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   27735篇
  免费   257篇
  国内免费   203篇
安全科学   709篇
废物处理   927篇
环保管理   3630篇
综合类   7607篇
基础理论   6188篇
环境理论   8篇
污染及防治   6763篇
评价与监测   1340篇
社会与环境   899篇
灾害及防治   124篇
  2018年   305篇
  2017年   300篇
  2016年   438篇
  2015年   335篇
  2014年   481篇
  2013年   1980篇
  2012年   624篇
  2011年   898篇
  2010年   741篇
  2009年   871篇
  2008年   940篇
  2007年   994篇
  2006年   889篇
  2005年   740篇
  2004年   778篇
  2003年   777篇
  2002年   700篇
  2001年   977篇
  2000年   668篇
  1999年   457篇
  1998年   334篇
  1997年   306篇
  1996年   351篇
  1995年   376篇
  1994年   402篇
  1993年   358篇
  1992年   377篇
  1991年   366篇
  1990年   404篇
  1989年   395篇
  1988年   319篇
  1987年   317篇
  1986年   294篇
  1985年   307篇
  1984年   315篇
  1983年   310篇
  1982年   320篇
  1981年   337篇
  1980年   286篇
  1979年   294篇
  1978年   255篇
  1977年   230篇
  1976年   247篇
  1974年   260篇
  1973年   238篇
  1972年   229篇
  1971年   218篇
  1968年   230篇
  1967年   261篇
  1966年   222篇
排序方式: 共有10000条查询结果,搜索用时 98 毫秒
641.
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   
642.
643.
644.
Scheffler  H.  Witkowski  S.  Becke-Goehring  M.  Bock  R.  Schuster  P.  Habermehl  G.  Jaenicke  L.  Schröder  F. A.  Tritsch  M. F.  Creutzfeldt  O.  Ziegler  H.  Hölldobler  B. 《Die Naturwissenschaften》1984,71(10):540-543
The Science of Nature -  相似文献   
645.
This article reports the results of a retrospective study designed to examine the responses of couples to genetic amniocentesis and subsequent therapeutic abortions due to birth defects. Fourteen women and 12 men were interviewed by experienced interviewers using a structured format designed by the authors, and each interview was audiotaped for later rating. The 5 raters (all women) were instructed to independently rate each interview using forms designed by the authors to elicit information about many aspects of the participant's individual responses as well as perceptions of spouse's responses to the process of pregnancy, amniocentesis, therapeutic abortion, and sequelae. Ratings of all 5 raters were conjoined and an homogeneous narrative was constructed for each interview. Results indicate, in general, that the respondent couples coped well with this experience. In fact 70 per cent of the respondent couples described their marital relationships as becoming closer as a result of their experience. Only a few participants reported long-term deleterious effects. Most couples coped by relying on relatives, friends, and occasionally, professional counsellors. In addition, most participants in this study suggested ways to improve the medical and psychological aspects of this experience.  相似文献   
646.
647.
648.
649.
650.
The role of the development of information fidelity systems in evolution is explored, with evidence that the loss in the ability to maintain the integrity of homeostasis in organisms over time, aging, is correlated with the loss in the ability to maintain integrity at the molecular biological level. Evolutionary-comparative analysis places an upper limit on the number of these systems important to the evolution of longevity in the primates, and suggests the importance of insuring the stability of information bearing macromolecules in evolution and the role of modulators of damage to these moieties in the expression of the senescent state  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