全文获取类型
收费全文 | 40717篇 |
免费 | 442篇 |
国内免费 | 323篇 |
专业分类
安全科学 | 1168篇 |
废物处理 | 1469篇 |
环保管理 | 5655篇 |
综合类 | 6496篇 |
基础理论 | 11531篇 |
环境理论 | 24篇 |
污染及防治 | 10556篇 |
评价与监测 | 2448篇 |
社会与环境 | 1864篇 |
灾害及防治 | 271篇 |
出版年
2022年 | 260篇 |
2021年 | 276篇 |
2019年 | 323篇 |
2018年 | 555篇 |
2017年 | 548篇 |
2016年 | 814篇 |
2015年 | 662篇 |
2014年 | 937篇 |
2013年 | 3065篇 |
2012年 | 1154篇 |
2011年 | 1691篇 |
2010年 | 1402篇 |
2009年 | 1399篇 |
2008年 | 1711篇 |
2007年 | 1793篇 |
2006年 | 1640篇 |
2005年 | 1345篇 |
2004年 | 1348篇 |
2003年 | 1279篇 |
2002年 | 1246篇 |
2001年 | 1653篇 |
2000年 | 1147篇 |
1999年 | 731篇 |
1998年 | 588篇 |
1997年 | 577篇 |
1996年 | 583篇 |
1995年 | 652篇 |
1994年 | 623篇 |
1993年 | 532篇 |
1992年 | 560篇 |
1991年 | 527篇 |
1990年 | 541篇 |
1989年 | 571篇 |
1988年 | 477篇 |
1987年 | 422篇 |
1986年 | 384篇 |
1985年 | 419篇 |
1984年 | 425篇 |
1983年 | 457篇 |
1982年 | 451篇 |
1981年 | 401篇 |
1980年 | 342篇 |
1979年 | 375篇 |
1978年 | 320篇 |
1977年 | 272篇 |
1976年 | 258篇 |
1975年 | 267篇 |
1974年 | 256篇 |
1973年 | 244篇 |
1972年 | 292篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
441.
Berdicevsky I Duek L Merzbach D Yannai S 《Environmental pollution (Barking, Essex : 1987)》1993,80(1):41-44
The purpose of the study reported here was to investigate the relative resistance of yeast species to various metallic and metalloid ions, with a view to gaining more knowledge on this subject, as resistant species may become dominant in habitats contaminated with the relevant metals. Saccharomyces cerevisiae, Candida albicans and Candida tropicalis were grown in media containing different concentrations of mercury (as HgCl(2)), cadmium (as CdCl(2)), lead (as Pb(CH(3)COO)(2)), arsenic (as Na(2)HAsO(4)) and selenium (as Na(2)SeO(3)) for various intervals. Invariably, the two Candida species turned out to be more resistant to all the metals studied than S. cerevisiae. The metal showing the highest toxicity for these species was mercury, with cadmium being the second, lead, the third and arsenic and selenium being the least toxic elements. Strains showing resistance to mercury were isolated, even in the case of S. cerevisiae. 相似文献
442.
Summary We hypothesise that foraging group size (FGS) and population group size (PGS) in primates and carnivores are related to quantifiable variables indexing the intensity of exploitative competition. Group size is predicted to increase with both food density and travel capabilities, as estimated by the constraint-free day-range (DRs), i.e. the day-range of a solitary individual uninfluenced by competition from conspecifics. We test this exploitation competition hypothesis among primates and carnivores, using data on populations, species and genera. Food density was indexed by population density. Where DRs could be estimated by regression it was found to be correlated with observed day-range (DRm). DRs was therefore indexed by DRm in all species. Population density and DRm were associated with each other, but in a multiple regression each variable contributed independently to explaining variation in group size. PGS was predicted better than FGS, but regressions involving either measure of group size were significant in all analyses. The multiple regression analyses were validated by the method of linear contrasts, which accounts for possible lack of independence among taxa. We conclude that species differences in group size are influenced by both food density and DRs. This suggests that variation in the intensity of exploitation competition is partly responsible for differences in group size.Correspondence to: R.W. Wrangham 相似文献
443.
The proximate and elemental chemical compositions of 25 species of pelagic decapod and mysid crustaceans collected from the eastern Gulf of Mexico (27°N; 86°W, 1984 to 1989) was examined. Water level ranged from 63 to 95% and increased slightly with species' increased depth of occurrence. Protein levels were generally high (1.5 to 18.3% wet wt, WW; 27.6 to 62.4% ash-free dry wt, AFDW) and comprised the primary organic component in the majority of species. Protein, both as % WW and % AFDW, decreased with increased depth of occurrence. In contrast to protein, lipid levels were low (0.5 to 8.9% WW; 5.7 to 60.9% AFDW), and increased with increased depth of occurrence. Carbon and nitrogen best mirrored measured lipid and protein levels when considered as non-protein carbon and non-chitin nitrogen, respectively. C:N ratios increased with increased depth, consistent with changes in protein and lipid with depth. Because of their compositional attributes, resident Gulf of Mexico species have a low total wet weight energy content relative to species from more productive regions. Energy content showed no significant trend with depth. Vertical migration patterns were distinctly different between shallow-and deep-living gulf species and these differences were largely responsible for the relationships observed between composition and depth. In migrating species, the protein and nitrogen content were higher, the lipid and carbon contents and C:N ratio lower, than in non-migrating species. Three deep-living species of the genus Acanthephyra were found to be compositionally atypical, resembling shallow, migrating types rather than other deep-living, non-migratory species. 相似文献
444.
445.
Community response to hazard information 总被引:1,自引:0,他引:1
McKay JM 《Disasters》1984,8(2):118-123
The impact of flood hazard information on public acceptance of a selected flood mitigation strategy was assessed by an analysis of the content of newspaper reports of community reaction and letters to the editor. The impact of personal delivery of a flood hazard map on individual perception of risk and attitude to such information was assessed using personal interviews. The results indicated that media coverage of the flood hazard information reduced public criticism of the works. This result must be partially attributable to the dramatic style of media coverage and the fact that the media only emphasized the positive value of the works. The interview demonstrated that personal delivery of the information raised perception of risk, improved comprehension of flood risk, had no impact on acceptability of risk but discouraged some respondents from seeking such information in the future. Factors to explain the last negative change were identified to be the format of the map sheet and low salience of flood hazard. On the basis of all results, methods to improve community response to hazard information are provided. 相似文献
446.
447.
The population dynamics of Mytilicola intestinalis Steuer in mussels (Mytilus edulis L.) from the River Lynher, Cornwall, England, have been studied over 3 years. By transplanting uninfested mussels from the River Erme, South Devon, into the Lynher mussel bed, the study was extended to the growth and development of new infestations under natural conditions. Female Mytilicola intestinalis are shown to breed twice, and two generations of parasites coexist for most of the year, with recruitment taking place in summer and autumn. One generation contributes its first brood to the autumn recruits before overwintering and contributing its second brood to the following summer's recruits. The other generation overwinters as juvenile and immature stages to contribute its two broods successively to the summer and autumn recruits. Environmental temperatures are believed to control the rates of development at all stages rather than acting as triggers in the onset or cessation of breeding at specific times. There is no evidence to support the contention that heavily infested mussels are killed, and parasite mortality is shown to be density-independent. 相似文献
448.
Duffy JC 《Disasters》1978,2(2-3):159-162
449.
450.