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   896篇
  免费   88篇
  国内免费   110篇
安全科学   99篇
废物处理   20篇
环保管理   380篇
综合类   296篇
基础理论   114篇
环境理论   1篇
污染及防治   32篇
评价与监测   17篇
社会与环境   101篇
灾害及防治   34篇
  2023年   16篇
  2022年   18篇
  2021年   24篇
  2020年   46篇
  2019年   33篇
  2018年   36篇
  2017年   36篇
  2016年   43篇
  2015年   33篇
  2014年   42篇
  2013年   81篇
  2012年   56篇
  2011年   75篇
  2010年   39篇
  2009年   33篇
  2008年   46篇
  2007年   43篇
  2006年   59篇
  2005年   32篇
  2004年   27篇
  2003年   33篇
  2002年   23篇
  2001年   30篇
  2000年   13篇
  1999年   17篇
  1998年   11篇
  1997年   10篇
  1996年   8篇
  1995年   10篇
  1994年   6篇
  1993年   10篇
  1992年   4篇
  1991年   8篇
  1990年   3篇
  1989年   11篇
  1988年   4篇
  1986年   4篇
  1985年   3篇
  1984年   3篇
  1983年   6篇
  1982年   3篇
  1981年   6篇
  1980年   6篇
  1979年   6篇
  1978年   3篇
  1977年   5篇
  1976年   6篇
  1973年   3篇
  1972年   4篇
  1971年   10篇
排序方式: 共有1094条查询结果,搜索用时 15 毫秒
981.
ABSTRACT

Water shortages may present different and diverse implications for gender subgroups particularly in low-income settings. Yet, little research has documented the gendered livelihood implications of water shortages in Ghana. Based on a cross-sectional mixed method research involving a survey of 250 household heads and complemented with a qualitative study of 86 participants, the paper examines the differential effects of sporadic water supply in Tatale-Sanguli District of Northern Ghana. Our findings suggest that the livelihood effects of sporadic water supply in Tatale-Sanguli area are gendered, with females being disproportionately affected as compared to males. These differential effects are often framed by both gender role differentiation and inequities in access to vital productive resources and critical assets such as bicycles, tricycles and motor bikes. These findings highlight not only the need for local government and non-governmental organisations to step up efforts in water provision, but also to recognise the gendered effects of water shortages in Tatale-Sanguli District. Key to policy is also to ensure that programmatic interventions during water shortages take account of the likely gendered effects and differentiated burdens.  相似文献   
982.
我国是世界上13个贫水国之一,水资源紧缺的问题在一些地区已制约经济和社会的发展。中水主要是指城市污水或生活污水经处理后达到一定的水质标准,可在一定的范围内重复使用的非饮用杂用水。中水的水质介于上水和下水之间,是水资源有效利用的一种形式。开展中水回收工作,已经显现出开源和减轻水污染的双重功能。  相似文献   
983.
沱江内江段饮用水源的污染防治   总被引:6,自引:1,他引:5  
许毅  罗长椿 《四川环境》1998,17(2):65-67
通过加强对沱江内江段的水源污染进行防治,以及加快自来水厂制水工艺的改进,使集中式供水水质得到了明显改善,已取得较好的社会效益和环境效益  相似文献   
984.
ABSTRACT: A set of simulation models consisting of a weather generator, and irrigation supply, soil moisture and crop growth components was used to evaluate the impacts of climate change on irrigated corn in locations near Albany, New York, Indianapolis, Indiana, and Oklahoma City, Oklahoma. The models evaluated the combined effects of modified water demand, supply and crop management (planting date, cultivar selection, irrigation). Simulations were duplicated for 100-year weather sequences based on current (1961–1988) weather statistics, and statistics modified by outputs from the GFDL GCM runs showing the effects from doubling of atmospheric CO2. Climate impacts differed greatly with location and management. Effects were most adverse in New York and least damaging in Indiana. At all sites, the beneficial effects of longer growing season and increased water supply were generally overcome by the detrimental impacts of increased evapotranspiration and reduced solar radiation during plant maturing stages. Adverse impacts of climate change can be substantially reduced by irrigation and appropriate selection of planting dates and cultivars.  相似文献   
985.
ABSTRACT: This paper describes two methods that are introduced to improve the computational effort of stochastic dynamic programming (SDP) as applicable to the operation of multiple urban water supply reservoir systems. The stochastic nature of streamflow is incorporated explicitly by considering it in the form of a multivariate probability distribution. The computationally efficient Gaussian Legendre quadrature method is employed to compute the conditional probabilities of streamflow, which accounts for the serial correlation of streamflow into each storage and the cross correlation between the streamflow into various storages. A realistic assumption of cross correlation of streamflow is introduced to eliminate the need to consider the streamflow combinations which are unlikely to occur in the SDP formulation. A “corridor” approach is devised to eliminate the need to consider the infeasible and/or inferior storage volume combinations in the preceding stage in computing the objective function in the recursive relation. These methods are verified in terms of computational efficiency and accuracy by using a hypothetical example of three interconnected urban water supply reservoirs. Therefore, it can be concluded that these methods allow SDP to be more attractive for deriving optimal operating rules for multiple urban water supply reservoir systems.  相似文献   
986.
论河口海底淡水资源的形成   总被引:1,自引:0,他引:1  
在分析沿海河口区域地质构造和层序地层学特征的基础上,提出了潜在的新的淡水资源---海底淡水资源,并研究了沿海河口区域海底淡水的形成、赋存、运移等特性。  相似文献   
987.
论国家资源安全及其保障战略   总被引:30,自引:5,他引:30  
论文系统探索了资源安全的基本内涵,并初步划分了不同类型国家资源安全。作者认为资源安全是资源供给与需求相互均衡的产物,它是一个内涵丰富的复合范畴。资源安全可以划分为全球性安全、区域性安全和地方性安全。按时间序列和资源生产与消费等,还可以将资源安全划分为短期资源安全、中期资源安全和长期资源安全,以及资源净出口国的资源安全和资源净进口国的资源安全。资源安全因其短缺或稀缺而来,并且首先表现为对石油安全的担忧。文章进一步分析了国家资源安全的涵义、基本特征、影响因素和发展趋势,分析了不同类型国家资源安全战略。最后,从系统分析的角度,提出了保障国家资源安全的七大基本策略,即资源保护战略、资源流通战略、资源消费战略、资源利用战略、资源回收战略、资源创新战略、资源管理战略,形成完整的国家资源安全复合保障体系。  相似文献   
988.
区域给水与污水处理及回用系统规划的优化研究   总被引:1,自引:0,他引:1  
针对目前水污染控制规划只考虑污水处理以及经济效益这些不足,将区域给水、污水处理及中水系统作为统一整体进行统一规划,建立以区域经济效益、社会效益及环境效益最大化为目标,以各子系统供需水量及水质要求为约束条件的优化模型,并应用到具体实际中进行验证,结果表明区域给水与污水处理及回用系统规划的实用性与科学性.  相似文献   
989.
通过对深圳市福田河污染与生态破坏的现状及其原因分析,将河流水系及其流域地区统一纳入一个生态系统来考虑,提出了以生态恢复与重建为河流综合整治的思路,并确定了综合整治目标、主要工程措施和关键技术。  相似文献   
990.
One predicted impact of the construction of the hydroelectric plant of Brégnier-Cordon (Upper Rhône River, France) was the rise of the water table in the part of the plain situated upstream from the power plant. This impact made it possible to test the hypothesis that the slowing, indeed the halting, of ecological successions occurs in the former channels upstream from the power plant because of the increase of seepage supply through coarse alluvium. The vegetation of two braided former channels, one situated upstream (impacted site) and one downstream (reference site) of the power plant was studied over a period of nine years, before (1981) and after (1985, 1986, 1987, and 1989) the construction of the hydroelectric power-plant. The two sites had similar vegetation and successional stages at the beginning of the study. The seepage supply increases in the impacted site resulted in the establishment ofChara globularis andRiccia fluitans, indicating groundwater influence, but, after halting in 1985–1986, the ecological succession proceeded slowly again in 1987 and 1989, depicted by continuing eutrophication (expressed particularly by the increasing abundance ofCeratophyllum demersum). As expected, ecological succession was not halted in the reference site. Terrestrialization processes were apparent and changes were more rapid at its upstream part.  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