首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   122篇
  免费   10篇
  国内免费   30篇
测绘学   21篇
大气科学   7篇
地球物理   11篇
地质学   63篇
海洋学   12篇
综合类   19篇
自然地理   29篇
  2023年   1篇
  2022年   4篇
  2021年   4篇
  2020年   2篇
  2019年   2篇
  2018年   1篇
  2017年   3篇
  2016年   2篇
  2015年   6篇
  2014年   4篇
  2013年   7篇
  2012年   12篇
  2011年   10篇
  2010年   12篇
  2009年   10篇
  2008年   12篇
  2007年   9篇
  2006年   10篇
  2005年   13篇
  2004年   6篇
  2003年   2篇
  2002年   5篇
  2001年   6篇
  2000年   1篇
  1999年   5篇
  1998年   3篇
  1997年   1篇
  1996年   2篇
  1994年   1篇
  1993年   1篇
  1988年   2篇
  1986年   1篇
  1985年   1篇
  1977年   1篇
排序方式: 共有162条查询结果,搜索用时 16 毫秒
111.
ABSTRACT

We investigate possible changes in flood hazard over a 77-km2 area around the city of Ravenna. The subsidence rate in the area, naturally a few mm year?1, increased dramatically after World War II because of groundwater and natural gas extraction, exceeding 110?mm year?1 and resulting in cumulative drops larger than 1.5?m. The Montone–Ronco river system flows in the southern portion of the area, which is protected against frequent flooding by levees. We performed two-dimensional simulations of inundation events associated with levee breaching by considering four different terrain configurations: current topography and a reconstruction of ground elevations before anthropogenic land subsidence, both neglecting and representing the main linear infrastructures (e.g. roads, artificial channels). Results show that flood-hazard changes due to anthropogenic land subsidence (e.g. significant changes in computed water depth and velocity) are observed over less than 10% of the study area and are definitely less important than those resulting from construction of the linear infrastructures.  相似文献   
112.
地震泵抽吸作用与油气运聚成藏物理模拟   总被引:2,自引:0,他引:2  
地震泵抽吸作用是在断裂活动开启过程中,引发流体进入断裂带,并发生垂向运移的作用方式。在裂隙递进扩张形成优势裂隙并进一步发展成大的断裂面的演化过程中,地震泵抽吸作用发生,围岩中的流体在相对负压抽吸作用下进到断裂带中,之后主要在构造应力和异常高孔隙流体压力的共同作用下向上运移,并向着邻近断裂的封闭程度差、体积大、物性好的储层中充注运移,运移效率远远高于达西流和扩散流。断裂周期性破裂活动的特征决定了油气沿断裂的垂向泵吸运移呈周期性、间歇性和脉动的特点,同时也决定了油气易于在断裂错开的最新层位聚集成藏。通过克拉2气田天然气运聚成藏过程物理模拟实验结果表明,紧邻圈闭的盐下断裂为有效的天然气运移通道,穿盐断裂为无效的天然气运移通道,天然气在地震泵抽吸作用下沿断裂运移速度快、效率高,在断裂活动的短时间内可以大规模运聚成藏。  相似文献   
113.
In recent decades, the dominant planning discourse has undergone a great change from a previous top-down approach towards collaborative and communicative planning. Instead of merely planning for the people in a technocratic and positivist approach, planners are increasingly expected to pay attention to the voices of the citizens. However, within this new participatory approach there is a growing post-colonial and feminist critique pointing out that not all voices are being heard. This critique sheds light on inherent power relations within the collaborative and communicative planning discourse. In particular, the voices of women in marginalised neighbourhoods are often neglected (Sandercock Towards cosmopolis. Planning for multicultural cities. New York: Wiley, 1998; Cornwall World Development, 31(8), 1325–1342, 2003; Peleman Tijdschrift voor Economische en Sociale Geografie, 94(2), 151–163, 2003; Cameron and Grant-Smith Urban Policy and Research, 23(1), 21–36, 2005). Participatory planning in marginalised housing areas demands both a great sensibility to citizens’ everyday life worlds, and a more reflexive planner role. However, the complexities of the planner’s praxis and uncertainties in the planner’s roles become an obstacle to develop a more inclusive participatory approach. Difficulties of reaching out to the whole community is often recognised, but seldom fully dealt with, neither in theory, nor in practice.
Carina ListerbornEmail:
  相似文献   
114.
通过对滇东南地区区域构造的研究,发现该地区矿床的形成主要受控于构造作用。以广南金矿矿区构造和矿石构造解析作为基础,结合对矿区动力学背景的分析,指出极其发育的NW向、NE向和EW向断裂构造是矿区构造发育的主要特点,而金矿床的就位主要受制于前期构造活动形成的断层及不整合面,右行压剪作用及后期的伸展作用确定了现今的矿体分布特征。矿区发育的角砾状、浸染状和脉状矿石揭示,断裂活动和热液蚀变在成矿过程中起重要作用。  相似文献   
115.
海洋路由勘测对海底光缆工程的影响分析   总被引:1,自引:0,他引:1  
介绍了水深、海底坡度、土壤剪切强度以及潮流、雷暴等海洋路由各勘测要素及其在海底光缆通信施工中的作用,并对它们在施工中的作用及其必要性进行了评价,从而使海洋路由勘测与施工的需要结合得更紧密,更具有针对性。  相似文献   
116.
This review summarizes main research findings in soil fauna eco-geography in China in the past 30 years. The subject areas and main results were overviewed including biodiversity and eco-geological distribution of soil fauna communities. Studies of ecological distributions of soil fauna and dynamic ranges in space from tropical, subtropical to temperate regions, and in categories from forest, grassland, desert, wetland, farmland to urban ecosystems, the responses and indications of soil fauna to soil environments. Effects of intensive disturbance such as fire, grazing, farming, fertilization on soil fauna include sensitive (e.g. nematode) and rare groups and community indexes. The functions of soil fauna were discussed including environmental construction, environmental purification, litter decomposition and elements cycling. Interactions between soil fauna and other biota in soil ecosystems and linking between aboveground and belowground diversity and the effects of global change on soil fauna community in China were also included. Finally, the authors pointed out common interests in soil fauna eco-geographical studies, which include application of molecule biology into soil fauna taxa; function and mechanism of soil fauna community diversity; interaction between aboveground and belowground ecosystems; effects of disturbance, pollution, biological invasion, and global change on soil fauna community and function. The review is to provide a scientific basis for promoting soil fauna eco-geographical studies in China.  相似文献   
117.
我国土壤动物生态地理研究进展   总被引:40,自引:0,他引:40  
通过回顾我国近30年来土壤动物生态地理研究的进展,概述了我国土壤动物群落多样性及生态地理分布。包括我国从热带、亚热带到温带,从森林、草地、沙漠到湿地、农田乃至城市等诸多生态系统。总结了土壤动物群落对环境的响应及其指示意义研究的相关进展,从土壤动物对环境的营造、净化及其在生态系统凋落物分解和物质循环中的作用三个方面论述了土壤动物的功能,最后介绍了土壤动物与其他生物的互作、地上地下的生态学联系、全球变化对土壤动物群落的影响等热点领域的研究现状,并提出了未来土壤动物生态地理研究的热点问题。包括分子生物技术在土壤动物分类研究中的应用;土壤动物群落多样性的功能和机理;地上与地下生态系统的交互作用;干扰、污染、生物入侵和全球变化对土壤动物群落和功能的影响等。  相似文献   
118.
通过研究中国大陆1910年以来8级以上特大地震和国外几组典型特大地震对震源邻近区域的影响,发现特大地震往往发生在断裂带上,一组或一次特大地震可能使发震断裂部分破裂,未破裂断裂又是大震的空段,该空段短时间内可能会发生大震(起到增震作用);反之,发震断裂完全破裂或没有大震空段,震源邻近区域短时间可能不会发生大震(起到减震作用)。依据这一结果,特大地震发生后,可对震源邻近区域后续大震作短、中期预报。  相似文献   
119.
Food preferences, feeding attributes, trophic guilds, and ontogenetic changes in diet compositions of 45 fish species collected along coastal waters in the southern areas of the South China Sea, Thailand were examined. Most species had high food intake and fed on specific ranges of food types. Shrimp was the most important food (31.7%), followed by calanoid copepod (16.8%), fish (12.7%) and gammarid amphipod (8.3%). These fishes can be categorized into six different trophic guilds and further divided into four categories namely; piscivore, zooplanktivore, zoobenthivore and miscellaneous/opportunist. Numbers of feeding guilds at each depth vary between four and five. Four of these are consistently found throughout the year at all zones; shrimp predator, piscivore, calanoid copepod feeder and a combination of polychaete and other food feeders. Ontogenetic studies indicate that fishes are more likely to group according to species rather than size. This scientific information is important when examining the complex association between fishes and identifying groups of species using similar resources.  相似文献   
120.
社会资本在可持续发展中的作用   总被引:3,自引:0,他引:3  
可持续发展指既满足当代人的发展需求又不损害、不掠夺后代发展需求能力的发展。它要求人类社会经济系统在地球生态系统承载能力下运作;要求社会发展不能单纯以经济增长为目的,而是要在保护生态环境基础上提高人类福利。社会资本概念为可持续发展提供了一个有用的工具。它不但使人类意识到可持续发展的内涵,而且运用社会资本可以限制自然资本开采、并减缓其对环境的破坏,提高制造资本利用效率,充分利用人力资本,从而推动可持续发展进程。介绍社会资本概念的基础上,从促进经济发展、自然资源可持续利用管理、环境保护以及缓解贫困等方面,阐述了社会资本促进可持续发展的理论机制。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号