全文获取类型
收费全文 | 13787篇 |
免费 | 143篇 |
国内免费 | 115篇 |
专业分类
安全科学 | 383篇 |
废物处理 | 360篇 |
环保管理 | 2174篇 |
综合类 | 3320篇 |
基础理论 | 3223篇 |
环境理论 | 6篇 |
污染及防治 | 3502篇 |
评价与监测 | 632篇 |
社会与环境 | 376篇 |
灾害及防治 | 69篇 |
出版年
2018年 | 126篇 |
2017年 | 131篇 |
2016年 | 196篇 |
2015年 | 159篇 |
2014年 | 205篇 |
2013年 | 1049篇 |
2012年 | 322篇 |
2011年 | 458篇 |
2010年 | 333篇 |
2009年 | 430篇 |
2008年 | 478篇 |
2007年 | 511篇 |
2006年 | 470篇 |
2005年 | 348篇 |
2004年 | 371篇 |
2003年 | 409篇 |
2002年 | 352篇 |
2001年 | 476篇 |
2000年 | 336篇 |
1999年 | 223篇 |
1998年 | 165篇 |
1997年 | 160篇 |
1996年 | 191篇 |
1995年 | 190篇 |
1994年 | 209篇 |
1993年 | 188篇 |
1992年 | 193篇 |
1991年 | 190篇 |
1990年 | 212篇 |
1989年 | 203篇 |
1988年 | 173篇 |
1987年 | 173篇 |
1986年 | 156篇 |
1985年 | 174篇 |
1984年 | 162篇 |
1983年 | 170篇 |
1982年 | 169篇 |
1981年 | 175篇 |
1980年 | 151篇 |
1979年 | 155篇 |
1978年 | 149篇 |
1977年 | 132篇 |
1976年 | 144篇 |
1975年 | 118篇 |
1974年 | 146篇 |
1973年 | 128篇 |
1972年 | 130篇 |
1971年 | 109篇 |
1970年 | 111篇 |
1967年 | 116篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
801.
802.
J.M. Kirk C.L. Woodward W.C. Ellis S.C. Ricke 《Journal of environmental science and health. Part. B》2013,48(1):103-120
Abstract The objective of this study was to determine the effects of varying nitrogen sources and concentrations upon glutamine synthetase and protease activities in Prevotella ruminicola strain B14. Based on growth response it appears that ammonium chloride or pepticase limited P. ruminicola becomes nitrogen limited when nitrogen concentration is at 0.5 mM. However, when casein was provided as the sole source of nitrogen P. ruminicola becomes nitrogen limited at 2.5 mM. Glutamine synthetase activity was measured from mid‐log phase cells grown in either nitrogen‐limited or non‐limited conditions. No activity was detectable in the non‐limited treatments. However, in the N‐ limited treatments, pepticase had the highest activity (20.76 units), followed by ammonium chloride (18.72 units) and casein (14.42 units). Protease activity assays indicated that nitrogen‐limited cultures had higher proteolytic activity than non‐limited cultures. Moreover, these activities appeared to follow the same response pattern as the previously observed glutamine synthetase activities. The results of this study indicate that P. ruminicola strain B, 4 protease activity may be influenced by nitrogen concentration such that activity increases when nitrogen availability decreases. 相似文献
803.
804.
Irritant gases in concentrations that occur in polluted atmospheres might play a role in the degranulation and histamine release processes of mast cells in lung tissue. To test this hypothesis, young rats weighing 140-150 g were exposed to 1 ppm nitrogen dioxide for 2 hr. One group was killed immediately, and another group 24-27 hr after exposure. A third group was exposed to 0.5 ppm nitrogen dioxide for 4 hr and killed immediately. Animals serving as controls were placed for 1 hr into the exposure chamber ventilated with ambient air. Standard histological preparations were made after Carnoy’s fixative and subsequent staining with toluidine blue. The mast cells of the control animals appeared relatively intact with no evidence of disorientation. The cells of the animals exposed to NO2 and sacrificed immediately revealed rupture and loss of cytoplasmic granules with some disorientation. These changes were observed in the pleura, bronchi, and surrounding tissue with the effects more marked in the mediastinum. The mast cells of exposed animals sacrificed about 24-27 hr after discontinuing the exposure showed in some cases a combination of ruptured and intact cells with a predominance of the latter, and in other cases could not be differentiated from the controls. These findings indicate that 24 hr or more are required to reverse the acute effects of NO2 inhalation. The toxicological implications will be discussed. The release of granular substances in the lung tissue when NO2 is inhaled signifies the onset of an acute inflammation. 相似文献
805.
J. L. Jones E. A. Sckuck R. W. Eldridge N. Endow F. W. Cranz 《Journal of the Air & Waste Management Association (1995)》2013,63(2):73-77
While snowflakes fell and Christmas carols heralded the imminent holiday, over 3000 delegates to the Third National Conference on Air Pollution were told to “Control Now for Clean Air.” They were told this in many ways by many people—by the Vice President of the United States; by the Secretary of the Department of Health, Education, and Welfare who summoned the Conference; and by senators, congressmen, governors, and mayors. Then eight panel sessions convened to discuss and to determine how to control now for clean air. Speakers from every section of American life addressed themselves to this subject; when they were finished, the eight session chairmen summarized what had been said, what had been, learned. These summaries appear on the following pages. 相似文献
806.
Ralph I. Larsen Ph.D. William W. Stalker Charles R. Claydon 《Journal of the Air & Waste Management Association (1995)》2013,63(11):529-534
This progress report describes the National Air Pollution Technical Information Center currently under development in the Division of Air Pollution, Public Health Service. It briefly reviews the report "Science, Government, and Information" (Weinberg Report) and the White House delegation of responsibility to the Department of Health, Education, and Welfare for handling air pollution technical information. 相似文献
807.
808.
809.
810.
W. L. Faith 《Journal of the Air & Waste Management Association (1995)》2013,63(11):459-460
Commercial cattle-feeding is a large industry in the United States. In California, for instance, there are more than 500 commercial feedlots. Each of these lots handles from less than 500 to more than 50,000 head of cattle at one time. With the urban and suburban explosion, feedlots that were at one time many miles from residential centers are now “just across the street.” Naturally the high odor level from improperly operated yards gives rise to considerable complaint and citizen indignation. A variety of methods to reduce odor to an acceptable level have been tried with varying results. A highly satisfactory procedure is based on “good housekeeping” practices, frequent removal of fecal material, and abatement of residual odor by spraying the lots at designated intervals with a solution of potassium permanganate. Details of the method are discussed. 相似文献