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   892篇
  免费   39篇
  2023年   12篇
  2021年   3篇
  2020年   9篇
  2019年   21篇
  2018年   31篇
  2017年   51篇
  2016年   44篇
  2015年   31篇
  2014年   25篇
  2013年   267篇
  2012年   28篇
  2011年   25篇
  2010年   22篇
  2009年   24篇
  2008年   21篇
  2007年   30篇
  2006年   14篇
  2005年   12篇
  2004年   16篇
  2003年   14篇
  2002年   25篇
  2001年   17篇
  2000年   9篇
  1999年   17篇
  1998年   15篇
  1997年   11篇
  1996年   10篇
  1995年   8篇
  1994年   7篇
  1993年   4篇
  1992年   7篇
  1991年   4篇
  1990年   3篇
  1989年   4篇
  1988年   3篇
  1987年   7篇
  1986年   4篇
  1985年   7篇
  1983年   4篇
  1982年   6篇
  1981年   3篇
  1980年   5篇
  1979年   9篇
  1978年   3篇
  1977年   7篇
  1976年   3篇
  1975年   5篇
  1974年   5篇
  1973年   6篇
  1972年   5篇
排序方式: 共有931条查询结果,搜索用时 15 毫秒
81.
WHITE, M.A., FALKINGHAM, P.L., COOK, A.G., HOCKNULL, S.A. & ELLIOTT, D.A., 2013. Morphological comparisons of metacarpal I for Australovenator wintonensis and Rapator ornitholestoides: implications for their taxonomic relationships. Alcheringa 37, 1 - 7. ISSN 0311-5518.

Various comparisons of left metacarpal I of the Australovenator wintonensis holotype have been made with Rapator ornitholestoides. These specimens were identified as being morphologically more similar than either was to that of the neovenatorid Megaraptor namunhuaiquii. Owing to the poor preservation of A. wintonensis and R. ornitholestoides, distinct morphological separation between the two appeared minimal. The recent discovery of a near perfectly preserved right metacarpal I of A. wintonensis enables a direct and accurate comparison with R. ornitholestoides. Distinct morphological differences exist between the metacarpals of the two species. A re-evaluation of the age of the A. wintonensis holotype site (AODL 85 ‘Matilda Site’) with zircon dating reveals a maximum age of 95 Ma, 10 Ma younger than the Griman Creek Formation at Lightning Ridge, from which R. ornitholestoides was recovered. This age difference detracts from the probability that the specimens belong to the same genus.

Matt A. White? [fossilised@hotmail.com], School of Engineering, The University of Newcastle, Callaghan, New South Wales 2308, Australia; Peter L. Falkingham? [pfalkingham@rvc.ac.uk], Department of Comparative Biomedical Sciences, Structure and Motion Laboratory, Royal Veterinary College, London, UK; Alex G. Cook [alex.cook@y7mail.com] and Scott A. Hocknull [scott.hocknull@qm.qld.gov.au], Ancient environments, Queensland Museum, Hendra, Queensland, 4011, Australia; David A. Elliott [david.elliott@aaod.com.au], Australian Age of Dinosaurs Museum of Natural History, The Jump Up, Winton, Queensland, 4735, Australia. ?Also affiliated with Australian Age of Dinosaurs Museum of Natural History, The Jump Up, Winton, Queensland 4735, Australia. ?Also affiliated with Department of Ecology and Evolutionary Biology, Division of Biology and Medicine, Brown University, USA. Received 22.9.2012; revised 13.1.2013; accepted 17.1.2013.  相似文献   
82.
83.
84.
85.
86.
This paper analyses the current structure of the system of European cities and regions, relations within the system and how it is changing. Cluster analysis distinguished eight regional types: metropolitan, semi‐peripheral and peripheral service regions; central, semi‐peripheral, peripheral and collapsed industrial regions; and agricultural regions. The core of European industrial societies proves to be almost identical with the city belt that dominated economic development in pre‐industrial Europe. Two possible paths of change are discussed: delocalization of simpler, labour cost‐intensive activities towards the periphery (delocalization hypothesis), or structural changes in industrial core regions and persisting marginal status in the periphery (restructuring hypothesis). Neither hypothesis could be confirmed or rejected unequivocally: there were indicators for the continuing importance of urban service centres but no peripheral industrialization for the continuing dominance of industrial core regions while undergoing structural changes. It is concluded that there are hardly any signs of convergence between core and peripheral regions.  相似文献   
87.
88.
89.
90.
During the archaeobotanical investigation of Scythian–Sarmatian period (Early Iron Age), pits with crop processing waste, discovered in the floodplain of Donets River, eastern Ukraine, and charred remains of cereal grains, dominated by broomcorn millet, were recorded. The grains from the pits were radiocarbon dated to the fifth to first century BC. Those pits are distant from any known contemporaneous settlement. The apparent disconnection of these pits from any local settlement suggests that (1) millet was brought from other locations by mobile groups, or (2) millet was cultivated locally by populations whose settlements have left no discernible archaeological trace. The analysis of molecular biomarkers preserved in palaeosols that are stratigraphically connected to the pits revealed high levels of miliacin, a molecule that can be preserved in ancient soils and sediments, and that is consistent with broomcorn millet (Panicum miliaceum). High levels in miliacin in soils stratigraphically connected to the pits are interpreted as the result of a large biomass of P. miliaceum produced at time of soil formation. Our biogeochemical results applied to a palaeosol thus attest to the in situ cultivation of crops dominated by the broomcorn millet during the early Iron Age in the floodplain of Donets River. Biochemical examination of soils and palaeosols can thus provide useful information on past dynamics of land-use by ancient population, especially when settlements or macrobotanical remains are absent.  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