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   1660篇
  免费   481篇
  国内免费   157篇
安全科学   116篇
废物处理   88篇
环保管理   136篇
综合类   879篇
基础理论   305篇
污染及防治   617篇
评价与监测   43篇
社会与环境   44篇
灾害及防治   70篇
  2024年   19篇
  2023年   42篇
  2022年   80篇
  2021年   62篇
  2020年   41篇
  2019年   35篇
  2018年   52篇
  2017年   74篇
  2016年   96篇
  2015年   90篇
  2014年   122篇
  2013年   144篇
  2012年   147篇
  2011年   115篇
  2010年   109篇
  2009年   107篇
  2008年   118篇
  2007年   102篇
  2006年   86篇
  2005年   74篇
  2004年   32篇
  2003年   58篇
  2002年   55篇
  2001年   48篇
  2000年   48篇
  1999年   58篇
  1998年   50篇
  1997年   41篇
  1996年   40篇
  1995年   37篇
  1994年   22篇
  1993年   25篇
  1992年   20篇
  1991年   15篇
  1990年   5篇
  1989年   7篇
  1988年   11篇
  1987年   1篇
  1986年   5篇
  1985年   1篇
  1984年   1篇
  1982年   2篇
  1981年   1篇
排序方式: 共有2298条查询结果,搜索用时 0 毫秒
121.
为降低液体自燃温度测试过程中的操作危险,准确判定自燃现象发生及温度,减少繁琐的手工操作,参照ASTME659—78(2005)、GB/T21791-2008及GB/T21860-2008标准,设计了一套智能自燃温度测试系统。采用操作微机软件控制炉体升降温、自动进样泵进样、温度采集、自燃现象拍摄、尾气抽滤等过程,实现自燃温度测试从开始进样到吹扫尾气全流程的自动化;利用设计系统测试乙醇、丙酮等5种常见物质的自燃温度,测试结果与文献值的相对标准偏差不超过2.0%。结果表明所设计系统操作方便快捷、安全实用、结果准确。  相似文献   
122.
海域有机污染物优先排序和风险分类模糊评判系统   总被引:2,自引:2,他引:2  
本文提出了对区域性有机污染物优先排序和风险分类和定量评判系统:模糊评判系统。该评判系统以反映污染物的毒性,暴露水平和环境化学性质的7项碜数为指标,通过指标参数的标准化及模糊运算,获得有机污染优先排序和风险分类的定量结果。  相似文献   
123.
本文从不同方面和断代论述了中国东南地区的基底杂岩时代、性质、构造环境、边界变质条件、地球物理场及其反映的构造格局、断裂体系、中生代火山活动的基底构造及类型分区。在此基础上提出了东南地区的构造划分及构造演化阶段和格局。并提出了不同类型的地体及其分类、大陆裂解、增生的新概念。  相似文献   
124.
近年来随着水环境模拟领域的发展出现了较多水环境数学模型,目前日益成熟的WebGIS技术是使模型使用变得简单化和直观化的一大途径.是在通过Flex和ArcGIS Server搭建WebGIS系统平台的基础上,利用PHP进行WebGIS和水环境模拟模型的数据交互,实现系统平台和数值模型的松散耦合.用户在浏览器端进行模型输入条件的设置,模型在远程服务器端进行运行计算,反馈的模拟结果通过RIA在WebGIS中进行多元化动态展示.该方法对一般模型具有适用性,可降低模型使用门槛,提高模拟结果展示和分析能力.  相似文献   
125.
建设高校校园文化是发挥高校育人作用的重要工作,对全面推进素质教育和引导学生的全面发展都起着重要作用.本文就高校校园文化的概念、高校校园文化的作用、高校校园文化的建设要求与方法进行了论述,并提出了个人见解.  相似文献   
126.
生态系统完整性不仅反映了环境干扰下生态系统维持最优化运作和良性发展的能力,也反映了为人类社会提供有价值产品和服务的能力。本文以生态系统完整性的视角,从耗散结构和生态系统结构、过程、服务功能方面分析了岩溶生态系统的特点,表明岩溶生态系统完整性也是潜在脆弱的,随着生态的逐渐退化,生态系统完整性逐渐损失。作为人类作用胁迫下的终态,岩溶土地石漠化的发生和加剧代表着岩溶生态系统完整性的丧失,石漠化治理及生态恢复过程则是生态系统完整性逐渐恢复的过程。  相似文献   
127.
    
CuFe-SSZ-13 catalyst showed excellent performance in the selective catalytic reduction of NOx with NH3 (NH3-SCR) for diesel engine exhaust purification. To investigate the effect of preparation methods on NH3-SCR performance, Fe was loaded into one-pot synthesized Cu-SSZ-13 catalysts through solid-state ion-exchange (SSIE), homogeneous deposition precipitation (HDP) and liquid ion-exchange (IE), respectively. Three CuFe-SSZ-13 catalysts showed similar SO2 resistance, which was better than that of Cu-SSZ-13. The improvement was attributed to the protection of Fe species. Hydrothermal stability of three CuFe-SSZ-13 catalysts was significantly different, which was attributed to the state of active species caused by different preparation methods. Compared with the other two catalysts, more active species existed inside the zeolite pores of CuFe-SSZ-13SSIE. During hydrothermal aging, the aggregation of these active species in the pores caused the collapse of catalyst structure, ultimately leading to the deactivation of CuFe-SSZ-13SSIE. In contrast, Fe species was dispersed better on the surface over CuFe-SSZ-13IE, enhancing the hydrothermal stability of catalysts. Consequently, Fe loading effectively improved the resistance of SO2 and H2O over Cu-SSZ-13. For CuFe-SSZ-13, large amounts of active species located inside the zeolite pores are not beneficial for the hydrothermal stability.  相似文献   
128.
The paper presents a novel cleaner process for metal recovery from the Printed Circuit Board (PCB) waste sludge by assistance of ultrasound. The process can effectively recover heavy metals at low cost with high separation and recovery efficiency, produce high quality products and also achieve zero waste discharge with operation at industrial scale. With the PCB waste sludge containing (wet content) 3.14–4.85% copper and 3.71–4.23% iron, copper recovery efficiency of 95.2–97.5% and iron recovery efficiency of 97.1–98.5% were achieved, while the purity of copper sulfate produced by the process was 98.0% and the produced ferric chloride had a satisfied quality for using as a coagulant material for the plant on-site wastewater treatment. The process had been successfully scaled up to the industrial scaled applications in a heavy metal recovery plant in city of Huizhou, China for more than two years. The novel cleaner heavy metal recovery process has a great prospect on the applications of resources recovery and environmental protection practices.  相似文献   
129.
We conducted an experiment to study the interaction effects of Microcystis aeruginosa and Pseudomonas pseudoalcaligenes on off-flavors in an algae/bacteria co-culture system at three temperatures (24, 28 and 32°C). Gas chromatography–mass spectrometry was applied to measure off-flavor compounds dimethyl sulfide (DMS), dimethyl trisulfide (DMTS), 2-methylisoborneol, geosmin (GEO) and β-cyclocitral. During the lag phase of co-cultured M. aeruginosa (first 15 days), P. pseudoalcaligenes significantly increased the production of DMS, DMTS and β-cyclocitral at all three temperatures. In the exponential phase of co-cultured M. aeruginosa (after 15 days), M. aeruginosa became the main factor on off-flavors in the co-culture system, and β-cyclocitral turned to the highest off-flavor compound. These results also indicated that DMS, DMTS and β-cyclocitral were the main off-flavor compounds in our M. aeruginosa/P. pseudoalcaligenes co-culture system. Univariate analysis was applied to investigate the effects of M. aeruginosa and P. pseudoalcaligenes on the production of off-flavors. The results demonstrated that both M. aeruginosa and P. pseudoalcaligenes could increase the production of DMS and DMTS, while β-cyclocitral was mainly determined by M. aeruginosa. Our results also provide some insights into understanding the relationship between cyanobacteria and heterotrophic bacteria.  相似文献   
130.
This study investigated the bacterial regrowth in drinking water distribution systems receiving finished water from an advanced drinking water treatment plant in one city in southem China. Thirteen nodes in two water supply zones with different aged pipelines were selected to monitor water temperature, dissolved oxygen (DO), chloramine residual, assimilable organic carbon (AOC), and heterotrophic plate counts (HPC). Regression and principal component analyses indicated that HPC had a strong correlation with chloramine residual. Based on Chick-Watson's Law and the Monod equation, biostability curves under different conditions were developed to achieve the goal of HPC 100 CFU/mL. The biostability curves could interpret the scenario under various AOC concentrations and predict the required chloramine residual concentration under the condition of high AOC level. The simulation was also carded out to predict the scenario with a stricter HPC goal (≤50 CFU/mL) and determine the required chloramine residual. The biological regrowth control strategy was assessed using biostability curve analysis. The results indicated that maintaining high chloramine residual concentration was the most practical way to achieve the goal of HPC ≤ 100 CFU/mL. Biostability curves could be a very useful tool for biostability control in distribution systems. This work could provide some new insights towards biostability control in real distribution systems.  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