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   1045篇
  免费   10篇
  国内免费   35篇
安全科学   50篇
废物处理   87篇
环保管理   96篇
综合类   91篇
基础理论   158篇
环境理论   1篇
污染及防治   402篇
评价与监测   143篇
社会与环境   52篇
灾害及防治   10篇
  2023年   27篇
  2022年   132篇
  2021年   102篇
  2020年   40篇
  2019年   44篇
  2018年   59篇
  2017年   66篇
  2016年   64篇
  2015年   27篇
  2014年   40篇
  2013年   135篇
  2012年   47篇
  2011年   58篇
  2010年   42篇
  2009年   30篇
  2008年   27篇
  2007年   29篇
  2006年   22篇
  2005年   11篇
  2004年   15篇
  2003年   9篇
  2002年   8篇
  2001年   7篇
  2000年   8篇
  1999年   5篇
  1998年   1篇
  1997年   2篇
  1996年   1篇
  1995年   5篇
  1994年   6篇
  1993年   1篇
  1992年   2篇
  1991年   2篇
  1990年   1篇
  1989年   1篇
  1985年   4篇
  1984年   1篇
  1983年   1篇
  1981年   1篇
  1980年   1篇
  1979年   1篇
  1976年   1篇
  1974年   1篇
  1970年   1篇
  1964年   1篇
  1959年   1篇
排序方式: 共有1090条查询结果,搜索用时 453 毫秒
281.
Regional Environmental Change - The soils of the Mediterranean Basin are the products of soil processes that have been governed by a unique convergence of highly differentiated natural and...  相似文献   
282.
In this study, the volume and the cash value of water loss, and reduction of water loss as a result of enforcement action during 2011–2013 in the drinking water network of villages in Kermanshah Province, Iran, have been investigated. Date collected by referring to the different parts of rural water and waste water company of Kermanshah Province and checklist were completed. The study showed the volume of produced water and sold water has increased and the water loss percentage has decreased. High cost of water production compared to revenue of sold water and water loss resulted in significant detriments in terms of the water production costs. Water loss level decreased from 33% to 30% as result of measures taken to reduce water loss but, it is still 15% higher than the world average level. Also the reduction in number of water resources and increase in the number and volume of reservoirs indicates a lack of water and a growing need. As result of high water loss, waste of costs in the contrast of water production cost and also because physical water loss accounts for most of the water loss of villages, necessary measures can be effective in reducing loss and have economic justification.  相似文献   
283.
The aim of this study was to determine type of response curves for seventeen woody species (10 tree and 7 shrub species) to soil factors in an intact riparian forest in Safaroud River in northern Iran using HOF function. Data were collected along transects established perpendicular to the water flow on both sides of the river. Results indicated different responses for different woody species. The most common were symmetricunimodal response curves and curves showing an increase in occurrence probability after a certain value in form of a plateau. Bimodal curves were four times more frequent in riverside than forest interior area. It seems that river flow disturbances through frequent floods effect on species tolerance and optimum in riversides.  相似文献   
284.
Soil reclamation via additives can cause contradictory effects on the mobilization of toxic elements in soils under dry and wet conditions. Therefore, our aim was to investigate the impact of compost and sulfur in two rates (1.25 and 2.5%) on fractionation, mobilization, and phyto-availability of cadmium (Cd) and nickel (Ni) to sorghum (dry soil) and barnyard grass (wet soil) in a fluvial soil spiked with 25 mg Cd or 200 mg Ni/kg soil. Compost decreased the solubility and mobilization of Cd (especially in dry soil) and Ni (in both soils). Sulfur increased the solubility of Cd (31% in dry soil—49% in wet soil) and Ni (4.6% in wet soil—8.7% in dry soil). Sulfur altered the carbonate fraction of Cd to the soluble fraction and the residual fraction of Cd and Ni to the non-residual fraction. Compost decreased Cd and increased Ni in sorghum, but enhanced Cd and degraded Ni in grass. Sulfur increased Cd and Ni in both plants, and the increasing rate of Cd was higher in grass than in sorghum, while Ni was higher in sorghum than in grass. These results suggest that compost can be used as an immobilizing agent for Cd in the dry soil and Ni in the wet soil; however, it might be used as mobilizing agent for Cd in the wet soil and Ni in the dry soil. Sulfur (with rate 2.5%) can be used for enhancing the phyto-extraction of Cd and Ni (especially Cd) from contaminated alkaline soils.  相似文献   
285.
Cyanobacterial bloom events in South Taihu Lake cause serious water quality problems and disturb aesthetic view of lake’s environment. In this study, correlations between cyanobacterial blooms and hydro-meteorological factors, including water quality, temperature and precipitation were investigated. Results demonstrated that South Taihu Lake was heavily affected by cyanobacteria and the proliferation of cyanobacteria due to variations in hydro-meteorological factors and water quality conditions. Water quality parameters, including COD, NH3-N, TN and TP improved significantly since 2008 even at an elevated cyanobacterial bloom situation. Correlation analyses have shown that the development of cyanobacterial density and chlorophyll a concentration was sensitive to a wider temperature variation. The optimum temperature for cyanobacteria was 20°C, while extremely low and high temperatures were found to suppress their growth. Moreover, unusual rainfall patterns were measured during the study period (2003–2009), which showed an adverse impact on cyanobacterial development. Findings from this study suggested that seasonal lake’s water quality monitoring; suitable treatment of cyanobacterial blooms and strict policy implementation can solve the water quality issues in highly eutrophic lakes like Taihu.  相似文献   
286.
Environmental Science and Pollution Research - Polypyrrole (PPy) conducting films, doped with 4-amino-3-hydroxynaphthalene sulfonic acid (AHNSA), were electrosynthesized by anodic oxidation of...  相似文献   
287.

Information on the detection of pesticides in fresh water Lakes of Kashmir (Dal and Mansbal) through GC–MS technique is scarce, and also the recovery in biochemical parameters (AST, ALT and ALP) of fish after transferring them to clean media has not been reported yet. The water samples were collected from three sites and analyzed for their pesticide profile by dispersive liquid–liquid micro extraction (DLLME) followed by GC–MS. Influence of pesticides on liver marker enzymes of Cyprinus carpio and Carassius carassius was also investigated. The results obtained showed the presence of three main pesticides viz. chlorpyrifros, dimethoate and dichlorvos in waters of Dal Lake whereas no pesticide was detected in waters of Mansbal. The higher values for AST, ALT and ALP activities and decrease in protein content were obtained in the samples from the Dal Lake compared with those from Mansbal Lake (p < 0.05). These data when compared with the values found in C. carpio and C. carassius from both the Dal Lake and Mansbal Lake kept under laboratory conditions after 15, 30, 45 and 60 days of maintenance in clean media found that during depuration, all the enzyme activities came down significantly (p < 0.05) indicating the compensatory response by the fish against the pesticide stress. Therefore, these parameters could be used as indicators of pesticide pollution in aquatic organisms and were recommended for environmental monitoring for investigating the mechanism involved in the recovery pattern.

  相似文献   
288.
Over the last few decades, electrostatic precipitators (ESPs) have emerged as effective air pollution control devices for treating coal-fired power plant exhausts. Among the components of the ESP, the discharge electrodes are extremely important in determining the collection efficiency of the ESP. Typically, in wet ESPs, the discharge electrodes used must be made of corrosion-resistant alloys, which makes them extremely expensive and heavy. Hybrid composite discharge electrodes have the potential to be lightweight and corrosion-resistant substitute for traditional metal alloy electrodes used in wet ESPs. In this experimental study, a novel hybrid composite electrode (recently patented at Ohio University) is presented as a substitute for traditional metal electrodes in wet ESPs. The samples of hybrid electrodes were fabricated by using carbon fiber composites, combined with metal mesh, in the shape of a long and thin tape. The electrode’s electrical response was evaluated in open atmospheric conditions, while connected to a transformer-rectifier unit to generate a corona current at voltages exceeding 50 kV. Results of these hybrid electrodes were compared with traditional metal electrodes. The hybrid composite discharge electrode produced a uniform corona at comparable power levels to that of metal electrodes, with additional advantages of being compact, lightweight, and highly corrosion resistant. In addition, hybrid composite electrodes exhibited lower corona onset voltage as compared with metal electrodes. The preliminary experimental data are encouraging and show significant potential for this new inexpensive hybrid electrode to replace metal electrodes in wet ESPs, providing comparable (and in some cases exceeding) collection efficiencies with lower ozone generation.

Implications: The newly invented hybrid composite electrode (HCE) performance was evaluated through experimentation with conventional metal electrodes. The HCE performance was comparable to the metal electrodes. The HCE also exhibited uniform corona fields and steady power while maintaining similar and in some cases superior electrical performance as compared with metal electrodes and thus shows a significant potential to substitute metal electrodes in wet ESP systems.  相似文献   

289.
Environment, Development and Sustainability - The tourism sectors consume a high amount of electrical power, which in most cases is supplied by the electrical grid and diesel generator. As a...  相似文献   
290.
Environment, Development and Sustainability - In the hydrologic design of water management infrastructures, rainfall characteristics are often used and the available historical rainfall events in...  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