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   1677篇
  免费   1篇
  国内免费   4篇
安全科学   461篇
废物处理   9篇
环保管理   107篇
综合类   903篇
基础理论   83篇
污染及防治   84篇
评价与监测   25篇
社会与环境   7篇
灾害及防治   3篇
  2022年   5篇
  2016年   9篇
  2014年   7篇
  2013年   60篇
  2011年   9篇
  2010年   11篇
  2009年   12篇
  2008年   13篇
  2007年   10篇
  2006年   9篇
  2005年   11篇
  2004年   164篇
  2003年   161篇
  2002年   78篇
  2001年   42篇
  1998年   50篇
  1997年   17篇
  1996年   8篇
  1995年   59篇
  1994年   52篇
  1993年   39篇
  1992年   33篇
  1991年   26篇
  1990年   36篇
  1989年   27篇
  1988年   36篇
  1987年   30篇
  1986年   23篇
  1985年   16篇
  1984年   14篇
  1983年   16篇
  1982年   12篇
  1981年   6篇
  1979年   6篇
  1976年   6篇
  1975年   9篇
  1973年   10篇
  1961年   5篇
  1931年   4篇
  1923年   4篇
  1922年   4篇
  1921年   4篇
  1920年   4篇
  1919年   49篇
  1918年   46篇
  1917年   37篇
  1916年   58篇
  1915年   38篇
  1914年   73篇
  1913年   108篇
排序方式: 共有1682条查询结果,搜索用时 15 毫秒
251.

Goal and Scope

The constant increase of traffic and the rising energy and material consumption both in industry and trade as well as in private households mean a constant challenge to environmental protection and to the air pollution control. With the commencement of the Federal ambient pollution control act in April 1974, the legal basis for the monitoring of air pollution was created. In future, the limit values laid down in the Council Directive 1999/30/EG, 2000/69/EG and 96/62/EG, will be valid. In town and regional planning there is a great demand for a simple index to evaluate the air quality. From the available data of PM10, NO2, O3, CO, SO2, trends of the air quality will be derived.

Methods

The indices LQI and TLQ suggested by Mayer et al. (2002) were calculated for selected stations of the air pollution monitoring network (ZIMEN) in Rhineland-Palatine. All analysis are based on hourly recorded value, Mean values and frequency distributions are used for the interpretation. Furthermore, the characteristics and trends of the indices under different weather conditions were examined and discussed.

Results

The examination figures out that the air pollutions indices at all stations show similar patterns in the period between January 2001 and December 2002. Neither the LQI, nor the TLQ shows an annual variation. Existing variations are mainly controlled by the general weather situation and the air temperature. High values of the indices appear at extremely high or low mean daily air temperature. The absolute value of the air pollution index is determined by local pollution factors.

Outlook and Recommendations

Both indices are well suitable to evaluate the air quality and to assess the effects of state-aided measures for air pollutant control. Therefore, the indices TLQ and LQI should be published as an additional information in the world wide web.  相似文献   
252.
We evaluated the genotoxicity of dichloromethane (DCM) extracts of PCB-contaminated soil before and after the soil had been treated by a base-catalyzed dechlorination process. The treatment process involves heating a mixture of the soil, polyethylene glycol (or hydrocarbons with boiling points of 310–387°C), and sodium hydroxide to 250–350°C. Dechlorination reduced by >99% the PCB concentration of the soil, which was initially 2,200 ppm. The DCM extracts of both control and treated soils were not mutagenic in strain TA100 of Salmonella, but they were mutagenic in strain TA98. Based on results in strain TA98, the base-catalyzed dechlorination process reduced the mutagenic potency of the soil by approximately one-half. The DCM extracts of the soils before and after treatment were equally genotoxic in a prophage-induction assay in . , which detects some chlorinated organic carcinogens that are not detected by the Salmonella mutagenicity assay. These results suggest that treatment of PCB-contaminated soil by base-catalyzed dechlorination reduced the mutagenicity of the soil slightly.  相似文献   
253.
254.
255.
256.
257.
258.
259.
260.
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