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   5679篇
  免费   63篇
  国内免费   24篇
安全科学   144篇
废物处理   298篇
环保管理   448篇
综合类   897篇
基础理论   1390篇
环境理论   6篇
污染及防治   1818篇
评价与监测   429篇
社会与环境   308篇
灾害及防治   28篇
  2023年   58篇
  2022年   140篇
  2021年   156篇
  2020年   80篇
  2019年   91篇
  2018年   200篇
  2017年   221篇
  2016年   282篇
  2015年   197篇
  2014年   295篇
  2013年   453篇
  2012年   320篇
  2011年   371篇
  2010年   247篇
  2009年   208篇
  2008年   343篇
  2007年   313篇
  2006年   266篇
  2005年   208篇
  2004年   183篇
  2003年   161篇
  2002年   137篇
  2001年   90篇
  2000年   43篇
  1999年   51篇
  1998年   26篇
  1997年   28篇
  1996年   30篇
  1995年   40篇
  1994年   45篇
  1993年   18篇
  1992年   26篇
  1991年   30篇
  1990年   21篇
  1989年   17篇
  1988年   17篇
  1987年   12篇
  1986年   27篇
  1985年   14篇
  1984年   13篇
  1983年   15篇
  1982年   19篇
  1981年   10篇
  1980年   14篇
  1972年   9篇
  1966年   16篇
  1965年   10篇
  1957年   9篇
  1956年   12篇
  1954年   9篇
排序方式: 共有5766条查询结果,搜索用时 296 毫秒
41.
Cytogenetic study of chorionic villi sampled because of advanced maternal age revealed, after overnight culture, an apparently non-mosaic trisomy 7. Amniocentesis showed exclusively normal mitoses, and the pregnancy continued normally. One hundred mitoses from cord blood of the normal newborn revealed a non-mosaic 46,XX complement. No cells with a proven trisomy 7 were found in cultures from either of two biopsies of the morphologically normal placenta, but the peripheral biopsy showed in multiple cultures an abnormal clone: 47,XX, + 20,-2,-21, + t(2;21)(p13;q22). To our knowledge, this is the first case of non-mosaic trisomy 7 detected on CVS which has had follow-up studies of amniotic fluid, cord blood, and term placenta.  相似文献   
42.
The objective of this study was to explore women's attitudes towards prenatal diagnosis of trisomy 21 and to examine some of the factors possibly responsible for these attitudes before implementing in real practice serological screening of pregnant women at risk for trisomy 21. We carried out a telephone survey on a representative sample of women who had recently had a normal livebirth delivery in the Marseille district in 1990. The participation rate was 80 per cent and the average age of the mothers was 28-9 years. Among the 514 women interviewed, 78 per cent stated that they would ask for an amniocentesis for a 1 per cent risk of trisomy 21 at their next pregnancy. When adjusting for confounding factors, the decision to have or not to have an amniocentesis was found to depend not only on the women's attitude towards induced abortion, but also on their understanding of the risk involved and on the social context (knowing a handicapped child, discussion with the father). It also depended on the women's age and on what they knew about amniocentesis from the medical point of view. The risk of miscarriage can influence a woman's choice but this objection was not found to affect the women's decisions significantly in our survey. The data showed the existence of a high potential demand for fetal karyotyping.  相似文献   
43.
During a 7-year period, 117 fetal karyotypes were available from 131 genetic amniocenteses. These procedures were performed between 14 and 37 weeks' gestation for the following abnormal ultrasound findings: (1) intrauterine growth retardation (IUGR)—61 cases; (2) fetal malformation—71 cases; and (3) amniotic fluid volume (AFV) abnormality—60 cases. Chromosomal abnormalities were identified in 19 cases (16.2 per cent). Aneuploidy was 2.5 times as frequent in the presence of malformations than in their absence. No correlation was demonstrated between specific fetal malformations and specific chromosomal abnormalities. Aneuploidy was also twice as frequent in the presence of symmetrical IUGR than in its absence. No chromosomal abnormalities were found among eight cases of asymmetrical IUGR. Four cases of aneuploidy presented with isolated IUGR, three of these involving the X chromosome. The frequency of aneuploidy was the same with or without abnormalities of AFV (14.3 versus 16.4 per cent). No chromosomal abnormality was found associated with isolated AFV abnormalities.  相似文献   
44.
45.
46.
47.
48.
49.
50.
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