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   219篇
  免费   7篇
  国内免费   3篇
安全科学   28篇
废物处理   8篇
环保管理   60篇
综合类   39篇
基础理论   48篇
污染及防治   7篇
评价与监测   4篇
社会与环境   33篇
灾害及防治   2篇
  2023年   1篇
  2022年   4篇
  2021年   4篇
  2020年   4篇
  2019年   1篇
  2018年   1篇
  2017年   9篇
  2016年   6篇
  2015年   2篇
  2014年   9篇
  2013年   15篇
  2012年   10篇
  2011年   6篇
  2010年   5篇
  2009年   11篇
  2008年   10篇
  2007年   8篇
  2006年   15篇
  2005年   14篇
  2004年   18篇
  2003年   12篇
  2002年   14篇
  2001年   14篇
  2000年   8篇
  1999年   4篇
  1997年   5篇
  1995年   1篇
  1994年   2篇
  1993年   7篇
  1992年   1篇
  1991年   3篇
  1988年   2篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
排序方式: 共有229条查询结果,搜索用时 15 毫秒
61.
林业产业集群竞争力研究   总被引:2,自引:0,他引:2  
林业产业集群竞争力的定量评价是林业产业竞争力水平分析和政策制定的重要基础。GEM模型是当前产业集群竞争力评价研究中最具影响力的模型,本文以GEM模型为基础,考虑了林业产业近年来受到政策和社会因素的重要影响,提出了将政策环境和社会环境作为第四个因素对而对GEM模型做出拓展,构建GEMS模型,以适用于林业产业集群竞争力的评价。在此基础上,本文建立了林业产业集群竞争力的GEMS评价指标体系,提出了指标赋值标准,并且在量化过程中提出了最终GEMS得分的评价标准。运用GEMS模型及指标体系可以对林业产业竞争力水平的衡量以及类似产业间的比较,并据此做出合理的应对措施。  相似文献   
62.
简述了企业应急救援体系建设的内容、推动企业安全生产"三要素"的建设和生产现场的安全管理。提出在林业这个特定的范畴内做好安全工作要"关口前移,重心下移"的观点,并如何落实。  相似文献   
63.
This article deals with the visual quality of Mediterranean vegetation groups in northern Israel, the public's preference of these groups as a visual resource, and the policy options for their management. The study is based on a sample of 44 Mediterranean vegetation groups and three population groups of local residents, who were interviewed using a questionnaire and photographs of the vegetation groups. The results of the research showed that plant classification methods based on flora composition, habitat, and external appearance were found to be suitable for visual plant classification and for the evaluation of visual preference of vegetation groups by the interviewed public. The vegetation groups of planted pine forests and olive groves, characterizing a cultured vegetation landscape, were preferred over typical Mediterranean landscapes such as scrub and grassed scrub. The researchers noted a marked difference between the two products of vegetation management policy, one that proposes the conservation and restoration of the variety of native Mediterranean vegetation landscape, and a second that advanced the development of the cultured landscape of planted olive groves and pines forests, which were highly preferred by the public. The authors suggested the development of an integrated vegetation management policy that would combine both needs and thus reduce the gap between the policy proposed by planners and the local population's visual preference.  相似文献   
64.
Urban Hong Kong is covered by high building, road, and population densities. Its urban morphology is inherently not conducive to extensive or high-grade greening. Recent renewal of old areas has squeezed out some limited interstitial plantable space, although in new development areas modest spaces have been earmarked for greenery. The study aims at evaluating the major constraints to urban trees and their companion urban soil envelopes and at providing specific recommendations to improve tree management in the city. The analysis covers the above-ground confinements that dampen tree performance, the less tangible but rather difficult institutional restrictions that impose a somewhat unnecessary lid on tree planting, the multiplicity of players and stakeholders involved in urban-tree management that militates against coordination and cooperation, the widespread occupation of underground space by utility lines often to the exclusion of trees, and the extremely poor quality of urban soils that are often used without amelioration to support tree growth. The management recommendations furnish practical suggestions and hints to improve the short- and long-term welfare of trees in terms of quality, quantity, and spatial distribution. The conclusion enumerates some concrete measures for consideration by decision-makers to upgrade the city's greenery to close the gap between science and policy.  相似文献   
65.
Assisted colonization of vascular plants is considered by many ecologists an important tool to preserve biodiversity threatened by climate change. I argue that assisted colonization may have negative consequences in arctic‐alpine and boreal regions. The observed slow movement of plants toward the north has been an argument for assisted colonization. However, these range shifts may be slow because for many plants microclimatic warming (ignored by advocates of assisted colonization) has been smaller than macroclimatic warming. Arctic‐alpine and boreal plants may have limited possibilities to disperse farther north or to higher elevations. I suggest that arctic‐alpine species are more likely to be driven to extinction because of competitive exclusion by southern species than by increasing temperatures. If so, the future existence of arctic‐alpine and boreal flora may depend on delaying or preventing the migration of plants toward the north to allow northern species to evolve to survive in a warmer climate. In the arctic‐alpine region, preventing the dispersal of trees and shrubs may be the most important method to mitigate the negative effects of climate change. The purported conservation benefits of assisted colonization should not be used to promote the migration of invasive species by forestry.  相似文献   
66.
The natural range of variation of ecosystems provides reference conditions for sustainable management and biodiversity conservation. We review how the understanding of natural reference conditions of boreal forests in northern Europe has changed from earlier perceptions of even-aged dynamics driven by stand-replacing disturbances towards current understanding highlighting the role of non-stand-replacing disturbances and the resultant complex forest dynamics and structures. We show how earlier views and conceptual models of forest disturbance dynamics, including the influential ASIO model, provide estimates of reference conditions that are outside the natural range of variation. Based on a research synthesis, we present a revised forest reference model incorporating the observed complexity of ecosystem dynamics and the prevalence of old forests. Finally, we outline a management model and demonstrate its use in forest ecosystem management and show how regional conservation area needs can be estimated. We conclude that attaining favourable conservation status in northern Europe’s boreal forests requires increasing emphasis on ecosystem management and conservation for old forest characteristics.Electronic supplementary materialThe online version of this article (10.1007/s13280-020-01444-3) contains supplementary material, which is available to authorized users.  相似文献   
67.
An evaluation was conducted to establish the feasibility of a Natural Food Resources Bank (NFRB), in the form of forestry or grassland, to achieve both continuous food production and an accumulation of primary nutrients in living perennial plants. The development of an NFRB protects our living environment from deterioration (especially soil erosion) by increasing the surface coverage of the world's land, even in mountainous areas. Additionally a functioning NFRB enhances food sustainably and security, representing a tangible and renewable food resource production system. Research has identified the prospects of cultivating the NFRB in the form of forestry and also grassland. The review investigated the distinct differences of an NFRB from a range of approaches and discusses the environmental advantage and feasibility of cultivating NFRB. The ability of the NFRB to realize sustainable food resources production for ensuring food security is evaluated in terms of environmental and economical feasibility. A NFRB can attenuate climatic change by increasing CO2 absorption and fixation. It is worth considering the replacement of the annual food production system by the NFRB (especially in steeplands) in environmental law, and replacing the policy of maintaining annual food reserves by the NFRB in food security policy.  相似文献   
68.
万三敏 《资源开发与保护》2013,(12):1270-1272,1297
采用经济重心研究法和变异系数法对河南省林业经济进行了计量分析,发现该省林业经济差异在不断扩大,林业经济重心偏向东南方向,有北移和西移的趋势,对此现象进行了合理的解释.在此基础上,提出了河南省林业经济发展的建议:①转变林业经济增长方式;②豫北山区培育形成特色经济林基地;③豫南山区加强名优经济林种植及深加工;④豫东豫中平原区大力发展速生丰产林和用材林.  相似文献   
69.
A large number of organizations make decisions that directly or indirectly affect tropical forests. The principal constraints that affect these organizations are (1) insufficient funds; (2) insufficient knowledge about the resources and appropriate technologies; (3) institutional, cultural, and political factors; (4) inadequate communication; and (5) contradictory efforts. Opportunities for improving the efficiency and effectiveness of these organizations include (1) increasing cooperation among US government agencies; (2) redirecting international organizations; (3) increasing coordination among organizations; (4) boosting support of nongovernmental organizations and universities; (5) encouraging responsible involvement by private corporations; (6) strengthening existing organizations; and (7) creating new organizations.This article is drawn from US Congress, Office of Technology Assessment (1984), Technologies to Sustain Tropical Forest Resources, chap. 5. Other articles drawn from the OTA report are Hyman (1984a and b) and Hyman and Ross-Sheriff (1984). A larger number of organizations with activities related to tropical forestry are briefly described in the background paper (US Congress, Office of Technology Assessment 1983).  相似文献   
70.
This paper has developed a two-sector model of forestry that gives some insights into the interactions of poverty, land tenure insecurity, economic growth, trade and deforestation in the context of the drylands of Africa. Externally, the model results show that the world demand for non-timber forestry products can lead to a win-win situation whereby both trade and environmental sustainability can be promoted. Monopolistic measures to control the supply of these products, for short-term price gains, are harmful economically and environmentally. By contrast, productivity-raising measures have a favourable impact on both the economy and the environment. Internally, the model results show that the growth of the rest of the economy has driven the economic growth of the forestry sector, but at the same time, its environmental degradation. Poverty and land tenure insecurity also contribute to this degradation. Fortunately, policies promoting basic needs satisfaction and property rights security are shown to be effective in mitigating environmental degradation in the forestry sector. The paper results contribute towards a more sustainable exploitation of forestry.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