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   514篇
  免费   17篇
  国内免费   104篇
安全科学   27篇
废物处理   19篇
环保管理   9篇
综合类   489篇
基础理论   10篇
污染及防治   77篇
评价与监测   4篇
  2023年   1篇
  2022年   4篇
  2021年   7篇
  2020年   4篇
  2019年   3篇
  2018年   5篇
  2017年   8篇
  2016年   12篇
  2015年   15篇
  2014年   13篇
  2013年   14篇
  2012年   28篇
  2011年   57篇
  2010年   50篇
  2009年   57篇
  2008年   42篇
  2007年   42篇
  2006年   47篇
  2005年   38篇
  2004年   36篇
  2003年   27篇
  2002年   39篇
  2001年   24篇
  2000年   1篇
  1999年   1篇
  1998年   2篇
  1997年   2篇
  1995年   15篇
  1994年   15篇
  1993年   3篇
  1992年   1篇
  1991年   3篇
  1990年   4篇
  1989年   1篇
  1988年   3篇
  1987年   5篇
  1985年   2篇
  1984年   1篇
  1983年   2篇
  1982年   1篇
排序方式: 共有635条查询结果,搜索用时 437 毫秒
331.
332.
333.
334.
335.
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   
336.
337.
338.
339.
This article presents the methods and results of visual interpretation of NOAA AVHRR imagery for mapping flood areas in Bangladesh. Color composites of channels 1 and 2 for 18 August 1987 and 10, 15, and 24 September 1988 were interpreted visually for delineating flood boundaries. On such imagery flood areas appear in dark tones and are separated from land (light tones) owing to the absorption of near infrared by water and its reflectance by land and non-waterbodies. Visual interpretation was aided by the use of ground information, such as physiographic and river maps, previous flood maps, newspaper reports, and other published and unpublished documents on the 1987 and 1988 floods. Interpreted flood areas on selected images ranged from 31% to 43% of the total area of Bangladesh. Visual interpretation overestimated flood areas by 5%–10%, compared to the digitally analyzed data. The main advantage of visual analysis lies in the cost effectiveness of AVHRR photographic products, which make them more accessible than the digital image analysis of computer-compatible tapes.  相似文献   
340.
In utero diagnosis of de novo distal 11q deletion associated with renal and orofacial malformations has not been previously described. We present a 35-year-old pregnant woman with prenatal sonographic findings of a unilateral duplex renal system, pyelectasis and orofacial clefts at 20 weeks' gestation. Both genetic amniocentesis and postnatal cytogenetic analysis revealed de novo 46,XX,del(11)(q23). After birth, the fetus manifested a dysmorphic phenotype correlated with del(11q) syndrome. Genetic marker analysis showed a paternally derived distal deletion of chromosome 11q and a breakpoint centromeric to D11S1341. The present case represents the earliest prenatal diagnosis of a duplex renal system, pyelectasis and an additional feature of orofacial clefts associated with distal 11q deletion. Prenatal sonographic detection of a duplex renal system, pyelectasis and orofacial clefts should warrant a careful assessment of fetal anatomy and prompt cytogenetic analysis looking for chromosomal aberrations. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   
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