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   603篇
  免费   9篇
  612篇
  2023年   11篇
  2022年   3篇
  2021年   2篇
  2020年   15篇
  2019年   19篇
  2018年   38篇
  2017年   33篇
  2016年   32篇
  2015年   25篇
  2014年   25篇
  2013年   113篇
  2012年   15篇
  2011年   15篇
  2010年   28篇
  2009年   21篇
  2008年   22篇
  2007年   22篇
  2006年   18篇
  2005年   7篇
  2004年   11篇
  2003年   12篇
  2002年   15篇
  2001年   17篇
  2000年   10篇
  1999年   15篇
  1998年   11篇
  1997年   5篇
  1996年   7篇
  1995年   4篇
  1994年   3篇
  1993年   7篇
  1990年   4篇
  1988年   3篇
  1985年   3篇
  1984年   1篇
  1983年   1篇
  1981年   1篇
  1978年   1篇
  1977年   1篇
  1976年   1篇
  1975年   1篇
  1974年   1篇
  1972年   2篇
  1967年   2篇
  1966年   1篇
  1965年   1篇
  1964年   1篇
  1958年   1篇
  1956年   1篇
  1955年   1篇
排序方式: 共有612条查询结果,搜索用时 15 毫秒
41.
    
There has been noticeable development in the protection of linear infrastructure by UNESCO, whether on its cultural, technological or historical merits. However, with the exception of other means of transport incorporated within the field of industrial archaeology or recognised by the CIIC under the category of cultural routes, little or no consideration has been given to roads built from the mid-eighteenth century to the early part of the twentieth century. In view of this situation, this paper has the following aims. Firstly, to define the concept of ‘modern road’ and provide a brief analysis of the historical development and current situation of the same. Secondly, to assess the main contributions made to date regarding the heritage dimension of modern roads. Thirdly, to reconstruct the process of defining linear cultural landscapes, historic transportation corridors, cultural routes and heritage canals, railways and roads, in accordance with the considerations raised by ICOMOS and UNESCO. Finally, to contribute to the debate on the definition, characterisation and assessment of modern roads as world heritage assets, both intrinsically and in relation to established heritage categories.  相似文献   
42.
    
We analyse the isotopic values (δ13C, δ15N) of the diet of pre-Columbian horticulturalist populations from tropical and subtropical areas of southeastern South America, belonging to the Guarani and Taquara archaeological units. The data indicate different trends in each one (T?=?4.21; P?=?0.0004), showing a mixed diet with maize consumption in the Guarani samples (δ13Cco?=??15.5?±?1.8‰; δ13Cap ?10.4?±?0.8‰) and a depleted one in the Taquara ones (δ13Cco ?18.2?±?1.7‰; δ13Cap ?11.9?±?0.9‰), with a significant internal dispersion in both populations. The first population has higher nitrogen values (δ15N 11.1?±?0.6‰) compared to the Taquara samples (δ15N 9.3?±?1‰), suggesting a more carnivorous diet. The recognition of these pre-Columbian mixed diets involves the identification of maize cultivation on the Atlantic side of the southernmost area of South America (Parana Delta, 34° SL). Through the analysis of δ18O we have identified two isotopic ecozones, the first along the Paraná River Valley, with an average value of δ18O ?3.7?±?0.5‰ (CV?=?13.5%; CI?=??3.83 / ?3.16), and the second one, located in the Planalto of southern Brazil (Araucaria Forest), with a mean value of δ18O ?1.5?±?0.3‰ (CV?=?16.5%; CI?=??1.69 / ?1.29). The isotopic data (δ13C, δ15N and δ18O) suggest human movements between these two ecozones.  相似文献   
43.
    
ABSTRACT

This article is concerned with the everyday ‘spatial tactics’ deployed by children in a street situation in order to deal with notions of public space that define them as ‘out of place’, marginal and deviant. Using photovoice, we reconstruct former street children’s definitions of and feelings about their spaces in the city, bringing into view a complex set of social problems, attitudes and strategies that moves beyond the traditional binary notion of street children as either deviants or victims. This work points to the importance of finding ways to ensure the voices of marginalized and disadvantaged children are heard and presents the narratives that are important to our understanding of their worlds. Analyzing their spatiality in contexts of conflict, belonging and resistance, we found that children and youth in a street situation are mainly concerned with empowering themselves and resisting dominant labels and police repression.  相似文献   
44.
    
ABSTRACT

The preservation of the architectural heritage is characterized by the intervention of different technicians, who may disagree on decision-making criteria. In recent years, the H-BIM methodology has emerged to manage these buildings, although the multidisciplinary technical personnel make the decision-taking something of a challenge. In this regard, artificial intelligence may be an opportunity to establish automatic responses, thus optimizing the process. This article proposes a methodology to implement models of classification using the J48 algorithm in a H-BIM model. The case study was focused on a tiles panel from a building which belongs to the Real Alcazar of Seville. First, a model of classification was developed to estimate the degree of intervention with an adequate degree of adjustment. Then, the model was implemented in the H-BIM software by programming using GDL. This methodology automates the decision-making and reduces times of assessments, visualizing and managing the information in the H-BIM model.  相似文献   
45.
    
Whilst the advantages of the application of Land Readjustment (LR) are well known, there are nevertheless numerous countries in which application of LR is difficult or has not been successful. In its analysis of land readjustment constraints, conditions and the international practice, this paper contributes to improving the implementation of an LR system, particularly with respect to the management process. At the international level, management models in seven countries were studied: Australia, France, Germany, Japan, South Korea, Spain and Sweden. In Portugal, three case studies in the municipalities of Almada, Coimbra and Lisbon were selected, with semi-structured interviews being conducted with the respective managing entities. The management models are distinguished by the type of initiative and leadership processes, relations among stakeholders, managing entities and operating rules. It can be concluded that the role of the public authority as the process facilitator from the very initial stages, the existence of a managing entity and a board of specialists, and the legal conditions governing expropriation are key factors for the improvement of land readjustment management.  相似文献   
46.
    
Border regions are not often associated with innovation and economic prosperity. And even when they are prosperous, cross-border interaction is still mostly limited. The opening up of borders in Europe has presented new opportunities for firms located in these border regions to co-operate for innovation and knowledge to flow across borders. Despite the reduction of the importance of borders, firms seeking to access cross-border knowledge resources need still to ‘cross’ the border and address the various effects it brings. This paper therefore asks the question of how the presence of a border affects the processes by which firms attempt to build up productive co-operations for innovation. We use a heuristic of collaborative innovation across borders as building up through four sequential cooperation stages, and each of these different stages is susceptible to different kinds of border effects. Using a case study of firms co-operating across the Dutch-Flemish border, we empirically explore these border crossing processes in order to shed further light on how border processes play out.  相似文献   
47.
The results obtained from the multi-analytic compositional characterization of ceramic pastes and paints of the Santa María style, from the El Bolsón valley (Belén Department, Catamarca Province, Argentina), are presented here. This pottery style had a wide regional distribution in Northwestern Argentina between ca. 1000 and1600 ce and is characterized by its complex iconography painted in black, cream and red. The analyses show that the containers correspond to the technical tradition of using grog temper and suggest that its manufacture involved a double firing process. This reveals a new practice for the time.  相似文献   
48.
    
Examination of the histological structure of bone not only helps investigators to estimate age at death but can also aid in the diagnosis of palaeopathological lesions. The purpose of this paper is to assess whether histological features as described in the literature can confirm the macroscopic diagnoses of ossified subperiosteal haematomas associated with healed scurvy and syphilitic bone changes observed on the anterior tibiae of individuals from a 19th century mining community from Kimberley South Africa. The frequent occurrence of these two diseases amongst the deceased was well established in related hospital documents and governmental documents. A section of bone was removed from lesions on the tibiae of 14 individuals. These bone changes were macroscopically diagnosed as being indicative of either treponematosis ossified subperiosteal haematomas or non‐specific periostitis. Cross‐sections were prepared for microscopic investigation using a manual ground section technique. Ossified haematomas were histologically identified in seven individuals. These sections were characterised by normal cortical bone an intact original periosteal surface and newly formed radiating trabecular bone apposing it. Three phases of ossified subperiosteal haematoma formation and remodelling could be distinguished. Infectious bone changes most likely associated with treponematosis were observed in one individual. These were characterised by lysis and numerous resorption holes/channels. No clear distinction could be made between the internal spongy cortical or newly formed bone. Histological features described by some authors as characteristic of this condition could not be identified. In addition three individuals presented with microscopic features indicative of both the aforementioned bone affections and three did not show any pathological changes on microscopic level. It was concluded that although specific pathological conditions can most likely not be diagnosed purely on the basis of histomorphological observations broad distinctions could be made between lesions caused by the ossification of subperiosteal haematomas and bone changes due to infectious diseases. Copyright © 2009 John Wiley & Sons Ltd.  相似文献   
49.
    
In March 1993, South African State President F. W. de Klerk stunned the world with an announcement that the South African Apartheid Government had developed six and a half nuclear bombs during a top‐secret 15‐year programme. A number of factors led to the decision to develop nuclear weapons; the most important being Pretoria’s fear from the mid‐1970s that a communist takeover in Southern Africa was imminent and that they needed a suitable deterrent to ensure the security of South Africa and their own position of power. It was specifically the involvement of Cuba and the Soviet Union in the Angolan Civil War that led Pretoria to a formal decision in 1978 to develop a limited nuclear capability. At the end of the 1980s, however, the collapse of the Soviet Union, the withdrawal of Cuban troops from Angola, the independence of Namibia, and the imminent democratisation of South Africa brought a rapid end to the perceived ideological and security threat to South Africa and indeed made the deterrence factor of the nuclear arsenal obsolete. In August 1989, Pretoria decided to destroy the arsenal, thereby becoming the first country to voluntarily destroy a nuclear arsenal before acceding to the NPT, which happened in July 1991. This article provides a chronological overview of Apartheid South Africa’s development of a nuclear arsenal, within the framework of the Cold War.  相似文献   
50.
    
  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