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   1077篇
  免费   82篇
  2024年   6篇
  2023年   22篇
  2022年   8篇
  2021年   4篇
  2020年   56篇
  2019年   33篇
  2018年   94篇
  2017年   98篇
  2016年   85篇
  2015年   53篇
  2014年   49篇
  2013年   267篇
  2012年   44篇
  2011年   42篇
  2010年   25篇
  2009年   27篇
  2008年   26篇
  2007年   9篇
  2006年   20篇
  2005年   15篇
  2004年   9篇
  2003年   9篇
  2002年   14篇
  2001年   12篇
  2000年   7篇
  1999年   8篇
  1998年   12篇
  1997年   6篇
  1996年   7篇
  1995年   6篇
  1994年   5篇
  1993年   10篇
  1992年   7篇
  1991年   8篇
  1990年   7篇
  1989年   6篇
  1988年   6篇
  1987年   5篇
  1986年   7篇
  1985年   2篇
  1982年   3篇
  1981年   3篇
  1979年   2篇
  1973年   2篇
  1969年   2篇
  1962年   1篇
  1961年   1篇
  1959年   2篇
  1956年   1篇
  1950年   3篇
排序方式: 共有1159条查询结果,搜索用时 31 毫秒
971.
This study describes a thorough inspection of a 20th century church in the town of Isla Cristina (in the province of Huelva, southwestern Spain), which is currently awaiting restoration. The study indicates the damage processes at work in the building structure materials (brick, concrete, steel, and wood), which are closely related to its geographical location, and analyses the deterioration of the wooden roof structure. The analysis of the wooden roof includes the results of an inspection methodology on a protected building based on traditional techniques such as visual inspection and innovative non-destructive inspection techniques (visual classification, ultrasounds and thermography). Fieldwork consisted of the visual classification of the wooden pieces according to Spanish standard UNE 56544:2007 specifications after which ultrasound and thermography techniques were applied on-site. A second stage involved laboratory tests (anatomic identification, density and bending strength) using wood samples extracted from the structure in order to check the values for the physical and mechanical properties previously recorded by non-destructive techniques (NDT). These non-destructive techniques are used in inspections of the wooden roofs of buildings to identify dampness, deterioration, density loss and defects as a means of assessing their conservation status. This work concludes that the use of ultrasound and thermography techniques constitute an accurate diagnostic tool for the on-site inspection of wooden structures and the evaluation of their condition. Thermography identifies different materials and moisture content while ultrasound detects the various degrees of deterioration and density-loss in areas of the wood with high moisture content.  相似文献   
972.
973.
974.
Identifying integrated urban areas is an important issue for urban analysis and policy evaluation. In this article, we provide a set of FUAs suitable for monitoring urbanization in Ecuador, a less developed country without commuting data. We do so substituting such socioeconomic flows by available information on road structure, which allow us to work with accessibility based on a varying travel time. In order to build Ecuadorean FUAs, we calibrate our methodology considering Colombian data. We perform several sensitivity analysis and robustness checks to Ecuador with alternative sources of socioeconomic flows. We conclude that the use of GIS data and the calibrated thresholds provide a set of FUAs similar to the ones that would result of using commuting information.  相似文献   
975.
Exported peanuts have been a key source of state revenue and rural incomes in Senegal since the early 20th century. Senegal has among the world's highest rates of liver cancer incidence. From the 1960s, aflatoxin - the toxic metabolite of fungal strains to which peanut plants are vulnerable - was suspected to be a cause of this cancer. Aflatoxin has since been classified and, in markets that import Senegalese peanuts, regulated as a carcinogen. This article situates aflatoxin toxicity amid the traces of Senegal's century-old peanut export economy. Examining how peanuts have transformed and inhabit soil, landscapes, buildings, food, bodies and aetiological knowledge, it suggests ways in which aflatoxin as well as uncertainty about its carcinogenicity might be cast as residues of a market-oriented economy.  相似文献   
976.
ABSTRACT

This article examines policy responses in Canada and the US to the shale revolution and changing North American oil and gas markets. We outline the effect of the shale revolution on North American oil and gas markets, and how the subsequent energy policy choices in each country changed the relationship between Canada and the US. In the US, increasing production, combined with the policy imperative of maintaining energy security, led to less support for Canadian supply and the subsequent on-off-on saga of the Keystone XL pipeline. In Canada, growing concern about the balance between the environment and the economy led to stalled pipeline development and reform of regulatory systems, problems exacerbated by the new policy direction in the US.  相似文献   
977.
Javier Moreno Zacarés 《对极》2020,52(5):1351-1372
Despite a cascade of corruption scandals over the last decade, the role of political corruption has yet to be accounted for in the scholarship on Spanish urban entrepreneurialism. This is an omission that extends to the broader literature on the topic as well. This paper looks at the theoretical causes of this neglect and explores ways of integrating corruption into the study of urban entrepreneurialism. To do so, it offers a systematic analysis of the role of clientelism in the political economy of Spanish inter-urban competition. Contrary to the existing literature, which at best explains away corruption as a logical outgrowth of intensified competition for real estate capital, this paper argues that corruption is rooted in a political structure that precedes the emergence of urban entrepreneurialism. This structure is identified as an “iron triangle”, a complex of colluding interests formed by the state, the real estate industry, and political parties.  相似文献   
978.
In Colombia’s agrarian spaces, war and extractivism are deeply entangled. Almost four years after the peace accords signed between the national government and the FARC guerrilla, post-conflict geographies are best characterised by the ongoing dispossession of local populations related to the entrenchment of extractivism. Drawing from ethnographic work carried out in the Colombian Caribbean on the ordinary practices and spaces of social reproduction, the ordinary geographies, this article explores gendered practices of care and their role in both sustaining and disrupting paramilitary violence and agrarian extractivism. The focus not just on the gendered effects of war and extractivism, but on gender’s constitutive role in the configuration of these processes and dynamics, allows us to contribute to recent literature on extractivism, dispossession and violence from a feminist standpoint.  相似文献   
979.
980.
This paper presents the results of a pilot study using dental microwear analysis on 23 sheep and goat teeth dated to the 6th century BC from the Iron Age site of El Turó Font de la Canya (Barcelona, Spain). This study aimed to reconstruct livestock management practices and landscape use. The dental microwear pattern indicates that sheep and goats could have been grazing in the same area where vegetation was composed of shrubs, bushes and non-graminaceous plants on an eroded landscape, although additional supplies of fodder cannot be excluded. This scenario is compatible with the archaeological and palaeoenvironmental data which suggest a possibly increased territoriality, land degradation and an increase of woodland clearance during Iron Age in the North-east of the Iberian Peninsula. Furthermore, we applied two recent microwear approaches which provide more information about mortality events and the possibility of distinguishing between an intensive and extensive management. This paper demonstrates how this method can be used to better understand animal husbandry practices and landscape use in Late Prehistory.  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