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   30091篇
  免费   327篇
  国内免费   230篇
安全科学   847篇
废物处理   1091篇
环保管理   4102篇
综合类   4775篇
基础理论   8612篇
环境理论   21篇
污染及防治   7933篇
评价与监测   1800篇
社会与环境   1273篇
灾害及防治   194篇
  2022年   199篇
  2021年   193篇
  2019年   221篇
  2018年   405篇
  2017年   401篇
  2016年   580篇
  2015年   508篇
  2014年   716篇
  2013年   2204篇
  2012年   888篇
  2011年   1300篇
  2010年   1051篇
  2009年   1064篇
  2008年   1290篇
  2007年   1359篇
  2006年   1213篇
  2005年   1037篇
  2004年   1022篇
  2003年   952篇
  2002年   947篇
  2001年   1244篇
  2000年   863篇
  1999年   550篇
  1998年   430篇
  1997年   438篇
  1996年   446篇
  1995年   484篇
  1994年   442篇
  1993年   397篇
  1992年   416篇
  1991年   374篇
  1990年   378篇
  1989年   412篇
  1988年   350篇
  1987年   300篇
  1986年   278篇
  1985年   305篇
  1984年   286篇
  1983年   321篇
  1982年   323篇
  1981年   271篇
  1980年   243篇
  1979年   269篇
  1978年   230篇
  1977年   195篇
  1976年   200篇
  1975年   192篇
  1974年   172篇
  1973年   172篇
  1972年   198篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
 The “Linh Duong” (Pseudonovibos spiralis), a newly described Vietnamese bovid, has been shown to be related to the Caprinae on the basis of the mitochondrial cytochrome b gene sequencing from horn fragments. To integrate the greatest available biodiversity we performed a new phylogenetic analysis including all genera of Caprinae. Unexpectedly, Pseudonovibos is found to be robustly associated with Rupicapra, and closer to the Alpine than to the Pyrenean chamois. Several clues led us to interpret this result as a carry-over DNA contamination of Pseudonovibos by Rupicapra. Received: 19 July 1999 / Accepted in revised form: 20 October 1999  相似文献   
172.
173.
174.
A 17-year-old woman was referred for amniocentesis due to a low maternal serum alpha-fetoprotein (AFP) concentration in a voluntary screening test. The fetal karyotype was 48,XXYY, and the pregnancy was terminated. Autopsy of the fetus disclosed agenesis of the corpus callosum and unusual facial features.  相似文献   
175.
176.
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   
177.
178.
The diagnosis of Freeman–Sheldon syndrome was made by ultrasonographic evaluation of a 20-week fetus with a positive family history. The ultrasonographic features were abnormalities of the extremities and mouth.  相似文献   
179.
No clear answer concerning whether multivitamin/folate supplementation prevents neural tube defects (NTDs) is provided by three studies in the United States. All these studies are occurrence in nature, no recurrence studies having been conducted. The Atlanta Birth Defects Study is subject to pronounced memory and recall biases, the length between event and interview being as long as 16 years. In a second study (Boston University), objections can be raised to certain aspects of the experimental design, and the claim that 22 per cent of women started vitamins sufficiently early after pregnancy diagnosis to influence NTD formation is suspicious. Our NICHD case control study of 541 women in California and Illinois revealed no evidence for multivitamins or folic acid preventing NTDs. U.S. public policy-makers face difficulties in applying results of recurrence or occurrence studies in high-risk areas to low-risk areas in the U.S.  相似文献   
180.
With the advent of more stringent controls on wastewater treatment, sewage sludge production in Europe and many parts of the world is increasing. With this increase comes the problem of sludge disposal, and recycling to land arguably offers an economically and environmentally sustainable option. However, a major limitation of sewage sludge reuse is the potential release of heavy metals from the sludge and heavy metal accumulation to toxic levels in topsoils. The properties of the sludge play a crucial role in determining the initial release and subsequent availability of heavy metals in amended soils. Bioavailable forms of heavy metals in recently amended soils are most likely to be those that are bioavailable in the sewage sludge. In this paper, published research on the importance of sewage sludge characteristics on metal release and bioavailability will be reviewed and contrasted with original research. A selection of sludges from around Australia has been collected for this purpose. Through the use of incubation studies, isotope dilution techniques, ion-selective electrode measurements and 13C-NMR spectroscopy, the importance of a range of sludge properties on heavy metal behaviour in sludges and sludge-amended soils is addressed.  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