全文获取类型
收费全文 | 391篇 |
免费 | 39篇 |
国内免费 | 77篇 |
专业分类
安全科学 | 118篇 |
废物处理 | 29篇 |
环保管理 | 24篇 |
综合类 | 176篇 |
基础理论 | 52篇 |
污染及防治 | 60篇 |
评价与监测 | 34篇 |
社会与环境 | 11篇 |
灾害及防治 | 3篇 |
出版年
2023年 | 6篇 |
2022年 | 6篇 |
2021年 | 11篇 |
2020年 | 17篇 |
2019年 | 12篇 |
2018年 | 9篇 |
2017年 | 15篇 |
2016年 | 13篇 |
2015年 | 19篇 |
2014年 | 20篇 |
2013年 | 18篇 |
2012年 | 19篇 |
2011年 | 29篇 |
2010年 | 12篇 |
2009年 | 28篇 |
2008年 | 20篇 |
2007年 | 26篇 |
2006年 | 24篇 |
2005年 | 25篇 |
2004年 | 10篇 |
2003年 | 23篇 |
2002年 | 27篇 |
2001年 | 15篇 |
2000年 | 18篇 |
1999年 | 10篇 |
1998年 | 16篇 |
1997年 | 8篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1984年 | 1篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有507条查询结果,搜索用时 31 毫秒
171.
Irtishad Ahmad Berrin Tansel Jose D. Mitrani 《Environmental monitoring and assessment》2001,72(3):265-276
Indoor air quality has become one of the most seriousenvironmental concerns as an average person spends about 22 hrindoors on a daily basis. The study reported in this article, wasconducted to determine the effectiveness of three commercialHVAC (Heating Ventilation Air Conditioning) duct cleaning processes in reducing the level of airborne particulate matterand viable bioaerosols. The three HVAC sanitation processeswere: (1) Contact method (use of conventional vacuum cleaning ofinterior duct surfaces); (2) Air sweep method (use of compressedair to dislodging dirt and debris); (3) Rotary brush method(insertion of a rotary brush into the ductwork to agitate anddislodge the debris). Effectiveness of these sanitationprocesses was evaluated in terms of airborne particulate andviable bioaerosol concentrations in residential homes. Eightidentical homes were selected in the same neighborhood. Twohomes were cleaned using each procedure and two were used ascontrols. It was found that both particle count readings andbioaerosol concentrations were higher when cleaning was beingperformed than before or after cleaning, which suggests thatdirt, debris and other pollutants may become airborne as aresult of disturbances caused by the cleaning processes.Particle count readings at 0.3 micron size were found to haveincreased due to cigarette smoking. Particle counts at 1.0micron size were reduced due to HVAC duct cleaning. Post-levelbioaerosol concentrations, taken two days after cleaning, werefound to be lower than the pre-level concentrations suggestingthat the cleaning procedures were effective to some extent.Homes cleaned with the Air Sweep procedure showed the highestdegree of reduction in bioaerosol concentration among the threeprocedures investigated. 相似文献
172.
173.
Amvrossios C. Bagtzoglou Andrei Novikov 《Journal of the American Water Resources Association》2007,43(1):207-219
Abstract: This paper presents a numerical investigation of approaches to enhance the mixing and dispersion processes in tidal areas by effecting changes in the natural estuary system. It compares the impact of various estuary modifications stemming from human intervention to pollutant dispersion and chaotic flow within the estuary including the implications of alteration of the original channel shape, change of the channel bathymetry, and modification of the tidal signal. Our findings indicate that chaotic flow analysis is similar in many regards, but not all, to conventional dispersion analysis. Specifically, we conclude that (1) simplification of the flow regime reduces chaotic flow patterns and tracer particle dispersion, (2) creation of extensively protruding barriers and/or installation of barriers on opposite sides of the main stem of the estuary enhances particle dispersion and chaotic mixing, (3) installation of underwater berms has relatively minor beneficial, but highly localized, effects on chaotic regime and particle dispersion, and (4) increasing the tidal signal amplitude was shown to increase chaotic and dispersion properties of the estuarine system. A parametric study investigating the effect of several geometrical configurations and tidal signals on characteristics of chaotic flows concludes the paper. 相似文献
174.
175.
Willem van Hees 《Journal of the American Water Resources Association》1977,13(2):215-230
ABSTRACT: A number of aspects of the discharging of non-oily wastewaters by transiting ships are treated in this overview paper. In the introduction, options to discharging (the use of holding tank, on board treatment) and the impact of changing regulations are discussed. Assessment of the effects of sewage discharges on coastal waters required that data, at first not available, be generated. An account is given of the characterization of Navy shipboard wastewaters and of experiments involving sewage discharges at sea, measurements of water quality before, during and after an amphibious operation, and fore and aft of transitting Navy ships. A better understanding of sewage dilution after discharge led to the verification of a method for controlled discharging of sewage (and other wastewaters). This method permits limiting the coliform bacteria count in the ship's wake to values below acceptable limits. The final sections contain information on long range effects of ships’sewage discharges, obtained in studies by the U.S. Navy and others, as well as public health considerations. 相似文献
176.
G. Vachon P. Louka J-M. Rosant P.G. Mestayer J-F. Sini 《Water, Air, & Soil Pollution: Focus》2002,2(5-6):127-140
A full scale experiment has been performed in a streetcanyon, the Rue de Strasbourg in Nantes (France). Thiscampaign, the Nantes'99 experiment, provided a detaileddata base documenting, amongst others, the production ofturbulent kinetic energy (TKE) by vehicles within thestreet. Airflow and CO concentration measurements have beenanalysed during days with low wind perpendicular to thestreet axis, i.e. for conditions expected to greatly favourthe enhancement of the turbulence produced by traffic onflow and dispersion within the street canyon. It is shownthat traffic is associated with an increase in turbulentkinetic energy at the lowest levels of the street,especially at the leeward side of the street. It issuggested that turbulent kinetic energy increases with thenumber of vehicles up to a threshold value and thendecreases when vehicles form a `block' shape that limitsthe additional production of turbulence. Moreover, it issuggested that traffic-produced turbulence affectspollutant dispersion reducing CO concentration at the lowerlevels of the leeward side of the street from a thresholdvalue of TKE equal to about 0.15 m2 s-2. On the other hand, high traffic density generates less turbulencewhich in turn leads to a lower pollutant dispersion. 相似文献
177.
M. Ketzel P. Louka P. Sahm E. Guilloteau J.-F. Sini N. Moussiopoulos 《Water, Air, & Soil Pollution: Focus》2002,2(5-6):603-613
Microscale computational fluid dynamics (CFD) modelsdeveloped in different European countries were applied towell defined test cases comprising a variety of 2 and 3dimensional configurations for which measurements from windtunnel or field studies were available. This paper presentsthe results of five CFD codes employing the widely used`standard k--model' (CHENSI, CHENSI-2, MIMO, MISKAM, TASCflow) for a street canyon in Hannover, Germany(Göttinger Strasse). Firstly the characteristics of theflow field predicted by the different codes are comparedwith high spatial resolution wind tunnel measurements;secondly the calculated concentration fields are comparedwith field and wind tunnel data. Both agreements (e.g. forthe general flow and concentration fields) anddisagreements (e.g. for the level of concentration) areobserved in the comparison. The discussion aims atexplaining the differences along with giving somesuggestions to CFD model users on how to calculate suchcomplex flows, but also to experimentalists on whereconcentration measurements should be taken in order to bemore representative for a whole street and to avoiddistinct local effects. 相似文献
178.
基于GIS的城市最小生态用地空间分析模型研究——以深圳市为例 总被引:13,自引:3,他引:10
21世纪,全球范围内城市化已经成为人类社会发展的必然趋势,城市扩张不可避免地将大量的森林、农田、草地、湿地和水域等发挥着重要生态服务功能的生态用地转化为城市建设用地,对城市、区域乃至全球的生态系统造成较大的影响。在未来快速城市化过程中,保护必需的生态用地对于维持城市自身生态系统健康、改善城市居民生活质量和城市可持续发展有着重要意义。研究以中国经济特区深圳市为例,将景观生态概念模型与生态系统服务功能价值评估方法结合起来,在GIS技术的支持下,构建了城市最小生态用地空间分析模型,并分别按照保留城市面积30%、40%、50%和60%生态用地的4种情景,分析最小生态用地空间分布的合理性,结果表明论文所构建的最小生态用地模型能够很好地将城市当中具有重要生态系统服务功能的土地提取出来。 相似文献
179.
Although several studies on the dispersion of heavy toxic gas released from ruptured tanks on vehicles during transportation have considered complex terrain such as urban buildings, the influence of trees on the flow field in urban areas during gas dispersion tends to be ignored. In this study, a Computational Fluid Dynamics (CFD) model was proposed to investigate the characteristics of gas release and dispersion from loaded vehicle in the urban environment. In this model, the tree crown was treated as a porous medium, and the influence of drag due to the crown was incorporated into the model by a momentum source term through a user-defined function. In this study, the dynamic characteristics of chlorine (Cl2) dispersion under the conditions of building distribution, tree species and porosities were comprehensively analysed, to cover the influence of urban complexity, leaf density, and tree planting configuration. The results show that compared with flat terrain, the presence of urban buildings will prolong the dense gas retention time and increase the dangerous distance. It is found that the horizontal dispersion distance can increase by 63% and the isosurface of 25 ppm hazardous gas can increase by 130% with the introduction of buildings. Compared with the terrain with only buildings, the introduction of arbors or shrubs can result in a 147% or 359% increase in the maximum concentration. Also, trees will prolong the dispersion duration. It is also found that the higher the porosity, the less the wind blocking effect, and the weaker the ability of capturing gas. The wind field affected by arbores and shrubs are different in height, and arbores capture more Cl2. Planting short shrubs around buildings can effectively reduce the spread of harmful gases. 相似文献
180.