全文获取类型
收费全文 | 175717篇 |
免费 | 16430篇 |
国内免费 | 9502篇 |
专业分类
电工技术 | 13871篇 |
技术理论 | 8篇 |
综合类 | 17997篇 |
化学工业 | 17351篇 |
金属工艺 | 7172篇 |
机械仪表 | 15813篇 |
建筑科学 | 20350篇 |
矿业工程 | 6751篇 |
能源动力 | 7803篇 |
轻工业 | 13451篇 |
水利工程 | 7513篇 |
石油天然气 | 8323篇 |
武器工业 | 2008篇 |
无线电 | 10106篇 |
一般工业技术 | 17166篇 |
冶金工业 | 7036篇 |
原子能技术 | 2518篇 |
自动化技术 | 26412篇 |
出版年
2024年 | 726篇 |
2023年 | 2162篇 |
2022年 | 4394篇 |
2021年 | 5157篇 |
2020年 | 5421篇 |
2019年 | 4542篇 |
2018年 | 4456篇 |
2017年 | 5458篇 |
2016年 | 6587篇 |
2015年 | 6913篇 |
2014年 | 11286篇 |
2013年 | 11320篇 |
2012年 | 13059篇 |
2011年 | 14409篇 |
2010年 | 10315篇 |
2009年 | 10529篇 |
2008年 | 9865篇 |
2007年 | 11826篇 |
2006年 | 10260篇 |
2005年 | 8621篇 |
2004年 | 7297篇 |
2003年 | 6212篇 |
2002年 | 5033篇 |
2001年 | 4125篇 |
2000年 | 3536篇 |
1999年 | 2951篇 |
1998年 | 2535篇 |
1997年 | 2132篇 |
1996年 | 1757篇 |
1995年 | 1450篇 |
1994年 | 1301篇 |
1993年 | 972篇 |
1992年 | 895篇 |
1991年 | 658篇 |
1990年 | 554篇 |
1989年 | 471篇 |
1988年 | 400篇 |
1987年 | 271篇 |
1986年 | 238篇 |
1985年 | 214篇 |
1984年 | 256篇 |
1983年 | 241篇 |
1982年 | 196篇 |
1981年 | 96篇 |
1980年 | 95篇 |
1979年 | 67篇 |
1978年 | 53篇 |
1977年 | 46篇 |
1976年 | 43篇 |
1959年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
This paper considers the principles of algorithmic and software implementation of the software system NADRA 3D designed to
analyze processes in three-dimensional multicomponent soil media. The principles of operation of NADRA 3D are described.
__________
Translated from Kibernetika i Sistemnyi Analiz, No. 6, pp. 157–174, November–December 2006. 相似文献
32.
33.
34.
Computing surfaces invariant under subdivision 总被引:3,自引:0,他引:3
In this paper, we propose a general subdivision algorithm for generating surfaces. The algorithm has as motivation our earlier work on the design of free form curves where similar ideas were investigated. Here we describe some properties of uniform refinement algorithms for surface generation. A detail analysis of their properties will be given later by one of us. 相似文献
35.
The failure of the conductor of the 460 kV overhead transmission line located along the crossing of the Paraná River was investigated. As a result of this failure, a blackout took place in the southern states of Brazil in January of 2002, reaching approximately 67 million inhabitants. Investigation of the external aluminium layer of the ACSR conductor near the fracture showed typical static deformation marks and dynamic fretting wear tangential marks, both associated with the presence of Al2O3 debris. Additionally, encrusted silicon particles were observed on the external surface of the strands. The internal Al layer showed elliptical deformation marks also associated with Al2O3 debris. Both Al2O3 and Si particles are efficient abrasive material, which associated with slight relative motion of metallic surfaces (clamp/strand and strand/strand) can promote fretting wear. Two types of fracture surface of the Al strands were identified: 45° and quasi-normal surfaces, the former being the predominant type. Delamination and particle detachment were the mechanisms of superficial degradation observed on the Al strands, indicating that the rupture of the strands occurred under a gross slip fretting regime induced by sub-conductor oscillation. Inspection of the internal surface of as-cast Al–10%Si spacer clamps revealed different stages of intense circumferential wear caused by the preferential cracking and particle detachment of the eutectic constituent of the as-cast microstructure. This intense wear reduces the clamping contact pressure, which allows higher displacement amplitude and leads to the critical fretting regime. Finally, a few suggestions are discussed to minimise the occurrence of future failures. 相似文献
36.
37.
标准物质在分析测试中的重要地位及发展前景 总被引:2,自引:0,他引:2
标准物质在分析测试领域中无论在定值,方法的研究,误差确定等方面都有着重要地位。标准物质的质量保证及正确使用也应引起我们重视。随着科学技术迅速发展标准物质有着广阔发展前景。 相似文献
38.
39.
40.