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   166篇
  免费   8篇
  2024年   1篇
  2023年   3篇
  2022年   5篇
  2021年   3篇
  2020年   6篇
  2019年   7篇
  2018年   11篇
  2017年   11篇
  2016年   6篇
  2015年   9篇
  2014年   8篇
  2013年   35篇
  2012年   12篇
  2011年   8篇
  2010年   11篇
  2009年   6篇
  2008年   4篇
  2007年   8篇
  2006年   7篇
  2005年   2篇
  2004年   1篇
  2003年   2篇
  2002年   1篇
  2001年   1篇
  2000年   1篇
  1999年   1篇
  1998年   1篇
  1993年   1篇
  1992年   1篇
  1984年   1篇
排序方式: 共有174条查询结果,搜索用时 15 毫秒
61.
SUMMARY: In 1842 the former first government house located at Okiato, New Zealand, burnt to the ground and the site was abandoned. A well on the site was excavated in 1994–95, revealing a base layer of burnt timbers, a Maori digging stick and ceramic sherds with an estimated manufacture date range of 1823–41. We argue that this deposit is derived from the 1842 destruction of the Okiato government house building. An analysis of the wood identified kauri (Agathis australis) and kahikatea (Dacrycarpus dacrydioides), confirming that the building was not a prefabricated imported structure, but rather was constructed on site from locally available timber.  相似文献   
62.
63.
The possibility of determining the human or animal origin of bones from the lattice parameters of their inorganic bioapatite phase, when subjected to a high temperature treatment using the powder X-ray diffraction (XRD) technique, has been explored on a wide number of specimens. Forty-two animal bones were treated in a furnace at 1100 °C for 36 min and compared to 53 cremated human bones from a range of ancient necropolises. The X-ray diffraction patterns of bioapatite were simulated using both monoclinic P21/b and hexagonal P63/m structures to verify any occurrence of phase transformation and any difference in the lattice parameters due to the model. It was determined that the differences between the a-axis and c-axis of the monoclinic and hexagonal lattice were unimportant. Some outlying values were revealed to be caused by the presence of chlorine ions diffused into the apatite structure increasing its average unit cell values. Nevertheless, our results clearly show that in terms of lattice parameters the variability of human specimens are completely overlapped by the non-human variability making the use of XRD in order to distinguish animal from human bones questionable.  相似文献   
64.
汤艳坤  杨坤  石静苑 《神州》2012,(24):236-237
本文针对部队院校学员的实际情况,提出了一种利用仿真软件的优势,调动学员学习兴趣,促使部队学员电工电子知识系统的融合。使掌握的知识由理论向实际转变,从而满足当前对军人高素质的需求。  相似文献   
65.
圆觉洞石刻区10号龛是安岳石窟最精美的龛窟之一。本文介绍了三维扫描技术在圆觉洞10号龛的应用流程,主要包括三维数据采集,纹理信息采集。通过数据处理加工,获得照片般逼真纹理的仿真三维石窟模型。该模型可以用于圆觉洞10号龛保护性窟檐的设计等工作。  相似文献   
66.
As in traditional societies today ancient societies probably selected different fuels to meet specific heat requirements. Char and ash, the end products of fire, are often found in abundance in archaeological contexts. These end products can provide information regarding (i) the original fuel resource and type, (ii) the characteristics of the fire and (iii) combined with other archaeological evidence shed further light on possible socio-economic activity(-ies) associated with that fire. The three main fuel resources would have been (i) modern vegetation, (ii) fossil fuel and (iii) animal by-products. Local availability and abundance would have influenced the choice made.In this study an experimental approach was adopted to try and distinguish between the three different fuel resources that are known to have been used by ancient societies (and continue to be used by traditional societies today) from their char and ash remains to help determine original fuel-type and understand the relative heating properties. For this end one fuel-type from each fuel resource listed above, namely wood, peat and cow dung, was chosen.  相似文献   
67.
A road-network reliability analysis for a scenario seismic event is performed for a region of southern Italy characterised by a large number of small to medium municipalities quite close to each other and served by a dense network of roads. Among the many functions of the road network, whose links may fail after an earthquake due to the collapse of the bridges within them, the one selected for the present study is that of allowing rescue operations to be carried out at the sites of collapsed schools. For this to be possible, connection must be maintained between schools that survived, rescue centres and hospitals. Required elements for the study are the fragility curves of the bridges, the schools, the hospitals and the rescue centres. Output of the study is the expected value of the fraction of the total population in the area that is in need of assistance and cannot be hospitalised due to either failure of the network or other vulnerable components.  相似文献   
68.
西汉时期平板范竖式浇注铸钱工艺中有不同的钱币型腔设置和内浇道的形状,本研究通过计算机的流动模拟和凝固模拟技术,研究了钱币型腔和内浇道对充型过程的影响。结果表明:1)钱币型腔的不同设置对充型时间影响不大。2)钱币型腔的不同设置对充型过程产生影响,内郭正置的型腔产生气孔等铸造缺陷的可能性增大。3)内浇道的形状对钱币型腔的液流充型时间和液流在型腔中的流动过程有明显的影响,对凝固特征虽略有影响,但远小于钱币本身几何特征对凝固特征的影响。西汉中期起至晚期已基本采用内郭斜置的型腔设置,表明古代工匠在西汉中期始已明了钱币型腔的设置对充型过程将产生影响,已能通过选择更好的钱币型腔的设置来提高钱币的铸造质量。铸钱时,对缩短充型时间的要求高于对充型状态的要求,西汉中期以后多采用缩短充型时间的内浇道形状以提高平板范竖式浇铸工艺的充满率,从而提高成品率。  相似文献   
69.
Abstract

Within the EU-Project BACPOLES (EVK4-CT-2001-00043) bacterial wood degradation could be simulated in laboratory experiments to investigate the living conditions of the up to now unknown bacteria consortia, named erosion bacteria (EB), which cause considerable decay on waterlogged archaeological wood. In these Microcosm (MC) experiments the role of oxygen and chemical composition of the sediment were investigated. Therefore, the microcosms were subjected to different gassing treatments and the free dissolved oxygen was measured in different depths of the microcosms by special oxygen sensors (optodes). In further experiments the chemical composition of the sediment was verified to investigate the influence of different nutrient concentrations to the degradation process by EB.

From the findings it can be concluded that bacterial wood decay can proceed without free oxygen present but that it is more intense if oxygen is available. A water flow like streams in the sea, simulated by vertical water circulation, seems to stimulate the degradation activity and the degradation of wood by EB seems to be a result of low nutrient levels in the surrounding area.  相似文献   
70.
京津冀区域制造业分工与转移   总被引:1,自引:0,他引:1  
本文基于2001年至2009年京津冀区域182个区县制造业29个行业的数据,测算了京津冀区域制造业分工与转移的基本特征,并利用面板计量模型,对两者的关系进行了实证检验。研究得出:(1)京津冀区域制造业的发展呈现明显的差异化特征,三地制造业梯度分工格局正在逐步形成;(2)京津冀区域制造业在区域内部的转移主要从京津走廊向河北东部沿海的唐山、秦皇岛以及河北腹地的冀中南地区转移;(3)京津冀区域制造业的转移主要受到扩散效应的影响,在区县之间由分工的高梯度地区向低梯度地区转移。从分行业来看,技术密集型制造业转移受分工影响程度最大,其次是资本密集型制造业,劳动密集型制造业转移受分工影响最小。  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