全文获取类型
收费全文 | 44604篇 |
免费 | 473篇 |
国内免费 | 576篇 |
专业分类
安全科学 | 1334篇 |
废物处理 | 2014篇 |
环保管理 | 5282篇 |
综合类 | 7431篇 |
基础理论 | 11760篇 |
环境理论 | 26篇 |
污染及防治 | 11849篇 |
评价与监测 | 3077篇 |
社会与环境 | 2606篇 |
灾害及防治 | 274篇 |
出版年
2023年 | 218篇 |
2022年 | 505篇 |
2021年 | 493篇 |
2020年 | 363篇 |
2019年 | 423篇 |
2018年 | 752篇 |
2017年 | 795篇 |
2016年 | 1126篇 |
2015年 | 876篇 |
2014年 | 1346篇 |
2013年 | 3563篇 |
2012年 | 1607篇 |
2011年 | 2138篇 |
2010年 | 1709篇 |
2009年 | 1696篇 |
2008年 | 2059篇 |
2007年 | 2124篇 |
2006年 | 1812篇 |
2005年 | 1539篇 |
2004年 | 1445篇 |
2003年 | 1498篇 |
2002年 | 1345篇 |
2001年 | 1688篇 |
2000年 | 1195篇 |
1999年 | 711篇 |
1998年 | 480篇 |
1997年 | 529篇 |
1996年 | 521篇 |
1995年 | 610篇 |
1994年 | 628篇 |
1993年 | 488篇 |
1992年 | 524篇 |
1991年 | 493篇 |
1990年 | 539篇 |
1989年 | 479篇 |
1988年 | 410篇 |
1987年 | 396篇 |
1986年 | 350篇 |
1985年 | 376篇 |
1984年 | 380篇 |
1983年 | 371篇 |
1982年 | 349篇 |
1981年 | 319篇 |
1980年 | 274篇 |
1979年 | 292篇 |
1978年 | 262篇 |
1977年 | 214篇 |
1975年 | 210篇 |
1974年 | 192篇 |
1972年 | 203篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
M. Feldstein S. Balestrieri 《Journal of the Air & Waste Management Association (1995)》2013,63(4):177-178
The addition of a freeze-out step in liquid nitrogen prior to analysis by gas chromatography with flame ionization detection permits the accurate determination of C2 and higher hydrocarbons in the part per billion (ppb) range. Concentrations of C2 and higher hydrocarbons have been measured in commercial cylinders of nitrogen, helium and hydrogen. Using a 150 ml sample of gas, recovery of ppb concentrations is 95 to 100 percent. 相似文献
992.
M. Griggs 《Journal of the Air & Waste Management Association (1995)》2013,63(5):356-358
In recent years there has been considerable use of optical observations to determine the aerosol mass loading of the atmosphere. Nephelometer measurements of the scattering coefficient have been used for the local volume mass loading, and the turbidity of the atmosphere determined by the Volz sun photometer has been related to the vertical mass loading. This paper analyses various approaches to measuring the mass loading, and presents improved relationships between the optical observations and the aerosol mass loading. 相似文献
993.
H. C. Wohlers M. Feldstein 《Journal of the Air & Waste Management Association (1995)》2013,63(5):226-229
The problem of an investigation of the need for a regulation on organic compound emissions in the San Francisco Bay Area can be divided into two major areas: 1. Is there a need for a regulation on organic compound emissions? What is the extent of photochemical smog effects? How much control is necessary to achieve the desired effects? 2. (2) If the need exists for an organic compound regulation, can a performance type regulation be written for all types of organic compound emissions? Must the regulation be directed toward specific industries or types of emissions? Can the regulation be adequately enforced—both practically and legally? This paper will describe the studies undertaken by the District Staff to answer the first set of questions. Work covering the second group of questions is now under investigation. 相似文献
994.
995.
H. P. Sanderson R. Thomas Morris Katz 《Journal of the Air & Waste Management Association (1995)》2013,63(6):328-330
Field experience with the lead acetate impregnated paper tape sampler has indicated that large errors may arise in this method due to fading of the color of the precipitated lead sulfide spots. This fading is due to the action of light, sulfur dioxide, ozone, on other substances capable of oxidizing lead sulfide. The moisture content or relative humidity of the air sample must be maintained at an appropriate level to ensure reaction with the impregnated paper tape. The effects of the factors have been investigated in laboratory experiments with known concentrations of H2S. A number of antioxidants were studied in relation to the stability of the resultant spots to light and oxidation Orthophenyl phenol was found to be the most effective antioxidant for this purpose. A number of necessary precautions to be employed in the use of the lead acetate method are recommended and the limitations are discussed. 相似文献
996.
997.
998.
999.
1000.
John M. Pierrard 《Journal of the Air & Waste Management Association (1995)》2013,63(9):632-637
The role of particulate matter and oxides of sulfur in degradation of the atmospheric environment is discussed. The Federal Air Quality Criteria for these pollutants are analyzed for their conformance with the requirement of the Clean Air Act of 1967 that they reflect the latest scientific knowledge pertinent to the indication of their effects on health and welfare. Visibility reduction by suspended particulate matter is treated and the bases for the criteria issued in the documents “Air Quality Criteria for Particulate Matter” and “Air Quality Criteria for Sulfur Oxides” are examined. The reactions between particulate matter and gaseous pollutants are discussed, along with the Impact of particulate matter on modifications of weather processes. Local effects, such as precipitation, are considered. The relationship between pollution by particulate matter and cloud formation is discussed, as are persistence of fog and the observation that certain sources of particulate pollution are also sources of ice nuclei. 相似文献