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   809篇
  免费   59篇
  国内免费   59篇
安全科学   70篇
废物处理   14篇
环保管理   239篇
综合类   321篇
基础理论   122篇
环境理论   2篇
污染及防治   27篇
评价与监测   13篇
社会与环境   93篇
灾害及防治   26篇
  2023年   4篇
  2022年   9篇
  2021年   21篇
  2020年   15篇
  2019年   25篇
  2018年   23篇
  2017年   39篇
  2016年   38篇
  2015年   33篇
  2014年   31篇
  2013年   54篇
  2012年   59篇
  2011年   49篇
  2010年   38篇
  2009年   38篇
  2008年   32篇
  2007年   44篇
  2006年   38篇
  2005年   27篇
  2004年   25篇
  2003年   36篇
  2002年   31篇
  2001年   21篇
  2000年   26篇
  1999年   24篇
  1998年   11篇
  1997年   15篇
  1996年   6篇
  1995年   8篇
  1994年   13篇
  1993年   7篇
  1992年   2篇
  1991年   4篇
  1990年   3篇
  1988年   2篇
  1987年   7篇
  1986年   2篇
  1983年   6篇
  1982年   2篇
  1981年   8篇
  1980年   7篇
  1979年   8篇
  1978年   4篇
  1977年   5篇
  1976年   6篇
  1975年   4篇
  1974年   1篇
  1973年   3篇
  1972年   3篇
  1971年   7篇
排序方式: 共有927条查询结果,搜索用时 115 毫秒
281.
我国投资拉动的宏观成本分析   总被引:3,自引:0,他引:3  
我国多年来坚持的是一种高投入、高消耗的投资拉动型增长模式.而高投资高增长则更多地以宏观成本积累为代价。未来投资的增速不仅取决于经济增长的预期目的.更多的取决于资金、技术、资源支撑和环境容量。通过对高投资高增长发展模式的高宏观成本分析,提出了贯彻落实科学发展观、促进经济方式转变的若干结论性建议。  相似文献   
282.
协调贸易与环境的最佳途径——环境成本内部化   总被引:4,自引:0,他引:4  
面对经济发展带来人类福利增加的同时所产生的日益严重的环境污染问题。国际贸易被指责为环境质量下降的原因之一.甚至连国际贸易自由化的原则也受到质疑。围绕贸易与环境可否协调以及如何协调的问题.由环境保护与贸易自由化在理论和实践中的冲突引出贸易与环境之间存在着复杂的相互作用;并通过进一步的经济学分析得出结论:环境问题的根源并不是国际贸易。而是环境成本的外部性造成的市场失灵,而国际贸易只是加重了这种市场失灵。二者可以协调发展。环境成本内部化是解决这一问题的最佳手段。通过环境成本内部化可以达到环境资源的合理配置并最终实现可持续发展。  相似文献   
283.
ABSTRACT: Efficiency implications of seasonal pricing, uniform pricing, and optimal seasonal pricing with metering costs are analyzed qualitatively using classical optimization technique. The first two schemes are special cases of the last pricing scheme. A nonlinear-integer programming model is formulated for a case study application to Salt Lake City to examine the feasibility of seasonal pricing. The analysis indicates that uniform pricing is preferable unless metering costs are substantially lower than present levels.  相似文献   
284.
面向市场经济的中国水资源可持续利用策略   总被引:9,自引:0,他引:9  
中国是一个人口大国,人均可利用水资源量少,水资源利用的低效和浪费以及污染问题进一步加剧了水资源的供需矛盾。在中国的市场经济制度渐趋发展的形势下,要实现水资源的可持续利用,就必须突破过去计划经济体制下的不合理框架,更多地使用符合市场经济要求的价格机制。市场模式和管理体制。  相似文献   
285.
ABSTRACT: Calgary, the fastest growing city in Canada, is about to expand its urban water supply facilities in order to meet peak summer demands. Most of Calgary's residential water is sold by flat rate. The effect of this pricing policy on peak and average demands is discussed. The true marginal cost of peak capacity from the new expansion is calculated. The effect of a proposed metering program on capacity expansion requirements is computed. It is concluded that metering should preceed the next capacity expansion.  相似文献   
286.
潮白河顺义段断流的生态损失评估   总被引:1,自引:0,他引:1  
潮白河是北京市最重要的自然湿地之一。由于人类不合理的开发利用,河流生态系统严重退化,其中顺义段河道从1999年断流至今。在实地调研的基础上,建立了一套河道断流对区域社会-经济-自然复合生态系统发展造成的综合损失的定量评估方法体系,从社会-经济系统的年度产值损失、用于治理断流河道的年度恢复费用、断流河道非使用价值的年度损失三个方面,评价潮白河顺义段断流对研究区域造成的生态损失。研究结果表明,潮白河顺义段断流对研究区域复合生态系统造成的年度生态损失达8786.5万元,1995—2005年的十年间生态损失总值达87865万元。  相似文献   
287.
中国是一个秸杆资源浪费十分严重的国家,每年都有大量秸杆被白白烧掉。秸杆焚烧不仅造成巨大的资源浪费,而且还引起了严重的环境污染问题。文章运用成本-效益分析法对农户的秸杆焚烧问题进行了经济学分析,并运用该方法对河南省信阳市的秸杆处置情况进行实证描述,得出了“焚烧秸杆,是农户在通常的秸杆处置方法处置成本过高情况下不得已的选择;劳动力机会成本越来越高,是秸杆处置成本居高不下的主要原因;而运输距离遥远导致运输成本过高,是秸杆只能就地焚烧的又一重要原因”的结论。  相似文献   
288.
The RAMseS project, under the European Commission's 6th Framework Program, is dedicated to the construction and test of low-power operations based on photovoltaic power and a multipurpose electric vehicle. In the present study, the life-cycle costs and economical indices for the vehicle during its life span were assessed, compared to those of a standard internal combustion engine vehicle (ICEV). The results indicated that the life-cycle costs for the RAMseS vehicle and the ICEV are the same for a fuel unit price of 1.8 €/L. Also, the levelized cost of energy (LCE) for the RAMseS vehicle, was found to be 2.13 €/kWh, while RAMseS LCE, without EV taken into account, was shown to be 0.62 €/kWh. The RAMseS payback period (PBP) without EV taken into account was calculated to be 9 years if the value of the produced energy becomes at least 0.35 €/kWh. Vehicles that use PV systems as their power source, such as RAMseS, will be economically effective for fuel costs higher than 1.8 €/L, but considering the environmental benefits that are provided in terms of external costs, they can be considered profitable even at lower fuel costs.  相似文献   
289.
Introduction: In-transport vehicles often leave the travel lane and encroach onto natural objects on the roadsides. These types of crashes are called run-off the road crashes (ROR). Such crashes accounts for a significant proportion of fatalities and severe crashes. Roadside barrier installation would be warranted if they could reduce the severity of these types of crashes. However, roadside barriers still account for a significant proportion of severe crashes in Wyoming. The impact of the crash severity would be higher if barriers are poorly designed, which could result in override or underride barrier crashes. Several studies have been conducted to identify optimum values of barrier height. However, limited studies have investigated the monetary benefit associated with adjusting the barrier heights to the optimal values. In addition, few studies have been conducted to model barrier crash cost. This is because the crash cost is a heavily skewed distribution, and well-known distributions such as linear or poison models are incapable of capturing the distribution. A semi-parametric distribution such as asymmetric Laplace distribution can be used to account for this type of sparse distribution. Method: Interaction between different predictors were considered in the analysis. Also, to account for exposure effects across various barriers, barrier lengths and traffic volumes were incorporated in the models. This study is conducted by using a novel machine-learning-based cost-benefit optimization to provide an efficient guideline for decision makers. This method was used for predicting barrier crash costs without barrier enhancement. Subsequently the benefit was obtained by optimizing traffic barrier height and recalculating the benefit and cost. The trained model was used for crash cost prediction on barriers with and without crashes. Results: The results of optimization clearly demonstrated the benefit of optimizing the heights of road barriers around the state. Practical Applications: The findings can be utilized by the Wyoming Department of Transportation (WYDOT) to determine the heights of which barriers should be optimized first. Other states can follow the procedure described in this paper to upgrade their roadside barriers.  相似文献   
290.
Setting a baseline for carbon stock changes in forest and land use sector mitigation projects is an essential step for assessing additionality of the project. There are two approaches for setting baselines namely, project-specific and regional baseline. This paper presents the methodology adopted for estimating the land available for mitigation, for developing a regional baseline, transaction cost involved and a comparison of project-specific and regional baseline. The study showed that it is possible to estimate the potential land and its suitability for afforestation and reforestation mitigation projects, using existing maps and data, in the dry zone of Karnataka, southern India. The study adopted a three-step approach for developing a regional baseline, namely: (i) identification of likely baseline options for land use, (ii) estimation of baseline rates of land-use change, and (iii) quantification of baseline carbon profile over time. The analysis showed that carbon stock estimates made for wastelands and fallow lands for project-specific as well as the regional baseline are comparable. The ratio of wasteland Carbon stocks of a project to regional baseline is 1.02, and that of fallow lands in the project to regional baseline is 0.97. The cost of conducting field studies for determination of regional baseline is about a quarter of the cost of developing a project-specific baseline on a per hectare basis. The study has shown the reliability, feasibility and cost-effectiveness of adopting regional baseline for forestry sector mitigation projects.
N. H. RavindranathEmail:
  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