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   232篇
  免费   24篇
  2023年   6篇
  2022年   2篇
  2021年   3篇
  2020年   9篇
  2019年   22篇
  2018年   9篇
  2017年   14篇
  2016年   15篇
  2015年   13篇
  2014年   11篇
  2013年   30篇
  2012年   12篇
  2011年   12篇
  2010年   9篇
  2009年   5篇
  2008年   10篇
  2007年   10篇
  2006年   6篇
  2005年   7篇
  2004年   4篇
  2003年   2篇
  2002年   4篇
  2001年   1篇
  2000年   2篇
  1999年   1篇
  1998年   5篇
  1997年   3篇
  1996年   2篇
  1995年   1篇
  1994年   3篇
  1993年   2篇
  1992年   1篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1987年   2篇
  1986年   1篇
  1984年   1篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1977年   1篇
  1974年   1篇
  1973年   1篇
  1972年   1篇
  1971年   2篇
  1970年   1篇
  1969年   3篇
排序方式: 共有256条查询结果,搜索用时 93 毫秒
21.
In this study, we relax one of the general assumptions in the hub location literature by allowing routed flows between nonhub nodes. In hub networks, different flows are consolidated and routed via collection, interhub, and distribution arcs. Due to consolidation, some flows travel long paths despite closeness of their origin and destination. In this study, we allow direct flows by penalizing by a scalar factor of original cost of transshipment between these arcs. We present mathematical models for median, center, and set covering versions of the problem for single‐ and multi‐allocation cases. We test the models with the CAB and TR data sets. We discuss the properties of established direct connections for different models by using another mathematical model where the number of direct flows is bounded and interpret the effect of changes in problem parameters.  相似文献   
22.
This article studies an early Safavid chronicle, Futuhat-e Shahi by Amini Haravi. In 1521, the founder of the Safavid state, Shah Isma‘il, provided Haravi with a number of veterans from the early days of the Safavid uprising as informants. Their narrative presents an alternative view on the early career of the shah that differs from the dominant version current in modern scholarship. From the perspective of the Futuhat, the rise of the Safavids did not occur as a wild apocalyptic explosion, but was a carefully planned and cautious campaign run by experienced commanders who kept a tight rein on the teenage Shah Isma‘il.  相似文献   
23.
24.
25.
At the beginning of the twentieth century, the retreat of the Ottoman Empire caused a massive scale migration in the Aegean regions. This process was furthered by the Treaty of Lausanne (1923) between the Turkish Republic and Greece. Gradually, more than one million people were formally exchanged under the control of the respective national authorities. This study shows that the predictions made by political authorities regarding the expected adaptation and homogenization based on religious affiliations failed to materialize; instead, the process of migration generated its own unique and autonomous processes derived primarily from cultural aspects and social origins. This research examines the materialization of the migrants’ adaptation practices and the spatial transformations in the built environment at both urban and domestic level, in order to indentify spatial and related social conflicts that arose as a result of socio-cultural mixing through a case study of the Çe?me Peninsula, Turkey. The study concludes that the relationship between social space and the physical environment is intertwined, with spatial transformations based on residents’ home of origin, professions and economic prosperity positioned in a clearly defined hierarchy of meaning.  相似文献   
26.
27.
28.
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   
29.
In metropolitan areas, the changing spatial land-use preferences of the industrial sector are the most important determinants in the forming of the macro-form. Metropolitan areas, especially in developing European and Asian countries, become troubled cities with agglomerations of population and investment as a result of failures to apply satisfactory macro-policies and plans throughout the country. Industrial investments on various scales and the land-use preferences of investors have changed over time. The land preferences of production and headquarters of the manufacturing sectors have become basic determinants in the formation of settlement systems due to the transformations that occur alongside technological, economic and social development. This article examines whether or not the basic land-use criterion of the manufacturing sector changes in small-, medium- and large-scale businesses according to their labour structure, defined through an examination of the sectoral structure and relations of scale. Taking the increasing rate of the Gross National Product of the industrial sector in metropolitan areas in every country into account, and examining the land-use preferences of various industrial sub-sectors and scales will serve as an important input when making new planning decisions. The industrial land-use criterion will be effective in the transformation, reorganization or directing of new focuses for the agglomerated industrial structure, especially in Istanbul, which features both Asian and European metropolitan area characteristics. This article will define the existing industrial structure of the Istanbul metropolitan area; and differences between the various scales of land-use preferences within industrial investments will be presented, based on the findings of two investigations carried out over a 5-year period. Several important criteria for industrial investors seeking to establish themselves in metropolitan areas will be determined in the article.  相似文献   
30.
The Sanandaj-Sirjan zone of Iran is a metamorphic belt consisting of rocks which were metamorphosed under different pressure and temperature conditions and intruded by various plutons ranging in composition from gabbro to granite. The majority of these granitoids formed along the ancient active continental margin of the Neo-Tethyan ocean at the southeastern edge of the central Iranian microplate. Geochronological data published in recent years indicate periodic plutonism lasting from Carboniferous through Mesozoic to late-Paleogene times (from ca. 300 to ca. 35 Ma) with climax activity during the mid- and late-Jurassic. The age constraints for plutonic complexes, such as Siah-Kouh, Kolah-Ghazi, Golpayegan (Muteh), Azna, Aligoodarz, Astaneh, Borujerd, Malayer (Samen), Alvand, Almogholagh, Ghorveh, Saqqez, Marivan, Naqadeh and Urumieh, clearly indicate the periodic nature of magmatism. Therefore, the Sanandaj-Sirjan zone preserves the record of magmatic activity of a complete orogenic cycle related to (1) Permocarboniferous(?) rifting of Gondwana and opening of the Neo-Tethyan ocean, (2) subduction of the oceanic crust, (3) continental collision and (4) post-collision/post-orogenic activities. The formation of the Marivan granitoids, northwestern Sanandaj-Sirjan zone, for which we present U-Pb zircon and titanite ages of ca. 38 Ma, can be related to the collisional and post-collisional stages of this orogenic cycle.  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