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   2265篇
  免费   159篇
  国内免费   703篇
安全科学   223篇
废物处理   73篇
环保管理   351篇
综合类   1499篇
基础理论   289篇
环境理论   1篇
污染及防治   431篇
评价与监测   53篇
社会与环境   192篇
灾害及防治   15篇
  2024年   9篇
  2023年   40篇
  2022年   84篇
  2021年   89篇
  2020年   105篇
  2019年   114篇
  2018年   86篇
  2017年   130篇
  2016年   146篇
  2015年   147篇
  2014年   133篇
  2013年   192篇
  2012年   192篇
  2011年   231篇
  2010年   143篇
  2009年   156篇
  2008年   114篇
  2007年   167篇
  2006年   132篇
  2005年   94篇
  2004年   78篇
  2003年   92篇
  2002年   74篇
  2001年   67篇
  2000年   71篇
  1999年   52篇
  1998年   37篇
  1997年   26篇
  1996年   17篇
  1995年   22篇
  1994年   14篇
  1993年   17篇
  1992年   16篇
  1991年   7篇
  1990年   2篇
  1989年   2篇
  1988年   4篇
  1987年   3篇
  1986年   2篇
  1985年   3篇
  1982年   1篇
  1981年   1篇
  1980年   2篇
  1979年   1篇
  1978年   1篇
  1977年   4篇
  1976年   1篇
  1974年   2篇
  1972年   1篇
  1971年   2篇
排序方式: 共有3127条查询结果,搜索用时 171 毫秒
601.
The feasibility of using a chemical reaction-based approach for evaluating and modelling the role of adsorption reactions in determining the geochernical confinement capacity of natural geological barriers is being studied as part of an on-going R & D programme. The confined superficial aquifer underlying the Centre de Stockage de l'Aube facility, a geological barrier for this site, has been used as a case study with the following aims. First, development of a site characterisation protocol and demonstration of its use to determine the principal geochemical characteristics of aquifer materials using batch experiments and to represent the information obtained in terms of a chemical model. The experimental results obtained for Ni2+ partitioning as a function of total Ni, pH, total Ca and total solid can be satisfactorily represented in terms of reactions with an ion exchange site and a single amphoteric surface hydroxyl site with ferrihydrite reaction constants. A second objective is the incorporation of the reactions in a coupled geochemistry/transport code, and to verify the applicability of the coupled code predictions for Ni2+ mass transfer by comparison with the results obtained during column tracer experiments. The breakthrough curve and equilibrium solid phase Ni loading, predicted by a one-dimensional coupled model for a column tracer experiment, agree closely with observed data.Additional studies are underway to reduce model conditionality, to extend the adsorption model to other analogue cations and anions, to incorporate the effect of natural organic matter and to take into consideration precipitation/dissolution of amorphous Fe surface phases.  相似文献   
602.
本文根据“价值工程”理论和“成本—效益”理论,在作者提出的防灾工程“功能函数”、“成本函数”、“价值函数”、“效益函数”等灾害经济学基本函数及数学模型的基础上,结合地质灾害防御工程实例,探讨了防灾工程经济效益的评价原理及方法。  相似文献   
603.
Estuaries and coastal lagoons are characterized by a strong spatial and temporal variability of physicochemical characteristics and productivity patterns. In these environments, the magnitude and direction of the ecological responses to inorganic nutrient increase (i.e. eutrophication) are difficult to predict. In the framework of the project, New Indicators of Trophic state and environmental quality of marine coastal ecosystems and transitional environments (NITIDA), we analysed benthic indicators of trophic state, ecosystem efficiency, and environmental quality in four different transitional environments. The trophic state of the sediments was assessed in terms of quantity and bioavailability of sediment organic C pools; ecosystem efficiency was determined in terms of the prokaryote efficiency in exploiting enzymatycally degraded organic C; environmental quality was determined in terms of meiofaunal diversity. Here, we provide a synopsis of the results obtained and a meta-analysis of the scores assessments obtained using the different ecological indicators of environmental quality and demonstrate that trophic state, ecosystem efficiency, and biodiversity in transitional ecosystems are closely linked. We conclude that the assessment of the environmental quality of transitional ecosystems should be based upon a battery of trophic state indicators and 'sensors' of ecosystem functioning, efficiency, and quality.  相似文献   
604.
US Energy Conservation and Efficiency: Benefits and Costs   总被引:1,自引:0,他引:1  
With increased energy conservation plus the adoption of diverse energy efficient technologies, the US economy could save about 32 quads or about 33% of its current energy consumption, if sound conservation energy use policies were implemented over approximately 10 years. This potential of 32 quads is slightly greater than the current US oil imports. The systems that have the greatest potential to provide major energy savings are transportation, residential energy use, and the food system. Not only saving energy has merit in itself, but it would save US citizens approximately $438 billion per year, helping support the US economy, a high standard of living, and energy security. In addition, this analysis suggests that reducing the $40 billion in taxpayer money spent on subsidies of the energy industries would further increase conservation.  相似文献   
605.
厚果含笑(Michelialacei)生长在供给6mmolL-1NO3-(高氮)和2mmolL-1NO3-(低氮)Hoagland溶液的盆栽土中,利用PAM-2100叶绿素荧光仪、Licor-6400LCF荧光叶室和WatersHPLC分别测定叶绿素a荧光参数和类胡萝卜素组分,研究氮营养对光系统II(PSII)光化效率和光或暗下热耗散过程的影响.结果表明,在自然光日进程中叶片的开启PSII反应中心的内在量子效率(Fv/Fm)随光辐射增强而降低.低氮叶片Fv/Fm较高氮叶片降低明显(P<0.05).低氮叶片表现较明显的光抑制现象,反映低氮叶片对光抑制比高氮叶片敏感.高氮叶片比低氮叶片有低的PSII光化效率(ΦPSⅡ,P<0.05).高氮叶片依赖光的ΔpH和叶黄素介导的热耗散效率(ΦNPQ)和光下热耗散速率(JNPQ)则较低氮叶片高(P<0.05),结果反映高氮营养增进光下热耗散效率和速率.高氮叶片的紫黄质(A) 玉米黄质(Z)和叶黄素循环色素的转换态(A Z/V A Z)则较低氮叶片高(P<0.05).高氮叶片有较高光下热耗散(NPQ)和相应较高的(A Z)或(A Z/V A Z),叶片通过叶黄素循环色素以热的形式耗散过剩能;而低氮叶片表现高的总荧光淬灭和暗下热耗散.充足氮叶片有较低的光化效率,增高了光呼吸,并通过增强通过叶黄素循环色素的大量耗散过剩能.结果显示,过量氮输入将降低植物光能利用效率.图6表3参28  相似文献   
606.
Water saving and developing water conservation society are the two key strategies both for wise water allocation and sustainable utilization. The paper analyses the connotation of water saving and water conservation society. Essentially, water saving means freeing up water from non-beneficial uses and providing it to some more productive uses. Basic principles for setting indicator are presented by providing efficient use of water, considering social issues and ecological protection. An integrated assessing water saving system aiming at more sustainable and efficient consumption is given considering unbalanced social and economic development in regions and basins. The hierarchy indicator system provides qualified tools to the practice of water conservation and evaluates the value for water conservation society construction.  相似文献   
607.
以中国29个省市自治区为研究对象,并以2001~2015年PM2.5年度均值作为衡量霾污染的指标,构建了全要素能源效率对中国霾污染影响的空间杜宾模型.研究表明:中国绝大部分省市的霾污染演变趋势具有倒"U"的特点,这说明中国的霾污染在2001~2015年间经历了先上升后下降的总体变化趋势;无论是采用地理相邻权重还是经济权重,中国省际间的霾污染均存在显著空间集聚效应,这揭示霾污染的治理与控制需要地区间建立恰当的合作机制,避免出现"损人利己"现象;在对一系列经济社会因素控制的基础上,全要素能源效率对霾污染存在显著的负向影响并且具有显著的空间溢出效应,这表明全要素能源效率的提高不仅会显著降低本地区的霾污染水平,还将对周边地区的霾污染产生显著的负向影响;分解方程结果显示,技术进步和技术效率对霾污染的负向效应显著,并且技术进步的直接效应大于技术效率,但两者的间接效应均显著大于直接效应,这揭示了技术扩散对霾污染具有重要的潜在促降效应.因此,在治理霾污染的过程中,要通过不断优化能源结构和开发新能源技术以发挥全要素能源效率的减霾效果,以及通过地区间的交流与合作发挥技术扩散效应在霾污染治理中的作用.  相似文献   
608.
1IntroductionAsanunrenewablemineralresource,phosphorusisoneoftheimportantesentialelementsforlivingbeings.Phosphorushasmadeagr...  相似文献   
609.
研究了新型树NKY对7种水溶性染料的静态吸附特性,结果表明,该树脂对水溶性染料的吸附具有特性效,通过三常数方程非线性回归实验数据可求出吸附过程的△G^0,说明NKY对染料的第一层吸附为物理和化学作用并存在的过程,多层吸附为典型的物理吸附。由分民比和温度关系曲线可求得△H^0,推导出的标准自由熵为正值,说明吸附是自发进行的。  相似文献   
610.
以Hg(NO3)2、Cu(NO3)2水溶液为模拟工业废水,以侧链具N、S配位基的网状聚合物冠醚为吸附剂,研究了聚合物冠醚对HP(2+)、Cu(2+)的吸附性能。讨论了溶液温度、pH值、金属离子浓度及时间对吸附性能的影响,该聚合物冠醚对Hg(2+)具有较高的吸附容量和较快的吸附速度。  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