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   15188篇
  免费   49篇
  国内免费   31篇
安全科学   138篇
废物处理   1038篇
环保管理   1645篇
综合类   1783篇
基础理论   4403篇
环境理论   9篇
污染及防治   3608篇
评价与监测   1429篇
社会与环境   1193篇
灾害及防治   22篇
  2023年   66篇
  2022年   164篇
  2021年   174篇
  2020年   87篇
  2019年   101篇
  2018年   1555篇
  2017年   1489篇
  2016年   1400篇
  2015年   323篇
  2014年   352篇
  2013年   534篇
  2012年   796篇
  2011年   1671篇
  2010年   928篇
  2009年   801篇
  2008年   1192篇
  2007年   1496篇
  2006年   308篇
  2005年   253篇
  2004年   232篇
  2003年   234篇
  2002年   245篇
  2001年   103篇
  2000年   58篇
  1999年   57篇
  1998年   37篇
  1997年   25篇
  1996年   26篇
  1995年   38篇
  1994年   36篇
  1993年   14篇
  1992年   21篇
  1991年   21篇
  1990年   25篇
  1989年   19篇
  1988年   15篇
  1987年   11篇
  1986年   28篇
  1985年   13篇
  1984年   23篇
  1983年   19篇
  1982年   19篇
  1981年   10篇
  1980年   14篇
  1966年   17篇
  1965年   11篇
  1958年   10篇
  1957年   9篇
  1956年   11篇
  1954年   9篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
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   
62.
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   
63.
64.
65.
66.
67.
68.
69.
70.
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