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   1404篇
  免费   135篇
  国内免费   411篇
安全科学   133篇
废物处理   47篇
环保管理   187篇
综合类   871篇
基础理论   200篇
污染及防治   216篇
评价与监测   200篇
社会与环境   65篇
灾害及防治   31篇
  2024年   16篇
  2023年   25篇
  2022年   62篇
  2021年   58篇
  2020年   75篇
  2019年   59篇
  2018年   78篇
  2017年   81篇
  2016年   87篇
  2015年   80篇
  2014年   94篇
  2013年   151篇
  2012年   109篇
  2011年   127篇
  2010年   69篇
  2009年   98篇
  2008年   69篇
  2007年   94篇
  2006年   76篇
  2005年   64篇
  2004年   43篇
  2003年   46篇
  2002年   44篇
  2001年   31篇
  2000年   31篇
  1999年   22篇
  1998年   25篇
  1997年   20篇
  1996年   21篇
  1995年   20篇
  1994年   5篇
  1993年   11篇
  1992年   9篇
  1991年   9篇
  1990年   5篇
  1989年   6篇
  1988年   6篇
  1987年   4篇
  1985年   1篇
  1984年   1篇
  1983年   2篇
  1982年   3篇
  1981年   3篇
  1980年   3篇
  1979年   2篇
  1978年   1篇
  1975年   2篇
  1972年   1篇
  1971年   1篇
排序方式: 共有1950条查询结果,搜索用时 31 毫秒
981.
Source resolution and risk apportionment of emission source categories for risk reduction purposes can be used to enhance the Bubble Policy of the Clean Air Act. This is performed by incorporating receptor modeling techniques of factor analysis and chemical mass balances to assess noncarcinogenic and carcinogenic inhalation risks to a target population for certain pollutants coming from major emission source categories in a steel plant air shed. Source resolution, using factor analysis, statistically interprets a “source” from ambient data. By subsequently quantifying risks from identified metal emission sources using chemical mass balances and risk apportionment, a total additive risk from main source contributors in the steel plant is estimated. From this methodology, the Bubble Policy can be enhanced by targeting only main risk sources or by “risk-trading” with minor impact sources to reduce the total risk (if deemed significant) without arbitrarily reducing risk for all sources in an industrial source complex’s “bubble.”  相似文献   
982.
本文研究PAN-ACF的主要结构参数,探讨了ACF对SO2的物理吸附、脱附性能以及传质机理,得出传质过程为内扩散控制,并计算出扩散系数D值约为活性炭D的50-170倍。  相似文献   
983.
ABSTRACT: Soil-water conditions provide valuable insight into the hydrologic system in an area. A soil-water balance quantitatively summarizes soil-water conditions and is based on climatic, soil, and vegetation characteristics that vary spatially and temporally. Soil-water balances in the Great Plains of the central United States were simulated for 1951–1980. Results of the simulations were mean annual estimates of infiltration, runoff, actual evapotranspiration, potential recharge, and consumptive water and irrigation requirements at 152 climatic data stations. A method was developed using a geographic information system to integrate and map the simulation results on the basis of spatially variable climatic, soil, and vegetation characteristics. As an example, simulated mean annual potential recharge was mapped. Mean annual potential-recharge rates ranged from less than 0.5 inch in much of the north-central and southwestern Great Plains to more than 10 inches in parts of eastern Texas and southwestern Arkansas.  相似文献   
984.
This paper describes a mathematical model which calculates the time dependencies of the flow rate and composition of the vapour emerging from a pool. A large variety of accidental cases can be covered: continuous or instantaneous spills, on confined or unconfined ground, ideal or non-ideal liquid mixtures in boiling or evaporating conditions. The boiling, when present, is modelled through an equation system comprising the Rachford-Rice relation and the energy balance of the pool, which is assumed to be well-mixed. In the case of a volatile pool, interfacial mass rates are determined taking into account the Stefan flux, and the thermal resistance inside the liquid phase is also considered. In all situations, the energy balance includes the contribution of ground, sun and air. Known experimental data have been used to validate the model.  相似文献   
985.
ABSTRACT: Consumptive loss of water attributable to man-made snowmaking was estimated using an energy balance model and a mass balance procedure. Data from nine field experiments at Colorado ski areas were collected and used in these models. The mean consumptive loss using the energy balance model for the nine experiments was 6.0 percent and 5.8 percent for the mass balance model A thermodynamic relationship and a regression equation were developed to provide a procedure to estimate consumptive loss as a linear function of atmospheric temperature.  相似文献   
986.
ABSTRACT: This study presents an estimate of water balance components for Pacific atolls under average dimatological conditions. Figures show annual potential evapotranspiration, annual recharge for rain-fed and aquifer-fed vegetated areas, and the number of months that potential evapotranspiration exceeds actual evapotranspiration (indicating water stress) under average conditions. The method relies on the assumption that small islands have minimal influence on cloudiness and precipitation. The potential evapotranspiration is computed using the equilibrium evaporation concept, and estimates of monthly soil water storage and recharge follow Thornthwaite's bookkeeping method. Gradients in potential evapotranspiration run primarily north-south, though for the equatorial zone potential evapotranspiration declines from east to west, opposing the trend in rainfall. Recharge estimates range from 250 mm in the central Tuamotu Archipelago and zero in eastern Kiribati to over 2000 mm per year in the southern Caroline Islands (U.S. Trust Territory) and Solomon Islands. The sensitivity of the model to intra-month rainfall variability and a range of available soil moisture values is discussed.  相似文献   
987.
ABSTRACT: Competition for water, concerns for maintaining ground water quality, and compliance with legislative action require quantification of the water resource for high elevation watersheds in the Sierra Nevada. However, meager hydroclimatic data frequently hinder runoff assessments needed for formulating water development policies, and the selection of watershed models for estimating the water resource is limited to those requiring a minimum of observational data. A climatic water budget model and an energy slope and aspect model are employed to estimate the water resource for a small watershed in Sierra Valley north of Lake Tahoe. The models employ different assumptions and computational procedures, but the total water available estimated by both models is very similar. Measured runoff is estimated satisfactorily by the models, but streamflow is not representative of the total water resource because a substantial portion of the available water enters the regional ground water system. This conclusion is supported by hydrologic and geochemical evidence, and ground water recharge is estimated to be at least as great as measured runoff during dry years and nearly twice as large during wet years.  相似文献   
988.
蚯蚓有机废水土地处理试验研究   总被引:4,自引:0,他引:4  
利用蚯蚓的有机废水土地处理是一种符合生态平衡的新的处理技术,在这种处理工艺中,含有蚯蚓的土壤对废水中的COD的吸附去除百分数和有机物负荷均比常规的污水土地处理高两倍以上。这一处理过程的机理符合吸附,再生过程的一级反应动力学。  相似文献   
989.
灾害生态学问题研究   总被引:4,自引:0,他引:4  
严立冬 《灾害学》1995,10(4):90-94
灾害生态学是从生态进化的角度上研究灾害问题,其目的在于通过对生态灾害的界定,生态灾害成因分析,来寻求防止或减轻生态灾害的有效途径.文章从灾害与生态进化的关系入手,阐述了研究灾害生态学问题的重要意义,提出了当前灾害生态学研究的主要问题,为灾害生态学的研究提供了一条新的思路。  相似文献   
990.
地价与房价作为房地产市场的两个重要指标,其水平高低对房地产市场的正常、有序发展起者重要作用。房价与地价在一定范围内、一定条件下相互作用,相互影响。正确分析和处理房价与地价的关系,促进房地产业健康发展,可采取以下措施:土地交易信息公开、透明;土地及时开发,及时入市;加强对土地市场供需结构的宏观调控和经济适用房、廉租房体系的建设等。  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