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   174篇
  免费   7篇
  国内免费   9篇
测绘学   30篇
大气科学   32篇
地球物理   14篇
地质学   49篇
海洋学   23篇
综合类   17篇
自然地理   25篇
  2024年   1篇
  2023年   4篇
  2022年   7篇
  2021年   5篇
  2020年   7篇
  2019年   2篇
  2018年   3篇
  2017年   15篇
  2016年   6篇
  2015年   8篇
  2014年   7篇
  2013年   11篇
  2012年   5篇
  2011年   7篇
  2010年   3篇
  2009年   8篇
  2008年   13篇
  2007年   6篇
  2006年   12篇
  2005年   3篇
  2004年   7篇
  2003年   3篇
  2002年   6篇
  2001年   9篇
  2000年   10篇
  1999年   7篇
  1998年   2篇
  1997年   2篇
  1996年   2篇
  1995年   2篇
  1993年   3篇
  1992年   1篇
  1990年   2篇
  1989年   1篇
排序方式: 共有190条查询结果,搜索用时 968 毫秒
121.
The present and predicted increase in groundwater’s share of human freshwater withdrawals, its unprecedented importance for human activities globally, and the emerging threats from escalated and unplanned use and degradation, especially in the developing countries, point to the need for intensified efforts to cope with the imbalances. Despite these facts, there is little intervention by governments in developing countries. Sufficient knowledge, awareness and understanding of the groundwater resources and their proper management are missing in these countries, as well as in the international community. Links and trends are described, which highlight problem areas, such as water contamination, urbanization, and socio-economic factors related to groundwater management practices. Globalization provides novel opportunities for facilitating the process of acquiring and applying the necessary knowledge and can, and should, be further explored and developed. The likely benefits of this are: increase in convergence of understanding and approaches; the sharing of knowledge; and potentially wide-reaching, lasting, and scale-crossing networks. The international development and research community is in a particularly fortunate position to promote and facilitate such a process, which should go hand in hand with well focused and coordinated “on the ground” tasks, such as local networking, field investigations, capacity building, and advocacy activities.
Karen G. VillholthEmail: Phone: +94-11-278-7404Fax: +94-11-278-6854
  相似文献   
122.
In the debate on urban and regional competitiveness, it has become fashionable to stress the growing importance of creativity for economic development. Especially scientist-consultants with a keen eye for what politicians and business people want to hear have taken centre stage in this discussion. Each city and region in the advanced capitalist world seems to prefer a label as creative city or region, and all look after the same type of industries and try to produce the same set of conditions, while investing in higher education and research institutes, networking and lobbying institutions, and the promotion of spin-off companies. A vast number of leaders and spokesmen of local and regional (quasi) governments believe that a major thing to do is to become more attractive places to live for creative knowledge workers or the ‘creative class’, as it is euphemistically labelled.However, in academia there is a lot of scepticism with regard to the use of these concepts and their meaning for urban and regional competitiveness. Also citizen movements and NGOs, and some political parties, voice their concern about the extent to which policies that apply these concepts and ideas might only benefit an elite of higher educated, well- paid professionals while at the same time these policies might result in decline of other activities and in social polarisation and poverty as well.In this paper we contribute to the critical discussion through a critical appraisal of local experts’ views on developments in seven European city-regions, first with regard to policies towards the development of creative and knowledge-intensive industries; and secondly with regard to the impact the development of ‘creative knowledge regions’ may have in social and other respects. In contrast to the rather homogeneous yet dominant advice to facilitate ‘the creative class’, in this paper we will argue that a range of parameters related to the firms and regional institutional, geographical and historical contexts promote a much more diversified view on urban economic development.  相似文献   
123.
This paper investigates the developing spatial and social division of labor in the Greater Shanghai chemical industry. This industry experienced strong growth after the Asian financial crisis, when policy support was extended beyond “new economy” industries to include traditional manufacturing sectors. Based on a conceptualization that emphasizes the role of producer-user networks and interactive learning as a basis for ongoing innovation and business success, an explorative study was designed to investigate the supplier and customer linkages in different locations of the Greater Shanghai region. The results suggest that inter-firm networks are not extensive and often involve limited producer-user interaction. Important chemical firms in the region concentrate on business with their established international customer basis, use state-controlled distribution channels or rely on intermediaries that act as knowledge brokers. Neither of these practices of market interaction includes intensive information exchange and feedback on products, customer experience and demand changes. As such, these practices do not provide a sound basis for self-sustained growth or innovation in the future. The paper concludes that regional policy needs to support the establishment of combined “bonding” and “bridging” relations between chemical producers and their user industries.  相似文献   
124.
This study examines the key characteristics of successful fisheries learning exchanges (FLEs). FLEs are peer-to-peer gatherings in which fishery stakeholders from different communities freely exchange information and experiences surrounding fisheries challenges and solutions. They are usually organized by fishers, non-governmental organizations and governments and are credited as an integral tool for the diffusion and adoption of fisheries management strategies. Despite their numerous perceived benefits within fisheries conservation and management, little research has been conducted on FLEs. This multiple case study addressed the research question: “What are the key characteristics of successful FLEs?” Success metrics were defined during a workshop on FLEs in 2013. For this study, the authors selected six successful FLEs that were presented during the workshop. Documentation of FLEs and key informant interviews with participants and organizers were used as data. The following key elements of successful FLEs emerged from analyses: (1) a clear guiding purpose and flexible objectives, (2) careful and considered selection of participants with diverse professions and conservation beliefs, (3) a mix of activities including giving presentations, conducting site visits, talking with local fishers, spending time on boats or in the water, and participating in cultural activities, and (4) logistical and financial follow-up support, including information dissemination about what participants learned at the FLE. Based on these results, the authors provide recommendations for conducting successful FLEs.  相似文献   
125.
This paper examines the challenge of knowledge co-production and the implications for learning and adapting in the context of a narwhal co-management in Nunavut, Canada. Knowledge co-production is the collaborative process of bringing a plurality of knowledge sources and types together to address a defined problem and build an integrated or systems-oriented understanding of that problem. The paper considers knowledge co-production by examining five interrelated dimensions: knowledge gathering, sharing, integration, interpretation, and application. Voices of hunters, community representatives, and managers engaged in co-management are highlighted to identify primary challenges and opportunities. The analysis reveals how compartmentalized views of knowledge continue to constrain adaptive and collaborative management. An understanding of knowledge co-production processes, however, may help to overcome the resilience of top-down management approaches.  相似文献   
126.
Gaining support for shark conservation has been extremely difficult due to the negative preconceived notions the general public holds toward sharks. In order to achieve public support for conservation initiatives the factors that will change an individual’s attitude and behavior toward sharks must first be determined. Using structured questionnaire interviews (n=186), indices were created that rated an individual’s knowledge, attitude, and potential behavior toward sharks and shark conservation. Generally public knowledge levels about sharks were low. However, people with more knowledge pertaining specifically about sharks had potential behaviors more supportive of their conservation. Therefore, it would seem that increases in public knowledge on sharks would help gain support for shark conservation. Males, members of environmental groups, and viewers of shark documentaries and “Shark Week” all showed significantly higher levels of knowledge about sharks. The media (such as “Shark Week” ) can play a significant role in promoting conservation, but unfortunately media coverage of sharks has been controversial recently with the airing of several non-factual, fake documentaries. To promote shark conservation the media’s message has to be unbiased, non-sensationalized, and accurate to ensure people are receiving the information necessary to build strong pro-shark conservation behaviors.  相似文献   
127.
Plural valuation is about eliciting the diverse values of nature articulated by different stakeholders in order to inform decision making and thus achieve more equitable and sustainable outcomes. We explore what approaches align with plural valuation on the ground, as well as how different social-ecological contexts play a role in translating plural valuation into decisions and outcomes. Based on a co-constructed analytical approach relying on empirical information from ten cases from the Global South, we find that plural valuation contributes to equitable and sustainable outcomes if the valuation process: 1) is based on participatory value elicitation approaches; 2) is framed with a clear action-oriented purpose; 3) provides space for marginalized stakeholders to articulate their values in ways that can be included in decisions; 4) is used as a tool to identify and help reconcile different cognitive models about human-nature relations; and 5) fosters open communication and collaboration among stakeholders. We also find that power asymmetries can hinder plural valuation. As interest and support for undertaking plural valuation grows, a deeper understanding is needed regarding how it can be adapted to different purposes, approaches, and social-ecological contexts in order to contribute to social equity and sustainability.  相似文献   
128.
We develop the relational economic geographical potential of the incubator and hinge functions of megalopolis incorporating ideas from the literature on regional innovation systems and New Argonaut connections respectively. Empirically, we investigate how China’s Yangtze River Delta (YRD) has incubated but also articulated knowledge interactions at different geographical scales. Drawing upon co-patent data from the World Intellectual Property Organization database, we show that the YRD’s knowledge hinge role has strengthened over time, notably as a result of the role played by economic entities in Shanghai – the YRD’s gateway city. To unpack the YRD’s knowledge hinge role, we use information attached to co-patents to distinguish different channels – multinational enterprises, Chinese domestic enterprises, universities and research institutes, and “New Argonaut” linkages – by which YRD cities have accessed exogenous knowledge at different geographical scales. In conclusion we highlight the value of megalopolis as a meso-scale unit of analysis for relational economic geography.  相似文献   
129.
This paper focuses on a topic barely considered in the literature: how to improve the accuracy of a given Digital Elevation Model (DEM) irrespective of its lineage by identifying its most suspicious values (also denoted here as outliers). Methods tailored to a specific procedure and source (contour maps, remote sensing image, etc.) exist but they are not valid for other cases. This is a problem for both the producer and end user. The results of a comparison of two methods using six DEMs intended to be representative of different landscapes are reported here. Both methods have been applied to each DEM, producing a number of height candidates to be analysed. Assuming that all candidates are wrong, their elevations have been blindly replaced by interpolated heights, simulating the behaviour of the inexperienced user. The improved (or degraded) DEMs are then compared against the ground truth, and updated accuracy figures are calculated. The RMSE can diminish by 2 to 8% of the original value by changing less than 1% of the elevations in the dataset.  相似文献   
130.
This paper proposes a novel rough set approach to discover classification rules in real‐valued spatial data in general and remotely sensed data in particular. A knowledge induction process is formulated to select optimal decision rules with a minimal set of features necessary and sufficient for a remote sensing classification task. The approach first converts a real‐valued or integer‐valued decision system into an interval‐valued information system. A knowledge induction procedure is then formulated to discover all classification rules hidden in the information system. Two real‐life applications are made to verify and substantiate the conceptual arguments. It demonstrates that the proposed approach can effectively discover in remotely sensed data the optimal spectral bands and optimal rule set for a classification task. It is also capable of unraveling critical spectral band(s) discerning certain classes. The framework paves the road for data mining in mixed spatial databases consisting of qualitative and quantitative data.  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