全文获取类型
收费全文 | 21469篇 |
免费 | 227篇 |
国内免费 | 184篇 |
专业分类
安全科学 | 599篇 |
废物处理 | 870篇 |
环保管理 | 3071篇 |
综合类 | 5680篇 |
基础理论 | 4522篇 |
环境理论 | 7篇 |
污染及防治 | 5080篇 |
评价与监测 | 1174篇 |
社会与环境 | 769篇 |
灾害及防治 | 108篇 |
出版年
2019年 | 150篇 |
2018年 | 259篇 |
2017年 | 268篇 |
2016年 | 386篇 |
2015年 | 317篇 |
2014年 | 416篇 |
2013年 | 1632篇 |
2012年 | 531篇 |
2011年 | 743篇 |
2010年 | 664篇 |
2009年 | 730篇 |
2008年 | 797篇 |
2007年 | 830篇 |
2006年 | 726篇 |
2005年 | 604篇 |
2004年 | 667篇 |
2003年 | 621篇 |
2002年 | 589篇 |
2001年 | 687篇 |
2000年 | 503篇 |
1999年 | 369篇 |
1998年 | 267篇 |
1997年 | 251篇 |
1996年 | 259篇 |
1995年 | 294篇 |
1994年 | 298篇 |
1993年 | 268篇 |
1992年 | 290篇 |
1991年 | 271篇 |
1990年 | 299篇 |
1989年 | 268篇 |
1988年 | 207篇 |
1987年 | 212篇 |
1986年 | 223篇 |
1985年 | 217篇 |
1984年 | 242篇 |
1983年 | 230篇 |
1982年 | 230篇 |
1981年 | 252篇 |
1980年 | 209篇 |
1979年 | 199篇 |
1978年 | 169篇 |
1977年 | 153篇 |
1974年 | 153篇 |
1973年 | 155篇 |
1968年 | 157篇 |
1967年 | 188篇 |
1966年 | 155篇 |
1965年 | 148篇 |
1964年 | 151篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Monte Carlo-assisted factor analysis has been applied to a data set of 20 trace-element concentrations in tree-bark samples obtained from 123 locations in The Netherlands, with the aim to investigate the suitability of bark as a biomonitor for air pollution. A Monte Carlo approach was used to give more insight to the uncertainties and significance levels of the factor analysis results. Notwith-standing a rather strong influence of soil material on the concentration levels, factor analysis enabled the identification of five significant pollution source types, all of which corresponded with source types found in an earlier biomonitoring study in The Netherlands using epiphytic lichens. A more detailed comparison with the lichen results showed a remarkable difference in lead concentrations between bark and lichen. It was concluded that bark can be successfully employed as a biomonitor for air pollution. The power of factor analysis to adequately determine the soil contribution may render extensive sample washing procedures superfluous. 相似文献
22.
Robert H. Gray 《Environmental monitoring and assessment》1993,26(2-3):263-276
Environmental monitoring has been an ongoing activity on the U.S. Department of Energy's Hanford Site in southeastern Washington for almost 50 years. Objectives are to detect and assess potential impacts of Site operations on air, surface and ground waters, foodstuffs, fish, wildlife, soil and vegetation. Data from monitoring effects are used to calculate the overall radiological dose to humans working onsite or residing in nearby communities. In 1989, measured Hanford Site perimeter concentrations of airborne radionuclides were below applicable guidelines. Concentrations of radionuclides and nonradiological water quality in the Columbia River were in compliance with applicable standards. Foodstuffs irrigated with river water taken downstream of the Site showed radionuclide levels that were similar to those found in foodstuffs from control areas. Low levels of 137Cs and 90Sr in most onsite wildlife samples and concentrations of radionuclides in soils and vegetation from on- and offsite locations were typical of those attributable to worldwide fallout. The calculated dose potentially received by a maximally exposed individual (i.e., based on hypothetical, worst-case assumptions for all routes of exposure) in 1989 (0.05 mrem/yr) was similar to those calculated for 1985 through 1988.In addition to monitoring radioactivity in fish and wildlife, population numbers of key species are determined. Chinook salmon (Oncorhynchus tshawytscha) spawning in the Columbia River at Hanford has increased in recent years with a concomitant increase in winter roosting activity of bald eagles (Haliaeetus leucocephalus). An elk (Cervus elaphus) herd, established by immigration in 1972, is also increasing. The Hanford Site currently serves as a refuge for Canada goose (Branta canadensis), great blue heron (Ardea herodias), and various plants and other animals, e.g., mule deer (Odocoileus hemionus), and coyotes (Canis latrans). 相似文献
23.
The Science of Nature - 相似文献
24.
25.
The Science of Nature - 相似文献
26.
27.
J. Heinze H. Remmert F. L. Boschke D. Reinen L. Jaenicke 《Die Naturwissenschaften》1983,70(11):575-576
28.
Pheromones — semiochemicals used by insects for intraspecific chemical communication — can be isolated and with special analytical techniques their chemical structure elucidated. With stereoselective synthesis methods, presented by the preparation of sex attractants and aggregating pheromones of moths and beetles, respectively, a synthetic access to compounds is given which can be used for behavior manipulation of insects. Aside the importance of these compounds for investigations of the sensoric process the possibility of their application in an integrated and biological pest control is discussed. 相似文献
29.
30.
Plasticity of honeybee castes 总被引:1,自引:0,他引:1