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   756篇
  免费   105篇
  国内免费   62篇
安全科学   248篇
废物处理   8篇
环保管理   234篇
综合类   222篇
基础理论   70篇
环境理论   5篇
污染及防治   19篇
评价与监测   26篇
社会与环境   46篇
灾害及防治   45篇
  2024年   1篇
  2023年   12篇
  2022年   18篇
  2021年   26篇
  2020年   21篇
  2019年   32篇
  2018年   27篇
  2017年   48篇
  2016年   46篇
  2015年   40篇
  2014年   40篇
  2013年   40篇
  2012年   47篇
  2011年   69篇
  2010年   40篇
  2009年   62篇
  2008年   34篇
  2007年   54篇
  2006年   44篇
  2005年   25篇
  2004年   29篇
  2003年   17篇
  2002年   18篇
  2001年   13篇
  2000年   15篇
  1999年   17篇
  1998年   11篇
  1997年   12篇
  1996年   6篇
  1995年   10篇
  1994年   9篇
  1993年   8篇
  1992年   6篇
  1991年   2篇
  1990年   1篇
  1989年   4篇
  1988年   3篇
  1987年   1篇
  1985年   1篇
  1984年   1篇
  1983年   1篇
  1982年   3篇
  1981年   2篇
  1980年   2篇
  1977年   2篇
  1974年   1篇
  1973年   1篇
  1972年   1篇
排序方式: 共有923条查询结果,搜索用时 62 毫秒
311.
为提高综掘巷道的掘进效率、改善支护工艺,设计一种用于综掘巷道迎头顶板支护的迈步式超前支护装备。通过对装备工作原理的分析,建立其三维模型。为检验装备的支护效果,设计了支护特性实验方案,构建实验平台,基于实验平台进行了双组支撑状态下的支护实验。实验结果表明:顶板上离固支边越远处动态位移变形量越大,接触力波动也越大; 在双组支撑状态下,顶板变形量最大达到9 mm,接触力最大幅值达到5.84 kN,位置均为顶板纵向中线位置处,在被支护后,该位置最迟趋于稳定; 在双组支撑状态下,顶板变形及接触力经历2~3 s波动后都将趋于平稳; 超前支护装备对顶板的稳定性能起到良好的控制作用,能提高顶板的安全性,为后续产品研发及工业实验提供依据。  相似文献   
312.
China's Du Jiang Yan Irrigation Project, dating back to 256 BC, is one of the world's earliest water resources projects. Although it has been benefiting the Sichuan Basin area for over 2000 years, it is facing increasing problems due to ecological deterioration, over-exploitation from local industries and agriculture, suboptimal resource allocation arising from supply and demand mismatches, and an aging infrastructure. The traditional water resources development model is no longer appropriate for current and future needs of the area. Therefore, a sustainable development framework is envisioned in which population, economy and environment coexist in harmony. Within this framework, major strategies, such as construction and renovation of infrastructure, promotion of water conserving irrigation through non-engineering measures, pollution control and ecological improvements, restructuring of management entities and exploration of new funding sources, are proposed. An evaluation system is also introduced to assess the degree of sustainability and to monitor progress towards a high level of sustainable development.  相似文献   
313.
Risk communication in flood incident management can be improved through developing hydrometeorological and engineering models used as tools for communicating risk between scientists and emergency management professionals. A range of such models and tools was evaluated by participating flood emergency managers during a 4-day, real-time simulation of an extreme event in the Thamesmead area in the Thames estuary close to London, England. Emergency managers have different communication needs and value new tools differently, but the indications are that a range of new tools could be beneficial in flood incident management. Provided they are communicated large model uncertainties are not necessarily unwelcome among flood emergency managers. Even so they are cautious about sharing the ownership of weather and flood modelling uncertainties.  相似文献   
314.
Flood management policies in the United States rely on scientific information about the frequency and intensity of extreme precipitation and runoff. Yet, the available information is inherently uncertain because of the complexity of meteorological and hydrological processes. In mountainous areas, flood risk can vary greatly even within short distances depending on local climate, topography, soil characteristics, and land use. This paper describes two Colorado cases in which policy makers were presented with conflicting scientific estimates: revision of the Fort Collins floodplain map and modification of the Cherry Creek Dam. The case studies demonstrate that uncertainty can have substantial impacts on regulatory processes, public safety, and costs. The analysis considers the differing perspectives of various participants in the flood management processes, illustrating the interplay between uncertainties attributable to scientific issues and values issues. It suggests that attempts to provide a single “best” estimate do not necessarily meet the decision needs of all stakeholders. Conclusions indicate a need to improve communication about uncertainty when scientific estimates areprovided to decision makers. Furthermore, in highly controversial decisions, it may be necessary to reframe the discussion to consider the values issues raised by scientific uncertainty.  相似文献   
315.
《Environmental Hazards》2013,12(3):177-193
This paper presents the findings of a study that explored public support for wildfire mitigation programmes implemented in Peavine Métis Settlement, an Indigenous community located in Alberta, Canada. Data were collected in a community-based study using interviews, focus groups and participant observation over a 4-year period. Results showed that support for the wildfire mitigation programme was influenced by local leadership, economics, community capacity and land and home ownership. The communal nature of land and home ownership on the settlement influenced support for wildfire mitigation that was conducted by the settlement at both the residential and community levels. Employment opportunities available in the community for settlement members for wildfire mitigation activities also increased support for the local wildfire mitigation programme. A local Aboriginal leader skilled in wildfire mitigation and existing community capacity was also seen as vital to settlement member support for the programme.  相似文献   
316.
We present a general methodology for developing environmental emergency decision support systems (EEDSS) based on an Artificial Neural Network (ANN). We highlight the method for developing the system using an illustrative example of an unexpected atmospheric accident with an ANN prototype system for a district in Shanghai. The network architecture of the ANN is introduced. Then the development process and key technologies are addressed. The procedures for matching the environmental emergency decision support characteristics are as follows: (1) digitization (coding) of case information and emergency measures, in which the information of cases are divided into the input attributes and decision-making information, and standardized and digitized through the Feature Evaluation (FE) method and the Intensity Hierarchical (IH) method, respectively; (2) construction of environmental emergency ANN, in which Gradient Descent with Momentum and Adaptive Learning Rate (GDMALR) method (traingdx function), a modified back-propagation algorithm, is employed to do training; and (3) translation (decoding) of decision-making information, in which output data of ANN is interpreted into practical contingency measures with Translation Based on Conventional Import Ratios (TBCIR) method. The training features, time, errors, accuracy, and input attribute weights of the prototype system are analyzed. The usage of the prototype system is demonstrated through a hypothetical case. This article encounters the challenge of ANN’s own lack of training samples. We discuss to the concept of integrating Case-Based Reasoning (CBR), Genetic Algorithm (GA), and ANN to overcome this difficulty and form a technology system for generating useful decision support information for environmental emergency response.  相似文献   
317.
Although the prevalence of employees working within the same workplace or occupation with their spouse has increased, relatively little research has examined their experiences. On the basis of the boundary and conservation of resources (COR) theories, we argue that higher levels of work–family role integration among work‐linked couples will lead to higher levels of spousal support resources and lower levels of work–family conflict. This will, in turn, lead to lower emotional exhaustion among employees in a work‐linked relationship. Among two samples of employees in a variety of occupations, we found that being in a work‐linked relationship was associated with both higher spousal instrumental support as well as different forms of work–family conflict. The interaction between spousal support and work–family conflict was associated with emotional exhaustion. We discuss the implications of these findings for boundary and COR theories in terms of movement of resources across work–family boundaries and resource relevance in the strain process. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
318.
西安地裂缝是一种地区性的地质灾害,地裂缝的存在给西安地铁的设计和施工等带来一系列的难题和挑战.本文针对西安地铁1号线与F6地裂缝的交叉进行了支护结构设计的探讨分析,调查了F6地裂缝的活动规律和特点.在此基础上,建立了三维有限元计算模型,确定模型的加载方式,分析研究了地铁隧道在施工、支护阶段以及设计年限内最终沉降的结构受力与变形,从而确定了结构设计的方式以及布置形式.同时探讨了支护结构构造,给出了变形缝处结构协调地裂缝活动措施和方法,以期本研究对西安地裂缝带的地铁建设有一定参考.  相似文献   
319.
安全管理决策支持系统的管理控制框架探讨   总被引:1,自引:0,他引:1  
从安全管理的特性出发,用控制框图说明了安全管理控制系统的组成。在论述安全管理决策的内容及其最重。要的问题的过程中,提出了安全管理对象化的思想。利用6步描述方法解析了安全管理问题,并构建了安全决策支持系统的4 4模块化框架,为系统的研究与开发奠定基础。  相似文献   
320.
针对采空区稳定性分级的影响因素众多且关系复杂的特点,提出采用支持向量机理论对采空区稳定性进行分级。根据分级评价指标选取原则,选取岩体结构、地质构造、岩石的质量指标、地下可见水、地下水体、周边开采的影响、相邻空区的情况、工程布置、跨度、面积、高度、矿柱的尺寸及布置、埋藏深度和采空区的规格14个影响因子,建立了采空区稳定性评价指标体系,引入支持向量机理论,选择有向无环图方式构造多类分类器,得到采空区稳定性分级的支持向量机模型。将该模型用于山东黄金矿业西山矿区的25个采空区进行分级,并与未确知测度方法的分级情况  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