全文获取类型
收费全文 | 1224篇 |
免费 | 94篇 |
国内免费 | 106篇 |
专业分类
电工技术 | 255篇 |
综合类 | 61篇 |
化学工业 | 205篇 |
金属工艺 | 53篇 |
机械仪表 | 115篇 |
建筑科学 | 12篇 |
矿业工程 | 1篇 |
能源动力 | 4篇 |
轻工业 | 2篇 |
石油天然气 | 1篇 |
武器工业 | 6篇 |
无线电 | 341篇 |
一般工业技术 | 295篇 |
冶金工业 | 4篇 |
原子能技术 | 3篇 |
自动化技术 | 66篇 |
出版年
2024年 | 2篇 |
2023年 | 14篇 |
2022年 | 5篇 |
2021年 | 23篇 |
2020年 | 19篇 |
2019年 | 15篇 |
2018年 | 25篇 |
2017年 | 34篇 |
2016年 | 36篇 |
2015年 | 32篇 |
2014年 | 41篇 |
2013年 | 197篇 |
2012年 | 44篇 |
2011年 | 71篇 |
2010年 | 32篇 |
2009年 | 81篇 |
2008年 | 96篇 |
2007年 | 111篇 |
2006年 | 106篇 |
2005年 | 79篇 |
2004年 | 81篇 |
2003年 | 35篇 |
2002年 | 42篇 |
2001年 | 35篇 |
2000年 | 24篇 |
1999年 | 26篇 |
1998年 | 21篇 |
1997年 | 22篇 |
1996年 | 15篇 |
1995年 | 23篇 |
1994年 | 12篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1982年 | 1篇 |
1978年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有1424条查询结果,搜索用时 15 毫秒
91.
利用弹性力学模型,简要推导了低频下磁致伸缩—压电双层复合材料磁电电压系数的表达式,计算了镍铁氧体—锆钛酸铅(NiFe2O4—Pb(Zr,Ti)O3,NFO—PZT)层状复合材料的横向磁电耦合。采用溶胶—凝胶法制备NiFe2O4样品,将其与PZT胶合制成NFO—PZT和NFO—PZT—NFO层状复合材料,研究了其在低频下的横向磁电效应。在约31.8 kA·m-1的偏置磁场下,NFO—PZT—NFO的横向磁电耦合达到的峰值为761.8 mV.A-1,约是NFO—PZT的3倍多。三层的界面耦合参数明显高于双层。 相似文献
92.
Nanocrystalline (30 nm) lead zirconate-titanate (PZT) ceramics, with Zr/Ti ratio 60:40, was prepared by a chemical method starting from a mixed metal ion–tartarate (Zr4+, Ti4+)–EDTA (Pb2+) complex solution. After complete evaporation of the mixed complex solution, a fluffy dried mass, known as precursor material was obtained. Heat-treatments of the precursor material at 400°C/2 h resulting single phase PZT. The precursor and heat-treated powders were characterized by TG/DTA, XRD and TEM analysis. The result shows that the process provides a technically simple route for the preparation of nanocrystalline PZT powders at low preparation temperatures. 相似文献
93.
94.
Daisuke HirookaAuthor Vitae Koichi SuzumoriAuthor VitaeTakefumi KandaAuthor Vitae 《Sensors and actuators. A, Physical》2011,171(2):283-291
In this article, we report a new particle-excitation flow control valve. The purpose of this study is the development of a particle-excitation flow control valve that can precisely control pneumatic cylinders. We have reported this flow control valve principle. The valve, driven by a PZT vibrator, has a simple lightweight structure with large flow rate. We report the relationship between the orifice arrangement and flow rate characteristics of the valve. We have designed a new prototype for the purpose of high controllability. We have measured flow-rate characteristics and confirmed the conditions necessary for continuous adjustment of flow quantity. The control valve works successfully to realize a change in flow rate. 相似文献
95.
给出了一种新颖的微量车床刀架系统,该系统由PZT(piezolectrictransducer)驱动的X-Z二维微进给工作台和Y向的微调对刀装置组成。微量工作台的两个方向均采用三个弹性元件的非对称式新型结构,这种新结构使刀具安装面位于工作台的一个角落,方便了刀具的安装。Y向微调机构利用差分螺纹调节原理使粗精调集为一体,结构紧凑,调节方便。 相似文献
96.
97.
98.
K. Boumchedda A. Ayadi T. Aouaroun G. Fantozzi 《Journal of the European Ceramic Society》2010,30(1):101-105
Performances in ultrasonic active transducers of interconnected porous lead zirconate titanate (PZT) piezoelectric disks with a porosity ranging from 30 to 70%, and polarized along their axial axis, are investigated. The characterization method used is based on the measurement of the voltage, which appears between the two faces of the piezoelectric element when it is excited by a current impulse. The device used, allows the acquisition of axial and radial vibrations of the transducer, and from these data, electromechanical and acoustic parameters are deduced. One observes that interconnected porosity causes the disappearance of the radial vibrations, and for large porosities the disk vibrates exclusively according to the axial mode. kt is increased, the acoustic impedance is reduced, and the axial propagation velocity reaches 2500 m s−1 for 30% of porosity. These results show that interconnected porous PZT are suitable for making ultrasonic active transducer, such as biomedical imaging devices. 相似文献
99.
采用磁控溅射法制备La0.5Sr0.5CoO3(LSCO)薄膜、sol-gel法制备Pb(Zr0.4Ti0.6)O3(PZT)薄膜,在玻璃和Ti-Al/Si衬底上构架了LSCO/PZT/LSCO电容器,研究了衬底对LSCO/PZT/LSCO电容器结构和铁电性能的影响。研究发现:虽然生长在两种衬底上的PZT薄膜均为钙钛矿结构多晶薄膜,但是,生长在玻璃衬底上的LSCO/PZT/LSCO电容器具有更好的铁电性能。玻璃基LSCO/PZT/LSCO电容器的剩余极化强度(Pr)为28×10–6C/cm2,矫顽电压(Vc)为0.96V;而硅基LSCO/PZT/LSCO电容器的Pr为25×10–6C/cm2,Vc为1.05V。 相似文献
100.