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   517篇
  免费   10篇
  国内免费   4篇
安全科学   28篇
废物处理   26篇
环保管理   66篇
综合类   45篇
基础理论   126篇
污染及防治   161篇
评价与监测   39篇
社会与环境   30篇
灾害及防治   10篇
  2023年   6篇
  2022年   10篇
  2021年   10篇
  2020年   8篇
  2019年   10篇
  2018年   12篇
  2017年   13篇
  2016年   17篇
  2015年   15篇
  2014年   16篇
  2013年   47篇
  2012年   25篇
  2011年   44篇
  2010年   29篇
  2009年   30篇
  2008年   28篇
  2007年   33篇
  2006年   34篇
  2005年   33篇
  2004年   19篇
  2003年   14篇
  2002年   17篇
  2001年   4篇
  2000年   3篇
  1999年   6篇
  1998年   4篇
  1997年   6篇
  1996年   4篇
  1995年   6篇
  1994年   6篇
  1993年   3篇
  1992年   4篇
  1991年   1篇
  1990年   3篇
  1989年   1篇
  1985年   2篇
  1983年   1篇
  1982年   2篇
  1981年   2篇
  1980年   1篇
  1974年   1篇
  1964年   1篇
排序方式: 共有531条查询结果,搜索用时 328 毫秒
231.
232.
Journal of Polymers and the Environment - This work aims to investigate the effect of organically modified montmorillonite (OMMT) and vermiculite (OVT) clays on the properties of poly(lactic acid)...  相似文献   
233.
234.
235.
ABSTRACT: Concrete block irrigation diversion systems have been proposed as alternatives to permanent dams of concrete or rock or temporary gravel berms. Permanent dams can cause stream channel instability, bank erosion, sediment pollution, ice flow blockage, and safety problems for recreational floating craft. Temporary berms can require substantial streambed disturbance and can promote sediment pollution, stream bank instability, and bank erosion. A design procedure was developed based on a model of the hydraulic performance of concrete block diversion systems. The procedure was used to model a site on the Gallatin River in Montana. The method relies on HEC-RAS (Hydrologic Engineering Center -River Analysis System) software combined with analytical techniques in an iterative scheme. The hydraulic performance of different diversion configurations (the existing heavy-rock diversion system, concrete blocks oriented parallel to flow, and concrete blocks oriented diagonally) was assessed using the model under a range of flow rates. The minimum diversion dimensions (length, number, and size of blocks) that maintained block stability while diverting the requisite flow were determined for each model run. At the Gallatin River site, the block system oriented parallel to flow required less diversion material than the diagonal orientation. The recommended diversion length was 51.8 m (170 ft). Trapezoidal blocks with a top width of 20.3 cm (8 in), a height of 45.7 cm (18 in), and side slopes of 2 vertical to 1 horizontal were specified. This configuration minimizes the total block mass, diverts the required flow, and has a factor of safety of 2.0 against block displacement.  相似文献   
236.
There are several different approaches to evaluate regional environmental and sustainability performance, where regional indicators are an emerging issue. Academia could play an important role in many sustainable initiatives, giving credibility, scientific and technical support and contribute to increasing public participation. This paper intends to trace the Portuguese profile on regional Sustainable Development Indicators (SDI) initiatives and contribute to an understanding of the key factors related to the role of academia in those processes. A national survey was conducted to obtain data on SDI initiatives on a regional scale and the Portuguese profile was defined. Overall results show that SDI implementations are concluded in one region and are being implemented in three of the total of seven regions, despite a significant lack of institutional guidelines and policy guidance from national authorities. The particular approach conducted in the Algarve, the most southerly region of Portugal, was analysed. The indicators developed for this region are a practical example of how academia and regional public authorities can cooperate efficiently, involving multi-stakeholders, to obtain the desired outcomes.  相似文献   
237.
238.
The Critical Review on Motor Vehicle Inspection/Maintenance Programs was presented by John C. Elston at a Session at the 74th Annual Meeting of APCA in Philadelphia. Mr. Elston summarized his paper which had been published in the May 1981 of JAPCA. Prepared discussions which were presented by Mr. Cackette, Mr. Weaver, Dr. Jones, and Mr. Wallis are reproduced here. In addition, comments made from the floor by Dr. McKee, Mr. Pattison, and Mr. Seliber have been formalized and are presented here along with the discussion from the floor. Mr. Elston responds to the comments of his peers. Dr. Melvin W. First was Moderator of the Session.  相似文献   
239.
Dutta, Sudarshan, Shreeram Inamdar, Jerry Tso, Diana S. Aga, and J. Tom Sims, 2012. Dissolved Organic Carbon and Estrogen Transport in Surface Runoff from Agricultural Land Receiving Poultry Litter. Journal of the American Water Resources Association (JAWRA) 48(3): 558-569. DOI: 10.1111/j.1752-1688.2011.00634.x Abstract: Dissolved organic carbon (DOC) provides a reactive substrate for the transport of organic contaminants with runoff. Very few studies have investigated the export of DOC from agricultural land, especially those receiving manure applications. We investigated exports of DOC in surface runoff from agricultural fields receiving various treatments of poultry litter (raw vs. pelletized). In addition, we also investigated how estrogens in runoff were associated with DOC. Different forms of estrogens studied were: estrone, 17β-estradiol, estriol, and their conjugates. Experimental agricultural plots were 12 m × 5 m long and had reduced tillage and no-till management practices. The aromatic content of DOC was characterized using specific ultraviolet absorbance (SUVA). Flow-weighted concentrations of DOC and SUVA in surface runoff from plots with poultry litter were significantly (p ≤ 0.10) greater than the control (no litter) plots. Compared to pelletized poultry litter, reduced-tillage plots with raw litter yielded higher DOC concentrations and SUVA values. No significant differences (p ≥ 0.10) in DOC and SUVA were observed between litter treatments for plots with no-till. Total estrogen concentrations (including all forms) were positively and significantly (p ≤ 0.10) correlated with DOC. These results can help select and guide agricultural management practices that can reduce the exports of DOC and associated contaminant from agricultural land receiving manure applications.  相似文献   
240.
Conflict between people and carnivores can lead to the widespread killing of predators in retaliation for livestock loss and is a major threat to predator populations. In Kenya, a large, rural, pastoralist population comes into regular conflict with predators, which persist across southern Kenya. We explored the social and psychological backdrop to livestock management practices in this area in a process designed to be easy to use and suitable for use across large areas for the study of conflict and transboundary implementation of wildlife conflict reduction measures, focusing on community involvement and needs. We carried out fully structured interviews of livestock managers with a survey tool that examined how social and psychological factors may influence livestock management behavior. We compared survey responses on 3 sites across the study area, resulting in 723 usable responses. Efficacy of individuals’ livestock management varied between and within communities. This variation was partially explained by normative and control beliefs regarding livestock management. Individual livestock managers’ self-reported management issues were often an accurate reflection of their practical management difficulties. Psychological norms, control beliefs, and attitudes differed among sites, and these differences partially explained patterns associated with conflict (i.e., variation in livestock management behavior). Thus, we conclude that a one-size-fits-all approach to improving livestock management and reducing human–predator conflict is not suitable.  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