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   703篇
  免费   70篇
  2024年   2篇
  2023年   21篇
  2022年   5篇
  2021年   7篇
  2020年   38篇
  2019年   33篇
  2018年   93篇
  2017年   83篇
  2016年   79篇
  2015年   47篇
  2014年   57篇
  2013年   144篇
  2012年   25篇
  2011年   31篇
  2010年   22篇
  2009年   8篇
  2008年   21篇
  2007年   10篇
  2006年   5篇
  2005年   4篇
  2004年   7篇
  2003年   1篇
  2002年   1篇
  2001年   6篇
  2000年   5篇
  1999年   4篇
  1998年   3篇
  1997年   2篇
  1996年   2篇
  1995年   2篇
  1989年   1篇
  1987年   1篇
  1986年   1篇
  1985年   1篇
  1982年   1篇
排序方式: 共有773条查询结果,搜索用时 0 毫秒
691.
This paper examines the evolution of regional innovation policy in Emilia-Romagna and Valencia, two regions with similar economic features that implemented close innovation policies in the 1970s and 1980s. We investigate whether their similarities have led to parallel targets, policy tools and governance developments. We show that innovation policy in both regions suffered from the effects of privatization, budget constraints and changes to manufacturing during the 1990s and we highlight the consequences. Although Emilia-Romagna experienced deeper changes to its innovation policy, privatizations and/or the replacement of public funds promoted commercial approaches and induced market failures in both regions. The worst effects of these policies were the implementation of less-risky innovation projects, the shift towards extra-regional projects and markets, and the favouring of large firms.  相似文献   
692.
The recent increase in business services in terms of both value added and employment has had a positive effect on regional economies, helping them to create a comparative advantage and contributing to the general development of regional productive systems. This heterogeneous set of activities is characterized, among others, by its uneven distribution in the territory. In this paper we aim to identify the key factors that influence the location of business services within the NUTS 2 regions of the European Union. Using a multivariate analytical approach (combining a principal components factor analysis and a multiple linear regression by means of ordinary least squares), four key factors have been identified. In terms of their influence on the location of business services, we can pinpoint the following factors: urban dimension, competitiveness, accessibility and economic dynamism. It was found that business services tend to locate in urban, densely populated and dynamic areas with high levels of competitiveness and easy access.  相似文献   
693.
The process of facilitation aims to solve community problems by encouraging the exploitation of skills through different tools implemented by the facilitator. Facilitation has been analysed in the context of advanced and established groups with well-defined objectives, but not at the start of these groups. This article analyses the facilitation process carried out by the Institute of Community Development over 25 years with four work groups in rural areas of Cuenca, Spain. The leadership role taken on by the facilitator is crucial when it comes to identifying and managing the initial efforts required to start the group work. During the facilitation process, training and information tools are essential. It is also important to see a suitable transfer of roles between the facilitator and the stakeholders as they acquire new skills. This transfer is crucial for the continuity of the group and can cause difficulties if it does not happen.  相似文献   
694.
Extracting cores from a tree using an increment borer has been standard practice in dendrochronological studies for a long time. Although empirical rules exist regarding how many samples to take and which methodology to apply, comparatively few studies provide quantification of the similarity of relative tree-ring-widths (TRW) around the stem circumference. The aim of this study was therefore to precisely measure the similarity of standardised TRWs around the stem circumference and to provide objective suggestions for optimal core sampling of Norway spruce (Picea abies Karst. [L.]) and European beech (Fagus sylvatica L.) growing in Central European temperate forests. A large sample of cross-sectional discs was used from Norway spruce and European beech trees growing on various slopes, at different altitudes and biogeographic regions across the Czech Republic and Slovakia. The similarity of TRWs measured in different coring directions was analysed by testing the relativized TRW around the trunk (rTRW). Comparison of rTRWs revealed no significant differences between coring directions, indicating that the relative increment was the same around the radius. The results also showed the high similarity between the rTRWs to be independent of both slope inclination and altitude. Moreover, the reconstruction of proportional tree diameters and basal areas backward in time from one core sample and one measurement of tree diameter (basal area) at the time of sample extraction is possible with reasonable precision.  相似文献   
695.
696.
697.
The economic boom and subsequent collapse (Hrun) of the mid 2000s had a marked effect on Reykjavík, leaving various half-finished and empty structures with uncertain futures. Although the material culture of the economic collapse has been examined to some degree, the abandoned building sites have not. The Icelandic heritage discourse has so far had very little engagement with twentieth-century materiality and even less with twenty-first-century materiality but this paper contends that these places can nevertheless be seen as heritage. In order to engage with such places, the Icelandic authorized heritage discourse must be significantly broadened.  相似文献   
698.
When in 1945 the Czechoslovak authorities confiscated the estate of the Princes von und zu Liechtenstein, the two countries became involved in a dispute which had not been resolved until recently, at least on a diplomatic level. For several decades, the 1948 Communist coup d'état in Czechoslovakia dashed the hopes of the Liechtenstein family for a restitution of their confiscated assets. However, officials responsible internally admitted that the property confiscation had been questionable in the case of the Liechtenstein family. The court had not confirmed the confiscation until after the Communist coup. However, the Liechtenstein family did not renounce their claims, and after the collapse of the Communist regime in 1989 they brought them up again.  相似文献   
699.
High-gradient streams are localities with the most dynamic activity of geomorphological processes in medium-high mountains. This study of the frequency of floods and debris flows in a selected high-gradient stream in the Moravskoslezské Beskydy Mts was based on a dendrogeomorphic approach. It makes use of the most accurate methods applied in the dating of historic geomorphological processes. Individual events were reconstructed on the basis of the dating of various growth disturbances displayed in 99 samples taken from 56 predominantly broad-leaved trees.  相似文献   
700.
This paper examines an alternative approach to previously proposed models of prehistoric exchange such as the law of monotonic decrement or the down-the-line exchange model developed by Renfrew (Proceedings of the Prehistoric Society 34: 319–331, 1968, Renfrew 1977) to explain the distribution of obsidian across the Near East during the Neolithic period. Renfrew’s down-the-line model, which results in a very regular and clustered network, does not permit the circulation of obsidian to regions of the Near East that are further than 300 km from the source zones, as is shown in the archaeological data available. Obsidian exchange is a complex system where multiple factors interact and evolve in time and space. We therefore explore Agent-Based Modelling (ABM) so as to get a better understanding of complex networks. ABM simulations of an exchange network where some agents (villages) are allowed to attain long-distance exchange partners through correlated random walks are carried out. These simulations show what variables (population density, degree of collaboration between villages…) are relevant for the transfer of obsidian over long distances. Moreover, they show that a type of small-world exchange network could explain the breadth of obsidian distribution (up to 800 km from source) during the Near Eastern Neolithic.  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