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   8014篇
  免费   49篇
  国内免费   32篇
安全科学   593篇
废物处理   277篇
环保管理   647篇
综合类   1753篇
基础理论   1431篇
环境理论   3篇
污染及防治   1645篇
评价与监测   547篇
社会与环境   1167篇
灾害及防治   32篇
  2022年   70篇
  2021年   88篇
  2019年   57篇
  2018年   121篇
  2017年   141篇
  2016年   173篇
  2015年   111篇
  2014年   226篇
  2013年   577篇
  2012年   246篇
  2011年   294篇
  2010年   240篇
  2009年   272篇
  2008年   321篇
  2007年   357篇
  2006年   279篇
  2005年   273篇
  2004年   406篇
  2003年   377篇
  2002年   283篇
  2001年   290篇
  2000年   199篇
  1999年   91篇
  1998年   111篇
  1997年   85篇
  1996年   65篇
  1995年   134篇
  1994年   115篇
  1993年   93篇
  1992年   87篇
  1991年   81篇
  1990年   101篇
  1989年   78篇
  1988年   75篇
  1987年   67篇
  1986年   65篇
  1985年   59篇
  1984年   64篇
  1983年   49篇
  1982年   56篇
  1981年   41篇
  1980年   45篇
  1979年   50篇
  1973年   42篇
  1972年   41篇
  1919年   49篇
  1918年   45篇
  1916年   55篇
  1914年   74篇
  1913年   106篇
排序方式: 共有8095条查询结果,搜索用时 656 毫秒
11.
Male phenotype associated with a 45,X karyotype is an infrequent finding. We present a case diagnosed prenatally on amniocentesis performed for maternal age. The male phenotype was associated with a translocation of a distal part of Yp including the pseudoautosomal SHOX gene and SRY gene on the short arm of a chromosome 21. By DNA analysis we could show that the X chromosome was of maternal origin and that the breakpoint was in interval 3 of the Y chromosome. Mechanisms and genetic counselling are discussed based on a review of published cases of 45,X and XX males. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
12.
13.
14.
15.
16.
17.
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   
18.
The effect of mountain relief and industrial air pollution on biometric parameters of pine stands was studied. The empirical–statistical models of the dependence of biometric characteristics on the parameters of forest sites were developed using raster modeling and multivariate analysis. The possibility of predicting changes in the biometric parameters at any site on the basis of these models is shown.  相似文献   
19.
20.
Assessment of environmental changes in the Orinoco River delta   总被引:1,自引:0,他引:1  
Major anthropogenic driven changes in the hydrologic and sedimentation patterns of the Orinoco River have had an impact on environmental conditions in the delta. The abrupt water flow reduction from 3,600 to 200 m3 s–1 in one of its major distributaries resulting from dam construction forced its transformation from a fresh-water body into a tidal channel with an increase in salinity level (as far as 100 km upstream) and with well-mixed water at the mouth and estuarine connection to the Paria Gulf. Three different sectors along this distributary can be identified (indicated by the Na/Cl ratio in the water). As a result, noticeable changes have occurred in the mangrove community which moved about 60 km further upstream. The changes have also promoted the formation of new islands of sediment progradation at the mouth of this distributary, where successional colonization and species replacement by different species of grasses and mangroves take place. Electronic Publication  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