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   35261篇
  免费   391篇
  国内免费   454篇
安全科学   952篇
废物处理   1351篇
环保管理   4709篇
综合类   5648篇
基础理论   9943篇
环境理论   21篇
污染及防治   9019篇
评价与监测   2191篇
社会与环境   2044篇
灾害及防治   228篇
  2022年   294篇
  2021年   266篇
  2020年   212篇
  2019年   290篇
  2018年   502篇
  2017年   497篇
  2016年   726篇
  2015年   601篇
  2014年   850篇
  2013年   2665篇
  2012年   1061篇
  2011年   1527篇
  2010年   1245篇
  2009年   1293篇
  2008年   1525篇
  2007年   1612篇
  2006年   1398篇
  2005年   1219篇
  2004年   1190篇
  2003年   1138篇
  2002年   1126篇
  2001年   1473篇
  2000年   1023篇
  1999年   623篇
  1998年   490篇
  1997年   490篇
  1996年   522篇
  1995年   559篇
  1994年   490篇
  1993年   450篇
  1992年   467篇
  1991年   434篇
  1990年   425篇
  1989年   447篇
  1988年   384篇
  1987年   350篇
  1986年   308篇
  1985年   344篇
  1984年   329篇
  1983年   363篇
  1982年   374篇
  1981年   315篇
  1980年   281篇
  1979年   302篇
  1978年   257篇
  1977年   223篇
  1976年   223篇
  1975年   215篇
  1973年   205篇
  1972年   234篇
排序方式: 共有10000条查询结果,搜索用时 765 毫秒
541.
542.
One hundred and fifty-one women of advanced maternal age who underwent genetic termination of pregnancy (TOP) were studied for their reproductive behaviour and the type of procedure for prenatal diagnosis in a subsequent pregnancy. A total of 59 women (39 per cent) had a further pregnancy. In all continuing pregnancies prenatal diagnosis was performed, of which 75 per cent consisted of chorionic villus sampling (CVS). Reproductive behaviour following a genetic termination was negatively correlated with maternal age and parity. Both reproductive behaviour and the choice to undergo a diagnostic procedure in the next pregnancy were independent of the type of diagnostic procedure in the previous affected pregnancy.  相似文献   
543.
544.
545.
546.
547.
548.
Ninety-two families with spinal muscular atrophy (SMA) applied for genetic counselling and further prenatal diagnosis. To minimize expenses, only one tightly linked informative marker was determined in the course of preliminary examination, and non-radioactive allele detection was preferably used. Four prenatal diagnoses of SMA type I, four of SMA type II, and one of SMA type III were made. This trial programme shows the considerable requirements, importance, and potential effectiveness of prenatal prediction of SMA in Russia.  相似文献   
549.
We report two cases of apparently balanced complex de novo chromosomal rearrangements (BCCR) detected prenatally at 17 weeks and 10 weeks of gestation, respectively. Chromosomes were studied using GTG-banding and fluorescent in situ hybridization (FISH). In one case four chromosomes and in the other case three chromosomes were involved in the rearrangements. One of the pregnancies was terminated and no external or internal abnormalities were detected at autopsy. The other pregnancy continued to term. Level III ultrasound examination showed no abnormalities. The child is now 3 years old and has neither congenital anomalies nor evidence of delayed psychomotor development.  相似文献   
550.
A prenatally detected case of a rare mosaic tetrasomy 12p/trisomy 12p is reported, presenting as the well-known accessory isochromosome 12p and a supernumerary single 12p marker in 17/24 and 6/24 clones of cultured amniotic fluid cells, respectively. The chromosomal nature of both marker chromosomes was investigated in cultured amniotic fluid cells by fluorescent in situ hybridization with various probes: the 12-centromeric probes pa12H8 and D12Z3, a whole chromosome 12 paint, and the chromosome 12p-specific paint M28. DNA analysis revealed a maternal origin of the extra 12p material. After counselling, the parents requested termination of pregnancy. Inspection and autopsy of the fetus revealed many of the dysmorphisms and internal structural abnormalities of the Pallister–Killian syndrome.  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