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   1484篇
  免费   90篇
  2024年   8篇
  2023年   40篇
  2022年   16篇
  2021年   19篇
  2020年   62篇
  2019年   77篇
  2018年   90篇
  2017年   82篇
  2016年   74篇
  2015年   57篇
  2014年   58篇
  2013年   189篇
  2012年   115篇
  2011年   86篇
  2010年   82篇
  2009年   73篇
  2008年   80篇
  2007年   75篇
  2006年   60篇
  2005年   30篇
  2004年   18篇
  2003年   28篇
  2002年   20篇
  2001年   12篇
  2000年   17篇
  1999年   9篇
  1998年   6篇
  1997年   7篇
  1996年   7篇
  1995年   5篇
  1994年   4篇
  1993年   7篇
  1992年   3篇
  1991年   1篇
  1990年   1篇
  1988年   1篇
  1987年   2篇
  1985年   9篇
  1984年   6篇
  1983年   9篇
  1982年   7篇
  1981年   5篇
  1980年   5篇
  1979年   9篇
  1978年   3篇
排序方式: 共有1574条查询结果,搜索用时 62 毫秒
971.
何光强  宋秀琚 《人文地理》2014,29(2):113-122
地缘政治分析离不开地图。在全球地缘政治分析中,作为世界地图基本空间框架的地图投影通过变形为人们架起了一座"认知的桥梁"--一种空间认知的视角,包括结构、中心方位、距离和面积四种认知。它们在人脑中组合成世界意象地图,为全球地缘政治分析营造了一个多维的空间思维条件。世界观念研究、地缘动态研究,地区研究和全球性问题研究都离不开全球地图投影。总之,地图投影对于国际关系研究具有重要价值。  相似文献   
972.
A sample of Folsom points from the Southern Plains of Texas and New Mexico is analyzed quantitatively in order to assess patterns of point resharpening in relation to distance to raw material source area and evaluate models of how resharpening was accomplished in terms of point design. A newly developed digitizing method is used to capture 12 interlandmark characters from coordinate data to describe point form. Principal components analysis is used to investigate size and shape variation in point form, and the symmetry and allometry of characters are used to explore the effects of resharpening on point dimensions. Size allometry illustrates the degree of association of relative point proportions, and other aspects of point form, with point size. Blade length, the leading edge of the weapon, was found to be isometric with point size, suggesting that this character was critical to the proper functioning of weapon tips. The regulation of blade length to point size supports a fixed-in-haft model for Folsom point resharpening. Multivariate analyses show that reduction in point forms do not correlate with distance-to-source but are more consistent with the model of the cyclical resharpening and replacement of points. This research illustrates that multivariate and allometric analyses are useful methods for investigating models of technological organization and the effects of resharpening on point form.  相似文献   
973.
While tobacco use was a widespread and important social practice among Native Americans during the Historic Period, the prehistoric origins of the practice are poorly understood. Smoking pipes significantly predate botanical evidence of tobacco in Eastern North America. A promising technique for addressing this problem is gas chromatography/mass spectroscopy (GC/MS) analysis to identify nicotine or related compounds in smoking pipe residues. GC/MS analysis of a smoking pipe dating to approximately 300 B.C. from the Boucher Site, a Middlesex-complex site from Vermont, has produced evidence of nicotine decay products. This is interpreted as evidence for an Early Woodland Period origin for tobacco use in Eastern North America. The cultural and chronological implications of this finding are discussed.  相似文献   
974.
Simultaneous analysis of relationships between multiple artifact classes is required for characterization of many types of activity areas. This paper illustrates improved forms of multivariate visualization, spatial analysis and integration of experimental results that are possible with GIS based photomapping. Techniques are demonstrated through analysis of a hearth associated artifact scatter exposed during excavations of a Late Archaic pithouse at Jiskairumoko, Peru. A multivariate density raster is created and additive color visualization is used for simultaneous display of three artifact distributions. Performing unconstrained clustering in a GIS, space is classified by simultaneous relative density relationships between multiple object types.  相似文献   
975.
Climate deterioration at around the time of the Bronze Age/Iron Age transition has for long been argued to have resulted in upland abandonment in northern and western Britain, and recent research has provided evidence that a major climate downturn from 850 cal BC caused settlement abandonment in western Europe and potentially worldwide. It is, however, unclear to what extent only ‘marginal’ sites were affected, due to the lack of any systematic attempt to view the evidence for settlement and land-use change across a range of landscape types with differing sensitivities to environmental change. This paper addresses this issue by an evaluation of 75 pollen sequences spanning the late Bronze Age and early Iron Age in Britain to assess whether climatic deterioration was sufficient to cause widespread land abandonment. The results provide no evidence for wholesale land-use change at this time; the overall picture is one of continuity of land use or even increased agricultural activity. There are, however, hints of regional variability, with a greater tendency to abandonment of upland areas in Wales, and signs of woodland regeneration in agriculturally productive areas of lowland central southern England. The latter pattern may reflect a combination of rising ground-water levels affecting local land-use in the immediate vicinity of the mires which provide the source of the pollen data, against a backdrop of regional-scale social and economic changes at the Bronze Age-Iron Age transition.  相似文献   
976.
采用相差分析方法,区分出禾本科植物中的农作物花粉;通过对青海互助丰台卡约文化遗址文化层和丰台村周围现代表土样品的孢粉分析,发现孢粉组合中有农作物花粉,反映人类农耕活动对聚落及其周围孢粉组合有明显的影响;文化层样品的孢粉组合显示,卡约文化早期阶段,禾本科植物花粉明显多于晚期阶段,可能反映了卡约文化时期(约公元前1200-800年)农业在社会经济中地位逐步下降的过程;孢粉组合还显示,与现代丰台村相比,卡约文化时期,聚落周围有更多的禾本科植物生长,人类可利用的植物资源比现代丰富。研究结果将有助于综合研究西北地区青铜时代环境与人类文化的关系。  相似文献   
977.
博物馆环境中的粉尘对文物有不利的影响,需了解其成分和来源,为文物的保存环境的选择提供科学的数据。为此,采用红外光谱、X射线衍射、扫描电镜等手段对河南博物院空调滤网上的粉尘进行了成分分析和形貌分析。分析结果显示,粉尘包括无机的硅酸盐物质和各种纤维。分析结果说明,博物馆展室这样的人工环境中仍然含有对文物有危害的因素,而空调措施对去除粉尘具有一定的作用。  相似文献   
978.
张梦 《旅游科学》2006,20(5):8-12
本文在对区域旅游业竞争力现有研究进行回顾和评述的基础上,结合区域旅游业发展的实践和竞争力发展特征,构建起了区域旅游业竞争力的二维度分析模型,并对模型建构的思路和内容进行了分析和探讨。  相似文献   
979.
Self-Citation in Archaeology: Age, Gender, Prestige, and the Self   总被引:1,自引:0,他引:1  
Citation analyses in archaeology have detected prestige tactics, shifts in research agendas, and patterns of gender differentiation. This paper focuses on self-citation in archaeology and systematically analyzes the factors that affect rates of self-citation. Self-citation rates in archaeology are significantly higher than in socio-cultural anthropology but are average for a social science with interdisciplinary ties to the physical sciences. Self-citation correlates weakly with the gender of the citing author and the geographic and thematic focus of research, but correlates strongly with the age of the author. Additional analyses reveal partial evidence for the use of self-citation as a prestige tactic. The paper concludes with a discussion of citations to writers close to the author (mentors, friends).  相似文献   
980.
This study uses GIS and spatial modelling to relate voting outcomes at the 2001 federal election for polling booths across Australia with the socio‐economic characteristics of polling booth catchment areas. The data and analysis used are more detailed and comprehensive than previous studies. It is conducted at a fine level of spatial disaggregation across the whole nation to examine voting outcomes for both major and minor political parties. Because the aim of the paper is to distinguish voting outcomes between political parties rather than to predict voting outcomes for particular political parties, a discriminant analysis is used rather than regression analysis. The statistical discriminant analysis identifies two main socio‐economic dimensions that are able to predict polling booth outcomes with a relatively high degree of accuracy. That analysis shows how, at the 2001 federal election, the middle ground, in terms of socio‐economic characteristics, was being claimed by the Liberal Party, Country Liberal Party, The Greens, and, to a lesser extent, by the Australian Labor Party. However, the Australian Democrats, National Party and One Nation had more distinctive constituencies, with the National Party and One Nation Party competing for areas with similar socio‐economic characteristics. Using GIS mapping tools, examples of actual and predicted polling booth voting outcomes are given, along with selected socio‐economic characteristics of booth catchments.  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