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   3217篇
  免费   425篇
  国内免费   763篇
安全科学   393篇
废物处理   104篇
环保管理   323篇
综合类   2203篇
基础理论   312篇
污染及防治   305篇
评价与监测   660篇
社会与环境   84篇
灾害及防治   21篇
  2024年   10篇
  2023年   65篇
  2022年   103篇
  2021年   132篇
  2020年   139篇
  2019年   137篇
  2018年   142篇
  2017年   164篇
  2016年   184篇
  2015年   198篇
  2014年   203篇
  2013年   230篇
  2012年   225篇
  2011年   247篇
  2010年   160篇
  2009年   168篇
  2008年   159篇
  2007年   209篇
  2006年   240篇
  2005年   188篇
  2004年   160篇
  2003年   202篇
  2002年   150篇
  2001年   141篇
  2000年   126篇
  1999年   77篇
  1998年   43篇
  1997年   43篇
  1996年   38篇
  1995年   26篇
  1994年   23篇
  1993年   9篇
  1992年   12篇
  1991年   10篇
  1990年   15篇
  1989年   6篇
  1988年   4篇
  1987年   8篇
  1986年   1篇
  1984年   1篇
  1982年   1篇
  1981年   2篇
  1973年   1篇
  1972年   2篇
  1971年   1篇
排序方式: 共有4405条查询结果,搜索用时 184 毫秒
941.
厌氧-气浮-UASB-SBR工艺处理酒精废水   总被引:2,自引:0,他引:2  
介绍了厌氧-气浮-UASB-SBR处理工艺在酒精废水处理工程中的实际应用,分析并总结了工程设计及运行的经验。实践表明,经厌氧-气浮-UASB-SBR的工艺处理后,废水中COD和SS总去除效率分别可达到99.6%和99.8%以上,并可以回收大量的沼气和部分废水回用于生产过程中。该工艺具有运行稳定和处理效率高等优点,为企业带来了良好的经济效益和社会效益。  相似文献   
942.
二次风口的合理布设是实现炉膛内气体混合均匀、反应完全的有效措施之一,运用CFD技术进行二段往复炉排焚烧炉二次风口的辅助设计,借助PHOENICS软件模拟二次风口对炉内流场的影响。通过模拟发现,二次风口的布设可明显提高烟气的湍流程度.前后墙各设一排直径为0.04m的二次风口可以实现最佳的炉膛流场工况。  相似文献   
943.
A model is developed to predict the rate of mass transfer between a double-layer material and indoor air. The model allows non-uniform initial material-phase concentrations in each of the two layers and a transient influent gas-phase concentration to be considered. This model builds on a recently validated single-layer model and should prove useful in predicting the behavior of double-layer material assemblies. Many indoor furnishings and building structures are comprised of layers of different material. The approach taken here represents a first step in the development of a more generally applicable multi-layer model. An analytical solution to the double-layer model is obtained and a parametric analysis is performed illustrating the behavior of the model as a function of the primary model parameters. The paper concludes by examining the potential use of thin diffusion barriers to reduce material emission rates and a hypothetical example of emissions from an adhesive that is part of an adhesive/material assembly.  相似文献   
944.
Sorption of emitted gas-phase organic compounds onto material surfaces affects environmental tobacco smoke (ETS) composition and exposures indoors. We have introduced a new metric, the exposure relevant emission factor (EREF) that accounts for sorptive uptake and reemission to give the mass of individual ETS constituents available for exposure over a day in which smoking occurs. This paper describes month-long experiments to investigate sorption effects on EREFs and potential ETS exposures under habitual smoking conditions. Cigarettes were smoked in a 50-m3 furnished room over a 3-h period 6–7 days per week, with continuous ventilation at 0.3, 0.6, or 2.1 h−1. Organic gas concentrations were measured every few days over 4-h “smoking”, 10-h “post-smoking” and 10-h “background” periods. Concentration patterns of volatile ETS components including 1,3-butadiene, benzene and acrolein were similar to those calculated for a theoretical non-sorbing tracer, indicating limited sorption. Concentrations of ETS tracers, e.g. 3-ethenylpyridine (3-EP) and nicotine, and lower volatility toxic air contaminants including phenol, cresols, and naphthalene increased as experiments progressed, indicating mass accumulation on surfaces and higher desorption rates. Daily patterns stabilized after week 2, yielding a steady daily cycle of ETS concentrations associated with habitual smoking. EREFs for sorbing compounds were higher under steady cycle versus single-day smoking conditions by 50% for 3-EP, and by 2–3 times for nicotine, phenol, cresols, naphthalene, and methylnaphthalenes. Our results provide relevant information about potential indirect exposures from residual ETS (non-smoker enters room shortly after smoker finishes) and from reemission, and their importance relative to direct exposures (non-smoker present during smoking). Under the conditions examined, indirect exposures accounted for a larger fraction of total potential exposures for sorbing versus non-sorbing compounds, and at lower versus higher ventilation rates. Increasing ventilation can reduce indirect exposures to very low levels for non-sorbing ETS components, but indirect routes accounted for 50% of potential nicotine exposures during non-smoking periods at all ventilation rates.  相似文献   
945.
Determination of volatile organic compounds (VOCs) formed one part of the EU-EXPOLIS project in which the exposure of European urban populations to particles and gaseous pollutants was studied. The EXPOLIS study concentrated on 30 target VOCs selected on the basis of environmental and health significance and usability of the compounds as markers of pollution sources. In the project, 201 subjects in Helsinki, 50 in Athens, 50 in Basel, 50 in Milan and, 50 in Oxford and 50 in Prague were selected for the final exposure sample. The microenvironmental and personal exposure concentrations of VOCs were the lowest in Helsinki and Basel, while the highest concentrations were measured in Athens and Milan; Oxford and Prague were in between. In all cities, home indoor air was the most significant exposure agent. Workplace indoor air concentrations measured in this study were generally lower than the home indoor concentrations and home outdoor air played a minor role as an exposure agent. When estimating the measured personal exposure concentrations using the measured concentrations and time fractions spent at home indoors, at home outdoors, and at the workplace, it could be concluded that these three microenvironments do not fully explain the personal exposure. Other important sources for personal exposure must be encountered, the most important being traffic/transportation and other indoor environments not measured in this study.  相似文献   
946.
等离子体与光催化复合技术净化污水处理泵站臭气   总被引:1,自引:0,他引:1  
用一种等离子体-光催化复合技术净化污水处理泵站臭气,研究表明该复合技术具有较显著的协同促进效应,通过改变等离子体发生单元与光催化单元的距离以及在两者之间放置去静电网,可消除等离子体单元产生的负电荷对光催化单元的不利影响,进一步提高其复合效应。同时还对这一复合技术产生协同效应的机理进行了分析,并在污水处理泵站实地考查了这种复合技术对臭气的净化效果。该技术对臭气中NH3的降解率可达46.1%,对H2S的降解率可达67.3%。  相似文献   
947.
空气自动监测系统的仪器仪表多样化,以及数据采集装置和数据格式的差异,给系统软硬件的集成,以及数据应用和管理带来了不便,也是构成空气自动监测信息化进程中的技术瓶颈之一,通过对空气自动监测系统软件开发和数据整合模式的对比分析,探讨了解决问题的途径。  相似文献   
948.
The concentration of sulphate on limestone surfaces of the external walls of churches in Malta is shown to be related to their position and distance from a power station, the main local point source of sulphur dioxide pollution. Limestone powder collected from these surfaces was examined for the presence of particles which, under low-power optical microscopy, appear as shiny black amorphous bodies which were interpreted as soot particles; the abundance of these bodies was expressed as a black particle count (BPC). The degree of sulphation and BPC were shown to be correlated with each other and both appeared to be strongly dependent on the prevailing wind. The BPC contour map indicated an important contribution to the parameter from vehicular traffic. It is suggested that the degree of sulphation and BPC of limestone surfaces from the built environment should function as environmental indicators of the relative air quality with respect to SO2 and soot pollution. This data is possibly more accurately representative of the relative long-term air-quality status of different areas of habitation than that deduced from single or episodic measurements of atmospheric pollutant levels.  相似文献   
949.
窑炉烟气净化和控制燃烧相结合技术   总被引:2,自引:0,他引:2  
窑炉烟气污染治理技术的关键是要解决降低高温烟气以实现机械排烟的条件,而在采用配风形式降低了高温烟气和通过选用适宜的湿式净化技术装置解决了污染问题的同时,必须考虑控制窑炉燃烧,以保证窑炉的正常运行,并改善窑炉燃烧条件,使窑炉的产品质量得到保证和提高,实现环保与节能降耗的双重效果。  相似文献   
950.
浅析相关因子对空气负离子水平的影响   总被引:10,自引:0,他引:10  
空气负离子是一种重要的森林旅游资源,其保健功能迎合了人们追求生态健康的旅游心理.论文着重对其影响因素进行分析,借助于SPSS统计软件对若干因子进行一元回归分析.在分析结果的基础上,对森林旅游地有关保健设施的规划和设计提供一定的建议。  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