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   55篇
  免费   0篇
  2021年   1篇
  2020年   3篇
  2019年   6篇
  2017年   1篇
  2016年   1篇
  2015年   2篇
  2013年   14篇
  2012年   2篇
  2011年   2篇
  2010年   4篇
  2009年   1篇
  2004年   1篇
  2003年   4篇
  2002年   1篇
  2001年   3篇
  1999年   1篇
  1997年   1篇
  1992年   2篇
  1984年   1篇
  1981年   1篇
  1970年   2篇
  1969年   1篇
排序方式: 共有55条查询结果,搜索用时 31 毫秒
31.
Investigators have long recognised the effects of microbial activity on archaeological bone. These investigators, however, have focused on single or groups of microbes rather than on complex microbial aggregates such as biofilms, a focus that has affected our understanding of archaeological bone biodeterioration. In this paper, we report on the investigation of a biofilm in archaeological human bone from the site of Tell Leilan, Syria (2900–1900 BCE). Scanning electron microscopy indicated that the biofilm is characterised by single cells and microcolonies of bacteria and fungi, as well as calcite crystals that were all embedded within extracellular polymeric substances. Using culture techniques and DNA sequencing, we isolated and identified several microbes from the biofilm including Amycolatopsis sp., Penicillium chrysogenum, Aspergillus sp., Chaetomium sp., and Cladosporium sp. Having characterised the Leilan biofilm, we are now closer to understanding the complex process of bone biodeterioration in archaeological bone collections.  相似文献   
32.
This paper connects philosophical debate concerning the metaphysics and epistemology of counterfactuals to the methodological concerns of historical geography. It argues that counterfactual claims are implied by a wide range of common epistemic judgements, specifically those regarding evidential support and explanatory connection. In addition it argues against those who have sought to restrict the use of counterfactuals to, in particular, rational action, or systems that are inherently chancy. Rather it argues in favour of an expanded role for counterfactual method in history and geography, in the forms of imaginary experiments and the questioning of ‘what might have been’.  相似文献   
33.
Ceramic vessels and associated vitreous debris, excavated at Coppergate, York, UK, have been interpreted as the remains of Roman glass‐making from the raw materials. This paper reports the results of analysis of this assemblage by XRF, ICPS, XRD, SEM– EDAX and thin‐section petrography. These findings suggest that some ceramic vessels, used as crucibles, have been subjected to temperatures up to 1200°C, well above the firing temperatures of the local domestic assemblage from which they were selected. Analysis of quartz‐rich debris, intimately mixed with glass in some samples and in others interleaved with glassy phases, indicates partially reacted glass‐making raw materials, with α‐quartz, tridymite and cristoballite phases represented. This could represent evidence either of a failed attempt to frit the raw materials, or a batch that had not fully fused. Variability in the composition of glass at the site is viewed in the light of glass‐making technology, and possible interpretations concerning this episode are discussed in the light of the archaeological evidence.  相似文献   
34.
This Term, the Historical Society has put on a wonderful series about the man who is widely—and rightly—regarded as this Court's greatest Chief Justice. Through his recognition of the right of judicial review, John Marshall secured for this Court a role in shaping the nation's most important principles: racial equality, individual liberty, the meaning of democracy, and so many others.  相似文献   
35.
In Mexico, as in many other parts of the world, industrial agriculture is dramatically changing rural landscapes and altering relationships with the land. This paper draws on community‐based research from a collaborative international research project that examined the perceived health implications of the agricultural industry for Indigenous peoples in the state of Jalisco, Mexico. Thirty interviews were conducted in a Nahuas community experiencing expanding agribusiness industries. The results of this study show that the implications of export‐oriented agricultural industry for this Nahuas community are complex and, at times, contradictory: employment in the agricultural industry provides community members with much‐needed sources of income, but it is precarious work. At the same time, community members are concerned about the long‐term health and environmental implications, such as increased exposure to chemicals, depletion of the soil and water, and loss of traditional food and lifeways. These results suggest that to better understand the costs and benefits of large‐scale agriculture for Indigenous health, a broad lens of health that is situated in the context of colonial legacies and the particularities of relationships with the land is required.  相似文献   
36.
The absence of studies investigating the influence of political participation on individuals’ perceptions of political efficacy constitutes a significant gap in our knowledge of political behaviour. While many researchers have investigated the influence of efficacy on political participation, and there has been some endeavour to examine the reciprocity of the relationship between the variables, none has estimated a comprehensive model of the impact of individuals’ participation is different kinds of political activity on different aspects of their perceptions of political efficacy. We redress these particular deficiencies in our knowledge of political behaviour, investigating the influence of participation in three different modes of activity—partisan activism, community activism and political extremism—on individuals’ perceptions of internal and external efficacy; that is, their perceptions of political self‐competence and system responsiveness. Our findings confirm that the relationships between different modes of participation and efficacy are both reciprocal and varied, and that they vary in ways which have important implications for theories of participatory democracy.  相似文献   
37.
CHARMed PyMca is a protocol for researchers using energy‐dispersive X‐ray fluorescence spectroscopy (ED‐XRF) who wish to maximize interlaboratory reproducibility of quantitative results from copper alloys found in heritage materials. This paper reports the results of a study evaluating the interlaboratory reproducibility expected when following this protocol. Five institutions participated in this study, using nine tube‐based instruments of seven types. A set of 12 reference materials not used for calibration was analysed according to the protocol. The results show an improvement in reproducibility of between 65% and 83%, depending on the element, in comparison with a similar study carried out in 2010. The protocol allowed the consistent reporting of concentrations for 15 elements, in contrast to only eight elements that were reported in the 2010 study. Finally, the protocol was shown to generate accurate quantitative results with a well‐characterized precision. It is hoped the information presented here can help researchers studying heritage copper alloys to collaborate more effectively and with greater confidence in the reproducibility of their results. It should also aid researchers to make realistic and informed decisions about whether or not the degree of reproducibility that they may expect from ED‐XRF makes the protocol suitable for their specific purposes.  相似文献   
38.
Falling trees commonly turbate soils in primary forest, creating characteristic edaphic patterns related to pit and mound topography. Vernal ponds with associated mounds were observed in mineral soils on a treeless plain in subalpine Tasmania, Australia. The hypothesis that paired ponds and mounds on the plain originated as pit and mound features in forests that were later destroyed by fire was tested by comparing the soils and landforms caused by recent tree falls in adjacent forest with those on the plain. The soil characteristics, orientations, and dimensions of the ponds and mounds were consistent with a tree fall origin, although rare secondary ponds on the tops of mounds may derive from the burrowing activities of the medium‐sized marsupial, Vombatus ursinus (common wombat). The characteristics of pond and mound soils suggested that most were hundreds to thousands of years old, with the ponds persisting because of differences in deflation, deposition, and organic matter formation between themselves and adjacent persistently dry land.  相似文献   
39.
The formation of reference groups comprises an important procedure in chemical provenance studies of archaeological pottery. Material from ancient kilns is thought to be especially suitable for reference groups, as it comprises a definite unit of past production. Pottery from the Late Minoan IA kiln excavated at Kommos, Crete was analysed in order to produce a reference group in this important area of Minoan ceramic production. The samples were characterized by a combination of techniques providing information on the chemistry, mineralogy and microstructure of the ceramic body. Initially, the study was unable to establish, in a straightforward manner, a chemical reference group. Different ceramic pastes and a range of selective alterations and contaminations, affected by variable firing temperatures and burial environment, were shown to be responsible for the compositional variability. Procedures are described to compensate for such alterations and the perturbations in the data that they produce.  相似文献   
40.
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