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   5654篇
  免费   260篇
  2020年   86篇
  2019年   129篇
  2018年   169篇
  2017年   205篇
  2016年   187篇
  2015年   137篇
  2014年   144篇
  2013年   1800篇
  2012年   127篇
  2011年   145篇
  2010年   153篇
  2009年   137篇
  2008年   120篇
  2007年   105篇
  2006年   90篇
  2005年   70篇
  2004年   75篇
  2003年   79篇
  2002年   81篇
  2001年   76篇
  2000年   91篇
  1999年   72篇
  1998年   61篇
  1997年   71篇
  1996年   50篇
  1995年   56篇
  1994年   44篇
  1993年   42篇
  1992年   45篇
  1991年   54篇
  1990年   38篇
  1989年   43篇
  1988年   47篇
  1987年   45篇
  1986年   46篇
  1985年   72篇
  1984年   54篇
  1983年   71篇
  1982年   52篇
  1981年   63篇
  1980年   55篇
  1979年   61篇
  1978年   61篇
  1977年   45篇
  1976年   53篇
  1975年   38篇
  1974年   39篇
  1973年   35篇
  1972年   28篇
  1969年   27篇
排序方式: 共有5914条查询结果,搜索用时 15 毫秒
91.
92.
93.
94.
The chemical and mineralogical characterization of seven ceramic fragments produced within Tiwanaku state (c.500–1000 ce ) is reported. The instrumental techniques used included X‐ray elemental and mineralogical chemical analysis, Raman spectroscopy, and scanning and light microscopy. The results indicate there are several clay types, although they show similarities, such as the use of a plant‐based temper. The red colour of the decoration is hematite, and manganese oxides such as jacobsite are present in the black. The white colour is a mixture of gypsum and clay, and the orange is a mixture of hematite and clay. The use of colours, the quality of the clays and the temperatures reached during pottery firing point to expertise in ceramic production and to complex decision‐making processes. The multi‐elemental archaeometric approach documented here could become an important tool to shed a light on ancient ceramic technology and the internal variance of Tiwanaku pottery.  相似文献   
95.
In 2022, an Athenian red-figured cup attributed to Makron was returned to Italy by New York’s Metropolitan Museum of Art. The cup had been acquired in fragments, through purchase and gift, from multiple sources over several years, starting with two fragments from the restorer Fritz Bürki in 1978. A second cup, also attributed to Makron, was acquired in a parallel way. The sources for the fragments from both cups point to galleries collectors and donors – Summa Galleries, Frieda Tchachos, Elizabeth Hecht, and Dietrich von Bothmer – who have been associated with other material that has been repatriated to Italy in recent years. It is suggested that some of the incised ‘signatures’ by Hieron that are found on cups attributed to Makron may have been applied since antiquity.  相似文献   
96.
97.
98.
99.
A multidisciplinary programme of research on Islamic pottery has been focused on questions of the dating, provenance and technology of Islamic pottery. One particular question has been the development of stonepaste, a material made primarily of crushed quartz with added frit-glass and clay. The combination of the different approaches of this study has revealed early foundations for the technology in ninth-century AD Iraq, apparently originating in the clay ceramic rather than the ‘Egyptian faience’ tradition. Subsequent and final practice developed in tenth- and eleventh-century AD Egypt. This technology becomes the primary body for all fine Islamic ceramics.  相似文献   
100.
As technologies grow in complexity, firms often target their internal R&D resources on core competencies and utilize outside sources for supporting knowledge and technology. Where do firms turn to find such resources? This paper reports the perceptions of technology transfer managers in United States manufacturing firms toward federal and university labs and identifies the types of farms that are better positioned to utilize externally available technological resources. Based on replies from research-intensive companies within the United States, the authors find that larger firms with high research and development (R&D) budgets tend to ascribe greater significance to external sources than do smaller ones. Also, companies spending over $500 million in R&D rank universities the most significant external source of knowledge, followed by V S.-based firms, and then foreign firms.  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