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   2125篇
  免费   235篇
  国内免费   49篇
安全科学   42篇
废物处理   17篇
环保管理   585篇
综合类   349篇
基础理论   1146篇
环境理论   3篇
污染及防治   76篇
评价与监测   45篇
社会与环境   138篇
灾害及防治   8篇
  2023年   67篇
  2022年   58篇
  2021年   85篇
  2020年   79篇
  2019年   76篇
  2018年   75篇
  2017年   83篇
  2016年   90篇
  2015年   104篇
  2014年   96篇
  2013年   129篇
  2012年   79篇
  2011年   125篇
  2010年   137篇
  2009年   138篇
  2008年   133篇
  2007年   141篇
  2006年   99篇
  2005年   90篇
  2004年   72篇
  2003年   33篇
  2002年   39篇
  2001年   48篇
  2000年   39篇
  1999年   25篇
  1998年   25篇
  1997年   23篇
  1996年   29篇
  1995年   26篇
  1994年   20篇
  1993年   21篇
  1992年   12篇
  1991年   9篇
  1990年   6篇
  1989年   8篇
  1988年   10篇
  1987年   13篇
  1986年   5篇
  1985年   4篇
  1984年   4篇
  1983年   8篇
  1982年   9篇
  1981年   8篇
  1980年   7篇
  1979年   4篇
  1978年   6篇
  1973年   1篇
  1972年   1篇
  1971年   5篇
  1968年   1篇
排序方式: 共有2409条查询结果,搜索用时 734 毫秒
241.
Landscapes fulfil a multitude of ecological and social functions. Due to the fact that both traditional and everyday landscapes today face many different threats, regulatory measures have been undertaken in many countries to protect and further sustainable landscape development. They include legislation as well as economic incentives. In recent years, however, it has become clear that just to have a few laws and to spend money on subsidies is not enough. Factors other than legislation are also essential to further the sustainable development of landscapes. One of the basic factors affecting the success or failure of landscape conservation measures is public acceptance of these measures. Our project took this as its starting point. The objective was to determine which conditions and factors influence acceptance positively or negatively. To this end 22 Swiss who are directly affected by nature conservation measures, in particular by mire landscape and dry meadow conservation measures, were interviewed using qualitative interview techniques. It is shown that perception, communication, and possibilities to participate are the most decisive driving factors influencing the formation of a long-lasting acceptance. Furthermore, acceptance may be based mainly on economic criteria, on usefulness, on ecological or even aesthetic aspects. It can be shown that not all of these motivations lead to a long-lasting acceptance. Ecologically based acceptance seems the most promising because it is founded on general convictions. Economic incentives--though important--seem to generate only superficial acceptance and do not seem to be as important as is usually assumed.  相似文献   
242.
Successful biodiversity conservation does not depend on ecologic knowledge alone. Good conservation policies and policy implementation tools are equally important. Moreover, the knowledge, skills, and attitudes of local actors, directly in charge of operations in the field, are a key to successful policy implementation. The connections between policy objectives and their implementation as well as the involvement of local actors’ efforts in implementing policy objectives largely depend on the governance model in use. This article assesses the knowledge of local actors in relation to the biodiversity conservation objectives and tools in Lithuanian forest management. As a main framework for this study, the needs assessment approach was applied. The study used both in-depth open-ended interviews and follow-up telephone interviews. Two state forest enterprises in Lithuania were selected as the study sites. The findings indicate that policy objectives in the field of forest biodiversity conservation and the related tools are well known but not well understood by those in charge of forest biodiversity policy implementation. To improve the situation, a transition toward adaptive learning and participatory governance as a means of facilitating conservation efforts is proposed.  相似文献   
243.
Human agency plays a key role in the processes of biological invasions. This comprises not only the human role in the configuration of driving forces or in the perception of the impacts, but also the conceptualization of alien species themselves as an environmental problem. This paper examines different stakeholders' positions in bioinvasion processes at different scales, and it looks at their relevance for the management of invasive species. It compares two cases: the invasion process of Dreissena polymorpha in the Ebro River in Spain and the case of Hydrilla verticillata in Lake Izabal, Guatemala. Our results are structured according to impacts and to management options. The discussion focuses on the relevance of incorporating the different stakeholders' interests and values in the analysis and management of biological invasions. Although social analysis of stakeholders' positions is necessary in order to foster management actions, it also reveals conflicts on the relevant criteria and on the very definition of invasive species.  相似文献   
244.
为明确兜兰属(Paphiopedilum)宽瓣亚属(Subgenus.Brachypetalum)植物各物种在我国的生存现状与濒危状况,在大量的野外调查和文献、标本数据收集的基础上,对其种群分布、数量、生境特征、市场贸易、受威胁因素、保护现状与保护成效进行统计分析,并依据《IUCN红色名录等级和标准(3.1版)》对该类群的濒危等级进行重新评估.结果表明,野外调查到硬叶兜兰(Paphiopedilum.micranthum)、麻栗坡兜兰(P.malipoense)、杏黄兜兰(P.armeniacum)、白花兜兰(P.emersonii)、巨瓣兜兰(P.bellatulum)、文山兜兰(P.wenshanense)、同色兜兰(P.concolor)7个目标物种,已知分布于我国50个县(市、区),共计194个自然分布点.宽瓣亚属植物在我国水平方向上主要分布于滇东南、黔西南、黔东北、滇西北、桂北与黔南交界处以及桂西北至桂西南等地区;垂直方向上集中分布于中高海拔段(780~1267m),平均海拔997m;在全国大尺度上,该亚属整体呈零散分布,区域小尺度上个体呈聚集生长;其小生境具有高海拔、透水、透气、喜阴、喜钙的特点.市场调查的贸易率为36.67%,贸易价格高低不等,具有较强的随机性;贸易来源主要为野外采挖,占贸易数量的88.32%,具有较强的地域性;贸易方式为现场和线上网络交易,具有较强的灵活性.该类群主要受到采挖和生境退化的威胁,分别占所有分布点的44.85%、29.83%.宽瓣亚属整体就地保率仅为34.53%,保护成效为一般保护;调查的29个保育地中,有20个保育地对该类群累计保育98次,除文山兜兰和绿叶兜兰外,其他7种迁地保护成效被评估为合适.巨瓣兜兰、文山兜兰由原来的濒危(EN)评估为极危(CR);麻栗坡兜兰、白花兜兰、杏黄兜兰评估等级未发生变化,仍为极危(CR);硬叶兜兰和同色兜兰由原来的易危(VU)评估为濒危(EN);德氏兜兰、绿叶兜兰被评为数据缺乏(DD).  相似文献   
245.
南方丘陵山地带土壤保持功能及其经济价值时空变化特征   总被引:2,自引:0,他引:2  
土壤保持是生态系统提供的重要调节服务之一,在区域侵蚀控制以及生态安全的维持方面具有不可替代的作用。以全国主体生态功能区划中"两屏三带"的南方丘陵山地带为研究对象,在遥感和地理信息系统的支持下,以2000、2005和2010年3期生态系统类型数据为主要数据源,运用通用土壤流失方程(Universal Soil Loss Equation, USLE)分析了南方丘陵山地带生态系统土壤保持功能,并对其经济价值进行动态核算。结果表明:10 a间,南方丘陵山地带土壤保持总量呈上升趋势,土壤保持总量上升了76.79×107 t,森林、灌丛和农田生态系统是研究区土壤保持功能的主要贡献者,总贡献率3个年份分别为82.29%、82.59%和80.58%,不同生态系统土壤保持总量排序为森林> 灌丛> 农田> 草地> 湿地> 人工表面> 稀疏地,土壤保持能力排序为湿地> 草地> 灌丛> 森林> 农田> 人工表面> 稀疏地;10 a间,研究区土壤保持功能总经济价值增加了270.34×108元,总经济价值中以保持土壤肥力价值为主;土壤保持功能经济价值的变化以轻微增加为主,其呈现增加的区域面积和价值增幅大于经济价值减少的区域面积和价值减幅。在对该区域生态系统进行保护的基础上,因地制宜地合理增加植被盖度对防治土壤侵蚀、保持土壤养分可以起到良好效果。  相似文献   
246.
Water is a natural resource key to human and environmental health. China has suffered serious contamination of its water sources in the past decade, which has had severe consequences on the water supplies of millions of residents. Frequent polluting accidents and the amount of wastewater discharged have caused concern for the safety of drinking water. Fortunately, those at various levels of government have realized the importance of protecting the sources of drinking water and confirmed a list of 175 nationally important sources. Measures have also been adopted to control water pollution, including infrastructural, physical, chemical, ecological, administrative, and legal measures. While helpful, some areas in need of more attention are rural water, groundwater, agricultural pollution, and domestic sewage. Based on the lessons learned from experiences in developed countries, we offer some suggestions for improving, inter alia, funding, legal construction, management, and awareness‐raising, as well as present proposals for the future protection of our sources of drinking water. Future work should focus on water quality standards, quantitative research, high technology and legislation.  相似文献   
247.
Abstract: In a time of increasing urbanization, the fundamental value of conserving urban biodiversity remains controversial. How much of a fixed budget should be spent on conservation in urban versus nonurban landscapes? The answer should depend on the goals that drive our conservation actions, yet proponents of urban conservation often fail to specify the motivation for protecting urban biodiversity. This is an important shortcoming on several fronts, including a missed opportunity to make a stronger appeal to those who believe conservation biology should focus exclusively on more natural, wilder landscapes. We argue that urban areas do offer an important venue for conservation biology, but that we must become better at choosing and articulating our goals. We explored seven possible motivations for urban biodiversity conservation: preserving local biodiversity, creating stepping stones to nonurban habitat, understanding and facilitating responses to environmental change, conducting environmental education, providing ecosystem services, fulfilling ethical responsibilities, and improving human well‐being. To attain all these goals, challenges must be faced that are common to the urban environment, such as localized pollution, disruption of ecosystem structure, and limited availability of land. There are, however, also challenges specific only to particular goals, meaning that different goals will require different approaches and actions. This highlights the importance of specifying the motivations behind urban biodiversity conservation. If the goals are unknown, progress cannot be assessed.  相似文献   
248.
Abstract Spatial prioritization techniques are applied in conservation‐planning initiatives to allocate conservation resources. Although typically they are based on ecological data (e.g., species, habitats, ecological processes), increasingly they also include nonecological data, mostly on the vulnerability of valued features and economic costs of implementation. Nevertheless, the effectiveness of conservation actions implemented through conservation‐planning initiatives is a function of the human and social dimensions of social‐ecological systems, such as stakeholders’ willingness and capacity to participate. We assessed human and social factors hypothesized to define opportunities for implementing effective conservation action by individual land managers (those responsible for making day‐to‐day decisions on land use) and mapped these to schedule implementation of a private land conservation program. We surveyed 48 land managers who owned 301 land parcels in the Makana Municipality of the Eastern Cape province in South Africa. Psychometric statistical and cluster analyses were applied to the interview data so as to map human and social factors of conservation opportunity across a landscape of regional conservation importance. Four groups of landowners were identified, in rank order, for a phased implementation process. Furthermore, using psychometric statistical techniques, we reduced the number of interview questions from 165 to 45, which is a preliminary step toward developing surrogates for human and social factors that can be developed rapidly and complemented with measures of conservation value, vulnerability, and economic cost to more‐effectively schedule conservation actions. This work provides conservation and land management professionals direction on where and how implementation of local‐scale conservation should be undertaken to ensure it is feasible.  相似文献   
249.
Abstract: Indigenous people inhabit approximately 85% of areas designated for biodiversity conservation worldwide. They also continue to struggle for recognition and preservation of cultural identities, lifestyles, and livelihoods—a struggle contingent on control and protection of traditional lands and associated natural resources (hereafter, self‐determination). Indigenous lands and the biodiversity they support are increasingly threatened because of human population growth and per capita consumption. Application of the Endangered Species Act (ESA) to tribal lands in the United States provides a rich example of the articulation between biodiversity conservation and indigenous peoples' struggle for self‐determination. We found a paradoxical relationship whereby tribal governments are simultaneously and contradictorily sovereign nations; yet their communities depend on the U.S. government for protection through the federal‐trust doctrine. The unique legal status of tribal lands, their importance for conserving federally protected species, and federal environmental regulations' failure to define applicability to tribal lands creates conflict between tribal sovereignty, self‐determination, and constitutional authority. We reviewed Secretarial Order 3206, the U.S. policy on “American Indian tribal rights, federal–tribal trust responsibilities, and the ESA,” and evaluated how it influences ESA implementation on tribal lands. We found improved biodiversity conservation and tribal self‐determination requires revision of the fiduciary relationship between the federal government and the tribes to establish clear, legal definitions regarding land rights, applicability of environmental laws, and financial responsibilities. Such actions will allow provision of adequate funding and training to tribal leaders and resource managers, government agency personnel responsible for biodiversity conservation and land management, and environmental policy makers. Increased capacity, cooperation, and knowledge transfer among tribes and conservationists will improve biodiversity conservation and indigenous self‐determination.  相似文献   
250.
Abstract: Successful protection of biodiversity requires increased understanding of the ecological characteristics that predispose some species to endangerment. Theory posits that species with polymorphic or variable coloration should have larger distributions, use more diverse resources, and be less vulnerable to population declines and extinctions, compared with taxa that do not vary in color. We used information from literature on 194 species of Australian frogs to search for associations of coloration mode with ecological variables. In general, species with variable or polymorphic color patterns had larger ranges, used more habitats, were less prone to have a negative population trend, and were estimated as less vulnerable to extinction compared with nonvariable species. An association of variable coloration with lower endangerment was also evident when we controlled statistically for the effects of range size. Nonvariable coloration was not a strong predictor of endangerment, and information on several characteristics is needed to reliably identify and protect species that are prone to decline and may become threatened by extinction in the near future. Analyses based on phylogenetic‐independent contrasts did not support the hypothesis that evolutionary transitions between nonvariable and variable or polymorphic coloration have been accompanied by changes in the ecological variables we examined. Irrefutable demonstration of a role of color pattern variation in amphibian decline and in the dynamics and persistence of populations in general will require a manipulative experimental approach.  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