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   31671篇
  免费   343篇
  国内免费   253篇
安全科学   1038篇
废物处理   1509篇
环保管理   4050篇
综合类   5180篇
基础理论   8098篇
环境理论   15篇
污染及防治   7878篇
评价与监测   2205篇
社会与环境   2112篇
灾害及防治   182篇
  2023年   147篇
  2022年   271篇
  2021年   335篇
  2020年   209篇
  2019年   258篇
  2018年   472篇
  2017年   495篇
  2016年   761篇
  2015年   567篇
  2014年   899篇
  2013年   2558篇
  2012年   1054篇
  2011年   1425篇
  2010年   1156篇
  2009年   1201篇
  2008年   1485篇
  2007年   1412篇
  2006年   1274篇
  2005年   1144篇
  2004年   1081篇
  2003年   1043篇
  2002年   975篇
  2001年   1146篇
  2000年   808篇
  1999年   509篇
  1998年   382篇
  1997年   404篇
  1996年   411篇
  1995年   478篇
  1994年   428篇
  1993年   356篇
  1992年   390篇
  1991年   375篇
  1990年   338篇
  1989年   335篇
  1988年   302篇
  1987年   249篇
  1986年   256篇
  1985年   257篇
  1984年   283篇
  1983年   265篇
  1982年   281篇
  1981年   239篇
  1980年   174篇
  1979年   191篇
  1978年   168篇
  1977年   143篇
  1975年   147篇
  1973年   176篇
  1972年   152篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
103.
 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   
104.
105.
106.
Fetal aspartylglucosaminuria (AGU) was studied during the first trimester of pregnancy in six at-risk pregnancies using chorionic villus samples. The activity of aspartylglucosaminidase (AGA) was high in five cases, indicating an unaffected fetus. This was confirmed through delivery of healthy newborns with a normal pattern of urinary oligosaccharides. Low enzyme activity in an uncultured biopsy specimen and in cultured amniotic fluid cells in one case demonstrated that the fetus was affected. The pregnancy was terminated and the prenatal diagnosis was confirmed by showing reduced AGA activity in cultured fibroblasts of the fetus.  相似文献   
107.
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   
108.
109.
Long-term copper smelting in the Anaconda and Deer Lodge Valley area of Montana has resulted in an extensive area of trace element contamination. Aerial extent of contamination is generally established, but total analysis of soils does not correlate to relative degree of impact on vegetation growth. Three pedons (Beaverell, Cetrack and Judco) were analyzed by routine soil characterization methods, aqua regia microwave digestion, sequential chemical extraction, and X-ray diffraction analysis with the objective of providing a better understanding of chemical forms and potential reactivity of selected trace elements (Cd, Co, Cr, Cu, Hg, Mn, Ni, P, Pb). Surface horizons of soils are more acidic than subsoils, with pH for all horizons ranging from 4.0 to 8.7. Beaverell is the most contaminated in the upper 20 cm with the sum of total extractable (SUMTE) trace elements by microwave digestion ranging from 1836 to 3605 mg kg−1, largest H2O-soluble (WS) and exchangeable (EX) fractions (e.g. 1.6 and 9.3%, respectively), and smallest residual (RES) fraction (e.g. 14.3%). Cetrack has greater SUMTE elements than Judco, though a lower WS+EX fraction due to the effects of alkaline pH, carbonates and high P. Oxide (OX), organic matter/sulfide (OM/S), and RES fractions predominate over WS, EX, and specially-sorbed/carbonate-bound fractions (SS/CAR) for all horizons. Copper, Zn, Pb and Cd are elevated in surface over subsurface horizons in these latter fractions, indicating these elements were anthropogenic additions. X-ray data indicate that Pb, Cu, Cr and Cd partially exists as both OX and sulfide mineral forms.  相似文献   
110.
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