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   32509篇
  免费   272篇
  国内免费   338篇
安全科学   650篇
废物处理   1829篇
环保管理   4397篇
综合类   4322篇
基础理论   9082篇
环境理论   11篇
污染及防治   7548篇
评价与监测   2528篇
社会与环境   2604篇
灾害及防治   148篇
  2022年   201篇
  2021年   182篇
  2020年   146篇
  2019年   192篇
  2018年   1854篇
  2017年   1743篇
  2016年   1638篇
  2015年   538篇
  2014年   617篇
  2013年   1922篇
  2012年   1154篇
  2011年   2356篇
  2010年   1637篇
  2009年   1500篇
  2008年   1942篇
  2007年   2393篇
  2006年   903篇
  2005年   840篇
  2004年   843篇
  2003年   918篇
  2002年   894篇
  2001年   932篇
  2000年   688篇
  1999年   406篇
  1998年   295篇
  1997年   307篇
  1996年   297篇
  1995年   337篇
  1994年   328篇
  1993年   278篇
  1992年   291篇
  1991年   253篇
  1990年   271篇
  1989年   254篇
  1988年   199篇
  1987年   210篇
  1986年   208篇
  1985年   208篇
  1984年   221篇
  1983年   216篇
  1982年   178篇
  1981年   187篇
  1980年   168篇
  1979年   154篇
  1978年   130篇
  1977年   137篇
  1975年   111篇
  1974年   98篇
  1973年   113篇
  1972年   100篇
排序方式: 共有10000条查询结果,搜索用时 285 毫秒
51.
52.
53.
54.
The effect of industrial air pollution on natural small mammal populations has been studied in the northern taiga subzone of the boreal forest zone. The results of long-term monitoring have been used to demonstrate the possibility of predicting changes in the main population and community characteristics of the animal species studied as dependent on the degree of anthropogenic impact.  相似文献   
55.
56.
57.
58.
59.
Three monoclonal antibodies (MAbs) against trophoblast (GB17, GB21, and GB25) and flow cytometry were used to sort trophoblast-like cells (TLCs) from peripheral blood of pregnant women. Sorted TLCs were processed for electron microscopy and fetal DNA amplification of the Y-specific sequences from mothers carrying male fetuses. At the ultra-structural level, most of the nucleated cells had the morphology of leucocytes, suggesting maternal contaminants, and we did not find the characteristic features of the free inter-villous trophoblast cells. Nevertheless, polymerase chain reaction (PCR) analysis showed an amplification of Y-specific sequences in two out of three samples of sorted TLCs. These results suggest that besides the maternal leucocytes, sufficient trophoblast nucleated fetal cells can be obtained using cell enrichment by sorting. This sensitive method holds promise for non-invasive prenatal diagnosis of fetal sex and if sufficient Y(positive) nuclei are found, for the diagnosis of selected numerical chromosome abnormalities.  相似文献   
60.
The past two decades have witnessed an increase in the exploration for, and development of, mineral resources at Arctic latitudes. Such effort has resulted in the commencement of production at a number of different localities in close proximity to the ocean. Since proximity to a source of transportation for the conveyance of concentrates to the market is a primary requirement governing the economic decisions for the mine to proceed, it is logical that ore deposits near a coastline are primary targets for development.

Closely tied to coastal mining developments is the need to dispose of tailings and waste rock in the most economical manner. Prior to the advent of heightened public awareness and environmental concern, and the enactment of pollution legislation, disposal practices were largely based upon convenience. Currently, however, proposed disposal and operating practices receive closer scrutiny, with a view to providing adequate protection for aquatic resources and habitat. This paper summarizes some of the features of three Arctic mines, wastes from which enter the marine environment, and compares the disposal practices used at each to measures of environmental change as indicated by metal concentrations in various media.  相似文献   
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