全文获取类型
收费全文 | 2210篇 |
免费 | 18篇 |
国内免费 | 27篇 |
专业分类
安全科学 | 62篇 |
废物处理 | 70篇 |
环保管理 | 276篇 |
综合类 | 485篇 |
基础理论 | 454篇 |
环境理论 | 1篇 |
污染及防治 | 659篇 |
评价与监测 | 113篇 |
社会与环境 | 120篇 |
灾害及防治 | 15篇 |
出版年
2023年 | 22篇 |
2022年 | 19篇 |
2021年 | 31篇 |
2020年 | 24篇 |
2019年 | 31篇 |
2018年 | 54篇 |
2017年 | 57篇 |
2016年 | 67篇 |
2015年 | 75篇 |
2014年 | 84篇 |
2013年 | 108篇 |
2012年 | 90篇 |
2011年 | 144篇 |
2010年 | 121篇 |
2009年 | 137篇 |
2008年 | 124篇 |
2007年 | 129篇 |
2006年 | 94篇 |
2005年 | 68篇 |
2004年 | 93篇 |
2003年 | 59篇 |
2002年 | 79篇 |
2001年 | 71篇 |
2000年 | 41篇 |
1999年 | 20篇 |
1998年 | 23篇 |
1997年 | 29篇 |
1996年 | 23篇 |
1995年 | 33篇 |
1994年 | 26篇 |
1993年 | 9篇 |
1992年 | 20篇 |
1991年 | 27篇 |
1990年 | 14篇 |
1989年 | 20篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1982年 | 13篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 11篇 |
1970年 | 10篇 |
1967年 | 5篇 |
1966年 | 5篇 |
1965年 | 8篇 |
1964年 | 5篇 |
1960年 | 6篇 |
1956年 | 5篇 |
排序方式: 共有2255条查询结果,搜索用时 203 毫秒
781.
This paper analyses the extent to which the new Reagan mineral policy will encourage increased US production, substitution, recycling and conservation, domestic stock-piling and diversification of foreign supplies. Major inadequacies of the mineral policy are the transfer of responsibility for research and development from the government to the unprepared private sector, the lack of emphasis on short-term research and development in mineral processing technology, and the lack of coordination between minerals policy and national security and foreign policy. However, overall the policy is a positive step towards reducing the current US minerals supply vulnerability. 相似文献
782.
The factors which influence the size and value of mineral reserves are discussed and an example is given of a more rigorous system for measuring supplies of non-renewable resources.The extent to which reserves and resources of minerals can be used as leading indicators of future mineral production is examined and examples of the dangers of over-reliance on this factor are described.Key aspects, such as confidence limits, differences in the economic exploitability, the dynamic nature of reserves, and their variability in grade, are examined in some detail using the South African coal industry as an example. 相似文献
783.
784.
Wemcol is a technical isopropylbiphenyl formulation that is used as a substitute for polychlorobiphenyl. According to the producer Wemcol is 4-isopropylbiphenyl, but we found our sample to consist of 60.3% 3-isopropylbiphenyl, 38.6% 4-isopropylbiphenyl and 3,5-, 3,3′-, 3,4′- and 4,4′-diisopropylbiphenyl in amounts of 0.3%, 0.4%, 0.2% and 0.1% respectively. The two major components of the mixture are metabolized in the rat by two routes : oxidation of the isopropyl group and hydroxylation of the aromatic nuclei. Rats fed the technical mixture retained 3- and 4-isopropylbiphenyl in a ratio 4.3 : 1 in their abdominal fat, whilst the ratio in the mixture is 1.6 : 1. One week after the simultaneous feeding of equal amounts of Wemcol, 4,4′-dichlorobiphenyl, 2,4′,5-trichlorobiphenyl and 2,2′,5,5′-tetrachlorobiphenyl, the isopropylbiphenyls, in contrast to the chlorobiphenyls, could no longer be detected in the abdominal fat of rats. 相似文献
785.
786.
787.
788.
789.
790.
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