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   86篇
  免费   3篇
  2023年   3篇
  2020年   7篇
  2019年   4篇
  2018年   6篇
  2017年   1篇
  2015年   6篇
  2014年   1篇
  2013年   22篇
  2012年   3篇
  2011年   1篇
  2010年   5篇
  2009年   6篇
  2008年   4篇
  2007年   1篇
  2006年   1篇
  2005年   1篇
  2004年   1篇
  2003年   1篇
  2002年   2篇
  2001年   1篇
  2000年   2篇
  1998年   1篇
  1997年   1篇
  1996年   3篇
  1995年   1篇
  1994年   2篇
  1993年   1篇
  1982年   1篇
排序方式: 共有89条查询结果,搜索用时 15 毫秒
51.
Energy-dispersive X-ray fluorescence spectroscopy was used to characterize red-slipped pottery (2nd–1st century BC) from ancient Cassope, north-western Greece. The compositional data were statistically treated by principal component analysis and chemical groups were established, representing locally produced and imported items. Mineralogical investigation by X-ray diffraction indicated firing temperatures in the range from 850 to 1000 °C for most of the sherds, while one group consisted of over-fired items, possibly in excess of 1050 °C. The morphology and elemental composition of the ceramic bodies and surface slips were examined through scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The analyses revealed that different pottery groups exhibit surface slips of different nature, in terms of thickness, degree of vitrification and elemental composition. Overall, the diversity in technological characteristics of the examined sherds is indicative of the socio-economic conditions prevailing in Cassopaea during the late Hellenistic period.  相似文献   
52.
根据历史文献和考古调查,确定出甘肃省庆阳市西峰区彭原乡的两座古城遗址分别是后汉富平县城(GC1)和唐宋彭原县城(GC2),唐宋彭原县是北魏永和元年(434年)以后从今庙头嘴村搬迁到南庄村。据此推断泾河四级支流、马莲河三级支流彭原沟(当地称湫沟)流域的现代侵蚀沟,是在此年以后开始发育的。利用黄土高原现代侵蚀沟地貌年龄计算公式,计算出彭原沟主干沟道现代侵蚀沟的地貌年龄为1669±819年,沟口附近的现代侵蚀沟发育于西晋成帝咸康五年(339年)前后,其主要分支沟谷现代侵蚀沟的地貌年龄介于900±442~1300±638年之间。沟头平均延伸速度为3.367m/a,沟谷平均下切速度为0.063m/a,平均加宽速度0.19m/a。公式计算结果与考古结果基本相符,研究结果具有较高的信度。依此结果,将彭原沟及其支流地貌复原至西晋时期。  相似文献   
53.
Soils in a lower Hunter valley vineyard, New South Wales, Australia, were sampled and analysed for caesium‐137, an indicator of soil erosion status, in 1984–1985 and 2004. From the time of the vineyard's first establishment in 1971 to 1985, estimated soil losses were 250 tonnes (equivalent to 64.2 t ha?1 yr?1). Re‐sampling in 2004 showed that soil losses were 48 tonnes in the 19 years since 1985, equivalent to 9.7 t ha?1 yr?1. The decline in erosion rates may be explained by a change in land and soil management from intensive cultivation to one of no cultivation (sod culture) in 1998, and a lower annual rainfall and fewer rain‐days per year in the period from 1986 to 2004.  相似文献   
54.
East Asian ostrich (Struthio anderssoni Lowe) was thought to have become extinct sometime in the Late Pleistocene. Petroglyphs portray ostrich with Pleistocene animals, and ostrich eggshell (OES) fragments and ornaments from Holocene sites were considered to be older fossils. Here we summarize previous radiometric dates for ostrich eggshell (OES) and present 15 new calibrated accelerator mass spectrometry (AMS) dates, indicating that ostrich survived in Mongolia and northern China until at least 8.9 ka BP. The dates in our sample population suggest a correlation between Struthio and warm steppe environments, with extirpation probably related to essential changes in Holocene steppe ecosystems including human expansion. This study assesses the usefulness of Asian OES for archaeological dating by AMS, constrains the date of Asian ostrich extirpation, and investigates palaeoenvironmental implications of ostrich survival and extinction.  相似文献   
55.
This paper reports on a methodological study carried out in order to propose a cleaning procedure to remove stains produced by bronze corrosion products on surface of limestone (namely travertine); the procedure is effective and more environmentally friendly than the methods commonly used today. Several copper complexing or chelating agents were considered, including three amino acids and compared with some ion exchange resins. After a first laboratory phase on pure copper products and on artificially stained quarry samples, the optimized procedure was tested on the pedestal of a bronze statue in the Sapienza campus, in Rome. Colorimetry and ICP/OES were used to evaluate the efficiency of the cleaning procedure.  相似文献   
56.
Increasing evidence indicates that ongoing and future climate change impacts, such as enhanced coastal erosion driven by intensified storms and sea-level rise, will be destructive or problematic for coastal archaeological heritage. Approaches to this problem range from broad-scale GIS-based vulnerability assessments to site-scale monitoring and survey. In all cases, the approach chosen should be based on the best-available data on the local historic environment and pattern of coastal change. Therefore, this paper will demonstrate how such data can be successively acquired and enhanced using an integrated approach that builds on and refines a previously conducted broad-scale vulnerability assessment. This approach was adopted in the study region (Northern Ireland) owing to a lack of coherent and up-to-date information on shoreline change. This approach incorporated the GIS-based Digital Shoreline Analysis System (DSAS) to quantify and analyze local shoreline change. DSAS is a software extension for ESRI ArcGIS which allows calculation of rate-of-change statistics using past shorelines identified from georeferenced historic maps and vertical aerial imagery. Additionally, a field survey was conducted to assess the condition of recorded sites, and identify unrecorded ones. Results revealed a more complex pattern of shoreline change in the study area (Magilligan Foreland, Lough Foyle) than previously anticipated, with zones of significant erosion interspersed with areas of stability or advance. Fifty-one new sites ranging from the prehistoric period to the Second World War were also identified. The new information was used to develop a priority classification based on site significance, condition and risk level which improved significantly on the uniform classification of the original broad-scale assessment.  相似文献   
57.
From the Neolithic up to the present, people have used various methods to improve the surface of ceramic objects. In this study, we look specifically at smoothing and pattern burnishing of ceramics produced today by traditional methods. Optical microscopy and SEM show specific surface changes. Smoothing results in an irregular surface, which causes diffused reflection of light. Burnishing produces an even and compact surface, which causes specular reflection and lustre. The results can be used to infer methods of surface treatment employed by ancient peoples as well as to help identify the presence of ceramics production centres at archaeological sites.  相似文献   
58.
Nowadays, multi-image 3D reconstruction is an active research field and a number of commercial and free software tools have been already made available to the public. These provide methods for the 3D reconstruction of real world objects by matching feature points and retrieving depth information from a set of unordered digital images. This is achieved by exploiting computer vision algorithms such as Structure-From-Motion (SFM) and Dense Multi-View 3D Reconstruction (DMVR). In this work, we evaluate the performance of a low-cost commercial SFM–DMVR software by digitising a Cycladic woman figurine. Although the surface properties of the specific artefact are considered 3D laser scanner friendly, its almost featureless white-grey surface composes a challenging digitisation candidate for image based methodologies as no strong feature points are available. We quantify the quality of the 3D data produced by the SFM–DMVR software in relation to the data produced by a high accuracy 3D laser scanner in terms of surface deviation and topological errors. We question the applicability and efficiency of two digitisation pipelines (SFM–DMVR and laser scanner) in relation to hardware requirements, background knowledge and man-hours. This is achieved by producing a complete 3D digital replica of the Cycladic artefact by following both pipelines.  相似文献   
59.
60.
Slope soil erosion is one of the main threats to archaeological sites. Several methods were applied to establish the erosion rates at archaeological sites. Digital elevation models (DEMs) from three different dates were used. We compared the elevations from these three models to estimate erosion. We also applied the landscape evolution model LAPSUS with the available DEMs as basis. Spatial processing errors and effects of tillage and harvesting practices explain most of the DEM elevation differences between the recordings. Increased DEM resolution does not result in more precise or reliable erosion. The present technological level of landscape evolution modelling makes it possible to indicate areas most vulnerable to soil displacement by surface runoff erosion and tillage. Future research, using sediment and surface dating techniques such as deposit of radionuclides, heavy metals and OSL dating will provide a more accurate estimation of erosion rates and the subsequent impact on archaeological sites.  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