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   20239篇
  免费   4583篇
  国内免费   483篇
安全科学   2040篇
废物处理   369篇
环保管理   4972篇
综合类   10840篇
基础理论   2228篇
环境理论   1篇
污染及防治   1876篇
评价与监测   1540篇
社会与环境   931篇
灾害及防治   508篇
  2025年   118篇
  2024年   398篇
  2023年   565篇
  2022年   624篇
  2021年   626篇
  2020年   750篇
  2019年   606篇
  2018年   496篇
  2017年   817篇
  2016年   892篇
  2015年   952篇
  2014年   899篇
  2013年   1212篇
  2012年   1323篇
  2011年   1434篇
  2010年   1008篇
  2009年   1019篇
  2008年   768篇
  2007年   1236篇
  2006年   1248篇
  2005年   952篇
  2004年   864篇
  2003年   861篇
  2002年   753篇
  2001年   613篇
  2000年   581篇
  1999年   507篇
  1998年   371篇
  1997年   331篇
  1996年   304篇
  1995年   269篇
  1994年   225篇
  1993年   211篇
  1992年   162篇
  1991年   116篇
  1990年   92篇
  1989年   85篇
  1988年   76篇
  1987年   78篇
  1986年   56篇
  1984年   52篇
  1983年   63篇
  1982年   61篇
  1981年   74篇
  1980年   88篇
  1979年   78篇
  1978年   54篇
  1977年   48篇
  1973年   45篇
  1971年   58篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
挥发性有机化合物及其二氧化钛光催化控制技术   总被引:4,自引:3,他引:4  
介绍了挥发性有机化合物的来源、危害以及控制技术与措施,详细论述了纳米二氧化钛光催化控制技术的控制机理和应用现状。  相似文献   
952.
白音华二号矿滑坡区边坡治理工程是针对稳定性差的南帮非工作帮和南排土场构成的复合边坡进行的。滑坡体受多层弱层控制,治理过程中易导致边坡失稳,所以治理工程采取分区开采的条采方案,充分利用边坡治理的三维效应来进行边坡的失稳破坏研究和稳定性分析。选取滑坡区的典型剖面作为研究对象,基于强度折减方法(SRM),应用有限差分FLAC3D软件,在两种开挖条件下,对含多弱层的复合边坡的稳定性规律和破坏机制进行了数值模拟分析,揭示了多弱层对复合边坡的失稳破坏及稳定性的影响。研究结果表明,治理工程中,弱层被揭露一定宽度,滑体沿煤底板弱层水平错动、竖直方向拉裂破坏;随弱层暴露宽度的增加,边坡稳定性明显降低,说明治理边坡具有三维效应;开挖至3-3煤层底板,开挖坡角20°,弱层暴露宽度为400m,边坡的稳定系数刚好达到安全储备系数1.1,建议矿方首选此方案,可以最大限度的回收煤炭资源。  相似文献   
953.
密封消解法测定高氯离子含盐废水COD_(Cr)的探讨   总被引:6,自引:0,他引:6  
针对国标重铬酸钾法测定高氯离子含盐废水CODCr时的不足,提出用密封消解法来测定高盐废水CODCr的观点,通过丁酮氧化率、氯离子干扰、混配水样和实际水样测定结果的比较,对国标法和密封消解法进行了验证。试验结果表明:在测定高氯离子含盐废水CODCr值时,密封消解法优于重铬酸钾法,能够真实准确地反映废水的CODCr。  相似文献   
954.
孟庆峰 《环境与发展》2020,(2):26-26,28
本文首先介绍了我国当前的河湖水环境现状,分析了我国水资源存在的一系列问题,主要问题包括水体污染和富营养化;河湖面积严重萎缩,河湖水的功能逐渐退化;难以降解的有机污染物污染量加大。有针对性地提出了改善我国河湖水环境的管理以及治理模式,进一步落实了保护河湖水环境工作,加强水资源周围生态环境的文明建设,实现河湖水环境的可持续发展。  相似文献   
955.
    
ABSTRACT: Erosion from construction sites significantly affects water quality in receiving streams. A rainfall simulator was used to evaluate the effectiveness of different methods for controlling erosion from construction sites. Erosion control methods investigated included dry and liquid applications of polyacrylamide (PAM), hydroseed, and straw mulch. Fertilizer was also applied to each plot to examine the effectiveness of the methods in reducing nutrient losses in runoff. Runoff samples were analyzed for total suspended solids (TSS), nitrate, total Kjeldahl nitrogen (TKN), ammonium, total phosphorus (TP), and orthophosphate. Among all treatments investigated, straw mulch was the most effective treatment for controlling TSS and nutrient losses during short term and long term simulations. The low liquid PAM (half the recommended PAM) treatment resulted in the highest reduction in runoff, TSS bound nitrogen, and total nitrogen (TN) concentrations and loadings. The study results indicate that a high application rate (twice the recommended rate) of PAM could actually increase runoff and TSS losses. At a low application rate, both liquid and dry PAM were effective in reducing TSS and nutrient losses in runoff. However, application of the liquid form of PAM to construction sites is more practical and perhaps more economical than applying the PAM in the dry form.  相似文献   
956.
    
Due to increasing freshwater demand and limited availability of resources, conservation and recycling of greywater are getting attention worldwide. Greywater (GW) is considered a potential contender to different types of industrial wastewater in terms of recyclability, toxicity, and reusability. The reuse and treatment methodologies in the case of LGW mainly depend on parameters such as pH, Biochemical oxygen demand (BOD), Chemical oxygen demand (COD), Total dissolved solids (TDS), Total suspended solids (TSS), turbidity, ionic concentration, surfactants, and microbial growth. Available literature suggests that domestic as well as commercial laundries are major contributors to greywater around the globe. This paper presents the results of investigations conducted on the quantity and quality of greywater generated from domestic urban laundries. Various factors were observed that influence the quantity of generated LGW such as family size, type of washing (machine or manual), and composition of LGW influenced by the work profile of family members, etc. The average values of BOD, COD, TSS, TDS, turbidity, Chloride (Cl−), Sulphate (SO42−), Fluoride (F−), Nitrate (NO3−), and anionic surfactants as MBAS (methylene blue active substances) were observed as 265.73 mgL−1, 1754.67 mgL−1, 469.13 mgL−1, 1837.73 mgL−1, 281.8 NTU, 438.6 mgL−1, 87.93 mgL−1, 0.87 mgL−1, 6.83 mgL−1, and 16.45 mgL−1, respectively. The average concentration of Escherichia coli and total coliforms was observed to be 73.4 MPN/100 mL (most probable number per 100 mL) and 386.2 MPN/100 mL, respectively. The high values of selected parameters necessitate the planning of greywater treatment in urban locations for re-utilization. This study also revealed that a huge amount of freshwater is being converted to greywater by domestic laundries that can be re-utilized for non-potable purposes after some treatment.  相似文献   
957.
    
This paper proposes a modified conditional value-at-risk interval two-stage stochastic programming coordination model (MCITSP) for water allocation and illustrates its advantages in risk aversion and pollution control. We analyze its performance in maintaining the equity of water use in various sectors, which is specifically reflected in the water satisfaction of multiple users. In this paper, the MCITSP model and original ITSP model are applied to the case of the Hanjiang River Basin, and three scenarios of water availability are set up to provide theoretical support for water allocation. Our results show that the MCITSP model with a higher risk coefficient has a stronger ability to avoid risks. The MCITSP model simultaneously controls pollutant discharge and guarantees economic benefits, making it superior to the ITSP model under different scenarios. Water shortages primarily affect the agricultural sector, due to its high water demand and low economic value, and the MCITSP model plays a positive role in maintaining equity and coordinating water conflicts among multiple users. Managers can choose appropriate model parameters according to their preferences to formulate more reasonable decisions.  相似文献   
958.
    
For developing countries, the proportion of households covered by improved water resources is conventionally used to assess the water stress situation. However, in a developing country like India with a high population growth rate, water demand and supply are considerably mismatched. An agro-based economy with large variations in socio-economic conditions and changing rainfall patterns across the states imposes greater challenge on water resources. Therefore, there is a need to assess the water situation across the country in a holistic manner. This paper proposes application of the Water Poverty Index as a comprehensive policy tool to assess actual water-stress situation across 20 major states in India. This index covers important socio-economic parameters such as access, capacity, use and environment in addition to water resources of each state. The results and findings are expected to be of use to policymakers and implementing agencies. In view of policy formulation, a state performing well on a Water Poverty Index component can act as a benchmark for another state.  相似文献   
959.
ABSTRACT: Landsat radiance values were processed at two different (single and double) levels of accuracy to estimate chlorophyll a, turbidity, and suspended sediment in Lake Okeechobee, Florida. Both ordinary least square and ridge regression analyses were used to establish a relationship between water quality parameters and Landsat radiance. Radiance measurements made at greater precision (double level) gave a better solution in this application. The ridge regression analysis for double level not only can reduce the total mean square error about 13–20 percent and confidence interval about 6–28 percent as compared to ordinary least square analysis, but it can also change the interpretation of analysis results.  相似文献   
960.
ABSTRACT The Republic of South Africa, legatee of a three-century history of recurring drought, is firmly committed to a program of the optimum use of its water for the national benefit. Its water law encourages centralized planning in that water is held to be the property of the state and is assignable without requiring acquiescence by the basin or province of origin. Interbasin diversions from the Tugela River to the Vaal River Basin, from the Orange River to the Fish and Sundays River Basins, and from several basins to Cape Town are under construction as are facilities for water importation from Lesotho and Angola. For satisfaction of demands beyond the year 2000 the nation may depend increasingly on a shift of its power production and water-using industry from the coal fields of the central plateau to nuclear power development with associated desalination along its coasts. Alternatively, and preferably, it may cooperate in a co-prosperity bloc in Southern Africa aiding the economies of its neighbors by development for mutual advantage of the water and power resources of the Okavango and other northern rivers.  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