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   562篇
  免费   16篇
  国内免费   33篇
测绘学   26篇
大气科学   114篇
地球物理   30篇
地质学   188篇
海洋学   104篇
天文学   26篇
综合类   29篇
自然地理   94篇
  2023年   8篇
  2022年   12篇
  2021年   16篇
  2020年   13篇
  2019年   14篇
  2018年   9篇
  2017年   52篇
  2016年   31篇
  2015年   47篇
  2014年   31篇
  2013年   48篇
  2012年   17篇
  2011年   30篇
  2010年   16篇
  2009年   23篇
  2008年   25篇
  2007年   25篇
  2006年   19篇
  2005年   24篇
  2004年   12篇
  2003年   22篇
  2002年   19篇
  2001年   10篇
  2000年   16篇
  1999年   12篇
  1998年   12篇
  1997年   6篇
  1996年   5篇
  1995年   6篇
  1994年   7篇
  1993年   3篇
  1992年   2篇
  1991年   6篇
  1990年   2篇
  1989年   3篇
  1988年   5篇
  1987年   1篇
  1985年   2篇
排序方式: 共有611条查询结果,搜索用时 31 毫秒
141.
Vertical chain collaboration is a strategy for customers’ value creation. However, Dutch fishermen are hardly participating in integrated value chains. While supply chain literature describes factors that contribute to successful chain partnerships, scarce research has been done on the dynamics of the sociocultural context for chain collaboration.In 10 semi-structured interviews, representatives of supply chain parties were asked for their perceptions on chain collaboration, trust, and the role of the local community. The interviews were directed at obtaining so-called ‘tacit’ knowledge, the non-spoken codified truths of social networks. Without generalizing, this research provides benchmarks to monitor how the different domains, laid out in this study, impact chain collaboration: community values, network participation and company competences. An overview is given of socio-economic factors blocking and enhancing chain collaboration at company and community level. Factors such as the strong bonding of family with business in tightly knit networks, a high level of social control, entrepreneurial autonomy, and loyalty as community norm hamper collaboration within the supply chain.Respondents’ discourse demonstrates that cultural codes and identity form the very core of the entrepreneur, driving rather than ‘embedding’ economic behavior. Kinship, religion and peer pressure determine ‘windows on the world’ when engaging in chain collaboration. Consequently, any analysis of economics that does not integrate sociological and psychological methodology is flawed from the outset.  相似文献   
142.
机载小光斑Li DAR是近年来遥感领域的新兴技术,它对回波脉冲进行全数字化的记录,通过分解返回波形能够得到更加丰富的信息。针对传统LM波形分解算法容易陷入局部最优的问题,引入改进LM模型,采用信赖域技巧使得参数解全局收敛。实验证明,该方法相比传统LM能够得到更加可靠的波形分解结果,并且对城区、郊区和山地区域适应性好,具有较强实用价值。  相似文献   
143.
China is home to nearly half of the world’s 50,000 large dams, which provide irrigation, flood protection, and hydroelectricity. Most of these projects involve substantial population displacement, which can disrupt social capital, the webs of interdependence and support that community members maintain with one another through relationships of trust and reciprocity. We use new empirical evidence to examine the association between dam-induced displacement and social capital in China and interpret our findings in the context of social–ecological resilience theory. Our focus is on agricultural households on the Upper Mekong River, where four large hydropower dams have been constructed over the past twenty years.Our broad finding is that resettlement is associated with diminished social capital, as measured by two key indicators: inter-household exchange of financial resources, and inter-household exchange of agricultural labor. These effects differ across the four dam sites in the study based on local economic conditions and changes in resettlement policy. We find that population resettlement is associated with markedly lower levels of agricultural labor exchange. In an economically under-developed setting, this reduces the depth and breadth of social support that agricultural households rely on to produce crops for subsistence and income. This in turn diminishes social–ecological resilience because social capital is a key factor that helps agricultural or resource-dependent communities manage risk and adapt to changes and stressors.We consider the policy implications of our findings in the context of scientific and industry efforts to minimize social harm, promote economic vitality, and improve the sustainability of hydropower as a form of renewable energy.  相似文献   
144.
Scholars overwhelmingly adopt the case study method when analyzing causal conditions inducing anti-dam-protests. We have carried out the first medium-N-study on this topic analyzing public opposition to 12 dam projects in Asia. For this purpose, we employ a fuzzy-set Qualitative Comparative Analysis (QCA) which is based on a thorough review of scholarly writings and press reports on the dam projects at question as well as an online survey and semi-structured interviews. We identify two causal recipes sufficient for the emergence of significant anti-dam-protests. First, lacking social safeguards in combination with the presence of political opportunity structures and higher levels of development are sufficient for significant anti-dam-protests to emerge. Second, lacking social safeguards in combination with rampant corruption and environmental risk induce these protests. Current scholarly literature particuarly emphasizes political opportunity structures and development as causal conditions inducing significant protests. Our findings build on this literature to highlight the importance of project-specific conditions.  相似文献   
145.
Research on vulnerability and adaptation in social-ecological systems (SES) has largely centered on climate change and associated biophysical stressors. Key implications of this are twofold. First, there has been limited engagement with the impacts of social drivers of change on communities and linked SES. Second, the focus on climate effects often assumes slower drivers of change and fails to differentiate the implications of change occurring at different timescales. This has resulted in a body of SES scholarship that is under-theorized in terms of how communities experience and respond to fast versus slow change. Yet, social and economic processes at global scales increasingly emerge as ‘shocks’ for local systems, driving rapid and often surprising forms of change distinct from and yet interacting with the impacts of slow, ongoing ‘trends’. This research seeks to understand the nature and impacts of social shocks as opposed to or in concert with trends through the lens of a qualitative case study of a coastal community in Mexico, where demand from international seafood markets has spurred rapid development of a sea cucumber fishery. Specifically, we examined what different social-ecological changes are being experienced by the community, how the impacts of the sea cucumber fishery are distinct from and interacting with slower ongoing trends and how these processes are affecting system vulnerability, adaptations and adaptive capacity. We begin by proposing a novel framework for conceptualizing impacts on social systems, as comprised of structures, functions, and feedbacks. Our results illustrate how the rapid-onset of this fishery has driven dramatic changes in the community. New challenges such as the ‘gold-rush-style’ arrival of new actors, money, and livelihoods, the rapid over-exploitation of fish stocks, and increases in poaching and armed violence have emerged, exacerbating pressures from ongoing trends in immigration, overfishing and tourism development. We argue that there is a need to better understand and differentiate the social and ecological implications of shocks, which present novel challenges for the vulnerability and adaptive capacity of communities and the sustainability of marine ecosystems.  相似文献   
146.
Wildfires cause different impacts, depending on the conditions and resilience level of the exposed communities. Wildfire occurrence in mainland Portugal was assessed with regard to socioeconomic and demographic parameters, to identify the most distinctive conditions of fire-affected areas, without implying the existence of causal relationships. The latest population and agriculture census data were used to retrieve conditions at the civil parish level, regarding demographic patterns, social and labor conditions, physical structures and agricultural activities. To identify differences between parishes, two groups were created with the communities that showed the highest and lowest 20% of wildfire incidence between 2007 and 2014, separately for density of fire events and for burned area. A stepwise approach based on classification trees and random Forest methods was applied to identify the best discriminant variables between the groups. First, irrelevant variables were removed by an interactive process based on misclassification rates. The second step used random Forest analysis to the remaining variables to evaluate their importance in distinguishing the groups. In the final step, cluster analysis was applied to test the correspondence between the clusters created with the selected variables and the initial groups. Results showed that parishes with higher fire density have higher population density, higher proportion of young and educated people, larger families and more overcrowded buildings. On the contrary, parishes with larger burned area are less populated, less attractive to foreigners, have a higher proportion of elderly people, more degraded housing conditions and agricultural activities, visible in the density of sheep and goat and pastures, are still relevant. The cluster analysis demonstrated a better performance of the model for wildfire density, revealing a strong association with socioeconomic dynamics with an agreement above 0.85, much higher than for burned areas which is 0.29. Overall, the spatial distribution of wildfire impacts is framed by societal settings and particular conditions must be further understood to improve the coping capacity of affected communities.  相似文献   
147.
Numerical modeling of extreme sea levels associated with tropical cyclones in the Indian seas has been confined to the northern part of the Bay of Bengal (north of Tamil Nadu). However, limited attempts have been made for modeling of surges along the Tamil Nadu and Sri Lankan coasts. Although, very rarely, cyclones form south of 10°N, there are some instances of severe cyclonic storms hitting these areas and causing widespread destruction to life and property. Keeping this in view, a suitable location-specific, high-resolution, numerical model has been developed for the prediction of storm surges in these regions with a grid resolution of 3 km. Using the model, numerical experiments are performed to simulate the storm surge associated with the 1964 Rameswaram cyclone, the 1978 Batticaloa cyclone, the 1992 Tuticorin cyclone, the 1993 Karaikal cyclone, and the 1994 Madras cyclone. During the years 1964, 1978, and 1992, the cyclones struck both Sri Lanka and Tamil Nadu coasts, while in 1993 and 1994, the cyclones struck only the Tamil Nadu coast. It is found that the computed sea surface elevations are in close agreement with the available observations/estimates.  相似文献   
148.
Small-scale fisheries and the communities they support are often given the protection of designated fishing zones from which non-artisanal vessels are excluded. This paper looks at one example of this approach, the trawl ban introduced in the Gulf of Castellammare (NW Sicily), focussing on the economic sustainability of the artisanal fishery currently operating within the protected area. The consequences of lifting the trawl ban and how far this would jeopardise the sustainability of the artisanal fishery are explored via an analysis of the financial viability of trammel net vessels under alternative assumptions concerning catch rates. The paper also investigates fishermen's attitudes towards the trawl ban and their predisposition either to remain in the fishery or to quit in the event of the ban being removed.  相似文献   
149.
Svein Jentoft   《Marine Policy》2006,30(6):671-680
This paper has two main sources of inspiration. Firstly, building on Flyvbjerg's “Making Social Science Matter”[Flyvbjerg B. Making social science matter: why social inquiry fails and how it can succeed again. Cambridge: Cambridge University Press; 2003], I argue that the contribution of the social sciences to fisheries resource management must essentially be “phronetic” (after Aristotle's phronesis, i.e. practical wisdom), in contrast to the “scientific” (Aristotle: episteme) contribution of the natural sciences. Secondly, inspired by the recent publication “Fish for Life: Interactive Governance for Fisheries” [Kooiman J, Jentoft S, Pullin R, Bavinck M, editors. Fish for life: interactive governance for fisheries. Amsterdam: Amsterdam University Press; 2005], I hold that phronesis is basically what the notion of governance adds to management. Governance is the broader concept, inviting a more reflexive, deliberative and value-rational methodology than the instrumental, means-end oriented management concept. I claim that for interdisciplinarity to work in fisheries it is essential to recognize the fundamental methodological differences that exist between the social and natural sciences.  相似文献   
150.
This article contributes to the understanding of the changes in distribution and total area of mangrove forests along the mainland Tanzania coast over the past decade. Mangroves are recognized as critical coastal habitat requiring protection and special attention. The Tanzania coastline forms a suitable habitat for establishment of mangrove forests. Mangrove forests are distributed from Tanga in the north to Mtwara in the south covering approximately 109,593 hectares from 1988-1990 and about 108,138 hectares in 2000. The largest continuous mangrove stands are found in the districts of Rufiji, Kilwa, Tanga-Muheza, and Mtwara. Comparison of data between these two time periods shows that the geographic coverage of mangroves has no dramatic change in the past decade. The Tanzania Mangrove Management Project and other closely related programs and efforts pertaining to mangrove conservation contribute to direct restoration and natural regeneration of mangroves. This study documents the changes of mangroves and demonstrates that remote sensing and GIS offer important data and tools in the advancement of coastal resource management and ecosystem monitoring. Application of geographic information technologies is critical for improved coastal resources management and decision making for sustainable development in Tanzania.  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