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   218篇
  免费   10篇
  国内免费   10篇
安全科学   3篇
环保管理   15篇
综合类   160篇
基础理论   26篇
环境理论   3篇
污染及防治   1篇
社会与环境   21篇
灾害及防治   9篇
  2022年   4篇
  2021年   3篇
  2020年   1篇
  2019年   9篇
  2018年   13篇
  2017年   3篇
  2016年   3篇
  2015年   3篇
  2014年   2篇
  2013年   6篇
  2012年   6篇
  2011年   18篇
  2010年   15篇
  2009年   9篇
  2008年   11篇
  2007年   11篇
  2006年   12篇
  2005年   11篇
  2004年   6篇
  2003年   13篇
  2002年   16篇
  2001年   15篇
  2000年   6篇
  1999年   1篇
  1998年   3篇
  1997年   1篇
  1996年   1篇
  1995年   5篇
  1994年   6篇
  1993年   4篇
  1992年   3篇
  1991年   1篇
  1989年   3篇
  1988年   6篇
  1985年   1篇
  1984年   2篇
  1983年   1篇
  1982年   1篇
  1981年   3篇
排序方式: 共有238条查询结果,搜索用时 15 毫秒
31.
32.
33.
34.
35.
Hyperechogenic fetal bowel is prenatally detected by ultrasound during the second trimester of pregnancy in 0.1% to 1.8% of foetuses. It has been described as a normal variant and has often been associated with severe diseases, notably Down syndrome. The aim of the present study was to determine the risk of trisomy 21 in a prospective study of 680 fetuses with hyperechogenic foetal bowel. Karyotyping was performed on amniotic cells in 632 cases, and outcome was known in 655 cases. A 2.5% risk of Down syndrome and a 1% risk of other severe chromosomal anomalies were observed. Hyperechogenicity was isolated in 11/17 Down syndrome cases, and associated with other ultrasound anomalies in all seven cases of severe chromosomal anomalies. In conclusion, fetal bowel hyperechogenicity indicates a risk of chromosomal anomalies ten-fold higher than that expected on the basis of maternal age, therefore justifying invasive procedures. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
36.
We present a case report on a fetus with multiple malformations, diagnosed by ultrasound at 20 weeks' gestation. From the combination of intrauterine growth retardation and limb abnormalities that were observed, the most likely diagnosis was considered to be Cornelia de Lange Syndrome (CdLS). Following counselling, the mother opted to terminate the pregnancy. Chromosome analysis of cultured amniotic fluid cells showed a karyotype of 46,XX,t(3;5)(q21;p13). Postmortem examination of the baby confirmed the presence of features consistent with a diagnosis of CdLS. This case provides a report of a definitive diagnosis of Cornelia de Lange Syndrome, suspected on the basis of ultrasound imaging and confirmed by amniocentesis findings. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
37.
In a group of 149 women who had undergone routine first trimester screening using fetal nuchal translucency thickness (NT) and maternal serum free β-hCG and pregnancy associated plasma protein-A (PAPP-A) in two consecutive pregnancies the within person between pregnancy biological variability of these markers has been assessed. For fetal NT there was no correlation between NT MoM in the first and second pregnancy (r=0.0800). For maternal serum free β-hCG MoM a significant correlation was observed (r=0.4174) as was also found for PAPP-A MoM (r=0.3270). The implications for such between pregnancy marker association is that women who have an increased risk of Down syndrome in their first pregnancy are 1.5–2 times more likely to repeat this event in their next pregnancy. This observation may be useful in counselling women in the first trimester screening of a subsequent pregnancy. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   
38.
39.
40.
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