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   11098篇
  免费   16篇
  国内免费   40篇
安全科学   22篇
废物处理   857篇
环保管理   1360篇
综合类   1062篇
基础理论   3356篇
环境理论   2篇
污染及防治   2241篇
评价与监测   1274篇
社会与环境   976篇
灾害及防治   4篇
  2023年   59篇
  2022年   173篇
  2021年   115篇
  2020年   25篇
  2019年   47篇
  2018年   1508篇
  2017年   1422篇
  2016年   1274篇
  2015年   166篇
  2014年   93篇
  2013年   179篇
  2012年   519篇
  2011年   1420篇
  2010年   743篇
  2009年   653篇
  2008年   947篇
  2007年   1278篇
  2006年   64篇
  2005年   54篇
  2004年   56篇
  2003年   82篇
  2002年   126篇
  2001年   22篇
  2000年   17篇
  1999年   7篇
  1998年   12篇
  1997年   2篇
  1996年   8篇
  1995年   2篇
  1994年   5篇
  1993年   3篇
  1992年   3篇
  1989年   2篇
  1988年   3篇
  1985年   2篇
  1984年   13篇
  1983年   12篇
  1982年   5篇
  1979年   2篇
  1966年   1篇
  1965年   2篇
  1964年   2篇
  1962年   2篇
  1961年   4篇
  1958年   3篇
  1957年   3篇
  1956年   2篇
  1955年   4篇
  1953年   1篇
  1935年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
881.
Exploitation of certain resources within a protected area on a sustainable basis could contribute to higher living standards of rural people, particularly those in poor countries, and decrease conflicts between these populations and park authorities. This article presents data from a case study of Kopaonik National Park (NP), Serbia, which is a park with natural resources, most notably bilberries, which have always been relied on by local people. Vaccinium myrtillus traditionally has been collected for decades in Kopaonik NP and used by local people. However, little is known about the socioeconomic and ecological relations that affect the collection and use of this species. The aim of the present study was to understand how local people collect bilberries in Kopaonik NP and what their attitudes toward the park are. Household questionnaire data were used to examine how local people collect bilberries and how to improve the relations between local people and NP authorities. The survey questionnaire included 52 households from 7 local communities, and we applied a purposive sampling strategy. In addition, expert interviews were conducted, and from these data we obtained a broader understanding of the relation between local people and NP authorities. The results indicate that in Kopaonik NP, there is a conflict between pickers and NP authorities. Sustainable management should be directed toward the protection of bilberries. Education of local people is a key element in the sustainable collection and protection of natural resources.  相似文献   
882.
Natural and man-made magnetic and electromagnetic fields are important factors in the contemporary life. The paper discusses the role of environmental magnetic and electromagnetic fields in origin and evolution of life. A brief review of the characteristics of Earth magnetic field, Earth magnetosphere, and their role as a shield for cosmic radiation follows. The role of endogenous and exogenous magnetic fields is discussed in respect of the clarification of the potential hazard and benefit of electromagnetic fields. The second part of the paper discusses the mechanisms of detection and response to exogenous electromagnetic fields, as well as threshold versus window hypothesis for mechanisms of interactions. Finally, the necessity of accurate dosimetry at the target site and the importance of relevant research and clinical protocols in studying biological responses are pointed out.  相似文献   
883.
Forest management can benefit from decision support tools, including GIS-based multicriteria decision-aiding approach. In the Mediterranean region, Pinus pinaster forests play a very important role in biodiversity conservation and offer many socioeconomic benefits. However, the conservation of this species is affected by the increase in forest fires and the expansion of Matsucoccus feytaudi. This paper proposes a methodology based on commonly available data for assessing the values and risks of P. pinaster forests and to generating maps to aid in decisions pertaining to fire and phytosanitary risk management. The criteria for assessing the values (land cover type, legislative tools for biodiversity conservation, environmental tourist sites and access routes, and timber yield) and the risks (fire and phytosanitation) of P. pinaster forests were obtained directly or by considering specific indicators, and they were subsequently aggregated by means of GIS-based multicriteria analysis. This approach was tested on the island of Corsica (France), and maps to aid in decisions pertaining to fire risk and phytosanitary risk (M. feytaudi) were obtained for P. pinaster forest management. Study results are used by the technical offices of the local administration—Corsican Agricultural and Rural Development Agency (ODARC)—for planning the conservation of P. pinaster forests with regard to fire prevention and safety and phytosanitary risks. The decision maker took part in the evaluation criteria study (weight, normalization, and classification of the values). Most suitable locations are given to target the public intervention. The methodology presented in this paper could be applied to other species and in other Mediterranean regions.  相似文献   
884.
Forest Ecosystem Services and Eco-Compensation Mechanisms in China   总被引:1,自引:0,他引:1  
Forests are a major terrestrial ecosystem providing multiple ecosystem services. However, the importance of forests is frequently underestimated from an economic perspective because of the externalities and public good properties of these services. Forest eco-compensation is a transfer mechanism that serves to internalize the externalities of forest ecosystem services by compensating individuals or companies for the losses or costs resulting from the provision of these services. China’s current forest eco-compensation system is centered mainly on noncommercial forest. The primary measures associated with ecosystem services are (1) a charge on destructive activities, such as indiscriminate logging, and (2) compensation for individual or local activities and investments in forest conservation. The Compensation Fund System for Forest Ecological Benefits was first listed in the Forest Law of the People’s Republic of China in 1998. In 2004, the Central Government Financial Compensation Fund, an important source for the Compensation Fund for Forest Ecological Benefits, was formally established. To improve the forest eco-compensation system, it is crucial to design and establish compensation criteria for noncommercial forests. These criteria should take both theoretical and practical concerns into account, and they should be based on the quantitative valuation of ecosystem services. Although some initial headway has been made on this task, the implementation of an effective forest eco-compensation system in China still has deficiencies and still faces problems. Implementing classification-based and dynamic management for key noncommercial forests and establishing an eco-compensation mechanism with multiple funding sources in the market economy are the key measures needed to conquer these problems and improve the forest eco-compensation system and China’s forestry development in sequence.  相似文献   
885.
Increasingly government agencies are seeking to quantify the outcomes of proposed policy options in terms of ecosystem service benefits, yet conflicting definitions and ad hoc approaches to measuring ecosystem services have created confusion regarding how to rigorously link ecological change to changes in human well-being. Here, we describe a step-by-step framework for producing ecological models and metrics that can effectively serve an economic-benefits assessment of a proposed change in policy or management. A focus of the framework is developing comparable units of ecosystem goods and services to support decision-making, even if outcomes cannot be monetized. Because the challenges to translating ecological changes to outcomes appropriate for economic analyses are many, we discuss examples that demonstrate practical methods and approaches to overcoming data limitations. The numerous difficult decisions that government agencies must make to fairly use and allocate natural resources provides ample opportunity for interdisciplinary teams of natural and social scientists to improve methods for quantifying changes in ecosystem services and their effects on human well-being. This framework is offered with the intent of promoting the success of such teams as they support managers in evaluating the equivalency of ecosystem service offsets and trades, establishing restoration and preservation priorities, and more generally, in developing environmental policy that effectively balances multiple perspectives.  相似文献   
886.
Biological invasions occur worldwide, and have been the object of ecological and socio-economic research for decades. However, the manner in which different stakeholder groups identify the problems associated with invasive species and confront invasive species management under different policies remains poorly understood. In this study, we conducted an econometric analysis of the social factors influencing willingness to pay for invasive alien species management under two different regimes: eradication and prevention in the Doñana Natural Protected Area (SW Spain). Controlling for the participation of local residents, tourists and conservationists, email and face-to-face questionnaires were conducted. Results indicated that respondents were more willing to pay for eradication than prevention; and public support for invasive alien species management was influenced by an individual’s knowledge and perception of invasive alien species, active interest in nature, and socio-demographic attributes. We concluded that invasive alien species management research should confront the challenges to engage stakeholders and accept any tradeoffs necessary to modify different conservation policies to ensure effective management is implemented. Finally, our willingness to pay estimates suggest the Department of Environment of Andalusian Government has suitable social support to meet the budgetary expenditures required for invasive alien species plans and adequate resources to justify an increase in the invasive alien species management budget.  相似文献   
887.
Anthropogenic impairment of water bodies represents a global environmental concern, yet few attempts have successfully linked fish performance to thermal habitat suitability and fewer have distinguished co-varying water quality constraints. We interfaced fish bioenergetics, field measurements, and Thermal Remote Imaging to generate a spatially-explicit, high-resolution surface of fish growth potential, and next employed a structured hypothesis to detect relationships among measures of fish performance and co-varying water quality constraints. Our thermal surface of fish performance captured the amount and spatial-temporal arrangement of thermally-suitable habitat for three focal species in an extremely heterogeneous reservoir, but interpretation of this pattern was initially confounded by seasonal covariation of water residence time and water quality. Subsequent path analysis revealed that in terms of seasonal patterns in growth potential, catfish and walleye responded to temperature, positively and negatively, respectively; crappie and walleye responded to eutrophy (negatively). At the high eutrophy levels observed in this system, some desired fishes appear to suffer from excessive cultural eutrophication within the context of elevated temperatures whereas others appear to be largely unaffected or even enhanced. Our overall findings do not lead to the conclusion that this system is degraded by pollution; however, they do highlight the need to use a sensitive focal species in the process of determining allowable nutrient loading and as integrators of habitat suitability across multiple spatial and temporal scales. We provide an integrated approach useful for quantifying fish growth potential and identifying water quality constraints on fish performance at spatial scales appropriate for whole-system management.  相似文献   
888.
Knowledge of forest fuels and their potential fire behavior across a landscape is essential in fire management. Four customized fire behavior fuel models that differed significantly in fuels characteristics and environmental conditions were identified using hierarchical cluster analysis based on fuels data collected across a boreal forest landscape in northeastern China. Fuel model I represented the dense and heavily branched Pinus pumila shrubland which has significant fine live woody fuels. These forests occur mainly at higher mountain elevations. Fuel model II is applicable to forests dominated by Betula platyphylla and Populus davidiana occurring in native forests on hill slopes or at low mountain elevations. This fuel model was differentiated from other fuel models by higher herbaceous cover and lower fine live woody loading. The primary coniferous forests dominated by Larix gmelini and Pinus sylvestris L. var. mongolica were classified as fuel model III and fuel model IV. Those fuel models differed from one another in average cover and height of understory shrub and herbaceous layers as well as in aspect. The potential fire behavior for each fuel model was simulated with the BehavePlus5.0 fire behavior prediction system. The simulation results indicated that the Pinus pumila shrubland fuels had the most severe fire behavior for the 97th percentile weather condition, and had the least severe fire behavior under 90th percentile weather condition. Fuel model II presented the least severe fire potential across weather conditions. Fuel model IV resulted in greater fire severity than Fuel model III across the two weather scenarios that were examined.  相似文献   
889.
Overview of Contemporary Issues of Forest Research and Management in China   总被引:1,自引:0,他引:1  
With 207 million ha of forest covering 22% of its land area, China ranks fifth in the world in forest area. Rapid economic growth, climate change, and forest disturbances pose new, complex challenges for forest research and management. Progress in meeting these challenges is relevant beyond China, because China’s forests represent 34% of Asia’s forests and 5% of the worlds’ forests. To provide a broader understanding of these management challenges and of research and policies that address them, we organized this special issue on contemporary forest research and management issues in China. At the national level, papers review major forest types and the evolution of sustainable forestry, the development of China’s forest-certification efforts, the establishment of a forest inventory system, and achievements and challenges in insect pest control in China. Papers focused on Northern China address historical, social, and political factors that have shaped the region’s forests; the use of forest landscape models to assess how forest management can achieve multiple objectives; and analysis and modeling of fuels and fire behavior. Papers addressing Central and South China describe the “Grain for Green” program, which converts low productivity cropland to grassland and woodland to address erosion and soil carbon sequestration; the potential effects of climate change on CO2 efflux and soil respiration; and relationships between climate and net primary productivity. China shares many forest management and research issues with other countries, but in other cases China’s capacity to respond to forest management challenges is unique and bears watching by the rest of the world.  相似文献   
890.
The diversity of plant resources in the Brazilian semi-arid region is being compromised by practices related to agriculture, pastures, and forest harvesting, especially in areas containing Caatinga vegetation (xeric shrublands and thorn forests). The impact of these practices constitutes a series of complex factors involving local issues, creating a need for further scientific studies on the social-environmental dynamics of natural resource use. Through participatory methods, the present study analyzed people’s representations about local environmental change processes in the Brazilian semi-arid region, taking into consideration local production systems, natural resources, and their importance. Environmental historical graphs were developed with nine local families to analyze landscape changes with regard to cultivated areas and pastures, and their relationship with the availability of native vegetation. Punctuation exercises were performed to observe the importance of each unit that supplied native and cultivated resources. The availability of native resources in the environment is subject to stability, as observed by a majority of the local families. The role of the production units (crops and pastures) was emphasized by most families in the study, especially because of the need for products for subsistence needs and income generation. The current decline of such practices is a consequence of an exodus of field workers and also relates to the conservation of native species that otherwise would have been deforested in favor of agricultural practices.  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