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   9038篇
  免费   110篇
  9148篇
  2020年   106篇
  2019年   128篇
  2018年   436篇
  2017年   381篇
  2016年   454篇
  2015年   178篇
  2014年   160篇
  2013年   1997篇
  2012年   223篇
  2011年   394篇
  2010年   391篇
  2009年   244篇
  2008年   256篇
  2007年   229篇
  2006年   154篇
  2005年   135篇
  2004年   118篇
  2003年   83篇
  2002年   88篇
  2001年   117篇
  2000年   109篇
  1999年   104篇
  1998年   78篇
  1997年   89篇
  1996年   65篇
  1995年   70篇
  1994年   69篇
  1993年   83篇
  1992年   76篇
  1991年   81篇
  1990年   63篇
  1989年   70篇
  1988年   61篇
  1987年   90篇
  1986年   61篇
  1985年   95篇
  1984年   91篇
  1983年   109篇
  1982年   82篇
  1981年   87篇
  1980年   95篇
  1979年   78篇
  1978年   82篇
  1977年   107篇
  1976年   95篇
  1975年   79篇
  1974年   70篇
  1973年   62篇
  1972年   57篇
  1971年   53篇
排序方式: 共有9148条查询结果,搜索用时 15 毫秒
61.
Novel technologies linked to women and men through identity-demarcated tasks and knowledge sets can potentially have differential and even long-term effects on each group. This study follows the trajectory of two significant imports into the coastal western Alaskan system, the firearm and the metal cook pot. These imports had different implications for coastal Yup’ik women and men, young and old. Over time the gun became an integral piece of a man’s tool kit and one that had the potential to boost production and thus a man’s access to status-building. However, these same tools had the potential to undermine the apprenticeship system of male authority. Likewise, the metal cook pot replaced the productive oversight and skill set of elder women’s ceramic production but created paths of independence for younger Yup’ik women. These changes in technology destabilized relative balances of gender and age based status, security, and authority and fashioned new gender and age based social and economic opportunities and limitations.  相似文献   
62.
Archaeological predictive modeling has been used successfully for over 20 years as a decision-making tool in cultural resources management. Its appreciation in academic circles however has been mixed because of its perceived theoretical poverty. In this paper, we discuss the issue of integrating current archaeological theoretical approaches and predictive modeling. We suggest a methodology for doing so based on cognitive archaeology, middle range theory, and paleoeconomic modeling. We also discuss the problems associated with testing predictive models.  相似文献   
63.
Mumba rockshelter is a key archaeological site for the Middle and Later Stone Age occupation of East Africa, but its chronology has remained unresolved. We report the results of a dating study, focussing on the characterisation of the optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) properties of quartz- and potassium-rich feldspar grains. Quartz has previously proven troublesome for dating in East Africa. We identified five general types of quartz grain behaviour, based on the shapes of their OSL decay and dose–response curves. Dose recovery experiments and measurement of the natural samples revealed particular problems with quartz grains that had hyperbolic dose–response curves, low characteristic saturation doses and anomalously large changes in sensitivity between regenerative-dose cycles. The use of pulsed irradiation during measurement and standard and additional quality-assurance criteria during data analysis reduced the number of grains that suffered from these problems. We applied these procedures to individual grains of quartz from eight samples and, using appropriate statistical models, identified post-depositional mixing in three samples. The remaining samples had scattered equivalent-dose distributions typical of quartz grains that had received variable beta dose rates during burial. Stratigraphically consistent OSL ages were obtained for all but the deepest sample. Feldspar ages were estimated for the latter sample and three other samples, using the elevated temperature IRSL signal that exhibited low rates of anomalous fading. Fading-corrected feldspar ages for the latter three samples are consistent with their single-grain quartz ages, but single-grain dating is needed to address problems of post-depositional mixing.  相似文献   
64.
65.
Between 2005 and 2009 a deep‐water shipwreck was located, mapped, and partially excavated by a joint team from RPM Nautical Foundation and the office of the Soprintendenza del Mare, Sicily. Located off Levanzo Island, one of the Egadi Islands off north‐west Sicily, this wrecked merchantman revealed a mixed cargo of foodstuffs, coarseware, glass, and construction materials. The nature of the wreck‐site, its cargo, operational date, and find‐location indicate its likely association with the annona service which supplied Rome. © 2012 The Authors  相似文献   
66.
New work at Kehf el Hammar Cave provides the first well-dated palaeoenvironmental sequence for the Late Upper Palaeolithic in this region of the northwest Maghreb. The archaeological layers are dated via a combination of AMS radiocarbon and luminescence dating methods. The sequence contains charcoal-rich occupation layers with faunal, human and lithic finds. Local vegetational patterns are reconstructed on the basis of preliminary analysis of the charcoal evidence. Using standard calibration curves the AMS radiocarbon dates are compared with proxy evidence for climatic change from sea core records in the Alborán Sea. These appear to show that the Late Upper Palaeolithic occupation of the region coincides closely with Heinrich Event 1, a period marked by intense aridification and dating to ca. 16,700–17,250 calendar years ago.Les nouvelles recherches dans la grotte de Kehf el Hammar ont permis d’obtenir la première séquence paléoenevironnementale bien datée du Paléolithique supérieur tardif au Nord Ouest du Maghreb. En effet, les niveaux archéologiques ont été datés par le radiocarbone par accélérateur (AMS) et des méthodes radiométriques basées sur la luminescence. En revanche, les paléoenvironnements végétaux ont été partiellement reconstitués à base des premières analyses des charbons de bois. Les dates AMS calibrées ont été comparées aux données climatiques issues des carottes marines dans la mer Alborán. Ainsi, les occupations humaines du Paléolithique supérieur tardif dans la région ont sensiblement coïncidé avec l’événement climatique Heinrich 1. Celui-ci correspond à une période qui a été marquée par une aridification intense entre 16.700 et 17.250 ans (cal.).  相似文献   
67.
68.
69.
Benson, R.B.J., Fitzgerald, E.M.G., Rich, T.H. & Vickers-Rich, P., 2013. Large freshwater plesiosaurian from the Cretaceous (Aptian) of Australia. Alcheringa 37, 1–6. ISSN 0311-5518

We report a large plesiosaurian tooth from the freshwater early–middle Aptian (Early Cretaceous) Eumeralla Formation of Victoria, Australia. This, combined with records of smaller plesiosaurian teeth with an alternative morphology, provides evidence for a multitaxic freshwater plesiosaurian assemblage. Dental and body size differences suggest ecological partitioning of sympatric freshwater plesiosaurians analogous to that in modern freshwater odontocete cetaceans. The evolutionarily plastic body plan of Plesiosauria may have facilitated niche differentiation and helped them to exclude ichthyosaurs from freshwater environments during the Mesozoic. However, confirmation of this hypothesis requires the discovery of more complete remains.

Roger B.J. Benson [roger.benson@earth.ox.ac.uk], Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK; Erich M.G. Fitzgerald [efitzgerald@museum.vic.gov.au], Thomas H. Rich [trich@museum.vic.gov.au], Museum Victoria, GPO Box 666, Melbourne, Victoria 3001, Australia; Thomas H. Rich and Patricia Vickers-Rich [pat.rich@monash.edu], School of Geosciences, Monash University, Clayton, Victoria 3800, Australia. Received 30.10.2012; revised 27.1.2013; accepted 31.1.2013.  相似文献   
70.
The first known ammonite from the Maastrichtian of the Perth Basin, a single, incomplete specimen of Grossouvrites gemmatus (Huppé, 1854), is described from core material from the Lancelin No. 1 borehole. Foraminiferal and nannoplankton evidence date the ammonite as middle Maastrichtian; its age is also assessed on the basis of dinoflagellate assemblages from this section, but these give a less precise dating. The position of the ammonite with respect to a mid-Maastrichtian disconformity, which probably extended along much of the Western Australian margin is discussed.  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