全文获取类型
收费全文 | 11537篇 |
免费 | 440篇 |
出版年
2020年 | 153篇 |
2019年 | 198篇 |
2018年 | 247篇 |
2017年 | 293篇 |
2016年 | 333篇 |
2015年 | 236篇 |
2014年 | 209篇 |
2013年 | 3319篇 |
2012年 | 282篇 |
2011年 | 303篇 |
2010年 | 350篇 |
2009年 | 319篇 |
2008年 | 301篇 |
2007年 | 287篇 |
2006年 | 270篇 |
2005年 | 164篇 |
2004年 | 142篇 |
2003年 | 151篇 |
2002年 | 153篇 |
2001年 | 162篇 |
2000年 | 144篇 |
1999年 | 169篇 |
1998年 | 118篇 |
1997年 | 104篇 |
1996年 | 122篇 |
1995年 | 118篇 |
1994年 | 116篇 |
1993年 | 127篇 |
1992年 | 118篇 |
1991年 | 88篇 |
1990年 | 75篇 |
1989年 | 112篇 |
1988年 | 93篇 |
1987年 | 110篇 |
1986年 | 108篇 |
1985年 | 140篇 |
1984年 | 152篇 |
1983年 | 162篇 |
1982年 | 128篇 |
1981年 | 139篇 |
1980年 | 136篇 |
1979年 | 132篇 |
1978年 | 137篇 |
1977年 | 112篇 |
1976年 | 135篇 |
1975年 | 130篇 |
1974年 | 95篇 |
1973年 | 89篇 |
1972年 | 86篇 |
1970年 | 69篇 |
排序方式: 共有10000条查询结果,搜索用时 44 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.
5.
Y. Zhang L. Wei Z. Cui T. Zhang Y. Lei A. Gu Y. Chen L. Y. Zhang Z. X. Du 《Archaeometry》2020,62(3):660-676
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
6.
Albert A. Dahlberg 《Journal of archaeological science》1983,10(6):552-553
7.
8.
9.
10.