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   505篇
  免费   11篇
  国内免费   9篇
安全科学   21篇
废物处理   13篇
环保管理   137篇
综合类   50篇
基础理论   94篇
污染及防治   132篇
评价与监测   46篇
社会与环境   21篇
灾害及防治   11篇
  2021年   6篇
  2020年   2篇
  2019年   5篇
  2018年   5篇
  2017年   6篇
  2016年   8篇
  2015年   14篇
  2014年   15篇
  2013年   65篇
  2012年   20篇
  2011年   22篇
  2010年   20篇
  2009年   17篇
  2008年   21篇
  2007年   27篇
  2006年   24篇
  2005年   20篇
  2004年   13篇
  2003年   19篇
  2002年   13篇
  2001年   9篇
  2000年   12篇
  1999年   8篇
  1998年   6篇
  1997年   5篇
  1996年   4篇
  1995年   9篇
  1994年   13篇
  1993年   9篇
  1992年   7篇
  1991年   8篇
  1990年   7篇
  1989年   4篇
  1988年   7篇
  1987年   4篇
  1986年   3篇
  1985年   2篇
  1984年   3篇
  1983年   9篇
  1982年   8篇
  1981年   8篇
  1980年   11篇
  1979年   8篇
  1978年   5篇
  1977年   3篇
  1976年   3篇
  1975年   2篇
  1973年   2篇
  1971年   1篇
  1968年   1篇
排序方式: 共有525条查询结果,搜索用时 0 毫秒
521.
Summary Juvenile female mice (Mus musculus) were exposed to the soiled bedding of unfamiliar males of different degrees of genetic relatedness. Females exposed to the soiled bedding of first cousins and unrelated males show an acceleration of first oestrus relative to controls. In contrast, females exposed to the soiled bedding of fathers or uncles show no such acceleration.  相似文献   
522.
The use of species distribution models (SDMs) to predict potential distributions of species is steadily increasing. A necessary assumption when projecting models throughout space or time is that climatic niches are conservative, but recent findings of niche shifts during biological invasion of particular plant and animal species have indicated that this assumption is not categorically valid. One reason for observed shifts may relate to variable selection for modelling. In this study, we assess differences in climatic niches in the native and invasive ranges of the Greenhouse frog (Eleutherodactylus planirostris). We analyze which variables are more ‘conserved’ in comparison to more ‘relaxed’ variables (i.e. subject to niche shift) and how they influence transferability of SDMs developed with Maxent on the basis of ten bioclimatic layers best describing the climatic requirements of the target species. We focus on degrees of niche similarity and conservatism using Schoener's index and Hellinger distance. Significance of results are tested with null models. Results indicate that the degrees of niche similarity and conservatism vary greatly among the predictive variables. Some shifts can be attributed to active habitat selection, whereas others apparently reflect variation in the availability of climate conditions or biotic interactions between the frogs' native and invasive ranges. Patterns suggesting active habitat selection also vary among variables. Our findings evoke considerable implications on the transferability of SDMs over space and time, which is strongly affected by the choice and number of predictors. The incorporation of ‘relaxed’ predictors not or only indirectly correlated with biologically meaningful predictors may lead to erroneous predictions when projecting SDMs. We recommend thorough assessments of invasive species' ecology for the identification biologically meaningful predictors facilitating transferability.  相似文献   
523.
Thermochemical biomass gasification, followed by conversion of the produced syngas to fuels and electrical power, is a promising energy alternative. Real-world characterization of particulate matter (PM) and other contaminants in the syngas is important to minimize damage and ensure efficient operation of the engines it powers and the fuels created from it. A dilution sampling system is demonstrated to quantify PM in syngas generated from two gasification plants utilizing different biomass feedstocks: a BioMax?15 Biopower System that uses raw and torrefied woodchips as feedstocks, and an integrated biorefinery (IBR) that uses rice hulls and woodchips as feedstocks. PM2.5 mass concentrations in syngas from the IBR downstream of the purification system were 12.8–13.7 μg·m−3, which were significantly lower than the maximum level for catalyst protection (500 μg·m−3) and were 2–3 orders of magnitude lower than those in BioMax?15 syngas (2247–4835 μg·m−3). Ultrafine particle number concentration and PM2.5 chemical constituents were also much lower in the IBR syngas than in the BioMax?15. The dilution sampling system enabled reliable measurements over a wide range of concentrations: the use of high sensitivity instruments allowed measurement at very low concentrations (∼1 μg·m−3), while the flexibility of dilution minimized sampling problems that are commonly encountered due to high levels of tars in raw syngas (∼1 g·m−3).  相似文献   
524.
Examples from previously published work by the lead author on the role of employee health indicators on individual and organizational outcomes provide an intriguing backdrop through the use of illustration for suggesting some of the many benefits obtained by the incorporation of replication, extension, and mixed‐methods study designs in organizational research. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
525.
Environmental and Ecological Statistics - After applying canonical correspondence analysis to metagenomics data with hugely different library sizes (site totals) it became evident that Canoco and...  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