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   4834篇
  免费   44篇
  国内免费   55篇
安全科学   131篇
废物处理   283篇
环保管理   401篇
综合类   777篇
基础理论   968篇
环境理论   4篇
污染及防治   1569篇
评价与监测   456篇
社会与环境   306篇
灾害及防治   38篇
  2023年   48篇
  2022年   158篇
  2021年   171篇
  2020年   93篇
  2019年   95篇
  2018年   181篇
  2017年   174篇
  2016年   243篇
  2015年   155篇
  2014年   230篇
  2013年   373篇
  2012年   262篇
  2011年   333篇
  2010年   234篇
  2009年   197篇
  2008年   233篇
  2007年   240篇
  2006年   165篇
  2005年   182篇
  2004年   223篇
  2003年   207篇
  2002年   144篇
  2001年   105篇
  2000年   61篇
  1999年   50篇
  1998年   26篇
  1997年   29篇
  1996年   24篇
  1995年   32篇
  1994年   27篇
  1993年   14篇
  1992年   19篇
  1991年   17篇
  1990年   14篇
  1989年   12篇
  1988年   7篇
  1987年   11篇
  1986年   10篇
  1985年   11篇
  1984年   12篇
  1983年   12篇
  1982年   7篇
  1981年   10篇
  1979年   10篇
  1975年   4篇
  1967年   3篇
  1966年   3篇
  1964年   5篇
  1961年   3篇
  1958年   3篇
排序方式: 共有4933条查询结果,搜索用时 15 毫秒
41.
Hybridization between Aegilops geniculata, A. biuncialis and bread wheat Triticum aestivum has been evaluated during two seasons under simulated field conditions to estimate the field hybridization rate under Central Spain conditions. The mean frequencies of hybridization between A. biuncialis and A. geniculata with wheat were 0.34% and 0.31%, respectively. Data from 10 hybrid plants for each combination showed that hybrids can be partially fertile by backcrossing with wheat parent, with percent averages of 3.17 grains/spikelets for A. biuncialis × wheat hybrids and 2.87 grains/spikelets for A. geniculata × wheat hybrids. Self-pollination, although at very low rates, was also possible in hybrids. The potential risks associated with natural hybridization in the context of transgenic wheat cultivation are discussed.  相似文献   
42.
This paper examines how legal standards of liability may apply to geologic carbon storage. The liability regime governing geologic carbon storage will shape the technology's cost-effectiveness and overall attractiveness. We classify potential sources of liability into operational, in situ, and climate liability. As a first step, we explore in situ liability in the United States. After summarizing legal standards of liability including negligence, breach of implied warranty, strict liability, and product liability, we discuss how liability may be addressed at the level of the federal government, state government, industry, and the firm. Finally, we address the implications of judicial treatment of liability for carbon storage, including the apportionment of liability and the adequacy of current regulations.  相似文献   
43.
The Science of Nature - Because of the sudden rise in primary-energy costs and the rapid inflation of plants which are used for the conversion of primary to secondary energy, the storage of energy,...  相似文献   
44.
45.
46.
Two types of fermented organic waste (trade and industry waste and fruit and vegetable waste) were successfully used as a sole carbon source to produce poly-3-hydroxybutyrate-co-valerate (PHBV) by Ralstonia eutrophus (formerly Alcaligenes eutrophus) via oxygen limitation.The production of PHBV could be optimized by optimizing the oxygen transfer through the fermentor. Thereby, a peak concentration of 1.1 g PHBV per liter cell suspension, 40 w% of cell dry weight, was obtained at an aeration rate of 0.24 mol O2/h·kg biomass. The yield of PHBV on the fatty acid concentration in the organic waste was 0.16 g polymer/g volatile organic matter. The process obtained, compares well with the commercial production process of PHBV based on glucose.  相似文献   
47.
In a case of hydrops fetalis, serological examination showed a recent maternal human parvovirus B19 infection. Amniocentesis revealed a unique unbalanced translocation between chromosomes 3 and 11 of the fetus. The mother proved to have a balanced reciprocal translocation between chromosomes 3 and 11. A grossly macerated hydropic male fetus was delivered with a flat nose and low implanted deformed ears. Histopathological examination revealed nuclear inclusion bodies in fetal erythroid cells, confirming human parvovirus B19 infection. Parvovirus B19 DNA was demonstrated by in situ hybridization in the nuclei of heart muscle cells. Our finding of two different disorders in one case illustrates the importance of a complete evaluation of every case of hydrops fetalis, especially concerning counselling on the outcome of future pregnancies. The human parvovirus B19 infection will not recur due to the acquired immunity of the mother, whereas the balanced reciprocal translocation will endanger future pregnancies.  相似文献   
48.
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   
49.
50.
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