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产业区域集聚是近年学术研究的一个重要问题。本文在总揽国内外现有研究文献的基础上,从理论和实证两个层面对这一论题进行了系统梳理。从理论层面来看,新近兴起的新经济地理学是迄今为止研究产业集聚的主流经济学理论。它在规模报酬递增与不完全竞争市场为特征的理论框架下,引入了外部经济、要素流动、以及路径依赖等因素,来研究产业在地理空间上的集聚与扩散问题。实证层面,本文将近年涌现出的产业区域集聚经验检验归纳概括为五个实证命题,并分别展开回顾。 相似文献
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美国经济遏制战略与高新技术转让限制 总被引:4,自引:0,他引:4
50— 60年代 ,美国经济遏制战略是以禁运战略物资为主 ,从 70年代开始 ,转向以限制高新技术转让为主 ;1 979年《出口管制法》标志着这种转变的完成。在“缓和时代” ,美国经济遏制战略追求的目标是 ,以有限发展东西方贸易换取苏联的政治让步。在“新冷战”时期 ,美国经济遏制战略将打击对象从中国重新转向苏联 ,更重要的是将高新技术转让限制作为迫使苏联“改变国内政治”的重要手段 相似文献
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宋太宗在处理民族问题的具体实践中形成了由"中国一统"、"四夷当置之度外"和"修德以怀远"三大观点支撑的民族关系思想体系.宋太宗的这一思想在不同阶段具有不同的特点,先由"备边通好"转向"图制契丹",再由"图制契丹"转向"联夷攻辽",最终由"联夷攻辽"转向"修德以怀远".宋太宗民族关系思想的演变,既直接影响着当时民族关系思想流派的兴衰,也对宋初疆域的形成产生了不可忽视的影响. 相似文献
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本文根据考古学14C年代数据和考古遗存情况,结合高分辨率的地层和古气候研究资料,分析了河北及京津地区早中全新世文化的时空分布格局以及影响遗址分布的地貌和气候因素。该地区早中全新世文化时间序列为:早期新石器时代文化(10,000~8,800 yr BP)、新石器早中期之间的文化缺环(约8,800~7,300 yr BP)、7,300~6,500yr BP的磁山.兴隆洼.北福地一期三大文化系统并立发展时期以及6,500~6,000 yr BP的前仰韶文化时期。文化序列与气候序列对比发现:文化发展很大程度上受到气候条件的制约。从文化分布空间来看,具有如下特征:首先,早中全新世时期的文化分布在与当时海岸线平行的弧形地带上,这种分布格局与气候和地貌条件有关。在排除了地势高亢和海侵影响地区后,太行山东麓到古海岸线之间的弧形地带成为最佳选择。其次,从遗址分布高度来看,当时人仍居住在较高地貌面上,海侵及众多湖沼阻止了人类向东部平原腹地迈进的步伐。 相似文献
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Ancient DNA analysis of desiccated wheat grains excavated from a Bronze Age cemetery in Xinjiang 总被引:1,自引:0,他引:1
Chunxiang Li Diane L. Lister Hongjie Li Yue Xu Yinqiu Cui Mim A. Bower Martin K. Jones Hui Zhou 《Journal of archaeological science》2011
Wheat has been one of the most important crop in Eurasia since the Neolithic period. Understanding the spread of wheat cultivation is crucial to understanding the spread of agriculture as a whole and the interactions between prehistoric populations across the Eurasian continent. However, the routes by which wheat cultivation spread eastwards have been poorly understood to date, due to the scarcity of plant remains recovered from archaeological sites. Desiccated wheat grains excavated from the Xiaohe cemetery in Xinjiang, and dated to the early Bronze Age, show excellent DNA preservation. Here we present an ancient DNA (aDNA) analysis of wheat (Triticum sp.) grains excavated from Xiaohe and provide the first definitive evidence for bread wheat in China during the Bronze Age. The nuclear ribosomal DNA internal transcribed spacer regions (ITS1 and ITS2) and the intergenic spacer region (IGS) were amplified. The IGS region within the D genome of wheat has a 71 bp insertion that is absent from corresponding regions in the A and B genomes. The results showed that the Xiaohe wheat showed most sequence similarity to hexaploid bread wheat (Triticum aestivum), including the characteristic insertion into the D genome. The presence of bread wheat at the Xiaohe cemetery is discussed in relation to it having spread into Xinjiang by the Bronze Age, providing new insight into the origins of bread wheat in East Asia. 相似文献
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Low‐temperature vitreous materials fluxed with lead (and barium) appeared in the early Warring States period (c.fifth century bce ) in ancient China. A range of lead vitreous products fluxed with the same agent, including faience/glass beads, glazed pottery and Chinese blue (purple) pigment, were developed subsequently. This study carries out scientific analysis of six vitreous beads unearthed from the Zhaitouhe cemetery site in northern Shaanxi dating to the early and middle Warring States period to investigate their chemical composition, microstructure and coloration. The lead (and barium) vitreous beads identified here are some of the earliest lead vitreous materials discovered in China so far, and therefore important for the study of the development of lead vitreous technologies in ancient China. This paper also points out that it is meaningful to evaluate the lead glass, glazed pottery and barium copper silicate pigments as a whole technological assemblage given their close relationships. 相似文献
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笔者在查阅济南市博物馆藏高凤翰作品资料时,发现了两对孪生作品,几乎一模一样。在书画鉴定中最重要的方法就是比较,笔者就将这些孪生作品进行排列对比总结,从中发现高凤翰绘画的特点以及真伪作品的区别。现将这些孪生作品排列一下,为了叙述方便,将济南市博物馆的藏品简称"济博本",将拍卖公司拍出的作品简称"拍卖本"。图1《素袜凌波图》题款:"素袜凌波之图"。壬子写,丁巳补题。南阜。荷花荷叶五尺长, 相似文献
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东盎格利亚是英格兰东部一个相对独立的地理单元,作为中世纪较为发达的传统农业区,它具有与典型封建农业区不同的一些经济社会特点。在英国从农业社会向工业社会转型的进程中,东盎格利亚根据自身的资源、传统和优势,不断探寻本区域的经济发展方向,走了一条"传统农业→原工业化→商品化农业"的曲折道路,最终找到了较为适当的经济定位。东盎格利亚的这一转型既反映了英国崛起过程的复杂性,也体现了农业社会向工业社会转变道路的多样化。 相似文献