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   31919篇
  免费   351篇
  国内免费   460篇
安全科学   980篇
废物处理   1487篇
环保管理   3763篇
综合类   5651篇
基础理论   8213篇
环境理论   25篇
污染及防治   8449篇
评价与监测   2147篇
社会与环境   1835篇
灾害及防治   180篇
  2023年   138篇
  2022年   328篇
  2021年   330篇
  2020年   250篇
  2019年   299篇
  2018年   508篇
  2017年   507篇
  2016年   775篇
  2015年   597篇
  2014年   926篇
  2013年   2506篇
  2012年   1089篇
  2011年   1497篇
  2010年   1209篇
  2009年   1246篇
  2008年   1506篇
  2007年   1553篇
  2006年   1317篇
  2005年   1145篇
  2004年   1019篇
  2003年   1111篇
  2002年   981篇
  2001年   1274篇
  2000年   887篇
  1999年   538篇
  1998年   366篇
  1997年   376篇
  1996年   372篇
  1995年   440篇
  1994年   473篇
  1993年   364篇
  1992年   384篇
  1991年   365篇
  1990年   395篇
  1989年   351篇
  1988年   302篇
  1987年   283篇
  1986年   230篇
  1985年   257篇
  1984年   278篇
  1983年   264篇
  1982年   251篇
  1981年   237篇
  1980年   181篇
  1979年   201篇
  1978年   183篇
  1975年   149篇
  1974年   127篇
  1972年   138篇
  1971年   136篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
261.
Defense Mechanisms of Arthropods, no. 96; no. 95: Eisner et al.: Chemoecology (in press)  相似文献   
262.
263.
264.
265.
266.
The fetal gall bladder can now be easily identified during the second and third trimesters using high-resolution ultrasonography. In this report we present eight fetuses with an enlarged gall bladder detected on prenatal ultrasonography at a mean gestational age of 24.6 weeks (range 19–31 weeks). Additional ultrasonographic findings were present in four cases: fetal anomalies and intrauterine growth retardation in three and polyhydramnios in one. Of those cases associated with fetal anomalies, one woman underwent amniocentesis at 21 weeks revealing trisomy 18. The other two declined prenatal karyotyping; neonatal karyotyping revealed trisomy 13 in one and trisomy 18 in the other. Although an enlarged fetal gall bladder can be a normal variant in the second and third trimesters, the prenatal detection of cholecystomegaly should prompt a search for associated anomalies and other markers of aneuploidy. If found, prenatal karyotyping should be considered.  相似文献   
267.
Herlitz junctional epidermolysis bullosa (HJEB) is a severe blistering disorder which usually results in death during infancy. We have previously shown that the anchoring filament protein laminin-5 (kalinin/nicein), which mediates keratinocyte attachment and dermal–epidermal cohesion, is abnormally expressed in individuals with HJEB. Laminin-5 was detected by Western blot analysis in amniotic fluid from 44 consecutive normal secondtrimester control pregnancies, but was undetectable in second-trimester amniotic fluid from four pregnancies with fetuses affected by HJEB. In one case of severe non-Herlitz JEB, laminin-5 was detected in both amniotic fluid and skin. In human amniotic fluid, the laminin-5 a3 subunit was processed to a major 165 kD species and a minor 145 kD species and the β2 subunit was partially processed to 105 kD. Although laminin-5 was covalently associated with laminin-6 (K-laminin) in amniotic membrane, no covalent interaction was detected in amniotic fluid. Laminin-5 from amniotic fluid strongly supported keratinocyte attachment. These results suggest that Western blot analysis of second-trimester amniotic fluid is useful in determining the prenatal diagnosis of HJEB and that laminin-5 may serve a physiologically important function in amniotic fluid.  相似文献   
268.
Trisomy 10 was detected at amniocentesis undertaken following observation of fetal nuchal oedema. This is the first report of fetal trisomy 10 in association with nuchal oedema. The physical features of fetal trisomy 10 are described.  相似文献   
269.
A case of gastric outlet obstruction diagnosed prenatally at 22 weeks' gestation is described. The differential diagnosis and the clinical management of this rare condition are discussed, and an updated literature review is presented.  相似文献   
270.
Cytomegalovirus (CMV) is the most common cause of intrauterine infection. Recent publications show amniocentesis to have an 81–100 per cent sensitivity in antenatal diagnosis after 21 weeks' gestation. Testing before 21 weeks' gestation is less well documented. We performed 36 amniocenteses between 14 and 20 weeks' gestation. The sensitivity was 45 per cent and the specificity 100 per cent. Implications and possible causes of this low sensitivity are discussed.  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