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   6293篇
  免费   431篇
  国内免费   1630篇
安全科学   471篇
废物处理   778篇
环保管理   1014篇
综合类   4332篇
基础理论   460篇
环境理论   2篇
污染及防治   1088篇
评价与监测   126篇
社会与环境   53篇
灾害及防治   30篇
  2024年   6篇
  2023年   43篇
  2022年   78篇
  2021年   125篇
  2020年   149篇
  2019年   118篇
  2018年   108篇
  2017年   113篇
  2016年   172篇
  2015年   206篇
  2014年   332篇
  2013年   400篇
  2012年   465篇
  2011年   463篇
  2010年   370篇
  2009年   422篇
  2008年   335篇
  2007年   544篇
  2006年   650篇
  2005年   493篇
  2004年   412篇
  2003年   411篇
  2002年   346篇
  2001年   307篇
  2000年   266篇
  1999年   249篇
  1998年   174篇
  1997年   137篇
  1996年   102篇
  1995年   97篇
  1994年   82篇
  1993年   56篇
  1992年   31篇
  1991年   25篇
  1990年   10篇
  1989年   5篇
  1988年   4篇
  1986年   8篇
  1984年   2篇
  1982年   3篇
  1981年   4篇
  1980年   3篇
  1978年   2篇
  1977年   2篇
  1975年   2篇
  1974年   3篇
  1973年   4篇
  1972年   3篇
  1971年   3篇
  1970年   2篇
排序方式: 共有8354条查询结果,搜索用时 875 毫秒
761.
ABSTRACT: Most of California's precipitation falls at the wrong place in the wrong season in relation to the water needs. Redistribution and regulation are essential. Aquifer systems – groundwater basins – can provide a share of the future cyclic storage regulation. There are some differences in management concepts in using a full basin in comparison with a partially dewatered basin. Legal, water quality, and physical impacts on aquifer systems, including subsidence, are concerns. Storage may be for the benefit of overlying water users or for distant areas. Extraction during dry periods or recharge methods will require careful planning. Existing rights and uses and equitable treatment of all parties must be assured. Financial compensation may be involved. Changes in methods of operation or degree of self-determination by affected water agencies will require committed watermanship to resolve. Legislation or amendments to organic acts may be needed but much can be accomplished within existing statutes. Environmental impacts which can be avoided by not using large surface storage sites are important. Energy for pumping will be a key consideration. About 40 percent of California is underlain by aquifer systems. This resource offers major potential in overcoming the maldistribution of natural water resources.  相似文献   
762.
Potential increase in fire hazard as a result of timber harvesting is a concern of forest managers throughout the United States. Treating fuels can help reduce unacceptable fire hazards. To evaluate alternative fuel treatments, managers need to know their effects on fire hazard. A decision analysis approach to estimating fire hazard in terms of expected burned area was applied to a watershed in the Siskiyou National Forest (Oregon). Three treatment alternatives (do nothing and two levels of yarding unmerchantable material) were evaluated, and the effects of the treatments were projected over a 90-yr period. Initially, the effects of applying a treatment are small. After 50 years of treatment, the most intense alternative can be expected to show almost a 50% reduction in burned area compared to no treatment. The procedure also estimates burned are by fire size and fire intensity classes. Managers may find this useful for estimating expected fire effects associated with a particular fuel treatment regime.  相似文献   
763.
Heavy metals in fly ash from municipal solid waste incinerators are present in high concentrations. Therefore fly ash must be treated as a hazardous material. On the other hand, it may be a potential source of heavy metals. Zinc, lead, cadmium, and copper can be relatively easily removed during the thermal treatment of fly ash, e.g. in the form of chlorides. In return, wet extraction methods could provide promising results for these elements including chromium and nickel. The aim of this study was to investigate and compare thermal and hydrometallurgical treatment of municipal solid waste fly ash. Thermal treatment of fly ash was performed in a rotary reactor at temperatures between 950 and 1050 °C and in a muffle oven at temperatures from 500 to 1200 °C. The removal more than 90% was reached by easy volatile heavy metals such as cadmium and lead and also by copper, however at higher temperature in the muffle oven. The alkaline (sodium hydroxide) and acid (sulphuric acid) leaching of the fly ash was carried out while the influence of temperature, time, concentration, and liquid/solid ratio were investigated. The combination of alkaline-acidic leaching enhanced the removal of, namely, zinc, chromium and nickel.  相似文献   
764.
邯郸市沁河水污染治理方案   总被引:1,自引:0,他引:1  
本文对邯郸市沁河水污染现状进行了调查分析,总结了城市内河治理经验,通过方案比较,推荐“清淤,护坡,建坝,分质截污,邯钢废水混凝沉淀处理”为沁河治理方案。  相似文献   
765.
The nexus between human rights and the environment is a key issue for climate policymakers and Indigenous peoples around the world. We combine national spatial, social and biological datasets from Australia to describe where Indigenous carbon projects are happening, why Indigenous people are participating, and how effective these schemes might be at marrying Indigenous co-benefit, biodiversity and carbon emission mitigation goals. Our study shows that many Indigenous people engage in carbon offset schemes as part of their broader cultural responsibility for landscapes, and that they seek to grow the relationship between social and ecological benefits. It also highlights the challenges associated with designing carbon offset schemes that address the impacts of climate change and respond to Indigenous peoples’ world views about what is required to sustain cultural-social-ecological systems.  相似文献   
766.
传统工业生产方式在可持续发展背景下面临严峻挑战,清洁生产应而生,它是持续利用资源,减少工业污染,保护环境的根本措施,本文就清洁生产在中国示范推广所产生的经济,社会及环境效益进行了综合论述。  相似文献   
767.
填料在自由水面人工湿地中的应用   总被引:4,自引:0,他引:4  
钟定胜  罗华铭 《环境与开发》2000,15(1):14-15,18
本文通过对深圳市某橡胶厂自行设计造的自由水面人工湿地的调查研究,分析了在人工湿地中采用填料代替植物的工作特性,并论证了土壤-植物-微笑一这样一个生态系统是传统自由水面湿地处理系统实现其处理污水功能的核心。  相似文献   
768.
769.
阐述了沈阳市沈河区环境噪声污染的现状和存在的问题,并提出了综合治理的对策。  相似文献   
770.
本文通过对国内外近几年有关电解铝含氟化氢工业尾气净化处理大量的参考文献的分析研究及国内外电解铝生产企业在尾气治理方面的技术应用和尾气净化装置运行状况的调研,结合自己的专业特长和工程经验,建立一套有关电解铝含氟化氢尾气在处理、净化氟化氢方面的技术方案,设计制作一套湿法氟化氢吸收中试装置,从工艺方案优化设计、安全运行、设备设计及选材、自动控制、建立相关的副产物检测方法和后续产物的综合利用等方面进行了研究和探讨。  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