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   701篇
  免费   41篇
  2023年   8篇
  2022年   8篇
  2021年   3篇
  2020年   27篇
  2019年   23篇
  2018年   28篇
  2017年   22篇
  2016年   29篇
  2015年   25篇
  2014年   22篇
  2013年   138篇
  2012年   55篇
  2011年   43篇
  2010年   34篇
  2009年   29篇
  2008年   65篇
  2007年   30篇
  2006年   28篇
  2005年   16篇
  2004年   11篇
  2003年   7篇
  2002年   13篇
  2001年   15篇
  2000年   6篇
  1999年   4篇
  1998年   8篇
  1997年   9篇
  1996年   7篇
  1995年   6篇
  1994年   6篇
  1993年   1篇
  1992年   2篇
  1991年   1篇
  1990年   1篇
  1988年   2篇
  1986年   1篇
  1983年   1篇
  1982年   1篇
  1981年   1篇
  1980年   3篇
  1978年   3篇
排序方式: 共有742条查询结果,搜索用时 15 毫秒
701.
Excavations carried out in Tomb IX of the hypogeic necropolis of ‘Sa Figu’, near the village of Ittiri (Sassari, Italy), supplied burnt human bone remains and pottery unambiguously referred to the Early Bronze Age (characterised by the local culture of ‘Bonnannaro’). Besides the anthropological study, we have investigated and evaluated the possibility of a funerary cremation practice in Sardinian pre‐history, a subject that has previously not been considered from a scientific point of view. Making use of a calibration procedure based on X‐ray diffraction (XRD) line‐broadening analysis, related to the microstructural properties, it was possible to estimate the combustion temperature to which the fragmented bones were subjected. It was found that the studied bones reached temperatures varying from 400°C up to a maximum of 850°C. This spread of values suggested inhomogeneous combustion of the bones, which seems compatible with funerary cremation practices. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   
702.
703.
It is proposed that the vitrification in some Iron Age forts in NW Scotland can be explained through decomposition of micas (largely biotite) giving melts that react with or dissolve quartz and crystallise orthopyroxene and feldspars, so equating with the reaction biotite + quartz = sanidine + orthopyroxene + liquid. A sample of Moine semi-pelite has been experimentally melted at c. 850 °C demonstrating this breakdown reaction. A preserved thermal gradient across the sample reveals the progressive degradation of biotite towards the melting (upper) surface. Degradation is evident from the initial emphasis of mica cleavages in grains at the bottom of the sample, and then appearance and progressive increase in size of bubbles associated with biotite and melt towards the top of the sample. A chocolate-brown melt was produced as a coating on the upper surface and along micaceous layers. A near equivalent sample was located from the fort at The Torr that, whilst being more thoroughly affected by heat, with no unaffected biotite, preserved similar textures. Compositions of original Moine minerals are used to constrain the melts produced and melt evolution is tracked through quenched crystals. These include ternary feldspars as well as sanidine, spinels and orthopyroxene. Spot geochemical evidence demonstrates the heterogeneity of the melts, plus varying contributions of Ca and Na that could be attributed to the onset of reactions involving feldspars and other minerals from the original assemblage. It is thus concluded that a similar temperature to that of c. 850 °C derived in the experiment was reached in the vitrification process at The Torr in order to produce the glass observed.  相似文献   
704.
The division of land on Dartmoor during the Bronze Age by the construction of moor-wide boundaries known as reaves represents a significant development in agricultural practice and land tenure. Previous research relating to the Dartmoor reaves suggests this way of life may have continued for no longer than 200–400 years. It has been suggested that their abandonment occurred as the result of a deteriorating climate, although there are no published palaeoclimatic reconstructions from the area. We therefore test the hypothesis that on Dartmoor, a marked climatic deterioration occurred in the late Bronze Age that can be linked to the abandonment of the reaves. A palaeoclimatic reconstruction derived from testate amoebae and peat humification analyses is presented from Tor Royal Bog, central Dartmoor, the first such record from southwest England. A major shift to a cooler and/or wetter climate is inferred from ca. 1395 to 1155 cal BC that is coincident with the period hypothesised as encompassing the abandonment. This climatic deterioration is replicated in sites in northern Britain, suggesting it was a widespread event. It is concluded that while the evidence supports a climatically forced retreat, there are a range of other socio-economic factors that must also be taken into consideration.  相似文献   
705.
The aim of this study was to test with non-adult skeletons the quality of a recently published dental age assessment method based on Bayes' theorem. The test sample consisted of dental X-rays from 16 individuals (range 2.6–15.1 years) recovered from the crypt of Christ Church, Spitalfields, London, for which age-at-death and sex were known. The training sample consisted of dental X-rays from 1346 girls and 1040 boys (range 1.9–16.0 years). Bayesian dental age assessment method was alternatively used with dependent and independent assumptions; the dependent Bayesian method (DBM) and independent Bayesian method (IBM), respectively. Moreover, both DBM and IBM were used alternatively with sex-specific standards and with non-sex-specific standard. Due to the training sample age distribution, both methods are efficient between 5.0 and 14.0 years. Whatever the method or the sex standard used, when dental age was different from chronological age, the discrepancy did not exceed one age group of one year. DBM produced tighter dental age 100% confidence intervals than IBM for the majority of assessments. The observed stability between results produced according to the type of sex standard used (i.e. sex-specific or non-sex-specific), and the number of teeth studied (range 4–7), is worthy of note for both archaeological and forensic contexts.  相似文献   
706.
Inlaid ceramics belonging to the Encrusted Pottery Culture and dated to the Middle Bronze Age (2000–1500 BC) are highly distinctive vessels with complex decorative motifs found in large numbers in the Transdanubia region of Hungary. Despite this considerable corpus of material there has been little systematic investigation of the composition of the inlays. Micro-analysis of Transdanubian inlaid wares by X-ray diffraction (XRD), micro-Fourier transform infrared microscopy (FT-IR), and scanning electron microscopy (SEM) provides new compositional, structural and textural information on the inlays. In contrast to common statements in the literature regarding the materials used to make inlays, these new data show that the majority of inlays are composed of hydroxyapatite (bone) that was previously ashed, although some of the inlays are composed of calcium carbonate. Additional compositional and textural variation in the bone inlays suggests that bone material from different skeletal elements and/or of different age may have been used, and that contrasting recipes for inlay preparation were employed during fabrication. These results suggest that the production of inlaid vessels of the Encrusted Pottery Culture was more complex than has hitherto been thought.  相似文献   
707.
We use NAA to characterize a relatively large archaeological ceramic sample from the Late Bronze Age to Hellenistic phases of Kinet Höyük, a coastal Turkish site in the Gulf of Iskenderun at the northeast corner of the Mediterranean Sea. The geographic extent of local Kinet wares (how local is local?) is established through comparison with sediment samples across the Kinet hinterland. Four major compositional groups are identified: local and locally imported wares, imports from Cypriot, and presumed Western Anatolian and Aegean centers, and imports that appear relatively homogenous elementally but comprise typologically diverse ceramics with attributions that range from Cyprus to the coastal mainland. Comparison with other published NAA studies for this site reinforces the elemental evidence for local production, and underlines the need for caution when assuming local production always equates with local clays particularly for coastal sites. We propose that the chronological distribution of the local and non-local groups provides a useful political economic proxy. The study indicates systemic and widespread political disruption and marginalization at the transition to the Late Iron Age in this region.  相似文献   
708.
This paper reports on a piece of engraved ochre recovered from a Middle Stone Age context at the rock shelter site of Klein Kliphuis (Western Cape, South Africa). The ochre was associated with a mixed assemblage of Howiesons Poort and post-Howiesons Poort MSA artefacts, suggesting that it is substantially younger than similar finds at Blombos Cave. The implications of the find for arguments concerning the nature of Late Pleistocene behavioural evolution are discussed.  相似文献   
709.
In the South Caucasus—roughly the territory of today's Armenia, Georgia, and Azerbaijan—the transition from the Middle Bronze Age (MBA) to the Late Bronze Age (LBA) is equated with fundamental shifts in settlement patterns, subsistence economy, and political strategies. During the mid-2nd millennium BC, nomadic pastoral societies that had dominated the region began to settle down and construct stone fortresses along the foothills of the Lesser Caucasus; these fortifications largely replaced the expansive and often opulently adorned kurgan burials as the most prominent expression of political dominance on the landscape. After a decade of intensive archaeological study at various fortifications, very little remains known about the political and economic relationships among fortresses on a regional scale that might improve our understanding of the roots of these sociopolitical transformations. In this paper, we highlight the results of a recent neutron activation analysis (NAA) of ceramics from elite and non-elite contexts at a selection of LBA fortresses on the Tsaghkahovit Plain in northwestern Armenia, and offer some preliminary interpretations about political and economic organization and boundary formation. Most strikingly, the NAA data suggest that the fortresses on the Tsaghkahovit Plain appear to have isolated themselves economically from surrounding valleys, perhaps in an attempt to forge boundaries and legitimating ideologies attendant to new political formations that were quite distinct from their nomadic predecessors in the MBA.  相似文献   
710.
The normalised difference vegetation index (NDVI) has evolved as a primary tool for monitoring continental‐scale vegetation changes and interpreting the impact of short to long‐term climatic events on the biosphere. The objective of this research was to assess the nature of relationships between precipitation and vegetation condition, as measured by the satellite‐derived NDVI within South Australia. The correlation, timing and magnitude of the NDVI response to precipitation were examined for different vegetation formations within the State (forest, scrubland, shrubland, woodland and grassland). Results from this study indicate that there are strong relationships between precipitation and NDVI both spatially and temporally within South Australia. Differences in the timing of the NDVI response to precipitation were evident among the five vegetation formations. The most significant relationship between rainfall and NDVI was within the forest formation. Negative correlations between NDVI and precipitation events indicated that vegetation green‐up is a result of seasonal patterns in precipitation. Spatial patterns in the average NDVI over the study period closely resembled the boundaries of the five classified vegetation formations within South Australia. Spatial variability within the NDVI data set over the study period differed greatly between and within the vegetation formations examined depending on the location within the state. ACRONYMS AVHRR Advanced Very High Resolution Radiometer ENVSAEnvironments of South Australia EOS Terra‐Earth Observing System EVIEnhanced Vegetation Index MODIS Moderate Resolution Imaging Spectro‐radiometer MVC Maximum Value Composite NDVINormalised Difference Vegetation Index NIRNear Infra‐Red NOAANational Oceanic and Atmospheric Administration SPOT Systeme Pour l’Observation de la Terre  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