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   41922篇
  免费   397篇
  国内免费   313篇
安全科学   1177篇
废物处理   2266篇
环保管理   6022篇
综合类   5628篇
基础理论   11225篇
环境理论   12篇
污染及防治   9789篇
评价与监测   3287篇
社会与环境   3000篇
灾害及防治   226篇
  2023年   149篇
  2022年   275篇
  2021年   356篇
  2020年   221篇
  2019年   293篇
  2018年   1824篇
  2017年   1765篇
  2016年   1878篇
  2015年   711篇
  2014年   944篇
  2013年   2892篇
  2012年   1568篇
  2011年   2702篇
  2010年   1862篇
  2009年   1786篇
  2008年   2349篇
  2007年   2584篇
  2006年   1383篇
  2005年   1217篇
  2004年   1204篇
  2003年   1187篇
  2002年   1153篇
  2001年   1164篇
  2000年   867篇
  1999年   565篇
  1998年   432篇
  1997年   436篇
  1996年   450篇
  1995年   521篇
  1994年   444篇
  1993年   397篇
  1992年   434篇
  1991年   391篇
  1990年   364篇
  1989年   359篇
  1988年   318篇
  1987年   270篇
  1986年   284篇
  1985年   282篇
  1984年   313篇
  1983年   302篇
  1982年   300篇
  1981年   272篇
  1980年   207篇
  1979年   200篇
  1978年   183篇
  1977年   146篇
  1975年   149篇
  1973年   174篇
  1972年   146篇
排序方式: 共有10000条查询结果,搜索用时 655 毫秒
511.
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   
512.
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   
513.
We describe a patient with a significantly elevated serum alphafetoprotein (AFP) concentration at 17 weeks of gestation, who showed only a marginally increased amniotic fluid AFP and lacked the second rapidly migrating band of acetylcholinesterase electrophoresis. Ultrasound examination revealed an encephalocele and ventriculomegaly. Autopsy showed that the encephalocele was not covered by skin.  相似文献   
514.
We report herein a de novo unbalanced chromosome translocation in a fetus resulting from in vitro fertilization technology. Prenatal diagnostic analysis of an amniotic fluid revealed a 46,XX,4p+ karyotype. The origin of the extra material on the short arm of chromosome 4 could not be identified by a variety of banding techniques. However, examination of fetal parts did reveal some dysmorphic features.  相似文献   
515.
Reverse phase HPLC of radioactive globin chains has been compared to classical carboxy methyl cellulose chromatography for the prenatal diagnosis of β thalassaemia. The two methods correlated highly (r = 0.97 p < 0.0005) and provided an identical diagnosis for 40 fetal blood samples of fetuses homozygous or heterozygous for β thalassaemia. The HPLC procedure was much faster and required fewer biochemical steps (no globin preparation). It was at least as accurate and more sensitive than the classical chromatography. A single column can be used for 150 analyses and is always ready to be used. Last but not least it is much less expensive than CMC chromatography.  相似文献   
516.
517.
Mitigation and Adaptation Strategies for Global Change - In Mexico an estimated 4.5 × 106ha are available for farm forestry, while up to 6.1 × 106 ha could be saved from deforestation by...  相似文献   
518.
519.
520.
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