期刊文献+
共找到235,205篇文章
< 1 2 250 >
每页显示 20 50 100
To Explore the Innovation of Mobile E-commerce Model in Service Industry From the Perspective of Supply Chain
1
作者 HAN Yalin Yu Li 《International English Education Research》 2017年第4期34-36,共3页
This paper analyzed the service supply chain of the domestic industry, tourist industry, information service industry in the mobile e-business environment, according to the function of different participators in suppl... This paper analyzed the service supply chain of the domestic industry, tourist industry, information service industry in the mobile e-business environment, according to the function of different participators in supply chain and their relationship between each other, this paper obtained different patterns of different industry in the mobile e-commerce environment. 展开更多
关键词 supply chain service industry mobile e-commerce model
下载PDF
New E-Commerce Model Based on Multi-Agent Automated Negotiation 被引量:2
2
作者 向传杰 贾云得 《Journal of Beijing Institute of Technology》 EI CAS 2003年第4期432-435,共4页
A new multi-agent automated negotiation model is developed and evaluated, in which two competitive agents, such as the buyer and seller, have firm deadlines and incomplete information about each other. The negotiation... A new multi-agent automated negotiation model is developed and evaluated, in which two competitive agents, such as the buyer and seller, have firm deadlines and incomplete information about each other. The negotiation is multi-dimensional in different cases. The model is discussed in 6 kinds of cases with different price strategies, warrantee strategies and time strategies. The model improves the model of Wooldridge and that of Sycara to a certain extent. In all possible situations, the optimal negotiation strategy is analyzed and presented, and an e-commerce model based on multi-agent automated negotiation model is also illustrated for the e-commerce application in the future. 展开更多
关键词 MULTI-AGENT automated negotiation e-commerce negotiation strategy
下载PDF
The Study of SINA.com as E-commerce Model
3
作者 刘玉玲 《海外英语》 2013年第17期281-285,共5页
E-commerce is playing an important role in our life. As E-commerce model, SINA is an online media company serv ing China and the global Chinese communities, which is worth studying. In the paper, the advantages of SIN... E-commerce is playing an important role in our life. As E-commerce model, SINA is an online media company serv ing China and the global Chinese communities, which is worth studying. In the paper, the advantages of SINA.com will be intro duced. After that, you can know the competition and strategy of SINA.com. Its future development is discussed at the end. 展开更多
关键词 SINA e-commerce COMPETITION PARTNERSHIP STRATEGY
下载PDF
Study on the Cooperative E-commerce Model between Enterprises based on the Value Chain
4
作者 XU Jun LIU Xiaoxing 《International Journal of Technology Management》 2015年第8期151-153,共3页
The real e-commerce between enterprises is based on the internal departments of enterprises and the cooperative interaction between enterprise and its partners. In this paper, on the basis of the theory of value chain... The real e-commerce between enterprises is based on the internal departments of enterprises and the cooperative interaction between enterprise and its partners. In this paper, on the basis of the theory of value chain, 11 cooperative e-commerce models between enterprises have been classified according to the activities of the cooperation between enterprises, and then every cooperative e-commerce model between enterprises is discussed. In practice, cooperative e-commerce between enterprises can be a combination of one or more e-commerce models between enterprises. 展开更多
关键词 e-commerce COOPERATIVE e-commerce COOPERATIVE modeL VALUE CHAIN
下载PDF
Study on the Problems in China's Free E-commerce Model
5
作者 Degang CHEN Yayun HUA 《International Journal of Technology Management》 2013年第6期1-3,共3页
There are a variety of e-commerce development modes. Free mode as one of the most important has been widely applied in e-commerce enterprises, and it has become one of the basic methods for ensuring e-commerce enterpr... There are a variety of e-commerce development modes. Free mode as one of the most important has been widely applied in e-commerce enterprises, and it has become one of the basic methods for ensuring e-commerce enterprises to seek a development. In this paper, the current development of the free mode is firstly analyzed and also the factors influencing users to make a choice are analyzed under the free business model, and then the problems in free e-commerce model are proposed, and finally related strategies and suggestions on how to develop for e-commerce enterprises under the free business model are provided. Keywords: 展开更多
关键词 e-commerce Free Business model Profit Making
下载PDF
The Revolution of Entrepreneurship Through E-Commerce Model:Questionnaire-based Research in China
6
作者 Juntao Li 《Journal of Electronic Research and Application》 2021年第5期11-19,共9页
E-commerce is evolving as an innovative tool in a wide range of areas,and has changed the face of entrepreneurship by making them more efficient and dynamic.In this paper,the author firstly reviewed the current develo... E-commerce is evolving as an innovative tool in a wide range of areas,and has changed the face of entrepreneurship by making them more efficient and dynamic.In this paper,the author firstly reviewed the current development of e-commerce and entrepreneurship,as well as existing opportunities and challenges in this field.This paper also combines both qualitative method(literature review)and quantitative method(questionnaire-based research)to explore the impact of e-commerce on the landscape of entrepreneurship.The findings of this study suggest that the development of e-commerce has triggered fundamental changes in entrepreneurial activities.It significantly promotes the entry of new start-ups and facilitates the growth of their businesses.Meanwhile,small-and medium-sized firms also encounter greater challenges when they try to adopt and implement e-commerce. 展开更多
关键词 e-commerce Entrepreneur ship Business strategies Literature review QUESTIONNAIRE
下载PDF
Predicting Purchasing Behavior on E-Commerce Platforms: A Regression Model Approach for Understanding User Features that Lead to Purchasing
7
作者 Abraham Jallah Balyemah Sonkarlay J. Y. Weamie +2 位作者 Jiang Bin Karmue Vasco Jarnda Felix Jwakdak Joshua 《International Journal of Communications, Network and System Sciences》 2024年第6期81-103,共23页
This research introduces a novel approach to improve and optimize the predictive capacity of consumer purchase behaviors on e-commerce platforms. This study presented an introduction to the fundamental concepts of the... This research introduces a novel approach to improve and optimize the predictive capacity of consumer purchase behaviors on e-commerce platforms. This study presented an introduction to the fundamental concepts of the logistic regression algorithm. In addition, it analyzed user data obtained from an e-commerce platform. The original data were preprocessed, and a consumer purchase prediction model was developed for the e-commerce platform using the logistic regression method. The comparison study used the classic random forest approach, further enhanced by including the K-fold cross-validation method. Evaluation of the accuracy of the model’s classification was conducted using performance indicators that included the accuracy rate, the precision rate, the recall rate, and the F1 score. A visual examination determined the significance of the findings. The findings suggest that employing the logistic regression algorithm to forecast customer purchase behaviors on e-commerce platforms can improve the efficacy of the approach and yield more accurate predictions. This study serves as a valuable resource for improving the precision of forecasting customers’ purchase behaviors on e-commerce platforms. It has significant practical implications for optimizing the operational efficiency of e-commerce platforms. 展开更多
关键词 e-commerce Platform Purchasing Behavior Prediction Logistic Regression Algorithm
下载PDF
Optimization and Innovation of the Operation Model of Mobile Social E-commerce under AI Empowerment:Taking the Female Community Platform“Little Red Book”as an Example
8
作者 Mi Liu Jia Yu +1 位作者 Yan Li Jun Zheng 《Proceedings of Business and Economic Studies》 2024年第4期269-274,共6页
This article takes the female community platform“Little Red Book”as an example to explore the optimization and innovation of mobile community e-commerce operation mode under Artificial Intelligence(AI)empowerment.Fi... This article takes the female community platform“Little Red Book”as an example to explore the optimization and innovation of mobile community e-commerce operation mode under Artificial Intelligence(AI)empowerment.Firstly,the relevant concepts were defined,and then the unique attributes of mobile community e-commerce were analyzed.As a typical representative of mobile community e-commerce,Little Red Book introduces the background and characteristics of its platform,analyzes its mobile community operation mode,and focuses on exploring how to establish a mobile community e-commerce platform and effective operation mode under the empowerment of AI technology,to provide some reference and inspiration for the development and operation of Little Red Book and other e-commerce platform enterprises. 展开更多
关键词 Mobile social e-commerce Little Red Book Female community platform AI User experience UGC
下载PDF
Impacts of agri-food e-commerce on traditional wholesale industry:Evidence from China
9
作者 Ruyi Yang Jifang Liu +2 位作者 Shanshan Cao Wei Sun Fantao Kong 《Journal of Integrative Agriculture》 SCIE CAS CSCD 2024年第4期1409-1428,共20页
Rapidly expanding studies investigate the effects of e-commerce on company operations in the retail market.However,the interaction between agri-food e-commerce(AEC)and the traditional agri-food wholesale industry(AWI)... Rapidly expanding studies investigate the effects of e-commerce on company operations in the retail market.However,the interaction between agri-food e-commerce(AEC)and the traditional agri-food wholesale industry(AWI)has not received enough attention in the existing literature.Based on the provincial panel data from 2013 to 2020 in China,this paper examines the effect of AEC on AWI,comprising three dimensions:digitalization(DIGITAL),agrifood e-commerce infrastructure and supporting services(AECI),and agri-food e-commerce economy(AECE).First,AWI and AEC are measured using an entropy-based combination of indicators.The results indicate that for China as a whole,AWI has remained practically unchanged,whereas AEC exhibits a significant rising trend.Second,the findings of the fixed-effect regression reveal that DIGITAL and AECE tend to raise AWI,whereas AECI negatively affects AWI.Third,threshold regression results indicate that AECI tends to diminish AWI with three-stage inhibitory intensity,which manifests as a first increase and then a drop in the inhibition degree.These results suggest that with the introduction of e-commerce for agricultural product circulation,digital development will have catfish effects that tend to stimulate the vitality of the conventional wholesale industry and promote technical progress.Furthermore,the traditional wholesale industry benefits financially from e-commerce even while it diverts part of the traditional wholesale circulation for agricultural products. 展开更多
关键词 agri-food e-commerce traditional wholesale industry panel threshold model dual-channel circulation
下载PDF
Impact of BRICS Trade Facilitation on China's Exports Using Cross-Border E-Commerce
10
作者 Longling LI Kaimei CHEN Zijian LONG 《Asian Agricultural Research》 2024年第5期1-7,共7页
With the rapid growth of the global digital economy, cross-border e-commerce, as an emerging form of trade, has gradually become a powerful engine to promote the development of global trade. BRICS is an important forc... With the rapid growth of the global digital economy, cross-border e-commerce, as an emerging form of trade, has gradually become a powerful engine to promote the development of global trade. BRICS is an important force in the global economy, and the progress of the BRICS countries' trade facilitation level has an important impact on the global trade environment. This paper conducts an in-depth study of the dynamic changes in BRICS trade facilitation from 2013 to 2022, and uses an extended gravity model to analyze the specific impact of this change on China's exports using cross-border e-commerce. The results show that although the BRICS countries have made some progress in trade facilitation, the overall level still needs to be improved, and there are obvious differences among member countries. However, the improvement of trade facilitation among BRICS countries has undoubtedly brought significant positive effects to China's exports using cross-border e-commerce. 展开更多
关键词 Trade facilitation BRICS Cross-border e-commerce Export trade
下载PDF
Research on Current Situation and Legal Regulation of Cosmetics Live Streaming E-commerce in China
11
作者 Jiang Ying 《China Detergent & Cosmetics》 CAS 2024年第1期63-70,共8页
Analyze the compatibility between cosmetics and live streaming e-commerce from its own nature,marketing means and supply chain characteristics.According to the prominent problems,sort out the relationship between all ... Analyze the compatibility between cosmetics and live streaming e-commerce from its own nature,marketing means and supply chain characteristics.According to the prominent problems,sort out the relationship between all parties in the cosmetics live e-commerce industry chain.Combined with the latest regulatory policies of live streaming e-commerce and cosmetics,the responsibilities of different subjects in cosmetics live streaming e-commerce are summarized,and relevant suggestions and countermeasures are put forward for the standardization and development of live streaming e-commerce.Cosmetics brand owners are the first responsible persons for product quality.Anchors,as a mixed identity between intermediary,advertising spokesperson and operator,should bear stricter joint and several liability when recommending products related to consumers’health.If anchors fail to clearly identify themselves in the recommendation process,thus causing consumers to mistake them for the operator of the cosmetics,they should assume the obligations of the operator. 展开更多
关键词 COSMETICS live streaming e-commerce legal relationship responsibilities of parties
下载PDF
How Does E-Commerce Policy Affect Consumption Disparities of Rural Households?-Evidence from China
12
作者 Zhang Cheng Weng Xiyan 《China Economist》 2024年第4期107-128,共22页
In the context of China’s ongoing efforts to promote countryside revitalization and facilitate domestic economic circulation,it is of great significance to reduce the consumption disparity among rural households and ... In the context of China’s ongoing efforts to promote countryside revitalization and facilitate domestic economic circulation,it is of great significance to reduce the consumption disparity among rural households and unleash the consumption potential in the countryside.Based on data from China Family Panel Studies,this paper adopts a staggered difference-in-differences method to assess the impact of the e-commerce to enter rural areas on the consumption disparity among rural households.Findings:the comprehensive demonstration work of promoting e-commerce to enter rural areas has reduced the consumption disparity among rural households through the following mechanisms.Firstly,this policy initiative has mitigated the consumption-inhibiting effect on rural household consumption due to the local market size and external market accessibility by promoting the distribution of consumer goods to villages.Secondly,this policy initiative has also increased the agricultural income of rural households and reduced their consumption disparity by distributing farm produce to cities and enhancing the agricultural income of rural households.Moreover,the work is characterized by inclusive growth and is not susceptible to the“elite capture”phenomenon. 展开更多
关键词 e-commerce to enter rural areas consumption disparity among rural household market accessibility market size income of rural households
下载PDF
The Impact of E-Commerce Live Broadcasts on Consumers’Purchase Intention
13
作者 Xingchao Bian Thanakon Ratchatakulpat Rattanavalee Maisak 《Proceedings of Business and Economic Studies》 2024年第4期263-268,共6页
E-commerce live broadcast has an important influence on consumers’purchase intention.The three dimensions of live broadcast content in the broadcast room are the number of comments,product quality,and live content as... E-commerce live broadcast has an important influence on consumers’purchase intention.The three dimensions of live broadcast content in the broadcast room are the number of comments,product quality,and live content as independent variables.A theoretical model is constructed with perceived value and risk as intermediaries and the consumers’purchase intention as the dependent variable,and corresponding hypotheses are put forward.We designed the scale,collected relevant data,and tested the model hypothesis using Statistical Package for Social Sciences(SPSS)and Analysis of Moment Structure(AMOS)software.The study found that the number of comments and product quality had a significant impact on perceived value,perceived risk,and consumers’purchase intention.From this conclusion,it is suggested that businesses should control the number of comments,strengthen the product quality of comments,and distinguish the repetition degree of the content of live broadcasts. 展开更多
关键词 Livestreaming e-commerce Perceived value Perceived risk Purchase intention
下载PDF
Research on Professional Teaching Reform of the E-Commerce Major in Vocational Colleges Under the Internet Era
14
作者 Yong Liang 《Journal of Contemporary Educational Research》 2024年第5期21-26,共6页
With the rapid development of science and technology,the face of human society has undergone great changes;with the emergence of the Internet era,all kinds of educational technology,equipment,and software in vocationa... With the rapid development of science and technology,the face of human society has undergone great changes;with the emergence of the Internet era,all kinds of educational technology,equipment,and software in vocational colleges have been widely used to carry out education and teaching,and has achieved remarkable results.Based on this,colleges and universities’electronic commerce(e-commerce)professional teachers should try to rely on the Internet to build information teaching classrooms,introduce advanced methods to build efficient classrooms by integrating teaching resources,and optimize the top-level design,so as to activate the classroom atmosphere,mobilize students’emotions,make them immersed in the teaching of electronic commerce courses.In view of this,this paper combines the existing theory and experience,first analyzes the dilemma faced by the current teaching of e-commerce in vocational colleges,then discusses the practical significance of teaching reform based on the Internet era,and lastly puts forward the specific practice path. 展开更多
关键词 INTERNET Vocational colleges e-commerce major Teaching reform
下载PDF
Analysis of the Current Situation, Influential Factors, and Countermeasures of Rural E-commerce Development
15
作者 Yi Wei Guizhen He 《Journal of Electronic Research and Application》 2024年第2期140-145,共6页
The development of rural e-commerce is becoming an important driver for the transformation of China’s rural economy,and with the rapid development of information technology and the upgrading of the agricultural indus... The development of rural e-commerce is becoming an important driver for the transformation of China’s rural economy,and with the rapid development of information technology and the upgrading of the agricultural industry,rural e-commerce is showing a vigorous momentum of development.Traditionally,agricultural products are mainly sold through traditional farmers’markets,which are subjected to geography and channel limitations,resulting in inefficient circulation of agricultural products.This paper analyzes the definition,the status quo,as well as the influencing factors of rural e-commerce development.On this basis,countermeasures for the advancement of rural e-commerce development are put forward. 展开更多
关键词 Rural e-commerce Influencing factors Industrial clusters RESPONSE
下载PDF
Enhanced E-commerce Fraud Prediction Based on a Convolutional Neural Network Model
16
作者 Sumin Xie Ling Liu +3 位作者 Guang Sun Bin Pan Lin Lang Peng Guo 《Computers, Materials & Continua》 SCIE EI 2023年第4期1107-1117,共11页
The rapidly escalating sophistication of e-commerce fraud in recent years has led to an increasing reliance on fraud detection methods based on machine learning.However,fraud detection methods based on conventional ma... The rapidly escalating sophistication of e-commerce fraud in recent years has led to an increasing reliance on fraud detection methods based on machine learning.However,fraud detection methods based on conventional machine learning approaches suffer from several problems,including an excessively high number of network parameters,which decreases the efficiency and increases the difficulty of training the network,while simultaneously leading to network overfitting.In addition,the sparsity of positive fraud incidents relative to the overwhelming proportion of negative incidents leads to detection failures in trained networks.The present work addresses these issues by proposing a convolutional neural network(CNN)framework for detecting ecommerce fraud,where network training is conducted using historical market transaction data.The number of network parameters reduces via the local perception field and weight sharing inherent in the CNN framework.In addition,this deep learning framework enables the use of an algorithmiclevel approach to address dataset imbalance by focusing the CNN model on minority data classes.The proposed CNN model is trained and tested using a large public e-commerce service dataset from 2018,and the test results demonstrate that the model provides higher fraud prediction accuracy than existing state-of-the-art methods. 展开更多
关键词 CNN model detection e-commerce FRAUD
下载PDF
Investigation and Countermeasures of the Development of Chinese Pharmaceutical E-commerce in the B2C Model Based on PEST-SWOT Analysis
17
作者 Xiu Yu Wang Shuling 《Asian Journal of Social Pharmacy》 2023年第4期398-405,共8页
Objective To analyze the problems of pharmaceutical e-commerce and provide strategies for its development in the future B2C mode since drug network management has great potential in China.Methods By collecting,identif... Objective To analyze the problems of pharmaceutical e-commerce and provide strategies for its development in the future B2C mode since drug network management has great potential in China.Methods By collecting,identifying,and conducting literature research,PEST-SWOT identification and positioning of pharmaceutical e-commerce in the B2C mode were carried out.Results and Conclusion A PEST-SWOT analysis matrix was established to analyze the status of B2C pharmaceutical e-commerce,and to summarize its advantages,disadvantages,opportunities and threats from four perspectives of politics,economy,society and technology.Suggestions on cultivating compound talents proficient in medicine and e-commerce,exploring online payment methods for medical insurance,integration of upstream and downstream of the industrial chain and data sharing are put forward to promote the healthy and long-term development of pharmaceutical e-commerce under the background of big data. 展开更多
关键词 pharmaceutical e-commerce B2C PEST-SWOT analysis matrix
下载PDF
A Study on the Countermeasures of Modern Agricultural Development from a Perspective of E-commerce——A Case of Suzhou,China 被引量:1
18
作者 SUN Xue-wen 《Asian Agricultural Research》 2010年第7期35-38,共4页
Based on the fact that e-commerce promotes the development of modern agriculture,the paper summarizes the present situation of agri-cultural e-commerce through related materials.Taking Suzhou city as an example,the pa... Based on the fact that e-commerce promotes the development of modern agriculture,the paper summarizes the present situation of agri-cultural e-commerce through related materials.Taking Suzhou city as an example,the paper analyzes the features of modern agriculture.And themodern agriculture is characterized with apparent industrialization and scaled requirements,the branded and particular agriculture has more advan-tages,leisure agriculture is the very special one.In order to upgrade the degree of agricultural industrialization of Suzhou,promote the communica-tion of agricultural information and sales of products and lower the risks of agricultural production,the e-commerce countermeasures of modern agri-culture have been put forward.Firstly,strengthen the network construction of agricultural information.Secondly,carry out the agricultural e-com-merce business by B2B model.Thirdly,construct the e-commerce platform of leisure agriculture.Fourthly,construct the e-commerce platform ofmodern agriculture.Fifthly,perfect the logistics distribution network of agricultural products of Suzhou.The last point is to accelerate the e-com-merce training of farmers and the introduction of talents. 展开更多
关键词 modern agriculture Agricultural e-commerce Agricultural e-commerce model e-commerce talents China
下载PDF
Spatial Structure of China's E-commerce Express Logistics Network Based on Space of Flows 被引量:2
19
作者 LI Yuanjun WU Qitao +2 位作者 ZHANG Yuling HUANG Guangqing ZHANG Hongou 《Chinese Geographical Science》 SCIE CSCD 2023年第1期36-50,共15页
The intermediate link compression characteristics of e-commerce express logistics ne tworks influence the tradition al mode of circulation of goods and economic organization,and alter the city spatial pattern.Based on... The intermediate link compression characteristics of e-commerce express logistics ne tworks influence the tradition al mode of circulation of goods and economic organization,and alter the city spatial pattern.Based on the theory of space of flows,this study adopts China Smart Logistics Network relational data to build China's e-commerce express logistics network and explore its spatial structure characteristics through social network analysis(SNA),the PageRank technique,and geospatial methods.The results are as follows:the network density is 0.9270,which is close to 1;hence,indicating that e-commerce express logistics lines between Chinese cities are nearly complete and they form a typical network structure,thereby eliminating fragmented spaces.Moreover,the average minimum number of edges is 1.1375,which indicates that the network has a small world effect and thus has a high flow efficiency of logistics elements.A significant hierarchical diffusion effect was observed in dominant flows with the highest edge weights.A diamond-structured network was formed with Shanghai,Guangzhou,Chongqing,and Beijing as the four core nodes.Other node cities with a large logistics scale and importance in the network are mainly located in the 19 city agglomerations of China,revealing the fact that the development of city agglomerations is essential for promoting the separation of experience space and changing the urban spatial pattern.This study enriches the theory of urban networks,reveals the flow laws of modern logistics elements,and encourages coordinated development of urban logistics. 展开更多
关键词 space of flows e-commerce express logistics urban logistics network logistics big data
下载PDF
基于主客观环流分型的强降水数值预报MODE检验方法及其在2019年暖季东北地区的应用
20
作者 齐铎 崔晓鹏 +4 位作者 陈力强 黄丽君 刘松涛 卜文惠 王承伟 《大气科学》 CSCD 北大核心 2024年第3期1113-1130,共18页
本文构建了基于主客观环流分型的强降水数值预报空间检验(MODE)方法框架,并利用该框架对欧洲中期天气预报中心全球模式(ECMWF)和中国气象局区域中尺度数值天气预报模式(CMA_MESO)的2019年暖季东北地区强降水预报进行检验。结果表明,201... 本文构建了基于主客观环流分型的强降水数值预报空间检验(MODE)方法框架,并利用该框架对欧洲中期天气预报中心全球模式(ECMWF)和中国气象局区域中尺度数值天气预报模式(CMA_MESO)的2019年暖季东北地区强降水预报进行检验。结果表明,2019年暖季东北地区54个强降水日的环流型可分为:西风槽型(15个)、副热带高压影响型(13个)、急流型(5个)、西部(12个)和东部冷涡型(9个)。其中,西风槽型和急流型以区域性强降水为主,模式对其强降水发生与否的预报能力强,TS评分较高;西部、东部冷涡型强降水的局地性强,模式对其强降水发生与否的预报能力差,TS评分低;副热带高压影响型也以区域性强降水为主,模式对其强降水发生与否的预报能力也比较强,但是对其强降水质心位置、强度、面积等属性预报偏差较大,TS评分也相对较低。另外,从两种模式预报性能对比看,CMA_MESO强降水强度和面积预报较实况普遍偏强,虽然其预报的TS评分一般高于ECMWF,但其对强降水预报的空报率也都比ECMWF大,对强降水的属性预报偏差一致性一般也低于ECMWF,其预报的可订正性整体上不及ECMWF。 展开更多
关键词 主客观融合环流分型 东北冷涡客观识别 强降水 数值预报 mode检验
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部