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   42976篇
  免费   354篇
  国内免费   260篇
安全科学   978篇
废物处理   2024篇
环保管理   5557篇
综合类   6244篇
基础理论   12342篇
环境理论   23篇
污染及防治   10493篇
评价与监测   3001篇
社会与环境   2708篇
灾害及防治   220篇
  2022年   262篇
  2021年   248篇
  2019年   261篇
  2018年   1836篇
  2017年   1708篇
  2016年   1760篇
  2015年   691篇
  2014年   840篇
  2013年   2503篇
  2012年   1426篇
  2011年   2631篇
  2010年   1853篇
  2009年   1741篇
  2008年   2225篇
  2007年   2602篇
  2006年   1403篇
  2005年   1180篇
  2004年   1208篇
  2003年   1175篇
  2002年   1186篇
  2001年   1461篇
  2000年   997篇
  1999年   623篇
  1998年   477篇
  1997年   487篇
  1996年   493篇
  1995年   536篇
  1994年   488篇
  1993年   442篇
  1992年   462篇
  1991年   423篇
  1990年   429篇
  1989年   463篇
  1988年   379篇
  1987年   343篇
  1986年   314篇
  1985年   332篇
  1984年   338篇
  1983年   365篇
  1982年   361篇
  1981年   297篇
  1980年   269篇
  1979年   292篇
  1978年   256篇
  1977年   220篇
  1976年   222篇
  1975年   209篇
  1974年   199篇
  1973年   195篇
  1972年   222篇
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
591.
The aim of the study was to describe the opinion of pregnant women who had accepted or declined an alpha-fetoprotein (AFP) test, not only on AFP screening in general, but also on whether every pregnant woman should be offered amniocentesis (AC)/chorionic villus sampling (CVS) and an ultrasound scan for fetal malformations. An additional aim was to describe pregnant women's attitudes concerning continued research in the prenatal field. The study was performed as a questionnaire study in two regions over a 1-year period from 1 October 1988 to 30 September 1989. Results are based on answers from 3331 women who had taken an AFP test and 336 women who had declined the offer of a test. A total of 79 per cent of the women thought that an AFP test, 70 per cent that an ultrasound scan for fetal malformations, and 26 per cent that AC or CVS should be offered to all pregnant women. Fifty-nine per cent of the women were positive towards continued research in the prenatal field. Women who had had an AFP test were generally much more positive towards screening and research than women who had declined, who were generally against. Women who had left school without a high school degree were on average more positive towards the screening issues than women who had this degree. In conclusion, the results obtained in this study strongly suggest that women's attitudes are very dependent on how the prenatal screening programme is already organized in their local area.  相似文献   
592.
Monoclonal antibody to fetal haemoglobin (a2γy2) has been proposed as a fetal-specific reagent. We developed an intracellular staining protocol that combines fluorescein isothiocyanate or phycoerythrin conjugated anti-γ with the DNA binding dye Hoechst 33342 to identify and flow sort fetal erythroblasts from maternal blood. Our preliminary observations on anti-γ-positive cells sorted from four different pregnant women are described here, using fluorescence in situ hybridization (FISH) with chromosome-specific probes to identify fetal cells. Our data demonstrate that far fewer candidate fetal cells are sorted with this protocol than by current cell surface staining methods that employ the monoclonal antibody CD71. This results in increased fetal cell sorting purities. With this protocol, standard FISH techniques require modification due to the rigorous fixation with 4 per cent paraformaldehyde. Our initial data indicate the promise of this approach.  相似文献   
593.
594.
595.
596.
597.
598.
599.
600.
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