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   21324篇
  免费   2185篇
  国内免费   3487篇
安全科学   1834篇
废物处理   333篇
环保管理   4389篇
综合类   12750篇
基础理论   2344篇
环境理论   51篇
污染及防治   1172篇
评价与监测   2764篇
社会与环境   1157篇
灾害及防治   202篇
  2024年   77篇
  2023年   387篇
  2022年   543篇
  2021年   684篇
  2020年   773篇
  2019年   685篇
  2018年   585篇
  2017年   919篇
  2016年   954篇
  2015年   1112篇
  2014年   1076篇
  2013年   1537篇
  2012年   1525篇
  2011年   1583篇
  2010年   1262篇
  2009年   1230篇
  2008年   933篇
  2007年   1370篇
  2006年   1406篇
  2005年   1166篇
  2004年   973篇
  2003年   1043篇
  2002年   821篇
  2001年   764篇
  2000年   747篇
  1999年   528篇
  1998年   403篇
  1997年   363篇
  1996年   284篇
  1995年   255篇
  1994年   204篇
  1993年   166篇
  1992年   122篇
  1991年   94篇
  1990年   71篇
  1989年   42篇
  1988年   29篇
  1987年   34篇
  1986年   25篇
  1985年   17篇
  1984年   14篇
  1982年   20篇
  1981年   23篇
  1980年   21篇
  1979年   19篇
  1978年   22篇
  1977年   13篇
  1973年   12篇
  1972年   13篇
  1971年   13篇
排序方式: 共有10000条查询结果,搜索用时 21 毫秒
51.
Several wind tunnel experiments of tracer dispersion from reduced-scale landfill models are presented in this paper. Different experimental set-ups, hot-wire anemometry, particle image velocimetry and tracer concentration measurements were used for the characterisation of flow and dispersion phenomena nearby the models. The main aim of these experiments is to build an extensive experimental data set useful for model validation purposes. To demonstrate the potentiality of the experimental data set, a validation exercise on several mathematical models was performed by means of a statistical technique. The experiments highlighted an increase in pollutant ground level concentrations immediately downwind from the landfill because of induced turbulence and mean flow deflection. This phenomenon turns out to be predominant for the dispersion process. Tests with a different set-up showed an important dependence of the dispersion phenomena from the landfill height and highlighted how complex orographic conditions downwind of the landfill do not affect significantly the dispersion behaviour. Validation exercises were useful for model calibration, improving code reliability, as well as evaluating performances. The Van Ulden model proved to give the most encouraging results.  相似文献   
52.
对安全评价方法在危险废物处置建设项目环境风险评价中的运用进行初步探索。主要用"工艺过程风险因素分析表"对工艺过程潜在风险性识别;用蒙德法进行源项分析;用池火灾模型、蒸气云爆炸伤害模型对易燃、易爆物质的火灾、爆炸等重大事故后果进行计算,得出人员的伤亡半径和财产损失半径等参数,以便于判断风险的可接受水平。分析结果表明:采用安全评价方法对危险废物处置建设项目进行环境风险评价是适用的、可行的。  相似文献   
53.
环境质量评价的生物方法研究   总被引:1,自引:0,他引:1  
环境质量的生物评价是以生物对环境污染的表现为基础的.环境质量评价的生物方法包括环境指示生物的选择,环境质量生物评价指标的确定和环境质量分类等3个步骤.论述了环境污染的生物表现,提出了选择环境指示生物的原则,给出了环境质量生物评价的3类指标,建立了环境质量4级分类体系.  相似文献   
54.
Mycorrhiza is the main spatial and temporal linkage between different constituents in a forest ecosystem. The functional compatibility and stress tolerance of ectomycorrhizal types is species specific, and therefore the information on the ectomycorrhizal community structure can add to the understanding of processes in forest ecosystems and can also be applied as tools for bioindication of pollution stress in forest soils. We have studied the effects of pollution (N and S) on trees and forest soils by: (1) quantification of ECM types diversity as in situ indicators in forest stands, (2) determination and quantification of pollution-sensitive or -insensitive ECM types as passive monitors, (3) root growth and development of ECM on nonmycorrhizal spruce seedlings, planted at the studied sites (active monitors), and (4) ECM infection (a bioassay based on mycorrhizal inoculum potential) of seedlings in an experimental set-up as ex situ testers. ECM species richness for Norway spruce trees (Picea abies) showed higher values in unpolluted sites than in polluted ones, while the differences were not significant for European beech trees (Fagus sylvatica). As pollution-sensitive or -insensitive ECM species in spruce forests, we suggest Hydnum rufescens (sensitive) and Paxillus involutus (unsensitive). Mycorrhizal potential in Norway spruce seedlings as a bioassay for soil N and S pollution was effective, and is suggested as an additional, standardized and widely comparable system in bioindication of soil pollution.  相似文献   
55.
兰州市大气污染特征与污染预报技术研究   总被引:4,自引:2,他引:2  
结合兰州市大气污染特征,采用国际上较为先进的污染预报模式,分别建立了实时资料与数值产品相结合的实用统计预报模型.其系统预报结果准确程度较好,实用性强,时研究兰州市大气污染来源及政府决策都起着重要的作用.  相似文献   
56.
BACKGROUND: The Yangtze Delta is one of the most developed regions in China and includes Shanghai, eight cities in Jiangsu province and eight cities in Zhejiang province. Meat consumption in this region has increased with economic growth, and most of the consumed meat is produced locally. The water quality of surface waters has deteriorated in recent years. An example was the huge blue-green algae bloom in Tai Lake in late May 2007, which affected millions of people's daily drinking water. However, animal husbandry is considered to be one of the main pollution sources. METHODS: Pollutants (NH3-N, total phosphorus (TP), and total nitrogen (TN)) excreted by livestock and poultry, and the resultant COD (chemical oxygen demand) and BOD (biochemical oxygen demand), were estimated using two different methods based on different data sets. RESULTS: The number of livestock and poultry has remained stable in the Yangtze Delta over the four years from 1999 to 2002, with the average number of pigs, cattle, sheep and poultry being 21.1 M, 0.4 M, 7.7 M and 597.6 M, respectively. Pollutants in livestock and poultry excreta estimated by Method I were: 0.12 Mt NH3-N, 0.11 Mt TP and 0.29 Mt TN, resulting in COD and BOD of 1.34 Mt and 1.30 Mt, respectively, while the estimations based on Method II were: 0.18 Mt NH3-N, 0.15 Mt TP and 0.40 Mt TN, resulting in COD and BOD of 1.95 Mt and 1.80 Mt, respectively. DISCUSSION: Pollutants excreted annually by livestock and poultry in the Yangtze Delta are estimated to be: 0.17 Mt NH3-N, 0.16 Mt TP and 0.42 Mt TN, giving rise to a COD of 1.86 Mt and a BOD of 1.72 Mt. Approximately 25% of this pollution was estimated to enter water bodies, which means that the annual pollutant load is 43,700 t NH3-N, 39,400 tTP, 104,600t TN with a COD of 465,000 tand a BOD of 430,100 t. Pollutants from animal husbandry were similar in magnitude to those from industrial wastewater. Pigs produced the most pollution, followed by poultry, cattle and sheep. The pollution load from animal husbandry in the Yangtze Delta is about twice the average level of the whole of China. CONCLUSIONS: Domestic wastewater was the main pollution source in the Yangtze Delta, followed by pollution from raising livestock and poultry and from industrial wastewater. The pollution load in Shanghai and Jiaxing were the greatest, followed by 7 cities of Jiangsu province (except Suzhou) and other cities of Zhejiang province and Suzhou. Pigs and poultry produced about 90% of the total pollutants from animal husbandry. RECOMMENDATIONS AND PERSPECTIVES: The local governments, especially in Shanghai and Jiaxing, should focus their attention on the pollution produced by livestock and poulrry. Controlling pollution from pigs and poultry will have the greatest impact in this region. Control of pollution will be facilitated by the development of large-scale livestock and poultry farming units and a shift away from small scale husbandry.  相似文献   
57.
浅论国家环境权   总被引:1,自引:0,他引:1  
随着全球环境的日益恶化和公民环保意识的不断增强,环境权理论迅速发展。国家环境权作为一项重要的环境权。在环境法理论逐步变革和权利内涵不断演进的趋势下,已成为法学界研究探讨的重要课题。通过分析国家环境权的国内、国际法律基础。论证了国家环境权的确立。利用类比的方法。阐述了国家环境权与其他宪法权利的不同之处。从权利义务的对等统一和国内国际两个层面。重新归纳了国家环境权的内容。初步构建了国家环境权的基本理论框架。  相似文献   
58.
Volunteer monitoring of natural resources is promoted for its ability to increase public awareness, to provide valuable knowledge, and to encourage policy change that promotes ecosystem health. We used the case of volunteer macroinvertebrate monitoring (VMM) in streams to investigate whether the quality of data collected is correlated with data use and organizers' perception of whether they have achieved these outcomes. We examined the relation between site and group characteristics, data quality, data use, and perceived outcomes (education, social capital, and policy change). We found that group size and the degree to which citizen groups perform tasks on their own (rather than aided by professionals) positively correlated with the quality of data collected. Group size and number of years monitoring positively influenced whether a group used their data. While one might expect that groups committed to collecting good-quality data would be more likely to use it, there was no relation between data quality and data use, and no relation between data quality and perceived outcomes. More data use was, however, correlated with a group's feeling of connection to a network of engaged citizens and professionals. While VMM may hold promise for bringing citizens and scientists together to work on joint conservation agendas, our data illustrate that data quality does not correlate with a volunteer group's desire to use their data to promote regulatory change. Therefore, we encourage scientists and citizens alike to recognize this potential disconnect and strive to be explicit about the role of data in conservation efforts.  相似文献   
59.
最优环境税:庇古法则与税制协调   总被引:2,自引:0,他引:2  
从经济学的角度对国外关于最优环境税的经典理论——庇古法则及近十年来研究的前沿内容——一般均衡模型等作出阐释,并在外部性理论的基础上通过一个一般均衡模型考察环境税的效率特性和在次优情形下最优环境税的决定因素。随后是对我国开征环境税的几点思考:环境税的课征范围应暂定为排放各种废水、废气(烟尘)和固体废弃物的行为。环境税税率的确定可以采用“反复迭代”的方法,即“环境效益优先,兼顾税收协调和收入分配等效应。”其他相关问题的处理,如环境税和其它政策手段的配合使用,环境税税收的使用等。  相似文献   
60.
合成麝香是一类近十多年才引起人们关注的有机污染物.合成麝香广泛分布于环境中.难降解,易生物富集,对水生生物和人体均呈现一定的生物毒性.文章对某一化妆品厂生产车闯内、外及工厂外的上、下风向大气中多环麝香进行了定性定量分析,结果表明,除ATⅡ之外,大气中检测出了五种多环麝香,其中作为对照点的上风向多环麝香总浓度为5.43ng/m3,而工厂室内、外及下风向的多环麝香浓度范围为17.25~5543.4ng/m3;气固分配实验研究发现,超过68.43%的多环麝香分布于气相中.  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