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   5796篇
  免费   204篇
  2024年   20篇
  2023年   97篇
  2022年   98篇
  2021年   96篇
  2020年   237篇
  2019年   215篇
  2018年   243篇
  2017年   231篇
  2016年   255篇
  2015年   161篇
  2014年   180篇
  2013年   619篇
  2012年   382篇
  2011年   345篇
  2010年   274篇
  2009年   308篇
  2008年   323篇
  2007年   368篇
  2006年   307篇
  2005年   290篇
  2004年   186篇
  2003年   170篇
  2002年   173篇
  2001年   84篇
  2000年   113篇
  1999年   34篇
  1998年   20篇
  1997年   19篇
  1996年   16篇
  1995年   14篇
  1994年   17篇
  1993年   19篇
  1992年   9篇
  1991年   9篇
  1990年   5篇
  1988年   1篇
  1987年   1篇
  1986年   1篇
  1985年   8篇
  1984年   6篇
  1983年   12篇
  1982年   9篇
  1981年   5篇
  1980年   6篇
  1979年   9篇
  1978年   5篇
排序方式: 共有6000条查询结果,搜索用时 15 毫秒
31.
The archaeological record of prehistoric Cyprus is rich, diverse, well-published, and frequently enigmatic. Regarded by many as a bridge between western Asia and the Aegean, Cyprus and its past are frequently seen from scholarly perspectives prevalent in one of those two cultural areas. Its material culture, however, differs radically from that of either area. Apart from the early colonization episodes on the island (perhaps three during the pre-Neolithic and Neolithic), evidence of foreign contact remains limited until the Bronze Age (post-2500 B. C.). This study seeks to present the prehistory of Cyprus from an indigenous perspective, and to examine a series of archaeological problems that foreground Cyprus within its eastern Mediterranean context. The study begins with an overview of time, place, and the nature of fieldwork on the island, continues with a presentation and discussion of several significant issues in Cypriot prehistory (e.g., insularity, colonization, subsistence, regionalism, interaction, social complexity, economic diversity), and concludes with a brief discussion of prospects for the archaeology of Cyprus up to and beyond 2000.  相似文献   
32.
古铜矿遗址围岩表层有害生物的防治   总被引:3,自引:0,他引:3  
铜绿山古铜矿遗址地处长江中游地区、空气湿度大、围岩表层有害生物成片生长蔓延,对遗址的长期保护造成极大威胁。对此采取了改变遗址的环境条件、喷涂消杀药品的方法,消除了围岩表层有害生物的危害。经过一年半的观察表明该方法是可行的。  相似文献   
33.
西安城墙东门箭楼砖坯墙体风化因素研究报告   总被引:2,自引:2,他引:0  
论述了西安城墙东门箭楼的文化背景,实地考察了风化外状,并对风化外状进行了分类测试。通过对砖坯墙体材料进行化学全分析、X-射线衍射分析、吸水率测定(含他和系数)、冻融实验、泛霜实验、环境污染与水文气象监测资料的分析,研究了东门箭楼砖坯墙体不同风化外状的风化因素,同时对现代修缮用砖的理化性能及质量进行了评估。结果表明,温度的交替变化、水的冻结与融化使得砖坯裂解成碎块;干湿引起可溶盐的结晶与潮解以及自然界中的雨水、地面水或地下水、污染气体等通过溶解、水化、水解、碳酸化、氧化等方式,使得砖坯墙体表面酥碱粉化。同时说明研究适用于古建筑修缮使用的抗风化仿古青砖是当务之急。  相似文献   
34.
浑仪、简仪(以下简称两仪)在高PH、大气污染和日晒雨淋环境中的腐蚀是一种动态加速腐蚀过程。采用合成的双唑胺铜缓蚀剂和有机硅改性的甲基丙烯酸树脂,并分别复配成协同缓蚀剂群和含有增效稳定剂的封护剂。采用这两种材料和脱水后再防护的工艺,使带锈防护后的浑仪、简仪的腐蚀低于无污染大气中的速率。用电化学方法评价了防护技术的可行性,根据腐蚀与人工老化试验结果讨论了防护材料性能与腐蚀环境和带锈防护的关系,采用XPS分析方法探索了双唑胺比BTA更适用于两仪防护的原因。  相似文献   
35.
明墓出土的历书,粘连固结成块,脆硬易于折断。通过实验分析研究,探明其主要原因可能是木质素选择性地吸附的钙铁离子与蛋白质的分解物形成复杂物质,沉积在纸上,渗入书内所致。故揭取该历书的关键是去除钙离子,EDTA二钢,碱性过氧化氢、气相二氧化硅等的分步处理,使脆硬的纸张软化,再逐页分离揭取,然后再去除色素沉淀物,终于恢复了书的原貌。  相似文献   
36.
The chronology of the period is briefly considered in the light of the dendrochronological results which have appeared in recent years. Patterns of settlement history in different parts of the area are then examined, and it is suggested that in some of them the late fourth millennium was a period of population decline which was not reversed until the Early Bronze Age, 1000 years later. Detailed information about specific local occupation patterns is provided by recent work on the circum-Alpine lake villages. Changes in cultural patterns during the period, especially the appearance of the Corded Ware, are discussed and explanations of them reviewed. It is argued that changing patterns of gender relations were a major feature of the period, linked to processes which eventually led to the development of small-scale chiefdoms. The development of copper and bronze metallurgy and its connection to these processes are discussed.  相似文献   
37.
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   
38.
Empirical aspects of the movement of strontium through the food chain suggest that the level of bone strontium can be used as an indicator of the percentage of meat in human diet. In general, skeletal remains from agricultural peoples are expected to have high bone strontium levels relative to hunter-gatherers from the same geographical region because plants contain relatively higher amounts of strontium when compared with animal products. The results of the study described in this paper, however, indicate that the inclusion of molluscs as a component of the diet may produce the opposite of the expected strontium values. Burials from an Archaic (c. 2500 BC) hunting-gathering population excavated from Luo25, an archaeological site in northern Alabama, USA, exhibit a mean bone strontium level ( atomic absorption; neutron activation) that is higher than the mean level from an agricultural Mississippian (c. AD 1400) population ( atomic absorption; neutron activation) that was buried at the same site. The samples were analysed by two techniques (atomic absorption spectrometry and neutron activation analysis) and the results compared favourably; therefore, the results can be accepted as valid rather than being due to technique error. We propose that the ingestion of molluscs, whose meat is known to contain large amounts of strontium, has produced this reversal from expected results.  相似文献   
39.
About 200 analyses have been made on late Roman and Sassanian silver objects using energy-dispersive X-ray fluorescence. This has shown that the main feature of the composition of the silver throughout the period and across the geographical area studied was towards high fineness (average silver percentage about 95%). Compositional differences are found between Roman and Sassanian silversmiths' products for the elements copper and lead. Much of the material analysed came from hoards, and using a statistical technique on the analytical data (Discriminant Analysis) broad compositional differences between hoards were found to emerge. The use of different compositions of silver for different joined parts of a single object are discussed.  相似文献   
40.
The bodies and glazes of 27 early Western Zhou proto‐porcelain samples from Yejiashan cemetery, Hubei Province, were analysed using LA‐ICP–AES, SEM, XRD, a thermal expansion instrument and other analytical methods. The results indicated that the bodies of all samples were characterized by high silicon and low aluminium, and were made with porcelain stone raw materials found in the south of China. The glazes are typical of high‐temperature calcium glazes of the CaO (MgO) – K2O (Na2O) – Al2O3 – SiO2 series, with relatively high Mn and P content, which was probably caused by the addition of plant ashes. The physical properties and phase compositions of Yejiashan proto‐porcelain show that firing processes were still in the early stages of development in ancient China. Multivariate statistical analyses indicated that Yejiashan proto‐porcelain might have come from the Deqing area, in Zhejiang Province. These results provide new archaeological evidence for research on issues related to material flow in the Western Zhou dynasty.  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