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   477篇
  免费   20篇
  497篇
  2023年   3篇
  2022年   2篇
  2021年   4篇
  2020年   15篇
  2019年   24篇
  2018年   24篇
  2017年   20篇
  2016年   29篇
  2015年   17篇
  2014年   17篇
  2013年   131篇
  2012年   16篇
  2011年   9篇
  2010年   15篇
  2009年   11篇
  2008年   7篇
  2007年   11篇
  2006年   6篇
  2005年   8篇
  2004年   10篇
  2003年   4篇
  2002年   7篇
  2001年   5篇
  2000年   4篇
  1999年   5篇
  1998年   4篇
  1997年   5篇
  1996年   6篇
  1995年   2篇
  1994年   3篇
  1993年   3篇
  1992年   3篇
  1991年   5篇
  1990年   4篇
  1989年   2篇
  1986年   5篇
  1985年   7篇
  1984年   4篇
  1983年   6篇
  1982年   4篇
  1980年   4篇
  1979年   5篇
  1978年   2篇
  1976年   5篇
  1975年   2篇
  1971年   1篇
  1969年   1篇
  1957年   1篇
  1949年   3篇
  1948年   1篇
排序方式: 共有497条查询结果,搜索用时 15 毫秒
91.
Significant political and economic developments among the Chumash of southern California were catalyzed in part by the emergence of an intensive, specialist-driven shell-bead industry during the second millennium CE on the Santa Barbara Channel Islands. The production of millions of beads depended in turn on the availability of lithic microdrills of standardized form and materials. Channel Islanders quarried a particular stone type, a blocky Monterey Formation chert, from multiple outcrops situated close to the eastern shores of Santa Cruz Island. Rich archaeological assemblages document the lithic and shell byproducts of these intertwined production systems, each of which endured for several centuries (CE 1150–1819). Islanders invariably chose Island chert for making microdrills: hundreds of thousands of specimens recorded to date are of this material. Furthermore, nearly every microlith in all of Chumash territory (post CE 1150) was produced on the islands; the large populations on the mainland did not participate in microlith making or bead making after CE 1150–1200. We argue that this pattern had its roots not only in the patchiness of key resources and shifting regional social relationships, but also in the physical properties of available raw materials. Here we experimentally assess the properties of Santa Cruz Island chert alongside three important mainland raw materials—Grimes Canyon fused shale, Coso obsidian, and Vandenberg chert—that potentially could have been tapped to make microliths. We test the proposition that Island chert outperforms other lithic materials in drilling efficiency and drill use life. Our experimental results from 108 drilling trials reveal sharp distinctions in performance characteristics across the four materials. We infer that the process by which Islanders became the more-or-less exclusive manufacturers of shell-bead currency in southern California was facilitated by both the efficacy and physical properties of the Island cherts and the propitious locations of the outcrops.  相似文献   
92.
Two associated anterior dorsal vertebrae of a primitive archosaur are described from the Early Triassic (Dienerian–Spathian) Bulgo Sandstone at Long Reef, New South Wales, Australia. Character states including anteroposteriorly elongate centra, dorsal neural spines with height greater than length, the possible presence of intercentra, double-headed rib articulations and well-developed apical tables on the neural spines suggest affinity with proterosuchid archosauriforms and permit some comparisons with previously described Australian taxa. The Bulgo Sandstone vertebrae represent the first record of archosaurian body fossils from the Sydney Basin and are one of only a handful of occurrences thus far documented from the Triassic of Australia.  相似文献   
93.
Pterosaur remains are very rare in Australasia and especially in Upper Cretaceous strata. Thus, the discovery of a jaw fragment from the Cenomanian–Coniacian Molecap Greensand near Gingin in Western Australia represents an important new stratigraphical occurrence for the region. Although the teeth are not preserved, the presence of labio-lingually compressed alveoli that are anterolaterally oriented, variable in shape/size (inferring heterodonty) and very widely spaced is reminiscent of ornithocheirids—a geographically cosmopolitan clade of predominantly Early Cretaceous pterodactyloids. If correct, this identification could extend the known range of Ornithocheiridae through to the Late Cretaceous in the Southern Hemisphere.  相似文献   
94.
The changing dynamics of regional and local labor markets during the last decades have led to an increasing labor market segmentation and socioeconomic polarization and to a rise of income inequalities at the regional, urban, and intraurban level. These problems call for effective social and local labor market policies. However, there is also a growing need for methods and techniques capable of efficiently estimating the likely impact of social and economic change at the local level. For example, the common methodologies for estimating the impacts of large firm openings or closures operate at the regional level. The best of these models disaggregate the region to the city (Armstrong 1993; Batey and Madden 1983). This paper demonstrates how spatial microsimulation modeling techniques can be used for local labor market analysis and policy evaluation to assess these impacts (and their multiplier effects) at the local level‐to measure the effects on individuals and their neighborhood services. First, we review these traditional macroscale and mesoscale regional modeling approaches to urban and regional policy analysis and we illustrate their merits and limitations. Then, we examine the potential of spatial microsimulation modeling to create a new framework for the formulation, analysis and evaluation of social and local labor market policies at the individual or household level. Outputs from a local labor market microsimulation model for Leeds are presented. We show how first it is possible to investigate the interdependencies between individual's or households labor market attributes at the microscale and to model their accessibilities to job opportunities in different localities. From this base we show how detailed what‐if microspatial analysis can be performed to estimate the impact of major changes in the local labor market through job losses or gains, including local multiplier effects.  相似文献   
95.
Books reviewed in this article:
Vernon M. Briggs, Jr. Immigration Policy and the American Labor Force .
Vernon M. Briggs, Jr. and Martha Tienda, eds. Immigration: Issues and Policies .
Elizabeth Hull. Without Justice for All: The Constitutional Rights of Aliens .
Milton Morris. Immigration: The Beleaguered Bureaucracy .  相似文献   
96.
97.
Epistemology     
  相似文献   
98.
99.
ABSTRACT

This paper examines ideas of individual freedom in the Hellenistic city-states (c. 323–31 BCE). It concentrates on the civic ideas expressed in the laws and decrees of Hellenistic cities, inscribed on stone, comparing them with Hellenistic historical and philosophical works. It places different Hellenistic approaches alongside modern liberal, neo-Roman republican and civic humanist theories of individual liberty, finding some overlaps with each of those modern approaches. The argument is that the Hellenistic Greeks developed innovative ways of combining demanding ideals of civic virtue and the common good with equally robust ideals of individual freedom and ethical choice. They did so not least by adapting and developing traditional Greek approaches close to modern civic humanism, in ways very relevant to modern debates about how to reconcile civic duty, the common good and pluralism.  相似文献   
100.
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