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   88916篇
  免费   1224篇
  国内免费   1093篇
安全科学   3718篇
废物处理   3183篇
环保管理   13770篇
综合类   21014篇
基础理论   26105篇
环境理论   72篇
污染及防治   13880篇
评价与监测   5369篇
社会与环境   3586篇
灾害及防治   536篇
  2022年   788篇
  2021年   792篇
  2020年   641篇
  2019年   853篇
  2018年   1103篇
  2017年   1154篇
  2016年   2123篇
  2015年   1816篇
  2014年   2559篇
  2013年   9214篇
  2012年   2141篇
  2011年   2337篇
  2010年   3216篇
  2009年   3382篇
  2008年   1882篇
  2007年   1729篇
  2006年   2188篇
  2005年   2170篇
  2004年   2470篇
  2003年   2326篇
  2002年   1860篇
  2001年   2092篇
  2000年   1896篇
  1999年   1470篇
  1998年   1358篇
  1997年   1348篇
  1996年   1471篇
  1995年   1565篇
  1994年   1459篇
  1993年   1309篇
  1992年   1307篇
  1991年   1274篇
  1990年   1229篇
  1989年   1197篇
  1988年   1033篇
  1987年   964篇
  1986年   990篇
  1985年   1060篇
  1984年   1151篇
  1983年   1174篇
  1982年   1174篇
  1981年   1095篇
  1980年   941篇
  1979年   929篇
  1978年   817篇
  1977年   719篇
  1976年   638篇
  1975年   610篇
  1973年   637篇
  1972年   650篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
351.
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   
352.
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   
353.
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   
354.
Environment, Development and Sustainability - Renewable energy (RE) plays an increasingly important role in the economy of almost every country in the world. In order to examine the state of...  相似文献   
355.
Environment, Development and Sustainability - This study describes the results of groundwater table variation in Thanjavur District before and after the monsoon seasons. Groundwater-level data...  相似文献   
356.
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   
357.
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   
358.
Rate-temperature responses in scyphozoan medusae and polyps   总被引:1,自引:0,他引:1  
The effects of temperature on oxygen consumption and spontaneous rhythmic activity have been investigated in various stages of the life histories of 3 species of jellyfish from the Chesapeake Bay, USA. All 3 species clearly show the ability to acclimate positively to temperature change. Thermal sensitivity of metabolism in the winter medusa Cyanea capillata fulva is fairly low at temperature intervals which are experienced in nature. Polyps of the two summer medusae, Chrysaora quinquecirrha and Aurelia aurita, show reduced metabolic sensitivity at temperatures normally accompanying high developmental activity and the onset of strobilation.  相似文献   
359.
360.
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