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   1310篇
  免费   187篇
  国内免费   1176篇
安全科学   113篇
废物处理   60篇
环保管理   95篇
综合类   1704篇
基础理论   346篇
环境理论   1篇
污染及防治   249篇
评价与监测   35篇
社会与环境   39篇
灾害及防治   31篇
  2024年   12篇
  2023年   52篇
  2022年   117篇
  2021年   134篇
  2020年   110篇
  2019年   117篇
  2018年   114篇
  2017年   105篇
  2016年   99篇
  2015年   122篇
  2014年   139篇
  2013年   188篇
  2012年   173篇
  2011年   158篇
  2010年   118篇
  2009年   108篇
  2008年   108篇
  2007年   108篇
  2006年   104篇
  2005年   80篇
  2004年   72篇
  2003年   51篇
  2002年   42篇
  2001年   38篇
  2000年   38篇
  1999年   27篇
  1998年   31篇
  1997年   24篇
  1996年   15篇
  1995年   23篇
  1994年   8篇
  1993年   9篇
  1992年   10篇
  1991年   4篇
  1990年   4篇
  1989年   3篇
  1988年   3篇
  1987年   1篇
  1986年   2篇
  1981年   1篇
  1971年   1篇
排序方式: 共有2673条查询结果,搜索用时 31 毫秒
151.
区域经济增长与环境质量之间的关系研究是目前学者们探讨的重要学术议题之一.其中较多的是对EKC曲线的验证,近几年部分学者从国民经济各部门中的产业自身特征、产业结构、技术进步、FDI效应等方面考察产业发展对污染物排放的影响.然而以上研究议题中学者均没有讨论污染物的发生主体-各产业部门与排污的直接关系.故本文将从宏观尺度下的综合水平测度区域经济发展与环境质量关系、中观尺度下的产业属性特征与排污关系的研究视角转移至分析具体产业部门的污染物排放效应,同时将产业置于产业链的结构形式中,研究产业链上产业发展与污染物排放的关系.发现:第一,通过借助复杂网络思想的社区划分方法,将山东省39个产业部门分为3个社团.其中社团I主要由制造业部门组成,共有18个产业部门,社团II包括了15个部门,主要是第三产业,杜团III由6个产业部门组成且内部异质性高.第二,选择其中以制造业为主的社团I,并在社团I内识别出一条彼此间联系最为紧密的产业链,包括农林牧渔业、食品制造及烟草加工业、化学工业、纺织工业、服装皮革羽绒及其制品业、通用/专用设备制造业和交通运输设备制造业.以一种定量的方法获取了通过价值流传递而串在一起的产业链条.该产业链的经济规模、污染物规模在山东省均有重要地位.第三,采用岭回归分析方法,构建了6个制造业与产业链工业废水、固体废弃物排放的关系模型,6个制造业中对工业废水、固体废弃物排放相对贡献度最大的部门分别为服装皮革羽绒及其制品业、食品制造及烟草加工业.这是由于上游产业排污的链式传递效应与产业自身污染物排放效应的共同叠加作用.  相似文献   
152.
Abstract

Leaching, downward mobility and persistence of tebufenozide was investigated under laboratory conditions in columns packed with forest litter and soil, after fortification with the analytical grade material (purity > 99.6%) and with two commercial formulations, RH‐5992 2F (aqueous flowable) and RH‐5992 ES (emulsion suspension). Two types of litter and soil were used: one type with relatively high amounts of sand and the other with high amounts of clay.

The concentrations eluted in the leachates were lower when the analytical material (dissolved in acetone) was used for fortification, than when the two formulations (diluted with water) were used. The amount leached was higher for RH‐5992 2F than for RH‐5992 ES. The type of substrate, i.e., sandy or clay type, had only marginal influence on the amounts eluted in the leachates. Downward movement of tebufenozide from the top 2‐cm layer to the untreated middle and bottom layers (3‐cm segments) was consistently lower when the analytical material was used for fortification, than when the two formulations were used. Downward movement was higher for RH‐5992 2F than for RH‐5992 ES. Persistence of tebufenozide in substrates, maintained under submerged conditions for 70 days after leaching, indicated an initial 2‐week lag period prior to the onset of degradation. Formulation‐related differences were observed in the half‐life (DT50) values. When the analytical material was used for fortification, the DT50 ranged from ca 54 to 59 d. However, when the formulations were used for fortification, the DT50 showed a higher range, i.e., from ca 62 to 67 d for RH‐5992 2F and ca 70 to 80 d for RH‐5992 ES. Formulation ingredients appear to have caused enhanced adsorption of tebufenozide onto the substrates, thus delaying degradation.  相似文献   
153.
An info-tech complex is proposed for 286 acres (116 ha) of land within the East Calcutta wetlands. The proposed site is 15 km east of Kolkata city and only 8 km south of Dum Dum airport. The site is vacant, with pockets of agricultural land and a few degrading water-logged areas. In order to assess the likely impact of the proposed development on the environment, a rapid environmental impact assessment of an area of 10 km radius from the centre of the project site was carried out. The present status of the environment with respect to ambient air, surface water, groundwater, soil, landuse, noise, and socio-economics of the core and buffer zone has been documented and correlated with 24 project activities during construction, development and operational phases. The frequency of adverse impacts is greater than that of beneficial impacts. Out of the total adverse impacts 20 are short term, reversible and have a low magnitude. The total impact score for the proposed project is (–)468.75 and as per the Assessment Value Index Scale the environmental impact of the proposed project activities is no appreciable impact. But there are certain sectors where the environment will be adversely impacted. Therefore, appropriate measures have been suggested to ameliorate the adverse impacts. It is envisaged that if these measures are implemented then there will be an improvement in the quality of the environment, as well as life, by 687.5 units.  相似文献   
154.
The holomictic Traunsee is the deepest and second largest lakein Austria. The special characteristic of this ecosystem isthe fact that local salt and soda industries presumably alterthe lake by the discharge of waste materials. Since thebeginning of the 20th century salt and soda works areannually releasing up to 50,000 tons of solid wastes and up to150,000 tons of chloride into Traunsee. To assess potentialeffects of these anthropogenic impacts on the bacterioplanktonthree sampling sites, influenced as well as not influenced bythe industrial discharge, were chosen for comparison andsampled monthly from November 1997 to October 1998. Bacterialabundance ranged between 0.4 to 3.0 × 106 cells ml-1 with decreasing numbers along the depth profile. Theproportion of actively respiring bacteria, i.e. INT [2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyltetrazolium chloride]reducing cells, never exceeded 10% of DAPI (4',6'-diamidino-2-phenylindole) stained cells. Fluorescence in situ hybridization (FISH) was used to examine the seasonal and spatial distribution of dominant phylogenetic groups of thebacterioplankton. Up to 84% of bacteria detected with DAPIcould be detected via FISH applying the universal bacterialprobe EUB338. Percentages of alpha- and beta-Proteobacteriaand members of the Cytophaga-Flavobacterium cluster did notexceed 60% of DAPI-stained cells.Beta-Proteobacteriaappeared to be the most abundant group, not only in Traunsee butalso in two reference lakes, Attersee and Hallstättersee. No significant differences in any of the bacterial parameters couldbe detected between the three sampling sites and all measurementswere found in the range reported for oligotrophic lakes. The highdischarge of the Traun River, resulting in a lake water renewaltime of only one year, may diminish possible effects of industrial waste discharge in the pelagic zone.  相似文献   
155.
从二维空间的角度出发,提出了系统的结构特征;联系紧密和联系松散;复杂式相互作用和直线式相互作用的概念及其特点,并探讨了系统结构特征在系统事故致因中的应用分析。  相似文献   
156.
基于洪水灾害快速评估的承灾体易损性信息管理系统   总被引:5,自引:0,他引:5  
洪水灾害易损性信息管理系统是为了开展洪水灾害快速评估,对不同洪水灾害流域和同一洪水灾害流域中的不同地区、不同承灾体(财产分类)、不同致灾因子(水深和历时等)条件,以财产的损失率为核心的综合信息管理系统。本文介绍了洪水灾害易损性信息管理系统的开发与设计的基本原理,阐述了系统的总体结构框架和功能模块划分,并且在系统数据流程图的基础上,对损失率数据库等几个重要的模块进行了详细的分析与设计,给出了系统的部分运行结果。本系统在与GIS、遥感等空间技术结合后,能够高效地完成各种洪水灾害损失的快速评估与预测分析工作,同时,本系统亦可独立作为对区域洪水灾害易损性研究的数据基础和理论支撑。  相似文献   
157.
A “finding of no significant impact” (FONSI) resulting from an environmental assessment (EA) was reported by the US Army in June 1986 for the construction and utilization of a multipurpose range complex (MPRC) at the Pohakuloa Training Area, Hawaii. There was little public response, and the US Fish and Wildlife Service and state agencies were consulted and had few comments concerning the results of the botanical surveys used in the assessment. Construction of the $24 million project was begun in 1988. Near the end of construction in 1989 a lawsuit was filed to halt construction because an environmental impact statement (EIS) had not been done for the project, and the plaintiff thought that significant damage had occurred to several unusual ecosystems. Judgment was against the plaintiff and construction continued. An appeal was filed with the 9th Circuit Court. As MPRC construction was nearly complete, and on advice of Department of Justice lawyers, the Department of Army agreed to settle out of court. The settlement in part called for: (1) the plaintiff to drop the appeal and allow construction to be completed as scheduled, and (2) the Department of Army to prepare an EIS for the operation of the MPRC. A subsequent botanical survey for the EIS discovered one endangered plant species, four category 1 candidate plant species (taxa with sufficient data to support listing as endangered or threatened), three category 2 candidate plant species (taxa with some evidence of vulnerability but insufficient data to support listing at this time), one category 3a species (presumably extinct taxa), and possibly three undescribed species growing within the MPRC boundary. The MPRC case study is an excellent example of why the National Environmental Policy Act (NEPA) must be modified to require in-depth and thorough environmental surveys.  相似文献   
158.
In order to improve the process performance regarding the removal of organics, nitrogen, and an odor-causing compound (sulfide) contained in domestic wastewater, an entrapped-mixed-microbial cell (EMMC) with and without humic substances for both fixed and moving carrier reactors and conventional suspended growth culture (i.e. conventional activated sludge process) were investigated simultaneously. Both synthetic (simulated to the organics concentration of general domestic sewage) and actual domestic wastewater were investigated under operational conditions of 12 h of hydraulic retention time (HRT) with 1 h of aeration and 1 h of non-aeration, and 6 h of HRT with continuous aeration, at a room temperature of 25 +/- 2 degrees C. It was found that entrapping humic substances in the EMMC carriers had no impact on the removal of organics, nitrogen, and the odor-producing compound. Additionally, the performance of the EMMC moving carrier system for the removal of these pollutants is similar to that of the EMMC fixed carrier system. In general, the EMMC associated systems which provide high solids retention time achieve a better removal of chemical oxygen demand (COD), nitrogen, and the odor-producing substance than the suspended growth system for both HRTs of 6 h (continuous aeration) and 12 h (1 h of aeration and 1 h of non-aeration). Both the fixed and moving carrier EMMC processes, therefore, have the potential for improvement or replacement of the existing conventional activated sludge process with regard to improving the effluent qualities (such as COD, nitrogen and odor-producing compound) for reuse/disposal.  相似文献   
159.
Although several reports are available concerning the composition and dynamics of the microflora during the composting of municipal solid wastes, little is known about the microbial diversity during the composting of agro-industrial refuse. For this reason, the first parts of this study included the quantification of microbial generic groups and of the main functional groups of C and N cycle during composting of agro-industrial refuse. After a generalized decrease observed during the initial phases, a new bacterial growth was observed in the final phase of the process. Ammonifiers and (N2)-fixing aerobic groups predominated outside of the piles whereas, nitrate-reducing group increased inside the piles during the first 23 days of composting. Ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), showed an opposite trend of growth since ammonia oxidation decreased with the increase of the nitrite oxidation activity. Pectinolytics, amylolytics and aerobic cellulolytic were present in greater quantities and showed an upward trend in both the internal and external part of the heaps.Several free-living (N2)-fixing bacteria were molecularly identify as belonging especially to uncommon genera of nitrogen-fixing bacteria as Stenotrophomonas, Xanthomonas, Pseudomonas, Klebsiella, Alcaligenes, Achromobacter and Caulobacter. They were investigated for their ability to fix atmospheric nitrogen to employ as improvers of quality of compost. Some strains of Azotobacter chrococcum and Azotobacter salinestris were also tested. When different diazotrophic bacterial species were added in compost, the increase of total N ranged from 16% to 27% depending on the selected microbial strain being used. Such microorganisms may be used alone or in mixtures to provide an allocation of plant growth promoting rhizobacteria in soil.  相似文献   
160.
Fe(Ⅱ) EDTA易被氧化为对NO无吸收能力的Fe(Ⅲ)EDTA,为实现Fe(Ⅱ)EDTA的循环使用,提出了Fe(Ⅱ)EDTA络合吸收-空气氧化解吸-铁屑还原再生组合脱除NO新工艺.采用空气氧化解吸络合吸收产物Fe(Ⅱ) EDTA (NO)中NO的方法,研究了温度及压力对Fe(Ⅱ)EDTA(NO)空气氧化解吸过程的影响.结果表明,0.4 MPa、333K为较优的解吸条件.该工艺可循环脱除NO,成本低、效率高,能有效回收NO2资源.  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