全文获取类型
收费全文 | 375篇 |
免费 | 12篇 |
国内免费 | 22篇 |
专业分类
化学 | 114篇 |
晶体学 | 20篇 |
力学 | 26篇 |
数学 | 3篇 |
物理学 | 246篇 |
出版年
2023年 | 6篇 |
2022年 | 5篇 |
2021年 | 1篇 |
2020年 | 10篇 |
2019年 | 18篇 |
2018年 | 12篇 |
2017年 | 10篇 |
2016年 | 17篇 |
2015年 | 10篇 |
2014年 | 12篇 |
2013年 | 53篇 |
2012年 | 27篇 |
2011年 | 43篇 |
2010年 | 16篇 |
2009年 | 28篇 |
2008年 | 17篇 |
2007年 | 35篇 |
2006年 | 17篇 |
2005年 | 22篇 |
2004年 | 11篇 |
2003年 | 4篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 8篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1992年 | 7篇 |
1973年 | 1篇 |
排序方式: 共有409条查询结果,搜索用时 15 毫秒
1.
Christian Erich Zybill Mahmoud Abdel-Hafiez Sami Allam Tharwat El Sherbini 《Progress in Solid State Chemistry》2007,35(2-4):469-480
Ferroelectric thin films form an equilibrium domain structure compatible with their respective crystallographic symmetry. In tetragonal (111) PZT, 90° domains prevail; in (pseudo-tetragonal) (100) SBT both 90° and 180° domains are present. The size of 90° domains has been measured for e.g., PZT as slabs of 15 nm width. Domain size is a result of stress minimization in the film during the paraelectric (PE) → ferroelectric (FE) transition. A precise and regular domain pattern for (111) PZT and (100) SBT films has been investigated in detail by TMSFM. Single domains can be addressed mechanically with the tip of an AFM. Such single domain switching corresponds to a data storage density of 200 Gbit/inch2. Applications of ferroelectric and high- paraelectric materials for e.g., non-volatile data storage replacing DRAM devices or as sensors in infrared cameras are increasingly becoming popular. 相似文献
2.
Ch. Linga Raju K.V. Narasimhulu N.O. Gopal J.L. Rao B.C.V. Reddy 《Journal of Molecular Structure》2005,754(1-3):100-105
Electron paramagnetic resonance (EPR) studies have been carried out on VO2+ ions doped in single crystals of ferroelectric material, potassium thiourea bromide (PTB) at room temperature and in the temperature range 103–343 K on X-band MW frequency. An isotropic octet spectrum characteristic of VO2+ ion was obtained due to the fast re-orientation of the VO2+ in PTB lattice, which exhibits glassy nature at certain range around room temperature. The temperature dependant EPR spectra of VO2+ ions in this host lattice has been attributed to the occurrence of multiple phase transitions due to the combined environment effects of KBr and thiourea materials in the single crystal. From the optical absorption spectrum, the crystal field splitting parameter Dq, tetragonal parameters Ds and Dt have been evaluated and discussed. 相似文献
3.
The metal-ferroelectric-semiconductor (MFS) heterostructure has been fabricated using Bi3.25La0.75Ti3O12 (BLT) as a ferroelectric layer by sol-gel processing. The effect of annealing temperature on phase formation and electrical
characteristics of Ag/BLT/p-Si heterostructure were investigated. The BLT thin films annealed at from 500°C to 650°C are polycrystalline,
with no pyrochlore or other second phases. The C-V curves of Ag/BLT/p-Si heterostructure annealed at 600°C show a clockwise C-V ferroelectric hysteresis loops and obtain good electrical properties with low current density of below 2×10−8 A/cm2 within ±4 V, a memory window of over 0.7 V for a thickness of 400 nm BLT films. The memory window enlarges and the current
density reduces with the increase of annealing temperature, but a annealing temperature over 600°C is disadvantageous for
good electrical properties. 相似文献
4.
Lead zirconate titanate (PZT) thin films were deposited on Pt/Ti/SiO2/Si and interlayer/Pt/Ti/SiO2/Si substrate by radio frequency (r.f.) magnetron sputtering with a Pb1.1Zr0.53Ti0.47O3 target. The crystallization of the PZT thin films was formed only by substrate temperature. When interlayer (PbO/TiO2) was inserted between the PZT thin film and the Pt electrode, the grain growth and processing temperature of the PZT thin films were considerably improved. Compared to PZT/Pt structure, the dielectric constant and polarization properties of the PZT/interlayer/Pt structure were fairly improved. In particular, PZT/interlayer/Pt at the substrate temperature of 400 °C showed prevalent ferroelectric properties (r=475.97, tanδ=0.0591, Pr=23 μC/cm2). As a result of an X-ray photoelectron spectroscopy (XPS) depth-profile analysis, it was found that PZT/interlayer/Pt deposited only by substrate temperature without the post-annealing process via r.f. magnetron sputtering method remained independent of each other regardless of substrate temperatures. 相似文献
5.
A perovskite-type BaCu1/3Nb2/3O3 was prepared by high temperature reaction using BaCO3, CuO and Nb2O5. The X-ray powder diffraction pattern of this compound was indexed with the tetragonal cell with the lattice parameters of a=4.0464(4) and c=4.1807(4) Å (c/a=1.033). This compound had the tetragonal perovskite-type structure in which the B site was occupied statistically by Nb and Cu atoms. From high temperature X-ray powder diffraction patterns this compound had a phase transition from the tetragonal to cubic symmetry in the temperature range of 500-600 °C. The P-E and S-E hysteresis loops occurred at room temperature and the apparent maximum in the temperature dependence of the dielectric constant was observed at 520 °C. The temperature dependence of the inverse of magnetic susceptibility exhibited paramagnetic behavior. 相似文献
6.
Shuhui Yu Kui Yao Francis Eng Hock Tay 《Journal of Sol-Gel Science and Technology》2007,42(3):357-364
The preferential formation of a pyrochlore structure is a knotty problem in the preparation of Pb(Zn1/3Nb2/3)O3 (PZN)-based thin film materials and its presence is significantly detrimental to the dielectric and piezoelectric properties.
In this study, 40 mol% of PZN was replaced with Pb(Mg1/3Nb2/3)O3 (PMN) for obtaining a perovskite composition around a morphotropic phase boundary (MPB), (1−x)(0.6PZN-0.4PMN)-xPT ((1−x)PZMN-xPT, PT: PbTiO3) where x = 0.23. The thin films with this composition were prepared with a polyethylene glycol (PEG) modi-fied sol-gel method on LaAlO3 substrates. The microstructural evolution of the films on heat treatment was examined with X-ray diffraction. With the aid
of PEG, the formation of the pyrochlore phase was suppressed and the perovskite phase formed directly from the amorphous gel
film. The multilayer films with a thickness around 0.25 μm showed a single perovskite phase without any detectable pyrochlore
structure. Microscopic images showed uniform grain size of a few tens of nanometers. The role of the polymer dramatically
promoting the perovskite phase was investigated with the aid of X-ray photoelectron spectroscopy and thermal analysis. The
dielectric constant of the obtained film was 4160 at 1 kHz. The film demonstrated typical ferroelectric hysteresis loops and
exhibited excellent piezoelectric performance. 相似文献
7.
Pb(Zr0.25Ti0.75)O3 (PZT25) thin films were prepared on LaNiO3-coated thermally oxidized silicon substrates by chemical solution deposition method, where LaNiO3 electrodes were also prepared by a chemical solution deposition technique. The dielectric constant and dielectric loss of
the PZT25 thin films were 570 and 0.057, respectively. The remanent polarization and coercive field were 20.11 μC/cm2 and 60.7 kV/cm, respectively. The PZT25 thin films on LaNiO3-coated thermally oxidized silicon substrates showed improved fatigue characteristics compared with their counterparts on
plantium-coated silicon substrates. 相似文献
8.
9.
In the present work, zirconium modified bismuth titanate ceramics have been studied as potential lead-free ferroelectric materials over a broad temperature range (RT – 800 °C). Polycrystalline samples of Bi4Ti3−xZrxO12 (x=0.2, 0.4, 0.6) (BZrT) with high electrical resistivity were prepared using the solution combustion technique. The effect of Zr doping on the crystalline structure, ferroelectric properties and electrical conduction characteristics of BZrT ceramics were explored. Addition of zirconium to bismuth titanate enhances its dielectric constant and reduces the loss factor as it introduces orthorhombic distortion in bismuth titanate lattice which is exhibited by the growth along (0010) lattice plane. Activation energy due to relaxation is found to be greater than that due to conduction thus confirming that electrical conduction in these ceramics is not due to relaxation of dipoles. Remanent polarization of the doped samples increases as the Zirconium content increases. 相似文献
10.
The resistance switching behavior has recently attracted great attentions for its application as resistive random access memories (RRAMs) due to a variety of advantages such as simple structure, high-density, high-speed and low-power. As a leading storage media, the transition metal perovskite oxide owns the strong correlation of electrons and the stable crystal structure, which brings out multifunctionality such as ferroelectric, multiferroic, superconductor, and colossal magnetoresistance/electroresistance effect, etc. The existence of rich electronic phases, metal–insulator transition and the nonstoichiometric oxygen in perovskite oxide provides good platforms to insight into the resistive switching mechanisms. 相似文献