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   34304篇
  免费   373篇
  国内免费   274篇
安全科学   1108篇
废物处理   1674篇
环保管理   4285篇
综合类   5220篇
基础理论   8807篇
环境理论   14篇
污染及防治   8851篇
评价与监测   2494篇
社会与环境   2301篇
灾害及防治   197篇
  2023年   187篇
  2022年   390篇
  2021年   455篇
  2020年   262篇
  2019年   323篇
  2018年   614篇
  2017年   659篇
  2016年   949篇
  2015年   694篇
  2014年   1095篇
  2013年   2831篇
  2012年   1280篇
  2011年   1657篇
  2010年   1302篇
  2009年   1317篇
  2008年   1667篇
  2007年   1575篇
  2006年   1415篇
  2005年   1234篇
  2004年   1192篇
  2003年   1127篇
  2002年   1040篇
  2001年   1160篇
  2000年   799篇
  1999年   523篇
  1998年   380篇
  1997年   402篇
  1996年   413篇
  1995年   494篇
  1994年   421篇
  1993年   355篇
  1992年   387篇
  1991年   371篇
  1990年   340篇
  1989年   335篇
  1988年   306篇
  1987年   247篇
  1986年   262篇
  1985年   256篇
  1984年   277篇
  1983年   264篇
  1982年   280篇
  1981年   228篇
  1980年   173篇
  1979年   186篇
  1978年   167篇
  1977年   138篇
  1975年   143篇
  1973年   170篇
  1972年   150篇
排序方式: 共有10000条查询结果,搜索用时 640 毫秒
541.
We report a gas chromatographic-mass spectrometric method which allows the very long chain fatty acids content of trophoblastic tissue to be directly measured in samples collected by biopsy between 8 and 11 weeks of gestation. This method has been successfully applied to the detection of fetal Zellweger syndrome in two pregnant women who had previously delivered affected infants. In one of them, increased concentrations of C26:0 (0.254 versus 0.108±0.035 μ/mg proteins) and C24:0 (1.32 versus 0.815±0.325 μ/mg proteins) in trophoblast indicated that the fetus had Zellweger syndrome, a diagnosis confirmed by pathological findings after abortion. In the second case, the pregnancy was allowed to proceed, on the basis of normal concentrations of very long chain fatty acids in trophoblastic tissue, and its outcome was actually a healthy newborn.  相似文献   
542.
543.
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   
544.
545.
546.
547.
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   
548.
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   
549.
550.
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