全文获取类型
收费全文 | 725篇 |
免费 | 9篇 |
国内免费 | 6篇 |
专业分类
安全科学 | 33篇 |
废物处理 | 20篇 |
环保管理 | 173篇 |
综合类 | 66篇 |
基础理论 | 214篇 |
环境理论 | 1篇 |
污染及防治 | 113篇 |
评价与监测 | 60篇 |
社会与环境 | 48篇 |
灾害及防治 | 12篇 |
出版年
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 7篇 |
2019年 | 8篇 |
2018年 | 19篇 |
2017年 | 13篇 |
2016年 | 24篇 |
2015年 | 12篇 |
2014年 | 18篇 |
2013年 | 37篇 |
2012年 | 24篇 |
2011年 | 44篇 |
2010年 | 23篇 |
2009年 | 37篇 |
2008年 | 35篇 |
2007年 | 32篇 |
2006年 | 31篇 |
2005年 | 27篇 |
2004年 | 20篇 |
2003年 | 21篇 |
2002年 | 28篇 |
2001年 | 17篇 |
2000年 | 23篇 |
1999年 | 14篇 |
1998年 | 13篇 |
1997年 | 9篇 |
1996年 | 14篇 |
1995年 | 18篇 |
1994年 | 16篇 |
1993年 | 13篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 10篇 |
1989年 | 6篇 |
1988年 | 11篇 |
1987年 | 7篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 14篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 8篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1972年 | 4篇 |
1968年 | 2篇 |
1967年 | 2篇 |
排序方式: 共有740条查询结果,搜索用时 958 毫秒
471.
472.
Livestock Grazing and Conservation on Southwestern Rangelands 总被引:3,自引:0,他引:3
473.
In order to examine the effects of artificial diets at the tissue level, plaice (Pleuronectes platessa L.) were fed either high (50%) or low (20%) protein diets for several weeks and the total quantities of deoxyribonucleic acid (DNA), ribonucleic acid (RNA), protein and phospholipid in their livers were measured. Alanine amino-transferase, aspartate aminotransferase, glutamate dehydrogenase and glucose-6-phosphatase activities in the livers were also measured. Similar measurements were made on the livers of wild plaice. The total amount of DNA in the livers of both cultured and wild plaice, of standard weight, did not differ significantly, irrespective of dietary history. In fish of standard weight, total hepatic RNA, protein and phospholipid levels were highest in the cultured fish fed high protein diet and lowest in the wild fish. These differences were related to dietary protein supply and environmental temperature. The total organ levels of the liver enzymes in plaice of equal weight were not significantly different in the cultured fish fed high and low protein diets. Wild-fish livers contained a smaller total amount of alanine aminotransferase, aspartate aminotransferase and glucose-6-phosphatase activity than did those of cultured fish. Total liver glutamate dehydrogenase activity was not significantly different in any of the fish examined. It is suggested that kinetic and allosteric factors may be more important in controlling protein metabolism and amino acid cat abolism in fish than total enzyme level. 相似文献
474.
Leonard R. Brown 《Journal of the American Water Resources Association》1972,8(2):401-403
The author cites many discrepancies in using river basins as a framework for water resources planning, development, and management. He suggests that a national planning framework, an urban region framework, or increased attention to regional externalities might be viable. However, basically the author is seeking to elicit suggestions and recommendations from the readers. 相似文献
475.
Previous studies relating forest presence to stream acidity and aluminium concentration were based on small numbers of catchments, often precluding the elimination of confounding influences on stream chemistry, such as geology or soil type. Spatial patterns in aluminium and pH data from 113 Welsh catchments of contrasting land use were therefore analysed in three different ranges of acid sensitivity (< 10, 10-15, 15-25 mg CaCO(3) litre(-1) total hardness). In each range, pH declined and aluminium increased significantly with increasing percentage forest cover. There was no evidence that the relationships reflected a spurious effect of forest location. Where aluminium concentrations were elevated under forest in a sub-set of 13 streams, aluminium was present predominantly in the labile form, most toxic to fish. Regressions of pH and aluminium on percentage forest cover provide a useful method of assessing the amount of forest in Welsh catchments which might give rise to given chemical conditions (e.g. pH <6, Al > 80 microg litre(-1)), though some difficulties are likely in accurately specifying the conditions desirable for fish or other biota. 相似文献
476.
477.
James T. Brown Jr. 《Environment international》1981,6(1-6)
An experimental study has been undertaken at the Colorado School of Mines to evaluate the feasibility of using condensational enlargement to enhance the collection efficiency of existing dust control technologies for sub-micron particulates. Although the study was begun to consider the problem of respirable dust control in the underground coal mine environment, this enhancement technique shows promise for a more general class of applications. In the experiments to be reported on, particulates are injected into a continuous flow thermal diffusion chamber and subjected to varying environmental conditions; saturation ratio (rel. humidity), temperature, and residence time were the parameters. The results show that condensation on a dust nucleus (≈0.1 micron) can bring it to a size of several microns in a sufficiently short period of time as to indicate engineering applicability of the concept. 相似文献
478.
479.
480.