全文获取类型
收费全文 | 60216篇 |
免费 | 7230篇 |
国内免费 | 5203篇 |
专业分类
电工技术 | 5452篇 |
综合类 | 6569篇 |
化学工业 | 7171篇 |
金属工艺 | 4034篇 |
机械仪表 | 4306篇 |
建筑科学 | 4911篇 |
矿业工程 | 2606篇 |
能源动力 | 1672篇 |
轻工业 | 7096篇 |
水利工程 | 2072篇 |
石油天然气 | 2060篇 |
武器工业 | 952篇 |
无线电 | 6401篇 |
一般工业技术 | 4827篇 |
冶金工业 | 2179篇 |
原子能技术 | 1062篇 |
自动化技术 | 9279篇 |
出版年
2024年 | 380篇 |
2023年 | 990篇 |
2022年 | 2483篇 |
2021年 | 2997篇 |
2020年 | 2179篇 |
2019年 | 1500篇 |
2018年 | 1605篇 |
2017年 | 1844篇 |
2016年 | 1639篇 |
2015年 | 2653篇 |
2014年 | 3256篇 |
2013年 | 3854篇 |
2012年 | 5130篇 |
2011年 | 5081篇 |
2010年 | 4995篇 |
2009年 | 4826篇 |
2008年 | 5055篇 |
2007年 | 4751篇 |
2006年 | 4233篇 |
2005年 | 3567篇 |
2004年 | 2569篇 |
2003年 | 1643篇 |
2002年 | 1569篇 |
2001年 | 1483篇 |
2000年 | 1258篇 |
1999年 | 415篇 |
1998年 | 115篇 |
1997年 | 84篇 |
1996年 | 57篇 |
1995年 | 44篇 |
1994年 | 34篇 |
1993年 | 44篇 |
1992年 | 40篇 |
1991年 | 45篇 |
1990年 | 41篇 |
1989年 | 34篇 |
1988年 | 22篇 |
1987年 | 16篇 |
1986年 | 20篇 |
1985年 | 5篇 |
1984年 | 12篇 |
1983年 | 11篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 23篇 |
1979年 | 16篇 |
1966年 | 1篇 |
1964年 | 1篇 |
1959年 | 8篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Shear ductility and toughenability study of highly cross-linked epoxy/polyethersulphone 总被引:1,自引:0,他引:1
The objective of the present study was to determine whether the ductility and toughenability of a highly cross-linked epoxy
resin, which has a high glass transition temperature, T
g, can be enhanced by the incorporation of a ductile thermoplastic resin. Diglycidyl ether of bisphenol-A (DGEBA) cured by
diamino diphenyl sulphone (DDS) was used as the base resin. Polyethersulphone (PES) was used as the thermoplastic modifier.
Fracture toughness and shear ductility tests were performed to characterize the materials. The fracture toughness of the DDS-cured
epoxy was not enhanced by simply adding PES. However, in the presence of rubber particles as a third component, the toughness
of the PES–rubber-modified epoxy was found to improve with increasing PES content. The toughening mechanisms were determined
to be rubber cavitation, followed by plastic deformation of the matrix resin. It was also determined, through uniaxial compression
tests, that the shear ductility of the DDS-cured epoxy was enhanced by the incorporation of PES. These results imply that
the intrinsic ductility, which had been enhanced by the PES addition, was only activated under the stress state change due
to the cavitation of the rubber particles. The availability of increasing matrix ductility seems to be responsible for the
increase in toughness.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
32.
TRT入口方管道爆裂原因剖析 总被引:1,自引:0,他引:1
介绍了鞍钢7#高炉TRT装置入口方管道爆裂事故经过,进行了原因分析,并提出了解决措施。 相似文献
33.
大空域机动巡航导弹的模糊PID控制器设计 总被引:1,自引:1,他引:0
针对大空域机动巡航导弹下降转平飞过程中出现的强非线性特点.在俯仰通道设计了模糊PID双模控制方案。以高度误差和该误差变化量为输入.以高度误差为阀限.在高度误差较大时采用响应迅速的模糊控制器.较小时采用稳态精度较高的PID控制器。最后通过仿真表明通过该方案所控制的弹道符合方案弹道.满足设计指标要求。 相似文献
34.
35.
The article is to introduce author's research results in recent years in the field of leadership behavior. The main researches conducted in this field include competency model of senior executives in communication industry and family firms; transformational leadership and its relationship with leadership effectiveness, the impact of supervisor's feedback on employees' behavior and the cross-culture study of supervisor's feedback. Theoretical and practical contributions of these researches are explained. Directions for future research are discussed. 相似文献
36.
37.
The charge storage characteristics of P-channel Ge/Si hetero-nanocrystal based MOSFET memory has been investigated and a logical array has been constructed using this memory cell. In the case of the thickness of tunneling oxide T_ox=2nm and the dimensions of Si- and Ge-nanocrystal D_Si=D_Ge=5nm, the retention time of this device can reach ten years(~1×10~8s) while the programming and erasing time achieve the orders of microsecond and millisecond at the control gate voltage |V_g|=3V with respect to N-wells, respectively. Therefore, this novel device, as an excellent nonvolatile memory operating at room temperature, is desired to obtain application in future VLSI. 相似文献
38.
39.
40.
对T形线路的故障测距,现有方法都是先判断故障支路,再将3端线路等效成2端线路进行测距。但在 T节点附近短路,尤其是经高阻短路时,现有的测距方法由于无法正确判别故障支路而存在一定范围的测距死区。针对上述缺陷,分别假设故障发生在某一支路,由假定正常的2段支路端的电压、电流推算求得 T节点电压和注入假定故障支路的电流,从而分别求得3个故障距离。经证明,求得的3个故障距离有且仅有1个在0和对应支路总长度之间,该距离就是真实的故障距离,故障发生在对应支路上。该方法无需事先判别故障支路即可测距,在 T节点附近经高阻故障时无测距死区。其测距精度理论上不受过渡电阻和故障类型影响,无需故障前数据,且对滤波无高要求。EMTP仿真结果表明该方法正确、有效,测距精度高。 相似文献