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   10934篇
  免费   402篇
  2020年   133篇
  2019年   210篇
  2018年   244篇
  2017年   277篇
  2016年   326篇
  2015年   236篇
  2014年   222篇
  2013年   3246篇
  2012年   306篇
  2011年   312篇
  2010年   356篇
  2009年   321篇
  2008年   262篇
  2007年   284篇
  2006年   262篇
  2005年   151篇
  2004年   137篇
  2003年   134篇
  2002年   150篇
  2001年   168篇
  2000年   124篇
  1999年   152篇
  1998年   119篇
  1997年   101篇
  1996年   116篇
  1995年   113篇
  1994年   113篇
  1993年   114篇
  1992年   103篇
  1991年   83篇
  1990年   69篇
  1989年   100篇
  1988年   90篇
  1987年   106篇
  1986年   97篇
  1985年   113篇
  1984年   109篇
  1983年   133篇
  1982年   97篇
  1981年   111篇
  1980年   112篇
  1979年   108篇
  1978年   93篇
  1977年   106篇
  1976年   98篇
  1975年   102篇
  1974年   74篇
  1973年   69篇
  1972年   78篇
  1970年   64篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Evidence from several disciplines supports the proposition that following the Wisconsinan and an initial but brief moist phase of the Holocene, there was a gradual drying trend in the mid-continent Prairie Peninsula that peaked about 7000 years ago, a pattern that was not reversed until about 4000 years ago. Except for minor perturbations, conditions during the past four millennia have essentially been similar to those of the present. Studies in palynology and geomorphology have shown that the climatic regimes of the early/mid Post-glacial had a marked influence on both the biota and landscape erosional patterns, especially along the margins of the Prairie Peninsula. Measurable changes in the landscape and attendant biota show a time-transgressive pattern of drought related phenomena recorded palaeo-ecologically from west to east.Few studies of archaeological sites in the Prairie Peninsula have examined the evidence in and around the sites themselves for data reflecting local environmental dynamics. In fact, earlier models proposed for explaining the evolution of food-procuring systems in eastern North America virtually ignored potential changes in the natural environment. This paper examines data from two archaeological sites along the prairie-forest border in Missouri that contain long cultural sequences. Evidence is presented that pronounced changes in the natural environment occurred and that these biophysical variables are indeed critical for understanding the evolution of food-procuring societies in the American Midwest.  相似文献   
3.
4.
Palace lanterns were important and highly visible decorations in the imperial palace in Beijing, China, during the Qing dynasty (1636–1912). Most lanterns had colourful tassels made of fibres. The study performed a comprehensive investigation of the materials and dyes used for palace lantern tassels preserved in The Palace Museum, Beijing. Eight samples with different colours, including yellow, green and red, from five palace lanterns were analysed. By using ultra-performance liquid chromatography combined with time-of-flight mass spectrometry, the compositions of the dyes were identified quickly, and thus the dyes' origins were explored. A X-ray fluorescence spectrometer assisted in the detection of whether a mordant was used during the dyeing process. As a result, the tassels were all made of silk, discovered through the use of microscopic observation and micro-Fourier transform infrared spectrometry analysis. Different dyeing techniques were found in these tassels: yellow tassels were dyed by cork tree or turmeric by a direct dyeing method; greens were dyed by pagoda bud with an iron mordant, or by the combination of cork tree and indigo using multi-dyeing method; and red tassels were coloured with different acid red industrial dyes. These results provide valuable data for the conservation of ancient textile tassels and contribute to the investigation of other hanging tags.  相似文献   
5.
6.
7.
8.
9.
10.
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