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   3210篇
  免费   166篇
  2020年   34篇
  2019年   61篇
  2018年   101篇
  2017年   79篇
  2016年   135篇
  2015年   76篇
  2014年   78篇
  2013年   781篇
  2012年   89篇
  2011年   118篇
  2010年   89篇
  2009年   103篇
  2008年   73篇
  2007年   85篇
  2006年   84篇
  2005年   44篇
  2004年   44篇
  2003年   51篇
  2002年   36篇
  2001年   63篇
  2000年   50篇
  1999年   57篇
  1998年   49篇
  1997年   42篇
  1996年   39篇
  1995年   32篇
  1994年   20篇
  1993年   46篇
  1992年   33篇
  1991年   22篇
  1990年   32篇
  1989年   36篇
  1988年   27篇
  1987年   35篇
  1986年   29篇
  1985年   32篇
  1984年   25篇
  1983年   48篇
  1982年   36篇
  1981年   33篇
  1980年   33篇
  1979年   28篇
  1978年   34篇
  1977年   37篇
  1976年   32篇
  1975年   30篇
  1974年   27篇
  1973年   25篇
  1972年   29篇
  1971年   24篇
排序方式: 共有3376条查询结果,搜索用时 15 毫秒
181.
182.
This article evaluates the results of almost a decade of experience with regional R&D development and implementation for enhanced innovation in the county of Nordland, Norway. Following a 2002 national devolution initiative, the county of Nordland was the first among Norwegian counties to coin and implement a distinct R&D policy for business-related innovation and development. This was done by setting up a broad regional partnership, framing a regional strategy and by coordinating substantial budgetary resources to implement the strategy. The evaluation describes the results of this process as ambiguous. This article looks at the process from three perspectives. First, we look at the organizational side of how the policy formation and implementation processes have performed. Second, we evaluate the business community response to the policy initiative to see whether any signs of altered behaviour can be found. Third, we look at how the partnership dynamic can explain policy outcomes. Theoretically and policy-wise we then discuss how our findings contribute to new insights in the field of analysing and generating regional innovation policy.  相似文献   
183.
In the Late Bronze Age, the extractive metallurgy of copper in north‐eastern Italy achieved a peak of technological efficiency and mass production, as evidenced by the substantial number of metallurgical sites and the large volume of slags resulting from smelting activities. In order to define the technological features of the Late Bronze Age metallurgical process, more than 20 slags from the smelting site of Luserna (Trentino, Italy) were fully analysed by means of optical microscopy, X‐ray powder diffraction, X‐ray fluorescence spectrometry and scanning electron microscopy. Three different slag types were identified based on mineralogical and chemico‐physical parameters, each being interpreted as the product of distinct metallurgical steps. A Cu‐smelting model is proposed accordingly.  相似文献   
184.
185.
We present the results of a multi‐method archaeometric study concerning the architectural elements reused in Monte Sorbo church (Sarsina, central Italy) between the eighth and ninth centuries AD . The provenance study has focused on classical marbles and stones, which clearly do not originate from the local Apennine geological formations and are thought to come from extra‐regional sources. A large fraction of the tested marbles is from Asia Minor, coming from both the Proconnesian district on Marmara Island and, probably, the Hasançavuslar site near Ephesus (Greco scritto). Of the four remaining marbles investigated, one is from the Carrara district and three are from different Greek quarrying areas, such as Mount Pentelikon (Athens) and the Thasos and Paros islands. The data also highlight the reuse of decorated gravestones made of Pietra di Aurisina as architectonic elements. This limestone is a fossiliferous carbonate stone outcropping in the Trieste Karst region (north‐eastern Italy), which was exploited by both the Romans and the Byzantines. The assignment of all of the columns of the central nave to the same source area provides an argument in favour of their provenance from a single monument, which was probably located in Sarsina or Ravenna, with the ‘colourful taste’ that is typical of the late Antonine and Severian periods.  相似文献   
186.
In the Iberian Peninsula, the copper metallurgy from the Chalcolithic to the Middle Bronze Age (MBA) was mostly characterized by low arsenic contents. A collection of 53 MBA artefacts from southern Portugal was analysed by micro‐EDXRF, optical microscopy, SEM–EDS and Vickers to investigate the metal composition and manufacture. No technological distinction was found between artefacts from domestic and funerary contexts, which were radiocarbon‐dated to 2000–1500 cal bc . The arsenic contents of almost 100 MBA artefacts from this region, including the above‐mentioned set, have a Gaussian distribution with a high average (3.9 wt% As). Possible explanations are discussed for this distinctive metallurgy at the south‐western end of the Iberian Peninsula.  相似文献   
187.
The grounds of 51 post‐Byzantine icons (Eastern Orthodox panel paintings) were studied by means of analytical techniques. The artefacts cover the period from the mid‐15th to the mid‐19th century and originate mainly from western (Epirus and the Ionian Islands) and southern Greece (Crete). The findings are examined in the light of technical recipes from related areas and eras, while special insights are gained from the exploration of a gypsum processing recipe by Dionysius of Fourna. A spectrum of ground fabrication practices that is richer than that reported so far or can be deduced from surviving Greek recipes is documented; three instances of ‘grosso‐sottile’ type grounds and a case of ‘inverse grosso‐sottile’ ground are among the reported novel, for post‐Byzantine icons, findings. Moreover, a case of an early icon restoration intervention is documented.  相似文献   
188.
189.
190.
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