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   7717篇
  免费   407篇
  2023年   48篇
  2020年   135篇
  2019年   181篇
  2018年   253篇
  2017年   230篇
  2016年   303篇
  2015年   196篇
  2014年   185篇
  2013年   2031篇
  2012年   237篇
  2011年   261篇
  2010年   248篇
  2009年   240篇
  2008年   211篇
  2007年   224篇
  2006年   181篇
  2005年   137篇
  2004年   115篇
  2003年   113篇
  2002年   123篇
  2001年   151篇
  2000年   110篇
  1999年   124篇
  1998年   94篇
  1997年   83篇
  1996年   84篇
  1995年   72篇
  1994年   61篇
  1993年   75篇
  1992年   75篇
  1991年   62篇
  1990年   60篇
  1989年   57篇
  1988年   54篇
  1987年   61篇
  1986年   62篇
  1985年   72篇
  1984年   80篇
  1983年   85篇
  1982年   69篇
  1981年   68篇
  1980年   66篇
  1979年   62篇
  1978年   66篇
  1977年   70篇
  1976年   62篇
  1975年   71篇
  1974年   42篇
  1973年   39篇
  1972年   45篇
排序方式: 共有8124条查询结果,搜索用时 328 毫秒
11.
12.
Almost all of the obsidian used to craft stone tools in the Near East from the Palaeolithic onward originated from volcanoes in two geographic regions: Central Anatolia and Eastern Anatolia. Five decades of obsidian sourcing has led to the view that Central Anatolian obsidians largely followed the Mediterranean coast and rarely reached farther east than the Middle Euphrates, whereas Eastern Anatolian sources almost exclusively supplied sites east of the Euphrates. This paper discusses the identification of Central Anatolian obsidian artefacts at the Bronze-Age site of Tell Mozan (Urkesh) in northeastern Syria. Most of the obsidians at Tell Mozan (97%) came from the Eastern Anatolian sources, as expected from established distribution models. Artefacts of Central Anatolian obsidian, however, were excavated from one well-constrained context: the deposits on a palace courtyard that date to the height of the Akkadian empire's influence at this third-millennium Hurrian religious and political centre. In particular, the obsidian came from the Kömürcü source of Göllü Da?. Potential explanations for this exotic obsidian are discussed. This obsidian might have “piggybacked” on the distribution of Central Anatolian metals or arrived at this city as royal gifts or prestige items. Other discussed mechanisms include Akkadian-linked changes in either territoriality involving pastoral nomads responsible for the arrival of Eastern Anatolian obsidians or identity construction of elites based on involvement in Central Anatolian economic and political networks.  相似文献   
13.
14.
15.
16.
"A model of private local labor demand and interjurisdictional migration is presented and estimated using data from Swedish counties and municipalities for 1979-84. Our goal is to compare the effects on local labor markets of distinctive public-sector programs with those of traditional market variables. We find that local income taxes and tax-equalization grants have important effects on local labor markets; regional development policy measures and geographical-mobility subsidies do not. Thus, recent efforts scaling back some of these programs may not materially alter the regional economy's performance. Wages and other traditional market variables are also often found to influence significantly local labor markets."  相似文献   
17.
An axiomatic approach to distance is developed which focuses on those behavioral concepts of distance related to movement in space. In particular, spatial movement by behaving units is postulated to involve a choice from among some set of abstract trips in space, and implicitly, to involve the minimization of some relevant notion of trip costs. In this context, the relevant behavioral notion of distance in space is taken to be the minimum-cost distance generated by this choice process. These trip-cost concepts extend the classical notions of paths, path lengths, and shortest paths in metric spaces. Hence many of the analytical results of the paper involve extensions of classical shortest-path distance properties to minimum-cost distances. In addition to these extensions, a characterization theorem is given which specifies the possible functional relationships between trip costs and their associated path lengths. These relationships include most functional forms which are commonly employed in the literature.  相似文献   
18.
19.
20.
In 1985 a Neanderthal skeleton was found in the cave of Kebara in southern Mt. Carmel. Electron spin resonance (ESR) dates have been obtained on tooth enamel of gazelles found in layer X, just overlying the layer in which the skeleton was found. Assuming early uptake of uranium by the teeth, they yield an age of 60 ± 6 ka; assuming gradual, linear uptake of uranium yields an age of 64 ± 6 ka. Both age estimates are consistent with a previous estimate for the skeleton, based on TL dating of burnt flint, of 60 ± 4 ka.  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