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   112篇
  免费   2篇
安全科学   3篇
废物处理   6篇
环保管理   22篇
综合类   10篇
基础理论   26篇
污染及防治   26篇
评价与监测   6篇
社会与环境   14篇
灾害及防治   1篇
  2022年   1篇
  2021年   1篇
  2020年   1篇
  2018年   11篇
  2017年   5篇
  2016年   2篇
  2015年   4篇
  2014年   5篇
  2013年   4篇
  2012年   5篇
  2011年   11篇
  2010年   7篇
  2009年   7篇
  2008年   7篇
  2007年   12篇
  2006年   7篇
  2005年   4篇
  2004年   1篇
  2003年   2篇
  2002年   4篇
  2001年   2篇
  2000年   1篇
  1998年   2篇
  1997年   2篇
  1994年   1篇
  1992年   1篇
  1990年   1篇
  1985年   1篇
  1982年   1篇
  1981年   1篇
排序方式: 共有114条查询结果,搜索用时 31 毫秒
101.
The efficiency of a biopurification system, developed to treat pesticide contaminated water, is to a large extent determined by the chemical and hydraulic load. Insight into the behaviour of pesticides under different fluxes is necessary. The behaviour of metalaxyl, bentazone, linuron, isoproturon and metamitron was studied under three different fluxes with or without the presence of pesticide-primed soil in column experiments. Due to the time-dependent sorption process, retention of the pesticides with intermediate mobility was significantly influenced by the flux. The higher the flux, the slower pesticides will be sorbed, which resulted in a lower retention. Degradation of the intermediate mobile pesticides was also submissive to variations in flux. An increase in flux, led to a decrease in retention, which in turn decreased the opportunity time for biodegradation. Finally, the presence of pesticide-primed soil was only beneficial for the degradation of metalaxyl.  相似文献   
102.
Starting from a risk conflicts perspective, this article challenges two common assumptions of existing research on climate change in public and media discourses. It argues that the evaluation of these discourses on the extent to which these either accurately reflect a scientific consensus or contribute to achieving social consensus insufficiently takes account of the exclusionary mechanisms it starts from. A conceptual and empirical framework is subsequently put forward which allows one to evaluate mediated discourses in terms of the extent to which democratic debate and citizenship are encouraged. Such analysis can reveal the discursive strategies underlying processes of politicization and depoliticization. This perspective is illustrated by an analysis of a local case study: the “Sing for the Climate” campaign. We conclude by calling for a broad systematic research agenda revealing the extent to which de/politicizing discourses are found to influence public and media discourses.  相似文献   
103.
Sampling can be the source of the greatest errors in the overall results of foliar analysis. This paper reviews the variability in heavy metal concentrations in tree crowns, which is a feature that should be known and understood when designing a suitable leaf sampling procedure. The leaf sampling procedures applied in 75 articles were examined. Most of the environmental studies used a closely related form of the UN/ECE-EC leaf sampling procedure, which was developed for the long-term monitoring of forest condition. Studies with objectives outside the UN/ECE-EC field of application should utilize a sampling procedure that is in accordance with the objectives of the study and based on the observed variation in pilot and similar studies. The inherent sources of heavy metal variability inside the stand, i.e. the crown class, stand management, site properties, crown dimensions, infections, seasons, etc. were discussed, but the underlying causes of this variability are rarely understood. The inherent variability in tree crowns is the reason for using leaf sampling as a tool in pollution studies. The objectives of a pollution study determine which sources of variability are utilized by the researcher.  相似文献   
104.
The objective of this study was to evaluate vegetation recovery on footpaths in woodland that have been closed for access for 6 years. A vegetation survey was conducted in four mesophile forests, in transects perpendicular to the trail. Analyses concentrated on the direction and rate of the recovery process. Vegetation on trail sides in these ecosystems recovered substantially. Non-metric multidimensional scaling based upon species composition separated the four sample locations and each cluster contained representatives of the three major trail zones: path centre, transition and undisturbed zones. Analysis of distribution of life forms, plant strategies and seedbank longevity indices showed no differences between trail zones. This indicates that vegetation on the path centre is likely to recover towards the plant composition of the undisturbed zone. Ellenberg values indicate that environmental variation is not related to former path structures, as significant variability was only observed between the forest sites. Furthermore, the analysis concentrated on characteristics of species relevant to the recovery process.  相似文献   
105.
During the second half of the 1990s the combination of ecological and economic targets in industrial land‐use planning became an official part of spatial‐economic policy in the Netherlands. A growing number of business locations are now being developed or re‐developed as ‘sustainable business sites’. At the same time, ‘parkmanagement’ came into existence as a new tool for development and control of business sites for industry and services. Parkmanagement is now regarded as one of the obvious instruments to realize sustainable (or ‘careful’) land use on business parks. However, there is now a question about whether it is wrong for local governments (which in the Dutch case are responsible for most land development schemes) to have so much participation in parkmanagement initiatives. There is a threat that local governments are welcoming parkmanagement as a fashionable way to impose new regulations on business establishments, and ignore the evidence from practice. Such evidence shows that parkmanagement is most successful when organized with the involvement of private enterprises. This would also be more in line with the modern interaction‐oriented planning theory (consensus planning). The paper describes the principal dilemmas facing local governments in business site development, the theoretical options for influencing the development process of the sites, and the set of actions that could be part of a parkmanagement strategy. These can be arranged on a ‘ladder’ or range of activities, from rather simple facilities serving individual companies' needs, such as maintenance and security, to more complex co‐operation projects in combined transport or energy supply, and ultimately lead to schemes for connecting material flows of production processes. The successive stages of the ladder of business site facilities can be combined with different forms and stages of process organization.  相似文献   
106.
When water supply improvements are coupled with opportunity to create income through micro–enterprises, time released from water collection is converted into income earned. This brings several benefits: reduced drudgery, higher household income, and, consequently, greater women's empowerment through changing gender relations within the household. This article documents the performance of one such scheme in Banaskantha District in the state of Gujarat in India, one of poorest districts in the state and the country. Here, due to the efforts of the Self–Employed Women's Association (SEWA), an Indian NGO, poor women are reaping the social and economic benefits of a government–run regional piped water supply scheme, a project funded by Dutch bilateral aid, focusing on women's development. If government policy–makers took the cue and formulated programmes and schemes that combined these two aspects, viz., actions that release time for rural women from daily chores (e.g., collecting water, fuel wood and fodder)and opportunities for sustainable micro–enterprises to convert time saved into income, this could become a reliable route out of rural poverty into gender–sensitive sustainable development.  相似文献   
107.
Long-term future development of European agriculture within the global market is highly uncertain, but can potentially have large impacts on the future of agricultural businesses, rural communities and amenities such as traditional landscapes and biodiversity. Despite great uncertainties it is of interest to explore the extent of these potential changes. This paper provides an explorative scenario of the European crop production in a liberalised world without European Union (EU) market interventions. The results do not form a prediction or a business as usual scenario, but rather a plausible and salient thought-experiment of a possible future based on the consistent integration of current conceptual and quantitative models.Future scenarios for climate, demography, technology and global demand for agricultural commodities are used to assess the competitiveness of European agriculture. Regional economic competitiveness is determined by combining indicators for the economic strength of farms in a region and population pressure on agricultural land, and subsequently used to determine where agricultural production is likely to sustain under the market liberalisation scenario. The method is illustrated for the 27 EU member state countries for three commodities: wheat, potato and milk (relying on grass).Results include maps of the dominant wheat, potato and milk producing regions across Europe as projected for 2050. They show that due to increased agricultural productivity, less agricultural land will be needed to supply the European demand for food and feed. In addition, production will concentrate in those regions which have a comparative advantage. This potentially leads to a strong polarisation between north-western Europe and southern Europe, which faces negative impacts of climate change and central and northern Europe where agricultural businesses lag in economic strength and farm size. A contrasting policy intervention scenario illustrates how differences in demand and productivity result in an expansion of the agricultural area, especially for the production of wheat.Although the complete liberalisation scenario may seem unlikely, and the underlying assumptions have great uncertainty, the results help identify and map market pressures on agricultural land use across regions in Europe. As such, it stimulates policy debate on the desired future for the European agricultural sector and the trade-offs between economic competitiveness under global market conditions and policy intervention. In addition, it provides a basis for the planning of alternative economic strategies for agriculturally less competitive regions.  相似文献   
108.
Historical processes constrain patterns in global diatom diversity   总被引:8,自引:0,他引:8  
There is a long-standing belief that microbial organisms have unlimited dispersal capabilities, are therefore ubiquitous, and show weak or absent latitudinal diversity gradients. In contrast, using a global freshwater diatom data set, we show that latitudinal gradients in local and regional genus richness are present and highly asymmetric between both hemispheres. Patterns in regional richness are explained by the degree of isolation of lake districts, while the number of locally coexisting diatom genera is highly constrained by the size of the regional diatom pool, habitat availability, and the connectivity between habitats within lake districts. At regional to global scales, historical factors explain significantly more of the observed geographic patterns in genus richness than do contemporary environmental conditions. Together, these results stress the importance of dispersal and migration in structuring diatom communities at regional to global scales. Our results are consistent with predictions from the theory of island biogeography and metacommunity concepts and likely underlie the strong provinciality and endemism observed in the relatively isolated diatom floras in the Southern Hemisphere.  相似文献   
109.
Since 2006, around 600 rainwater harvesting systems have been constructed for agricultural irrigation in Beijing. The financial and economic implications of using these systems are discussed less. It is important to understand the effectiveness of the investments spent on the rainwater harvesting systems. The paper aims to analyze economic and financial performance of the constructed rainwater harvesting systems in rural areas of Beijing through the method of cost benefit analysis. The economic analysis focuses on determining the contribution of rainwater harvesting systems to the development of society, carried out from the point of view of government. The financial analysis allows comparison of the financial implications of using groundwater with using rainwater for agricultural irrigation from the point of view of individual participant, namely the local farmers. The results show that the rainwater harvesting systems are economically feasible. This means rainwater harvesting have positive effects for society. However, the financial feasibility of rainwater harvesting systems depends on the charge for groundwater and on the size of the rainwater harvesting systems. If groundwater is not charged, the rainwater harvesting systems are not financially feasible. If groundwater is charged at 2 Yuan/m3, only large size systems are financially feasible while small and middle sizes systems are not financially feasible. Under these circumstances, only large systems can run smoothly, while farmers may not use the small and medium-size systems.  相似文献   
110.
Goodman BA  Johnson PT 《Ecology》2011,92(3):542-548
Parasites can cause dramatic changes in the phenotypes of their hosts, sometimes leading to a higher probability of predation and parasite transmission. Because an organism's morphology directly affects its locomotion, even subtle changes in key morphological traits may affect survival and behavior. However, despite the ubiquity of parasites in natural communities, few studies have incorporated parasites into ecomorphological research. Here, we evaluated the effects of parasite-induced changes in host phenotype on the habitat use, thermal biology, and simulated predator-escape ability of Pacific chorus frogs (Pseudacris regilla) in natural environments. Frogs with parasite-induced limb malformations were more likely to use ground microhabitats relative to vertical refugia and selected less-angled perches closer to the ground in comparison with normal frogs. Although both groups had similar levels of infection, malformed frogs used warmer microhabitats, which resulted in higher body temperatures. Likely as a result of their morphological abnormalities, malformed frogs allowed a simulated predator to approach closer before escaping and escaped shorter distances relative to normal frogs. These data indicate that parasite-induced morphological changes can significantly alter host behavior and habitat use, highlighting the importance of incorporating the ubiquitous, albeit cryptic, role of parasites into ecomorphological research.  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