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   17254篇
  免费   62篇
  国内免费   36篇
安全科学   176篇
废物处理   1133篇
环保管理   1778篇
综合类   2477篇
基础理论   4761篇
环境理论   14篇
污染及防治   4171篇
评价与监测   1535篇
社会与环境   1283篇
灾害及防治   24篇
  2023年   75篇
  2022年   177篇
  2021年   190篇
  2020年   100篇
  2019年   118篇
  2018年   1577篇
  2017年   1513篇
  2016年   1440篇
  2015年   348篇
  2014年   410篇
  2013年   642篇
  2012年   841篇
  2011年   1753篇
  2010年   1010篇
  2009年   889篇
  2008年   1267篇
  2007年   1579篇
  2006年   372篇
  2005年   325篇
  2004年   272篇
  2003年   294篇
  2002年   297篇
  2001年   188篇
  2000年   116篇
  1999年   87篇
  1998年   59篇
  1997年   48篇
  1996年   41篇
  1995年   62篇
  1994年   72篇
  1993年   28篇
  1992年   43篇
  1991年   41篇
  1990年   35篇
  1989年   31篇
  1986年   38篇
  1984年   38篇
  1983年   32篇
  1982年   31篇
  1966年   40篇
  1965年   42篇
  1964年   26篇
  1963年   32篇
  1962年   26篇
  1961年   36篇
  1960年   29篇
  1959年   26篇
  1958年   26篇
  1957年   35篇
  1956年   29篇
排序方式: 共有10000条查询结果,搜索用时 468 毫秒
71.
72.
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   
73.
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   
74.
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   
75.
76.
The radiation budget of planets substantially determines their climates. For the terrestrial planets having their own imperceptible heat source compared to the solar radiation, the radiation budget supplies energy that can be transformed and used in their atmospheres and at their surfaces. The crucial role of the radiation budget for the Earth's climate is manifested in current international programs like the World Climate and Global Change Programs. The intercomparison and analysis of the radiation budget of the terrestrial planets, due to quite different atmospheric compositions and external conditions, provide a deeper insight into the relations of the different components of the radiation budget.  相似文献   
77.
78.
79.
80.
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