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   1019篇
  免费   17篇
  国内免费   20篇
安全科学   77篇
废物处理   31篇
环保管理   243篇
综合类   145篇
基础理论   289篇
环境理论   3篇
污染及防治   162篇
评价与监测   60篇
社会与环境   35篇
灾害及防治   11篇
  2023年   8篇
  2022年   11篇
  2021年   14篇
  2020年   13篇
  2019年   18篇
  2018年   15篇
  2017年   35篇
  2016年   38篇
  2015年   26篇
  2014年   29篇
  2013年   75篇
  2012年   41篇
  2011年   57篇
  2010年   34篇
  2009年   43篇
  2008年   61篇
  2007年   49篇
  2006年   59篇
  2005年   40篇
  2004年   28篇
  2003年   31篇
  2002年   35篇
  2001年   22篇
  2000年   23篇
  1999年   13篇
  1998年   17篇
  1997年   17篇
  1996年   14篇
  1995年   18篇
  1994年   13篇
  1993年   22篇
  1992年   9篇
  1991年   11篇
  1990年   6篇
  1989年   11篇
  1988年   12篇
  1987年   10篇
  1985年   9篇
  1984年   8篇
  1983年   6篇
  1982年   10篇
  1981年   10篇
  1980年   7篇
  1979年   8篇
  1978年   5篇
  1977年   2篇
  1975年   2篇
  1974年   2篇
  1973年   3篇
  1968年   2篇
排序方式: 共有1056条查询结果,搜索用时 31 毫秒
1.
2.
This paper demonstrates the potential for induced preference experiments to test previously unverified explanations of observed behavior in contingent valuation surveys. The NOAA Panel on Contingent Valuation called for experimental evidence on potential biases in the double referendum format. We test Carson, Groves, and Machina's (Incentives and informational properties of preference questions, Plenary address to the European Association of Resource and Environmental Economists, Oslo, Norway, June 1999) simple cost uncertainty and weighted averaging explanations of inconsistent responses to follow-up offers in such double referenda against a baseline of certainty and truthful preference revelation. The results find evidence to support the Weighted Average hypothesis. Results regarding the cost uncertainty hypothesis are more ambiguous and merit further investigation.  相似文献   
3.
The Countryside and Rights of Way Act 2000 places a duty on highways and national park authorities to establish local access forums (LAFs), to advise on the improvement of public access to land for the purposes of open air recreation and enjoyment. This paper examines these proposals in the context of recent academic and political debates about deliberative democracy, and empirical research on the nature and practice of existing access liaison groups and forums. While demonstrating that the proposed LAFs are consistent with contemporary constructs of participative, if not deliberative democracy, the paper argues that most existing groups and forums fall short of this ideal, in a number of significant respects. The paper proceeds to discuss the extent to which the draft regulations for LAFs in England and Wales address these issues, and concludes by questioning the extent to which such consultative arrangements can contribute to new forms of local governance.  相似文献   
4.
5.
6.
7.
The objective of this study was to determine filter materials and extraction methods that are appropriate to use for environmental sampling of B. anthracis. Four types of filters were tested: mixed cellulose ester (MCE) with a pore size of 3 microm, polytetrafluoroethylene (PTFE) with pore sizes of 1 and 3 microm, and gelatin with a pore size of 3 microm. Bacillus subtilis var. niger endospores (also known as Bacillus globigii[BG]) were used as a surrogate for B. anthracis. Endospores were collected into Button Inhalable Aerosol Samplers with sampling times of 15 minutes, 1 hour, and 4 hours. Physical collection efficiency was determined by measuring upstream and downstream B. subtilis concentrations with an optical particle counter. Vortexing with ultrasonic agitation and vortexing with shaker agitation extraction methods were evaluated. The MCE, 1 microm PTFE, and gelatin filters provided physical collection efficiencies of 94% or greater. The 3 microm PTFE filter showed inconsistent physical efficiency characteristics between filters. Epifluorescence microscopic analysis of the gelatin filter extraction fluid revealed the presence of contamination by non-culturable bacteria. Mean differences for microbial culturability were not statistically significant for filter materials and extraction methods. However, the vortexing with shaker agitation extraction method resulted in higher total microbial counts in the extraction fluids for MCE and 1 microm PTFE filters when compared to vortexing with ultrasonic agitation. In summary, the MCE and 1 microm PTFE filters in combination with vortexing and shaker extraction demonstrated the best performance for the filter collection and extraction of BG spores.  相似文献   
8.
Mercury is released to the environment from various anthropogenic and natural sources. This work is a compilation of mercury emissions from anthropogenic sources in Ontario, Canada. The goal of our study was to identify all sources of mercury, and develop an emission inventory of anthropogenic mercury in Ontario. The result of our investigation revealed that combustion of fossil fuels and emissions from landfill sites are two primary sources of mercury to the atmosphere. Other sources of significance are emissions from waste incinerators, various industrial activities, and cement production. Total mercury emission in Ontario is estimated as 4100 kg per year.  相似文献   
9.
Chorionic villus sampling (CVS) with either transcervical catheters or transabdominal needles is a widely-accepted method for prenatal diagnosis. However, there exists a small subset of patients in whom sampling is difficult or impossible with either route because of individual anatomic variations. A new method of chorionic villus biopsy has been developed to circumvent these problems, utilizing transvaginal chorionic needle aspiration guided by an intravaginal ultrasound probe. This technique was performed successfully in 15 patients in whom villi could not be obtained by either of the conventional methods. This method now makes CVS possible in essentially all women regardless of their uterine anatomy or placental placement; it may also prove useful for very early chorionic sampling.  相似文献   
10.
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