期刊文献+
共找到6,353篇文章
< 1 2 250 >
每页显示 20 50 100
Research on the Four Collaborative Innovation Mechanisms of Industry-education Integration Based on the Concept of Community
1
作者 Yanwei Wang Yuhan Jiang +3 位作者 Shuxue Tian Yu Zheng Shihang Zhou Huilin Huang 《教育技术与创新》 2023年第4期20-33,共14页
The concept of community is of great significance in guiding the innovation of the mechanism of industry-education integration,which can promote the integration of industry-education integration from"integration&... The concept of community is of great significance in guiding the innovation of the mechanism of industry-education integration,which can promote the integration of industry-education integration from"integration"to real"integration".We summarize the current situation of the development of industry-teaching integration mode through research,point out the"four deviations"in the development of industry-teaching integration,analyze the causes of deviations,and put forward the research strategy of"four synergistic"innovation mechanism for industry-teaching integration based on the concept of community,i.e.,synergistic development of community planning It proposes the research strategy of"four synergies"innovation mechanism based on the concept of community,namely the synergy of community planning and development,the synergy of community governance concept,the synergy of community multi-party educating mechanism,and the synergy of community fusion effect system,so as to establish collaborative ties,build a new form of cooperation concepts,safeguard the docking of talent supply and demand,and enhance the effect of integration of industry and education. 展开更多
关键词 community concept integration of industry-education collaborative development INNOVATION
下载PDF
Exploration of the Construction and Path Selection of the Deep Integration Model of Industry-Education in Universities
2
作者 Yufei Zhang Chang Yu 《Journal of Contemporary Educational Research》 2024年第3期187-192,共6页
Against the backdrop of continuous development in the field of education,universities are encouraged to innovate their talent cultivation systems and objectives.The deep integration of industry and education has emerg... Against the backdrop of continuous development in the field of education,universities are encouraged to innovate their talent cultivation systems and objectives.The deep integration of industry and education has emerged as an effective strategy,aligning with the basic requirements of the new engineering education initiative and exerting a positive impact on socioeconomic development.However,an analysis of the current state of industry-education integration in universities reveals several issues that require optimization,affecting the ultimate effectiveness of integration.To optimize this phenomenon and achieve high-quality development,universities need to further explore the construction of a deep integration model of industry and education,adhering to corresponding principles to form a comprehensive system.On this basis,pathways for deep industry-education integration can be summarized. 展开更多
关键词 UNIVERSITIES industry-education integration Deep integration Construction model PATHWAYS
下载PDF
The Impact of Industry-Education Integration on College Students’ Motivation to Learn English under the TPACK Framework
3
作者 Xiaochao Yao 《Journal of Contemporary Educational Research》 2024年第8期181-187,共7页
This paper explores the impact of industry-education integration on students’motivation in college English courses under the TPACK(Technological Pedagogical Content Knowledge)framework using a comprehensive approach ... This paper explores the impact of industry-education integration on students’motivation in college English courses under the TPACK(Technological Pedagogical Content Knowledge)framework using a comprehensive approach combining quantitative and qualitative methods.Quantitative data analysis indicates a significant positive correlation between the perception of industry-education integration and the level of student learning motivation.There is also a clear association between the perception scores of TPACK framework integration and learning motivation.Qualitative data analysis reveals students’positive experiences and recognition of the TPACK framework integration in practical application projects.The study concludes that industry-education integration and the TPACK framework play a crucial role in enhancing students’learning motivation.It suggests optimizing teaching practices through faculty training,designing practical application projects,and promoting student interaction.This comprehensive analysis provides substantial guidance for the future development of English courses. 展开更多
关键词 industry-education integration TPACK framework Learning motivation English learning
下载PDF
Research on the Generation of Professional Skill Modules for Talent Cultivation in the Landscape Architecture Profession for Industry-Education Integration of Small and Medium-Sized Enterprises
4
作者 Fengyi Xu Yang Su 《Journal of Contemporary Educational Research》 2024年第6期227-232,共6页
Due to industry characteristics or regional limitations,many students in certain majors tend to seek employment in small and medium-sized enterprises(SMEs).SMEs face certain challenges in implementing industry-educati... Due to industry characteristics or regional limitations,many students in certain majors tend to seek employment in small and medium-sized enterprises(SMEs).SMEs face certain challenges in implementing industry-education integration,and there is a lack of mature methods in specific implementation processes and talent cultivation plan generation.Taking the landscape architecture profession as an example,this paper conducts a correlation analysis and cross-analysis of the industry-required professional skills based on surveys of over 300 industry practitioners employed in SMEs.It provides professional skill cultivation modules based on market feedback.This research process and analysis method have certain reference significance for the rapid production of adaptive talent cultivation professional skill modules in other industries targeting SMEs. 展开更多
关键词 Landscape architecture profession Talent cultivation industry-education integration Small and medium-sized enterprises
下载PDF
Discussion on the Talent Cultivation Strategy for Interior Design in Vocational Colleges from the Perspective of Industry-Education Integration
5
作者 Jingqiu Guo Qing He Jin Zeng 《Journal of Contemporary Educational Research》 2024年第10期192-198,共7页
To further enhance the effectiveness of talent cultivation for interior design in vocational colleges,it is necessary to vigorously promote the construction of an industry-education integration model.Through this mode... To further enhance the effectiveness of talent cultivation for interior design in vocational colleges,it is necessary to vigorously promote the construction of an industry-education integration model.Through this model,the roles of both enterprises and schools can be leveraged to jointly facilitate the continuous improvement of students’professional abilities and practical skills,providing a steady stream of high-quality talents for the development of the interior design field.Therefore,this paper analyzes the current issues in interior design talent cultivation in vocational colleges from the perspective of industry-education integration and proposes corresponding improvement measures. 展开更多
关键词 industry-education integration Interior design in vocational colleges Talent cultivation
下载PDF
Research on the Deep Integration Mechanism of National Fitness Campaign and College Physical Education Teaching:Taking Guangdong University of Science and Technology as an Example
6
作者 Junmei Cui Yanqing Yan 《Journal of Contemporary Educational Research》 2024年第1期107-115,共9页
By using the methods of literature review,questionnaire survey,and expert interview,this paper discusses and analyzes the deep integration mechanism of national fitness campaign and college physical education teaching... By using the methods of literature review,questionnaire survey,and expert interview,this paper discusses and analyzes the deep integration mechanism of national fitness campaign and college physical education teaching,in order to promote the development of college physical education teaching reform,expand ideas,explore new fields,and provide novel development directions.The purpose is to enhance the national physical quality,improve the public service system,enhance the health awareness of the citizens,and provide guidelines for promoting the development of sports. 展开更多
关键词 National fitness campaign College physical education Deep integration mechanism
下载PDF
Discussion on Construction and Mechanism of Practice Bases for Professional Degree Postgraduates Based on the Integration of Production and Education in Local Universities
7
作者 Dabing XIANG Yu FAN +5 位作者 Xueling YE Changying LIU Liangzhen JIANG Yan WAN Yuehua WANG Yanxia SUN 《Agricultural Biotechnology》 CAS 2023年第5期75-77,87,共4页
Under the background of emerging agricultural education,practice bases are an important place to train profession talented person that match social needs,so it is very important to build stable and long-term practice ... Under the background of emerging agricultural education,practice bases are an important place to train profession talented person that match social needs,so it is very important to build stable and long-term practice bases.At present,the main problems in the construction of practice bases for postgraduates in local colleges and universities are mainly focusing on construction and neglecting management,imperfect cooperation mechanism and lack of teaching management effectively.It is of great significance to build a long-term management mechanism to ensure the education quality of practice bases.Therefore,constructing the mode of"double integration and double promotion of production and education"with practice bases as the carrier and realizing the organic combination of industrial needs and postgraduate projects is an important idea for local colleges and universities to train professional degree postgraduates to"know agriculture,love agriculture,strengthen agriculture and promote agriculture",and it also provides a reference for the mechanism construction of postgraduate bases. 展开更多
关键词 Emerging Agricultural Education Professional master integration of science and education Practice base mechanism
下载PDF
Research and Practice on the Construction of Municipal Industry-Education Consortium Based on the Integration of Industrial Chain,Innovation Chain,Talent Chain,and Education Chain
8
作者 Hui Li Xu-liang Duan Jia-xin Yue 《Journal of Contemporary Educational Research》 2023年第12期53-63,共11页
The construction of a municipal industry-education consortium is one of the important measures for the“one body,two wings,and five key points”reform of China’s modern vocational education system in the new era.It i... The construction of a municipal industry-education consortium is one of the important measures for the“one body,two wings,and five key points”reform of China’s modern vocational education system in the new era.It is of great significance for the integrated promotion of the three major national strategies of education,technology,and talent.Exploring the construction path of municipal industry-education consortia from the perspective of“four-chain integration”is essential for improving the quality of vocational education talents,comprehensively promoting local economic and social development,and serving the national strategy of revitalizing the country through science and education.The new generation of information technology industry-education consortium in Chengdu actively explores new paths of industry-education integration,science-education integration,and vocational-education integration.It has formed a“park+alliance”to establish a diversified collaborative construction and management mechanism,a“professional+industry”school-enterprise cooperation to promote industrial transformation and upgrading,a“teaching+research and development”to build an industry-university research innovation platform to empower high-quality development,and a“cultivation+employment”to explore a matrix style talent cultivation model,thus promoting regional governments,industries enterprises,and higher education institutions.Fully leveraging complementary advantages involves capitalizing on the spatial cluster effect.It requires a foundation in the education chain,guided by the industrial chain,activation of the innovation chain,establishment of a talent chain,enhancement of the value chain,and the promotion of a modern vocational education structure.This structure should align with market demand and industry structure,ultimately promoting regional economic and social development. 展开更多
关键词 Four-chain integration Municipal industry-education consortium integration of industry and education Vocational colleges
下载PDF
Failure mechanism and influencing factors of cement sheath integrity under alternating pressure 被引量:1
9
作者 Kuan-Hai Deng Nian-Tao Zhou +4 位作者 Yuan-Hua Lin Yan-Xian Wu Jie Chen Chang Shu Peng-Fei Xie 《Petroleum Science》 SCIE EI CAS CSCD 2023年第4期2413-2427,共15页
The failure of cement sheath integrity can be easily caused by alternating pressure during large-scale multistage hydraulic fracturing in shale-gas well.An elastic-plastic mechanical model of casing-cement sheath-form... The failure of cement sheath integrity can be easily caused by alternating pressure during large-scale multistage hydraulic fracturing in shale-gas well.An elastic-plastic mechanical model of casing-cement sheath-formation(CSF)system under alternating pressure is established based on the Mohr-Coulomb criterion and thick-walled cylinder theory,and it has been solved by MATLAB programming combining global optimization algorithm with Global Search.The failure mechanism of cement sheath integrity is investigated,by which it can be seen that the formation of interface debonding is mainly related to the plastic strain accumulation,and there is a risk of interface debonding under alternating pressure,once the cement sheath enters plasticity whether in shallow or deep well sections.The matching relationship between the mechanical parameters(elastic modulus and Poisson's ratio)of cement sheath and its integrity failure under alternating pressure in whole well sections is studied,by which it has been found there is a“critical range”in the Poisson's ratio of cement sheath.When the Poisson's ratio is below the“critical range”,there is a positive correlation between the yield internal pressure of cement sheath(SYP)and its elastic modulus.However,when the Poisson's ratio is above the“critical range”,there is a negative correlation.The elastic modulus of cement sheath is closely related to its Poisson's ratio,and restricts each other.Scientific and reasonable matching between mechanical parameters of cement sheath and CSF system under different working conditions can not only reduce the cost,but also protect the cement sheath integrity. 展开更多
关键词 Casing-cement sheath-formation system mechanical model Matching relationship Cement sheath integrity Critical range mechanical parameters
下载PDF
The Application of Semantic Cognitive Mechanism of English Idioms in Idiom Teaching
10
作者 Haiying Zhan 《Journal of Contemporary Educational Research》 2024年第9期237-242,共6页
This article takes the perspective of cognitive linguistics and applies the semantic cognitive mechanism of English idioms to analyze the motivation between the generation and meaning of idioms.It explores the teachin... This article takes the perspective of cognitive linguistics and applies the semantic cognitive mechanism of English idioms to analyze the motivation between the generation and meaning of idioms.It explores the teaching of English idioms based on motivation analysis and proposes several suggestions and strategies for idiom teaching,hoping to benefit English idiom teaching. 展开更多
关键词 Semantic cognitive mechanism METAPHOR METONYMY Conceptual integration Idiom teaching
下载PDF
Research on Mechanism and Promotion Path of Culture and Tourism Industry Integration in Tai'an City
11
作者 DONG Hongxia WANG Hui 《Journal of Landscape Research》 2021年第6期63-66,70,共5页
Based on in-depth analysis of dynamic mechanism of industry integration under the background of industry integration,as well as current situation and existing problems of integrated development of culture and tourism ... Based on in-depth analysis of dynamic mechanism of industry integration under the background of industry integration,as well as current situation and existing problems of integrated development of culture and tourism industry in Tai’an City,the paper puts forward the selection path and policy guarantee for the integrated development of culture and tourism industry in Tai’an City following the theory of industry integration and dynamic mechanism,which is of important policy guiding significance for promoting the coordinated development of culture and tourism industry in Tai’an City. 展开更多
关键词 Culture and tourism industry Industry integration mechanism PATH
下载PDF
Research on the Talent Training Mode of Early Education Specialty Under the Background of Industry-Education Integration
12
作者 Lingyu Bao 《Journal of Contemporary Educational Research》 2022年第2期98-102,共5页
With the continuous progress of the society and the rapid development of the industry,the talent training mode of early education has become an important commodity of education reform.Under the background of the integ... With the continuous progress of the society and the rapid development of the industry,the talent training mode of early education has become an important commodity of education reform.Under the background of the integration of industry and education,the training direction of early education professionals needs to be adjusted and planned.The practice of industry-education integration requires the deep combination of early education specialty with early education institutions and the technical standards of the equivalent industry,so as to build a high-quality platform for the growth of early education professionals.This paper focuses on the current situation of the integration of industry and education,and then makes an in-depth analysis on several reform strategies,so as to lay a solid foundation for the training of early education talents. 展开更多
关键词 industry-education integration Early education specialty Talent training mode Reform strategies
下载PDF
Research on Application-oriented Undergraduate Course Construction under the Background of Industry-education Integration——Take the Performance Management Course as an Example
13
作者 Miaomiao Ma Xia Mu 《教育研究前沿(中英文版)》 2022年第1期53-57,共5页
Deepening the integration of industry and education is an effective way to cultivate high-quality applied talents.However,integration of industry and education is still at a relatively low level,and the mode is relati... Deepening the integration of industry and education is an effective way to cultivate high-quality applied talents.However,integration of industry and education is still at a relatively low level,and the mode is relatively single,without realizing the deep integration of collaborative education and industry.This paper takes the course"Performance Management"of Human Resource Management as an example to build an industry-education integration system with curriculum construction as a carrier.We introduce enterprise tutors and enterprise scenarios from the aspects of teaching syllabus,teaching content,teaching design,teaching process,teaching resources,and teaching evaluation to study the construction of professional courses under the background of industry-education integration.Through the Performance Management course study,we summarize the methods and modes of industry-education integration in human resource management(HRM)courses and extend and apply the research results to other courses of HRM majors to complete the construction of courses aiming at industry-education integration in HRM majors. 展开更多
关键词 industry-education integration Applied Bachelor's Degree Curriculum System "Performance Management"Course
下载PDF
Study on the Mechanism of the Integration of Urban and Rural Development from the View of Elements Flow
14
作者 Chang Ye Jin Tianlin 《学术界》 CSSCI 北大核心 2016年第6期285-290,共6页
Fromthe enterprise,individual and government,which are the three main economic behavior subject,this paper analysis factors impact of flow behavior main body and the change of the objective function,constraint functio... Fromthe enterprise,individual and government,which are the three main economic behavior subject,this paper analysis factors impact of flow behavior main body and the change of the objective function,constraint function and the impact of the change of behavior equation,and then summarizes their effects on the integration of urban and rural development,to build fromexogenous shocks to the endogenous to adapt to the economic decision-making framework,clarify elements flow affect the running mechanismof the urban-rural integration. 展开更多
关键词 城乡一体化发展 流动行为 运行机制 经济决策 行为主体 目标函数 约束函数 城乡发展
下载PDF
Proportion Integration Differentiation(PID)Control Strategy of Belt Sander Based on Fuzzy Algorithm
15
作者 陈坤 张亚伟 +1 位作者 张振 桂志伟 《Journal of Donghua University(English Edition)》 CAS 2023年第2期177-184,共8页
Aiming at solving the problems of response lag and lack of precision and stability in constant grinding force control of industrial robot belts,a constant force control strategy combining fuzzy control and proportion ... Aiming at solving the problems of response lag and lack of precision and stability in constant grinding force control of industrial robot belts,a constant force control strategy combining fuzzy control and proportion integration differentiation(PID)was proposed by analyzing the signal transmission process and the dynamic characteristics of the grinding mechanism.The simulation results showed that compared with the classical PID control strategy,the system adjustment time was shortened by 98.7%,the overshoot was reduced by 5.1%,and the control error was 0.2%-0.5%when the system was stabilized.The optimized fuzzy control system had fast adjustment speeds,precise force control and stability.The experimental analysis of the surface morphology of the machined blade was carried out by the industrial robot abrasive grinding mechanism,and the correctness of the theoretical analysis and the effectiveness of the control strategy were verified. 展开更多
关键词 grinding mechanism constant force control strategy fuzzy control proportion integration differentiation(PID)
下载PDF
Study on a Bowl-based Mechanism for Transplanting Potted Strawberry Seedlings
16
作者 Yin Da-qing Yang Yu-chao +2 位作者 Zhou Mai-le Wei Ming-xu Wang Jin-wu 《Journal of Northeast Agricultural University(English Edition)》 CAS 2023年第1期56-68,共13页
To improve the efficiency of fetching and transplanting seedlings for the mechanization of strawberry planting,an integrated transplanting mechanism was designed with protruding,fetching and planting performance to ac... To improve the efficiency of fetching and transplanting seedlings for the mechanization of strawberry planting,an integrated transplanting mechanism was designed with protruding,fetching and planting performance to achieve rapid fetching and pushing bowl movements.According to the working principle of the slewing mechanism,a kinematics model and the optimization goal were established,respectively.Based on visual auxiliary analysis software,optimal parameters were obtained.A three-dimensional model was established to obtain a simulation trajectory by means of a virtual simulation design analysis.Three-dimensional printing technology was used to manufacture the test prototype,and the actual working trajectories of the test prototype were extracted using high-speed photography technology,which verified the consistency of the actual trajectory with the theoretical and simulated trajectories.A prototype transplanting experiment was performed with the success rate of seedling extraction of 91.2%and excellent planting rate of 82.8%,which met the requirements for integrated strawberry harvesting,planting and transplanting.The experimental results verified the correctness and feasibility of the design of integrated transplanting mechanism. 展开更多
关键词 potted strawberry seedlings potted seedling transplanting integrated planting mechanism protruding and pushing bowl type parameter optimization
下载PDF
A Survey of Mathematical Tools in Topology and Performance Integrated Modeling and Design of Robotic Mechanism 被引量:1
17
作者 Xinming Huo Shuofei Yang +2 位作者 Binbin Lian Tao Sun Yimin Song 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2020年第4期30-44,共15页
Topology and performance are the two main topics dealt in the development of robotic mechanisms.However,it is still a challenge to connect them by integrating the modeling and design process of both parts in a unified... Topology and performance are the two main topics dealt in the development of robotic mechanisms.However,it is still a challenge to connect them by integrating the modeling and design process of both parts in a unified frame.As the properties associated with topology and performance,finite motion and instantaneous motion of the robot play key roles in the procedure.On the purpose of providing a fundamental preparation for integrated modeling and design,this paper carries out a review on the existing unified mathematic frameworks for motion description and computation,involving matrix Lie group and Lie algebra,dual quaternion and pure dual quaternion,finite screw and instantaneous screw.Besides the application in robotics,the review of the work from these mathematicians concentrates on the description,composition and intersection operations of the finite and instantaneous motions,especially on the exponential-differential maps which connect the two sides.Furthermore,an in-depth discussion is worked out by investigating the algebraical relationship among these methods and their further progress in integrated robotic development.The presented review offers insightful investigation to the motion description and computation,and therefore would help designers to choose appropriate mathematical tool in the integrated design and modeling and design of mechanisms and robots. 展开更多
关键词 Robotic mechanism integrated method Matrix Lie group Dual quaternion Finite screw
下载PDF
Research on Operation Optimization of Energy Storage Power Station and Integrated Energy Microgrid Alliance Based on Stackelberg Game
18
作者 Yu Zhang Lianmin Li +1 位作者 Zhongxiang Liu Yuhu Wu 《Energy Engineering》 EI 2024年第5期1209-1221,共13页
With the development of renewable energy technologies such as photovoltaics and wind power,it has become a research hotspot to improve the consumption rate of new energy and reduce energy costs through the deployment ... With the development of renewable energy technologies such as photovoltaics and wind power,it has become a research hotspot to improve the consumption rate of new energy and reduce energy costs through the deployment of energy storage.To solve the problem of the interests of different subjects in the operation of the energy storage power stations(ESS)and the integrated energy multi-microgrid alliance(IEMA),this paper proposes the optimization operation method of the energy storage power station and the IEMA based on the Stackelberg game.In the upper layer,ESS optimizes charging and discharging decisions through a dynamic pricing mechanism.In the lower layer,IEMA optimizes the output of various energy conversion coupled devices within the IEMA,as well as energy interaction and demand response(DR),based on the energy interaction prices provided by ESS.The results demonstrate that the optimization strategy proposed in this paper not only effectively balances the benefits of the IEMA and ESS but also enhances energy consumption rates and reduces IEMA energy costs. 展开更多
关键词 Energy storage station dynamic pricing mechanism stackelberg game integrated energy multi-microgrid alliance demand response
下载PDF
Integrating Automatic Patch Snatching System by the Concept of Generalized Mechanisms
19
作者 裘建新 林兰天 沈逸平 《Journal of Donghua University(English Edition)》 EI CAS 2008年第2期235-240,共6页
An automatic patch snatching system is described which has three machine cells including dividing equipment, tackling equipment and patch removing equipment. The electromechanical integration design of in-piece tackli... An automatic patch snatching system is described which has three machine cells including dividing equipment, tackling equipment and patch removing equipment. The electromechanical integration design of in-piece tackling system based on the concept of generalized mechanisms is introduced. The design of the dividing equipment, the design of micro-feeding machine equipped with micro-level pressure sensor, and the realizing of computer path for patch snatching are investigated. 展开更多
关键词 PATCH snatching generalized mechanisms electromechanical integration design
下载PDF
Research on the mechanism of Chaihu Huangqin medicine based on integrated pharmacology to improve the clinical symptoms of COVID-19
20
作者 Huan-Le Fang Bei-Bei Bie +2 位作者 Ying Mu Rong-Li Liu Yan-Bin Chen 《Journal of Hainan Medical University》 2020年第12期15-19,共5页
Objective:Novel coronavirus(COVID-19)was used to improve the clinical symptoms of the new type coronavirus(LV),based on integrated pharmacology.Methods:TCMIP v2.0 was used to predict the key target and action pathway ... Objective:Novel coronavirus(COVID-19)was used to improve the clinical symptoms of the new type coronavirus(LV),based on integrated pharmacology.Methods:TCMIP v2.0 was used to predict the key target and action pathway of Bupleurum baicalensis Georgi in improving the clinical symptoms of covid-19.The multi-dimensional network diagram of"drug pair active component key target action pathway"was drawn to explore its action mechanism from the molecular level.Results:Bupleurum and Scutellaria baicalensis could regulate IL signaling pathway and clec7a(a member of C-type lectin domain 7 family)/Inflammatory pathway,immune stress and other related signaling pathways can inhibit activated cytokines,alleviate excessive immune response,eliminate inflammation,and resist virus.In addition,the core targets of Bupleurum baicalensis baicalensis Georgi:nuclear factor kB(NFKB2,NFKB1),interleukin(IL-6,IL-1B),toll like receptor 4(TLR4),tumor necrosis factor(TNF)and so on are mostly induced by inflammation It is related to body damage.Bupleurum and scutellaria have the clinical effects of anti-inflammatory,antiviral,strengthening immunity,inhibiting pulmonary fibrosis and so on.Conclusion:Radix Bupleuri Scutellariae can be used to treat covid-19 by multi-channel,multi-target and multi ring.The results of this study provide a theoretical basis for Bupleurum Scutellaria to improve the use of COVID-19. 展开更多
关键词 integrated pharmacology Chaihu Scutellaria COVID-19 mechanism of action
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部