全文获取类型
收费全文 | 28111篇 |
免费 | 706篇 |
国内免费 | 34篇 |
专业分类
电工技术 | 361篇 |
综合类 | 14篇 |
化学工业 | 6013篇 |
金属工艺 | 558篇 |
机械仪表 | 501篇 |
建筑科学 | 1206篇 |
矿业工程 | 335篇 |
能源动力 | 678篇 |
轻工业 | 1801篇 |
水利工程 | 229篇 |
石油天然气 | 247篇 |
无线电 | 1844篇 |
一般工业技术 | 4284篇 |
冶金工业 | 6647篇 |
原子能技术 | 273篇 |
自动化技术 | 3860篇 |
出版年
2022年 | 249篇 |
2021年 | 418篇 |
2020年 | 275篇 |
2019年 | 356篇 |
2018年 | 433篇 |
2017年 | 385篇 |
2016年 | 495篇 |
2015年 | 399篇 |
2014年 | 633篇 |
2013年 | 1691篇 |
2012年 | 961篇 |
2011年 | 1253篇 |
2010年 | 973篇 |
2009年 | 994篇 |
2008年 | 1190篇 |
2007年 | 1091篇 |
2006年 | 1010篇 |
2005年 | 910篇 |
2004年 | 769篇 |
2003年 | 742篇 |
2002年 | 729篇 |
2001年 | 518篇 |
2000年 | 425篇 |
1999年 | 482篇 |
1998年 | 560篇 |
1997年 | 489篇 |
1996年 | 527篇 |
1995年 | 487篇 |
1994年 | 482篇 |
1993年 | 475篇 |
1992年 | 443篇 |
1991年 | 293篇 |
1990年 | 433篇 |
1989年 | 411篇 |
1988年 | 357篇 |
1987年 | 428篇 |
1986年 | 368篇 |
1985年 | 463篇 |
1984年 | 488篇 |
1983年 | 412篇 |
1982年 | 395篇 |
1981年 | 311篇 |
1980年 | 310篇 |
1979年 | 368篇 |
1978年 | 311篇 |
1977年 | 260篇 |
1976年 | 258篇 |
1975年 | 259篇 |
1974年 | 221篇 |
1973年 | 225篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Robert Greetham 《Landscape Research》1992,17(1):10-19
An account of the use of landscape as subject-matter as a basis for the exploration of personal concerns and the search for self by various 20th Century photographers. Particular reference is made to the landscape photography of Eugene Atget, Edward Weston and Bill Brandt. 相似文献
42.
H. E. N. Stone 《Journal of Materials Science》1992,27(6):1701-1703
Ten samarium-structure alloys have been oxidation tested in air to estimate the thermal oxidation parameter, T
p, and hence the ratio T
p/TSm, where T
Sm is the temperature of decomposition of the appropriate structure and the ratio is a measure of the strength and type of bonding. The ratio decreases with (a) increasing distance apart in the 4f series of the components, and (b) increasing average Group number. 相似文献
43.
44.
45.
46.
Ronald W. Rousseau James K. Ferrell Robert M. Kelly 《Chemical Engineering Communications》1985,34(1):27-35
Experience with the operation of a pilot-scale unit is used to outline potential difficulties in the operation of acid gas removal systems on gases produced from coal. The pilot plant has been used to condition gases produced from subbituminous coal, devolatilized char, peat and lignite. The solvent used in the acid gas removal system has been refrigerated methyl alcohol. Data from this study document accumulation of hydrocarbons, sulfur and nitrogen compounds, and mercury in the circulating solvent. 相似文献
47.
Robert M. Wirtshafter 《Energy Policy》1985,13(2):143-155
Utility conservation programmes are designed to benefit both participants and non-participants. This article outlines the issues involved in designing conservation programmes for utilities and determining the appropriate amount of incentives that can be provided to participants without harming non-participants. More importantly, the article discusses the issue of access to the programmes by utility customers. It concludes that it is the existing restrictions to participation, and not the level of compensation, that are of greatest concern to non-participants. A number of utility programmes designed to eliminate the problem of non-participation are reviewed. 相似文献
48.
In order to obtain a bonded wood product from the tree, wood must be subjected to a series of processes. These include, among others, vital processes like drying of the green wood and machining of the surfaces of the dried wood in preparation for bonding. However, when wood is machined with dull blades, thermal degradation of the wood frequently occurs. The effects of kiln drying and thermal degradation of wood on the performance of the adhesive joints subsequently formed from such wood were investigated. Tapered double cantilever beam (TDCB) test specimens obtained from hard maple and phenol–resorcinol–formaldehyde (PRF) adhesives were used in the investigations. The enhancement of fracture energy due to the reduction in the moisture content of wood, the improved performance of adhesive joints due to rejointing of wood surfaces before bonding, and the reduction of adhesive joint strength resulting from thermal degradation of wood are presented and discussed. 相似文献
49.
50.
A Stone 《Canadian Metallurgical Quarterly》1998,101(6):1738-1739