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   9824篇
  免费   3篇
  国内免费   2篇
安全科学   1篇
废物处理   778篇
环保管理   1219篇
综合类   959篇
基础理论   3135篇
污染及防治   1791篇
评价与监测   1036篇
社会与环境   909篇
灾害及防治   1篇
  2023年   6篇
  2022年   14篇
  2021年   13篇
  2020年   2篇
  2019年   8篇
  2018年   1480篇
  2017年   1378篇
  2016年   1203篇
  2015年   130篇
  2014年   29篇
  2013年   21篇
  2012年   469篇
  2011年   1347篇
  2010年   701篇
  2009年   608篇
  2008年   885篇
  2007年   1237篇
  2006年   6篇
  2005年   22篇
  2004年   39篇
  2003年   63篇
  2002年   105篇
  2001年   16篇
  2000年   10篇
  1999年   4篇
  1998年   9篇
  1990年   1篇
  1984年   11篇
  1983年   8篇
  1979年   1篇
  1961年   1篇
  1935年   2篇
排序方式: 共有9829条查询结果,搜索用时 0 毫秒
991.
Anthropogenic biomass burning in insular Southeast Asia facilitates conversion and degradation of ecosystems and emits high amounts of carbon into the atmosphere. We analyzed the influence of peat soil and land cover distribution on the occurrence and characteristics of vegetation fires. Two years of satellite-based active fire detections over Peninsular Malaysia, Sumatra, Borneo and Java were examined together with land cover and peatland maps. Our results showed that fire occurrence nearly tripled (23,000 → 68,000) from a wet La Niña year (2008) to a drier El Niño year (2009). In both years, fires were concentrated in peatlands (in 2009 41% of fires vs. 10% of land area), and the majority of large-scale burning took place in peatlands. Variation in peatland land cover within the study area was noticed to create remarkable different fire regimes. Biomass burning in the intensely managed Sumatran peatlands was characterized by large-scale land clearance fires that took place annually to varying extent. The largely unmanaged degraded peatland ecosystems of Borneo, on the other hand, experienced very little fire activity in a wet year but were ravaged by large-scale wildfires when El Niño conditions arose. We conclude that fire regime characteristics in insular Southeast Asia are strongly connected to occurrence of peat soil and land management status. This leads to high variation of fire activity within this region both annually (depending on weather patters) and over longer time range (depending on land cover/management issues) and greatly complicates estimation of the effects of fires.  相似文献   
992.
A regional climate change impact assessment was conducted which investigated the timing of the first appearance of furunculosis caused by the bacterium, Aeromonas salmonicida, in fish of the Ouje-Bougoumou region of northern Quebec, Canada. Historical data were used to assess whether there was a temporal relationship between increased temperatures (observed climate data) and the appearance of furunculosis (traditional environmental knowledge was used to provide context). To project future impacts of climate change, climate models and lake models were used. Regression analysis revealed a significant, positive temporal trend in mean air temperature. The temperature range conducive to A. salmoncida survival coincided with the first appearance of furunculosis. In addition, it is predicted that lake temperatures will remain suitable for the presence of A. salmonicida into the future; it is likely that the disease will persist throughout the twenty-first century. Climate change appears to be a factor explaining the onset of furunculosis; however, other factors/stressors cannot be discounted, such as, the effects past mining activities near the lakes of the Ouje-Bougoumou region have had on the body burden of contaminants in the fish (and the potential effects on the fish immune system).  相似文献   
993.
Rapid land-use change arising from incentives for afforestation has created tensions in rural communities previously dominated by agricultural enterprises. This paper reports on an innovative experiment with social learning that incorporated participatory modelling to resolve community concerns in a case study of plantation forestry in the Upper Clarence catchment of north-eastern NSW Australia. The development of a diagnostic framework helped identify socioeconomic and environmental issues within the community for investigation by a self-selected participatory advisory committee (PAC) representing a diversity of views. Implementation of a social learning exercise offered empathetic and intellectual engagement among PAC members that maintained interest, built confidence, and improved problem-solving capacity while fostering group ownership over decision making. A shared understanding of dynamic landscape problems helped empower participants to collaboratively develop solutions for improved management and operational practices, and cooperate to explore further options for plantation industry development under existing policy guidelines which are presented in this paper. As a result of frank discussions between diverse stakeholders in a mutually respectful learning environment that combined local, scientific and expert knowledge, concerns dissipated and participants developed a more favourable view of plantation forestry activity.  相似文献   
994.
Using the focusing event framework, a comprehensive analysis of private households’ and businesses’ preparedness was undertaken in the aftermath of the 2002 and 2006 flood events on the Elbe River in Germany. In August 2002, preparedness of households (n = 235) and businesses (n = 103) was low: 30% of the households and 54% of the businesses took no precautionary measures before the flood event. Many undertaken emergency measures were ineffective, since only 26% of all households knew how to react when the flood warning came, and only 9% of businesses had an emergency plan in place. Due to this extreme flood, double-loop learning occurred in many households and businesses, so that many did implement precautionary measures. The distribution of adopted precautionary measures for households fits well to Preisendörfer’s low-cost hypothesis, but does not apply for businesses. Only 10% of the households (n = 112), but still 29% of the businesses (n = 41) were unprepared before the flood in 2006. Significant improvement in flood preparedness activities is still necessary. Particularly for businesses, regulatory programs and programs encouraging proactive behaviour should be implemented. The focusing event framework proofed to be a useful tool for a differentiated analysis of the responses to and learning due to a disaster also in the commercial and private sector.  相似文献   
995.
The current state of Mediterranean mountain areas has been driven by two main factors: intense traditional human activity and the dynamics of the ecosystem itself. In this study, we examine land-cover changes in a National Park in the Pyrenees mountains (NE Iberian Peninsula), which was designated a protected area 55 years ago. First, we have analyzed spatio-temporal changes in land-cover pattern and forest dynamics from 1957 to 2005. During this period, land-cover dynamics consisted of two main processes: (i) expansion of the forest area and (ii) increasing cover of forests already present in 1957. To analyze the role of the conservation level of the park, we have also compared the results obtained within the park with those of unprotected, peripheral areas. In the two areas with different protection level, dense forests increased throughout the period because of the reduction in forestry activities. The peripheral area showed a higher rate of forest-cover change from 1957 to 2005 compared to the National Park. This higher increase in forest cover in the peripheral area could be related to a higher proportion in the National Park of screes and rocky areas and to the decline and transformation of forest activities in these peripheral, lower elevation areas.  相似文献   
996.
997.
This paper introduces an integrated water management model at the industrial park level. It suggests four approaches to water management: first, direct water reuse among users; second, water reuse among users by blending with freshwater; third, water reuse between users and a wastewater treatment plant; and fourth, groundwater recharge by reclaimed wastewater or other feasible applications in order to optimize the overall water efficiency. The model results in a comprehensive management methodology for optimizing water resources within an industrial park, seeking potential water reuse among industries, and incorporating the size and cost of reclaimed wastewater delivery systems. A case study is employed to test the model’s feasibility. An economic analysis of the optimized water use network is also carried out, showing the potential water and cost savings.  相似文献   
998.
We tested separately the effect of two taxonomically related rotifers (B. patulus and B. macracanthus) on the population dynamics of another species (A. fissa) at low (0.5 ×10 6) and high food levels (1.5 × 106 cells/ml of Chlorella vulgaris) using different inoculation densities (0–100%). We also quantified the impact of A. fissa on the two brachionid species. Regardless of the presence of the competing species, an increase in the availability of food led to increase in the abundances of the three rotifers. The population growth of B. patulus, B. macracanthus, or A. fissa was affected negatively when cultured together with another species. An increase in the initial density of any one of the competing species became advantageous to maintain a certain population size. At a low algal food level, B. patulus was able to suppress A. fissa more strongly than B. macracanthus. On the other hand, at a high food level, B. macracanthus suppressed the population of A. fissa more strongly than B. patulus. Peak population densities for A. fissa varied from about 150 to 1000 ind./ml, depending on food density and the presence of competitors. The rate of population increase (r) of A. fissa, B. patulus, and B. macracanthus increased with an increase in food availability but decreased with increasing initial density of the competitor. Both Brachionus spp. experienced negative growth rates in the presence of A. fissa, especially at a high initial density of the latter. Published in Russian in Ekologiya, 2007, Vol. 38, No. 5, pp. 381–390. The article was submitted by the authors in English.  相似文献   
999.
This study estimates efficient nitrogen load reductions to the Stockholm archipelago, a Swedish coastal zone in the Baltic Sea, and compares these with politically determined and implemented nitrogen abatement programs. The region is relatively well equipped with necessary data, and a simple programming model is constructed. The results show a large divergence in efficient nitrogen reductions, mainly due to the divergences in benefit estimates from water quality improvements in the archipelago. However, the results need to be interpreted with caution due to all uncertainties related to predicting net values from changes in nitrogen load to a coastal zone. In spite of this, it is still of policy relevance to infer results which show that the politically determined target coincides with an efficient nitrogen reduction at relatively low benefit estimate, but that actual net benefits could be increased from a reallocation of abatement measures towards more low cost measures.  相似文献   
1000.
Contrary to claims from American politicians, lobbyists, and oil and gas executives, allowing energy development in the Alaskan Arctic National Wildlife Refuge (ANWR) will harm the environment, compromise international law, erode the social significance of wilderness protection, and ultimately fail to␣increase the energy security of the United States. After exploring a brief history of the ANWR controversy, this piece argues that the operation of oil and gas refineries in ANWR will release discharged solids, drilling waste, and dirty diesel fuel into the ecosystem’s food-chain, as they have from oil operations in Prudhoe Bay. Less obvious but equally important, oil and gas exploration in ANWR will violate a number of international treaties on biodiversity protection. In the end, development in ANWR will threaten the concept of wilderness protection, and will do little to end US dependence on foreign sources of energy. About the Author: Benjamin K. Sovacool is a doctoral candidate in the Department of Science and Technology Studies at the Virginia Polytechnic Institute & State University in Blacksburg, Virginia. He works as a research analyst for the Consortium on Energy Restructuring and is a Senior Research Fellow for the Virginia Center for Coal and Energy Research. He also just completed a Graduate Fellowship in Energy Policy at the Oak Ridge National Laboratory in Oak Ridge, Tennessee. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.  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