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111.
112.
Pb(Fe2/3W1/3)O3 (PFW) thin films were deposited on platinized silicon substrate by a chemical solution deposition technique. Room‐temperature X‐ray diffraction (XRD) revealed a pure cubic crystal structure of the investigated material. The microstructure indicated good homogeneity and density of the thin films. A Raman spectroscopic study was carried out on PFW to study the polar nano‐regions in the temperature range 85–300 K. The Raman spectra showed a change in the peak intensity and a shift towards the lower wavenumber side with temperature. The Raman spectra also revealed the transition from the relaxor to the paraelectric state of PFW. There was no evidence of a soft mode in the low‐temperature region, in contrast to the normal ferroelectric behavior. The polar nano‐regions tend to grow and join at low temperatures (∼85 K), which become smaller with increase in temperature. The presence of strong Raman spectra in the cubic phase of the material is due to the presence of distributed Fm3m(Z = 2) symmetry nano‐ordered regions in the Pm3m(Z = 1) cubic phase. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
113.
利用最小二乘法,对辐照改性后P(VDF-TrFE)薄膜试样的介电常数谱进行v-F关系模拟,得出该材料具有与自旋玻璃体系及弛豫铁电体类似的性质.同时研究了其冻结温度随加工和辐照条件变化的规律.研究结果表明,通过适当选择加工和辐照条件,可以满足不同应用对铁电共聚物的要求. 相似文献
114.
P.D. Moran A. Chen N. Tangtrakarn M. Lawrence S. Bakhru H. Bakhru 《Journal of Electronic Materials》2007,36(12):1724-1731
This work reports the impact of He ion implantation conditions on the depth-dependent refractive index profile n(z) defining optical waveguides in 95.5% Pb(Zn1/3Nb2/3)O3-4.5%PbTiO3 (4.5% PZN-PT). Two hypotheses are investigated. The first is that n(z) follows the same functional form as the energy deposited into the lattice for all implantation conditions. The second is
that the effective refractive indices for fully confined propagating modes can be accurately predicted by a simple step-function
analytical approximation. Experimentally observed prism-coupled reflectivity data are collected from 4.5% PZN-PT samples implanted
with 1.0 MeV He ions for doses varying from 7.5 × 1014 ions/cm2 to 1 × 1017 ions/cm2 and with 3.8 MeV He ions for doses varying from 1 × 1015 ions/cm2 to 5 × 1016 ions/cm2. For doses less than 5 × 1016 ions/cm2, the data are consistent with a functional form of n(z) following that of the energy deposited to the lattice. The confined modes are accurately described by a step-function approximation to n(z). These data and analyses result in the ability to design waveguides in PZN-PT through choosing implantation conditions that
deposit the appropriate energy profile. This is not the case for the highest implantation doses, potentially signaling a difference
in the type of structural modification that occurs. 相似文献
115.
应用显微拉曼技术对弛豫型铁电体0.67PbMg1/3Nb2/3O3-0.33PbTiO3(0.67PMN-0.33PT)的偏振拉曼光谱随温度变化的研究表明,在-196到600°C温度范围内0.67PMN-0.33PT存在两次相变:三方到四方(R-T)相变和四方到立方(T-C)相变。R-T相变的特征是106cm-1软模(-196°C时)随温度的升高而湮没到80cm-1"静态"模式中。依照群论分析,0.67PMN-0.33PT的80cm-1和106cm-1(-196℃时)两个模式分别为E(1TO)和A1(1TO)模。文章对三方相的对称结构(C3v点群)在背向散射配置下不同偏振方向的拉曼散射效率进行了计算。计算结果表明晶体中的A1(1TO)和E(1TO)模式能够通过使用不同的散射配置进行识别。理论计算和实验结果相比较得到了很好的吻合。 相似文献
116.
Composites of (1 ? x)Na0.5Bi0.5TiO3-(x)SrTiO3, where x = 0.05, 0.10, 0.15, 0.2, 0.3 and 0.9 are studied. Individual compounds are synthesized by sol gel, and composites are prepared by solid-state sintering process. Through the analysis of X-ray diffraction, lattice parameters are obtained and, from scanning electron microscope (SEM), micro-structure of the samples is observed. The depolarization temperature (Td) and the Curie temperature (Tc) are determined from dielectric studies. Relaxor behavior of the samples is interpreted using modified Curie Weiss law. Control of polarization in sodium bismuth titanate (NBT) is achieved using strontium titanate (SrTiO3-ST) and studied through polarization vs. electric field (PE) loops and piezoelectric measurements. The intra-granual and inter-granual effects on the electrical properties of the ceramics are studied from impedance analysis. 相似文献
117.
Influence of the crystallization on the molecular mobility and ionic DC conductivity behaviors of relaxor ferroelectric P(VDF‐TrFE‐CTFE) terpolymers 下载免费PDF全文
Qing Liu Xunqian Yin Claude Richard Jean‐Fabien Capsal 《Journal of Polymer Science.Polymer Physics》2016,54(16):1645-1657
The dynamics of semicrystalline poly(vinylidene fluoride‐trifluoroethylene‐chlorotrifluoroethylene) (P(VDF‐TrFE‐CTFE)) terpolymers were fully investigated as a function of temperature and frequency, by means of broadband dielectric spectroscopy. Four types of relaxation regimes were observed over the full dielectric spectroscopy, namely (second) relaxation in the sub‐glass state, (segmental dynamics) in the rubbery state, the Curie transition and space charge carrier motion at high temperatures. Constrained segmental dynamics were observed in the terpolymer containing the highest crystalline fraction for which a narrow relaxation time distribution was found. These results indicate a decreasing average size of the cooperative rearranging region over the crystalline fraction. A decrease of the strength index values also implied a more fragile behavior for terpolymers with a higher degree of crystallinity. An exceptional increase in dielectric strength was found as the crystallinity increased. This behavior could be explained by an enhanced interphase (constrained amorphous phase). The Curie transition showed an accelerating relaxation rate for a more fragile terpolymer. Moreover, a motion of the space charge carrier ions was observed in the higher temperature range. Finally, there was evidence that the segmental dynamics in the amorphous phase was responsible for the motion of the space charge carrier ions. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1645–1657 相似文献
118.
铅基复合钙钛矿型弛豫铁电单晶体PMNT的生长基元为多种[BO_6]配位八面体,晶体生长过程可视为多种八面体基元与Pb~(2 )的组装过程.这些生长基元向{111}面叠合时易采取法向生长机制,向{001}面叠合时易采取层状生长机制,由此决定了晶体生长速度的各向异性与晶体的形貌.Bridgman法生长的PMNT晶体在生长过程中由内向生长机制形成规则的负晶结构;在晶体生长过程中,在其自然表面上可形成正形与负形两种形貌;在高温退火过程中,由于PbO的分解,晶体表面上可形成类似“蚀象”的构型,这些可从[BO_6]八面体生长基元的组装或拆分方面获得解释. 相似文献
119.
The local structure of Ba(Ti0.70,Sn0.30)O3 (BSnT) was investigated using micro Raman spectroscopy from 80 to 500 K, which indicated three local phase sequences. The dielectric spectroscopy studies illustrated freezing of polar nano‐regions (PNR) below 95 K, merger of frequency dispersion at 220 K, and the origin of polar nano‐regions at 482 K. The temperature evolution of Raman spectra, basically integrated intensity, indicates non‐ergodic relaxor phase below 100 K, mature ergodic phase between 100 and 200 K, and the existence of ergodic polar clusters until 450 K, and above paraelectric phase. The observation of local phase sequences by Raman spectra are in agreement with dielectric spectroscopy anomalies. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
120.
Systematic Raman scattering experiments were performed on Pb(Mg1/3Nb2/3)O3 (PMN) single crystals to resolve the low‐wavenumber dynamics in the crystal. Careful checking of the angular dependence of the Raman spectra indicated that the intense peak around 45 cm−1, which always smears the low‐wavenumber spectra, stems from the F2g mode due to Mg:Nb = 1:1 chemically ordered Fm3 m region. A proper scattering configuration for eliminating the strong F2g mode allowed the observation of the lowest wavenumber soft mode dynamics in PMN. The results revealed the softening of the mode towards Tc with underdamped oscillation. The soft mode becomes overdamped in a wide temperature range above Tc, suggesting the development of cluster dynamics due to polar nanoregions. It recovers the underdamped oscillation and hardens in the high‐temperature region. Finally, the physical picture of the relaxor phenomenon in PMN is discussed in terms of lattice dynamics by comparison with the typical displacive‐type ferroelectric phase transition. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献