全文获取类型
收费全文 | 3074篇 |
免费 | 138篇 |
出版年
2020年 | 54篇 |
2019年 | 53篇 |
2018年 | 101篇 |
2017年 | 101篇 |
2016年 | 94篇 |
2015年 | 63篇 |
2014年 | 84篇 |
2013年 | 1060篇 |
2012年 | 84篇 |
2011年 | 84篇 |
2010年 | 78篇 |
2009年 | 66篇 |
2008年 | 72篇 |
2007年 | 61篇 |
2006年 | 52篇 |
2005年 | 35篇 |
2004年 | 50篇 |
2003年 | 41篇 |
2002年 | 32篇 |
2001年 | 30篇 |
2000年 | 24篇 |
1999年 | 29篇 |
1998年 | 27篇 |
1997年 | 23篇 |
1996年 | 19篇 |
1995年 | 23篇 |
1994年 | 27篇 |
1993年 | 19篇 |
1992年 | 24篇 |
1989年 | 23篇 |
1988年 | 18篇 |
1987年 | 19篇 |
1986年 | 20篇 |
1985年 | 24篇 |
1984年 | 30篇 |
1983年 | 31篇 |
1982年 | 23篇 |
1981年 | 24篇 |
1980年 | 25篇 |
1979年 | 29篇 |
1978年 | 29篇 |
1977年 | 28篇 |
1976年 | 24篇 |
1975年 | 25篇 |
1974年 | 18篇 |
1973年 | 26篇 |
1972年 | 18篇 |
1971年 | 22篇 |
1970年 | 17篇 |
1969年 | 23篇 |
排序方式: 共有3212条查询结果,搜索用时 31 毫秒
201.
202.
203.
I. Casar P. Morales L. R. Manzanilla E. Cienfuegos F. Otero 《Archaeological and Anthropological Sciences》2017,9(1):99-115
This study examines the diet consumed by the population at the neighborhood center of Teopancazco, Teotihuacan, in the basin of Mexico. We used stable isotope analysis of δ13C and δ15N of the dentine collagen as well as the δ13C from enamel bioapatite from teeth (M2 and M3) of 39 of excavated burials. The results show that the diet consumed by the majority of the population during childhood and adolescence had high 13C enriched values in both dietary components: δ13C enamel_bioapatite = ?2.0 ‰ ± 1.5 for the whole diet and δ13C dentine_collagen = ? 9.4 ‰ ± 2.1 for the protein component. According to the bi-variable and multivariable models, some individuals consumed higher amounts of C4/CAM resources than those specified in cluster #2 (70 % C4 diet; ≥50 % C4/CAM protein). An inter-tissue adjustment of 2.3 ‰ was used to relate the enamel bioapatite data to the bone bioapatite of the models. Average δ15Ndentine_collagen was 10.2 ‰ ± 2.8 with high variability especially for four individuals, three of which belong to special burials, suggesting different access to meat or marine products due to their social or migration status and/or to pathological conditions. The data suggest that maize was the staple crop of the population not only at Teopancazco but for Teotihuacan as a whole, in the form of tortillas, tamales, atole, and protein from maize-fed animals with the inclusion of other CAM, C4, and C3 resources probably from the bountiful ecosystem of the basin of Mexico or from the wide trade system that Teotihuacan had with Mesoamerica. 相似文献
204.
Collaborative Networks for Effective Ecosystem‐Based Management: A Set of Working Hypotheses 下载免费PDF全文
Ecosystem‐based management (EBM) represents a comprehensive approach to better govern the environment that also illustrates the collaborative trend in policy and public administration. The need for stakeholder involvement and collaboration is strongly articulated, yet how and for what purposes collaboration would be effective remains largely untested. We address this gap by developing and evaluating a set of hypotheses specifying how certain patterns of collaborations among actors affect their joint ability to accomplish EBM. Content analyses of management plans drawn from five EBM planning processes in Sweden are combined with analyses of the collaborative networks through which these plans have been developed. Our results indicate that system thinking and the ability to integrate across different management phases are favored by collaborations between different kinds of actors, and by project leaders being centrally located in the networks. We also find that dense substructures of collaboration increase the level of specificity in the plans in regards to explicating constraints on human activities. Having many collaborative ties does however not enhance the overall level of specificity. Our results also show that different network characteristics can give rise to similar EBM outcomes. This observed equifinality suggests there is no single blueprint for well‐performing collaborative networks. 相似文献
205.
The White Marble of the Arch of Augustus (Susa,North‐Western Italy): Mineralogical and Petrographic Analysis for the Definition of its Origin 下载免费PDF全文
The Arch of Augustus in Susa (north‐western Italy) was built in 9–8 bc by King Cottius, to celebrate the treaty between the Romans and the Gauls. It is made of white marble, which was considered for a long time to be locally extracted, but no archaeometric studies have been performed up to now. Therefore, a multi‐analytical study based on petrographic (optical and scanning electron microscopy), electron microprobe and stable isotope analyses was carried out on the marble from the arch and from reference samples, with the aim of defining the provenance. All the data confirmed that white marble belonging to the metamorphosed carbonate cover of the Dora Maira Massif, known as Foresto marble, was used for the Susa Arch. This choice was probably made for economic reasons, but also due to the relative independence of the ruling family of the Alpes Cottiae, which was obviously interested in promoting a local marble. 相似文献
206.
207.
J. Appleby T. K. Seetah D. Calaon S. aval A. Pluskowski J. F. Lafleur A. Janoo V. Teelock 《International Journal of Osteoarchaeology》2014,24(6):737-746
The cemetery of Le Morne in Mauritius dates from the 1830s and is thought to contain the remains of slaves, freed slaves or potentially free Madagascans, which in itself has economic and social implications and makes the cemetery all the more intriguing. During 2010, excavations recovered the remains of 11 individuals, of which six were children. Although a small sample, the burials of the non‐adults show several interesting features. Two neonates were buried contemporaneously and may have been twins, while a late term foetus in a grave with a young woman may represent an incident of coffin birth. This sample has the potential to cast light on the burial practices of the slave/ex‐slave community in Mauritius, about which little is currently known. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
208.
S. A. JimNez‐Brobeil M. G. Roca Z. Laffranchi T. NJera F. Molina 《International Journal of Osteoarchaeology》2014,24(5):649-659
One of the most interesting sites of the Bronze Age in the central area of the Iberian Peninsula is La Motilla del Azuer (Daimiel, Ciudad Real), dated between 2200 and 1350 bc . The main objective of this study was to investigate interpersonal violence in this site and to report an uncommon case of violent death. No traumatic injury was detected in any child, and men and women significantly differed in the frequency of traumas. More traumatisms were found in men from the earlier stages of occupation, including a young man with at least three blunt force traumas and 26 sharp force traumas. The archaeological findings and trauma patterns in the skeletons of the 65 individuals studied suggest a relatively intense level of exposure to violence for adult men in the earlier stages of occupation of this settlement. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
209.
210.
Structure‐ and tectonic‐related gas migration into Ordovician sandstone reservoirs and its impact on diagenesis history were reconstructed in two gas fields in the Sbaa Basin, in SW Algeria. This was accomplished by petrographical observations, fluid inclusion microthermometry and stable isotope geochemistry on quartz, dickite and carbonate cements and veins. Two successive phases of quartz cementation (CQ1 and CQ2) occurred in the reservoirs. Two phase aqueous inclusions show an increase in temperatures and salinities from the first CQ1 diagenetic phase toward CQ2 in both fields. Microthermometric data on gas inclusions in quartz veins reveal the presence of an average of 92 ± 5 mole% of CH4 considering a CH4‐CO2 system, which is similar to the present‐day gas composition in the reservoirs. The presence of primary methane inclusions in early quartz overgrowths and in quartz and calcite veins suggests that hydrocarbon migration into the reservoir occurred synchronically with early quartz cementation in the sandstones located near the contact with the Silurian gas source rock at 100–140°C during the Late Carboniferous period and the late Hercynian episode fracturing at temperatures between 117 and 185°C, which increased in the NW‐direction of the basin. During the fracture filling, three main types of fluids were identified with different salinities and formation temperatures. A supplementary phase of higher fluid temperature (up to 226°C) recorded in late quartz, and calcite veins is related to a Jurassic thermal event. The occurrence of dickite cements close to the Silurian base near the main fault areas in both fields is mainly correlated with the sandstones where the early gas was charged. It implies that dickite precipitation is related to acidic influx. Late carbonate cements and veins (calcite – siderite – ankerite and strontianite) occurred at the same depths resulting from the same groundwater precipitation. The absence of methane inclusions in calcite cements result from methane flushing by saline waters. 相似文献