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   93499篇
  免费   1235篇
  国内免费   1142篇
安全科学   3814篇
废物处理   3376篇
环保管理   14401篇
综合类   21217篇
基础理论   26703篇
环境理论   73篇
污染及防治   16116篇
评价与监测   5618篇
社会与环境   3971篇
灾害及防治   587篇
  2022年   813篇
  2021年   823篇
  2020年   653篇
  2019年   875篇
  2018年   1182篇
  2017年   1229篇
  2016年   2197篇
  2015年   1827篇
  2014年   2581篇
  2013年   9254篇
  2012年   2308篇
  2011年   2689篇
  2010年   3320篇
  2009年   3480篇
  2008年   2278篇
  2007年   2191篇
  2006年   2517篇
  2005年   2397篇
  2004年   2746篇
  2003年   2568篇
  2002年   2104篇
  2001年   2461篇
  2000年   2081篇
  1999年   1535篇
  1998年   1379篇
  1997年   1373篇
  1996年   1494篇
  1995年   1602篇
  1994年   1495篇
  1993年   1344篇
  1992年   1351篇
  1991年   1312篇
  1990年   1269篇
  1989年   1220篇
  1988年   1067篇
  1987年   994篇
  1986年   998篇
  1985年   1075篇
  1984年   1164篇
  1983年   1183篇
  1982年   1183篇
  1981年   1101篇
  1980年   948篇
  1979年   943篇
  1978年   828篇
  1977年   729篇
  1976年   646篇
  1974年   629篇
  1973年   661篇
  1972年   677篇
排序方式: 共有10000条查询结果,搜索用时 468 毫秒
371.
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   
372.
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   
373.
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   
374.
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   
375.
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   
376.
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   
377.
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   
378.
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   
379.
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   
380.
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