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   272篇
  免费   13篇
  2023年   6篇
  2022年   3篇
  2021年   3篇
  2020年   4篇
  2019年   12篇
  2018年   12篇
  2017年   20篇
  2016年   13篇
  2015年   16篇
  2014年   14篇
  2013年   40篇
  2012年   12篇
  2011年   11篇
  2010年   16篇
  2009年   11篇
  2008年   8篇
  2007年   9篇
  2006年   10篇
  2005年   7篇
  2004年   4篇
  2003年   7篇
  2002年   2篇
  2001年   3篇
  2000年   3篇
  1999年   3篇
  1998年   3篇
  1997年   2篇
  1996年   2篇
  1995年   1篇
  1994年   6篇
  1993年   1篇
  1992年   2篇
  1991年   1篇
  1990年   2篇
  1988年   1篇
  1985年   2篇
  1984年   2篇
  1983年   1篇
  1981年   2篇
  1980年   1篇
  1978年   1篇
  1976年   1篇
  1975年   1篇
  1973年   2篇
  1972年   1篇
  1969年   1篇
排序方式: 共有285条查询结果,搜索用时 31 毫秒
151.
152.
153.
Here we demonstrate the successful extraction and amplification of target species DNA from artefacts made of whale baleen collected from excavations of past palaeo-Eskimo and Inuit cultures in Greenland. DNA was successfully extracted and amplified from a single baleen bristle of 1.5 cm length dated based on archaeological context to the period of the Saqqaq culture, more than 4000 years ago and following decades of storage at room temperature at the National Museum. The results reveal ancient baleen in archaeological material as a potential source of DNA that can be used for population genetic studies. We conclude that genetic investigation of historical baleen collections can contribute to our knowledge of the prehistoric population genetics of baleen whales, for example by quantifying the impact of modern whaling on the genetic diversity of bowhead whales.  相似文献   
154.
The paper contributes to notions of ‘hybrid’ historical geographies of irrigation by focusing on contested visions for irrigation in the Lower Rio Grande Valley of Texas. Adding to geographical work using biography, notions of performance, and racialized landscapes, the paper analyzes debates between John Shary and Charles Pease. Shary and Pease were protagonists, respectively, of pumping water from the Rio Grande and a gravity scheme reliant on action by the U.S. Bureau of Reclamation. The pumping system survived; the gravity system was never constructed. However, the debate between Shary and Pease illustrates tensions within the Anglo elite. The analysis focuses on three early-twentieth-century moments. The first is a 1918 crisis in Shary’s irrigation company, followed by a 1927 debate between Shary and Pease over the flaws of the pumping system and benefits of gravity irrigation. Finally, the paper focuses on Shary and Pease’s constructions of racialized landscapes that subordinated Hispanics as voters to be utilized for Shary’s accumulation strategy, or as ‘non-water users’ that should be excluded from water politics. The paper argues that Shary and Pease projected similarly exclusionary social visions onto the irrigated landscape in spite of their differences on irrigation systems.  相似文献   
155.
156.
This article examines the way in which the tribal areas of the North-West Frontier came to constitute a recurrent point of contention and dispute in Anglo-Afghan relations during the period under examination. It argues that while much attention has been paid to the way in which the activities of autonomous tribes of the frontier impacted upon British interests, much of the existing historiography has tended to focus upon the physical confrontation between tribe and state and has hitherto ignored perhaps the most complex aspect of the ‘tribal problem’ during this period; its impact upon the Government of India's diplomatic relations with Afghanistan. The article proposes that the period 1929–39 constituted a particularly challenging context for British policy-makers wrestling with the requirement to formulate a cost-effective tribal policy that would suit the interests of British India without undermining the newly emerged, pro-British but inherently weak Musahiban regime. It argues that while the Government of India avoided any fatal breach in relations with the Afghan leadership, the process of frontier policy-making illustrated some fundamental weaknesses in perspective on the part of that government department most closely associated with the formulation of such policy: the Indian Political Service.  相似文献   
157.
Abstract

The article presents an overview of the main public debates in Norway that can be said to have framed and defined the High North since the turn of the Millennium. It is based on a qualitative study of over 3000 articles published in four Norwegian newspapers issued between 2000 and 2006. Our discussion is structured around three overarching, interconnected narratives that we think capture the essence of the Norwegian public discourses on the High North between 2000 and 2006. These are “Fragments from the 1990s”; “The great narrative of the High North”; and “Mixing cold water with hot blood”. The first half of the 2000s is characterised by an almost total absence of the High North as a discursive and politically coherent concept. From 2004, however, usage grew fivefold, alongside an extensive, dynamic discursive mobilisation. When the Russians decided in 2006 to shelve the Shtokman project and critical voices were heard condemning Norway's environmental performance in northwest Russia, public opinion swung back again. A feeling of cold reality replaced the sense of optimism towards the energy potential of the north, and an exercise in collective soul-searching commenced – similar to that of the early years of the decade. We believe the type of discursive change we document in this article constitutes policy trends in connection both with the High North and with other sectors where policy is subject to intense public debate and appraisal. We hope that discourse analysis has enabled us to investigate and share how Norwegian public discourses on the High North are socially produced, framed and maintained but at the same time are always in flux and open to “new” directions which should be possible – at least in theory – to trace by going back in time.  相似文献   
158.
In this special issue, we seek to explore experiences, performances and effects of both “unfamiliarity” and “familiarity” across a diversity of inner and outer borders of the European Union. In EU integration discourse, cross-border unfamiliarity is usually considered to obstruct international mobility and diminish opportunities for cross-border cohesion and communities to develop. European development policy, therefore, often focuses on creating mutual understanding in border regions, especially through diminishing the barrier effect of borders. One of the consequences is that more cross-border familiarity is created. However, too much familiarity may also have undermining implications for cross-border mobility, integration and community-building. This special issue, therefore, scrutinizes what “being” and “feeling” (un)familiar imply in cross-border contexts and what consequences both have for spatial practices in and representations of borderlanders in several Euroregions—as well as for European regional development policies aiming for cross-border mobility, integration and community-building.  相似文献   
159.
160.
Soluble salts are indigenous to the marine sediments of the Esna Formation and Thebes Formation in central Egypt. Natural weathering processes and human impact cause salt efflorescence in tombs and on walls of ancient Egyptian monuments in the Theban Necropolis, resulting in the disintegration of wall paintings and carved hieroglyphs. Determination and quantification of soluble salts and measurements of the porosity were done on tomb marls in order to understand the origin and damage potential of the salts in the royal tombs of the Valley of the Kings. The study shows that sodium chloride (NaCl) is the predominant salt species. Sulphates, anhydrite (CaSO4) and gypsum (CaSO4 . 2 H2O) also occur in the limestone deposits of the Thebes Formation and the underlying shale deposits of the Esna Formation. Member I of the Thebes Formation, into which most of the ancient tombs were hewn, shows the highest amount of soluble salts (up to 6·2 wt-% dry). In addition, the porosity and permeability of the marls in Member I are high, enhancing water molecules and brine migration. Wetting and drying of the tomb surfaces in the past has affected solution, transportation and recrystallization of water soluble minerals, and has led to major destruction of wall paintings and ornamentations. This study shows that large amounts of salt minerals still remain in the wall rocks. Future humidity changes due to flash floods and tourists may favour salt crystallization in the ancient Egyptian monuments. The authors urge the authorities to undertake steps to prevent further destruction to save the magnificent cultural heritage found in the Thebes area.  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