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   2024篇
  免费   220篇
  国内免费   412篇
安全科学   244篇
废物处理   37篇
环保管理   361篇
综合类   1051篇
基础理论   274篇
环境理论   1篇
污染及防治   177篇
评价与监测   70篇
社会与环境   209篇
灾害及防治   232篇
  2024年   10篇
  2023年   36篇
  2022年   66篇
  2021年   74篇
  2020年   73篇
  2019年   70篇
  2018年   74篇
  2017年   87篇
  2016年   93篇
  2015年   85篇
  2014年   94篇
  2013年   165篇
  2012年   149篇
  2011年   163篇
  2010年   114篇
  2009年   106篇
  2008年   73篇
  2007年   147篇
  2006年   115篇
  2005年   125篇
  2004年   110篇
  2003年   98篇
  2002年   80篇
  2001年   55篇
  2000年   61篇
  1999年   79篇
  1998年   26篇
  1997年   33篇
  1996年   33篇
  1995年   25篇
  1994年   17篇
  1993年   32篇
  1992年   23篇
  1991年   21篇
  1990年   14篇
  1989年   6篇
  1988年   4篇
  1987年   1篇
  1986年   2篇
  1983年   1篇
  1981年   2篇
  1980年   2篇
  1979年   2篇
  1978年   4篇
  1977年   2篇
  1976年   1篇
  1973年   1篇
  1972年   1篇
  1971年   1篇
排序方式: 共有2656条查询结果,搜索用时 453 毫秒
101.
The ecosystem services (ES) concept is being increasingly incorporated into environmental policy formulation and management approaches. The Corporate Ecosystem Services Review (ESR) is a framework used to assess the dependence and impact that a business has on ES. The success of the corporate experience of ES assessment provides an opportunity for adaption for local authority decision making. In this paper, the ESR tool was adapted to the South African setting at a local government level, and tested at two sites in the Msunduzi Municipality, KwaZulu-Natal. In testing the tool and gathering feedback from key stakeholders, it was found that there are both opportunities and challenges to this approach. Overall, however, it provides an opportunity for the systematic inclusion of ES assessment into existing regulatory frameworks for land-use planning and Integrated Environmental Management, whether in a strategic application, at a broader spatial (municipal) scale or in a specific locale within the municipality.  相似文献   
102.
主要介绍汽车整车自然暴露试验评价方法,基于整车厂长期进行汽车整车自然暴露试验,对整车进行表观检测、性能检查及其他项目检测,通过分析试验结果,归纳汽车内外饰件常见缺陷,按照失效程度和不同部件类型,为整车耐候性进行等级划分,建立整车系统化评价方法。  相似文献   
103.
Continuous flow transesterification of waste frying oil (WFO) with methanol for the biodiesel production was tested in a laboratory scale jacketed reactive distillation (RD) unit packed with clam shell based CaO as solid catalyst. The physiochemical properties of the clam shell catalysts were characterized by X-ray Diffraction (XRD), Brunauer–Emmett–Teller (BET), Scanning Electron Microscopy (SEM), and Energy Dispersive Atomic X-ray Spectrometry (EDAX). The effects of the reactant flow rate, methanol-to-oil ratio, and catalyst bed height were studied to obtain the maximum methyl ester conversion. Reboiler temperature of 65°C was maintained throughout the process for product purification and the system reached the steady state at 7 hr. The experimental results revealed that the jacketed RD system packed with clam shell based CaO showed high catalytic activity for continuous production of biodiesel and a maximum methyl ester conversion of 94.41% was obtained at a reactant flow rate of 0.2 mL/min, methanol/oil ratio of 6:1, and catalyst bed height of 180 mm.  相似文献   
104.
自然资源资产及其负债表编制与审计   总被引:1,自引:1,他引:0       下载免费PDF全文
自然资源资产仍然是一个新概念,还需要在理论和方法层面进行系统的研究。就当今及今后一个时期看,自然资源资产负债表的编制和自然资源资产审计,是亟需研究的理论和现实问题。在此,重点对自然资源资产的概念、属性、分类进行探讨,并就自然资源资产负债表及编制的重点与基础,自然资源资产审计及其重点与方式等,进行系统讨论。  相似文献   
105.
Research suggests that previous, current, and prospective extractive industry activities influence perceptions of new development. Studies that have drawn this conclusion, however, have usually focused on specific projects in specific communities. Here, these factors are examined on an aggregate, national scale. Combining geospatial data on extractive industry activities and survey data from a nationally representative sample (N = 1061), the influence of extractive industry activities on support for fracking is studied. While limited evidence is found for the impact of proximity to oil and gas wells or production on support for fracking, employment levels in the natural resources and mining sector in the respondent’s county and residence in an area experiencing active oil and gas development significantly increase support for fracking. The results highlight the role of spatial and community factors in shaping support for energy development.  相似文献   
106.
对自然恢复下4类不同年代样地的灰渣养分含量及重金属含量进行研究,通过对比分析发现,有机质、全氮、全钾、全磷含量随着自然恢复时间的增加呈现递增的趋势,全磷含量在各恢复阶段与对照样地之间并不存在显著差异(P0.05)。pH随着恢复时间的增加呈现递减的趋势。对灰渣综合质量指数进行研究发现,自然恢复长期、中期、短期与自然恢复初期对比均有显著提高(P0.05),且随着自然恢复时间的增加灰渣综合质量指数逐渐提高。对灰渣场锌、铅、铜3种重金属研究后发现,在自然恢复下随着时间的增加,灰渣中重金属含量均呈现递减的趋势。  相似文献   
107.
Two industrial sites were investigated based on years of available hydrogeologic information and monitoring data for soil and groundwater. Collected data were forensically evaluated using age-dating and fingerprinting methods. The previous business uses of the project sites were as a gas station, laundry/dry-cleaning service, and car wash with petroleum underground storage tanks (USTs). As a result, these sites were exposed to a number of toxic contaminants at relatively high concentrations. Source control was necessary for successful remediation and the ultimate removal of the remaining compounds from these industrial sites. Although contaminated soil around the source was excavated during the remedial action and the high concentrations of contaminants were reduced, typical groundwater contaminants such as petroleum hydrocarbons as gasoline (TPH-G), benzene, toluene, ethylbenzene, xylenes (BTEX), and oxygenates including methyl tert-butyl ether (MTBE), diisopropyl ether (DIPE), ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME), and tert-butyl alcohol (TBA) were persistently found at the studied sites around the source points. The plume and concentration of contaminants had changed their shapes and strength for all monitoring periods. Thus, additional source control seems to be a requirement for the complete removal of source contamination, which must be ascertained with groundwater and soil monitoring on a regular time base. For the study sites, monitored natural attenuation was relatively feasible for the long-term plan; however, it did not offer a perfect remediation solution for an ultimate goal because of residual toxic compounds that might have affected the surrounding residential areas at higher concentrations than their health limits. Therefore, as a remediation strategy, the combination of clean-up technology and natural attenuation with monitoring activities are more highly recommended than either clean-up or natural attenuation used separately.  相似文献   
108.
循环经济理论思索   总被引:13,自引:5,他引:8  
李康 《环境科学研究》2007,20(1):114-117
循环经济是对近现代人类社会长期、大规模、高强度、未善待大自然的开发活动导致自然资源和生态环境逼近其耐受极限而进行反思的产物.从经济-社会-科技-自然多元复合人工自组织系统角度,研究了循环经济的科学内涵,指出循环经济是建立在组织结构协同基础上的物质循环与能量梯级利用,是集约经济的高级形态和理想模式.针对循环经济包含的若干属性特征,论述了5个基本理论问题,包括守恒与平衡、循环与协调、互动整合与倍增效应、聚集经济与产业集群、生态学基本原理应用和生态系统服务.并就生态工业系统规划设计涉及的基本方法、关键环节、人力投入等给出了政策建议.   相似文献   
109.
重庆市特大旱灾的自然与社会机制分析   总被引:1,自引:0,他引:1  
文章针对2006年的特大旱灾探讨了2006年的特大旱灾的特征,分析了2006年特大旱灾的形成自然机制和社会机制,并提出了今后重庆市抗御旱灾的策略。认为2006年的特大旱灾是自然因素与社会因素叠加的结果,是人类社会经济系统自身易损性的体现。  相似文献   
110.
采用富集培养的方法,从未受苯酚污染的自然土壤中分离得到5株能以苯酚为唯一碳源生长的细菌.根据生理生化特性和系统发育分析对它们进行了初步鉴定,菌株PHD-2为Ralstonia sp.,菌株 PHD-4为Acinetobacter sp.,菌株PHD-5 为Microbacterium sp.,菌株PHD-1和PHD-3均为Pseudomonas sp.,16S rRNA基因序列的同源性比较和系统发育分析表明自然土壤中的苯酚降解菌具有丰富的多样性.  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