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   7813篇
  免费   342篇
  2020年   114篇
  2019年   148篇
  2018年   195篇
  2017年   256篇
  2016年   235篇
  2015年   183篇
  2014年   146篇
  2013年   2282篇
  2012年   159篇
  2011年   170篇
  2010年   213篇
  2009年   205篇
  2008年   195篇
  2007年   160篇
  2006年   147篇
  2005年   122篇
  2004年   109篇
  2003年   124篇
  2002年   121篇
  2001年   105篇
  2000年   116篇
  1999年   114篇
  1998年   100篇
  1997年   91篇
  1996年   77篇
  1995年   80篇
  1994年   79篇
  1993年   82篇
  1992年   81篇
  1991年   61篇
  1990年   52篇
  1989年   67篇
  1988年   69篇
  1987年   73篇
  1986年   68篇
  1985年   107篇
  1984年   120篇
  1983年   118篇
  1982年   92篇
  1981年   98篇
  1980年   95篇
  1979年   96篇
  1978年   89篇
  1977年   73篇
  1976年   96篇
  1975年   91篇
  1974年   66篇
  1973年   48篇
  1972年   41篇
  1970年   37篇
排序方式: 共有8155条查询结果,搜索用时 15 毫秒
991.
Scientists from the National Institute of Standards and Technology (NIST) worked in a collaborative partnership with archaeologists from the National Park Service's (NPS) Submerged Resources Center (SRC) to develop a finite element model (FEM) of the battleship USS Arizona. An FEM is a computer-based engineering model that calculates theoretical stresses, propagation of force, and shape changes to a structure under loads using thousands or even millions of individual elements whose individual responses are well understood. NIST researchers created an FEM of an 80 ft. (25 m) midships section of the Arizona site to analyze archaeological site formation processes on the sunken battleship, in particular to determine the current condition of the wreck and predict its future strength and structural integrity as it continues to corrode. The NIST's FEM study is one aspect of a larger project under the direction of the NPS, the USS Arizona Preservation Project, whose goal is to determine the nature and rate of corrosion affecting USS Arizona, and to model its long-term structural deterioration. The FEM incorporates findings from other key components of the USS Arizona Preservation Project, such as steel hull corrosion rates, structural surveys of the vessel, sediment compaction studies, and analysis of the concretion that covers the ship's hull, into a single tool that is being used to predict how the wreck will degrade in the future.  相似文献   
992.
The analysis and preservation of organic materials preserved within wetland environments represents one of the most costly parts of any post-excavation strategy. This paper outlines the application of high-resolution terrestrial laser scanning to one class of preserved material, worked archaeological wood. Scanning allowed the recording of the artefacts in three dimensions and the identification of features such as toolmarks. Features can be measured and volumetrically modelled within the digital environment, which may not always be possible for these often fragile materials using conventional techniques. Repeat scanning of the artefacts provided an opportunity to use comparative analysis software to investigate changes in the morphology of artefacts under contrasting conditions of short-term storage. The results suggest that immersion in water results in the least deterioration, whereas both freezing and air-drying caused distortion and degradation. This paper demonstrates that laser scanning provides a viable alternative post-excavation method for the recording, analysis and long-term ‘virtual archiving’ of organic archaeological materials, which may be more cost-effective in some instances than other methods of preservation.  相似文献   
993.
During the 19th century, the question of the relation between the soul and the body was deeply renewed by German psychological studies. The new elaborated conception of the relationship between the psychical and the physical coincides with the appearance of a cognitivist paradigm, in which mental phenomena are considered as entities that may be individualised, isolated, and then correlated with the activity of specific neural substrates. German psychologists were confronted with the problem of the correlation between psychical life and the nervous system (localisation of mental phenomena and nature of this correlative relationship), and propose an extensive analysis on the neural conditions and the emergence of psychical processes.  相似文献   
994.
995.
996.
997.
The subsistence strategies of the Lapita populations (3100–2800 BP), the first colonisers of the pristine environments of the islands of Eastern Melanesia and Western Polynesia, have been a matter of ongoing debate for decades. Opinions have ranged between the two extremes of Lapita colonisers being either characterised as highly mobile foragers to fully horticultural communities. To further address the question, this paper presents stable carbon and nitrogen isotopic data obtained from analyses of human and animal collagen samples from the site of Teouma (Efate, Vanuatu) dated to between c. 3000–2500 BP. The isotopic signatures obtained from 28 samples (23 human and 5 animal), interpreted in combination with isotopic information from several coastal and insular environments, suggest a diet primarily made up of terrestrially derived animal protein with lesser contributions from vegetable produce and inshore marine species. Comparisons linking the isotopic data gleaned from the Teouma individuals and Lapita subsistence patterns reconstructed through archaeozoological and archaeobotanical remains support the hypothesis of a mixed economy, that included terrestrial foraging, inshore marine exploitation and a low level of food production for at least some of the earliest Lapita colonists in Vanuatu.  相似文献   
998.
999.
1000.
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