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   32462篇
  免费   309篇
  国内免费   268篇
安全科学   845篇
废物处理   1381篇
环保管理   4172篇
综合类   5753篇
基础理论   8073篇
环境理论   11篇
污染及防治   8744篇
评价与监测   2105篇
社会与环境   1791篇
灾害及防治   164篇
  2022年   265篇
  2021年   284篇
  2019年   255篇
  2018年   455篇
  2017年   460篇
  2016年   736篇
  2015年   577篇
  2014年   861篇
  2013年   2548篇
  2012年   1020篇
  2011年   1372篇
  2010年   1052篇
  2009年   1200篇
  2008年   1398篇
  2007年   1486篇
  2006年   1309篇
  2005年   1078篇
  2004年   1090篇
  2003年   1054篇
  2002年   1014篇
  2001年   1249篇
  2000年   857篇
  1999年   553篇
  1998年   392篇
  1997年   396篇
  1996年   446篇
  1995年   458篇
  1994年   450篇
  1993年   412篇
  1992年   370篇
  1991年   365篇
  1990年   374篇
  1989年   329篇
  1988年   329篇
  1987年   301篇
  1986年   274篇
  1985年   279篇
  1984年   318篇
  1983年   317篇
  1982年   309篇
  1981年   295篇
  1980年   256篇
  1979年   267篇
  1978年   223篇
  1977年   199篇
  1976年   180篇
  1975年   186篇
  1974年   175篇
  1973年   174篇
  1972年   174篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
541.
542.
This research was supported by a grant from the National Council for Research and Development, Israel, and the KFK, Karlsruhe, Germany.  相似文献   
543.
Cysts of the choroid plexus of the lateral ventricle can be detected in the fetus during routine scanning at 16–18 weeks' gestation with an approximate incident of one in every 120 pregnancies. It is likely that in a high percentage of cases cysts are bilateral and that their recent discovery is mainly due to improvements in imaging technology. Although the great majority of cases resolve and do not result in any morbidity, five cases of trisomy 18 and one case of trisomy 21 associated with fetal choroid plexus cysts have been reported. In this prospective study, choroid plexus cysts were detected in 42 fetuses, resulting in 40 normal infants and 2 cases of trisomy 18. It is concluded that there may be a relationship between fetal choroid plexus cysts and trisomy 18. In order to obtain a more precise and accurate result, a multi-centre prospective study is being organized.  相似文献   
544.
A technique is described for measuring pressure within the amniotic cavity and within fetal vessels and/or body compartments. Two saline-filled catheters were connected at one end to needles inserted during indicated invasive procedures and at the other to silicon strain gauge transducers. In 36 pregnancies with normal liquor volume, stable intra-amniotic pressure (IAP, range 1–14 mmHg) increased with gestation (r=0·48, p<0·01). In pregnancies complicated by severe oligohydramnios, IAP was ≤ 1 mm Hg and rose to normal levels with saline amnioinfusion. Raised IAP (range 17–26 mm Hg), found in pregnancies with gross polyhydramnios, fell with drainage of amniotic fluid. Subtraction manometry was used to determine supra-amniotic pressure within the intervillus space, umbilical vein, umbilical artery, abdominal and thoracic cavities, and the urinary tract in normal and/or pathological fetuses. Low intravesical and intrapelvicalyceal pressures (median 6·5, range 2–10 mmHg) were noted in fetuses with obstructive uropathies. Intrauterine subtraction manometry appears to be a useful tool in the understanding of fetal pathophysiology and may be of clinical benefit in the therapeutic drainage and infusion of amniotic fluid and in the assessment of certain fetal disease states.  相似文献   
545.
This work was supported by DFG SFB 0207, project G 6.  相似文献   
546.
Dedicated to Professor H. J. Berthold, Hannover, on the occasion of his 65th birthday.  相似文献   
547.
A syncytiotrophoblast-associated antigen identified by the monoclonal antibody (McAb) H315 is detectable on the surface of a low proportion of peripheral blood cells in pregnant women, raising the possibility of a new approach to prenatal diagnosis of genetic disorders. We aimed at verifying the trophoblastic origin of H315+ cells and their use for prenatal diagnosis of β-thalassaemia. H315 + cells were separated from the peripheral blood of pregnant women: the DNA obtained from these cells in two selected cases was shown to have genetic markers indistinguishable from those of the mother and definitely different from the fetus. Our results suggest that H315 antigen is expressed by maternal cells and that prenatal diagnosis on peripheral blood of the mother using H315 McAb is not feasible.  相似文献   
548.
549.
550.
A de novo paracentric inversion of chromosome 11 identified through antenatal diagnosis is described along with long-term follow-up information on the child and discussion of reported experiences with de novo inversions.  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