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   257篇
  免费   22篇
  国内免费   11篇
安全科学   13篇
废物处理   4篇
环保管理   67篇
综合类   77篇
基础理论   51篇
环境理论   1篇
污染及防治   31篇
评价与监测   14篇
社会与环境   24篇
灾害及防治   8篇
  2024年   1篇
  2023年   1篇
  2022年   5篇
  2021年   12篇
  2020年   4篇
  2019年   6篇
  2018年   6篇
  2017年   17篇
  2016年   16篇
  2015年   12篇
  2014年   14篇
  2013年   32篇
  2012年   7篇
  2011年   26篇
  2010年   4篇
  2009年   12篇
  2008年   10篇
  2007年   17篇
  2006年   15篇
  2005年   7篇
  2004年   11篇
  2003年   5篇
  2002年   7篇
  2001年   7篇
  2000年   4篇
  1999年   3篇
  1998年   2篇
  1997年   5篇
  1996年   1篇
  1995年   4篇
  1994年   3篇
  1993年   2篇
  1992年   2篇
  1991年   2篇
  1988年   2篇
  1987年   1篇
  1984年   1篇
  1983年   3篇
  1979年   1篇
排序方式: 共有290条查询结果,搜索用时 0 毫秒
281.
How an economically affordable, environmentally effective and socially acceptable municipal solid waste management system can be developed is currently unclear. Considerable research has been carried out on the practical aspects of municipal waste management (i.e. transport, treatment and disposal) and how citizens feel about source separation, recycling, incineration and landfill but the perspective of the waste manager within the context of long term planning is often ignored. In this study, waste managers from 11 different leading-edge European municipal solid waste programs in nine different countries were interviewed. The economic, social, political, environmental, legal and technical factors of their specific programs were explored and analyzed. The transition of municipal solid waste management to urban resources management was observed and key ‘system drivers’ for more sustainable waste management practices were identified. Programs visited were: Brescia (I), Copenhagen (DK), Hampshire (UK), Helsinki (FI), Lahn-Dill-Kreis (D), Malmö (SE), Pamplona (E), Prato (I), Saarbrücken (D), Vienna (A), and Zürich (CH).  相似文献   
282.
SUMMARY

Over-population in relation to poor land productivity and cultivation in less fertile lands is resulting in land degradation and deforestation in UP hills. Growing demand of more food production and increasing need for more cash in hand have forced the hill people to cultivate all kinds of land, resulting in the denudation of land resources and soil erosion. These changes resulted in out migration of the area's human resource. A new management system for the revival of natural resources and the sustainable utilization of the area's human population and livestock has been proposed, involving active local participation in order to change the existing land-use to a system based on the soil fertility scale.  相似文献   
283.
Within the context of its institutional scientific support to the European Commission, in 2005 the Radioactivity Environmental Monitoring (REM) group at the Joint Research Centre of the European Commission, started to explore the possibility of mapping indoor radon in European houses as a first step towards preparing a European Atlas of Natural Radiations. The main objective of such an atlas is to contribute to familiarizing the public with its naturally radioactive environment. The process of preparing the atlas should also provide the scientific community with a database of information that can be used for further studies and for highlighting regions with elevated levels of natural radiation. This document presents the status of the European indoor radon (Rn) map, first statistical results, and outlines of forthcoming challenges.  相似文献   
284.
Temporal variation of radon-222 concentration was studied at the Syabru-Bensi hot springs, located on the Main Central Thrust zone in Central Nepal. This site is characterized by several carbon dioxide discharges having maximum fluxes larger than 10 kg m−2 d−1. Radon concentration was monitored with autonomous Barasol™ probes between January 2008 and November 2009 in two small natural cavities with high CO2 concentration and at six locations in the soil: four points having a high flux, and two background reference points. At the reference points, dominated by radon diffusion, radon concentration was stable from January to May, with mean values of 22 ± 6.9 and 37 ± 5.5 kBq m−3, but was affected by a large increase, of about a factor of 2 and 1.6, respectively, during the monsoon season from June to September. At the points dominated by CO2 advection, by contrast, radon concentration showed higher mean values 39.0 ± 2.6 to 78 ± 1.4 kBq m−3, remarkably stable throughout the year with small long-term variation, including a possible modulation of period around 6 months. A significant difference between the diffusion dominated reference points and the advection-dominated points also emerged when studying the diurnal S1 and semi-diurnal S2 periodic components. At the advection-dominated points, radon concentration did not exhibit S1 or S2 components. At the reference points, however, the S2 component, associated with barometric tide, could be identified during the dry season, but only when the probe was installed at shallow depth. The S1 component, associated with thermal and possibly barometric diurnal forcing, was systematically observed, especially during monsoon season. The remarkable short-term and long-term temporal stability of the radon concentration at the advection-dominated points, which suggests a strong pressure source at depth, may be an important asset to detect possible temporal variations associated with the seismic cycle.  相似文献   
285.
The limnological record of human impact on catchment land cover and on lake sedimentation during the historical period has been established for Pinto Lake in Central Coastal California. In addition, the sedimentary record of the ‘pre-impact’ condition preserves evidence of a climatic control on the nature of lake sedimentation. Chronological marker horizons have been determined using pollen data in combination with the documented land-use history and introductions of exotic species. Further chronological data have been determined using 14C and 137Cs. The impact of Mexican and Euro-American immigrants and their ‘imported’ land-use practices is clearly reflected in an order of magnitude increase in the rate of lake sedimentation to c. 9 kg m−2 year−1 (c. 2 cm year−1) between 1770 and 1850. Here, the occurrence of exotic plant species indicates disturbance as early as c. 1769–1797, whilst redwood deforestation between 1844 and 1860 represents the most significant human impact. Changes in the nature of sedimentation prior to this reveal a high degree of sensitivity to changes in precipitation where subtle decreases in lake level and the supply of runoff-derived mineral matter have resulted in two periods of organic lake sedimentation c. 650–900 and 1275–1750. Set against this background condition of high sensitivity, the dramatic impacts of Euro-American settlement are unsurprising. An erratum to this article can be found at  相似文献   
286.
The drastic socio-economic and political changes that occurred after the breakdown of socialism in Eastern Europe triggered widespread land use change, including cropland abandonment and forest cover changes. Yet the rates and spatial patterns of post-socialist land use change remain largely unclear. We used Landsat TM/ETM+ images to classify land cover maps and assess landscape pattern changes from 1990 to 2005 in Argeş County, Southern Romania. Cropland abandonment was the most widespread change (21.1% abandonment rate), likely due to declining returns from farming, tenure insecurity, and demographic developments during transition. Forest cover and forest fragmentation remained remarkably stable during transition, despite widespread ownership transfers. Cropland abandonment provides opportunities for increased carbon sequestration, but threatens cultural landscapes and biodiversity. Continued monitoring is important for assessing whether abandoned croplands will eventually reforest or be put back into production and to better understand the consequences of post-socialist land use change for ecosystems and biodiversity.  相似文献   
287.
The giant panda was found on Mount Shennongjia in Central China for thousands of years but vanished in the late 19th century. The possibility for reintroducing the giant panda in Shennongjia is discussed in terms of food availability, carrying capacity, and predicted bamboo flowering. Three species (Fargesia spathacea, F. murielae, and Yushania confusa) are considered the preferred forage bamboos, which could feed 193–223 giant pandas. However, in 1879–1888 these three species synchronously flowered and died back. In the past, such bamboo flowering usually forced the panda to migrate to a new habitat where forage bamboos were available. But since the 19th century, Shennongjia has become separated from other panda habitats by densely populated agricultural zones. Multi-species flowering of the forage bamboo and isolating of the habitat might caused the extinct of the giant panda in Shennongjia. If the flowering cycle of the bamboo is genetically fixed, the next synchronous flowering of two staple food species (F. spathacea and F. murielae) may occur in 2436–2439. It means that the food supply is dependable in Shennongjia for reintroducing the giant panda before 2436.  相似文献   
288.
The Central Himalayan region is suffering from severe ecological problems as a consequence of deforestation and that threatens the subsistence population of the region. We analyze this problem and propose a plan for ecologically sustainable development for the region based on an analysis of the interrelationships of various ecosystems, particularly cropland and forest ecosystems, around which most human activities are concentrated. Each energy unit of agronomic yield leads to expenditure of about 12 energy units of forest/grazing land energy. Because with rapidly declining forest area, this form of agriculture is no longer sustainable and cannot be converted into a fossil fuel-based agriculture, we propose that agriculture in the mountain region has to be largely replaced with farm forests to revitalize the environment and to generate the basic needs of the subsistence economy of the hill population whose food grain needs can be met from the plains. We conclude by describing the advantages that are likely to accrue to the people for their long-term future. In terms of both energy and money, the value of resources collected from the forest to support agriculture in the present systems far exceeds the value of food grain that would be required to enable the proposed farm forest-based systems to function. At regional level, the proposed system would generate more energy than the existing systems, not only because the productivity of forest is about tenfold greater than that of cropland, but also because the proposed plan promotes recovery of various ecosystems.  相似文献   
289.
自然中心主义环境伦理思想作为目前最为热门的学科之一,自然同其它学科一样,有它产生的思想根源、现实缘由和直接的动因。工业社会的精神失落和蓬勃兴起的绿色运动是其思想诱因与直接动因,而它形成的现实缘由则主要是全球面临的生态困境以及对人与自然关系的重新认识。  相似文献   
290.
Due to rapid industrialization, with high population density and constraints of land, it is expected that level of risks arising from the hazardous industries will increase in India in the coming decades. However, 30 years after the Bhopal accident (1984), except a few discrete regulations, there is as yet no integrated system for assessing and managing risks arising out of these hazardous industries in India. The gravity of aspects related to the management of industrial risk still remains crucially important. In particular, there is no standard guideline on risk analysis methodology, acceptability or tolerability criteria, nor is there an accident database or a risk reduction strategy for the areas where risk levels are already high. On top of this, there are technical and legislative gaps in the institutional framework to implement any of the above mentioned issues. With the backdrop of the Bhopal gas tragedy, the objective of this paper is therefore to evaluate the effectiveness of a comprehensive risk assessment framework for the emerging economy of India, in order to control and/or to reduce the risk level that exists. In this context, regulations and policies pertaining to industrial risk assessment were reviewed.  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