为系统梳理生物炭对土壤微生物活动、群落等方面影响的研究进展和未来发展趋势,以2007-2020年Web of Science核心合集数据库中针对生物炭调控土壤微生物的文献为样本,采用文献计量学软件CiteSpace对文献的年发文量、研究力量和研究热点...为系统梳理生物炭对土壤微生物活动、群落等方面影响的研究进展和未来发展趋势,以2007-2020年Web of Science核心合集数据库中针对生物炭调控土壤微生物的文献为样本,采用文献计量学软件CiteSpace对文献的年发文量、研究力量和研究热点进行了可视化分析。从论文数量和质量来看,近年来以生物炭为主题对土壤微生物研究的发文数量呈现急剧增长趋势,发文数量最多的国家是中国和美国。文献排名TOP 10的科研机构有中国科学院、浙江大学和康奈尔大学等,作者分析显示科研团队之间存在深入的学术交流。基于关键词聚类分析和突现词分析,研究主题热点集中在不同材质、温度等条件制备的生物炭对土壤微生物群落结构、细菌和古菌的影响。该领域未来应更加注重生物炭改变土壤微生物的内在机理研究,提高生物炭和土壤微生物的联合作用关注度。展开更多
土壤深层碳库巨大,在全球碳循环中具有重要作用。为了深入理解深层土壤碳循环,分析深层土壤为主题的全球土壤碳循环研究的热点与前沿,以Web of Science核心合集为数据库,获取近25年以深层土壤为主题词的土壤碳循环研究文献(280篇)。通...土壤深层碳库巨大,在全球碳循环中具有重要作用。为了深入理解深层土壤碳循环,分析深层土壤为主题的全球土壤碳循环研究的热点与前沿,以Web of Science核心合集为数据库,获取近25年以深层土壤为主题词的土壤碳循环研究文献(280篇)。通过文献计量方法,分别对年文献发表量、研究区分布、研究主题热点等进行了统计与可视化分析。结果表明:(1)1995-2020年间,以深层土壤为主题词对土壤碳循环研究的发文数量逐渐增长,尤其是2010-2020年期间;(2)不同研究主题对深层土壤的定义不同,其中以土壤碳储量为主题的研究对深层土壤的定义深度最深,52.2%的文献对深层土壤定义深度超过60 cm;(3)农林、环境科学、土壤科学和生态学是深层土壤碳循环研究的主要领域;(4)研究热点主要集中在环境因素和土地利用变化对土壤碳储量、碳稳定性及碳剖面垂直变化的影响方面;(5)近几年,研究主题逐渐向微生物群落、激发效应、碳组分、碳稳定性等转变,研究对象扩展到了北极永久冻土。展开更多
The Zhujiang River （Pearl River） Estuary （ZRE） is a very complicated and large-scale estuarine system in China. It consists of two parts： the river networks and the estuarine bays. Not only is the network system ...The Zhujiang River （Pearl River） Estuary （ZRE） is a very complicated and large-scale estuarine system in China. It consists of two parts： the river networks and the estuarine bays. Not only is the network system one of the most complicated in the world, but also each estuarine bay has a very special morphodynamic feature due to the geological settings. Morphological boundary conditions have direct effects on the energy dissipa- tion and balance. On the basis of a three-dimensional （3-D） barotropic model whose domain includes the river networks and the estuarine bays, the energy budget is discussed under the influence of topography in the ZRE. The elevation and discharge of this model are validated by the observations collected in July 1999 and February 2001. The results show that （1） the source of energy in the ZRE is mainly generated by tides and river runoffs, which have an obvious seasonal change, and （2） there are some typical hotspots where the energy dissipation is 1-2 orders higher than those in the immediate upstream and downstream sections in the ZRE. These hotspots are linked with the small-scale dynamic structures （SSDS） and morphological units. On the basis of the characteristics of the morphology and the energy dissipation, the hotspots can be catego- rized into three types： the outlet of the ZRE, the meandering river, the branch and junction.展开更多
目的探讨适应性支持通气(adaptive support ventilation,ASV)在全麻苏醒期患者中的应用效果。方法采用便利抽样法选取全麻手术后带气管导管转入PACU观察的患者120例,采用随机数字表法分为对照组和试验组(每组60例)。对照组采用容量控制...目的探讨适应性支持通气(adaptive support ventilation,ASV)在全麻苏醒期患者中的应用效果。方法采用便利抽样法选取全麻手术后带气管导管转入PACU观察的患者120例,采用随机数字表法分为对照组和试验组(每组60例)。对照组采用容量控制同步间歇指令通气(volume control‑synchronized intermittent mandatory ventilation,VC‑SIMV),试验组采用ASV,比较两组拔管前人机对抗发生率、苏醒期间镇静药物使用率、手动更改呼吸机参数的比例、PACU苏醒时间和拔管后低氧血症发生率。结果试验组拔管前人机对抗发生率、苏醒期间镇静药物使用率、手动更改呼吸机参数的比例均低于对照组(P<0.05),PACU苏醒时间少于对照组(P<0.05);两组低氧血症发生率差异无统计学意义(P>0.05)。结论相比于传统的VC‑SIMV模式,ASV应用于全麻带气管导管转入PACU苏醒的患者,能提供更好的人机协调性、简化通气管理、缩短患者苏醒时间。展开更多
南极地区独特的地理位置和自然环境条件使其成为世界各国开展各类科研活动的热点区域。本文采用文献计量学可视化方法,以Web of Science数据库核心合集为数据源,分析了2000—2020年南极科学研究的中外发展态势和进程,明晰了近20年南极...南极地区独特的地理位置和自然环境条件使其成为世界各国开展各类科研活动的热点区域。本文采用文献计量学可视化方法,以Web of Science数据库核心合集为数据源,分析了2000—2020年南极科学研究的中外发展态势和进程,明晰了近20年南极科学研究的热点及前沿研究领域,并对比分析了中国与美国等西方发达国家在南极开展科学研究的现状,进而为推动中国南极科学研究提供支撑。结果表明:①国际南极科学研究在地球科学(综合)、生态学和海洋学等学科领域发文量较高,而环境科学在南极研究的受关注程度呈不断提高态势;②美国在南极领域的发文量最多,远超其他国家。中国在南极科学研究中与美国、澳大利亚、英国、德国和法国等国家合作密切;③近年国际南极研究的热点问题主要包括南大洋生物资源和碳循环,南极气候变化和海冰异常过程,南极地质演化和古环境,南极微生物资源开发以及南大洋水团及其动力学等;冰盖质量平衡、乔治王岛、生物地理学和生物多样性等研究领域是近年南极科学研究的前沿领域。④中国在南极的科学研究相对侧重环境科学、微生物学和食品科技等领域,而在地球化学与地球物理、生态学和自然地理等领域落后于西方发达国家。未来中国要加强与南极科考强国之间的合作,在学科交叉、边缘部分寻求突破,力争在重要科技领域成为领跑者,在新兴前沿交叉领域成为开拓者。展开更多
We analyzed the sedimentary characteristics and chronostratigraphy of the Pearl River Delta in South China, and discussed the Holocene stratigraphic characteristics and the filling process since the Holocene, based on...We analyzed the sedimentary characteristics and chronostratigraphy of the Pearl River Delta in South China, and discussed the Holocene stratigraphic characteristics and the filling process since the Holocene, based on 90 boreholes. Our results showed that the maximum transgressive surface of the Pearl River Delta was located in the soft marine silt horizons, whereas it was shown as an erosion surface in areas with tidal scour. From bottom to top, Holocene sedimentary sequences were fluvial facies, floodplain-estuary facies, and estuary-delta facies in the paleo-valley, while the paleo-interfluve sequences were described as littoral facies, estuary facies, and delta facies. Vertical accumulation sequences of Holocene sediments were shown primarily as positive tapering-shaped sequences with no typical foreset, topset, or other sedimentary sequences of the Gilbert Delta. The paleo-Pearl River estuary had different evolution models in the highstand systems tract (HST) compared with other large deltas worldwide, in that it is dominated by a unique and complex geomorphologic boundary, and that it is a multi-sourced delta compounded by the independent and parallel development of fluvial sedimentary bodies with different scales. A huge estuary was formed in the present Pearl River Delta area when the post-glacial transgression reached maximum at about 6 ka BP. The estuary was divided into two parts by obstruction of a series of islands, an upper part composed of the semi-enclosed inner paleo-bay connected to rivers and a lower part consisting of the outer paleo-bay connected to the ocean. Both of these areas were interlinked by only a few narrows, in which the fluvial sediments are accumulated primarily in the inner paleo-bay. During 6-2 ka BP, the sedimentation in various regions of the inner paleo-bay occurred simultaneously with independent development under the remodeling and transformation effect of complex boundaries on river and ocean dynamics. After 2 ka BP, the evolution of the delta is no longer a simple natural process, but rather a common remodeling process accomplished by nature and humans.展开更多
文摘为系统梳理生物炭对土壤微生物活动、群落等方面影响的研究进展和未来发展趋势,以2007-2020年Web of Science核心合集数据库中针对生物炭调控土壤微生物的文献为样本,采用文献计量学软件CiteSpace对文献的年发文量、研究力量和研究热点进行了可视化分析。从论文数量和质量来看,近年来以生物炭为主题对土壤微生物研究的发文数量呈现急剧增长趋势,发文数量最多的国家是中国和美国。文献排名TOP 10的科研机构有中国科学院、浙江大学和康奈尔大学等,作者分析显示科研团队之间存在深入的学术交流。基于关键词聚类分析和突现词分析,研究主题热点集中在不同材质、温度等条件制备的生物炭对土壤微生物群落结构、细菌和古菌的影响。该领域未来应更加注重生物炭改变土壤微生物的内在机理研究,提高生物炭和土壤微生物的联合作用关注度。
文摘土壤深层碳库巨大,在全球碳循环中具有重要作用。为了深入理解深层土壤碳循环,分析深层土壤为主题的全球土壤碳循环研究的热点与前沿,以Web of Science核心合集为数据库,获取近25年以深层土壤为主题词的土壤碳循环研究文献(280篇)。通过文献计量方法,分别对年文献发表量、研究区分布、研究主题热点等进行了统计与可视化分析。结果表明:(1)1995-2020年间,以深层土壤为主题词对土壤碳循环研究的发文数量逐渐增长,尤其是2010-2020年期间;(2)不同研究主题对深层土壤的定义不同,其中以土壤碳储量为主题的研究对深层土壤的定义深度最深,52.2%的文献对深层土壤定义深度超过60 cm;(3)农林、环境科学、土壤科学和生态学是深层土壤碳循环研究的主要领域;(4)研究热点主要集中在环境因素和土地利用变化对土壤碳储量、碳稳定性及碳剖面垂直变化的影响方面;(5)近几年,研究主题逐渐向微生物群落、激发效应、碳组分、碳稳定性等转变,研究对象扩展到了北极永久冻土。
基金The National Basic Research and Development Program(973 program) of China under contract No.2013CB956502the National Natural Science Foundation of China under contract No.41006050the Open Research Foundation of Pearl River Hydraulic Research Institute of China under contract No.2013KJ07
文摘The Zhujiang River （Pearl River） Estuary （ZRE） is a very complicated and large-scale estuarine system in China. It consists of two parts： the river networks and the estuarine bays. Not only is the network system one of the most complicated in the world, but also each estuarine bay has a very special morphodynamic feature due to the geological settings. Morphological boundary conditions have direct effects on the energy dissipa- tion and balance. On the basis of a three-dimensional （3-D） barotropic model whose domain includes the river networks and the estuarine bays, the energy budget is discussed under the influence of topography in the ZRE. The elevation and discharge of this model are validated by the observations collected in July 1999 and February 2001. The results show that （1） the source of energy in the ZRE is mainly generated by tides and river runoffs, which have an obvious seasonal change, and （2） there are some typical hotspots where the energy dissipation is 1-2 orders higher than those in the immediate upstream and downstream sections in the ZRE. These hotspots are linked with the small-scale dynamic structures （SSDS） and morphological units. On the basis of the characteristics of the morphology and the energy dissipation, the hotspots can be catego- rized into three types： the outlet of the ZRE, the meandering river, the branch and junction.
文摘南极地区独特的地理位置和自然环境条件使其成为世界各国开展各类科研活动的热点区域。本文采用文献计量学可视化方法,以Web of Science数据库核心合集为数据源,分析了2000—2020年南极科学研究的中外发展态势和进程,明晰了近20年南极科学研究的热点及前沿研究领域,并对比分析了中国与美国等西方发达国家在南极开展科学研究的现状,进而为推动中国南极科学研究提供支撑。结果表明:①国际南极科学研究在地球科学(综合)、生态学和海洋学等学科领域发文量较高,而环境科学在南极研究的受关注程度呈不断提高态势;②美国在南极领域的发文量最多,远超其他国家。中国在南极科学研究中与美国、澳大利亚、英国、德国和法国等国家合作密切;③近年国际南极研究的热点问题主要包括南大洋生物资源和碳循环,南极气候变化和海冰异常过程,南极地质演化和古环境,南极微生物资源开发以及南大洋水团及其动力学等;冰盖质量平衡、乔治王岛、生物地理学和生物多样性等研究领域是近年南极科学研究的前沿领域。④中国在南极的科学研究相对侧重环境科学、微生物学和食品科技等领域,而在地球化学与地球物理、生态学和自然地理等领域落后于西方发达国家。未来中国要加强与南极科考强国之间的合作,在学科交叉、边缘部分寻求突破,力争在重要科技领域成为领跑者,在新兴前沿交叉领域成为开拓者。
文摘We analyzed the sedimentary characteristics and chronostratigraphy of the Pearl River Delta in South China, and discussed the Holocene stratigraphic characteristics and the filling process since the Holocene, based on 90 boreholes. Our results showed that the maximum transgressive surface of the Pearl River Delta was located in the soft marine silt horizons, whereas it was shown as an erosion surface in areas with tidal scour. From bottom to top, Holocene sedimentary sequences were fluvial facies, floodplain-estuary facies, and estuary-delta facies in the paleo-valley, while the paleo-interfluve sequences were described as littoral facies, estuary facies, and delta facies. Vertical accumulation sequences of Holocene sediments were shown primarily as positive tapering-shaped sequences with no typical foreset, topset, or other sedimentary sequences of the Gilbert Delta. The paleo-Pearl River estuary had different evolution models in the highstand systems tract (HST) compared with other large deltas worldwide, in that it is dominated by a unique and complex geomorphologic boundary, and that it is a multi-sourced delta compounded by the independent and parallel development of fluvial sedimentary bodies with different scales. A huge estuary was formed in the present Pearl River Delta area when the post-glacial transgression reached maximum at about 6 ka BP. The estuary was divided into two parts by obstruction of a series of islands, an upper part composed of the semi-enclosed inner paleo-bay connected to rivers and a lower part consisting of the outer paleo-bay connected to the ocean. Both of these areas were interlinked by only a few narrows, in which the fluvial sediments are accumulated primarily in the inner paleo-bay. During 6-2 ka BP, the sedimentation in various regions of the inner paleo-bay occurred simultaneously with independent development under the remodeling and transformation effect of complex boundaries on river and ocean dynamics. After 2 ka BP, the evolution of the delta is no longer a simple natural process, but rather a common remodeling process accomplished by nature and humans.
