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   24679篇
  免费   262篇
  国内免费   395篇
安全科学   645篇
废物处理   1069篇
环保管理   3259篇
综合类   3564篇
基础理论   6431篇
环境理论   4篇
污染及防治   6831篇
评价与监测   1661篇
社会与环境   1704篇
灾害及防治   168篇
  2023年   126篇
  2022年   246篇
  2021年   248篇
  2020年   157篇
  2019年   229篇
  2018年   372篇
  2017年   371篇
  2016年   581篇
  2015年   462篇
  2014年   715篇
  2013年   2144篇
  2012年   818篇
  2011年   1075篇
  2010年   872篇
  2009年   991篇
  2008年   1138篇
  2007年   1195篇
  2006年   1019篇
  2005年   878篇
  2004年   884篇
  2003年   845篇
  2002年   833篇
  2001年   1027篇
  2000年   730篇
  1999年   399篇
  1998年   309篇
  1997年   291篇
  1996年   358篇
  1995年   373篇
  1994年   325篇
  1993年   296篇
  1992年   273篇
  1991年   264篇
  1990年   272篇
  1989年   245篇
  1988年   237篇
  1987年   229篇
  1986年   187篇
  1985年   200篇
  1984年   227篇
  1983年   217篇
  1982年   216篇
  1981年   223篇
  1980年   175篇
  1979年   201篇
  1978年   133篇
  1977年   132篇
  1975年   122篇
  1973年   130篇
  1972年   142篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
401.
402.
403.
404.
405.
406.
407.
408.
A case of body stalk anomaly diagnosed prenatally by ultrasound during the 24th week of pregnancy in a cocaine abusing mother is presented. Accurate visualization of the fetal organs was difficult due to the severe oligohydramnios caused by premature rupture of membranes, probably related to the cocaine use. The sonographic findings were an omphalocoele, fetal attachment to the placenta, kyphoscoliosis, and absence of a floating umbilical cord. The prenatal diagnosis of the syndrome and the possible relationship with cocaine abuse are discussed.  相似文献   
409.
A case of fatal generalized dystrophic epidermolysis bullosa is described in a prematurely born female whose mother had strikingly elevated mid-trimester serum and amniotic fluid alpha-fetoprotein concentrations, a positive amniotic fluid acetylcholinesterase band, and negative serial ultrasound studies. This case lends further support to an association between autosomal recessive generalized dystrophic epidermolysis bullosa and increased levels of alpha-fetoprotein, positive amniotic fluid acetylcholines'terase, and normal ultrasound findings.  相似文献   
410.
Early arnniocentesis between 11 and 14 weeks' gestation was offered to 110 women at risk of a chromosomally abnormal fetus due to maternal age. Four were found to be unsuitable for the procedure, and 106 early amniocenteses were performed. In 102 cases, clear amniotic fluid was obtained with a single tap. There were two dry taps and two bloodstained tapis; sampling was repeated in three of these cases before 15 weeks. In the fourth case, placental biopsy was performed at 16 weeks. Thus, we were able to obtain a satisfactory sample in all but three cases(2.8 percent). Karyotyping of cells harvested from the early amniotic fluid samples was successful in all the 105 cases. Cell culture from the initial samples revealed a normal karyotype in 99 cases, two balanced translocations, two tetraploid karyotypes, and two cases of pseudomosaicism. Of the 105 pregnancies successfully sampled, there have been two losses to date (1–8 per cent). Two further patients presented with premature rupture of membranes, both pregnancies having successful outcomes. Sixty-two babies have delivered to date, with four congenital anomalies. There were no respiratory problems. Twenty-nine pregnancies are continuing without known complications, and details are not yet available on the remaining 12. The results indicate that early arnniocentesis may replace the traditional test at 15–17 weeks.  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