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   637篇
  免费   104篇
  国内免费   62篇
安全科学   269篇
废物处理   7篇
环保管理   157篇
综合类   197篇
基础理论   47篇
环境理论   5篇
污染及防治   12篇
评价与监测   20篇
社会与环境   42篇
灾害及防治   47篇
  2024年   1篇
  2023年   13篇
  2022年   18篇
  2021年   25篇
  2020年   23篇
  2019年   31篇
  2018年   25篇
  2017年   47篇
  2016年   40篇
  2015年   41篇
  2014年   39篇
  2013年   48篇
  2012年   47篇
  2011年   54篇
  2010年   37篇
  2009年   45篇
  2008年   23篇
  2007年   46篇
  2006年   40篇
  2005年   23篇
  2004年   24篇
  2003年   15篇
  2002年   16篇
  2001年   11篇
  2000年   11篇
  1999年   11篇
  1998年   6篇
  1997年   8篇
  1996年   5篇
  1995年   6篇
  1994年   6篇
  1993年   6篇
  1992年   5篇
  1989年   1篇
  1987年   2篇
  1986年   1篇
  1983年   1篇
  1982年   1篇
  1972年   1篇
排序方式: 共有803条查询结果,搜索用时 0 毫秒
741.
基于粗糙集与灰色SVM的中国CO2排放量预测   总被引:1,自引:0,他引:1       下载免费PDF全文
周建国  张希刚 《中国环境科学》2013,33(12):2157-2163
从我国CO2排放量的不确定性、不完整性、小样本等特征出发,以灰色系统(GM)模型和支持向量机(SVM)模型为基础,建立基于粗糙集的组合预测模型.利用该模型以我国1990~2011年CO2排放量的数据以及同期的人口数量、GDP和能源消耗总量数据为基础对我国同期CO2排放量进行预测来验证其有效性,最后对我国2012~2017的CO2排放量进行预测.结果表明,灰色系统理论与支持向量机模型仅能够反应我国CO2排放的长期变化趋势,在预测精度上存在一定缺陷而基于粗糙集与灰色SVM的组合预测模型在预测精度上明显优于以上两种方法,能够对我国未来CO2排放量进行准确有效的预测分析.  相似文献   
742.
Urban ecological risk characterization is the final step in risk assessment and an important foundation upon which risk managers build risk aversion, risk control, and emergency handling strategies. In this study, we reviewed present risk characterization methods and proposed a multi-level characterization method for the assessment of urban ecological risks. The new characterization method consists of four elements: urban ecological risk sources, risk source probabilities, assessment endpoint indicators, and assessment endpoint indicator probabilities. Using this method, results of risk assessments can be organized into different levels of detail to meet different risk management goals.  相似文献   
743.
提出了基于最小二乘支持向量机(LSSVM)构造以球磨机制浆速度作为目标优化模型,并采用遗传算法实现了给料量、给水量、漩流器入口压力等运行参数的寻优,获得了优化制浆速度的调整方式。以此方式的相应参数作为当前负荷下的基准值,能很好地解决制浆工况下运行参数基准的确定问题。通过现场试验证明:按此基准值运行,可以提高制浆速度,降低电耗。  相似文献   
744.
With about half of its territory being farmed, agriculture is the main land use in the European Union (EU). As over 10% of the total EU manufacturing output comes from the agri-food sector, it also is an economic factor of great importance. Moreover, EU policy in this sector has far-reaching consequences ranging from the EU's status as a global trade partner to landscape preservation and development. The LUMOCAP Policy Support System is targeted towards policy makers in the European Commission (EC) and its Member States (MS) and aims to provide support in the field of sustainable agricultural and rural development. To this end it incorporates an integrated model with socio-economic and bio-physical processes, operating at different spatial scales. For supporting integrated assessment, a large number of policy levers is included as inputs for these models and outputs are transformed into policy-relevant social, economic and environmental indicators. The whole system is framed in a flexible, modular and easy to use software package that is useable for process experts and policy-analysts alike.This paper describes the integrated model, the individual models and a first calibration of the system. It demonstrates the system's behaviour for typical scenario runs and concludes with a reflection on the current status of the system and some recommendations for further development.  相似文献   
745.
Polygon-based thematic maps can be composed of boundaries that exist by definition—i.e., bona fide boundaries—or those that exist relative to a specific interpretation of a spatial phenomenon—i.e., fiat boundaries. The construction of maps composed of fiat boundaries is usually based on a subjective interpretive methodology that is affected by the data used to construct the map and the minimum mapping unit employed. That fiat boundaries are not the same as bona fide boundaries affects their use in computer-based spatial decision support tools. This is discussed both in terms of an analysis conducted at one specific moment, and in respect to increasingly common multi-temporal analysis.
Kim LowellEmail:
  相似文献   
746.
PROBLEM: This study evaluated injured construction workers' perceptions of workplace safety climate, psychological job demands, decision latitude, and coworker support, and the relationship of these variables to the injury severity sustained by the workers. METHODS: Injury severity was assessed using the Health Assessment Questionnaire (HAQ), which evaluates functional limitations. Worker perceptions of workplace variables were determined by two instruments: (a) the Safety Climate Measure for Construction Sites and (b) the Job Content Questionnaire (JCQ). RESULTS: The overall model explained 23% of the variance in injury severity, with unique contributions provided by union status, the Safety Climate Score, and Psychological Job Demands. A positive significant correlation was found between injury severity and the Safety Climate Scores (r = .183, P = .003), and between the Safety Climate Scores and union status (r = .225, P < .001). DISCUSSION: There were statistically significant differences between union and nonunion workers' responses regarding perceived safety climate on 5 of the 10 safety climate items. Union workers were more likely than nonunion workers to: (a) perceive their supervisors as caring about their safety; (b) be made aware of dangerous work practices; (c) have received safety instructions when hired; (d) have regular job safety meetings; and (e) perceive that taking risks was not a part of their job. However, with regard to the 49-item JCQ, which includes Coworker Support, the responses between union and nonunion workers were very similar, indicating an overall high degree of job satisfaction. However, workers who experienced their workplace as more safe also perceived the level of management (r = -.55, P < .001) and coworker (r = -.31, P < .001) support as being higher. IMPACT ON INDUSTRY: The findings of this study underscore the critical need for construction managers to alert workers to dangerous work practices and conditions more frequently, and express concern and praise workers for safe work in a manner that is culturally acceptable in this industry. Workplace interventions that decrease the incidence and severity of injuries, but that are flexible enough to meet a variety of potentially competing imperatives, such as production deadlines and client demands, need to be identified.  相似文献   
747.
可持续发展能力建设与人力资本投资   总被引:7,自引:0,他引:7  
本文在分析阐述可持续发展能力建设的内涵及可持续发展能力建设与人力资本投资关系的基础上 ,得到以下几个结论 :①可持续发展能力建设包含人类发展能力和自然支撑能力。②人力资本投资不仅可以提高人类发展能力 ,也能提高自然支撑能力。③人力资本投资能能为可持续发展提供一个良好的外部运行环境。因此 ,在实施可持续发展战略过程中 ,加强人力资本投资是至关重要的。  相似文献   
748.
The shellfish aquaculture industry (SAI) has operated in Baynes Sound, British Columbia (BC) since the early 1900s. Recognizing the economic potential of the area, the industry has requested additional farming opportunities. However, Baynes Sound upland residents and many other stakeholders have expressed concerns that SAI activities are having a negative impact on the environment, quality of life, and other nonaquaculture resource uses in the area. In order to address these issues, the Action Plan was initiated by a BC government interagency project team in November 2001. To assist in assessing the strategic aspects of this conflict, the decision support system GMCR II is employed here to apply a new methodology, the graph model for conflict resolution, to systematically analyze the ongoing conflict over shellfish aquaculture development in Baynes Sound within a social, economic, and environmental framework. Valuable insights are procured to guide decision-makers toward sustainability of the shellfish industry.  相似文献   
749.
This article presents the design of a fuzzy decision support system (DSS) for the assessment of alternative strategies proposed for the restoration of Lake Koronia, Greece. Fuzzy estimates for the critical characteristics of the possible strategies, such as feasibility, environmental impact, implementation time, and costs are evaluated and supplied to the fuzzy DSS. Different weighting factors are assigned to the critical characteristics and the proposed strategies are ordered with respect to the system responses. The best strategies are selected and their expected impact on the ecosystem is evaluated with the aid of a fuzzy model of the lake. Sensitivity analysis and simulation results have shown that the proposed fuzzy DSS can serve as a valuable tool for the selection and evaluation of appropriate management actions. Note: This version was published online in June 2005 with the cover date of August 2004.  相似文献   
750.
Connecting Multiple Criteria Decision Support (MCDS) methods with SWOT (Strengths, Weaknesses, Opportunities, and Threats) analysis yields analytical priorities for the factors included in SWOT analysis and makes them commensurable. In addition, decision alternatives can be evaluated with respect to each SWOT factor. In this way, SWOT analysis provides the basic frame within which to perform analyses of decision situations. MCDS methods, in turn, assist in carrying out SWOT more analytically and in elaborating the results of the analyses so that alternative strategic decisions can be prioritized also with respect to the entire SWOT. The A'WOT analysis is an example of such hybrid methods. It makes combined use of the Analytic Hierarchy Process (AHP) and SWOT. In this study, a hybrid method of the Stochastic Multicriteria Acceptability Analysis with Ordinal criteria (SMAA-O) and SWOT is developed as an elaboration of the basic ideas of A'WOT. The method is called S-O-S (SMAA-O in SWOT). SMAA-O enables the handling of ordinal preference information as well as mixed data consisting of both ordinal and cardinal information. Using SMAA-O is enough to just rank decision elements instead of giving them cardinal preference or priority ratios as required by the most commonly used MCDS methods. Using SMAA-O, in addition to analyzing what the recommended action is under certain priorities of the criteria, enables one to analyze what kind of preferences would support each action. The S-O-S approach is illustrated by a case study, where the shareholders of a forest holding owned by a private partnership prepared the SWOT analysis. Six alternative strategies for the management of their forest holding and of old cottage located on the holding were formed. After S-O-S analyses were carried out, one alternative was found to be the most recommendable. However, different importance orders of the SWOT groups would lead to different recommendations, since three of the six alternatives were efficient according to S-O-S analyses.  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