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   1789篇
  免费   56篇
  国内免费   20篇
安全科学   88篇
废物处理   70篇
环保管理   406篇
综合类   174篇
基础理论   506篇
环境理论   5篇
污染及防治   416篇
评价与监测   122篇
社会与环境   53篇
灾害及防治   25篇
  2023年   18篇
  2022年   35篇
  2021年   47篇
  2020年   24篇
  2019年   42篇
  2018年   53篇
  2017年   59篇
  2016年   78篇
  2015年   49篇
  2014年   66篇
  2013年   151篇
  2012年   84篇
  2011年   127篇
  2010年   79篇
  2009年   94篇
  2008年   105篇
  2007年   97篇
  2006年   104篇
  2005年   54篇
  2004年   50篇
  2003年   59篇
  2002年   45篇
  2001年   26篇
  2000年   44篇
  1999年   20篇
  1998年   19篇
  1997年   9篇
  1996年   21篇
  1995年   18篇
  1994年   20篇
  1993年   10篇
  1992年   11篇
  1991年   9篇
  1990年   8篇
  1989年   12篇
  1988年   11篇
  1987年   10篇
  1986年   11篇
  1985年   9篇
  1984年   5篇
  1983年   10篇
  1982年   13篇
  1981年   14篇
  1980年   4篇
  1979年   5篇
  1978年   6篇
  1977年   4篇
  1975年   4篇
  1969年   4篇
  1958年   2篇
排序方式: 共有1865条查询结果,搜索用时 781 毫秒
81.
Planning considerations to be evaluated early in the design of water quality monitoring programs are reviewed. These criteria emphasize the importance of isolating the study area, parameter section, and type of measurements required to ensure meaningful results. A demonstration automatic water quality monitoring program is described. Details with respect to type of equipment, coordination of component parts, sampling program, and analysis of specific parameters are reviewed. General costs of implementation and maintenance of such programs are presented.  相似文献   
82.
To the USSR resource depletion is not a threat to be taken seriously on a world-wide basis but rather a manifestation of capitalism. Shortages caused by the system will aggravate the contradictions inherent in capitalism and hasten its downfall. The socialist world avoids resource crises by planning its economies. The author examines here the ideological basis of views held on the resources question in the USSR and the role resources planning will play in the eventual triumph of socialism.  相似文献   
83.
ABSTRACT: The applicability of the U.S Environmental Protection Agency's (USEPA) water temperature criteria in evaluating the impact of a thermal discharge from the P. H. Glatfelter Paper Company, Spring Grove, Pennsylvania, is analyzed. A review of the literature relative to 11 temperature Criteria was conducted for six fish species designated by the USEPA as “representative important species” (RIS) of the West Branch Codorus Creek, Susquehanna River drainage. The species were: Notemigonus crysolcucas (golden shiner), Notropis analostanus (satinfin shiner), Rhinichthys atratulus (blacknose dace), Catostomus comme-soni (white sucker), Lepomis gibbosus (pumpkinseed). and Micropterous salmoides (largemouth bass). It was found that by applying only USEPA suggested criteria that a complete evaluation was not satisfactory. Temperature behavior data, specifically preference and avoidance information, coupled with field sampliug was needed to properly assess the effects of the thermal effluent. The final analysis indicated that the thermal discharge of the paper company should have minimal effect on the fish community of Codorus Creek.  相似文献   
84.
ABSTRACT: Deep percolation rates are normally estimated from a water balance. Results are presented of a study undertaken to evaluate three alternative methods of estimating percolation below the root zone when knowledge about the history of applied water and evapotranspiration are not available. The alternative methods are: 1) use of Darcy's equation to calculate deep percolation rate; 2) measurement of the soil temperature prof and calculation of the deep percolation rate from the shape of the temperature depth curve; and 3) measurement of the tritium concentration in the soil water and its relationship to the history of the tritium concentration in rainfall. At the principal study site, the Darcy velocity of flow ranged from 9 cm per year determined by the temperature method, to 40 cm per year determined by the tritium method. Darcy's equation to calculate seepage rates resulted in an estimation of deep seepage of 18 cm per year. An average deep percolation rate at the principal study site of 22 cm per year was determined using the average of all three methods. Results for other sites based on the temperature method indicated a lower seepage rate.  相似文献   
85.
There is inconsistency in many people's choice of electricity. When asked, they say they prefer a ‘green’ (i.e., environmentally friendly) source for this energy. Yet, although green electricity is available in many markets, people do not generally buy it. Why not? Motivated by behavioural decision research, we argue that the format of information presentation drastically affects the choice of electricity. Specifically, we hypothesise that people use the kind of electricity that is offered to them as the default. We present two natural studies and two experiments in the laboratory that support this hypothesis. In the two real-world situations, there was a green default, and most people used it. In the first laboratory experiment, more participants chose the green utility when it was the default than when ‘grey’ electricity was the default. In the second laboratory experiment, participants asked for more money to give up green electricity than they were willing to pay for it. We argue that changing defaults can be used to promote pro-environmental behaviour. Potential policy-making applications of this work are discussed.  相似文献   
86.
87.

Purpose  

The aims of this paper were to quantify the heavy metals (HM) in the air of different sites in Rio de Janeiro (RJ) and Salvador (SA) using Tillandsia usneoides (Bromeliaceae) as a biomonitor, and to study the morphology and elemental composition of the air particulate matter (PM) retained on the Tillandsia surface.  相似文献   
88.
Abstract: As a contribution to Partners in Flight–Canada, the Canadian Wildlife Service developed a ranking system to help set priorities for landbird species. Two complementary species lists were generated: one with scores for "concern" representing vulnerability and population trend, and one for "responsibility" for regionally characteristic fauna. The concern score gave equal weight to vulnerability, a composite score based on abundance and breadth of range, and population trend, because its purpose was to give early warning of potential problems. Responsibility scores were scale-free and were assigned for the season in which the species is most abundant. Other systems for identifying species of concern may be more appropriate for other jurisdictions or organisms, but the responsibility ranking is widely applicable. This system is a coarse filter that generates preliminary ranks; additional information should be considered in deciding how to allocate scarce resources for conservation. Unrefined results are nonetheless useful for a variety of purposes, as illustrated by the scores for Canadian landbirds. About 25% of Canada's high-responsibility species are also of high concern. These high-concern species are not associated with specific habitats or migration patterns. Conservation of species ranking high on concern and responsibility merits cooperation with the United States and Mexico in particular. The scores identified improved monitoring as a priority conservation activity for Canada.  相似文献   
89.
90.
This paper presents a simple least squares procedure for estimating the spatial covariance and compares it with the numerically more difficult restricted maximum likelihood procedure. Thereafter, it compares design-based and kriging techniques for the estimation of spatial averages in the context of double sampling, as used in forest inventory, where terrestrial sample plots are combined with auxiliary information based on aerial photographs. A case study illustrates the theory.  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