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   16394篇
  免费   146篇
  国内免费   123篇
安全科学   337篇
废物处理   639篇
环保管理   1880篇
综合类   3948篇
基础理论   3706篇
环境理论   6篇
污染及防治   4043篇
评价与监测   1027篇
社会与环境   1028篇
灾害及防治   49篇
  2022年   109篇
  2021年   122篇
  2019年   106篇
  2018年   209篇
  2017年   200篇
  2016年   313篇
  2015年   243篇
  2014年   363篇
  2013年   1100篇
  2012年   410篇
  2011年   621篇
  2010年   484篇
  2009年   562篇
  2008年   646篇
  2007年   689篇
  2006年   610篇
  2005年   506篇
  2004年   533篇
  2003年   524篇
  2002年   495篇
  2001年   629篇
  2000年   397篇
  1999年   305篇
  1998年   190篇
  1997年   206篇
  1996年   225篇
  1995年   234篇
  1994年   233篇
  1993年   217篇
  1992年   200篇
  1991年   207篇
  1990年   202篇
  1989年   175篇
  1988年   169篇
  1987年   155篇
  1986年   156篇
  1985年   150篇
  1984年   171篇
  1983年   169篇
  1982年   175篇
  1981年   145篇
  1980年   134篇
  1979年   128篇
  1978年   138篇
  1977年   115篇
  1976年   107篇
  1975年   109篇
  1974年   120篇
  1971年   101篇
  1967年   105篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
94.
In the UK for the period 1994-99, a broad range of environmental projects were given financial support through the European Agriculture Guidance and Guarantee Fund under the Objective 1 and Objective 5b programmes. This paper is concerned with the ex-post evaluation of these projects set within a Sustainable Development framework. The aim was to identify project types or characteristics that offered the greatest return on investment. A classification of six broad project types was adopted. The evaluation revealed that there were significant differences between individual projects with respect to the type and scale, and temporal and social distribution of the benefits they delivered. In particular, as well as delivering environmental and economic benefits, many projects made a significant contribution to the development of human and social capital. The paper concludes that it is possible to improve the basis for future project selection in order to maximise the returns on environmental investments in the context of sustainable development.  相似文献   
95.
Urban atmospheric environment contains many trace organic pollutants that are related to the incomplete fuel combustion in domestic heating, industrial plants and automobile traffic. Removal of these pollutants from the atmosphere takes place through wet and dry deposition as well as chemical transformations. In this study, concentrations of polycyclic aromatic hydrocarbons (PAHs) in wet deposition samples were determined at an urban site of Turkey. Wet and dry deposition samples were collected using Andersen Rain Sampler. The sampler was modified accordingly for the collection of organic pollutants. Collected samples were preconcentrated by using solid phase extraction (SPE) disks and consecutively analyzed by Gas Chromatography-Mass Spectrometry (GC-MS). Among the 13 compounds quantified in this study, anthracene, fluoranthene, and pyrene were found more frequently and at elevated concentrations (202, 271 and 260 ng L-1 mean concentrations, respectively).Concentrations of PAHs were found to be high in winter period.  相似文献   
96.
97.
ABSTRACT: Evidence is presented that snowmelt runoff from an urban watershed can produce density current intrusions (underflows) in a lake. Several episodes of density current intrusions are documented. Water temperatures and salinities measured near the bottom of a 10 m deep Minneapolis lake during the late winter warming periods in 1989, 1990, 1991, and 1995 show significant rapid changes which are correlated with observed higher air temperatures and snowmelt runoff. The snowmelt runoff entering this particular lake (Ryan Lake) has increased electrical conductivity, salinity, and density. The source of the salinity is the salt spread on urban streets in the winter. Heating of littoral waters in spring may also contribute to the occurrence of the sinking flows, but is clearly not the only cause.  相似文献   
98.
Car manufacturers must eliminate automotive shredder residues (ASR). Two ways of incineration are of interest: at 850°C in municipal waste incinerators or at higher temperatures, above 1100°C in cement plants. These processes reduce the mass and the volume of waste to be disposed of in landfills and energy recovery might be possible. Regulations govern the emission of gaseous effluents to control environmental risk. To determine gaseous effluents from a pilot sacle or an industrial incineration plant, an artificial ASR was made by mixing three representative organic polymers present in the real ASR, namely polyvinylchloride, polyurethane and rubber. This mixture was incinerated at 850 and 1100°C in laboratory experiments and the analyses of the principal gaseous effluents such as carbon oxides, nitrogen oxides, volatile organic compounds, hydrochloric and hydrocyanic acids and sulphur compounds are presented and discussed. Lastly, in order to simulate artificial ASR behaviour, the composition of the combustion gases at equilibrium was calculated using a Gibbs energy minimisation code.  相似文献   
99.
Biological and physicochemical approaches were utilized in a treatment train for acid mine dis charge (AMD) waters. Anaerobic bioreactors, chemical precipitation reactors, and biopolymer chelation reactors, operated in static, semicontinuous, and continuous flow modes, removed significant quantities of metals and sulfates associated with AMD water. Static tests indicated accept able copper removal via precipitation by generation of hydrogen sulfide in anaerobic reactors. However, low pH affected the biopolymer coating in the chelation reactor, resulting in loss of bed surface. Corrections of AMD to pH > 7 resulted in some metal precipitationprior to biopolymer treatment. A series of static semicontinuous tests at pH 5.0 provided improved metal and sulfate removal. Copper (Cu+) was reduced to trace concentrations, while manganese (Mn+), although reduced, proved to be the most recalcitrant of the metals. © 2006 Wiley Periodicals, Inc.  相似文献   
100.
The distribution and impacts of different nitrogen pollutants are inextricably linked. To understand the problem fully, the interactions between the different pollutants need to be taken into account. This is particularly important when it comes to abatement techniques, since measures to reduce emissions of one nitrogen pollutant can often lead to an increase in another. This project represents a step towards greater understanding of these issues by linking together new and existing nitrogen flux models into a larger framework. The modelling framework has been constructed and some of the nitrogen flows between fields, farms and the atmosphere have been modelled for a UK study area for typical farm management scenarios.  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