全文获取类型
收费全文 | 232篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
安全科学 | 1篇 |
废物处理 | 10篇 |
环保管理 | 7篇 |
综合类 | 111篇 |
基础理论 | 47篇 |
污染及防治 | 33篇 |
评价与监测 | 9篇 |
社会与环境 | 15篇 |
出版年
2021年 | 2篇 |
2018年 | 3篇 |
2016年 | 4篇 |
2015年 | 3篇 |
2013年 | 5篇 |
2012年 | 4篇 |
2011年 | 11篇 |
2010年 | 2篇 |
2009年 | 9篇 |
2008年 | 5篇 |
2007年 | 10篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 4篇 |
2003年 | 2篇 |
2002年 | 6篇 |
2001年 | 2篇 |
1999年 | 7篇 |
1998年 | 2篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1975年 | 3篇 |
1970年 | 2篇 |
1966年 | 8篇 |
1965年 | 4篇 |
1964年 | 11篇 |
1963年 | 7篇 |
1962年 | 5篇 |
1961年 | 9篇 |
1959年 | 3篇 |
1958年 | 2篇 |
1957年 | 2篇 |
1956年 | 3篇 |
1955年 | 4篇 |
1954年 | 7篇 |
1940年 | 1篇 |
1939年 | 2篇 |
1935年 | 1篇 |
1934年 | 1篇 |
1932年 | 1篇 |
1930年 | 2篇 |
排序方式: 共有233条查询结果,搜索用时 754 毫秒
211.
212.
213.
214.
215.
216.
Daniele Torriani Pierluigi Calanca Markus Lips Helmut Ammann Martin Beniston Jürg Fuhrer 《Regional Environmental Change》2007,7(4):209-221
A simple model of yield was used along with climate scenarios to assess the impact of climate change on grain maize productivity
and associated economic risk in Switzerland. In a first application, changes in the precipitation regime alone were shown
to affect the distribution of yield considerably, with shifts not only in the mean but also in the standard deviation and
the skewness. Production risk was found to respond more markedly to changes in the long-term mean than in the inter-annual
variability of seasonal precipitation amounts. In a further application, yield projections were generated with respect to
a full climate scenario, with the emission pathway as specified in the IPCC A2 scenario. Anticipation of the sowing date was
found to reduce the negative impact of climate change on yield stability, but was not sufficient to ensure average productivity
levels comparable to those observed at present. We argued that this was caused by the reduction in the duration of the growing
season, which had a stronger impact than suggested by previous studies. Assuming no change in price relations, the results
also revealed a strong increase in production risk with climate change, with more than a doubling in the probability of yield
falling short of a critical threshold as compared to today’s situation. 相似文献
217.
218.
219.
/ Since 1975, the European Union (EU) has developed an impressive body of waste management legislation, although, according to the principle of subsidiarity, responsibilities belong to the most local level at which the tasks can be carried out effectively. Using economic theory, this paper examines several factors that influence the efficient distribution of regulatory authority among the EU and the member states. We specifically analyze the role of harmonization that, in our opinion, will often lead to an overcentralization. Within this context, a second issue is becoming more important, as ongoing discussions show. If no consensus can be reached about harmonization, should member states be allowed to stop cross-border shipments of waste, or should the EU strive for a common market for waste? We take the position that most objections against waste shipments are not convincing, especially if the member states implement minimum standards for landfills and waste processing facilities and common information and control systems. Competition between different national regulations within adequate constraints that, e.g., control transboundary externalities leads to more efficient waste management structures in Europe than national self-sufficiency or centralized decision-making at the EU level. KEY WORDS: Waste management; European Union; Subsidiarity; Institutional competition; Harmonization; Cross-border shipments of waste 相似文献
220.
Grazing regulates the spatial variability of periphyton biomass 总被引:2,自引:0,他引:2
Hillebrand H 《Ecology》2008,89(1):165-173
The presence of consumers not only alters the mean biomass of the prey assemblage, but also affects the spatial heterogeneity of biomass distribution. Whereas the mean prey biomass is generally reduced by consumer presence, the effect on spatial heterogeneity is less clear-cut. A meta-analysis of almost 600 field experiments manipulating the presence of benthic invertebrate or vertebrate grazers was conducted to analyze the effect of grazers on both the absolute spatial variability of periphyton biomass and the relative variability, which was standardized to the mean. Effects on absolute variability were measured as the log response ratio of the standard deviation of biomass (LR-SD), whereas effects on relative variability were measured as the log response ratio of the coefficient of variation of biomass (LR-CV). The overall magnitude and range of LR-SD and LR-CV indicated that grazers not only reduced periphyton biomass, but also substantially altered their spatial distribution. However, grazer effects differed strongly for absolute and relative variability. On average, grazers reduced the absolute spatial variability in prey biomass by 50% (average LR-SD = -0.68) but increased the relative variability by 24% (average LR-CV = 0.22). The magnitude of LR-SD strongly depended on the efficiency of grazing, with strong biomass removal leading to strong homogenization. Moreover, LR-CV and LR-SD were significantly affected by habitat type (freshwater vs. coastal) and substrata. Given the importance of spatial heterogeneity for resource uptake, competition and the maintenance of diversity, grazer presence has potentially strong indirect effects on the interactions within prey assemblages. 相似文献