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   558篇
  免费   53篇
  2024年   6篇
  2023年   16篇
  2022年   6篇
  2021年   5篇
  2020年   16篇
  2019年   23篇
  2018年   76篇
  2017年   55篇
  2016年   57篇
  2015年   37篇
  2014年   38篇
  2013年   111篇
  2012年   24篇
  2011年   18篇
  2010年   17篇
  2009年   13篇
  2008年   15篇
  2007年   7篇
  2006年   1篇
  2005年   6篇
  2004年   4篇
  2003年   5篇
  2002年   9篇
  2001年   6篇
  2000年   5篇
  1999年   3篇
  1998年   1篇
  1997年   2篇
  1996年   6篇
  1995年   2篇
  1994年   2篇
  1993年   3篇
  1992年   1篇
  1989年   3篇
  1988年   1篇
  1985年   4篇
  1984年   2篇
  1983年   1篇
  1982年   1篇
  1981年   1篇
  1975年   1篇
  1973年   1篇
排序方式: 共有611条查询结果,搜索用时 31 毫秒
41.
A. Tarriño 《Archaeometry》2015,57(5):928-948
A new classification system is proposed to describe the volumetric formats of clastic lithic products of geological and archaeological origin. In order to build this operative classification, the rectangular block or cuboid is established as the standard geometric format to represent their three‐dimensional format (the X‐axis being length or long diameter, the Y‐axis being the width or intermediate diameter, and the Z‐axis being the thickness or short diameter) on a two‐dimensional diagram. To obtain this graph, each absolute coordinate (X, Y, Z) defining the prisms is projected on to an auxiliary plane with a new set of relative coordinates (x, y, z), expressed as the percentage of their sum. The projection generates a triangular diagram on which the indices of elongation and flatness are represented. A geometric transformation converting the triangular diagram into a quadrangular diagram has been produced in order to better represent the scatter points. Then, a double scale is necessary: (i) an absolute scale to quantify the indices, and (ii) a relative scale to calculate where the graphic locus is projected. This new graph also allows us to work with statistical parameters. Finally, two classic examples of applications selected from the literature are shown.  相似文献   
42.
Twenty‐six samples from domestic assemblages of 9th–12th century Córdoba were subjected to electron microprobe analysis. The results reveal two main compositional types. The first, encountered in 13 of the samples, seems to result from the combination of plant ashes with high‐impurity sand, and has some contemporary parallels from Syria and Egypt. The second type is a lead–soda–silica glass, encountered in a relatively high proportion of the glasses (11 of the 26 sampled), possibly formed by the addition of lead metal to existing glasses and with very few known parallels. These are among a very small number of results available to date on the chemical composition of glasses from medieval Spain, and the presence of a high proportion of lead–soda–silica glasses is particularly interesting, possibly indicating a technological practice unique to, or originating in, the western Muslim world.  相似文献   
43.
In this work, we present the results of the characterization of 20 lime plaster samples taken from the Sacred Precinct of Tenochtitlan (Mexico City), the ancient capital of the Aztec empire. The samples come from different buildings of this precinct (A, B and D) and from the west façade of phase VI of the Templo Mayor pyramid. The objective of the work is to characterize the plaster samples, to understand the raw materials used, and to evaluate the presence of similarities and differences among the samples in the building techniques and raw materials employed. All the samples were studied with OM, SEM–EDS and LA–ICP–MS. The study provided evidence of the plastering and replastering practice in the same constructive phases. The results of the analyses showed the existence of important similarities and differences among buildings and constructive phases in the Sacred Precinct. In order to understand the provenance of the limestone used in the plasters, the lumps and the binder of the samples were analysed. The results were compared with those of the limestone outcrops located in central Mexico. The provenance study showed that all the limestone used in the construction of the analysed buildings of Tenochtitlan's Sacred Precinct comes from the Tula region.  相似文献   
44.
45.
46.
47.
López-Gappa, J., Pérez, L.M. & Griffin, M. February 2017. First record of a fossil selenariid bryozoan in South America. Alcheringa XX, xxx-xxx. ISSN 0311-5518.

Selenariidae Busk 1854 (Bryozoa) is considered endemic to Australia and New Zealand. Here we describe a new species of Selenaria Busk 1854 from the lower Miocene Monte León Formation (Patagonia, Argentina). Selenaria lyrulata sp. nov. is characterized by autozooids with a lyrula-like, anvil-shaped cryptocystal denticle, opesiular indentations and lateral condyles, as well as avicularia with a shield of fused costae. This is the first record of a selenariid bryozoan in South America.

Juan López-Gappa [] CONICET—Museo Argentino de Ciencias Naturales. Av. Ángel Gallardo 470, C1405DJR, Ciudad Autónoma de Buenos Aires, Argentina; Leandro Martín Pérez [] and Miguel Griffin [], CONICET—División Paleozoología Invertebrados, Museo de La Plata. Paseo del Bosque s/n, B1900FWA, La Plata, Argentina.  相似文献   

48.
ABSTRACT

This paper contributes to the study of the role of public policies in the origins and evolution of clusters. Building on the existing literature, we set up a taxonomy of nine public policies that may have an impact on the emergence and evolution of clusters. Based on in-depth case studies of six clusters of the Basque Country, particularly representative of the industrial history of the region, we analyse the relevance of the different types of policies both in the emergence and evolution of clusters over time. In agreement with cluster literature, the paper concludes that public policies seem to have played only an indirect role across clusters and over their life cycles. Moreover, it points to the necessity of taking history and context into account, as most of the important policy measures highlighted by cluster literature today do not fit well with the previous policy and economic context. Finally, it also concludes that for cluster policies to be effective, the stages of the life cycle should be taken into consideration.  相似文献   
49.
ABSTRACT

The concept of topoiesis of textual space addresses an analysis of the spatial elements that tend to provide a meaning to the literary text. Based on textual semiotics where there is an organized relational system of meanings, in this article we propose that it is possible to determine the function of space as a meaning issue from three different literary text instances (event or motive; character; and object). This distinction will permit a deeper interpretation of the sense of space in the literary text.  相似文献   
50.
Despite phytoliths having been used to understand past human use of plants and palaeoenvironment in Middle Paleolithic sites, little is known on this aspect in the well-documented central region of Mediterranean Iberia. This paper presents the first phytolith and mineralogical study conducted at Abrigo de la Quebrada (Chelva, Valencia). Forty-one samples were analyzed through phytoliths and Fourier transform infrared spectroscopy (FTIR) from different areas, stratigraphic levels, and archeological contexts (hearth, hearth-related, and non-hearth-related sediments) of the shelter. The results obtained point towards a different pattern of preservation in the site depending firstly on the stratigraphy and secondly on the area where the samples were collected. Postdepositional processes that may have chemically affected phytolith preservation are discussed. Grasses are the main plant component identified in all the samples while woody plants are scarce. The abundance of grasses in the non-hearth-related sediments might be related, at least partially, to the dispersion of ashes from hearths, as indicated by the FTIR results. The results are indicative of an occupation of the site during the spring-autumn season. At this time, the area would be dominated by a semi-open environment with supramediterranean vegetation.  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