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   988篇
  免费   19篇
  2024年   2篇
  2023年   5篇
  2022年   11篇
  2021年   27篇
  2020年   29篇
  2019年   16篇
  2018年   14篇
  2017年   18篇
  2016年   19篇
  2015年   25篇
  2014年   11篇
  2013年   60篇
  2012年   49篇
  2011年   83篇
  2010年   79篇
  2009年   100篇
  2008年   81篇
  2007年   76篇
  2006年   86篇
  2005年   62篇
  2004年   25篇
  2003年   14篇
  2002年   21篇
  2001年   18篇
  2000年   26篇
  1999年   11篇
  1998年   10篇
  1997年   6篇
  1996年   6篇
  1995年   2篇
  1994年   4篇
  1993年   3篇
  1992年   5篇
  1991年   1篇
  1990年   2篇
排序方式: 共有1007条查询结果,搜索用时 15 毫秒
1.
Palace lanterns were important and highly visible decorations in the imperial palace in Beijing, China, during the Qing dynasty (1636–1912). Most lanterns had colourful tassels made of fibres. The study performed a comprehensive investigation of the materials and dyes used for palace lantern tassels preserved in The Palace Museum, Beijing. Eight samples with different colours, including yellow, green and red, from five palace lanterns were analysed. By using ultra-performance liquid chromatography combined with time-of-flight mass spectrometry, the compositions of the dyes were identified quickly, and thus the dyes' origins were explored. A X-ray fluorescence spectrometer assisted in the detection of whether a mordant was used during the dyeing process. As a result, the tassels were all made of silk, discovered through the use of microscopic observation and micro-Fourier transform infrared spectrometry analysis. Different dyeing techniques were found in these tassels: yellow tassels were dyed by cork tree or turmeric by a direct dyeing method; greens were dyed by pagoda bud with an iron mordant, or by the combination of cork tree and indigo using multi-dyeing method; and red tassels were coloured with different acid red industrial dyes. These results provide valuable data for the conservation of ancient textile tassels and contribute to the investigation of other hanging tags.  相似文献   
2.
侯深 《史学集刊》2021,(2):72-85
堪萨斯城崛起于密苏里河与堪萨斯河的交汇处,是一个依赖大平原的农牧业所建立的美国中西部都市。铁路助力资本打破了自然的种种限制,令大平原转化为堪萨斯城的腹地。虽然征服自然以实现城市经济的永续增长,一直是堪萨斯城,乃至整个资本主义制度与经济文化的野心,但是成为腹地并不意味着自然完全受到资本与技术力量的操纵,更不意味着自然的消失。作为一种自发的、独立的力量,自然以其丰饶奠定城市发展的基础,也以其极限挑战着城市发展的野心和规划。在堪萨斯城的故事中,1930年代的尘暴与1951年的洪水以灾难的形式迫使这个城市去适应新的生态现实。  相似文献   
3.
吴密 《文献》2021,(2):167-176,F0002
《河南卢氏曹先生教泽碑文》是鲁迅为曹靖华之父曹植甫撰写的一篇碑文,碑文原稿连同附带的一封书信一直没有被外界发现和披露。近日碑文和书信手稿首度现身公众视野,从其内容、特征和相关记载分析,可以确定为鲁迅手书原稿无疑。这两件手稿的发现,为我们对比研究《教泽碑文》的原稿、清稿、初刊本、文集本、全集本等诸多版本提供了重要依据,解决了1986年所立碑文石刻文字的底本问题,同时也廓清了包括曹靖华本人在内对这篇碑文手稿回忆的不准确之处。  相似文献   
4.
利用三维扫描技术获取兵马俑残片的三维点云数据,结合Geomagic Studio和Hypermesh建立高精度的兵马俑足踝残片三维实体网格模型。通过基于ABAQUS的重力作用下的有限元分析,研究足踝部分的Von Mises应力和变形特征,以确定足踝处的受力薄弱部位。为进一步探究模型各残片的最佳点云简化比例,采用点云简化模型进行相同工况的有限元分析,以验证点云简化的可靠性。结果表明:结构在重力作用下可保持安全稳定的状态,相对薄弱部位位于左腿足踝处;对于大部分残片,其最佳简化比例在60%~70%,简化后可有效缩短模型实体化处理时间;采用简化模型得到的有限元结果,其最大Mises应力相比于原始模型的误差小于15%,且应力云图和变形图形状接近,模型简化具有可靠性。  相似文献   
5.
聚醋酸乙烯酯(PVAc)乳液是常见的彩绘类文物保护材料。采用激光粒度仪、热重/差热分析、红外光谱、X-射线衍射、扫描电镜、透射电镜等表征了PVAc乳液的粒径以及胶膜的热稳定性、结构和形貌;采用粘度计、表面张力仪、pH计、电导率仪等研究了乳液浓度与其粘度、表面张力、pH、电导率的关系;通过冻融、室温-高温放置、离心分离研究了乳液的稳定性;同时用PVAc乳液对模拟起甲和酥碱的壁画进行了修复。结果表明,PVAc乳液粒径呈双峰分布,小粒子的平均粒径为380 nm,大粒子的平均粒径为5.85μm;乳液胶膜为非结晶物质,胶膜热重的最终质量残留为1.54%,335℃出现放热峰。PVAc乳液的电导率随浓度的增大而增大,pH随浓度的增大而下降;相同温度下表面张力随浓度的增大而基本呈现低浓度下降,高浓度上升的趋势。相同浓度下,表面张力随温度升高而无显著变化,表明PVAc乳液的表面张力受温度变化影响不大。相同温度下,乳液粘度随浓度的增大而增大;相同浓度下,乳液的粘度随温度的升高而降低。冻融、离心分离和不同温度下静置发现,该乳液出现分层。用该乳液对模拟起甲和酥碱壁画修复后,再分别老化20个循环和12个循环,发现颜料层再次空鼓、起甲。综合分析,说明实验中所使用的该种PVAc稳定性和抗老化能力较弱,在修复彩绘类文物中应慎重选择PVAc的种类,综合考虑PVAc的使用浓度、环境因素对其性能的影响,以达到最佳使用效果。  相似文献   
6.
7.
本文论述了图们江地区国际性城市体系建设的必要性,提出了城市体系等级结构、职能结构和空间结构的构建设想及管理原则,并初步估算了城市体系发展各项基础设施建设及投资规模。  相似文献   
8.
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   
9.
ABSTRACT

The emerging problem of left-behind children has attracted mounting academic and policy attention. Prior studies primarily cast light on left-behind children’s education, health, and behavior, while their subjective well-being is much less understood yet. Based on a nationally representative sample of rural children aged 10–15 in 2014, we examine the impacts of different types of parental migration on children’s subjective well-being and how these affects vary between boys and girls. The results show that parental migration is a double-edged sword: children from both-parent migrant families report compromised life satisfaction and relationship quality compared with those in integral families, and mother-only migration significantly lowers children’s subjective health. On the flip side, father-only migration enhances children’s aspiration for attaining college, an encouraging effect that is even stronger than that of parental education and family income. These effects are heterogeneous by children’s gender: boys seem to be more susceptible to the disruptive effects of both-parent migration; mother-only migration effectively promotes girls’ educational aspiration while father-only migration promotes boys’. This study portrays a comprehensive image of left-behind children. Relaxation of hukou restriction, equal access to education, and revitalization of rural economies are imperative to improve the well-being of left-behind children.

Abbreviations: LBC: Left-behing children; SWB: subjective well-being  相似文献   
10.
1866年《南部宅地法》为了解决美国黑人自由民的土地问题制定了相对有利的宅地申请条件。然而由于缺乏申请宅地以及从事农业生产的初始资本和其他借贷来源,美国联邦政府也没有在借贷方面为宅地申请者提供相应的扶持,绝大多数黑人自由民并没有利用《南部宅地法》提供的有利条件转变为独立的小农场主。这是1866年《南部宅地法》失败的深层次原因。  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