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   6905篇
  免费   51篇
  国内免费   32篇
安全科学   146篇
废物处理   279篇
环保管理   628篇
综合类   1007篇
基础理论   1479篇
环境理论   5篇
污染及防治   1680篇
评价与监测   555篇
社会与环境   1178篇
灾害及防治   31篇
  2022年   71篇
  2021年   87篇
  2020年   46篇
  2019年   60篇
  2018年   130篇
  2017年   146篇
  2016年   180篇
  2015年   117篇
  2014年   231篇
  2013年   568篇
  2012年   255篇
  2011年   312篇
  2010年   244篇
  2009年   275篇
  2008年   331篇
  2007年   365篇
  2006年   293篇
  2005年   279篇
  2004年   255篇
  2003年   237篇
  2002年   228篇
  2001年   254篇
  2000年   206篇
  1999年   92篇
  1998年   68篇
  1997年   78篇
  1996年   63篇
  1995年   83篇
  1994年   67篇
  1993年   60篇
  1992年   60篇
  1991年   62篇
  1990年   72篇
  1989年   57篇
  1988年   45篇
  1987年   38篇
  1986年   48篇
  1985年   48篇
  1984年   53篇
  1983年   40篇
  1982年   49篇
  1981年   40篇
  1980年   48篇
  1979年   46篇
  1977年   31篇
  1975年   32篇
  1973年   34篇
  1972年   39篇
  1971年   30篇
  1969年   32篇
排序方式: 共有6988条查询结果,搜索用时 109 毫秒
11.
The most widely used method for fetocide in late termination of pregnancy for fetal abnormalities (TOPFA) consists of injecting of potassium chloride (KCl) into the fetal heart and is likely to be painful after 22 weeks of gestation. We studied ten consecutive women undergoing TOPFA between 22 and 38 weeks. This technique for fetocide consisted of a single umbilical vein puncture under ultrasound guidance with injections of sufentanil 5 µg followed by KCl 2 g. No electrocardiographic modifications could be observed and maternal plasma potassium levels did not show any significant variation throughout the procedure. Fetal umbilical phlebotomy for fetal analgesia followed by fetocide therefore appears to be a safe procedure for the mother and allows the fetus to die without pain when late termination of pregnancy (TOP) is indicated. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
12.
The abundance and trophic structure of zooplankton along the longitudinal profile of two typical rivers in the Yaroslavl sector of the Volga region are determined by anthropogenic and zoogenic factors. The distribution of zooplankton under the influence of these factors is described by the concept of patch dynamics. The abundance of zooplankton reaches the highest values in the ameliorated upper reaches of rivers and in beaver ponds.  相似文献   
13.
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   
14.
15.
16.
17.
18.
19.
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   
20.
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   
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