全文获取类型
收费全文 | 1513篇 |
免费 | 212篇 |
国内免费 | 795篇 |
专业分类
安全科学 | 252篇 |
废物处理 | 45篇 |
环保管理 | 145篇 |
综合类 | 1371篇 |
基础理论 | 260篇 |
污染及防治 | 232篇 |
评价与监测 | 151篇 |
社会与环境 | 49篇 |
灾害及防治 | 15篇 |
出版年
2024年 | 5篇 |
2023年 | 33篇 |
2022年 | 59篇 |
2021年 | 102篇 |
2020年 | 102篇 |
2019年 | 81篇 |
2018年 | 81篇 |
2017年 | 101篇 |
2016年 | 98篇 |
2015年 | 115篇 |
2014年 | 122篇 |
2013年 | 177篇 |
2012年 | 165篇 |
2011年 | 184篇 |
2010年 | 117篇 |
2009年 | 106篇 |
2008年 | 98篇 |
2007年 | 136篇 |
2006年 | 113篇 |
2005年 | 68篇 |
2004年 | 66篇 |
2003年 | 63篇 |
2002年 | 58篇 |
2001年 | 39篇 |
2000年 | 36篇 |
1999年 | 47篇 |
1998年 | 32篇 |
1997年 | 28篇 |
1996年 | 18篇 |
1995年 | 11篇 |
1994年 | 13篇 |
1993年 | 10篇 |
1992年 | 7篇 |
1991年 | 8篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有2520条查询结果,搜索用时 31 毫秒
191.
This study focuses on the verification of test interpretations for different state analyses of diffusion experiments. Part 1 of this study identified that steady, quasi-steady and equilibrium state analyses for the through- and in-diffusion tests with solution reservoirs are generally feasible where the tracer is not highly sorptive. In Part 2 we investigate parameter identifiability in transient-state analysis of reservoir concentration variation using a numerical approach. For increased generality, the analytical models, objective functions and Jacobian matrix necessary for inverse analysis of transient-state data are reformulated using unified dimensionless parameters. In these dimensionless forms, the number of unknown parameters is reduced and a single dimensionless parameter represents the sorption property. The dimensionless objective functions are evaluated for individual test methods and parameter identifiability is discussed in relation to the sorption property. The effects of multiple minima and measurement error on parameter identifiability are also investigated. The main findings are that inverse problems for inlet and outlet reservoir concentration analyses are generally unstable and well-posed, respectively. Where the tracer is sorptive, the inverse problem for the inlet reservoir concentration analysis may have multiple minima. When insufficient measurement data is collected, multiple solutions may result and this should be taken into consideration when inversely analyzing data including that of inlet reservoir concentration. Verification of test interpretation by cross-checking different state analyses is feasible where the tracer is not highly sorptive. In an actual experiment, test interpretation validity is demonstrated through consistency between theory and practice for different state analyses. 相似文献
192.
活性污泥法水处理过程是一个复杂的生化反应过程,伴随有物理化学反应、生化反应、相变过程及物质与能量的转化和传递过程.通过对微生物动力学方程的讨论,进而建立动力学模型,比较了Monod方程和Contois方程分别来模拟有机碳在曝气条件下的生化去除过程.模型主要预测底物浓度、溶解氧、微生物增长等引起的系统响应,为污水处理厂的运行提供指导. 相似文献
193.
194.
195.
溶解氧及活性污泥浓度对同步硝化反硝化的影响 总被引:53,自引:1,他引:52
文章研究溶解氧及活性污泥浓度对同步硝化反硝化效率的影响。研究结果表明:在一定DO范围内,随着反应器内溶解氧浓度的降低,总氮去除率呈上升趋势,即好氧反硝化效率随溶解氧浓度的降低而提高;在一定MLSS范围内,反应器内混合液污泥浓度越高,出水总氮越低,反硝化现象越明显。 相似文献
196.
S. Andronopoulos D. Grigoriadis A. Robins A. Venetsanos S. Rafailidis J.G. Bartzis 《Environmental Fluid Mechanics》2001,1(4):415-440
The strong fluctuating component in the measured concentration time series of a dispersing gaseous pollutant in the atmospheric boundary layer, and the hazard level associated to short-term concentration levels, demonstrate the necessity of calculating the magnitude of turbulent fluctuations of concentration using computational simulation models. Moreover the computation of concentration fluctuations in cases of dispersion in realistic situations, such as built-up areas or street canyons, is of special practical interest for hazard assessment purposes. In this paper, the formulation and evaluation of a model for concentration fluctuations, based on a transport equation, are presented. The model is applicable in cases of complex geometry. It is included in the framework of a computational code, developed for simulating the dispersion of buoyant pollutants over complex geometries. The experimental data used for the model evaluation concerned the dispersion of a passive gas in a street canyon between 4 identical rectangular buildings performed in a wind tunnel. The experimental concentration fluctuations data have been derived from measured high frequency concentrations. The concentration fluctuations model is evaluated by comparing the model's predictions with the observations in the form of scatter plots, quantile-quantile plots, contour plots and statistical indices as the fractional bias, the geometrical mean variance and the factor-of-two percentage. From the above comparisons it is concluded that the overall model performance in the present complex geometry case is satisfactory. The discrepancies between model predictions and observations are attributed to inaccuracies in prescribing the actual wind tunnel boundary conditions to the computational code. 相似文献
197.
198.
199.
佛山市高明区环境空气污染物变化分析 总被引:1,自引:1,他引:0
根据佛山市高明区2007—2012年环境空气监测数据资料,分析该区近6年来空气污染物的变化趋势和影响因素。结果表明,2007—2012年该区空气污染呈现由单一型污染向复合型污染转变,综合污染指数总体上升,污染物以SO2、PM10为主。SO2、NO2浓度呈逐年增长,PM10则呈平稳状态。三者污染浓度最高值均在每年第4季度出现。该区的SO2浓度主要受工业污染源影响;NO2也受工业影响显著,与机动车数量呈正相关;PM10与烟粉尘排放量呈正相关,与降水量呈负相关。因此,改善该区环境空气应着重从控制工业污染源、扬尘污染、机动车排气污染3大方面开展工作。 相似文献
200.
邓继 《环境监测管理与技术》2014,26(1):66-70
选取上海市7家未安装气-气换热器的国控燃煤电厂作为研究对象,从煤质、除尘器、脱硫协同脱除作用以及锅炉工况负荷等方面探讨对颗粒物浓度排放系数 K值产生的影响,得出上述因素通过改变脱硫进口颗粒物浓度值影响 K值,当脱硫进口颗粒物浓度较低、波动范围较小时,其 K值也维持相对稳定的状态;当脱硫进口颗粒物浓度较高、波动范围较大时,其 K值也会发生较大的变化等结论。 相似文献