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   458篇
  免费   56篇
  国内免费   81篇
安全科学   42篇
废物处理   9篇
环保管理   81篇
综合类   245篇
基础理论   104篇
污染及防治   17篇
评价与监测   43篇
社会与环境   50篇
灾害及防治   4篇
  2024年   1篇
  2023年   2篇
  2022年   13篇
  2021年   18篇
  2020年   13篇
  2019年   13篇
  2018年   9篇
  2017年   17篇
  2016年   14篇
  2015年   33篇
  2014年   24篇
  2013年   37篇
  2012年   38篇
  2011年   38篇
  2010年   38篇
  2009年   34篇
  2008年   29篇
  2007年   27篇
  2006年   33篇
  2005年   27篇
  2004年   21篇
  2003年   12篇
  2002年   10篇
  2001年   19篇
  2000年   15篇
  1999年   10篇
  1998年   17篇
  1997年   8篇
  1996年   3篇
  1995年   5篇
  1993年   3篇
  1992年   3篇
  1991年   5篇
  1990年   2篇
  1988年   1篇
  1987年   1篇
  1981年   2篇
排序方式: 共有595条查询结果,搜索用时 15 毫秒
21.
城市酒店业的碳排放核算及低碳指标分析   总被引:2,自引:0,他引:2  
随着中国的快速城市化和服务业的发展,旅游业逐渐成为主要的温室气体排放者之一,酒店面临节能减排的压力并缺乏相关的评价标准.本文建立了生命周期的酒店业碳排放核算框架和低碳指标,并以宁波市为案例城市,对其3种类型的酒店进行碳排放核算和低碳指标的分析.结果表明,能源消费是酒店业最大的碳排放源,占93.5%~94.1%;各类酒店的碳排放量在2013—2015年间有约8.2%~9.2%的减少;从低碳指标看,五星级酒店的单位建筑面积的碳排放最小,单位出租间天数和单位旅客的碳排放最大,而四星级酒店的单位营业额碳排放最小.优化区域电力碳排放水平和酒店的软硬件设施是减少酒店碳排放的有效措施,碳标签是有效的酒店业低碳管理的政策工具.  相似文献   
22.
基于AHP和DEA模型的农业生态效率评价——以无锡市为例   总被引:10,自引:0,他引:10  
农业面源污染已成为我国重要环境污染源之一,但由于农业面源污染具有分散、面广、周期长、随机性等特点,在评价上存在较大难度。根据生态效率理论,结合农业生产的特点,建立了综合考虑经济效益和环境影响的农业生态效率评价指标体系,并以江苏省无锡市为例,选取该市1998~2008年农业生产和面源污染相关数据,运用偏好锥的数据包络分析模型(DEA)对其农业生态效率进行了评价分析。结果显示:1998~2008年,无锡市农业生态效率呈现先下降后上升的趋势,近三年累计上升幅度达22%。表明近年来无锡市农业面源污染治理成效显著,农业可持续发展水平显著提高。提出的农业生态效率评价体系和方法为进一步推进农业面源污染治理工作提供了依据  相似文献   
23.
As a typical tropical agro-forestry ecosystem in Wenchang,Hainan Province,China,rational mechanisms of the rubber-tea-chicken eco-agricultural model were studied with the Solow technological level index,stability indicator,harmonizing coefficient,grey correlation coefficient and production dominance.This study focused on rational hierarchical structure,the limiting factors and optimal strategies of the model development based on model structure,resource conditions and external market demands.Results showed that rational mechanism of the rubber-tea-chicken ecosystem model mainly included technological contributions,leverage function of dominance component(livestock husbandry),stability of the model structure and harmony of its components,the model dominant product’s market demand and government’s supporting policies.The contributions of fund,technology,information and talent resources played an important role in improving sustainability and productivity of the agro-forestry model.  相似文献   
24.
中国新克强指数的构建与实证分析   总被引:1,自引:0,他引:1  
随着中国经济进入新常态,英国《经济学人》杂志构建的克强指数已无法反映中国经济的全貌,如何客观地反映中国经济的真实状况成为一个迫切需要解决的现实问题。为更好地测度中国经济运行的真实状况,本文根据李克强总理提出的"未来会更加关注就业、居民收入和生态环境的持续改善"的愿景,在原有克强指数的基础上,增加年末就业人员数、农村居民家庭人均纯收入、城镇居民家庭人均可支配收入等就业和收入方面的指标,使用中国1995—2015年的相关数据和层次分析法构建了克强指数的修订版本即新克强指数,并将新克强指数与GDP增长率、克强指数进行了比较,发现新克强指数在反映中国经济波动和经济整体运行状态上有更为优良的性质。与GDP增长率相比,新克强指数克服了服务业比重提高带来的熨平效应,进而灵敏地反映中国经济波动情况,并对异常事件更加具有敏感性。相对于克强指数而言,新克强指数破除了因中国在第二产业上存在失衡性发展所带来的经济波动的杠杆效应,降低了经济增长中的虚假成分,从而与中国经济运行的整体关联度更为密切。此外,相对于克强指数而言,新克强指数在反映经济景气方面有着较好的时效性与关联性。采用时差相关分析法对新克强指数与宏观经济指标之间的关系进行分析,发现新克强指数在反映第一产业增加值、第三产业增加值、最终消费支出、资本形成总额、对外贸易、通货膨胀等方面具有优势。研究表明:新克强指数是更适宜测度中国经济的多元评价指标,为测度中国经济运行的真实状况提供了科学的参考依据。  相似文献   
25.
This study identifies the natural background, anthropogenic background and distribution of contamination caused by heavy metal pollutants in soil in Chunghua County of central Taiwan by using a finite mixture distribution model (FMDM). The probabilities of contaminated area distribution are mapped using single-variable indicator kriging and multiple-variable indicator kriging (MVIK) with the FMDM cut-off values and regulation thresholds for heavy metals. FMDM results indicate that Cr, Cu, Ni and Zn can be individually fitted by a mixture model representing the background and contamination distributions of the four metals in soil. The FMDM cut-off values for contamination caused by the metals are close to the regulation thresholds, except for the cut-off value of Zn. The receiver operating characteristic (ROC) curve validates that indicator kriging and MVIK with FMDM cut-off values can reliably delineate heavy metals contamination, particularly for areas lacking background information and high heavy metal concentrations in soil.  相似文献   
26.
中国民航局提出持续安全理念,并正在制定国家航空安全方案,推动行业安全管理由目前基于规章符合性的安全监管逐渐转向规章符合性基础上的安全绩效监管,其中一项重要的工作是设定中国民航业可接受的安全水平,来衡量民航业是否满足持续改进安全的目标的要求。本文根据国际民航组织对可接受安全水平的设定指南,同时参考国外民航常用的事故指标,设计了一套中国民航行业可接受安全水平的指标体系,该指标体系包括安全评估指标、安全绩效评估指标和安全指数三层,并对该指标体系内事故率指标和事故征候率指标设定了未来10年的目标值。该指标体系及其目标值的设定不仅可作为衡量民航是否持续安全的标准,也可为航空运输企业设定自身的安全绩效考核指标提供参考。  相似文献   
27.
The results of studies on postfire succession in larch forests of the permafrost zone are discussed. The main directions of successional processes in burned-out areas of different ages are described. It has been shown that secondary pyrogenic successions in larch forests follow the scheme of rapid regeneration without tree species replacement and the model of succession tolerance. Groups of plant species with different life strategies and indicator species characterizing different stages of the overgrowing of burned-out areas have been identified.  相似文献   
28.
采用衡山白果地区石膏矿山的11个评价指标,综合运用粗糙集和神经网络理论,构建了基于粗糙集-神经网络(RS-ANN)的矿山地质环境影响评价模型,对RSES软件约简的数据和无约简的数据采用EasyNN-plus软件进行预测评价。神经网络模型的输入属性为8个,而粗糙集-神经网络模型的输入属性为6个,训练样本均为13个,预测样本均为4个,前者的平均预测精度为1.85%~24.86%,后者为1.23%~15.28%。研究发现,粗糙集在保留关键信息的前提下可有效地对数据表进行约简,约简后的神经网络预测结果与实际情况吻合,并比无约简时总体精度有较大幅度提高。  相似文献   
29.
Life cycle thinking is a good approach to be used for environmental decision-support, although the complexity of the Life Cycle Assessment (LCA) studies sometimes prevents their wide use. The purpose of this paper is to show how LCA methodology can be simplified to be more useful for certain applications.In order to improve waste management in Catalonia (Spain), a Cumulative Energy Demand indicator (LCA-based) has been used to obtain four mathematical models to help the government in the decision of preventing or allowing a specific waste from going out of the borders. The conceptual equations and all the subsequent developments and assumptions made to obtain the simplified models are presented.One of the four models is discussed in detail, presenting the final simplified equation to be subsequently used by the government in decision making.The resulting model has been found to be scientifically robust, simple to implement and, above all, fulfilling its purpose: the limitation of waste transport out of Catalonia unless the waste recovery operations are significantly better and justify this transport.  相似文献   
30.
Accurate assessment of shark population status is essential for conservation but is often constrained by limited and unreliable data. To provide a basis for improved management of shark resources, we analyzed a long‐term record of species‐specific catches, sizes, and sexes of sharks collected by onboard observers in the western and central Pacific Ocean from 1995 to 2010. Using generalized linear models, we estimated population‐status indicators on the basis of catch rate and biological indicators of fishing pressure on the basis of median size to identify trends for blue (Prionace glauca), mako (Isurus spp.), oceanic whitetip (Carcharhinus longimanus), and silky (Carcharhinus falciformis) sharks. Standardized catch rates of longline fleets declined significantly for blue sharks in the North Pacific (by 5% per year [CI 2% to 8%]), for mako sharks in the North Pacific (by 7% per year [CI 3% to 11%]), and for oceanic whitetip sharks in tropical waters (by 17% per year [CI 14% to 20%]). Median lengths of silky and oceanic whitetip sharks decreased significantly in their core habitat, and almost all sampled silky sharks were immature. Our results are consistent with results of analyses of similar data sets. Combined, these results and evidence of targeted fishing for sharks in some regional fisheries heighten concerns for sustainable utilization, particularly for oceanic whitetip and North Pacific blue sharks. Regional regulations that prohibit shark finning (removal of fins and discarding of the carcass) were enacted in 2007 and are in many cases the only form of control on shark catches. However, there is little evidence of a reduction of finning in longline fisheries. In addition, silky and oceanic whitetip sharks are more frequently retained than finned, which suggests that even full implementation of and adherence to a finning prohibition may not substantially reduce mortality rates for these species. We argue that finning prohibitions divert attention from assessing whether catch levels are sustainable and that the need for management of sharks should not be addressed by measures that are simple to implement but complex to enforce and evaluate. Tendencias Poblacionales de Tiburones del Océano Pacífico y la Utilidad de Regulaciones sobre Cercenamiento de Aletas  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