首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   197篇
  免费   1篇
  国内免费   1篇
安全科学   2篇
废物处理   10篇
环保管理   17篇
综合类   36篇
基础理论   63篇
污染及防治   52篇
评价与监测   5篇
社会与环境   11篇
灾害及防治   3篇
  2023年   2篇
  2022年   4篇
  2021年   5篇
  2019年   2篇
  2018年   1篇
  2017年   9篇
  2016年   8篇
  2015年   7篇
  2014年   6篇
  2013年   12篇
  2012年   12篇
  2011年   8篇
  2010年   5篇
  2009年   12篇
  2008年   17篇
  2007年   13篇
  2006年   7篇
  2005年   10篇
  2004年   7篇
  2003年   10篇
  2002年   10篇
  2001年   3篇
  2000年   5篇
  1999年   2篇
  1998年   4篇
  1997年   5篇
  1996年   1篇
  1995年   1篇
  1994年   4篇
  1992年   3篇
  1989年   2篇
  1976年   1篇
  1962年   1篇
排序方式: 共有199条查询结果,搜索用时 0 毫秒
41.
Across Europe, national governments have started to strategically plan adaptation to climate change. Making adaptation decisions is difficult in the light of uncertainties and the complexity of adaptation problems. Already large amounts of research results on climate impacts and adaptive measures are available, and more are produced and need to be mediated across the boundary between science and policy. Both researchers and policy-makers have started to intensify efforts to coproduce knowledge that is valuable to both communities, particularly in the context of climate change adaptation. In this paper, we present results from a study of adaptation governance and information needs, comparing eight European countries. We identify sources and means for the retrieval of information as well as gaps and problems with the knowledge provided by scientists and analyzed whether these appear to be contingent on the point in the policy-making cycle where countries are. We find that in this early phase of adaptation planning, the quality of the definition of needs, the way uncertainty is dealt with, and the quality of science–policy interaction are indeed contingent on the stage of adaptation planning, while information needs and sources are not. We conclude that a well-developed science–policy interface is of key importance for effective decision-making for adaptation.  相似文献   
42.
43.
利用卫星数据估算波罗的海的透明度和透光层深度   总被引:4,自引:0,他引:4  
波罗的海水体透明度的长期变化趋势已按富营养化的观点加以解释[1,2].可以通过遥感数据估算得到光谱衰减系数Kd(490)[3].由于漫衰减系数与透明度之间存在着经验和理论关系,因此,利用遥感数据估算海水营养状态是可能的.本文研究了遥感和水下实测Kd(490)与分别于1999年在东波罗的海本体海区[4]和2001年、2002年在西波罗的海本体海区/希默海区(Himmerfjarden)专门海上观测中获得的透明度之间的关系.利用水下测量值通过回归分析方法建立波罗的海PAR与光谱衰减系数间的关系.分析表明,在调查海区,Kd(490)约为Kd(PAR)的1.48倍.该关系用于定义透光层深度与遥感光学深度Kd(490)-1间的关系.结果表明,透光层深度约是Kd(490)-1的6.8倍.Kd(PAR)与透明度的回归分析结果证实了已有的研究结果,即Kd(PAR)为透明度倒数的1.7倍.再者,透明度与Kd(490)之间的水体成分反演算法用于模拟制作由SeaWiFS Kd(490)获得的波罗的海透明度分布图.该分布图通过海上实测数据加以验证,对卫星遥感获得的Kd(490)与实测Kd(490)做了对比,并讨论了产生误差的原因.  相似文献   
44.
Although much is known about the relationship between vigilance, group size and predation risk, behavioural responses to predation risk and their resultant costs are less clear. We investigated the response of Diana monkeys to increased predation risk by looking at behavioural changes associated with male long-distance calls, which are reliably given to certain predators. After male long-distance calls, group spread and nearest-neighbour distance decreased whilst travel and association rates for the group increased. The average height and exposure level of individuals in the group did not change after calls. Individual Diana monkeys changed their behaviour and were more likely to be vigilant or travel and less likely to engage in social or resting behaviours after long-distance calls. In addition, movement rates increased with the number of species the Diana monkeys were associated with. Diana monkey long-distance calls facilitate the joining of groups of other species. Black and white colobus and lesser spot-nosed monkeys were more likely to be in an association following a long-distance call than before. Behavioural responses, such as increased travel or association rates, that reduce foraging efficiency are interpreted as evidence of a non-lethal impact of increased predation risk.  相似文献   
45.
Declines of species in fragmented landscapes can potentially be reversed either by restoring connectivity or restoring local habitat quality. Models fitted to snapshot occupancy data can be used to predict the effectiveness of these actions. However, such inferences can be misleading if the reliability of the habitat and landscape metrics used is unknown. The only way to unambiguously resolve the roles of habitat quality and metapopulation dynamics is to conduct experimental reintroductions to unoccupied patches so that habitat quality can be measured directly from data on vital rates. We, therefore, conducted a 15-year study that involved reintroducing a threatened New Zealand bird to unoccupied forest fragments to obtain reliable data on their habitat quality and reassess initial inferences made by modeling occupancy against habitat and landscape metrics. Although reproductive rates were similar among fragments, subtle differences in adult survival rates resulted in λ (finite rate of increase) estimations of <0.9 for 9 of the 12 fragments that were previously unoccupied. This was the case for only 1 of 14 naturally occupied fragments. This variation in λ largely explained the original occupancy pattern, reversing our original conclusion from occupancy modeling that this occupancy pattern was isolation driven and suggesting that it would be detrimental to increase connectivity without improving local habitat quality. These results illustrate that inferences from snapshot occupancy should be treated with caution and subjected to testing through experimental reintroductions in selected model systems.  相似文献   
46.
Abstract

In developing countries, high levels of particle pollution from the use of coal and biomass fuels for household cooking and heating are a major cause of ill health and premature mortality. The cost and complexity of existing monitoring equipment, combined with the need to sample many locations, make routine quantification of household particle pollution levels difficult. Recent advances in technology, however, have enabled the development of a small, portable, data-logging particle monitor modified from commercial smoke alarm technology that can meet the needs of surveys in the developing world at reasonable cost. Laboratory comparisons of a prototype particle monitor developed at the University of California at Berkeley (UCB) with gravi-metric filters, a tapered element oscillating microbalance, and a TSI DustTrak to quantify the UCB particle monitor response as a function of both concentration and particle size and to examine sensor response in relation to changes in temperature, relative humidity, and elevation are presented here. UCB particle monitors showed good linearity in response to different concentrations of laboratory-generated oleic acid aerosols with a coarse (mass median diameter, 2.1 µm) and fine (mass median diameter, 0.27–0.42 µm) size distributions (average r2 = 0.997 ± 0.005). The photoelectric and ionization chamber showed a wide range of responses based on particle size and, thus, require calibration with the aerosol of interest. The ionization chamber was five times more sensitive to fine rather than coarse particles, whereas the photoelectric chamber was five times more sensitive to coarse than fine. The ratio of the response between the two sensors has the potential for mass calibration of individual data points based on estimated parameters of the size distribution. The results demonstrate the significant potential of this monitor, which will facilitate the evaluation of interventions (improved fuels, stoves, and ventilation) on indoor air pollution levels and research on the impacts of indoor particle levels on health in developing countries.  相似文献   
47.
Concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) and other organic micropollutants were determined in dated sediment/soil cores collected from the flood-plain of the river Elbe near Pevestorf (PT), approximately 125 km upstream of Hamburg, and Heuckenlock (HL) in southeast of Hamburg. Concentrations of PCDD/Fs peaked sharply at PT in the 1950s and at HL at the end of the 1940s. Cluster analyses provide evidence that the region of Bitterfeld-Wolfen (about 350-400 km upstream of Hamburg) could be the source of the PCDD/F contamination existing in the cores PT and HL since the 1940s. Obviously it is caused by sediments of the river Elbe of a similar composition. Whereas the PCDD/Fs, HCHs (hexacyclohexane isomers), DDX (DDT, DDD, DDE), and tetrachlorinated ethers in PT and HL presumably originated predominantly from the Bitterfeld-Wolfen region, organotin compounds in HL and dichlorinated haloethers in HL during the 1940s and 1950s can probably largely be attributed to emissions from the Hamburg region. Although they are separated by a large distance, in both sediment cores PT and HL concentrations and composition patterns of most organic micropollutants analyzed widely match. Inductively it can be concluded that similar contaminations will be found in many of the river bank soils between the Bitterfeld-Wolfen region and Hamburg. Excavation of top soils may uncover highly contaminated materials. Since the dated sediment cores show the variation in contaminants in the Elbe sediments over a defined time period, it is possible to make an approximate assessment of the actual degree of contamination to be expected in areas where in previous decades contaminated dredged sediments from the Elbe and from the Port of Hamburg have been deposited on land and used for building plots or for agricultural purposes.  相似文献   
48.
49.
Steffan-Dewenter I  Schiele S 《Ecology》2008,89(5):1375-1387
The relative importance of bottom-up or top-down forces has been mainly studied for herbivores but rarely for pollinators. Habitat fragmentation might change driving forces of population dynamics by reducing the area of resource-providing habitats, disrupting habitat connectivity, and affecting natural enemies more than their host species. We studied spatial and temporal population dynamics of the solitary bee Osmia rufa (Hymenoptera: Megachilidae) in 30 fragmented orchard meadows ranging in size from 0.08 to 5.8 ha in an agricultural landscape in central Germany. From 1998 to 2003, we monitored local bee population size, rate of parasitism, and rate of larval and pupal mortality in reed trap nests as an accessible and standardized nesting resource. Experimentally enhanced nest site availability resulted in a steady increase of mean local population size from 80 to 2740 brood cells between 1998 and 2002. Population size and species richness of natural enemies increased with habitat area, whereas rate of parasitism and mortality only varied among years. Inverse density-dependent parasitism in three study years with highest population size suggests rather destabilizing instead of regulating effects of top-down forces. Accordingly, an analysis of independent time series showed on average a negative impact of population size on population growth rates but provides no support for top-down regulation by natural enemies. We conclude that population dynamics of O. rufa are mainly driven by bottom-up forces, primarily nest site availability.  相似文献   
50.
Climate change may affect the frequency, intensity, and geographic distribution of severe coastal storms. Concurrent sea-level rise would raise the baseline of flooding during such events. Meanwhile, social vulnerability factors such as poverty and disability hinder the ability to cope with storms and storm damage. While physical changes are likely to remain scientifically uncertain into the foreseeable future, the ability to mitigate potential impacts from coastal flooding may be fostered by better understanding the interplay of social and physical factors that produce human vulnerability. This study does so by integrating the classic causal model of hazards with social, environmental, and spatial dynamics that lead to the differential ability of people to cope with hazards. It uses Census data, factor analysis, data envelopment analysis, and floodplain maps to understand the compound social and physical vulnerability of coastal residents in the city of Revere, MA, USA. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号