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   756篇
  免费   4篇
  国内免费   17篇
安全科学   12篇
环保管理   17篇
综合类   676篇
基础理论   30篇
环境理论   2篇
污染及防治   17篇
评价与监测   6篇
社会与环境   10篇
灾害及防治   7篇
  2023年   2篇
  2022年   2篇
  2021年   7篇
  2020年   8篇
  2018年   3篇
  2017年   4篇
  2016年   5篇
  2015年   2篇
  2014年   4篇
  2013年   19篇
  2012年   20篇
  2011年   80篇
  2010年   69篇
  2009年   53篇
  2008年   53篇
  2007年   59篇
  2006年   52篇
  2005年   53篇
  2004年   50篇
  2003年   52篇
  2002年   46篇
  2001年   30篇
  1999年   2篇
  1997年   1篇
  1996年   2篇
  1995年   36篇
  1994年   29篇
  1993年   3篇
  1992年   2篇
  1991年   1篇
  1990年   4篇
  1989年   3篇
  1988年   4篇
  1987年   1篇
  1986年   3篇
  1985年   1篇
  1984年   6篇
  1983年   4篇
  1982年   1篇
  1979年   1篇
排序方式: 共有777条查询结果,搜索用时 830 毫秒
451.
452.
453.
454.
455.
456.
The aim of this study was to evaluate the detection of fetal structural abnormalities by the 11–14 week scan. 2853 pregnant women were submitted to a routine ultrasound scan between the 11th and 14th week and the fetal skull, brain, spine, abdominal wall, limbs, stomach and bladder were examined. Following the scans the patientes were examined in the second or third trimester of pregnancy. An isolated increased nuchal translucency was not considered an abnormality. However, these patients had an early echocardiography assessment. Fetal structural abnormalities were classified as major or minor and of early or late onset. A total of 130 (4.6%) defects were identified and 29 (22.3%) of these were diagnosed at the 11–14 week scan, including nine cardiac defects associated with increased nuchal translucency. The antenatal ultrasound detection rate was 71.5%, and 31.2% were detected in the first-trimester assessment. 78.8% of the major defects were diagnosed by the prenatal scan and 37.8% by the 11–14 week scan. Fetal structural abnormalities at the 11–14 week scan were detected in approximately 22.3% of the cases, therefore, a second-trimester anomaly scan is important in routine antenatal care to increase the prenatal detection of fetal defects. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
457.
When Beckwith–Wiedemann syndrome (BWS) is detected prenatally, it is usually on the basis of macroglossia, exomphalos or enlarged kidneys. We describe a case that presented as gross hepatomegaly and a suspected enlarged pancreas at 20 weeks' gestation, with none of the usual features. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
458.
To isolate fetal cells from maternal blood, we developed a new method based on galactose-bearing conjugation. Nucleated red blood cells (NRBCs), which highly express galactose on their surface, were selectively attached to a substrate coated with a galactose-containing polymer via soybean agglutinin (SBA), a galactose-specific lectin. Cord blood samples were used to evaluate enrichment efficacy of NRBCs by this method. Blood samples were obtained from 131 pregnant women between 6 and 27 gestational weeks. After preliminary condensation of fetal cells by Ficoll gradient centrifugation, NRBCs were enriched using galactose-positive selection by adjusting SBA concentration. We isolated one to severalhundred NRBCs (mean±SD, 7.8±8.5) in 2.3 ml of peripheral blood samples from 96% of pregnantwomen. The isolated NRBCs were analyzed by a Y-chromosome FISH probe in eight cases carrying male fetuses. Y-signals were detected in all eight cases and more than half of the NRBCs wereoffetal origin. The study demonstrates that our new method using galactose-specific lectin provides effective enrichment of fetal NRBCs allowing non-invasive prenatal diagnosis. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
459.
460.
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