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   161篇
  免费   11篇
  国内免费   3篇
安全科学   42篇
环保管理   70篇
综合类   28篇
基础理论   10篇
污染及防治   8篇
评价与监测   5篇
社会与环境   11篇
灾害及防治   1篇
  2023年   2篇
  2022年   1篇
  2021年   3篇
  2020年   3篇
  2019年   4篇
  2018年   2篇
  2017年   7篇
  2016年   8篇
  2015年   6篇
  2014年   8篇
  2013年   12篇
  2012年   14篇
  2011年   11篇
  2010年   7篇
  2009年   13篇
  2008年   4篇
  2007年   11篇
  2006年   6篇
  2005年   2篇
  2004年   6篇
  2003年   4篇
  2002年   5篇
  2001年   4篇
  2000年   2篇
  1999年   5篇
  1998年   6篇
  1995年   3篇
  1994年   1篇
  1993年   1篇
  1992年   5篇
  1991年   1篇
  1990年   1篇
  1988年   2篇
  1986年   1篇
  1984年   1篇
  1980年   1篇
  1976年   1篇
  1975年   1篇
排序方式: 共有175条查询结果,搜索用时 0 毫秒
171.
我国环境管制、自主创新与FDI内含技术水平提升   总被引:3,自引:1,他引:2  
环境管制与技术创新对FDI内含技术水平的提升有着重大的影响。本文在对相关文献回顾的基础上,构建了一个包含环境管制与自主创新的分析模型,并利用近几年的数据实证检验了其对外商投资企业内含技术水平的影响。研究发现,我国的环境管制措施对外商投资企业内含技术水平的提高起到了显著的作用,而现阶段我国总体的自主创新能力对其影响则不明显;但是技术含量多、创新层次高的创新活动,对外商投资企业内含技术水平提升的促进效果十分显著。该研究结果具有重要的政策意义,即环境保护、自主创新与引进高技术含量的外资之间具有良性的互动效应。我国应该逐步提高环境管制水平,激励外商投资企业的技术创新和引进;进一步加强对技术含量高、具备核心竞争能力的创新活动的支持力度,实现环境效益提高与外资内含技术水平提升的均衡发展。  相似文献   
172.
A method is proposed for the equitable allocation of impacts of groundwater pumping on streamflow. The method is intended for cases in which the pumping activity of multiple entities has impacts on streamflow and these impacts are computed by perturbation. It is shown that when the response of streamflow to pumping is nonlinear, simple methods for impact calculation can fail. The proposed method is developed for the case when there are four entities that impact streamflow. The method relies on the calculation of impacts by perturbation of the simulation model from different base pumping levels. When four entities are evaluated, 16 runs of the simulation model are required. It is shown the proposed method produces estimated impacts for each individual entity that are equitable because they meet the requirement that the impacts of each entity sum to the total impacts of all entities acting together and the impacts attributed to each entity do not depend on the order of calculation. A brief example demonstrates the approach.  相似文献   
173.
We present the results of a replicated before‐after‐control‐impact study on 33 streams to test the effectiveness of riparian rules for private and State forests at meeting temperature criteria in streams in western Oregon. Many states have established regulatory temperature thresholds, referred to as numeric criteria, to protect cold‐water fishes such as salmon and trout. We examined across‐year and within‐year patterns of exceedance at control and treatment stream temperature probes. Determining whether an exceedance at the downstream end of a harvest was unambiguously related to harvest proved surprisingly difficult. The likelihood of a site exceeding its numeric criterion appeared related, in part, to the site's preharvest temperature range. Four control reaches as well as three preharvest treatment reaches exceeded their numeric criteria, necessitating additional analysis to evaluate timber harvest impacts. Nine percent of sites (3 of 33) both exceeded their numeric criteria and exhibited a potential harvest effect (16.7% of private sites [3 of 18], 0% of State sites [0 of 15]). After harvest, exceedances were typically observed in only the first of the two post‐harvest years. These findings highlight the importance of including temporal and spatial controls in temperature assessments of numeric criteria when the assessment's purpose is to determine whether exceedances are related to human activities.  相似文献   
174.
国内外对农药包装废弃物回收的主要做法与经验   总被引:1,自引:0,他引:1  
全面介绍了国内外有关农药包装废弃物回收与处理的相关法律及政策制度,分析了国内外目前对农药包装废弃物回收处理的具体做法。探讨了国内在农药包装废弃物回收处理中存在的问题,最后对农药包装废弃物的安全处置提出政策建议。  相似文献   
175.

Introduction

A state by year panel is analyzed to simultaneously explore the statistical correlation between state level traffic fatality rates and state level behavioral regulations regarding teen licensing, seat belt use, and driving under the influence (DUI) in a model that also controls for other correlates.

Method

By including measures of all three of these policies, the estimated policy effects should not be overstated due to underspecification bias. The panel includes the 48 contiguous U.S. states for the time period from 1999 through 2003. State fatality rates are measured as fatalities per million miles traveled. Measures of state policies regarding traffic safety related behavior are based on information gathered by the Insurance Institute for Highway Safety. Estimates are calculated via a time fixed effects model that uses the double-log form to allow for interaction effects between the independent variables.

Results

Least squares estimates indicate that, on average, more restrictive graduated teen licensing and DUI policies significantly reduce traffic fatality rates, while stricter seat belt enforcement policies have a statistically insignificant negative impact on fatality rates.  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