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   2377篇
  免费   74篇
  2024年   2篇
  2023年   31篇
  2022年   6篇
  2021年   12篇
  2020年   56篇
  2019年   69篇
  2018年   378篇
  2017年   287篇
  2016年   314篇
  2015年   76篇
  2014年   65篇
  2013年   230篇
  2012年   88篇
  2011年   203篇
  2010年   212篇
  2009年   70篇
  2008年   93篇
  2007年   91篇
  2006年   16篇
  2005年   44篇
  2004年   17篇
  2003年   12篇
  2002年   11篇
  2001年   14篇
  2000年   6篇
  1999年   3篇
  1998年   3篇
  1997年   7篇
  1996年   5篇
  1995年   9篇
  1994年   5篇
  1993年   3篇
  1992年   3篇
  1989年   1篇
  1988年   2篇
  1983年   1篇
  1982年   2篇
  1981年   2篇
  1980年   1篇
  1979年   1篇
排序方式: 共有2451条查询结果,搜索用时 31 毫秒
21.
The period comprising the end of the Early Neolithic and the Middle Neolithic, dated broadly within the fifth millennium cal BC, corresponds to an interval that remains largely unknown in the extreme north-western tip of Africa. This situation contrasts with that of the Early Neolithic, a period characterised by the earliest evidence of the diffusion of a productive economy, cultivated plants and domestic animals. The paucity of data for these later phases can be explained in part by the lack of secure contexts and sequences based on radiocarbon datings of short-lived samples. The current study presents the results of the excavations of El-Khil Caves B and C that yield materials allowing re-evaluation of the chronology of a type of ceramic known as Ashakar ware. The study also identifies two traditions in the northern Moroccan Middle Neolithic. The first is heir to the so-called Impressa Mediterranean ware and rooted in the Cardial Neolithic, while the second is characterised by roulette cord impressions, red slip and tunnel lugs and probably rooted in the region of the Sahara, and has no technological precedents in the study area.  相似文献   
22.
The study presents the results of neutron activation analysis (NAA) of contemporary pottery from Tigray Regional State, northern highland Ethiopia. This is the first regional-scale study of ceramic composition of Tigray’s pottery and is part of an ethnoarchaeological study of the material and social contexts of pottery production and consumption in Tigray’s Eastern (Misraqawi), Central (Mehakelegnaw), and North-western (Semien Mi’irabawi) zones. The analysis identifies clear compositional groups with strong regional patterns, an encouraging result for the use of NAA to study Tigray’s ancient pottery trade. Significantly, the study further contributes to discussions of how mutually constituted social identities of potters and consumers affect compositional patterning in the distribution of pottery in market networks.  相似文献   
23.
Four decades have passed since Harlan and Stemler (1976) proposed the eastern Sahelian zone as the most likely center of Sorghum bicolor domestication. Recently, new data on seed impressions on Butana Group pottery, from the fourth millennium BC in the southern Atbai region of the far eastern Sahelian Belt in Africa, show evidence for cultivation activities of sorghum displaying some domestication traits. Pennisetum glaucum may have been undergoing domestication shortly thereafter in the western Sahel, as finds of fully domesticated pearl millet are present in southeastern Mali by the second half of the third millennium BC, and present in eastern Sudan by the early second millennium BC. The dispersal of the latter to India took less than 1000 years according to present data. Here, we review the middle Holocene Sudanese archaeological data for the first time, to situate the origins and spread of these two native summer rainfall cereals in what is proposed to be their eastern Sahelian Sudan gateway to the Red Sea and the Indian Ocean trade.  相似文献   
24.
First visited by westerners in the mid-nineteenth century, Saharan rock art has since received a great deal of attention. The richness and diversity of this region is recognised by the inclusion on the UNESCO World Heritage list of three properties: Tassili-n-Ajjer in Algeria, Tadrart Acacus in Libya, and Ennedi in Chad. The situation in many North African countries now makes this vast region very difficult to access: safety in the field is not guaranteed and few research funds are available. Today, a new generation of African and foreign scientists has no access to rock art sites in the north of the continent and the lack of fieldwork may entail a lack of safeguard and awareness. The growth of digital technologies over the last 15 years has revolutionised methods for recording rock art sites. Digital technologies are also used to mitigate the gap between artworks and accessibility in those countries where turmoil and social instability make fieldwork impossible. However, much of the documentation and most digital recordings of artworks currently available on the Internet lack an archaeological context. Equally, many of these websites barely mention methodological and theoretical aspects. It is also difficult to understand the extent of awareness among local communities in remote areas—sometimes suffering a digital and linguistic divide—and if (and how) they are genuinely able to exploit these digital resources. Here, I collate some examples from different parts of the Sahara illustrating that the recording, management and dissemination of rock art still present highs and lows. I argue that we should share theories and methods within the digital scientific community, with a view to adopting a shared nomenclature and a public thesaurus, making our cataloguing criteria explicit and, finally, developing an ethical code of conduct involving local communities.  相似文献   
25.
26.
This study takes a valuation perspective to study how and where products and innovations are gaining ‘economic significance’ in the contemporary economy. Building on a recent research stream in economic geography and urban and regional studies, it highlights that the economic value of many products is not formed within production systems alone, but relies on co-constructed connections between production and consumption systems, playing out across multiple geographies. It distinguishes between three types of economic valuation pathways – namely technical, experiential and identity-based – which although analytically distinct may actually build and reinforce one another. This approach is empirically illustrated with the case of the surf-related economy in the city of San Sebastian (Basque Country, Spain), which is used to make a broader point about the growing relevance of a valuation approach to understand competitive advantage and economic renewal in localized production systems.  相似文献   
27.
The objective of this research is to examine in depth the brokerage roles that supporting institutions play in conducting local business and applying technical knowledge inside clusters. We identify three main roles: a coordination role, characterized by the efforts that organizations play in internally coordinating themselves and establishing a shared institutional framework; an interconnector role, where organizations foster communication along the value chain of the industry; and a gatekeeper role that allows organizations to connect cluster members with external networks. Results obtained in the Toy Valley cluster provide evidence that each kind of supporting organization tends to specialize in specific roles, since universities are best for a coordination role with regard to technical knowledge while private organizations are key for vertical communication and coordination. Similar results were obtained when analysing the extra-cluster contacts that these organizations develop as gatekeepers, as they tend to establish specific communication conduits with similar alters in external networks.  相似文献   
28.
In this work, we apply a systemic approach to the analysis of a particular geographic territory, the industrial district. We are particularly interested in analysing the interaction between the productive-technological environment and the scientific environment by an examination of research contracts and patents. Our analysis shows that R&D activity in the Spanish ceramic tile District Innovation System was mainly conducted by suppliers. Final producers’ innovation efforts were related to non-technological aspects and differentiation.  相似文献   
29.
The defining element of island regions is their isolation, the separation of the islands from the mainland; there is an inherent notion of natural border. This condition has preserved ecosystems and protected against outside threats, stimulating ‘coevolution’ between man and the environment, a fundamental ingredient of sustainability. But insularity also means the evident added costs of access to markets which, together with territorial limits and the scarcity of basic resources, especially on small islands, hinders their socioeconomic development. These costs are even greater in the case of outlying islands, which suffer from a ‘double insularity’ in the form of both external and internal borders. For this reason, it is common for governments to establish various forms of support, from tax exemptions to the creation of permanent aid funds, like those implemented by the European Union for the outermost regions. This article discusses these aspects in the case of the Canary Islands, an example of a European outermost island region. The findings show that the support measures have not always been favourable for all the islands.  相似文献   
30.
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