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   394篇
  免费   16篇
  2024年   7篇
  2023年   9篇
  2022年   15篇
  2021年   13篇
  2020年   19篇
  2019年   17篇
  2018年   24篇
  2017年   17篇
  2016年   13篇
  2015年   9篇
  2014年   15篇
  2013年   42篇
  2012年   21篇
  2011年   19篇
  2010年   19篇
  2009年   23篇
  2008年   22篇
  2007年   19篇
  2006年   20篇
  2005年   5篇
  2004年   10篇
  2003年   12篇
  2002年   6篇
  2001年   11篇
  2000年   6篇
  1999年   2篇
  1998年   4篇
  1997年   5篇
  1994年   2篇
  1993年   1篇
  1990年   1篇
  1983年   1篇
  1979年   1篇
排序方式: 共有410条查询结果,搜索用时 31 毫秒
21.
Microscopy, mass spectrometry and X-ray diffraction methods were used to analyse 415 samples of natural and archaeological flint from Sierra de Atapuerca (Burgos, Spain) in order to define the different types from Neogene and Cretaceous formations in the study area, infer their genetic context and ascertain the supply sources used by hunter-gatherers who exploited this area in the Upper Pleistocene. A statistical classification model was also designed using linear discriminatory analysis and support vector machines which permitted the differentiation of the flint on an age basis.  相似文献   
22.
In Roman and Byzantine times, natron glass was traded throughout the known world in the form of chunks. Production centers of such raw glass, active from the 4th to 8th century AD, were identified in Egypt and Syro-Palestine. However, early Roman primary glass units remain unknown from excavation or scientific analysis. The ancient author Pliny described in 70 AD that besides Egyptian and Levantine resources, also raw materials from Italy and the Gallic and Spanish provinces were used in glass making. In this study, the primary provenance of 1st–3rd century AD natron vessel glass is investigated. The use of combined Sr and Nd isotopic analysis allows the distinguishing and characterizing of different sand raw materials used for primary glass production. The isotope data obtained from the glass samples are compared to the signatures of primary glass from known production centers in the eastern Mediterranean and a number of sand samples from the regions described by Pliny the Elder as possible sources of primary glass. Eastern Mediterranean primary glass has a Nile dominated Mediterranean Nd signature (higher than −6.0 ? Nd), while glass with a primary production location in the western Mediterranean or north-western Europe should have a different Nd signature (lower than −7.0 ? Nd). Most Roman glass has a homogeneous 87Sr/86Sr signature close to the modern sea water composition, likely caused by the (intentional) use of shell as glass raw material. In this way, strontium and neodymium isotopes now prove that Pliny's writings were correct: primary glass production was not exclusive to the Levant or Egypt in early Roman days, and factories of raw glass in the Western Roman Empire will have been at play.  相似文献   
23.
代林静 《攀登》2008,27(4):200-202
在新时期,新闻工作者肩负着“以科学的理论武装人,以正确的舆论引导人,以高尚的精神塑造人,以优秀的作品鼓舞人”的历史使命。所以,作为一名新闻工作人员必须始终保持清醒的头脑,不断提高自己的业务素质,以较强的政治鉴别力和政治敏锐性确保新闻舆论导向的正确。  相似文献   
24.
文物保护技术新世纪展望   总被引:1,自引:0,他引:1  
徐飞 《东南文化》2002,(7):93-96
新世纪中有机氟材料将在物保护领域广泛应用,纳米材抖将从物保护新材料中脱颖而出,抑制微生物腐蚀将成为物保护工作重中之重,互联网将在物保护工作中发挥巨大效率。  相似文献   
25.
A range of factors, including consumer concerns about food safety, the growing popularity of rural tourism and policy initiatives to promote endogenous rural development, is converging to promote a relocalization of food production and service provision, especially in those regions marginalized by the globalization of the food supply system. The recent outbreak of foot and mouth disease in the UK has starkly illustrated the fragility of localized systems which depend heavily on consumers travelling to them. Within such a context, the importance of successful marketing strategies has become even more apparent. This paper reports on a questionnaire survey which investigated promotional and marketing strategies among a diverse range of producers and service providers in marginal agricultural areas of the EU. The findings suggest that many producers are situated towards the "formal" end of a marketing continuum, whereby ability to promote quality products and services (QPS) lies with a range of intermediaries. This raises doubts about the future economic benefits of QPS, should current marketing structures persist. The discussion offers critical reflections on interdisciplinary and international research of this nature, and advocates further theoretical and methodological development in order to explore in more depth many of the aspects raised in this exploratory investigation.  相似文献   
26.
Companhia Aurifícia is located in Porto, Portugal, and was founded in 1864. It was a pioneer factory in the industrial production, casting, rolling, and stamping of metallic objects and laboured for about 150 years, in areas as jewelry, manufacture of parts in silver and gold or the production, and casting of various metals. In 1866, it began laboring in Rua dos Bragas, its present location, and in 2003 ceased all activities.Companhia Aurifícia is an industrial complex including several buildings, all located in the same block. It is a precious example of the industrial architecture in Porto, where the still existent retaining walls, structures, machinery, and decorative elements make it one of the last examples of 19th century industrial life of the city.This article aims to evaluate the safety condition of one of the buildings included in this industrial complex, in order to propose the necessary strengthening interventions.  相似文献   
27.
Studies of the ‘geographies of students’ have become increasingly prevalent across the social sciences and are particularly concerned with the predilection for young UK University undergraduates to be mobile in their institutional choice. A more recent focus within this work has been upon student identities, with attention given to how the spaces to which students move and in which they settle can have both positive and negative consequences for the evolution of the student identity, and how such identities are often framed within the context of social activities; learning environments; friendship networks; or other sociocultural factors. This paper contributes to these discussions by considering the role of student accommodation – a site which often remains on the periphery of discussions of student identities – in offering students opportunities to construct, adapt and manage their student identities. This adds to the important contemporary geographies of student accommodation, which are currently debating, among others, purpose-built student accommodation and the broad housing ‘careers’ and strategies of students. In contrast, this paper explores the micro-geographies of student accommodation (and more specifically, the bedroom) to highlight its value in providing young, mobile students with an anchor within which they can draw together their learner, social and domestic dispositions into one geographical location.  相似文献   
28.
化学材料在石质文物保护中的应用   总被引:1,自引:0,他引:1  
综述了目前石质文物保护中所用化学材料的种类、特点及应用,探讨了一些在石质文物保护中有发展潜能的化学材料。有机硅材料、纳米材料和仿生材料具有较好的应用前景。深入研究保护材料与石材的相互作用的微观机理,对于开发适用的石质文物保护材料是非常重要的。  相似文献   
29.
李兆中  甄峰 《人文地理》2019,34(6):53-61
在当前我国社会经济转型的背景下,城市生活空间质量成为居民、学界与政府关注的焦点。采用多源数据,拓展了已有城市生活空间质量的评价维度与评价方法,从舒适性、便利性、健康性、安全性、社会性五个维度构建了评价指标体系,并通过GIS空间分析方法,以南京为例进行了生活空间质量评价并识别其空间分布规律。实证分析表明:①南京的城市生活空间质量存在着明显的空间分异。高质量生活空间呈现明显的等级集聚特征,主中心位于核心区周边1-3 km的圈层,低质量生活空间总体分布较为分散。②在构成生活空间质量的五个维度中,舒适性和社会性的发展质量呈现由城市中心向外围递增的趋势,便利性的发展质量呈现由城市中心向外围递减的趋势,健康性受城市环境质量分布趋势的影响,呈现由西北向东南递减的趋势,安全性的高值集聚不显著而低值集聚于城市中心区。  相似文献   
30.
李彬  韩增林  马慧强 《人文地理》2015,30(3):111-117
基于基本公共服务的内涵,从教育服务、文化服务、卫生服务、基础设施服务、社会保障服务、生态环境服务和信息服务7个方面构建了基本公共服务质量评价指标体系,运用熵值法对2003-2011年辽宁省城市基本公共服务质量进行综合测度,并以此为变量,利用差异系数和基尼系数对辽宁省各市基本公共服务质量差异的演变过程与空间格局进行定量分析。结果发现:辽宁省各市基本公共服务质量整体为上升的趋势,表现出较为明显的规模特征,沈阳市和大连市两极突出;2003-2011辽宁省城市基本公共服务质量区域差异总体扩大的基础上,呈现先扩大后缩小的演变趋势,且以文化服务、卫生服务和基础设施服务的差异为主;空间上,公共服务质量空间提升极化作用不断增强,表现为不断向"沈阳-大连、盘锦-本溪"的"十字"轴线紧靠。  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