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   1776篇
  免费   314篇
  2023年   8篇
  2021年   19篇
  2020年   22篇
  2019年   119篇
  2018年   83篇
  2017年   88篇
  2016年   148篇
  2015年   91篇
  2014年   92篇
  2013年   378篇
  2012年   109篇
  2011年   112篇
  2010年   90篇
  2009年   67篇
  2008年   75篇
  2007年   78篇
  2006年   51篇
  2005年   26篇
  2004年   47篇
  2003年   33篇
  2002年   30篇
  2001年   26篇
  2000年   33篇
  1999年   15篇
  1998年   19篇
  1997年   22篇
  1996年   17篇
  1995年   24篇
  1994年   17篇
  1993年   7篇
  1992年   6篇
  1991年   7篇
  1988年   3篇
  1987年   5篇
  1986年   4篇
  1985年   6篇
  1984年   8篇
  1983年   11篇
  1982年   10篇
  1981年   3篇
  1980年   8篇
  1979年   10篇
  1978年   7篇
  1977年   10篇
  1976年   9篇
  1975年   7篇
  1974年   3篇
  1973年   3篇
  1972年   4篇
  1971年   3篇
排序方式: 共有2090条查询结果,搜索用时 78 毫秒
101.
102.
Having been adopted by legislatures in over a dozen states, postsecondary merit aid programs are largely concentrated in the southeastern United States. The observed clustering pattern seems to support previous evidence that policies spread between proximate states, a phenomenon referred to by political scientists as policy diffusion. Often, however, policy diffusion is not complete, and one or more states in a region fail to adopt. By interviewing policymakers throughout the southeastern United States—including actors in the three states in the region without merit aid—the study addresses the following question: Why do diffusion pressures lead to adoption in some states but not in others? Studying state “hold‐outs” promises not only to uncover the reasons for failed legislation in specific state contexts but also to better our understanding of the limits of diffusion theory.  相似文献   
103.
104.
105.
106.
107.
108.
We present the palaeopathological analysis of a right fourth metatarsal (ATD6‐124) recovered from the Atapuerca–Gran Dolina site (Spain). This fossil, ca. 1 Ma, belongs to Homo antecessor, the earliest known European hominin species. The metatarsal exhibits a proliferative lesion on its medial periosteal surface. Periosteal reaction can be the bone response to a wide number of injurious processes. We describe a lesion on the basis of macroscopic and microscopic analyses, including microtomography and scanning electron microscopy. Externally, the osteoblastic lesion presents a highly porotic and disorganised morphology. Internally, we observe a series of micro‐fractures on the compact bone that do not affect the medullary canal. We provide a differential diagnosis and suggest that the ATD6‐124 lesion could correspond to a pedal stress fracture, also known as fatigue or march fracture. Stress fractures have been related to a load increase and muscular fatigue. This type of fracture has been widely reported in the foot of soldiers and athletes, which are usually engaged in strenuous, excessive or prolonged locomotive activities. Despite its high frequency in these groups, stress fractures have not been reported as such in fossil collections, with the exception of a metatarsal belonging to the Sima de los Huesos site (Atapuerca). Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
109.
Intercontinental exchanges between communities living in different parts of Eurasia during the late prehistoric period have become increasingly popular as a topic of archaeological research. The Qijia culture, found in northwest China, is one of the key archaeological cultures that can shed light on trans‐Eurasian exchange because a variety of imports are found in this cultural context. These imports include new cereals and animals, which suggest that human diets may also have changed compared with previous periods. To understand human and animal diets of the Qijia culture, carbon and nitrogen isotope ratios from human and animal skeletal remains were analysed from the type site of the Qijia culture at Qijiaping. The results demonstrate that human diet at the site mainly consisted of millet and animals fed on millet. C3 cereals, such as wheat and barley, did not contribute significantly to human diet, and no isotopic differences were found between adult and subadult diets. Furthermore, three outlying human results raise the possibility of exogenous individuals, perhaps in relation to the parallel movement of animals, crops and goods. This study provides human and animal dietary information for evaluating the nature of exchange and diffusion in eastern Eurasia at this time. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
110.
This paper presents some of the basic principles of bone fracture physics and outlines characteristics used by forensic anthropologists to distinguish gunshot trauma from blunt trauma. The fracture pattern of a cranium from a historic cemetery in Memphis, Tennessee provides an example of how the mechanism of trauma could be misinterpreted. The pattern of the perimortem fractures is indicative of gunshot trauma with a bullet entering one side of the vault and impacting the opposite side. Identification of radiating fractures, concentric heaving fractures, and observation of the direction of bevel on the fractured surfaces are essential for interpretation of the mechanism that produced the injury.  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