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   5033篇
  免费   91篇
  国内免费   48篇
安全科学   169篇
废物处理   169篇
环保管理   899篇
综合类   805篇
基础理论   1286篇
环境理论   13篇
污染及防治   1234篇
评价与监测   320篇
社会与环境   225篇
灾害及防治   52篇
  2023年   30篇
  2022年   36篇
  2021年   62篇
  2020年   42篇
  2019年   55篇
  2018年   113篇
  2017年   119篇
  2016年   125篇
  2015年   125篇
  2014年   144篇
  2013年   367篇
  2012年   228篇
  2011年   308篇
  2010年   222篇
  2009年   250篇
  2008年   265篇
  2007年   312篇
  2006年   286篇
  2005年   219篇
  2004年   177篇
  2003年   166篇
  2002年   191篇
  2001年   98篇
  2000年   85篇
  1999年   67篇
  1998年   68篇
  1997年   79篇
  1996年   61篇
  1995年   75篇
  1994年   71篇
  1993年   42篇
  1992年   47篇
  1991年   37篇
  1990年   34篇
  1989年   22篇
  1988年   31篇
  1987年   26篇
  1986年   34篇
  1985年   22篇
  1984年   27篇
  1983年   31篇
  1982年   28篇
  1981年   25篇
  1980年   25篇
  1979年   30篇
  1978年   20篇
  1977年   15篇
  1974年   13篇
  1965年   14篇
  1957年   13篇
排序方式: 共有5172条查询结果,搜索用时 872 毫秒
51.
52.
53.
54.
55.
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   
56.
57.
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   
58.
Decision tree, one of the data mining approaches, was used to model the relative abundance of five functional groups of plant species, namely high fertility response grasses (HFRG), low fertility tolerance grasses (LFTG), legume, moss and flatweeds in a New Zealand hill-pasture ecosystem using aboveground biomass. The model outputs were integrated with a geographic information system (GIS) to map and validate the predictions on a pasture. The decision tree models clearly revealed the interactions between the functional groups and environmental and management factors, and also indicated the relative importance of these factors in influencing the functional group abundance. Soil Olsen P was the most significant factor influencing the abundance of LFTG and moss, while soil bulk density, slope and annual P fertiliser input were the most significant factors influencing the abundance of legume, HFRG and flatweeds, respectively. Generally, slope and soil Olsen P were the two key factors underlying the patterns of abundance for these five functional groups. For the five functional groups studied, there was an overall predictive accuracy of 75%. Modelling functional group abundance simplified the investigation of the complex interrelationship between species and environment in a pasture ecosystem. The integration of the decision tree with GIS in this study provides a platform to investigate community structure and functional composition for a pasture over space, and thus can be applied as a tool in pasture management.  相似文献   
59.
60.
Although amphibians are highly vocal, they generally emit only a limited number of acoustic communication signals. We report here the extraordinarily rich vocal repertoire of Amolops tormotus, a ranid species in China. These frogs produce countless vocalizations, some of which share features of birdsong or primate calls, e.g., ultrasonic frequency components, multiple upward and downward FM sweeps, and sudden onset and offset of selective harmonic components within a call note. Frame-by-frame video analysis of the frog's calling behavior suggests the presence of two pairs of vocal sacs that may contribute to the remarkable call-note complexity in this species. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00114-002-0335-x.  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