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   591篇
  免费   4篇
  国内免费   8篇
安全科学   9篇
废物处理   26篇
环保管理   74篇
综合类   91篇
基础理论   141篇
环境理论   4篇
污染及防治   191篇
评价与监测   31篇
社会与环境   36篇
  2023年   7篇
  2022年   7篇
  2021年   8篇
  2020年   9篇
  2019年   3篇
  2018年   22篇
  2017年   12篇
  2016年   12篇
  2015年   13篇
  2014年   20篇
  2013年   46篇
  2012年   20篇
  2011年   49篇
  2010年   30篇
  2009年   34篇
  2008年   27篇
  2007年   42篇
  2006年   31篇
  2005年   22篇
  2004年   30篇
  2003年   22篇
  2002年   24篇
  2001年   12篇
  2000年   7篇
  1999年   2篇
  1998年   13篇
  1997年   2篇
  1996年   4篇
  1995年   4篇
  1994年   7篇
  1993年   5篇
  1992年   4篇
  1991年   3篇
  1990年   4篇
  1989年   2篇
  1986年   2篇
  1985年   3篇
  1982年   3篇
  1981年   5篇
  1980年   3篇
  1979年   3篇
  1960年   2篇
  1959年   1篇
  1957年   2篇
  1956年   2篇
  1955年   4篇
  1954年   1篇
  1952年   1篇
  1951年   1篇
  1922年   3篇
排序方式: 共有603条查询结果,搜索用时 15 毫秒
131.
132.
133.
134.
Radiation fog is an important modifier of atmosphericcompounds in the planetary boundary layer. In vegetated areas effects are especially pronounced due to the enlarged surface area. Besides affectingthe lower boundary of atmospheric models fog acts as amulti-phase reaction chamber leading to acid deposition. Here we present the 1-dimensional radiation fog modelCHEMIFOG_V to simulate regional radiation fogevents. The key feature of the fog model is thedetailed microphysics, where the aerosol/dropletspectrum is describedwith a joint 2-dimensional distribution, but also thedynamics, thermodynamics, and radiative transfer are calculated. Toinvestigate the interaction between fog and the biosphere amulti-layer vegetation module, including a soil module as well as a drydeposition module were coupled. Vegetation influences thedynamics, thermodynamics, and the radiation field of the lowestatmospheric layers. With CHEMIFOG_V, numerical case studieson dry and moist deposition processes on vegetation surfaces wereperformed. Hereby multi-phase chemistry and the processing of aerosolswere considered. The results show that the chemical composition of thedeposited fog droplets is mainly determined by the aerosol composition. Dry deposition fluxes are dependent on the incoming radiation and the leaves' surface conditions with respect to water coverage.Due to chemical aerosol processing and deposition, the aerosol spectrumis significantly modified in the planetary boundary layer.  相似文献   
135.
136.
Only recently, studies of forest succession have started to include the effects of browsing by wild or domestic ungulates. We aim to contribute to this topic by analysing the influence of goat grazing on the long-term coexistence of Scots pine (Pinus sylvestris L.) and pubescent oak (Quercus pubescens Willd.) in the low-elevation forests of an inner-Alpine dry valley. The forest gap model ForClim was first adapted to these site conditions by examining the site-dependent sensitivity of the model with regard to the species-specific parameterisation of the drought tolerance as well as the light demand of establishing and adult trees. In a second step, the behaviour of the model was investigated with respect to different grazing intensities and species-specific browsing susceptibilities. The last step was the application of a grazing scenario based on forest history, with 150 years of heavy browsing (by goats) at the beginning of the simulated forest succession, followed by less intensive grazing pressure.  相似文献   
137.
The planning and execution of water quality management programs requires careful collection and analysis of data coupled with a systematic review and analysis of programmatic success. The environmental audit is a tool which facilitates improved water quality planning and management. This article demonstrates the utility of the environmental audit by reviewing portions of a comprehensive review of the water quality management program for the state of Idaho. The audit is a tool which forces careful design of a sampling program before data are collected. In the audit approach, program objectives are clearly stated prior to initiation of sampling. Stated objectives are also evaluated regularly to identify tension points, that is, conflicts between expectations and reality. In the example taken from Idaho, a management review team followed a directive to redesign the water quality monitoring program. We present a summary of the redesign as proposed by that team, to illustrate the results of a typical review of monitoring programs. That summary is followed by an example of how the proposed program would differ if the audit approach had been used. The two approaches offered both coincident and conflicting recommendations. Management review team and audit recommendations for lake sampling programs were similar even though a different process was used to develop the recommendations. The most striking contrast between the two results lies in the review team's approach to the problem. The directives followed, and the team's responses, concentrate on tools, such as increasing biological monitoring or reliance on monthly BWMP stations. In contrast, the audit results stress addressing management questions for which clear objectives have been stated, depending on specific tools only as needed to meet stated objectives. Although the audit does integrate externalities in its structure, it is little affected by economic or political influences. A major strength of the audit approach is its ability to provide defensible data for management decision making.  相似文献   
138.
The soils of the Amazon's rainforests, unlike soils in rainforests in other parts of the world, have very low productivity. Experiments have shown that the Amazon's timber productivity of 2–3 m3 per year per hectare is considerably below that achievable in Northern Europe. Sustainable agricultural development therefore can be expected to be very low. However, the mineral resources of the Amazon are very extensive and offer a way to develop the Amazon without destroying the ecology, provided that some limits are set on non-mining activities.  相似文献   
139.
A major restructuring of the mining industry has been going on since the early 1980s. Using 11 important minerals this paper analyses the changing pattern of control in the mining industry for European based mining companies. In general, European mining companies have increased their control over mineral production worldwide while North American based companies have shown a decline in control of production. Production of European state-owned mining companies has declined as a result of privatization.  相似文献   
140.
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