全文获取类型
收费全文 | 537篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
安全科学 | 7篇 |
废物处理 | 18篇 |
环保管理 | 48篇 |
综合类 | 214篇 |
基础理论 | 96篇 |
环境理论 | 1篇 |
污染及防治 | 124篇 |
评价与监测 | 17篇 |
社会与环境 | 17篇 |
灾害及防治 | 1篇 |
出版年
2022年 | 5篇 |
2021年 | 8篇 |
2020年 | 8篇 |
2018年 | 7篇 |
2017年 | 16篇 |
2016年 | 9篇 |
2015年 | 7篇 |
2014年 | 12篇 |
2013年 | 23篇 |
2012年 | 21篇 |
2011年 | 25篇 |
2010年 | 14篇 |
2009年 | 17篇 |
2008年 | 28篇 |
2007年 | 19篇 |
2006年 | 18篇 |
2005年 | 18篇 |
2004年 | 14篇 |
2003年 | 4篇 |
2002年 | 12篇 |
2001年 | 9篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 8篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1993年 | 5篇 |
1990年 | 4篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1977年 | 4篇 |
1973年 | 6篇 |
1972年 | 6篇 |
1971年 | 5篇 |
1970年 | 4篇 |
1967年 | 6篇 |
1966年 | 4篇 |
1965年 | 5篇 |
1963年 | 6篇 |
1961年 | 4篇 |
1960年 | 6篇 |
1959年 | 8篇 |
1958年 | 5篇 |
1957年 | 5篇 |
1956年 | 9篇 |
1955年 | 10篇 |
1938年 | 4篇 |
1934年 | 4篇 |
1924年 | 3篇 |
1913年 | 3篇 |
排序方式: 共有543条查询结果,搜索用时 437 毫秒
111.
112.
Ecologists use stable isotopes (delta13C, delta15N) to better understand food webs and explore trophic interactions in ecosystems. Traditionally, delta13C vs. delta15N bi-plots have been used to describe food web structure for a single time period or ecosystem. Comparisons of food webs across time and space are increasing, but development of statistical approaches for testing hypotheses regarding food web change has lagged behind. Here we present statistical methodologies for quantitatively comparing stable isotope food web data. We demonstrate the utility of circular statistics and hypothesis tests for quantifying directional food web differences using two case studies: an arthropod salt marsh community across a habitat gradient and a freshwater fish community from Lake Tahoe, USA, over a 120-year time period. We calculated magnitude and mean angle of change (theta) for each species in food web space using mean delta13C and delta15N of each species as the x, y coordinates. In the coastal salt marsh, arthropod consumers exhibited a significant shift toward dependence on Spartina, progressing from a habitat invaded by Phragmites to a restored Spartina habitat. In Lake Tahoe, we found that all species from the freshwater fish community shifted in the same direction in food web space toward more pelagic-based production with the introduction of nonnative Mysis relicta and onset of cultural eutrophication. Using circular statistics to quantitatively analyze stable isotope food web data, we were able to gain significant insight into patterns and changes in food web structure that were not evident from qualitative comparisons. As more ecologists incorporate a food web perspective into ecosystem analysis, these statistical tools can provide a basis for quantifying directional food web differences from standard isotope data. 相似文献
113.
Schröder W Hornsmann I Pesch R Schmidt G Markert B Fränzle S Wünschmann S Heidenreich H 《Environmental monitoring and assessment》2007,133(1-3):495-505
The study was conducted to test the hypothesis that the regional variability of nitrogen (N) and metal accumulations in terrestrial ecosystems are due to historical and recent ways of landuse. To this end, two regions of Central Europe were selected for investigation: the Weser-Ems Region (WER) and the Euro Region Nissa (ERN). They were assumed to have land use-specific accumulation profiles. Thus, the metal and N accumulations in both regions were examined by means of geostatistically based comparative moss analysis. The sampling and chemical analysis of mosses were conducted in accordance with the convenient guidelines and methods, respectively. The spatial representativity of the sampling sites was computed by means of a land classification which was calculated for Europe by means of classification trees and GIS-techniques. The differences of deposition loads were tested for statistical significance with regard to time and space. The measurement values corroborated the decline of metal accumulation observed since the beginning of the European Metals in Mosses Surveys in 1990. The metal loads of the mosses in the ERN exceeded those in the WER significantly. The opposite holds true for the N concentrations: those in the WER were significantly higher than those in the ERN. The reduction of emissions from power plants, factories and houses was strongly correlated with the decline of deposition and bioaccumulation of metals. As proved by the European Metals in Mosses Surveys, this tendency is due to successful environmental policies. But no such success could be verified by monitoring the accumulation of N in mosses. 相似文献
114.
Rainer Haas Alfred Krippendorf Torsten C. Schmidt Klaus Steinbach Eberhard v. Löw 《Environmental Sciences Europe》1998,10(5):289-293
Arsenic containing chemical warfare agents (cwa) are persistent in the environment and continue to contaminte soil and ground water. In this paper the chemical rections of the cwa diphenylarsine chloride (CLARK I), phenylarsine dichloride (PFIFFIKUS), ethylarsine dichloride (DICK) and of chlorovinyl arsenic compounds (LEWISITE) are shown. The posibilities of the detection and determination of this cwa and their metabolites are presented. 相似文献
115.
116.
117.
R. W. Pohl E. Schmidt G. C. Hirsch H. Marquardt O. Harnisch 《Die Naturwissenschaften》1959,46(11):387-388
118.
119.
120.