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   96篇
  免费   2篇
  2024年   1篇
  2023年   1篇
  2022年   1篇
  2020年   5篇
  2019年   2篇
  2018年   5篇
  2017年   3篇
  2015年   1篇
  2014年   3篇
  2013年   32篇
  2012年   3篇
  2011年   3篇
  2010年   6篇
  2009年   3篇
  2008年   7篇
  2007年   7篇
  2006年   4篇
  2005年   2篇
  2004年   3篇
  1998年   1篇
  1993年   1篇
  1979年   4篇
排序方式: 共有98条查询结果,搜索用时 15 毫秒
51.
Excavations at the archaeological site of Encosta de Sant'Ana (Lisbon, Portugal) uncovered a mid-Holocene buried alluvial soil associated with early Neolithic occupation layers. Routine laboratory analyses and micromorphological observations were undertaken on the soil material. Humic acids from its Ab horizon, as well as Neolithic ecofacts, were radiocarbon dated. The dates obtained indicate that soil was formed between c. 8.0 and 6.0 cal ka BP and that the pedological evidence fits the record of the North Atlantic Holocene IRD events (“Bond events”) and the so-called “Holocene climate optimum”. The geoarchaeological record reveals that Neolithic inhabitants settled upon a stable surface, still affected by soil formation that was suddenly interrupted by slope wasting, probably in correspondence to Bond event 4, at c. 6.0 cal ka BP.  相似文献   
52.
This paper is aimed at determining the effects of the soil characterization on the seismic input to use for seismic assessment. Three different soil profiles have been assembled to represent the stratigraphies found through a proper experimental investigation, carefully described, and alternative seismic site response analyses have been performed. The surface spectra obtained from the seismic site response analysis (SRA) are very different from each other, thus evidencing the importance of carefully describing soil stratigraphy. Furthermore, the comparison among the surface records found for different return periods has shown a limited sensitivity of the SRA to the seismic intensity.  相似文献   
53.
刘家洼遗址出土大量珍贵的青铜器对研究春秋早期芮国历史具有重要价值,但由于青铜器受到长期腐蚀影响,其蕴含的部分信息可能发生损失。为研究刘家洼青铜器的工艺、保存状况与稳定性,揭示关中东部黄土塬区出土青铜器的土壤腐蚀特征,并为文物保护修复提供参考依据,本工作对刘家洼青铜器腐蚀成因进行综合研究。本工作利用金相显微镜观察、扫描电镜-能谱、X射线衍射、拉曼光谱等分析手段对刘家洼遗址出土6件青铜器样品的锈蚀物相与锈层结构进行表征。结果表明,青铜器腐蚀产物以赤铜矿、孔雀石以及白铅矿为主。部分青铜器表面存在浅绿色粉状腐蚀产物,但并非含氯腐蚀产物。刘家洼青铜器锈层结构自金属基体向外依次为过渡层、原始表面内非金属层、原始界面、原始表面外原位沉积层及扩散沉积层。原始界面内非金属层Cu/Sn值低于基体,表明基体内的铜元素腐蚀后向外迁移以及锡元素腐蚀后形成锡石原位沉积。原始界面外Cu/Sn比值显著高于原始界面内非金属层,表明外迁的铜离子在埋藏环境作用下沉积。本工作通过对青铜器附着土壤样品pH值、氧化还原电位以及离子色谱分析,结果表明刘家洼青铜器埋藏环境为弱碱性氧化型环境,土壤中氯离子含量不高,这与出土青铜器的腐蚀...  相似文献   
54.
Examining four colonial soil conservation schemes in East Africa that were part of the modernising project of colonialism, this article considers multiple historical geographies of the colonised world. There were multiple modernities: while information and ideas flowed in many directions between (and within) the metropole and colonies, the particular ‘modernity’ that was put into practice was shaped by its context. The article highlights therefore that – despite playing to the same tune of modernity – colonialism was highly differentiated in the way that its policies played out on the ground. Furthermore, the ‘colonised’ acted and reacted to the policies in highly differentiated ways that depended on their particular context in time and space. All but one of the soil conservation schemes examined were rejected and there was significant resistance to them. Much of the existing literature on such schemes examines them in the context of essentially political processes, and in particular their influence on rising nationalism. Whilst these processes are important, this paper shows that there were other, non-political, factors that influenced the reception they were given, which need to be considered too. These ‘everyday’ details were about the practical and technical nature of the schemes, and by exploring these aspects of the schemes, and comparing them, the article highlights why most were rejected. It suggests that different aspects of conservation schemes need to be explored for a firm understanding of the reasons behind resistance to such schemes.  相似文献   
55.
Recent developments in digital technologies are heralding significant changes in the way we acquire, visualise and analyse archaeological data. Terrestrial laser scanners can be used to create photo-realistic virtual copies of landscapes, and archaeological features, and offer the potential to improve our understanding of three-dimensional (3D) spatial relationships at study sites. Here we present a methodology for the integration of a high-resolution 3D site model with soil chemical data obtained from an abandoned settlement site located in the Central Highlands of Scotland. At this site, the multi-element concentration in soil, co-visualised within a topographic setting, has an important role to play in elucidating settlement layout and activity. The methods described here are also of significance in archiving sites of archaeological/historical importance where development activities and/or environmental processes may destroy remains, or where access to field sites is restricted.  相似文献   
56.
Lead concentrations were measured in 41 rib samples from the Romano-British cemetery at Poundbury and in two sets of soil samples from the graves yielding up the bones. The levels of lead in the soil were in no way exceptional (means for the two series were 16·7 and 24·8 μg/g dry weight) and there was no correlation between soil lead and bone lead concentrations.Since bone lead concentrations vary independently of those in the soil, it is unlikely that the bones are contaminated by lead in the soil, at least under the conditions prevailing at this particular site.  相似文献   
57.
Relict arable soils dating fromc.AD700 provide an opportunity to identify early arable land management practices in the agriculturally marginal landscapes of the Lofoten archipelago, northern Norway. Synthesis of field survey and soil thin section micromorphology supported by image analysis suggests that there was deliberate management of erodible sandy soils in sloping locations to create small areas of cultivation terrace, with a range of materials used as soil amendments to stabilize the accumulated soil and enhance fertility. Small areas of sandy soils in more gently sloping locations were also cultivated, again with a range of materials used as amendments and which contributed to a significant increase in soil thickness. The last phase of cultivation commenced during the late 1800s and involved the reclamation of wetter, peaty soils by spade. These patterns of arable land management are repeated in different parts of Lofoten and indicate that despite the climatic and economic marginality of arable activity in Lofoten, land management practices were developed and applied to permit barley production from small areas.  相似文献   
58.
Microzonation is widely used in seismic risk evaluations to define the predominant period values, which are usually associated with extended areas of a few hundred meters. However, the representative values corresponding to these areas are obtained from few measurements in each area. Thereby, results are accurate only in the case of depth-dependent soils. However, not detected narrow and sharp lateral changes in soil are potentially the cause of imprecision and could be a source of specific errors. This article aims to present several tests conducted in order to emphasise the importance of accurate selection of points, to underscore the necessity of more precise and detailed evaluations, and to suggest a possible methodology to select the most appropriate data acquisition points. Results highlight the need to divide microzonation areas into smaller zones for a precise evaluation in locations where sudden changes in soil characteristics exist. Therefore, in such sites the requirement of nanozonation appears; defining zones with the same soil response. Distance between vibration measurements could be the main problem for nanozonation; data acquisition in areas with irregular geology can be time consuming when a precise analysis is required. In the most complicated environments or in dense cities, it could even be unfeasible. Consequently, it is necessary to establish a functional methodology to adequately distribute the measurement points throughout the area. On this occasion, three sites in Barcelona city were studied. This city is surrounded by mountains at NW, W, and S, and by the Mediterranean Sea at N and E. As a consequence, the shallow geology is characterized by many paleochannels and streams that are currently buried. These geological structures most likely affect the soil response. Several tests were carried out to determine this dependence. The tests were based on Ground Penetrating Radar (GPR) surveys to define the paleochannels position and on vibration measurements in order to define properly the soil response. The results from both methods were compared to the known geology to accurately define the effect of the shallow geological structures in the predominant period and in the GPR images. Areas with the same geological unit but different materials were identified in the GPR images, allowing the selection of the most appropriate distance between vibration measurements in each place. As a final result, predominant periods that were measured over the same geological unit but over different material showed changes higher than the 40% in short distances. This procedure could improve the soil response maps, including nanozonation.  相似文献   
59.
The history of two monumental grave buildings (nos. 4 and 5), excavated in area P of the late pre‐Islamic city of Mleiha, has been studied in detail. Like all other tombs excavated up to the present day in Mleiha, their chambers had been emptied in ancient times. They were found devoid of human remains and grave‐goods. In the upper parts of the grave fills, however, skeletal remains were encountered. One of the skeletons was radiocarbon dated to AD 623–656, the time of the Islamisation of south‐east Arabia. A radiocarbon date of 384–233 BC for a wooden beam from the same tomb showed that it was built during the late pre‐Islamic period (PIR‐A). These dates and stratigraphic observations made clear that the interments were intrusive. The surrounding sediments were deposited by flooding. Directly underneath the skull of the dated skeleton, a layer of sandy loam was encountered, showing mud cracks. To understand the relationship between the burial and these deposits, micromorphological analyses of the surrounding sediments were conducted. The microstructural organisation of the sedimentary components implied that the skull was interred as part of a burial, and not deposited by natural processes.  相似文献   
60.
室外土遗址经常因遭遇降雨、水淹等发生结皮,造成土遗址表层性能改变,影响土遗址的进一步保护。以定量纯净黄土在等降雨大小下,通过控制不同降雨时长,试验了不同降雨时长下土壤结皮发育的过程,分别测试了降雨前后的结皮厚度、密度、硬度及孔隙结构。结果表明,在降雨量未达到饱和状态时,随降雨量增大,结皮层的厚度、密度、硬度迅速增大,表皮土壤颗粒被击碎,孔隙迅速减小;在降雨量达到饱和状态时,随降雨量增大,结皮层的厚度、密度、硬度缓慢增大,但表皮土壤裂缝迅速发育,由周围向中心形成同心圆状或辐射状裂隙。研究结论可为室外土遗址的保护提供参考。  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