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   2013篇
  免费   19篇
  国内免费   24篇
安全科学   52篇
废物处理   71篇
环保管理   261篇
综合类   480篇
基础理论   379篇
环境理论   2篇
污染及防治   565篇
评价与监测   112篇
社会与环境   119篇
灾害及防治   15篇
  2023年   21篇
  2022年   19篇
  2021年   33篇
  2020年   24篇
  2019年   29篇
  2018年   52篇
  2017年   53篇
  2016年   67篇
  2015年   81篇
  2014年   82篇
  2013年   92篇
  2012年   89篇
  2011年   127篇
  2010年   104篇
  2009年   113篇
  2008年   100篇
  2007年   107篇
  2006年   86篇
  2005年   64篇
  2004年   83篇
  2003年   47篇
  2002年   77篇
  2001年   69篇
  2000年   34篇
  1999年   21篇
  1998年   18篇
  1997年   27篇
  1996年   23篇
  1995年   34篇
  1994年   23篇
  1993年   8篇
  1992年   15篇
  1991年   25篇
  1990年   14篇
  1989年   20篇
  1988年   8篇
  1985年   7篇
  1984年   5篇
  1983年   5篇
  1982年   12篇
  1981年   12篇
  1979年   12篇
  1977年   6篇
  1970年   6篇
  1967年   5篇
  1966年   5篇
  1965年   5篇
  1964年   5篇
  1960年   6篇
  1954年   4篇
排序方式: 共有2056条查询结果,搜索用时 15 毫秒
921.
There are millions of small isolatedwetlands in the semi-arid Canadian prairies. These`sloughs' are refuges for wildlife in an area that isotherwise intensively used for agriculture. They areparticularly important as waterfowl habitat, with morethan half of all North American ducks nesting inprairie sloughs. The water levels and ecology of thewetlands are sensitive to atmospheric change and tochanges of agricultural practices in the surroundingfields. Monitoring of the hydrological conditions ofthe wetlands across the region is vital for detectinglong-term trends and for studying the processes thatcontrol the water balance of the wetlands. Suchmonitoring therefore requires extensive regional-scaledata complemented by intensive measurements at a fewlocations. At present, wetlands are being enumeratedacross the region once each year and year-roundmonitoring is being carried out at a few locations. Theregional-scale data can be statistically related toregional climate data, but such analyses cast littlelight on the hydrological processes and have limitedpredictive value when climate and land use arechanging. The intensive monitoring network has providedimportant insights but it now needs to be expanded andrevised to meet new questions concerning the effects ofclimate change and land use.  相似文献   
922.
The flow-through spectrofluorometers, FLUO-IMAGER, were developed to measure the abundance of phytoplankton, including the analysis of pigment composition and concentration of organic pollution and dissolved organic matter (DOM), in continuous mode. The measurements can be carried out without the time-consuming pretreatment of water samples. The analytical concept uses the technique of spectral fluorescent signatures (SFS), based on the systematized spectral library comprising the SFS of major phytoplankton species and chemical pollution. The SFS technique has been applied for several years in qualitative and quantitative screening of organic compounds and phytoplankton in the Baltic, North and Norwegian Seas. The results of the analysis of phytoplankton pigments, the dynamic processes of bloom development, DOM and oil pollution are presented.  相似文献   
923.
924.
925.
It has been proposed that voluntary urban climate programmes overcome shortfalls in mandatory, top-down, state-led government interventions to address climate change risks. Such programmes seek commitments from households and firms to improve their environmental sustainability, but do not have the force of law. City governments are actively developing and implementing such programmes, seeking improved and accelerated urban climate action. There is little evidence, however, of whether their involvement positively affects voluntary programme performance. This article presents qualitative comparative analysis (QCA) of 26 voluntary programmes from Australia, the Netherlands and the US, seeking to understand whether, and if so how, city governments affect the performance of voluntary urban climate programmes. The results will help to inform city governments about the roles they may play in urban climate governance.  相似文献   
926.
927.
Dry and wet deposition onto thirty forest stands in relation to stand structure is studied by sampling throughfall and bulk precipitation. Nine measurement sites are situated in Pseudotsuga menziesii stands, ten in Pinus sylvestris and eleven in Quercus robur stands. All stands are situated within a radius of 1.2 km to assure a more or less equal air pollution load. In each stand, detailed forest structure inventories are made to determine aerodynamic roughness, collecting efficiency and surface area parameters. Measurements to data cover a four month period (April-July 1990). First results show relatively high throughfall deposition in Pseudotsuga menziesii stands. Lowest throughfall fluxes are recorded for Quercus robur and intermediate values for Pinus sylvestris stands. There are indications of a relatively strong canopy exchange in Quercus robur stands during the measurement period. Many results from forest stand structure inventories are not available yet. However, a strong relation is observed between throughfall deposition in Pseudotsuga menziesii stands and total crown volume.  相似文献   
928.
Rabbits have been suggested as a zoonotic source of Hepatitis E virus. Phylogenetic analysis of HEV isolates from farmed, wild and pet rabbits in the Netherlands (23, 0, and 60 % respectively) showed them to be grouped amongst published rabbit HEV sequences and distinct from most human isolates. Dutch rabbits are unlikely to be a zoonotic source.  相似文献   
929.
930.
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