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
71.
72.
73.
Seok Han KimSridhar Komarneni 《Ceramics International》2011,37(8):3211-3216
Various parameters such as gel composition, aging, organic additive, and heating method affected the preferred orientation of nearly cubic PZT particles that were prepared by hydrothermal methods using TiCl3 as a Ti3+ source, at relatively low temperatures of 100-140 °C. The newly found synthetic conditions could be used to develop specially orientated PZT particles, which may be useful in growing oriented films, for example, by electrophoretic deposition. 相似文献
74.
《应用陶瓷进展》2013,112(6):310-317
AbstractDouble doped lead zirconium titanate (PZT) was synthesised by solid state reaction method. Calcination and sintering was carried out at various heating rates in order to study the effect of heating rate on the extent of phase formation of double doped PZT. Furthermore, the effect of heating rate on dielectric and pyroelectric properties was also investigated. Rhombohedral perovskite phase was confirmed in the double doped PZT samples. Quantitative X-ray diffraction (XRD) analysis suggests that the extent of PZT formation decreases beyond 8°C min?1 heating rate. The crystallite and grain sizes calculated from Scherrer's equation and field emission scanning electron microscope (FE-SEM) photographs respectively show the decreasing behaviour with increasing heating rate. Dielectric and pyroelectric properties show the increasing behaviour up to 8°C min?1 and decreasing behaviour beyond this heating rate. 相似文献
75.
J. F. Scott 《组合铁电体》2013,141(1-3):1-12
Abstract A somewhat qualitative review of leakage currents J(V,t) in perovskite oxides is presented. It is stressed that space-charge-limited currents (SCLCs) are not alternatives to ionic conduction, Schottky emission, Poole-Frenkel, or Fowler-Nordheim tunneling, but can occur whenever currents due to any of those mechanisms reach a certain threshold and are no longer limited by the details of the metal electrode-ferroelectric interface. Standard metal-semiconductor band models that exclude surface states fail qualitatively to account for the experimental dependences of leakage currents and breakdown voltages on electrode work function; the correct model is metal-n-p-n-metal, with surface donor-state trapping. A discussion of conduction properties in these materials is presented from an ionic conductor viewpoint. 相似文献
76.
I.N. Andryushina L.A. ReznichenkoL.A. Shilkina K.P. AndryushinS.I. Dudkina 《Ceramics International》2013
Based on high temperature x-ray diffraction studies of the PZT system (PbTixZr1−xO3, 0.0≤x≤1.0) the complete x-T phase diagram of solid solutions is built, which exhibits peculiar properties due to the real structure of ceramics: 相似文献
77.
D. Nelis M. K. Van Bael H. Van Den Rul J. Mullens L. C. Van Poucke G. Vanhoyland 《组合铁电体》2013,141(1):205-213
SrBi 2 Nb 2 O 9 (SBN) thin films on a Pt/Ti/SiO 2 /Si substrate were prepared by aqueous chemical solution deposition. The precursor solution was synthesized by means of an 'aqueous solution-gel method', starting with stable, inexpensive and easily available inorganic salts which are dissolved in an aqueous solution of chelating or coordinating ligands (acetates and citrates). Afterwards the synthesized precursor was spin-coated. However, problems arose as a consequence of insufficient 'wetting' of the substrate surface by the aqueous solution (poor film-substrate adhesion). Instead of improving surface adhesion by the addition of a surface-wetting reagent, a new strategy was developed: prior to spin-coating the platinum surface characteristics were modified using a UV/ozone technique. In this way the precursor solution was not chemically changed. Wetting/wettability was verified by means of contact angle measurements. A uniform, three-layer thin film with a total thickness of about 200 nm was obtained after thermal treatment, as could be verified using SEM and XRD. 相似文献
78.
S. B. Majumder P. S. Dobal B. Roy S. Bhaskar R. S. Katiyar Amar Bhalla 《Ferroelectrics Letters Section》2001,28(3):85-92
We have studied the effect of rare earth dopants (Nd, Gd and Ce) on the phase formation behavior and electrical properties of sol-gel derived Pb1.05(Zr0.53Ti0.47)O3 thin films. In all these films the perovskite phase is obtained up to 5 at% doping and beyond that pyrochlore phase was found to coexist with the perovskite phase. Ce and Gd doping(1-2 at%) exhibited improved ferroelectric and dielectric properties as compared to the undoped PZT films. Nd doping (2 at%) was found to be effective to increase the retained switchable polarization of undoped PZT from 63% to 84%. The transition temperature of undoped PZT film was found to be reduced with Nd doping. The Nd doped films also exhibited typical relaxor behavior and a diffuse phase transition, characteristic of the relaxor material. Introduction of Nd into the PZT lattice probably introduces disorder in the B site of ABO3 lattice which causes the observed relaxor behavior 相似文献
79.
ABSTRACT A microelectromechanical systems-based handwriting system device was designed. We proposed an ominidirectional acoustical sensor microarray which can offer isotropic directional sensitivity with a high radiation acoustic power when it as a transmitter and a high array spatial gain (AG) when it as a receiver. It has been designed for use in the novel handwriting recognition system to attain a large writeable scale and to write in any direction. The proposed array device based on novel ferroelectric thin film has excellent performance, miniature size and high reliability, and could be fabricated with conventional integrated circuit process. 相似文献
80.
传统上厚膜电容的制备由于采用了丝网技术、烧结工艺、有限的匹配温度特性材料,使得要实现高容量、低损耗、高频性就必须同时改变材料的成分、制备工艺和技术, 这是无法同时达到的.而采用激光微细熔覆快速原型制造技术,不需要高温烧结和掩模的制备,在不改变电极膜特性的情况下直接制备了适应高容量、低损耗和高频应用的介质膜.同时,消除了原有技术通过多次印刷和增加厚度来减少针孔的弊端,以及高温烧结带来的电极材料和介质材料成分的扩散,利用CAD/CAM系统可灵活地制备所设计的图形和尺寸,实现了元件小型化、轻薄化的制造. 相似文献