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   12397篇
  免费   112篇
  国内免费   94篇
安全科学   340篇
废物处理   473篇
环保管理   1690篇
综合类   2158篇
基础理论   3254篇
环境理论   7篇
污染及防治   3114篇
评价与监测   832篇
社会与环境   649篇
灾害及防治   86篇
  2023年   76篇
  2022年   148篇
  2021年   129篇
  2020年   90篇
  2019年   103篇
  2018年   179篇
  2017年   156篇
  2016年   249篇
  2015年   211篇
  2014年   291篇
  2013年   929篇
  2012年   381篇
  2011年   524篇
  2010年   440篇
  2009年   498篇
  2008年   551篇
  2007年   541篇
  2006年   471篇
  2005年   432篇
  2004年   362篇
  2003年   378篇
  2002年   365篇
  2001年   479篇
  2000年   349篇
  1999年   214篇
  1998年   134篇
  1997年   158篇
  1996年   165篇
  1995年   192篇
  1994年   195篇
  1993年   159篇
  1992年   134篇
  1991年   170篇
  1990年   163篇
  1989年   159篇
  1988年   115篇
  1987年   114篇
  1986年   118篇
  1985年   91篇
  1984年   109篇
  1983年   110篇
  1982年   118篇
  1981年   108篇
  1980年   97篇
  1979年   112篇
  1978年   73篇
  1977年   76篇
  1975年   76篇
  1973年   73篇
  1967年   66篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
941.
The price of fuelwood has been increasing at a rate higher than that of the consumer price index in most of the major urban centres of India. Today, in terms of cost per unit of energy delivered, fuelwood is more than twice as expensive as kerosene for cooking. This has immense public policy implications. A number of complementary policy interventions are needed so that forests can be saved and the stability of energy supplies can be achieved in developing countries.  相似文献   
942.
One hundred seventy-seven police officers and their spouses from two metropolitan areas completed separate questionnaires regarding stress and coping. Both the police and spouses reported using four coping activities in response to their own stressors: problem focused, emotion focused, religiosity, and rugged individualism. Three potential police strains previously noted in non-empirical literature were given special attention; divorce potential, drinking behavior, and suicide thoughts.  相似文献   
943.
In reaction to a paper inEnvironmental Management in which the sense and sensibility of environmental assessments of packaging were questioned, it is argued that these types of assessments may be very useful, provided the relevant types of questions are posed. These boundary conditions are discussed, along with an overview of more recent methodological developments with respect to environmental assessment of products.  相似文献   
944.
Amid growing concern about the conservation of renewable natural resources, the process, extent and symptoms of their degradation are examined with specific reference to the Upper Pokhara Valley. Based on a household survey, field observations, informal deliberations and land use analysis, the results of this study reveal that forests and grazing land have been subject to increasing degradation caused by demographic, socioeconomic and institutional factors. The intensity of degradation varies by watershed. In particular, rainfed pakho land on steep slopes is under the severe threat of accelerating soil erosion, despite the construction of terraces. This calls for the formulation of a comprehensive natural resource conservation strategy which should be based on a framework comprising an integrated population control programme, planned land use changes and institutional reforms .  相似文献   
945.
946.
ABSTRACT: We evaluated the effects of institutional responses developed for coping with a severe sustained drought (SSD) in the Colorado River Basin on selected system variables using a SSD inflow hydrology derived from the drought which occurred in the Colorado River basin from 1579–1616. Institutional responses considered are reverse equalization, salinity reduction, minimum flow requirements, and temporary suspension of the delivery obligation of the Colorado River Compact. Selected system variables (reservoir contents, streamflows, consumptive uses, salinity, and power generation) from scenarios incorporating the drought-coping responses were compared to those from Baseline conditions using the current operating criteria. The coping responses successfully mitigated some impacts of the SSD on consumptive uses in the Upper Basin with only slight impacts on consumptive uses in the Lower Basin, and successfully maintained specified minimum streamflows throughout the drought with no apparent effect on consumptive uses. The impacts of the coping responses on other system variables were not as clear cut. We also assessed the effects of the drought-coping responses to normal and wet hydrologic conditions to determine if they were overly conservative. The results show that the rules would have inconsequential effects on the system during normal and wet years.  相似文献   
947.
ABSTRACT: The effectiveness of urban Best Management Practices (BMPs) in achieving the No-Net-Increase Policy (NNTP), a policy designed to limit nonpoint nitrogen loading to Long Island Sound (US), is analyzed. A unit loading model is used to simulate annual nitrogen exported from the Norwalk River watershed (Connecticut) under current and future conditions. A probabilistic uncertainty analysis is used to incorporate uncertainty in nitrogen export coefficients and BMP nitrogen removal effectiveness. The inclusion of uncertainty in BMP effectiveness and nitrogen export coefficients implies that additional BMPs, or BMPs with a greater effectiveness in nitrogen removal, will be required to achieve the NNIP. Even though including uncertainty leads to an increase in BMP implementation rates or BMP effectiveness, this type of analysis provides the decision maker with a more realistic assessment of the likelihood that implementing BMPs as a management strategy will be successful. Monte Carlo simulation results indicate that applying BMPs to new urban developments alone will not be sufficient to achieve the NNIP since BMPs are not 100 percent effective in removing the increase in nitrogen caused by urbanization. BMPs must also be applied to selected existing urban areas. BMPs with a nitrogen removal effectiveness of 40–60 percent, probably the highest level of removal that can be expected over an entire watershed, must be applied to at least 75 percent of the existing urban area to achieve the NNIP This high rate of application is not likely to be achieved in urbanized watersheds in the LIS watershed; therefore, additional point source control will be necessary to achieve the NNIP  相似文献   
948.
Lack of sufficient analytical capacity in most of the countries of sub-Saharan Africa has been frequently mentioned as a major factor limiting the effectiveness of drought management interventions. In this article we describe an approach used in Malawi for the past three years to develop a decentralized capacity to analyse drought management and disaster prevention programmes. A conceptual framework is presented which identifies the areas in which capacity strengthening is required and lessons from the Malawi experience are presented. Various issues relating to the efficiency of capacity building programmes are discussed. We argue that continuous dialogue between development researchers and decision-makers, and between trainers in academic institutions and donor agencies, is essential for achieving the goals of improved capacity for drought management and disaster prevention.  相似文献   
949.
950.
A resource survey and planning method for parks, reserves, and other environmentally significant areas (ESAs) is presented in the context of a holistic balanced approach to land use and environmental management. This method provides a framework for the acquisition, analysis, presentation, and application of diverse ecological data pertinent to land use planning and resource management within ESAs. Through the independent analysis and subsequent integration of abiotic, biotic, and cultural or ABC information, land areas within an ESA are identified in terms of their relative environmental significance and environmental constraints. The former term encompasses wildlife, historic, and other resource values, while the latter term reflects biophysical hazards and sensitivities, and land use conflicts. The method thus calls for a matching of an ESA's distinctive attributes with appropriate land use and institutional arrancements through an analysis of available acts, regulations, agencies, and other conservation and land use management mechanisms. The method culminates with a management proposal showing proposed park or reserve allocations, buffer areas, or other land use controls aimed at preserving an ESA's special ecological qualities, while providing for resource development. The authors suggest that all resource management decisions affecting ESA's should be governed by a philosophical stance that recognizes a spectrum of broad land use types, ranging from preservation to extractive use and rehabilitation.  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