全文获取类型
| 收费全文 | 32604篇 |
| 免费 | 291篇 |
| 国内免费 | 59篇 |
专业分类
| 教育 | 24166篇 |
| 科学研究 | 2766篇 |
| 各国文化 | 281篇 |
| 体育 | 1850篇 |
| 综合类 | 47篇 |
| 文化理论 | 513篇 |
| 信息传播 | 3331篇 |
出版年
| 2021年 | 211篇 |
| 2020年 | 273篇 |
| 2019年 | 451篇 |
| 2018年 | 2717篇 |
| 2017年 | 2733篇 |
| 2016年 | 2167篇 |
| 2015年 | 541篇 |
| 2014年 | 656篇 |
| 2013年 | 4627篇 |
| 2012年 | 777篇 |
| 2011年 | 1301篇 |
| 2010年 | 1360篇 |
| 2009年 | 922篇 |
| 2008年 | 1178篇 |
| 2007年 | 1666篇 |
| 2006年 | 570篇 |
| 2005年 | 836篇 |
| 2004年 | 813篇 |
| 2003年 | 704篇 |
| 2002年 | 442篇 |
| 2001年 | 422篇 |
| 2000年 | 372篇 |
| 1999年 | 302篇 |
| 1998年 | 209篇 |
| 1997年 | 233篇 |
| 1996年 | 220篇 |
| 1995年 | 187篇 |
| 1994年 | 196篇 |
| 1993年 | 179篇 |
| 1992年 | 250篇 |
| 1991年 | 254篇 |
| 1990年 | 293篇 |
| 1989年 | 265篇 |
| 1988年 | 211篇 |
| 1987年 | 210篇 |
| 1986年 | 230篇 |
| 1985年 | 206篇 |
| 1984年 | 213篇 |
| 1983年 | 204篇 |
| 1982年 | 160篇 |
| 1981年 | 162篇 |
| 1980年 | 157篇 |
| 1979年 | 205篇 |
| 1978年 | 198篇 |
| 1977年 | 139篇 |
| 1976年 | 146篇 |
| 1975年 | 135篇 |
| 1974年 | 118篇 |
| 1973年 | 129篇 |
| 1971年 | 125篇 |
排序方式： 共有10000条查询结果，搜索用时 187 毫秒
81.
82.
83.
84.
85.
An investigation has been undertaken at St Andrew’s church, Walpole St Andrew, Norfolk, to establish the underlying causes of the observed stone decay to the upper parts of the six stone piers. The stone decay was first recorded in the early 1930s. The salt-contaminated masonry within the church has been shown to undergo severe salt decay during the summer, with little damage occurring over the winter months. The south aisle piers have been shown to decay 2.5 times faster than the north aisle piers. Although crystallization–hydration cycles have been identified, the rate of decay is at its greatest when the cycling is relatively infrequent. This was not the expected trend. Furthermore, it has been shown that during extended periods where the ambient relative humidity is less than 75%, the rate of decay reaches a maximum. It is the length of this ‘drying’ period that apparently has the greatest influence on the rate of decay and could explain the significant difference in the rate of decay between the south and north aisle piers. The results have serious implications for passive conservation, where it is often recommended to lower the ambient relative humidity to well below the equilibrium relative humidity of the salt contaminant, to avoid crystallization–hydration cycles. Since, at the time of building, the church was situated on the coast, it is possible that the sodium chloride contamination occurred during the building process (1440–1520), particularly since the area was prone to sea-flooding at this time. Alternatively, the salt could have been applied as a treatment during the general restoration of 1897. Whatever the source of the salt, it seems likely that the ambient environment was changed by the insertion of a sealed floor in 1897, which could account for the onset of the salt decay. 相似文献
86.
87.
88.
89.
90.
L Sentz 《Bulletin of the Medical Library Association》1985,73(3):278-282
Fielding H. Garrison's paper "The medical periodical and the scientific society" cited the Buffalo Medical Journal in the company of eminent periodicals published in Berlin, Boston, and Edinburgh. This article provides an overview of the Journal and places it in context of 19th-century medical journalism. The Journal is assessed in terms of original scientific contributions and as a source of social and local history. 相似文献