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   21508篇
  免费   131篇
  国内免费   100篇
安全科学   322篇
废物处理   1322篇
环保管理   2651篇
综合类   2406篇
基础理论   6265篇
环境理论   5篇
污染及防治   4796篇
评价与监测   1817篇
社会与环境   2104篇
灾害及防治   51篇
  2023年   54篇
  2022年   115篇
  2021年   97篇
  2020年   81篇
  2019年   87篇
  2018年   1725篇
  2017年   1630篇
  2016年   1493篇
  2015年   324篇
  2014年   290篇
  2013年   804篇
  2012年   814篇
  2011年   1927篇
  2010年   1217篇
  2009年   1123篇
  2008年   1521篇
  2007年   1923篇
  2006年   456篇
  2005年   503篇
  2004年   396篇
  2003年   542篇
  2002年   539篇
  2001年   540篇
  2000年   361篇
  1999年   207篇
  1998年   177篇
  1997年   138篇
  1996年   147篇
  1995年   181篇
  1994年   136篇
  1993年   109篇
  1992年   134篇
  1991年   123篇
  1990年   135篇
  1989年   137篇
  1988年   98篇
  1987年   93篇
  1986年   72篇
  1985年   92篇
  1984年   110篇
  1983年   99篇
  1982年   85篇
  1981年   75篇
  1980年   64篇
  1979年   70篇
  1977年   54篇
  1976年   48篇
  1975年   54篇
  1974年   52篇
  1973年   53篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
River flooding impacts human life and infrastructure, yet provides habitat and ecosystem services. Traditional flood control (e.g., levees, dams) reduces habitat and ecosystem services, and exacerbates flooding elsewhere. Floodplain restoration (i.e., bankfull floodplain reconnection and Stage 0) can also provide flood management, but has not been sufficiently evaluated for small frequent storms. We used 1D unsteady Hydrologic Engineering Center's River Analysis System to simulate small storms in a 5 km-long, second-order generic stream from the Chesapeake Bay watershed, and varied % channel restored (starting at the upstream end), restoration location, restoration bank height (distinguishes bankfull from Stage 0 restoration), and floodplain width/Manning's n. Stream restoration decreased (attenuated) peak flow up to 37% and increased floodplain exchange by up to 46%. Floodplain width and % channel restored had the largest impact on flood attenuation. The incremental effects of new restoration projects on flood attenuation were greatest when little prior restoration had occurred. By contrast, incremental effects on floodplain exchange were greatest in the presence of substantial prior restoration, setting up a tradeoff. A similar tradeoff was revealed between attenuation and exchange for project location, but not bank height or floodplain width. In particular, attenuation and exchange were always greater for Stage 0 than for bankfull floodplain restoration. Stage 0 thus may counteract human impacts such as urbanization.  相似文献   
2.
3.
The purpose of the research is to identify the critical challenges that are impeding the adoption of e-mobility in India. It also aims to give a roadmap how to address these challenges while taking into considerations concerns of all the relevant stakeholders. Based on an in-depth literature review, an exploratory research design is employed to delve deep into various aspects of e-mobility. This is followed by a three-phase Delphi technique to identify and rate the e-mobility challenges in the Indian context. The study successfully identifies four different categories of challenges and proposes integrative framework for e-mobility. Further, the research goes on to lay out the future roadmap for mass adoption of electric vehicles (EVs) in India. The research is novel in terms of presenting a holistic viewpoint on e-mobility in India. Its originality lies in identifying the major inhibitors obstructing EVs adoption in India and then suggesting the roadmap how to overcome these impediments for mass adoption of e-mobility.  相似文献   
4.
5.
6.
7.
The periodicity of fires in larch forests of Evenkia and their relationship with landscape elements have been studied. Cross-sections with “burns” in them caused by past fires have been analyzed in 72 test plots; the fire chronology encompassed the period from the 15th to the 20th century. The between-fire intervals (BFIs) have been calculated by two methods: (I) on the basis of burns alone and (II) on the basis of burns and the start of growth of the new generation of larch after the earliest fire. The BFI depends on local orographic features; it is 86 ± 11 (105 ± 12), 61 ± 8 (73 ± 8), 139 ± 17 (138 ± 18), and 68 ± 14 (70 ± 13) years for northeastern slopes, southwestern slopes, bogs, and flatlands, respectively. The mean BFIs calculated by methods I and II are 82 ± 7 and 95 ± 7 years, respectively. The permafrost horizon rises at a mean rate of 0.3 cm per year after a forest fire. It has been shown that the number of fires regularly peaks at periods of 36 and 82 years. There is also a temporal trend in fire frequency: the mean BFI was approximately 100 years in the 19th century and 65 years in the 20th century.  相似文献   
8.
9.
10.
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