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   29587篇
  免费   337篇
  国内免费   253篇
安全科学   856篇
废物处理   1121篇
环保管理   4134篇
综合类   5157篇
基础理论   7780篇
环境理论   14篇
污染及防治   7447篇
评价与监测   1811篇
社会与环境   1648篇
灾害及防治   209篇
  2022年   217篇
  2021年   229篇
  2020年   201篇
  2019年   258篇
  2018年   398篇
  2017年   422篇
  2016年   620篇
  2015年   484篇
  2014年   674篇
  2013年   2391篇
  2012年   831篇
  2011年   1164篇
  2010年   954篇
  2009年   1011篇
  2008年   1196篇
  2007年   1253篇
  2006年   1159篇
  2005年   919篇
  2004年   977篇
  2003年   917篇
  2002年   850篇
  2001年   1127篇
  2000年   803篇
  1999年   477篇
  1998年   405篇
  1997年   369篇
  1996年   401篇
  1995年   428篇
  1994年   438篇
  1993年   389篇
  1992年   414篇
  1991年   387篇
  1990年   413篇
  1989年   381篇
  1988年   317篇
  1987年   278篇
  1986年   289篇
  1985年   300篇
  1984年   320篇
  1983年   314篇
  1982年   312篇
  1981年   316篇
  1980年   267篇
  1979年   269篇
  1978年   215篇
  1977年   210篇
  1975年   183篇
  1974年   210篇
  1973年   187篇
  1972年   222篇
排序方式: 共有10000条查询结果,搜索用时 373 毫秒
111.
As a consequence of decreases in the emission rate of sulphur in eastern North America in the late 1970s and early 1980s, sulphate deposition in central Ontario declined by about 40%, but has remained constant for about six years. Plastic Lake, a small, dilute lake on the Precambrian shield that the authors have studied since 1979, acidified between the start of the study and about 1986, but since then has not changed. The authors also monitored the chemistry of streamwater draining the Plastic Lake catchment. Water quality of runoff from an upland site improved rapidly (pH and alkalinity increased, SO4(2-) and Al decreased), but two factors offset these improvements. A small wetland area downstream reversed most of these changes, resulting in a constant output of strong acid from the catchment. In addition, in extremely dry years (1983, 1987, 1989) there were very high concentrations of SO4(2-) in the streamwater, suggesting substantial re-oxidation of reduced S in the catchment.  相似文献   
112.
Benson C  Clay EJ 《Disasters》1986,10(4):303-316
This paper documents the rapid expansion and changes in food aid flows to Sub-Saharan Africa up to mid-1985. Trends for Sub-Saharan Africa as a whole and for the more seriously affected countries are examined, as are the comparative experiences of food aid of individual countries in the region. Table 11 lists the Sub-Saharan African countries and indicates the most seriously affected food-short countries, as defined by the WFP/FAO task force. It should be borne in mind that some practical problems exist in compiling data on food aid. These include lack of availability of reliable data, especially of most recent data; lack of common terminology and definitions; and different accounting systems. These data problems are sometimes a source of confusion. However, the basic facts are clear: food aid gradually emerged during the early 1980s as a resource too often of considerable significance to many countries of Sub-Saharan Africa. These trends were only accelerated with the crisis of 1984-1985. These facts provide a point of reference for further analysis of the sources of the crisis, its actual dimensions and consequences.  相似文献   
113.
Riebsame WE 《Disasters》1985,9(4):295-300
Three recent cases of climate extremes are studied to identify human impacts and response strategies and to identify common characteristics that may help illuminate the nature of climate hazards. The 1980 heat wave in the central United States, 1981 cold wave in Boston, Massachusetts, and recent flooding and lake level rise in northern Utah, illustrate several important aspects of climate hazards that separate them from the more traditional set of catastrophic events (e.g. tornadoes, hurricanes and earthquakes) usually dealt with by hazards research and management. Among those characteristics are an emphasis on health impacts rather than physical damage, accumulative effects rather than short shocks, a tendency for impacts to accrue to certain socio-economic classes, and relatively slow onset. The management and research implications of these hazard characteristics are explored.  相似文献   
114.
Death and injury in earthquakes   总被引:1,自引:0,他引:1  
Alexander D 《Disasters》1985,9(1):57-60
The assumption that the ratio of mortality to morbidity will approximate 1:3 in earthquake disasters is investigated. When it occurs, a 1:3 ratio is most likely to coincide with a Richter magnitude in the range 6.5–7.4, but many other ratios of death to injuries may instead be probable. For each individual disaster the pattern of casualties is likely to be very heterogeneous, but it would be easier to discover regularities if a more standardized definition of 'injury' could be found.  相似文献   
115.
Environment, Development and Sustainability - Environmental deterioration and global warming has created a substantial impact on international companies to incorporate eco-friendly, green supply...  相似文献   
116.
Russian Journal of Ecology - Populations at the border of ranges are considered more vulnerable than those in the center. However, some recent reviews contradict this hypothesis. We have studied...  相似文献   
117.
Russian Journal of Ecology - Abstract—We tested a hypothesis about the different abilities of alien and native plants to form arbuscular mycorrhizae. The studies were carried out in the...  相似文献   
118.
119.
120.
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