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   217篇
  免费   25篇
  国内免费   8篇
测绘学   24篇
地球物理   35篇
地质学   126篇
海洋学   7篇
天文学   1篇
综合类   5篇
自然地理   52篇
  2024年   1篇
  2023年   2篇
  2022年   3篇
  2021年   9篇
  2020年   11篇
  2019年   10篇
  2018年   3篇
  2017年   5篇
  2016年   14篇
  2015年   14篇
  2014年   7篇
  2013年   14篇
  2012年   4篇
  2011年   9篇
  2010年   15篇
  2009年   6篇
  2008年   15篇
  2007年   16篇
  2006年   7篇
  2005年   11篇
  2004年   10篇
  2003年   12篇
  2002年   7篇
  2001年   8篇
  2000年   6篇
  1999年   6篇
  1998年   2篇
  1997年   6篇
  1996年   3篇
  1995年   1篇
  1994年   1篇
  1993年   2篇
  1991年   2篇
  1989年   1篇
  1987年   1篇
  1986年   1篇
  1985年   2篇
  1984年   1篇
  1983年   1篇
  1980年   1篇
排序方式: 共有250条查询结果,搜索用时 15 毫秒
1.
Kiacatoo Man, a large, rugged Aboriginal adult buried in the Lachlan riverine plains of southeastern Australia, was discovered in 2011. Laser‐ablation uranium series analysis on bone yielded a minimum age for the burial of 27.4 ± 0.4 ka (2σ). Single‐grain, optically stimulated luminescence ages on quartz sediment in which the grave had been dug gave a weighted mean age of 26.4 ± 1.5 ka (1σ). Luminescence samples from the grave infill and from sediment beneath the grave exhibit overdispersed dose distributions consistent with bioturbation or other disturbance, which has obscured the burial signal. The overlap between the minimum (U‐series) and maximum (luminescence) ages places the burial between 27.0 and 29.4 ka (2σ). Luminescence ages obtained from the channel belt of between 28 ± 2 and 25 ± 3 ka indicate that fluvial sedimentation was occurring before the Last Glacial Maximum, which is consistent with the broader geomorphic setting. Together, these results are internally and regionally consistent, and indicate that Kiacatoo Man was one of the more ancient individuals so far identified in Australia. His remains are important to our understanding of patterns of biological variation and other processes that have shaped people in the Murray‐Darling Basin through time. Copyright © 2019 John Wiley & Sons, Ltd.  相似文献   
2.
3.
A complex of channels underlying the Baginton-Lillington Gravel (Baginton Formation) at Waverley Wood Quarry, Warwickshire is described. Fossil pollen and plant macrofossils, Coleoptera, Ostracoda, Mollusca and Mammalia are described from the channel-fill deposits. Consideration of all the evidence allows the identification of four separate stages of channel fill which largely occurred under a cool temperate climate. At the top of Channel 2 evidence for a cold, continental climatic episode can be recognised, suggesting that the whole complex was deposited under a fluctuating climate at the end of a temperate stage. At two levels in the channels human artefacts were recovered confirming the presence of Palaeolithic people in Warwickshire during the deposition of the sediments. Amino-acid geochronology suggests an age within the ‘Cromerian Complex’ Stage for the channels. The small vertebrate and molluscan faunas indicate that the deposits are no older than the latter part of the ‘Cromerian Complex’ Stage of East Anglia. The regional stratigraphic significance of the Waverley Wood succession is outlined.  相似文献   
4.
Effective marine archaeological site management demands detailed information on not only the spatial distribution of artefacts but also the degradation state of the materials present. Although sonar methods have frequently been used in an attempt to detect buried wooden shipwrecks they are currently unable to indicate their degradation state. To assess the sensitivity of acoustic measurements to changes in the degradation state of such material, and hence the potential for sonars to quantify degradation, laboratory measurements of compressional wave velocity, as well as bulk density for oak and pine samples, in varying states of decay, were undertaken. These data enabled the calculation of theoretical reflection coefficients for such materials buried in various marine sediments. As wood degrades, the reflection coefficients become more negative, resulting in the hypothesis that the more degraded wood becomes, the easier it should be to detect. Typical reflection coefficients of the order of −0.43 and −0.52 for the most degraded oak and pine samples in sand are predicted. Conversely, for wood exposed to seawater the predicted reflection coefficients are large and positive for undegraded material (0.35 for oak, 0.18 for pine) and decrease to zero or slightly below for the most degraded samples. This indicates that exposed timbers, when heavily degraded, can be acoustically transparent and so undetectable by acoustic methods. Corroboration of these experimental results was provided through comparison with high resolution seismic reflection data that has been acquired over two shipwrecks.  相似文献   
5.
利用C4.5决策树分类算法和GIS组件Super Map Objects,开发实现了基于连续文化序列的空间数据挖掘系统,运用此系统对郑州-洛阳地区史前四个连续文化时期的聚落进行了数据挖掘,提取了聚落遗址面积的分类规则,并根据这些分类规则和聚落的空间分布情况对四个文化时期的I级聚落进行对比分析,得出了I级聚落的空间分布特点,即I级聚落中的一些特大面积的聚落朝着中心聚落的方向发展。  相似文献   
6.
近20年来中国旧石器考古学的进展与思考   总被引:13,自引:4,他引:13  
本文记述近20年来中国旧石器考古学研究的主要成果,着重论述早期人类扩散的速度和中国旧石器工业的基本框架:北、南方各存在一个主工业,并存若干区域工业;同时对试验考古研究以及东西文化比较研究等的现状和问题提出孔见。  相似文献   
7.
朱诚  张强  张芸  张之恒  沈明洁 《地理科学》2003,23(6):705-712
通过长江三角洲长江以北地区高邮龙虬庄和海安青墩两个新石器时代考古遗址剖面粒度、磁化率、孢粉以及年代学测定,较为全面地分析了该区全新世以来生态环境变化与人类文明兴衰的相互关系,研究结果表明:在有人类活动以前,该区距离海洋较远,但受海面变化影响强烈。此后,气候向暖湿方向发展,7000—6000间的大西洋温暖湿润气候以及3700aB.P.左右期间,该区气候适宜,人类文明在这样的适宜气侯条件下得到长足发展。值得注意的是,海安青墩遗址剖面中出现厚达1m多的自然沉积地层,粒度分析以及孢粉分析表明,这一自然沉积地层是4000aB.P.以来的海侵事件所致,正是这次海侵事件,使研究区人类文明得以衰落。  相似文献   
8.
9.
10.
The Amiens-Renancourt 1 site recently yielded one of the most important Upper Palaeolithic human occupations of northern France by the number of flint artefacts and especially by the presence of Venus figurines. All the material comes from a single archaeological layer located in a tundra gley bracketed by loess units. A multi-proxy study combining a detailed stratigraphy, luminescence and radiocarbon datings and high-resolution (5 cm per sample) grain size and molluscan analyses was therefore carried out to reconstruct and date the associated environmental changes and to determine the exact context of the human occupation. The chronological frame thus established supports the correlations of the archaeology-bearing tundra gley and of an underlying arctic brown soil with Greenland interstadials GI-4 and GI-3. Composition changes in the molluscan population enabled the identification of transitional and optimum phases and sub-phases within these two pedogenetic horizons. A conceptual correlation model linking molluscan phases with millennial-scale variations of Greenland ice-core and Sieben Hengste speleothem climate records is proposed. The Human occupation appears contemporaneous to the end of the stadial–interstadial transition of GI-3. Synchronous in Amiens-Renancourt 1 and Nussloch, subsequent micro-gleys may also result from a regional/global forcing. Such a level of detail is unprecedented in a loess sequence.  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