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   41642篇
  免费   438篇
  国内免费   354篇
安全科学   1219篇
废物处理   1582篇
环保管理   5833篇
综合类   6254篇
基础理论   11712篇
环境理论   24篇
污染及防治   11187篇
评价与监测   2537篇
社会与环境   1795篇
灾害及防治   291篇
  2022年   266篇
  2021年   302篇
  2020年   230篇
  2019年   321篇
  2018年   563篇
  2017年   553篇
  2016年   832篇
  2015年   712篇
  2014年   1045篇
  2013年   3288篇
  2012年   1246篇
  2011年   1780篇
  2010年   1451篇
  2009年   1511篇
  2008年   1812篇
  2007年   1919篇
  2006年   1695篇
  2005年   1417篇
  2004年   1417篇
  2003年   1338篇
  2002年   1342篇
  2001年   1677篇
  2000年   1196篇
  1999年   737篇
  1998年   576篇
  1997年   576篇
  1996年   615篇
  1995年   659篇
  1994年   602篇
  1993年   547篇
  1992年   527篇
  1991年   505篇
  1990年   506篇
  1989年   534篇
  1988年   465篇
  1987年   419篇
  1986年   371篇
  1985年   401篇
  1984年   393篇
  1983年   429篇
  1982年   438篇
  1981年   391篇
  1980年   332篇
  1979年   371篇
  1978年   301篇
  1977年   254篇
  1976年   257篇
  1975年   254篇
  1973年   238篇
  1972年   273篇
排序方式: 共有10000条查询结果,搜索用时 625 毫秒
671.
672.
Prenatal diagnosis of the cerebro-hepato-renal (Zellweger) syndrome has been performed in 10 pregnancies at risk by measuring both the activity of acyl CoA: dihydroxyacetonephosphate acyltransferase (DHAP-AT) and the de novo plasmalogen biosynthesis, either in cultured amniotic fluid cells or in fibroblasts cultured from a chorionic villus biopsy. In 7 of the pregnancies both tests indicated no abnormality. All 7 continued to term and normal infants were delivered. However, in amniotic fluid cells from 2 fetuses affected by Zellweger syndrome unequivocal differences from control values were found. The activity of DHAP-AT was clearly deficient and the de novo plasmalogen biosynthesis was impaired. In one pregnancy at risk prenatal diagnosis was performed during the first trimester by measuring both the DHAP-AT activity and the de novo plasmalogen biosynthesis in fibroblasts cultured from a chorionic villi biopsy. From the deficient DHAP-AT activity and the impaired de novo plasmalogen biosynthesis it was concluded that the fetus was affected. This was confirmed biochemically after induced abortion. It can be concluded that measurement of the DHAP-AT activity and the de novo plasmalogen biosynthesis provides convenient methods for the early prenatal detection of Zellweger syndrome.  相似文献   
673.
674.
675.
676.
Necrotic brown lesions developing on leaves and fruits of lemon, and other plants, near fossil-fuel-burning power plants emitting vanadium-rich ash, were reproduced experimentally by inoculating leaves with this type of ash, which is strongly acidic. Comparable lesions were formed when drops of vanadium oxide, dissolved in NaOH, were put on leaves and fruits. Neutralizing, or adding excess H2SO4 (to pH 3), did not alter lesion formation. The histology of these lesions was similar to that of lesions attributed to vanadium-rich ash.  相似文献   
677.
We report relatively high citrulline concentration in amniotic fluid of a citrullinemic fetus suggesting that prenatal detection of this condition could be done on this basis in conjunction with a direct or an indirect determination of argininosuccinate synthetase activity in amniotic fluid cells.  相似文献   
678.
679.
680.
The “constituents” quarks and leptons of matter (with rest-mass) are compared with the historical development of “elements” in chemistry. If unsaturated quarks induce high (and at the moment unpredictable) rest-masses above l0GeV, we have a new view of nuclei comprising (2Z + N) u-quarks and (Z +2N) d-quarks in their low-energy states, without any reference to protons and neutrons as permanent building-blocks. Recent studies of quarks and possible rishons (sub-quarks) and technicolour hadrons are reviewed, and the rôle of identity and cardinality in quantum mechanics analyzed.  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