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   303篇
  免费   22篇
  2023年   3篇
  2020年   6篇
  2019年   9篇
  2018年   14篇
  2017年   11篇
  2016年   18篇
  2015年   8篇
  2014年   3篇
  2013年   73篇
  2012年   6篇
  2011年   12篇
  2010年   10篇
  2009年   4篇
  2008年   7篇
  2007年   11篇
  2006年   6篇
  2004年   6篇
  2003年   7篇
  2002年   4篇
  2001年   2篇
  2000年   4篇
  1999年   5篇
  1998年   2篇
  1997年   5篇
  1995年   2篇
  1992年   2篇
  1990年   2篇
  1988年   6篇
  1986年   2篇
  1985年   11篇
  1983年   3篇
  1982年   5篇
  1981年   3篇
  1980年   6篇
  1979年   4篇
  1978年   2篇
  1977年   5篇
  1976年   2篇
  1974年   4篇
  1973年   2篇
  1972年   3篇
  1971年   2篇
  1970年   1篇
  1969年   1篇
  1968年   3篇
  1967年   2篇
  1966年   3篇
  1965年   1篇
  1963年   1篇
  1960年   2篇
排序方式: 共有325条查询结果,搜索用时 15 毫秒
21.
Following the exceptional discovery of Neolithic engravings on a boulder at Vallée aux Noirs in the Fontainebleau forest, south of Paris, an excavation trench was opened in order to access the buried part of the decorated rock panel and explore the stratigraphic context of the artwork. A palaeosol was found two metres below the modern ground level, underneath multiple layers of sterile sandy soil forming a very compact sequence from which only one archaeological artefact was recovered – an Iron Age fibula (c.200–300 BC). Dating of the palaeosol was attempted through two different methods: AMS dates from charcoal suggest a significant span from the Early Bronze Age to the Iron Age, while two more consistent OSL dates point to formation of the palaeosol during the Late Neolithic (3500–3000 cal BC). The entire engraved rock surface (16 m2), including its buried part, was fully recorded. Four main semiotic groups were identified: a typical fifth‐millennium crook‐hafted axe with a ring, two boats with steering oars, and a central, very tall human figure dominating the composition from its 3.5‐metre height.  相似文献   
22.
23.
24.
25.
26.
Scanning electron microscopy/energy dispersive X-ray analysis has earlier shown that the white background layer (slip) on painted pottery sherds (Yangshao culture, Henan, China, 4200 BC) is composed of kaolinitic clay containing titanium in the assumed form of TiO2 at just 1 wt%. The same samples of white slip have now been studied by Raman microscopy, revealing bands characteristic of anatase, but none from the majority species, the matrix of kaolinitic clay. These results highlight the extraordinarily intense Raman scattering from even trace amounts of anatase and thus the need to recognise that, although the colours of archaeological artefacts are almost always determined by the nature of the matrix, the Raman spectrum may be determined by a highly scattering trace component such as anatase. The significance of anatase as a potential date-marker pigment on works of art and archaeological artefacts is discussed.  相似文献   
27.
This study analyzes oral pathological conditions—caries, antemortem tooth loss, and occlusal macrowear—among adults (N = 70) interred at Machu Picchu, Peru. Previous isotopic diet reconstructions at Machu Picchu suggest substantial early‐life variation that may have narrowed somewhat by the last decade of life. This study seeks to further elucidate the intersection of diet, sex, and health at Machu Picchu by analyzing oral pathological conditions with existing carbon and nitrogen isotopic data. Observed caries prevalence is corrected to control for age and tooth loss, and is described for both anterior and posterior teeth; wear data are scored and reported for individual tooth types. Results indicate caries prevalence consistent with carbohydrate‐rich diets and no significant difference between males and females. However, no significant isotopic parameters are associated with caries prevalence in young adult males, while caries prevalence is significantly associated only with enamel carbonate δ13C in older adult males. Dietary protein sources, but not C4 resources, are associated with caries prevalence in young adult females, and to a lesser degree in older adult females. Significant associations between occlusal wear and caries exist among young adult males and young adult females, but involving different tooth types. These findings suggest differential protein consumption at Machu Picchu between males and females, and separate masticatory and physiological processes shaping caries prevalence between the sexes at the site. This study therefore underscores the role that gender roles may have played in diet variation among this population and the need to account for sex in analyzing oral pathology. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
28.
ABSTRACT This paper investigates the extent to which house–price uncertainty affects the transition of renter households into homeownership. Using a 14‐year household panel from the Panel Study of Income Dynamics during the years 1984–1997 and measures of the time‐varying risk and return to owner‐occupied housing, we estimate a Cox proportional hazard model of the effect of house–price volatility on the transition into homeownership. Results indicate that house–price uncertainty has a negative and dramatic impact on transitions into homeownership. In addition, we find that the low‐wealth renters are particularly sensitive to house–price risk.  相似文献   
29.
The present study utilises dental histological methods to analyse enamel micro‐defects as indicators of early life stress in indigenous Muchik individuals interred at two sites: La Capilla Santa María Magdalena de Eten (CSMME) (n = 15) and La Capilla del Niño Serranito (CNS) (n = 15), both located in the Lambayeque Valley region of northern Peru. Individuals interred at CNS date to the Early Colonial Period (AD 1533–1610), and individuals interred at CSMME date to the Middle/Late Colonial Period (AD 1625–1760), thus permitting comparison of childhood stress events between the Early and Middle/Late Colonial Periods. Results reveal a high prevalence of Wilson bands at both sites, although a lower prevalence at the CSMME was observed in comparison with the CNS. This indicates that, over time, Muchik individuals in this town may have been able to acclimate to life under Spanish oppression. Stress chronologies suggest that early life stress possibly resulted from inadequate and less than desirable food and/or water available for supplemental feeding during early infancy, especially around the ages of 4 and 5 months. Furthermore, results show that individuals with enamel defects in the form of Wilson bands at both the CNS and CSMME had an earlier mean age‐at‐death (9.6 and 4.05 years, respectively) in comparison with those without observed Wilson bands (19.75 and 8.8 years, respectively). These results underscore the importance of not only regional and temporal studies of the biological consequences of Spanish contact in the Americas but also of investigating the relationship between early life stress and adult health and longevity in archaeological populations. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
30.
Zipf's rank‐size rule, lognormal distribution, and Gibrat's urban growth models are considered as summarizing fundamental properties of systems of cities. In this article, they are used as statistical benchmarks for comparing the shapes of urban hierarchies and evolutionary trends of seven systems of cities in the world including BRICS, Europe, and United States. In order to provide conclusions that avoid the pitfalls of too small samples or uncontrolled urban definitions, these models are tested on some 20,000 urban units whose geographically significant delineations were harmonized in each country over 50 years between 1960 and 2010. As a result, if the models appear not always statistically valid, their usefulness is confirmed since the observed deviations from empirical data remain limited and can often be interpreted from the geohistorical context of urbanism proper to each world region. Moreover, the article provides new free software which authorizes the reproducibility of our experiments with our data bases as well as with complementary data.  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