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   8268篇
  免费   975篇
  国内免费   1711篇
安全科学   1586篇
废物处理   113篇
环保管理   1166篇
综合类   4604篇
基础理论   1429篇
污染及防治   508篇
评价与监测   367篇
社会与环境   747篇
灾害及防治   434篇
  2024年   57篇
  2023年   188篇
  2022年   347篇
  2021年   395篇
  2020年   384篇
  2019年   320篇
  2018年   268篇
  2017年   405篇
  2016年   418篇
  2015年   448篇
  2014年   362篇
  2013年   463篇
  2012年   669篇
  2011年   732篇
  2010年   575篇
  2009年   613篇
  2008年   441篇
  2007年   513篇
  2006年   532篇
  2005年   395篇
  2004年   294篇
  2003年   297篇
  2002年   274篇
  2001年   220篇
  2000年   212篇
  1999年   174篇
  1998年   151篇
  1997年   128篇
  1996年   117篇
  1995年   101篇
  1994年   90篇
  1993年   67篇
  1992年   60篇
  1991年   31篇
  1990年   24篇
  1989年   26篇
  1988年   22篇
  1987年   19篇
  1986年   18篇
  1985年   9篇
  1984年   12篇
  1981年   12篇
  1980年   15篇
  1979年   12篇
  1978年   9篇
  1974年   3篇
  1973年   3篇
  1972年   4篇
  1971年   9篇
  1970年   5篇
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
991.
河网水质模型研究进展   总被引:1,自引:0,他引:1  
纵观水质模型的研究、应用及相关科学的发展,本文针对现有的水质模型做了分析评价,简要介绍了河网水质模型的未来研究趋势,并提出了几点建议。  相似文献   
992.
关于行驶中的车辆在交通系统各因素作用下的行驶安全性评价,在现有交通系统四大要素的基础上加入车辆行驶状态,构成"人-车-环境-路-车辆行驶状态"5要素。并对各要素评价指标的选定做了细致的筛选,建立了车辆行驶安全性评价指标体系。其中"人-车-环境-路"因素采用打分的形式确定其参数的分值,并利用层次分析法(AHP)计算各参数权重来构建模型的;"车辆行驶状态"因素则是引入加速度干扰的定义,建立基于道路结构的加速度干扰模型。最后,运用层级分析法建立了总的车辆行驶安全评价模型。  相似文献   
993.
活性污泥法水处理过程是一个复杂的生化反应过程,伴随有物理化学反应、生化反应、相变过程及物质与能量的转化和传递过程.通过对微生物动力学方程的讨论,进而建立动力学模型,比较了Monod方程和Contois方程分别来模拟有机碳在曝气条件下的生化去除过程.模型主要预测底物浓度、溶解氧、微生物增长等引起的系统响应,为污水处理厂的运行提供指导.  相似文献   
994.
The present paper describes an effort for developing the total maximum daily load (TMDL) for phosphorus and a load reduction strategy for the Feitsui Reservoir in Northern Taiwan. BASINS model was employed to estimate watershed pollutant loads from nonpoint sources (NPS) in the Feitsui Reservoir watershed. The BASINS model was calibrated using field data collected during a 2-year sampling period and then used to compute watershed pollutant loadings into the Feitsui Reservoir. The simulated results indicate that the average annual total phosphorus (TP) loading into the reservoir is 18,910 kg/year, which consists of non-point source loading of 16,003 kg/year, and point source loading of 2,907 kg/year. The Vollenweider mass balance model was used next to determine the degree of eutrophication under current pollutant loading and the load reduction needed to keep the reservoir from being eutrophic. It was estimated that Feitsui Reservoir can becoming of the oligotrophic state if the average annual TP loading is reduced by 37% or more. The results provide the basis on which an integrated control action plan for both point and nonpoint sources of pollution in the watershed can be developed.  相似文献   
995.
HAN阻隔防爆模型研究   总被引:1,自引:0,他引:1  
通过合理简化,利用多方气体状态方程,分别建立油品储运容器内可燃混合气体定容爆炸模型和装设阻隔防爆材料的油品储运容器内可燃混合气体爆炸模型,获得了阻隔防爆性能测试装置的燃爆容器抗爆设计限值,以及其在HAN阻隔防爆测试中燃爆容器试爆压力量级的控制下限值,同时,还给出HAN工程应用中容器留空率的计算方法,具有实际指导意义。  相似文献   
996.
Degraded air quality severely affects the health of citizens worldwide. The design of effective policies requires exploring public preferences for environmental and air quality policy instruments. Within the EC-FP7 SEFIRA project, using a choice experiment that stresses the trade-offs between attributes, this study investigates public preferences for environmental policy drivers in Italy. The main objective is to investigate the role played by selected policy drivers in determining policy preferences, complemented by elasticity and willingness to pay estimations. Preference heterogeneity and the role of socio-economic and attitudinal variables are explored with a latent class model over 2400 respondents sampled across Italy. The results allow identifying the different role played by the policy drivers across the classes. It emerged that most of the respondents (43%) are particularly sensitive to the cost components (cost sensitive respondents). The remaining respondents instead show an important sensitivity towards personal engagement in term of changes in the mobility and eating habits (lifestyle-change sensitive respondents). However, while 29% of them perceive these habits’ changes as negatively impacting on the personal utility, the other 28% of respondents translate the potential changes in the habitual behaviour of driving and eating as environmental and health benefits. Based on the modelling results, potential policies are simulated reporting respondents’ reaction to selected scenarios. It shows the crucial role played by reduction of premature deaths due to atmospheric pollution and measure cost.  相似文献   
997.
Our objective is to propose permit allocation schemes that lead to a fair distribution of the net abatement cost among regions in a global greenhouse gas (GHG) stabilization scenario. We use a detailed technology-based energy model, World-MARKAL, to determine efficient abatement decisions, and to calculate the regional gross abatement costs (before permit allocation and trading). The net abatement costs are then calculated and used for different permit allocation schemes.  相似文献   
998.
城市生态安全多层次灰色综合评价   总被引:3,自引:1,他引:2  
从城市生态安全的基本内涵出发,根据压力(pressure)-状态(state)-响应(response)模型,从生态系统压力、生态系统状况、生态系统响应3方面构建一个4层次的城市生态安全评价指标体系,运用灰色系统理论,构建了城市生态安全多层次灰色综合评价模型,并结合实例进行计算。评价结果与实际情况基本相符,表明该模型能有效地利用评价指标的信息,所给出的综合评价值既能用于描述所评价城市的生态安全状况,亦可对不同城市的生态安全状况进行比较,对更加科学合理地评价城市生态安全状况具有参考价值。  相似文献   
999.
In this paper, a dynamic model is developed in which coastal quality can be improved, restored, or maintained by two distinct user groups; this is done by identifying a context that ensures an increase (or a greater increase) in coastal quality in terms of specific features that characterise the user groups. The results demonstrate that integrated coastal management is always better than non-integrated management. Moreover, when there is a low degree of interest in maintaining the coastal use over time, only integrated community-based (CB) coastal management will increase the coastal quality. Even when the interest in maintaining the coastal use over time is high, an integrated CB approach is preferred if the willingness to pay for coastal improvements is great and the marginal inefficiency of investments in coastal improvements is low, because the coastal quality improves to a greater extent; if not, only an integrated top-down (TD) approach to coastal management will increase the coastal quality. These results suggest that developing countries should always adopt a CB approach; in contrast, developed countries should adopt a CB approach where local stakeholders attach direct values to the coastal quality, and adopt a TD approach where the general population attaches indirect (option or existence) values to coastal quality.  相似文献   
1000.
Effective water resources management programs have always incorporated detailed analyses of hydrological and water quality processes in the upland watershed and downstream waterbody. We have integrated two powerful hydrological and water quality models (SWAT and CE-QUAL-W2) to simulate the combined processes of water quantity and quality both in the upland watershed and downstream waterbody. Whereas the SWAT model outputs water quality variables in its entirety, the CE-QUAL-W2 model requires inputs in various pools of organic matter contents. An intermediate program was developed to extract outputs from SWAT at required subbasin and reach outlets and converts them into acceptable CE-QUAL-W2 inputs. The CE-QUAL-W2 model was later calibrated for various hydrodynamic and water quality simulations in the Cedar Creek Reservoir, TX, USA. The results indicate that the two models are compatible and can be used to assess and manage water resources in complex watersheds comprised of upland watershed and downstream waterbodies.  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