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   1531篇
  免费   94篇
  2024年   9篇
  2023年   40篇
  2022年   19篇
  2021年   19篇
  2020年   64篇
  2019年   77篇
  2018年   89篇
  2017年   84篇
  2016年   72篇
  2015年   59篇
  2014年   62篇
  2013年   196篇
  2012年   119篇
  2011年   87篇
  2010年   90篇
  2009年   77篇
  2008年   86篇
  2007年   77篇
  2006年   67篇
  2005年   30篇
  2004年   18篇
  2003年   28篇
  2002年   20篇
  2001年   12篇
  2000年   19篇
  1999年   10篇
  1998年   6篇
  1997年   7篇
  1996年   7篇
  1995年   5篇
  1994年   4篇
  1993年   7篇
  1992年   3篇
  1991年   1篇
  1990年   2篇
  1988年   1篇
  1987年   1篇
  1985年   7篇
  1984年   6篇
  1983年   8篇
  1982年   7篇
  1981年   5篇
  1980年   5篇
  1979年   9篇
  1978年   4篇
排序方式: 共有1625条查询结果,搜索用时 15 毫秒
21.
The original fineness of coins is very important information that can help us to understand the commercial situation in a wide historical context. This paper deals with a comparison of analytical methods suitable for the evaluation of the actual and original fineness of coins based on a detailed case study of a medieval coin sample. Both non‐destructive (i.e., scanning electron microscopy/energy‐dispersive X‐ray spectroscopy, X‐ray fluorescence, atomic force microscopy and hydrostatic weighing) and destructive (i.e., inductively coupled plasma – mass spectrometry and the Volhard titration method) techniques were used. The original fineness can be also deduced from knowledge of the internal structure of the coin (limited miscibility of copper and silver). A new analytical method based on a combination of a micrograph of the metallographic cross‐section with consequent image analysis was developed for determination of the original fineness. The proposed approach is relatively simple and provides reliable values. Sample heterogeneity and its impact on the determination of fineness are also discussed.  相似文献   
22.
This paper re‐analyses a considerable corpus of glass from the Late Bronze Age site of Nuzi, found near Kirkuk in Iraq. SEM–WDS and Sr and Nd isotopic analysis were applied, in addition to cataloguing the glass. The work showed that the glass technology at Nuzi was subtly different from contemporary Egyptian sites, using different ways of opacifying and working glass. At least two, perhaps three, Near Eastern production sites are postulated. The range of glass colours and the skill of their application at Nuzi was perhaps not on a par with the Egyptian sites. This led to a reconsideration and review of the accepted wisdom that the Near East is the source of the innovation that is glass‐making. This opinion is based on limited textual and iconographic sources and is dominated by an erroneous early date for a very developed Nuzi glass industry along with a few finds of glass vessels in early contexts. Some of this evidence has now been at least questioned, suggesting that glass‐making in Egypt, at least as early as the middle of the 15th century bc , and probably earlier, is no later than that in the Near East. It is argued that it is far from clear that the Near East was the source of the innovation and that a more cautious approach would better fit the evidence.  相似文献   
23.
24.
ABSTRACT

Geographers interested in how entrepreneurs perceive locational environments have studied their mental maps in several European countries, within the theoretical framework provided by behavioral approach. Such studies have typically employed quantitative techniques, but qualitative studies are relatively new to this line of research. In this article, I examine the mental maps of entrepreneurs in Italy by using a mixture of qualitative and quantitative methods. I present and discuss the qualitative outcomes of this research, focusing in particular on the explanatory location factors and the key influences on the mental maps of entrepreneurs. What emerges is the realization that entrepreneurs are far from being fully rational economic actors, who exploit optimally all information and who are driven only by objective considerations. Rather, their views are also affected by subjective factors, individual’s own insights, commonplaces, stereotypes, and prejudices, particularly with reference to the southern regions of Italy (Mezzogiorno), and of other peripheral areas.  相似文献   
25.
26.
ABSTRACT

A remote archipelago, Hawai'i, offers a plethora of sought after coastal and marine tourism experiences. The same unique marine fauna that draws tourists also makes Hawai'i a major player in the international ornamental aquarium trade. For many residents of Hawai'i, the marine realm is part of their island home and interactions with tourists and tourism activities are a part of everyday life. For many residents, the ocean is an important resource and for some a staple source of livelihood, be it through tourism, fisheries, or the aquarium trade. This variance between extractive and non-extractive marine resource use creates conflicts between stakeholder groups in Hawai'i. This study thematically analyzes public testimony records, which included 1652 individual testimonies, from proposed legislation aimed to establish ‘an aquatic life conservation program in the Division of Aquatic Resources to implement conservation measures, including limited entry areas and certification requirements, to regulate the collection of fish and other aquatic life for aquarium purposes. Public opinions evident in individual testimonies are representative of the disagreement in the literature regarding the stability and health of reef fishes populations in Hawai'i and broader resource-user conflicts. This study aims to better describe the user conflict between stakeholder groups in the marine resources of Hawai'i by exposing themes concerning change in natural environments.  相似文献   
27.
许多出土饱水木质文物因其降解严重、含水率较高,容易在脱水过程中出现不可逆的收缩变形以及开裂现象,从而遭到严重破坏。因此,饱水木质文物脱水方法的研究是文物保护工作中的重要课题。为探究风冷冷冻法对饱水木质文物脱水的效果,以一批无法复原的出土饱水木质文物为研究对象,在对其材种、含水率、基本密度及化学成分进行了测定和分析后,使用一台风冷电冰箱在-18℃条件下对样品进行了风冷干燥脱水处理,记录脱水时间和脱水效果,并分析了该方法的传质传热特点,证明了风冷干燥法用于饱水木质文物的脱水干燥能够取得良好效果,并且具有对文物干预小、适用性广、操作简便、成本低廉等优点,为饱水木质文物的脱水处理提供了一种新的思路。  相似文献   
28.
Alongside the institutionally constructed European identity, research shows that insights into citizens’ sense of belonging are valuable as well in assessing questions of identity. The tendency to conflate European identity with EU identity has spurred debates about the components that underlie European identification. The online subsidiarity adopted by the EU through e-platforms has allowed for a new form of citizenship where e-citizens (de)legitimate the issues under debate. This article examines the contents of European and national identities in the e-debaters’ comments posted on the Debating Europe platform. Drawing on narrative and discursive approaches, we propose a framework to operationalize the (de)legitimation and identification categories used by e-debaters within their discursive construction of European identity. The qualitative empirical research shows three main (de)legitimation clusters: the “EU as a loss,” “inclusive gain,” and “exclusive gain.” We discuss these findings within the broader context of Europeanization, identity multiplicity, and the conditions of the EU enlargement policy.  相似文献   
29.
This article examines how role theory can enhance the middle-power literature in understanding the role preferences of middle powers. Rather than treating it as merely a function of material capability or good international citizenship, this article resituates middle power as a concept of international status that states aim to pursue through the enactment of role conceptions. Thus, it reinstates a conceptual distinction between ‘middle-power status’ and ‘middle-power roles’. The article suggests that the notion of role conceptions can analytically connect the status-seeking behaviour of middle powers with their foreign policy agenda. In so doing, it provides a more nuanced explanation of middle-power behaviour, which might differ between one middle power and another. Using Indonesia and South Korea as case studies of middle power, this article contends that foreign policymakers have strategically conceptualised and enacted several main roles that aim to capture historical experience, as well as ego and alter expectations, in order to pursue middle-power status. These role conceptions determine the foreign policy agenda of states in articulating their middle-power status.  相似文献   
30.
The seismic vulnerability of city centers is commonly assessed by extending the study methods applied to single buildings to urban aggregations. This approach is not always applicable at territorial scale, as it is uneconomical in terms of time and costs. An innovative method provides reasonable large-scale a priori estimation of parameters not directly evaluable from the exterior of buildings by elaborating values which can be measured from the outside. Those parameters are treated as continuous variables, by assigning them a suitable probability density function. The Bayesian approach is adopted, which allows the update of initial hypotheses by using new data gathered during on-site surveys. In this regard, a rapid survey form for the on-site data collection is proposed. An example of its application to a façade of a building structural unit in Santo Stefano di Sessanio in L’Aquila province (Italy) is proposed, showing promising preliminary results for buildings belonging to Italian historical centers.  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