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   3783篇
  免费   121篇
  2020年   42篇
  2019年   49篇
  2018年   80篇
  2017年   80篇
  2016年   106篇
  2015年   74篇
  2014年   67篇
  2013年   1069篇
  2012年   97篇
  2011年   127篇
  2010年   108篇
  2009年   88篇
  2008年   94篇
  2007年   64篇
  2006年   63篇
  2005年   62篇
  2004年   55篇
  2003年   30篇
  2002年   38篇
  2001年   60篇
  2000年   49篇
  1999年   56篇
  1998年   38篇
  1997年   43篇
  1996年   38篇
  1995年   30篇
  1994年   37篇
  1993年   42篇
  1992年   44篇
  1991年   35篇
  1990年   29篇
  1989年   36篇
  1988年   34篇
  1987年   45篇
  1986年   30篇
  1985年   48篇
  1984年   37篇
  1983年   65篇
  1982年   48篇
  1981年   55篇
  1980年   54篇
  1979年   38篇
  1978年   40篇
  1977年   58篇
  1976年   42篇
  1975年   44篇
  1974年   31篇
  1973年   29篇
  1972年   26篇
  1971年   33篇
排序方式: 共有3904条查询结果,搜索用时 31 毫秒
971.
A pile-dwelling settlement, dated to the final Bronze–early Iron Age (XII–XI century BC), was excavated at Stagno, near Leghorn (Tuscany, Italy). The site presented a well-preserved portion of the wooden foundation structure buried by sediments rich in plant remains: both wood and plant remains were subjected to archaeobotanical investigation. The ultimate goal was to improve our knowledge on agricultural economy and wood usage in Tuscany during the prehistoric ages. The results pointed to a farming system based on Triticum spp. (wheat), Hordeum spp. (barley) and Leguminosae cultivation in addition to the gathering of wild fruits, such as Corylus avellana, Cornus mas, Prunus spp., Vitis spp. Many of these plant remains are associated to a wetland context. Mesohygrophilous trees, such as deciduous Quercus, Ulmus minor, Fraxinus cf. excelsior, and Sorbus were used for the construction of the pile-dwelling structures; the choice of these plants indicates a good knowledge of the technological characteristics of timber.  相似文献   
972.
To date more intact dog remains have been found on San Nicolas than on any of the other seven California Channel Islands. However, little is known about them. During the 2007 summer field season we excavated a medium sized young male dog in a flexed burial position from a pit at CA-SNI-25, a large Native American village site. The dog exhibits hypodontia, noticeable tooth attrition, severe scapular trauma, and vertebral, rib, and phalanx pathologies. Most of the injuries appear to have resulted from a severe blunt force trauma of unknown origin and it is likely the dog would not have survived without human care. The results of our analysis contribute to the, somewhat limited, published data on archaeological dogs in California. In this paper we describe the biological characteristics of the dog especially his anomalies and pathologies and compare them with published reports of other North American archaeological dogs with similar conditions.  相似文献   
973.
The origin of Romita pottery has been a controversial topic during the last three decades of Colonial Mexico archaeological studies. Lead isotopic analyses of glaze coatings of Spanish and Mexican pottery, and Romita ceramics unearthed from the archaeological site of the Metropolitan Cathedral in Mexico City provide evidence that support a Mexican origin.  相似文献   
974.
从19世纪起,资本主义社会向工业时代过渡,经济、文化与价值观等各方面都发生了转变,这些转变为经济与社会的关系问题提供了研究基础。19世纪至今的资本主义可以划分为三个发展阶段,即自由资本主义阶段、有组织的资本主义阶段和非西方式的民主经济阶段。可将一个阶段向另一个阶段的过渡称为大转型。每一次转型都是资本主义现代性类型出现危机的结果,而新的现代性类型是通过寻找新的社会价值和社会组织关系来形成的。分析资本主义三次大转型的经济、社会根源,可以清晰地洞察资本主义的过去、现在和未来。同时,三次大转型的新理论框架为预测全球资本主义的未来发展方向提供了理论基础。  相似文献   
975.
Despite increased concern about environmental damage and resource depletion, the private motor car, and associated automobility, are taken-for-granted aspects of twenty-first-century life. This paper makes the counterfactual assumption that private ownership of cars was severely restricted at the start of the twentieth century, and uses a range of historical data to examine the ways in which such a scenario might have impacted on transport infrastructure, personal mobility and urban life. It is argued that, even without the wholesale adoption of the motor car as a means of personal transport, patterns of everyday mobility would not have differed significantly from today so long as other forms of transport had remained or expanded to cope with this demand. However, such a scenario would probably have required journeys to be planned in different ways, may have been qualitatively different from travel today, and could have disadvantaged particular groups of the population, including some women. A landscape without cars would probably also have altered the form of cities, with services provided closer to where people live, and levels of air pollution substantially lower. The counterfactual historical analysis is used to argue that, although there is little likelihood of cars being banned in Britain, greater restrictions on private motor vehicles would not necessarily lead to the fundamental changes in everyday mobility that some might predict.  相似文献   
976.
Urban and Rural Definitions in Regional Context: A Case Study on Turkey   总被引:2,自引:0,他引:2  
Transformations in the urban and rural areas under the effects of global economic, social and political circumstances have rendered their boundaries more blurring. It has become increasingly difficult to make a clear distinction between urban and rural. This paper intends to bring definitions of urban–rural into discussion in the context of Turkey. It reveals the results of a research project (conducted by Hürriyet G. Ö?dül with Serkan Öngel and Habip Uluçay from Mimar Sinan Fine Arts University, Istanbul, Turkey, in 2007 and financed by the Scientific and Technical Research Council of Turkey and Mimar Sinan Fine Arts University Research Fund), aiming at revealing the degrees of the urbanity and rurality throughout the country, with an emphasis on the diversification of regions in the urban–rural context. The study is conducted at the NUTS 4 level. Districts are classified as “dominantly rural, dominantly urban and transitional” through the factor analysis based on six structures: agricultural production, non-agricultural production, employment, demography, education and flows of money, goods and people. The urban–rural profile of the country is found as rural and transitional. It is possible to observe some areas displaying deep rural characters in well-developed western regions and some “prosperity spots” dispersed throughout the less-developed eastern regions. Then, regional classifications ranging from “concentrated urban regions” to “rural regions” are made at the NUTS 1 level. Finally, the results are evaluated in perspectives of spatial planning of Turkey and entering process to the EU.  相似文献   
977.
978.
Lead isotope data, together with an evaluation of previously published results for the chemical composition of Omani ores and copper‐base artefacts are used to define a material signature of Omani copper. Absent from our group of Bronze Age metal (Umm an Nar and Wadi Suq periods) are the signature of ores from Masirah Island and also from the vast deposits in north Oman inland from Suhar. Contemporaneous copper from Bahrain and from Tell Abraq on the Gulf coast is consistent in its material signature with Omani copper; a derivation from Omani ores of this copper is highly likely. A few exceptions at Tell Abraq point to Faynan/Timna in the southern Levant as a possible source region. Among Mesopotamian artefacts the signature of Omani copper is encountered during all cultural periods from Uruk at the end of the fourth millennium BC to Akkadian 1000 years later. Oman/Magan appears to have been particularly important during Early Dynastic III and Akkadian when about half of the copper in circulation bears the Omani signature.  相似文献   
979.
The source and transport regions of fluidized (transported) breccias outcrop in the Cloncurry Fe‐oxide–Cu–Au district. Discordant dykes and pipes with rounded clasts of metasedimentary calc–silicate rocks and minor felsic and mafic intrusions extend several kilometres upwards and outwards from the contact aureole of the 1530 Ma Williams Batholith into overlying schists and amphibolites. We used analytical equations for particle transport to estimate clast velocities (≥20 m sec?1), approaching volcanic ejecta rates. An abrupt release of overpressured magmatic‐hydrothermal fluid is suggested by the localization of the base of the breccias in intensely veined contact aureoles (at around 10 km, constrained by mineral equilibria), incorporation of juvenile magmatic clasts, the scale and discordancy of the bodies, and the wide range of pressure variation (up to 150 MPa) inferred from CO2 fluid inclusion densities and related decrepitation textures. The abundance of clasts derived from depth, rather than from the adjacent wallrocks, suggests that the pressure in the pipes was sufficient to restrict the inwards spalling of fragments from breccia walls; that is, the breccias were explosive rather than implosive, and some may have vented to the surface. At these depths, such extreme behaviour may have been achieved by release of dissolved fluids from crystallizing magma, in combination with a strongly fractured and fluid‐laden carapace, sitting under a strong, low permeability barrier. The relationship of these breccias to the Ernest Henry iron‐oxide–Cu–Au deposit suggests they may have been sources of fluids or mechanical energy for ore genesis, or alternately provided permeable pathways for later ore fluids.  相似文献   
980.
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