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   722篇
  免费   59篇
  2024年   1篇
  2023年   24篇
  2022年   3篇
  2021年   9篇
  2020年   39篇
  2019年   38篇
  2018年   104篇
  2017年   76篇
  2016年   66篇
  2015年   48篇
  2014年   39篇
  2013年   151篇
  2012年   36篇
  2011年   25篇
  2010年   18篇
  2009年   17篇
  2008年   18篇
  2007年   13篇
  2006年   4篇
  2005年   3篇
  2004年   1篇
  2003年   1篇
  2002年   6篇
  2001年   9篇
  2000年   4篇
  1999年   1篇
  1998年   1篇
  1997年   4篇
  1996年   2篇
  1995年   8篇
  1994年   3篇
  1993年   2篇
  1992年   3篇
  1987年   1篇
  1985年   1篇
  1982年   1篇
  1979年   1篇
排序方式: 共有781条查询结果,搜索用时 187 毫秒
91.
The implementation of a 3D Electrical Resistivity Tomography (ERT-3D) survey was carried out in El Pahñú archaeological site, Hidalgo State, Central Mexico. A combination of a new ERT arrays allowed studying the subsoil beneath the Main Pyramid built near the edge of a plateau, along with another important structure (the Tecpan), which was a smaller structure that lodged the governmental council in pre-Hispanic times. The recorded information was acquired through the combination of several electrodic designs: L-Corner (LC), Equatorial (Eq), and Minimum Coupling (MC). For the Main Pyramid, the electrodes were set up around the perimeter of the structure, since they were not permitted to be inserted over the edifice, thus preventing damages to the architectonic elements. The second structure allowed inserting electrodes on selected spots within the architectonic space. The combination of the different arrays made possible the acquisition of 1204 apparent resistivities beneath the Main Pyramid and 2460 resistivity data beneath the Tecpan. The apparent resistivity data were inverted to obtain a three dimensional display of the subsoil electrical resistivity beneath the archaeological structure. The interpreted resistivity model under the Main Pyramid displayed a highly resistive structure towards its northern face that could be associated with infill. Such material was employed by the ancient constructors to level the terrain close to the edge of the cliff. Another interesting anomaly was found towards the central portion of the structure that could be associated to a foundation offer. The interpretation of data beneath the Tecpan identified the structural foundations and other interesting anomalies related to the different occupational times. The investigation supported the archaeological investigation of the site, suggesting areas of potential geological risk and of archaeological interest. For example, the Main Pyramid presents serious stability problems, indicating that the infill has weakened, producing cracks threatening long-term pyramid integrity.  相似文献   
92.
The marsh deer (Blastocerus dichotomus, Illiger, 1815) is the largest contemporary South American deer, and its habitat includes the floodplains and wetlands of eastern South America. Throughout the Holocene these deer were widely used by indigenous societies, from the southern banks of the Amazon River to the Río de la Plata River, and from the Andean foothills to the Atlantic Ocean. However, despite the enormous ecological and archaeological importance of this ungulate in the region, our knowledge of the isotopic values of their diet is almost nonexistent. This paper is the first systematic approach to the study of the isotopic values of this mammal's diet, using archaeological and present-day samples from interconnected watersheds of the Paraná and Uruguay rivers in east-central Argentina. The results obtained from 24 measurements indicate an average value of ?21.09 ± 1.46‰ in δ13C collagen, with a low coefficient of variation (6.92%). The data indicate a marked preference for consumption of plants with a C3 photosynthetic pathway. Most of the observed variability in the isotopic values corresponds to the period 900–1430 14C years BP, a time range during which the values show higher consumption of C4 plants. This it could be related with a period where temperature and associated humidity increased, synchronous in the area with the Medieval Climate Anomaly.  相似文献   
93.
The phenomenon of equifinality complicates behavioral interpretations of faunal assemblages from contexts in which Pleistocene hominins are suspected bone accumulators. Stone tool butchery marks on ungulate fossils are diagnostic of hominin activities, but debate continues over the higher-order implications of butchered bones for the foraging capabilities of hominins. Additionally, tooth marks imparted on bones by hominins overlap in morphology and dimensions with those created by some non-hominin carnivores, further confounding our view of early hominins as meat-eating hunters, scavengers or both. We report on the manual/oral peeling of cortical layers of ungulate ribs as taphonomically diagnostic of hominoid/hominin meat- and bone-eating behavior that indicates access to large herbivore carcasses by hominins at the site of BK, Olduvai. Supporting these inferences, we show that certain types of rib peeling damage are very rare or completely unknown in faunas created by modern carnivores and African porcupines, but common in faunas modified by the butchery and/or consumption activities of modern humans and chimpanzees, during which these hominoids often grasp ribs with their hands, and then used their teeth to peel strips of cortex from raggedly chewed ends of the ribs. Carnivores consume ungulate ribcage tissues soon after kills, so diagnostic traces of hominin butchery/consumption on ribs (i.e., peeling and butchery marks) indicate early access to ungulate carcasses by BK hominins. Tooth marks associated with the peeling and butchery marks are probably hominin-derived, and may indicate that it was not uncommon for our ancestors to use their teeth to strip meat from and to consume portions of ribs. Recognition of rib peeling as a diagnostic signature of hominoid/hominin behavior may also aid the search for pre-archaeological traces of hominin meat-eating.  相似文献   
94.
The fundamental frequency of a structure enables better assessment of its seismic demand for an efficient design and planning of its maintenance and retrofit strategy. The frequency is independent of the type of external loads, however, depends on structural stiffness, mass, damping and boundary conditions. In the case of slender masonry structures such as towers, minarets chimneys, and pagoda temples, it is influenced by mass and stiffness distribution, connection to adjacent structures, material properties, aspect ratio and slenderness ratio. In this present article, the data collected from various literature reviews on the slender masonry structures regarding dynamic, geometrical, and mechanical characteristics have been correlated to identify the major parameters influencing the fundamental frequency of such structures. The database has been used for developing an empirical formulation for predicting the fundamental frequency of such structures. The comparison between the experimental fundamental frequencies and the estimated fundamental frequencies are carried out in order to define reliability and accuracy of these empirical formulae.  相似文献   
95.
A new approach is developed for vulnerability analysis of monuments based on a matrix model and the relationships with static and structural factors, climatic conditions, air quality, urban planning and social agents for preventive conservation of cultural heritage in urban centers.

The objective is to provide tools for decision-makers in the current recession to allow them to prioritize strategies for cultural heritage preservation in a town, where territorial policies are applied and regions where restoration budget is distributed. This new tool allows to classify monuments in order to prioritize restoration and is useful in deeper analysis associated to risks assessment.

The degradation of building materials and structures is mainly due to deterioration caused by structural instability, weathering, pollution, and anthropogenic damage. The vulnerability approach of each monument (vulnerability indexes) was calculated, based on a Leopold matrix that depends on intrinsic variables and the life of the monuments. For the very first time, the influence of different deterioration agents has been balanced with a Delphi forecast based on architects’ opinions.

The result is a new pre-Artificial Intelligence tool that enables users to reproduce human reasoning to study relations between vulnerability factors, risk factors, and the historical parameters of the monuments.  相似文献   

96.
This article studies the impact of colonial rule on Andean hierarchies of power, underlining the role of lower-level native leaders who enabled paramount lords to organize labor services, levy tribute, and govern Andean polities. Using the repartimiento of Macha (Charcas) as a case study, this article examines the impact of external colonial authorities' actions against the backdrop of rising internal tensions within Andean polities. Segmented polities such as Macha faced increasing tensions, giving rise to new mediating roles for lesser-ranking native leaders, placing the subordinate lords' fight for status at the center of debate. This article starts by exploring the first interrelations between lesser-ranking lords and colonial authorities under the encomienda system through the late 1560s. It then turns to the impact of Viceroy don Francisco de Toledo's reforms in the early 1570s, which simplified and standardized native hierarchies of power within each repartimiento while also fragmenting local Andean elites between tribute-paying lords and those exempted of from it. Finally, the article examines the reactions of lower-level native leaders in the face of new constraints regarding tribute exemption and related obligations in the early seventeenth century, as exemplified by indio principal don Diego Chambi.  相似文献   
97.
98.
We present radiocarbon dates and preliminary micromorphological information from the Neolithic cave site of Cueva del Toro (Antequera, Málaga, Spain). This site has yielded a rich early and late Neolithic archaeological record. The late Neolithic assemblage reflects specialized handcraft activity including in situ ceramic manufacture, textile production, and food processing along with sheep and goat penning, suggesting that the cave occupants and their domestic animals shared the same living space. Until now, dating of the stratigraphic sequence was incomplete, and the function of the combustion activities carried out at the cave remained unclear. New absolute dates from the main late Neolithic domestic activity area, corresponding to the most intense Neolithic occupation of the cave, allow us to place the entire sequence between 5320 and 5170 BP (or 4250–3950 to 2σ Cal BC). Micromorphological results show that many combustion features from this site represent recurrently burnt episodes on sheep/goat stabling deposits all along the sequence, corroborating human-goat/sheep cohabitation. This practice had not been previously documented in southern Spain for such early dates. Our results exemplify the importance of characterizing archaeological deposits at a microstratigraphic scale of observation.  相似文献   
99.
ABSTRACT This paper surveys recent evidence on the determinants of (national and/or foreign) industrial location. We find that the basic analytical framework has remained essentially unaltered since the early contributions of the early 1980s while, in contrast, there have been advances in the quality of the data (more firm and plant level information, geographical disaggregation, panel structure, etc.) and, to a lesser extent, the econometric modeling. We also identify certain determinants (neoclassical and institutional factors) that tend to provide largely consistent results across the reviewed studies. In light of this evidence, we finally suggest future lines of research.  相似文献   
100.
Esquilleu cave site has provided a moderately well preserved archaeological cave deposit from the Late Pleistocene in the Cantabrian area. Phytolith quantification, identification and determination of the refractive index have been carried out, together with FTIR analyses, from sediment samples collected in the profile. The comparison of the data obtained with the previous micromorphological results allows us to make inferences about the site formation processes and the Neanderthals use of the cave. Phytolith results show the presence of grass leaves nearby the hearth suggesting the repetitive existence of a bedding zone on the same area. Neanderthal behavioral patterns should be revised on the light of high resolution analyses, since diagenetic processes can obscure the existence of differentiated activity areas in the site.  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