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   592篇
  免费   20篇
  2024年   1篇
  2023年   9篇
  2022年   13篇
  2021年   5篇
  2020年   12篇
  2019年   20篇
  2018年   21篇
  2017年   21篇
  2016年   22篇
  2015年   15篇
  2014年   18篇
  2013年   57篇
  2012年   41篇
  2011年   27篇
  2010年   34篇
  2009年   24篇
  2008年   33篇
  2007年   31篇
  2006年   22篇
  2005年   34篇
  2004年   25篇
  2003年   19篇
  2002年   21篇
  2001年   24篇
  2000年   18篇
  1999年   8篇
  1998年   8篇
  1997年   5篇
  1996年   3篇
  1995年   6篇
  1994年   4篇
  1993年   2篇
  1992年   4篇
  1991年   1篇
  1990年   1篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
排序方式: 共有612条查询结果,搜索用时 62 毫秒
1.
本文对青海古代各历史时期的文化遗址及文物进行了分析与探讨,提出了青海古代文化遗址有着分布的集中性、石器时代的完整性以及多元结构的民族文化特点;论证了以上特点是由地理环境及历史的各民族文化活动所致。  相似文献   
2.
迄今已有2 700多年历史的铜鼓,是南方少数民族地区节日、喜庆、兵事、婚丧、祭祀、礼乐等场合使用的一种重器。为了对锈蚀状况做出科学的现状评估,为器物保护修复技术路线的制定和修复工作的开展提供科学指导,对玉林市博物馆馆藏7件铜鼓综合运用了体视显微镜、金相显微镜、激光显微拉曼光谱仪(RS)和环境扫描电镜及能谱仪(ESEM-EDAX)等仪器进行了金相组织和合金成分分析以及锈蚀产物的分析。分析结果显示:7件器物皆为泥范铸造成型,未见热、冷加工处理现象。7件铜鼓皆为铅锡青铜合金,总体呈低锡高铅的特点。组织形态呈典型α固溶体树枝晶偏析,锡含量处于6.0%~12.2%,分布较为集中,处于中等含量水平(5%≤Sn15%);铅含量处于14.4%~28.2%,铅含量普遍较高且分布较为集中,处于中高铅(10%≤Pb15%)和高铅含量(Pb≥15%)水平,合金中高铅含量配比应为工匠有意合金配比选择;铜鼓的腐蚀类型为α固溶体富铜相优先腐蚀,保存环境主要是富氧、少氯,铜鼓表面锈蚀产物主要为绿色孔雀石和蓝色蓝铜矿以及氧化物,有少量白色白铅矿。在保护修复工作中对于这些无害锈可保留,不予处理,并注重防氧。对于铜鼓表面夹杂泥土,需进行清洗去除。研究结果可为器物保护修复技术路线的制定和修复工作的开展提供科学指导。  相似文献   
3.
Many factors governed the penetration efficacy of prehistoric projectile weaponry. Archaeologists broadly focus their efforts on understanding the effect of stone weapon tips because these specimens are often the only part of the weapon system that survives in the archaeological record. The tip cross-sectional area (TCSA) and perimeter (TCSP) of stone weapon tips have been shown to correlate with target penetration depth. Here, using results from both static and dynamic penetration testing, we compare TCSA and TCSP against other tip geometry metrics: lateral surface area (LSA) and volume (V). Our analyses broadly show that using a single-point geometry metric evaluated at multiple locations along the length of the point, or using multiple geometry metrics evaluated at a single location, better predicts required energy than using a single-point geometry metric evaluated at a single location. Our results also show that in the case where a single geometry metric evaluated at multiple locations is used LSA provided the most robust prediction models. Finally, our results show that for the case where all geometry metrics evaluated at a single location are used the location that provides the most robust prediction model is dependent on how far the point penetrated the target.  相似文献   
4.
本文采用因子生态分析方法剖析多伦多都市区的居住空间结构。主成分分析表明,家庭构成、年龄构成、职业构成是形成城市居住分异的主要因素。聚类分析表明,家庭构成和年龄构成的分异呈同心园格局,职业构成的分异呈扇形格局。形成这种居住分异格局的机制包括动力机制、管理机制和行为机制三个方面。  相似文献   
5.
位于四川省阆中市的大像山石窟,主要开凿于中晚唐和宋代,明清时期也有少量开凿。现有37龛,以方形龛、外方内圆拱形龛及圆拱形龛为主,方形龛最为多见。龛楣大多无装饰,雕刻简单。题材主要有弥勒佛、七佛、千佛、观音、天王、力士、经幢及舍利塔等。造像组合较少,以单身造像为多。阆中独特的地理位置,使得大像山石窟兼具广元、巴中两地石窟的特点,其丰富的内容为巴蜀佛教石窟寺的深入研究提供了重要的实物资料。  相似文献   
6.
This article examines the wealthier inhabitants of Croydon in the late sixteenth and early seventeenth centuries, focusing on differences in wealth, ownership of property and social relationships. Using wills and subsidy lists, four broad categories of people were identified: gentlemen, yeomen, tradesmen and craftsmen and widows. There was no simple gradation of wealth between these groups; although gentlemen were generally among the richest subsidy payers, yeomen and tradesmen could also figure. In terms of social relationships and the ownership of property, there were differences. Gentlemen tended to marry within their own social group, appoint other gentlemen as overseers in their wills and were more likely to own land outside Croydon. The social relationships of yeomen and tradesmen/craftsmen were more focused on the town itself, as were their land purchases. Two groups of individuals can therefore be seen, not one homogenous entity as some scholars have argued.  相似文献   
7.
A sailing replica based on the archaeological remains and structural analysis of the 6th‐century archaic Greek sewn boat Jules‐Verne 9 was built in Marseille as part of the city's European Capital of Culture 2013 programme. Full‐scale reconstruction allowed investigation of specific aspects of the methods used to build a shell‐first, sewn‐plank, and lashed‐frame vessel, as well as learning the gestures and know‐how of the original shipbuilders. The first two seasons of sailing trials, including short journeys in the Bay of Marseille and longer, coast‐hopping expeditions, reflecting the uses of the original vessel have taken place and are reported here.  相似文献   
8.
ABSTRACT

The employment of timber pegs in timber structure joints is a widespread technology in the field of timber frame building in the United States, where the Timber Frame Engineering Council has published a special Standard to supplement the National Design Specification for Wood Construction. The authors have been studying the possibility of supplementing the Eurocode 5 design formulas, thought for timber joints with metal connectors, with specifications needed for a reliable design when employing timber pegs. The field of application envisaged is that of restoring timber structures and results obtained until now are quite encouraging. In this step of the research, more attention has been paid to deformation process: fir and chestnut samples have been tested to determine their dowel-bearing behavior with steel and ash timber peg while double-shear plane joints made of the same wood species, and fastened with steel as well as timber pegs, have been analyzed.  相似文献   
9.
10.
Historical towers, in particular medieval towers, are an important part of cultural heritage, and their preservation mandates monitoring and detailed analyses of vulnerability under seismic actions as well as of their long-term performance. Certain aspects of structural nature are linked to the masonry behavior as a unilateral material, and other are aspects related to the interaction with soft soil conditions. This study aims to contribute to the aspects of preservation by exploring the role of the soil-structure interaction in predicting the behavior of the structures, with specific reference to the well-documented case history of the medieval Ghirlandina Tower (Modena, Italy). A significant contribution comes from an experimental identification analysis, performed in the presence of ambient vibration. A novel finding is that the soil structure interaction cannot be neglected, in contrast to most published identification analyses that usually assume the structure to have rigid constraint at base.  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