全文获取类型
收费全文 | 896篇 |
免费 | 64篇 |
出版年
2024年 | 2篇 |
2023年 | 28篇 |
2022年 | 5篇 |
2021年 | 10篇 |
2020年 | 41篇 |
2019年 | 45篇 |
2018年 | 110篇 |
2017年 | 90篇 |
2016年 | 73篇 |
2015年 | 59篇 |
2014年 | 54篇 |
2013年 | 185篇 |
2012年 | 45篇 |
2011年 | 37篇 |
2010年 | 23篇 |
2009年 | 22篇 |
2008年 | 21篇 |
2007年 | 19篇 |
2006年 | 8篇 |
2005年 | 4篇 |
2004年 | 4篇 |
2003年 | 6篇 |
2002年 | 5篇 |
2001年 | 14篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1957年 | 1篇 |
1952年 | 1篇 |
1950年 | 2篇 |
排序方式: 共有960条查询结果,搜索用时 15 毫秒
91.
A polyphasic tectonic‐fluid system of a fault that involves crystalline and carbonate rocks (Hospital fault, Barcelona Plain) has been inferred from regional to thin section scale observations combined with geochemical analyses. Cathodoluminescence, microprobe analyses and stable isotopy in fracture‐related cements record the circulation of successive alternations of hydrothermal and low‐temperature meteoric fluids linked with three main regional tectonic events. The first event corresponds to the Mesozoic extension, which had two rifting stages, and it is characterized by the independent tectonic activity of two fault segments, namely southern and northern Hospital fault segments. During the Late Permian‐Middle Jurassic rifting, these segments controlled the thickness and distribution of the Triassic sediments. Also, dolomitization was produced in an early stage by Triassic seawater at shallow conditions. During increasing burial, formation of fractures and their dolomite‐related cements took place. Fault activity during the Middle Jurassic–Late Cretaceous rifting was localized in the southern segment, and it was characterized by hydrothermal brines, with temperatures over 180°C, which ascended through this fault segment precipitating quartz, chlorite, and calcite. The second event corresponds to the Paleogene compression (Chattian), which produced exhumation, folding and erosion, favouring the percolation of low‐temperature meteoric fluids which produced the calcitization of the dolostones and of the dolomite cements. The third event is linked with the Neogene extension, where three stages have been identified. During the syn‐rift stage, the southern segment of the Hospital fault grew by tip propagation. In the relay zone, hydrothermal brines with temperature around 140°C upflowed. During the late postrift, the Hospital fault acted as a unique segment and deformation occurred at shallow conditions and under a low‐temperature meteoric regime. Finally, and possibly during the Messinian compression, NW‐SE strike‐slip faults offset the Hospital fault to its current configuration. 相似文献
92.
G. Huelga‐Suarez M. Moldovan M. Suárez Fernández M. Ángel de Blas Cortina J. I. García Alonso 《Archaeometry》2014,56(4):651-664
This paper continues the characterization of the lead isotopic fingerprint of ancient copper mines in the north‐west of Spain. In this work, the lead isotopic compositions found in copper ores from the La Profunda mine are presented. Azurites and malachites sampled from this deposit were subjected to lead isotope analysis by multicollector ICP–MS. The results showed a clear radiogenic lead signature compatible with the presence of uranium‐rich minerals (such as zeunerite) in the same mining complex. Moreover, a rare copper artefact, found in the galleries of the mine during its modern exploitation, was also analysed and showed that local mineral was used for its manufacturing. 相似文献
93.
Åshild Kolås 《Development and change》2014,45(2):308-328
This article examines discourses about grassland degradation in China as expressed by herders, government officials and researchers, presenting findings from fieldwork in Xilinguole League, Inner Mongolia. Recognizing degradation discourse and grassland restoration policies as key sites of political contestation, this study does not try to arrive at the scientific facts about degradation, but rather seeks to illuminate the mechanisms by which grasslands are identified as degraded, and the implementation of policies to restore and protect the grasslands. A key finding is that policy outcomes are widely divergent and difficult to predict. This is not merely due to differences among actors in terms of their interests, access to resources, power, values or knowledge, but as much a result of contradictions and tensions inherent in key policy goals, opening up spaces for local resistance as well as selective policy implementation. This highlights the open‐ended and contested nature of China's environmental state project. 相似文献
94.
Miia Ijäs 《Scandinavian journal of history》2014,39(4):403-424
This article analyses the candidacy of King John III Vasa in the royal elections of Poland-Lithuania in 1573 and 1575. Although the ‘Polish-minded’ policy of John Vasa is commonly known in earlier historiography, Swedish and Finnish historians have not given much attention to John III’s election campaigns in Poland-Lithuania in the 1570s. This article contemplates John III’s candidacy and rejection from the perspective of Poland-Lithuania. The royal elections are analysed as a political decision-making process by the Polish-Lithuanian estates. Thus the article emphasizes the existence of past alternatives and conditions of decision-making in early-modern history. 相似文献
95.
Relying on stochastic frontier analysis we propose a methodology to study the technological characteristics and cost efficiency levels related to the provision of public infrastructure for basic utilities. The methodology assumes a cost minimizing behaviour on the part of public officials when planning the construction of local infrastructure, which is represented by way of a flexible translog cost function. Introducing relevant definitions of scale economies, associated with larger numbers of inhabitants and dwellings, as well as economies of density, brought about by reductions in urban dispersion, we analytically determine the optimal population densities for which average cost is minimized. We illustrate our model with the water cycle sector, including water distribution, sewage collection and cleansing of wastewater, and considering data at the municipality level for the Spanish region of Castilla y León. The obtained results indicate potential cost savings in the form of decreasing average costs, as relevant scale and density economies are present, along with large inefficiency levels. Relevant policy guidelines favouring larger and denser urban sizes are drawn, as the observed cost excess is the result of a general suboptimal urban size in terms of population density, and the negative effects of dispersed settlement patterns. 相似文献
96.
The excavation of Tunel VII, a Yamana site dating to the indigenous/European contact period was part of a long term research project based on the north coast of the Beagle channel (Tierra del Fuego, Argentina). The aim was to evaluate the theory and methodologies and devise an archaeological method that would enable a complete picture of subsistence strategies to be constructed. At Tunel VII (a site with shell middens), we were able to analyse these strategies through 10 successive occupation events on a single location. Archaeozoological analysis of the faunal remains and use-wear analysis of lithic material were used to examine the management of resources. Production and consumption are two very useful concepts, and together they have been used to create a methodology, which, together with spatial analysis using significant variables, has enabled identification of recurrent or significant tendencies in relation to alteration or continuity in subsistence strategies. In the case of Tunel VII, we know that the people who continually occupied the hut were all from the same group. 相似文献
97.
98.
99.
José Luis Hervás Oliver José Albors Garrigós Juan Ignacio Dalmau Porta 《European Planning Studies》2008,16(4):507-520
Classical industrial districts' literature is not focused on the role played by external ties but gives more importance to the local districts' endogenous development. Global value chains connect clusters to other external agents through external linkages and constitute a framework to analyse the complex inter-linkages between clusters and other external agents. In the field of the external ties and the global value chain approach Academia is primarily focused on the ties which link clusters in developing nations to global markets, although global value chains also consider connections between clusters in similar activities and even when both are located in developed nations. Thus, external linkages are mainly performed by multinational enterprise (MNE) affiliates which play fundamental role of knowledge diffusers and absorbers in the process of knowledge exchange throughout global value chains. The work examines the process of knowledge exchange between clusters through external ties using the global value chain approach. For this purpose, empirical work is conducted with 22 face-to-face interviews to provide a case study about a leading cluster in the global ceramic tile industry. Results show that the basic knowledge to successfully compete is locally originated, although it can be complemented with global knowledge learnt or generated in other territories. MNE affiliates bridge structural holes through external ties and reduce knowledge asymmetries within global value chains. External ties on network-based governance chains exist, matter and affect clusters allowing upgrading even between developed nations. 相似文献
100.
María Teresa Fernández‐Aceves 《Gender & history》2008,20(1):161-169
This paper discusses the impact of the conference ‘Las Olvidadas: Gender and Women's History in Post‐Revolutionary Mexico’ that took place at Yale University in May 2001, into my own work on women's political mobilisations. It points out from where I departed and how it changed my perspective from women's history to gender history by focusing on women workers in the tortilla industry, a union cacicazgo (political bossism), civic culture, narratives, cultural memory and female political trajectories after the granting of women's suffrage in 1953 in Jalisco. 相似文献