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   16223篇
  免费   195篇
  国内免费   143篇
安全科学   545篇
废物处理   441篇
环保管理   2808篇
综合类   3565篇
基础理论   3862篇
环境理论   13篇
污染及防治   3980篇
评价与监测   772篇
社会与环境   481篇
灾害及防治   94篇
  2018年   159篇
  2017年   185篇
  2016年   262篇
  2015年   218篇
  2014年   271篇
  2013年   1351篇
  2012年   426篇
  2011年   580篇
  2010年   415篇
  2009年   520篇
  2008年   577篇
  2007年   648篇
  2006年   565篇
  2005年   432篇
  2004年   454篇
  2003年   494篇
  2002年   417篇
  2001年   524篇
  2000年   387篇
  1999年   262篇
  1998年   204篇
  1997年   182篇
  1996年   236篇
  1995年   228篇
  1994年   261篇
  1993年   225篇
  1992年   221篇
  1991年   217篇
  1990年   242篇
  1989年   224篇
  1988年   199篇
  1987年   186篇
  1986年   179篇
  1985年   194篇
  1984年   172篇
  1983年   194篇
  1982年   199篇
  1981年   203篇
  1980年   171篇
  1979年   171篇
  1978年   162篇
  1977年   155篇
  1976年   148篇
  1975年   123篇
  1974年   152篇
  1973年   129篇
  1972年   134篇
  1971年   109篇
  1970年   113篇
  1967年   116篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
961.
The tape samplers using lead acetate impregnated paper tapes for continuous hydrogen sulfide sampling are subject to a number of errors which can throw considerable doubt on the accuracy of H2S concentrations being measured. Some of the errors have been minimized with a change in the humidification system and a reduction of the lamp intensity in the optical system.  相似文献   
962.
The nitrate ion selective electrode was investigated as an alternative approach to the present colorimetric determination of nitrate resulting from oxidative absorption of nitrogen oxides from combustion effluents. The electrode offers advantages of speed and relatively simple experimental procedure. Replicate measurements of 10?4–10?2M nitric acid solutions using bracketing standards show that the electrode approach is capable of good precision (coefficient of variation = ±4%). Comparison of a method utilizing the nitrate electrode with the more laborious phenol disulfonic acid method for the measurement of nitrogen oxides in both oil and gas fired combustion effluents showed agreement within 4% of the mean even in the presence of high levels of SO2. The correlation coefficient found for PDS vs nitrate electrode is 0.987.  相似文献   
963.
964.
The study considers a range of possible effects on the transportation industry, satellite industries, the labor market, and the economy which may be anticipated in the event mass production of unconventional low emission automotive propulsion systems should occur, whether as a consequence of federal intervention, or not. A postulated 1 976 Otto Cycle Internal Combustion Engine equipped with a dual catalyst manifold reactor and other “conventional” emission control devices was compared in detail with a Regenerative Free Turbine Engine and a Rankine Cycle Engine, as specified by the contracting agency. Manufacturing costs, operating and ownership costs, consumer demand, inter-industry effects, employment, resource requirements, and international trade implications were analyzed in depth under a number of plausible sets of policy constraints and parametric variations. Principal conclusions are that conversion over a 10 year period is feasible, that manufacturing cost differentials are less critical than fuel consumption and cost differentials, that industry/employment impacts are minor, and that resource/trade effects are dominated by petroleum imports. Implications for federal policy are discussed.  相似文献   
965.
At the Clairton Coke Works of the United States Steel Corporation (the world’s largest coke plant), with coal charges of about 30,000 net tons per day, a system designated as “stage charging” has been developed for charging coal into the coke oven chamber without emissions to the atmosphere. The principles of the system are based on controlled sequential flow of the coal from the charging hoppers, during which the oven chamber is maintained under a very slight negative pressure condition by use of steam aspiration in the offtakes for on-the-main charging. The techniques are basic but require knowledge of the coal characteristics, adequate and properly maintained aspirating systems, including clean offtake piping, control of coal volume in the individual hoppers, and last, and probably most important, adherence by the operating crew to specific charging and leveling practices.  相似文献   
966.
A study was conducted to evaluate performance and cost comparisons of fabric filters and alternate fine particulate control techniques. In relating the removal of fine particulate to costs, due to the lack of fractional efficiency data, it was found necessary to treat a specific application in order to make the study manageable. The case chosen is that of the coal fired industrial boiler since Enviro-Systems has a pilot program in this application area.  相似文献   
967.
As many of you know, I previously served as Deputy Administrator of the Environmental Protection Agency at a time when the problem of air pollution control was reaching a peak of public awareness. The work of the Air Pollution Control Association in investigating facts and accelerating the development of solutions earned my high respect then and my continued admiration now.  相似文献   
968.
The body of information presented in this paper is directed to design engineers, operating management and others who may be concerned with the prevention of atmospheric emissions from electric arc steelmaking furnaces. Inland Steel Co. has recently begun operating its first electric furnace shop. Air pollution control equipment for the shop was installed to meet or exceed the legal requirements of applicable air pollution ordinances and regulations. General shop production requirements were established at 100 tons of steel per hour (maximum) to meet sales forecasts and intermediate production facility requirements. Conventional swing roof furnace design was selected for the pair of furnaces in the shop.  相似文献   
969.
The Environmental Protection Agency has recommended or specified methods for the measurement of participate concentrations in flue gases. The EPA Train for this measurement originally comprised two segments: the front half and the impinger train downstream from the filter proper. This review examines the controversial areas implicit in the use of this EPA Train or the revised EPA train which eliminates the impinger train.  相似文献   
970.
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