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   330篇
  免费   11篇
  国内免费   10篇
安全科学   20篇
废物处理   10篇
环保管理   87篇
综合类   26篇
基础理论   68篇
环境理论   1篇
污染及防治   100篇
评价与监测   23篇
社会与环境   10篇
灾害及防治   6篇
  2023年   2篇
  2022年   3篇
  2021年   7篇
  2020年   3篇
  2019年   4篇
  2018年   7篇
  2017年   12篇
  2016年   8篇
  2015年   14篇
  2014年   10篇
  2013年   35篇
  2012年   17篇
  2011年   19篇
  2010年   14篇
  2009年   14篇
  2008年   18篇
  2007年   23篇
  2006年   24篇
  2005年   16篇
  2004年   16篇
  2003年   11篇
  2002年   15篇
  2001年   2篇
  2000年   5篇
  1999年   5篇
  1998年   3篇
  1997年   1篇
  1996年   4篇
  1995年   6篇
  1994年   6篇
  1993年   3篇
  1992年   3篇
  1991年   2篇
  1990年   1篇
  1987年   1篇
  1983年   2篇
  1982年   3篇
  1981年   2篇
  1980年   1篇
  1979年   2篇
  1976年   1篇
  1975年   1篇
  1974年   2篇
  1973年   1篇
  1972年   1篇
  1971年   1篇
排序方式: 共有351条查询结果,搜索用时 31 毫秒
171.
The number of environmental statutes has increased precipitously over the last twenty years. Regulations to implement these statutes went from four thousand pages in 1978 to over twelve thousand pages in 1992. With the many requirements of the regulatory programs comes a high risk of failure. Applying the continuous improvement principles and tools presented in this article has helped Lockheed meet this challenge by providing a focus and balance in its environmental programs.  相似文献   
172.
ABSTRACT In this paper, we discuss how user fees and congestion tolls can be used to improve the efficiency and equity with which the inland waterway system is managed. The advantages and disadvantages of various types of user fees (fuel taxes, segment tolls, and license fees) are presented. The rationale for the employment of congestion tolls on congested waterways is discussed. A segment toll that is equated to average variable cost is recommended for uncongested existing waterwyas. When existing waterways are congested, congestion tolls, in addition to the segment tolls, are recommended, A two-part tariff, consisting of segment tolls and an annual license fee, is recommended for “new” uncongested waterways. A three-part tariff, consisting of the first two parts plus congestion tolls, is recommended for “new” congested waterways.  相似文献   
173.
The release rates and transformation processes that influence the mobility, biological uptake, and transfer of radionuclides are essential to the assessment of the health effects in the food chain and ecosystem. This study examined concentrations of 222Th in both soil and vegetation at a closed military training site, Kirtland Air Force Base (KAFB), New Mexico. Brazilian sludge was intentionally introduced into the topsoil in the early 1960s to simulate nuclear weapon accidents. Soil (60) and vegetation (120) samples were collected from 1996 to 2000 and analyzed for radionuclides and progeny. High-resolution gamma-ray spectroscopy was used to determine radionuclide activities. The results indicate that the thorium progeny were the predominant contaminant in soil and vegetation. Concentration ratios (CRs) were calculated based on actinium levels.  相似文献   
174.
175.
176.
177.
In many communities in northern Ghana, the environment has been altered by complex natural and human driven forces with significant impact on the lives of their inhabitants. The need to formulate an improved, holistic and consistent methodological approach to assess the problem is critical for sustainable natural resource management. This paper examines the potential of the DPSIR environmental assessment framework utilizing GIS‐based participatory methodology in the assessment of environmental degradation in northern Ghana. Community truthing tools such as key informant interviews, focus group discussions, participant observation and participatory Geographical Information Systems (GIS) were employed as a means of soliciting societal responses integrated to conventional GIS spatial analysis to measure the indicators of the Driving force–Pressure–State–Impacts–Response (DPSIR) assessment framework. Post classification GIS imagery results show a marked natural vegetation decrease of 634 km2 (42%) of the study area with a corresponding increase of 600 km2 (39%) of grasses and built‐up and barren environment in the period of 14 years from 1990 to 2004. This is attributed to extreme climatic conditions and human driven causes such as poverty, population growth, migration and land tenure system. Poverty reduction strategies, amendment of the Mining and Mineral Law (PNDC law 153), improvement of the existing land tenure system and the control of migrants and Fulani herdsmen from neighbouring Burkina Faso were some of the solutions selected by the research participants, to be emphasized in the National Environmental Action Plan (EPA Act 490). This paper concludes that the DPSIR environmental assessment framework is an effective means of organizing complex environmental information to facilitate policy decision making.  相似文献   
178.
179.
Free-ranging, wild meadow voles (Microtus pennsylvanicus) were exposed to gamma radiation from a (137)Cs irradiator in a series of experiments conducted on six 1-ha meadows within a mixed deciduous forest in Manitoba, Canada. Over a period of 1-1.5 years in each of three experiments, vole populations were monitored with capture-mark-release techniques at nominal exposure rates of 200x, 9000x and 40,000x background. No effects on population or individual characteristics were detected up to the highest exposure rate (81 mGy/d). At this level, third generation voles were monitored up to a lifetime dose of about 5.7 Gy, at a measured dose rate of 44 mGy/d. Smaller numbers of overwintered animals survived and reproduced normally at doses up to 10 Gy. These results are discussed in terms of low-LET, external chronic radiation effects on rodents in the laboratory and the field, relative to current views on appropriate benchmarks for the protection of biota.  相似文献   
180.
Previous historic trends analyses on 21st Century hydrologic data in the United States generally focus on annual flow statistics and have continued to use USGS hydro‐climatic data network (HCDN) stations, although post‐1988 diversions and runoff regulations are not reflected in the HCDN. Using a more recent dataset, Geospatial Attributes of Gages for Evaluating Streamflow, version II (GAGES II), compiled by Falcone (2012), which includes more watersheds with reference conditions, a comprehensive analysis of changes in seasonal, and annual streamflow in Wisconsin watersheds is demonstrated. Given the pronounced influence of seasonal hydrology in Wisconsin watersheds, the objective of this study is to elucidate the nature of temporal (annual, seasonal, and monthly) changes in runoff. Considerable temporal and regional variability was found in annual and seasonal streamflow changes between the two historic periods 1951‐1980 and 1981‐2010 considered in the study. For example, the northern watersheds show relatively small changes in streamflow discharge ranging from ?6.0 to 4.2%, while the southern watersheds show relatively large increases in streamflow discharge ranging from 13.1 to 18.2%. To apportion streamflow changes to climate and nonclimatic factors, a method based on potential evapotranspiration changes is demonstrated. Results show that nonclimatic factors account for more than 60% of changes in annual runoff in Wisconsin watersheds considered in the study.  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