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   8124篇
  免费   568篇
  国内免费   271篇
安全科学   1617篇
废物处理   138篇
环保管理   3070篇
综合类   2142篇
基础理论   812篇
环境理论   10篇
污染及防治   207篇
评价与监测   334篇
社会与环境   353篇
灾害及防治   280篇
  2023年   85篇
  2022年   112篇
  2021年   179篇
  2020年   243篇
  2019年   190篇
  2018年   165篇
  2017年   220篇
  2016年   307篇
  2015年   256篇
  2014年   316篇
  2013年   455篇
  2012年   450篇
  2011年   572篇
  2010年   387篇
  2009年   496篇
  2008年   359篇
  2007年   475篇
  2006年   473篇
  2005年   364篇
  2004年   402篇
  2003年   299篇
  2002年   282篇
  2001年   272篇
  2000年   271篇
  1999年   205篇
  1998年   131篇
  1997年   135篇
  1996年   109篇
  1995年   105篇
  1994年   49篇
  1993年   62篇
  1992年   57篇
  1991年   47篇
  1990年   33篇
  1989年   27篇
  1988年   34篇
  1987年   33篇
  1986年   27篇
  1985年   23篇
  1984年   27篇
  1983年   17篇
  1982年   22篇
  1981年   18篇
  1980年   24篇
  1979年   33篇
  1978年   21篇
  1975年   14篇
  1973年   14篇
  1972年   16篇
  1971年   14篇
排序方式: 共有8963条查询结果,搜索用时 265 毫秒
761.
浅谈安全生产标准化建设   总被引:2,自引:0,他引:2  
系统阐述了大冶有色金属公司安全生产标准化建设内容、安全生产指标制定准则、建设体系以及建设效果,为现代企业安全生产管理积累了经验,可供借鉴。  相似文献   
762.
论建立我国安全管理硕士教育制度   总被引:2,自引:0,他引:2  
论述了安全科学技术的地位和作用,我国安全科学与工程学科的特点,安全工程师必备的知识体系,培养安全工程专业人才的要求,目前安全工程人才培养与实际需要的差距,我国安全科学技术的前景和已有的多层次安全教育体系等,在此基础上,首次提议了建立我国的安全管理硕士(MSA)教育制度,以便满足高层次安全管理人才的迫切需要,同时,还探讨了MSA人才的基本培养方案,比较了MSA和MBA(工商管理硕士)的共同特征,提出MSA教育可以借鉴MBA教育的经验。  相似文献   
763.
国内外大城市防灾减灾管理模式的比较研究   总被引:4,自引:2,他引:4  
翟永梅  韩新  沈祖炎 《灾害学》2002,17(1):62-69
城市综合防灾减灾管理是城市管理的一个重要组成部分。上海综合减灾体系目前尚不够完善,城市抗灾能力仍较薄弱。本文通过对国外大城市减灾管理模式的比较和研究,分析了目前上海市减灾管理模式的现状和问题,提出了改进目前上海市灾害管理模式的措施建议。  相似文献   
764.
基于洪水灾害快速评估的承灾体易损性信息管理系统   总被引:5,自引:0,他引:5  
洪水灾害易损性信息管理系统是为了开展洪水灾害快速评估,对不同洪水灾害流域和同一洪水灾害流域中的不同地区、不同承灾体(财产分类)、不同致灾因子(水深和历时等)条件,以财产的损失率为核心的综合信息管理系统。本文介绍了洪水灾害易损性信息管理系统的开发与设计的基本原理,阐述了系统的总体结构框架和功能模块划分,并且在系统数据流程图的基础上,对损失率数据库等几个重要的模块进行了详细的分析与设计,给出了系统的部分运行结果。本系统在与GIS、遥感等空间技术结合后,能够高效地完成各种洪水灾害损失的快速评估与预测分析工作,同时,本系统亦可独立作为对区域洪水灾害易损性研究的数据基础和理论支撑。  相似文献   
765.
ABSTRACT: Simulated water quality resulting from three alternative future land‐use scenarios for two agricultural watersheds in central Iowa was compared to water quality under current and historic land use/land cover to explore both the potential water quality impact of perpetuating current trends and potential benefits of major changes in agricultural practices in the U.S. Corn Belt. The Soil Water Assessment Tool (SWAT) was applied to evaluate the effect of management practices on surface water discharge and annual loads of sediment and nitrate in these watersheds. The agricultural practices comprising Scenario 1, which assumes perpetuation of current trends (conversion to conservation tillage, increase in farm size and land in production, use of currently‐employed Best Management Practices (BMPs)) result in simulated increased export of nitrate and decreased export of sediment relative to the present. However, simulations indicate that the substantial changes in agricultural practices envisioned in Scenarios 2 and 3 (conversion to conservation tillage, strip intercropping, rotational grazing, conservation set‐asides and greatly extended use of best management practices (BMPs) such as riparian buffers, engineered wetlands, grassed waterways, filter strips and field borders) could potentially reduce current loadings of sediment by 37 to 67 percent and nutrients by 54 to 75 percent. Results from the study indicate that major improvements in water quality in these agricultural watersheds could be achieved if such environmentally‐targeted agricultural practices were employed. Traditional approaches to water quality improvement through application of traditional BMPs will result in little or no change in nutrient export and minor decreases in sediment export from Corn Belt watersheds.  相似文献   
766.
ABSTRACT: A National Pilot Project (NPP) on Livestock and the Environment was initiated in 1992 to help provide solutions to environmental problems associated with livestock production. A major development of the NPP was the Comprehensive Economic and Environmental Optimization Tool‐Livestock and Poultry (CEEOT‐LP), an integrated modeling system designed to produce economic and environmental indicators for alternative policy scenarios applied to intensive livestock production watersheds. The system consists of a farm‐level economic model (FEM) and two environmental models: the field‐scale APEX model and the watershed‐level SWAT model. To date, CEEOT‐LP has been applied to two watersheds in Texas and one in Iowa. Predicted reductions in P losses for two P‐based manure application rate scenarios, relative to baseline conditions, ranged from ?4 to ?54 percent across the three watersheds; however, N loss impacts ranged from a decrease of 34 percent to an increase of 79 percent. For five other alternative scenarios that were simulated for only one watershed, N and P loss impacts ranged between a reduction of 78 percent to an increase of 20 percent. Aggregate watershed‐level economic impacts of the seven scenarios spanned a spectrum of a 27 percent decrease to a 25 percent increase in profit, relative to the baseline.  相似文献   
767.
ABSTRACT: Watershed stewardship activities throughout North America have evolved into a process that requires more involvement in planning and decision making by community stakeholders. Active involvement of all stakeholders in the process of watershed stewardship is dependent on effective exchange of information among participants, and active involvement of a wide range of stakeholders from “communities of place” as well as those from “communities of interest.” We developed a map‐based stream narrative tool as a means to: (a) assemble a wealth of incompletely documented, “traditional” ecological or natural history observations for rivers or streams; and (b) promote a higher level of active involvement by community stakeholders in contributing to information‐based, watershed management. Creation of stream narratives is intended for use as a tool to actively engage local stakeholders in the development of a more comprehensive information system to improve management for multiple stewardship objectives in watersheds. Completion of map‐based stream narrative atlases provides a valuable supplement to other independent efforts to assemble observations and knowledge about land‐based natural resources covering entire watersheds. We are confident that completion of stream narrative projects will make a valuable addition to the information and decision making tools that are currently available to the public and resource agencies interested in advancing the cause of community‐based approaches to watershed and ecosystem management.  相似文献   
768.
ABSTRACT: Operations of a dense raingage network in the Chicago area since 1989 provided data to assess the temporal and spatial distributions of heavy rainstorms. The 12‐year average was 4.4 storms per year, 40 percent more than in the 1948 to 1980 period, reflecting an ongoing Midwestern increase in heavy rains. The total rainfall from the 53 heavy rainstorms maximized over the city, reflecting previous observations that the influence of the city and Lake Michigan on the atmosphere causes an increase in heavy rains. Impacts from the record high number of eight storms in 2001 revealed that efforts to control flooding including the Deep Tunnel system, had reduced street and basement flooding in the moderate intensity storms, but the two most intense storms, each with 100‐year rainfall values, led to excessive flooding and a need to release flood waters into Lake Michigan. Results suggest continuing increases in the number of heavy rainstorms in future years, which has major implications for water managers in Chicago and elsewhere.  相似文献   
769.
ABSTRACT: In Yegua Creek, a principal tributary of the Brazos River in Texas, surveys of a 19 km channel reach downstream of Somerville Dam show that channel capacity decreased by an average of 65 percent in a 34 year period following dam closure. The decrease corresponds with an approximately 85 percent reduction in annual flood peaks. Channel depth has changed the most, decreasing by an average of 61 percent. Channel width remained stable with an average decrease of only 9 percent, reflecting cohesive bank materials along with the growth of riparian vegetation resulting from increased low flows during dry summer months. Although large changes in stream channel geometry are not uncommon downstream of dams, such pronounced reductions in channel capacity could have long‐term implications for sediment delivery through the system.  相似文献   
770.
ABSTRACT: This paper outlines a sound, practical approach for making more informed decisions about environmental policy choices. It emphasizes the importance of using a structured decision process to specify and organize values, use these values to create alternatives, and assess tradeoffs to help achieve a desired balance across key objectives. Although these decision making steps are based on common sense, they are often neglected or poorly carried out as part of the complex evaluations of natural resource options. We discuss several reasons for this frequent neglect of decision making principles and provide examples from recent water use planning projects to demonstrate some of the benefits of using a structured, decision focused approach: new and better solutions, increased and more productive participation by stakeholders, and greater defensibility and acceptance of the resource management evaluation process and its conclusions.  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