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   3282篇
  免费   200篇
  2023年   34篇
  2021年   14篇
  2020年   91篇
  2019年   75篇
  2018年   174篇
  2017年   154篇
  2016年   193篇
  2015年   119篇
  2014年   132篇
  2013年   786篇
  2012年   116篇
  2011年   105篇
  2010年   104篇
  2009年   80篇
  2008年   89篇
  2007年   80篇
  2006年   58篇
  2005年   60篇
  2004年   45篇
  2003年   32篇
  2002年   45篇
  2001年   51篇
  2000年   34篇
  1999年   41篇
  1998年   26篇
  1997年   32篇
  1996年   29篇
  1995年   29篇
  1994年   22篇
  1993年   30篇
  1992年   26篇
  1991年   23篇
  1989年   21篇
  1988年   18篇
  1987年   25篇
  1986年   23篇
  1985年   27篇
  1984年   31篇
  1983年   25篇
  1982年   30篇
  1981年   21篇
  1980年   31篇
  1979年   26篇
  1978年   20篇
  1977年   18篇
  1976年   17篇
  1973年   17篇
  1972年   21篇
  1971年   16篇
  1967年   18篇
排序方式: 共有3482条查询结果,搜索用时 78 毫秒
101.
102.
103.
104.
105.
106.
One of the most intriguing questions for archaeologists studying clay artefacts concerns technologies employed in their manufacture and whether standardization can be demonstrated through traditional ceramic analysis. Visual comparisons and mechanical measurements have been used to determine correlations and infer standardization. Using a laser multi‐line scanner and software developed to quantify Hausdorff distances between vertices in 3D surfaces, we analysed sample collections of figurines and moulds from Belize, Mexico and Honduras. The results indicated that this procedure was a more precise indicator of common source and standardization in moulded clay artefacts. This method provided data relevant to assessing the scope of ancient trade networks and the nature of social and economic relationships that existed among the ancient inhabitants of Mesoamerica.  相似文献   
107.
Yelang (夜郎), a mysterious state located in the south‐western area of early China and dating from the Bronze Age to the Early Iron Age (1300 bc – ad 25), is a cultural interactive junction between the Yunnan–Guizhou Plateau and the Yangtze River Basin. The Zhongshui Basin in Weining County, Guizhou Province, was one of the important distribution areas of the Yelang civilization. This area, which includes sites at Jigongshan (鸡公山; 1300 – 800 bc ), Hongyingpan (红营盘; 700 – 400 bc ) and Yinzitan (银子坛; 400 bc – ad 25), has provided a very integrated chronology, spanning from the Bronze Age to the Early Iron Age in the eastern Yunnan – western Guizhou area. To investigate human migration and horse‐trading at these Yelang sites, we conducted a strontium isotopic analysis on the teeth enamel of humans and horses unearthed from these three sites. The results indicated the following: (1) people at the earlier sites (Jigongshan and Hongyingpan) were all indigenous, whereas in the Yinzitan cemetery, there was a more immigrant population, and all the people who were buried in an upper limb flexed supine position were non‐local; and (2) most of the horses found at the Jigongshan and Yinzitan sites show different provenances, probably related to the famous Dian (滇) and Zuo (筰) horses recorded in historical documents, providing more clues for further study on horse‐trading in South‐West China during the Bronze Age and the Early Iron Age.  相似文献   
108.
The original fineness of coins is very important information that can help us to understand the commercial situation in a wide historical context. This paper deals with a comparison of analytical methods suitable for the evaluation of the actual and original fineness of coins based on a detailed case study of a medieval coin sample. Both non‐destructive (i.e., scanning electron microscopy/energy‐dispersive X‐ray spectroscopy, X‐ray fluorescence, atomic force microscopy and hydrostatic weighing) and destructive (i.e., inductively coupled plasma – mass spectrometry and the Volhard titration method) techniques were used. The original fineness can be also deduced from knowledge of the internal structure of the coin (limited miscibility of copper and silver). A new analytical method based on a combination of a micrograph of the metallographic cross‐section with consequent image analysis was developed for determination of the original fineness. The proposed approach is relatively simple and provides reliable values. Sample heterogeneity and its impact on the determination of fineness are also discussed.  相似文献   
109.
A human skull, buried about 2500 years ago in a Bronze Age cemetery at Jinggouzi, a site of an important ethnic group in ancient China, appeared to have characteristics of fibrous dysplasia. The CT images indicated a reduction in bone density and relatively homogeneous lesions. More features were revealed using CT reconstruction techniques. Lesions seen in low‐magnification images using a 3D deep‐field microscope had an irregular honeycomb‐like structure. At higher magnification, the trabeculae morphology and the gaps between the trabeculae were irregular and varied in size and shape. Paraffin‐embedded specimens stained with HE showed trabeculae with tortuous irregular arrangements varying in shape and width. The irregular trabeculae of woven bone has been described as having fibrous dysplasia. Molecular analysis of the GNAS gene indicated no mutation. This provides a non‐invasive approach for us to make more comprehensive diagnoses and to assist research into ancient human diseases.  相似文献   
110.
Among the wide range of geographic analysis methods are service coverage models. These location analytic approaches have been invaluable for better understanding existing (and past) conditions, deriving creative plans, and developing policy for addressing associated societal problems. Increasingly sophisticated spatial information and better knowledge about interrelated mechanisms of process and behavior have made it possible to enhance coverage models, enabling more nuanced formalizations to be devised. This has proven both important and essential in many ways. Mathematical details associated with service coverage models are derived to highlight evolving capabilities. Empirical results are presented in order to illustrate the significance and substantive importance of advanced location analytics capabilities.  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