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   507篇
  免费   31篇
  2023年   3篇
  2020年   11篇
  2019年   12篇
  2018年   24篇
  2017年   19篇
  2016年   26篇
  2015年   22篇
  2014年   15篇
  2013年   120篇
  2012年   17篇
  2011年   15篇
  2010年   18篇
  2009年   20篇
  2008年   17篇
  2007年   22篇
  2006年   20篇
  2005年   8篇
  2004年   10篇
  2003年   7篇
  2002年   8篇
  2001年   14篇
  2000年   7篇
  1999年   12篇
  1998年   3篇
  1997年   7篇
  1996年   6篇
  1995年   2篇
  1994年   3篇
  1993年   8篇
  1990年   5篇
  1989年   3篇
  1988年   5篇
  1985年   5篇
  1984年   5篇
  1983年   3篇
  1980年   7篇
  1979年   2篇
  1978年   3篇
  1977年   3篇
  1976年   2篇
  1975年   2篇
  1974年   3篇
  1972年   3篇
  1967年   2篇
  1966年   1篇
  1965年   1篇
  1964年   1篇
  1958年   1篇
  1956年   1篇
  1955年   1篇
排序方式: 共有538条查询结果,搜索用时 15 毫秒
21.
22.
23.
Telepresence-enabled exploration of deep sea environments has developed over the past 30 years, providing access to archaeologists, scientists, and the general public to sites otherwise inaccessible due to depth. Pioneered through the inception of the JASON Project in the late 1980 s, telepresence missions have expanded to two dedicated ships of exploration, NOAA Ship Okeanos Explorer and exploration vessel Nautilus, and has been implemented on a series of opportunistic missions on other vessels. This paper chronicles the history of the use of telepresence for the exploration of shipwrecks in deep water as well as how this capability has allowed the public to engage with such missions. Broadening the scope of who can explore the deep sea, telepresence has also expanded what is observed and documented in the deep, which speaks to humanity’s use of the maritime world and an archaeology of discard through our material disposed of into the deep sea.  相似文献   
24.
We investigated the contribution of freshwater resources to the diet of seven Late Mesolithic hunter-gatherers (ca. 5300–7000 BC) from Northern France and Luxembourg using stable isotope ratios. In addition to the carbon and nitrogen stable isotope ratios (δ13C, δ15N), we explored the potential of the sulphur isotopic ratios (δ34S) to detect and quantify the proportion of protein derived from aquatic foodstuff. In only two sites, animal remains from an associated settlement were available and subsequently examined to decipher the isotopic differential between terrestrial and freshwater resources. The quantification of their relative contribution was simulated using a Bayesian mixing model. The measurements revealed a significant overlap in δ13C values between freshwater and terrestrial resources and a large range of δ15N values for each food category. The δ34S values of the aquatic and terrestrial animals were clearly distinct at the settlement in the Seine valley, while the results on fish from Belgium demonstrated a possible overlap in δ34S values between freshwater and terrestrial resources. Local freshwater ecosystem likely contributed to ca. 30–40 % of the protein in the diet of the individuals found in the Seine settlement. Out of this context, the isotopic signature and thus contribution of the available aquatic foods was difficult to assess. Another potential source of dietary protein is wild boar. Depending on the local context, collagen δ34S values may contribute to better assessment of the relative contribution of freshwater and terrestrial resources.  相似文献   
25.
The animal remains found at the fourteenth–fifteenth century Hof van Leugenhaeghe are crucial to reconstruct the life of the noble inhabitants, as all buildings were destroyed with the construction of a later estate on the property called the Blauwhof. The diet confirms the high social status of this nobility with the suspected consumption of pig skulls, a possible sign of wealth in late-medieval Flanders. Other signs of a noble diet are found as well: juvenile cattle, a diverse spectrum of game, partridge and grey heron. The observed pattern of a wealthy diet is consistent with the zooarchaeological assemblages found at other noble sites in late-medieval Flanders.  相似文献   
26.
In Chinese traditional timber buildings, stitching is very common. When the bearing capacity or the rigidity is inadequate, a timber beam is often strengthened with another beam using the stitching method. The timber stitching beams are mainly of two types—the small-top/big-bottom type and the big-top/small-bottom type. To study the bending behavior of these two types of timber stitching beams, including the failure mode, the flexural capacity, the strain distribution at mid-span section, and the maximum deflection, bending tests are carried out on 14 timber stitching beams with Chinese traditional conformation for seven pine beams and seven fir beams. The results show that the failure modes of the small-top/big-bottom type of stitching beams all show brittle fractures at the bottoms of the bottom beams. The failure modes of the big-top/small-bottom type of stitching beams all show brittle fractures at the bottoms of the top beams. The distribution of section strain along the height of each part of the beam basically obeys plane hypothesis. Based on the theoretical and experimental analysis, the calculation formulas of flexural capacity and maximum deflection of these two types of timber stitching beams made of pine and fir are presented.  相似文献   
27.
One of the most important dilemmas facing the British authorities when they occupied their zone of Germany at the end of the Second World War was what to do with German science. The contributions made by scientists and engineers to the Nazi war machine, in fields such as rocketry and submarines, meant that German science was both revered and feared, and was therefore closely linked to concerns about a post-war military resurgence in Germany. This article aims to chart the changing approaches which the British occupation officials adopted towards German science in this period. While the initial intention was to prevent Germany from ever waging war again, through demilitarisation, denazification and dismantling, the focus changed as British enmity shifted from a former adversary, Germany, to a former ally, the Soviet Union. Policy reflected this shift as technology transfer and the reconstruction of domestic German science won greater favour. This article aims to show that, in the face of growing hostility from the USSR and in the deeply suspicious climate of the early Cold War, Britain was forced to abandon its moral mission towards German science and adopt a far more pragmatic strategy instead.  相似文献   
28.
This paper argues that portable X‐ray fluorescence spectrometry (pXRF) is a suitable elemental measurement technique to study the production of copper‐alloy artefacts. However, rather than try to imitate the accuracy and precision of laboratory techniques, it is more beneficial to deploy it in a survey role, one that attempts to model chronological and geographical changes within large quantities of artefacts. To achieve this, it was investigated to what extent corrosion and the issues surrounding surface measurements affect the potential of this type of research. Analyses on early Roman period brooches gathered in the Nijmegen region of the Netherlands were subsequently compared with published data.  相似文献   
29.
30.
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