全文获取类型
收费全文 | 437篇 |
免费 | 0篇 |
国内免费 | 2篇 |
专业分类
安全科学 | 1篇 |
废物处理 | 6篇 |
环保管理 | 34篇 |
综合类 | 196篇 |
基础理论 | 77篇 |
污染及防治 | 101篇 |
评价与监测 | 18篇 |
社会与环境 | 5篇 |
灾害及防治 | 1篇 |
出版年
2018年 | 7篇 |
2016年 | 5篇 |
2014年 | 4篇 |
2013年 | 17篇 |
2012年 | 7篇 |
2011年 | 13篇 |
2010年 | 8篇 |
2009年 | 14篇 |
2008年 | 9篇 |
2007年 | 14篇 |
2006年 | 20篇 |
2005年 | 25篇 |
2004年 | 5篇 |
2003年 | 11篇 |
2002年 | 6篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 9篇 |
1995年 | 8篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1981年 | 4篇 |
1969年 | 4篇 |
1967年 | 5篇 |
1966年 | 5篇 |
1965年 | 4篇 |
1964年 | 4篇 |
1962年 | 4篇 |
1961年 | 8篇 |
1960年 | 9篇 |
1959年 | 6篇 |
1958年 | 7篇 |
1957年 | 8篇 |
1956年 | 13篇 |
1955年 | 8篇 |
1954年 | 6篇 |
1953年 | 8篇 |
1952年 | 3篇 |
1951年 | 4篇 |
1947年 | 3篇 |
1941年 | 5篇 |
1939年 | 4篇 |
1921年 | 3篇 |
排序方式: 共有439条查询结果,搜索用时 15 毫秒
11.
12.
13.
We use hydra as a model system to understand how growth and differentiation and, as a consequence of this, pattern formation are controlled at the molecular level. We have found that four substances control head and foot formation in hydra: an activator and an inhibitor of head formation and an activator and an inhibitor of foot formation. The two activators are peptides with molecular weights around 1000 daltons, the inhibitors are smaller in molecular weight (<500), have an overall positive charge and do not contain peptide bonds. In normal animals all four substances are present and most likely produced by nerve cells. We hope to understand how these substances act and interact to create the spatial and temporal pattern of growth and differentiation typical for hydra. 相似文献
14.
Helmut Haberl Christoph Plutzar Karl-Heinz Erb Veronika Gaube Martin Pollheimer Niels B. Schulz 《Agriculture, ecosystems & environment》2005,110(3-4):119-131
The relationship between land-use induced changes in production ecology and avifauna diversity was analysed using a GIS land cover dataset on a 0.25 km × 0.25 km grid covering Austria's national territory. Considering only aboveground processes, the “human appropriation of net primary production” (HANPP = potential NPP − NPPt), actual NPP (NPPact), harvest (NPPh) and NPPt (= NPPact − harvest) were recalculated based on existing datasets. Elevation as well as indicators of land cover heterogeneity and landscape heterogeneity were also considered. Correlation analyses were performed between these potential determinants of avifauna diversity and breeding bird species richness data as well as the percentage of endangered breeding birds included in the Austrian red list. Four spatial scales—0.25 km × 0.25 km, 1 km × 1 km, 4 km × 4 km and 16 × 16 km, were analysed. It was shown that breeding bird species richness was more strongly correlated with production ecological indicators and elevation than with heterogeneity indicators. A residual analysis in which the effect of elevation (a proxy for climate) on species richness and its potential determinants was removed confirmed the importance of the availability of trophic energy (NPP) for bird diversity patterns. The results support the species-energy hypothesis, thus confirming the notion that HANPP could be a useful pressure indicator for biodiversity loss. 相似文献
15.
16.
17.
18.
Forty pairs of mallards (Anas platyrhynchos) were fed 15 ppm selenium as selenomethionine for about 21 weeks during winter. Twenty pairs served as controls. At the end of 21 weeks, which coincided with the onset of the reproductive season, selenium treatment was ended. Four birds died while on selenium treatment. Treated females lost weight, and their egg-laying was delayed. Hatching success of some of the first eggs laid by selenium-treated females was lower than that of controls, and a few of these early eggs contained deformed embryos, but, after a period of about two weeks off the selenium-treated diet, reproductive success returned to a level comparable with that of controls. The return to normal reproductive success was the result of a corresponding decrease in selenium concentrations in eggs once selenium treatment ended. 相似文献
19.
Christopher R. Ellis Jerry Champlin Heinz G. Stefan 《Journal of the American Water Resources Association》1997,33(6):1363-1374
ABSTRACT: Evidence is presented that snowmelt runoff from an urban watershed can produce density current intrusions (underflows) in a lake. Several episodes of density current intrusions are documented. Water temperatures and salinities measured near the bottom of a 10 m deep Minneapolis lake during the late winter warming periods in 1989, 1990, 1991, and 1995 show significant rapid changes which are correlated with observed higher air temperatures and snowmelt runoff. The snowmelt runoff entering this particular lake (Ryan Lake) has increased electrical conductivity, salinity, and density. The source of the salinity is the salt spread on urban streets in the winter. Heating of littoral waters in spring may also contribute to the occurrence of the sinking flows, but is clearly not the only cause. 相似文献
20.