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   4349篇
  免费   190篇
  国内免费   105篇
安全科学   156篇
废物处理   41篇
环保管理   1088篇
综合类   1900篇
基础理论   302篇
环境理论   19篇
污染及防治   307篇
评价与监测   624篇
社会与环境   189篇
灾害及防治   18篇
  2023年   26篇
  2022年   29篇
  2021年   54篇
  2020年   159篇
  2019年   60篇
  2018年   58篇
  2017年   112篇
  2016年   137篇
  2015年   101篇
  2014年   176篇
  2013年   221篇
  2012年   155篇
  2011年   311篇
  2010年   152篇
  2009年   279篇
  2008年   219篇
  2007年   221篇
  2006年   217篇
  2005年   108篇
  2004年   130篇
  2003年   188篇
  2002年   174篇
  2001年   175篇
  2000年   199篇
  1999年   172篇
  1998年   147篇
  1997年   147篇
  1996年   89篇
  1995年   62篇
  1994年   79篇
  1993年   75篇
  1992年   50篇
  1991年   30篇
  1990年   14篇
  1989年   18篇
  1988年   10篇
  1987年   8篇
  1986年   16篇
  1985年   14篇
  1984年   14篇
  1983年   4篇
  1982年   7篇
  1981年   6篇
  1980年   4篇
  1978年   11篇
  1977年   5篇
  1974年   1篇
排序方式: 共有4644条查询结果,搜索用时 50 毫秒
951.
Estuaries and coastal lagoons are characterized by a strong spatial and temporal variability of physicochemical characteristics and productivity patterns. In these environments, the magnitude and direction of the ecological responses to inorganic nutrient increase (i.e. eutrophication) are difficult to predict. In the framework of the project, New Indicators of Trophic state and environmental quality of marine coastal ecosystems and transitional environments (NITIDA), we analysed benthic indicators of trophic state, ecosystem efficiency, and environmental quality in four different transitional environments. The trophic state of the sediments was assessed in terms of quantity and bioavailability of sediment organic C pools; ecosystem efficiency was determined in terms of the prokaryote efficiency in exploiting enzymatycally degraded organic C; environmental quality was determined in terms of meiofaunal diversity. Here, we provide a synopsis of the results obtained and a meta-analysis of the scores assessments obtained using the different ecological indicators of environmental quality and demonstrate that trophic state, ecosystem efficiency, and biodiversity in transitional ecosystems are closely linked. We conclude that the assessment of the environmental quality of transitional ecosystems should be based upon a battery of trophic state indicators and 'sensors' of ecosystem functioning, efficiency, and quality.  相似文献   
952.
The biomarker approach has been used for 25 years to study the environmental quality of marine, brackish and freshwater ecosystems. Biomarkers may indicate health status and can be applied to organisms of all zoological phyla by destructive or non destructive methods. For 5 years we have been using this approach in zooplankton to detect ecotoxicological alterations at low levels of the food chain due to contaminants. Here we review our approach to validate and apply biomarker techniques in zooplankton. We discuss advantages, limitations, some results and future research. We indicate that biomarkers in zooplankton can be used as new indices of trophic status and ecological integrity of Italian marine coastal and lagoon environments, to be included among the tools specified by Italian law D.Lgs. 152/2006.  相似文献   
953.
从环境成本内部化、绿色消费需求和贸易壁垒创新的角度阐述了国际贸易中环境保护介入的成因,并提出了若干对策。  相似文献   
954.
The systems approach permits us to analyze national security as a cluster of interconnected elements, in which the environmental dimension appears to be the most important one. The environmental problem is divided into two main aspects: environmental security per se and the impact of environment on the overall status of a nation's security. It is argued here that the quality of life and health serve as both the main objective and the principal criterion of environmental security in a social system. Indices of these two factors are used in this article as indicators of the state of this type of security. They confirm that vast areas of Russia, the Ukraine, and Central Asia (especially the Aral Sea region) should be considered as presenting a substantial risk to local people and even producing global impacts on both natural and man-made systems. Environmental factors that destabilize national security are also divided into two groups: those that impact social systems directly and negatively (mainly natural disasters) and technological and sociopolitical agents that cause indirect impacts, in both war and peace time, as well as in the civil and military sectors of the economy. Developments in the former Soviet Union (the Commonwealth of Independent States) are used as an illustration of the consequences that such impacts may have on the status of national security.  相似文献   
955.
Development of a marina in a flooded brownstone quarry will require construction of a canal to the Connecticut River through an isthmus separating the two systems. An environmental audit over a 16-month period developed quantitative limnological data required by regulatory agencies. The deep quarry basin, protected by high sandstone walls, became strongly stratified in summer. Development of littoral vegetation in the quarry was prevented by the steep sides of the basin. Unusual characteristics of the manmade quarry basin, compared to most natural lakes in Connecticut, included a mean depth of 14 m, an intense thermocline, and negative heterograde oxygen profiles with metalimnetic minima. Alkalinity, conductivity, and nutrient levels differed significantly between the quarry and the river. Mean chlorophyll a concentrations in the two systems were similar, but the distribution of phytoplankton classes were quite different. The environmental audit, by comparing physical, chemical, and biological characteristics of the quarry to those of the river, allowed prediction of changes in trophic status when the two systems are joined.  相似文献   
956.
Several approaches can be used to define and construct visual buffer strips around proposed new facility sites in a forested environment. A visual buffer strip of a given value, defines a region around an object within which the probability of an unblocked view of all or portions of it by an observer are less than the buffer strip probability value. Two primary approaches are used to define visual buffer strips that take into account the size of the vegetative elements and their individual effects on visibility. Several variations and combinations of the approaches are possible. One approach defines a visual buffer strip based on the average probability of a clear view of points along the object by an observer; the other approach is based on the visibility of the feature as a whole. The computation and construction of visual buffer strips based on these two concepts are presented. Comparisons of the two approaches for specific feature shapes are also described.  相似文献   
957.
Substantial land degradation of agricultural catchments in Australia has resulted from the importation of European farming methods and the large-scale clearing of land. Rural communities are now being encouraged by government to take responsibility for environmental care. The importance of community involvement is supported by the view that environmental problems are a function of interactions between people and their environment. It is suggested that the commonly held view that community groups cannot care for their resources is due to inappropriate social institutions rather that any inherent disability in people. The communicative catchment is developed as a vision for environmental care into the future. This concept emerges from a critique of resource management through the catchment metaphors of the reduced, mechanical, and the complex, evolving catchment, which reflect the development of systemic and people-centered approaches to environmental care. The communicative catchment is one where both community and resource managers participate collaboratively in environmental care. A methodology based on action research and systemic thinking (systemic action research) is proposed as a way of moving towards the communicative catchment of the future. Action research is a way of taking action in organizations and communities that is participative and informed by theory, while systemic thinking takes into account the interconnections and relationships between social and natural worlds. The proposed vision, methodology, and practical operating principles stem from involvement in an action research project looking at extension strategies for the implementation of total catchment management in the Hunter Valley, New South Wales.  相似文献   
958.
Environmental protection policies generate an equity question concerning the fair allocation of environmental benefits and costs. This paper presents evidence from Greece during the 1980s. The findings reveal that Greek environmental policies, in the form of government self-regulatory programs, are mostly regressive in nature. At the regional level these programs combine all forms of vertical equity. Since the public sector finances the majority of related expenditures out of taxes, the regressive elements of environmental policies have been reinforced by discretionary fiscal measures and tax evasion, accompanied by inflation, which have distorted the country's progressive tax system.  相似文献   
959.
The current Mexican environmental law provides the legal basis for comprehensive land-use planning. Under the law, development of natural ecosystems must combine goals, policies, and practices towards the sustainable use of natural resources and the protection of biological diversity. Thus, ecosystem manipulation must be able to counter fragmentation of natural ecosystems and isolation of natural reserves, while providing for human needs. Assessment of the potential of natural ecosystems and management impacts are required. Multiple-resource simulation is an assessment and land-use planning tool that permits managers and decision makers to comply with the law, providing a flexible, user-oriented system that can meet the needs of managers, conservationists, and researchers. A multiple-resource model and an example of how it can be applied to meet planning needs is presented for discussion.  相似文献   
960.
The US Department of Energy (DOE) plans to conduct site characterization studies at Yucca Mountain, Nevada, to determine if the location is a suitable site for a nuclear waste repository. In lieu of traditional environmental review in accordance with the National Environmental Policy Act of 1969, the DOE is relying on an environmental assessment (EA) mandated by the Nuclear Waste Policy Act of 1982 as the cornerstone of its environmental program for the Yucca Mountain Project. Because of statutory restrictions, the EA is not based on comprehensive baseline information. Neither does it address fundamentals of environmental analysis such as ecological integrity and assessment of cumulative impacts. Consequently, the present environmental program for Yucca Mountain reflects decisions made without complete information and integrated environmental review. The shortcomings of the program risk compromising the natural integrity of Yucca Mountain and invalidating future assessment of the ability of a nuclear waste repository located at the site to protect the environment. Significant improvements are needed in the repository siting program before it can serve as a model of how society can evaluate the long-term environmental consequences of advanced technologies, as has been suggested.  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