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991.
R. Padhee 《Phase Transitions》2013,86(9):865-880
This paper highlights the electrical properties of two new complex tungsten bronze ceramics (K2Pb2Eu2W2Ti4Nb4O30 and K2Pb2Pr2W2Ti4Nb4O30) which were prepared by high temperature mixed oxide method. Variation of impedance parameters with temperature (27–500 °C) and frequency (1 kHz to 5 MHz) shows the grain and grain boundary effects in the samples. The variation of dielectric parameters with frequency is also studied. The ac conductivity variation with temperature clearly exhibits that the materials have thermally activated transport properties of Arrhenius type. 相似文献
992.
Samples of Bi4Ca x V2? x O11?(3 x /2)?δ in the composition range 0.07 ≤ x ≤ 0.30 were prepared by conventional solid state reactions. The stability of different phases as a function of composition was analysed by X-ray powder diffraction, FT-IR spectra, differential thermal analysis and AC impedance spectroscopy. For the compositions x ≤ 0.10, monoclinic α-phase structure is retained at room temperature. For x = 0.13, orthorhombic β-phase is observed, whereas for x ≥ 0.17, high O2?conducting tetragonal γ-phase is stabilised. However, the highest ionic conductivity σ300°C = 3.27 × 10?4 S cm?1 was observed for x = 0.17. This higher value of conductivity of the substituted compound as compared to the parent compound can be attributed to the increased oxygen ion vacancies generated as a result of cation doping. AC impedance spectroscopy reveals the fact that this ionic conductivity is mainly due to the grain contribution. 相似文献
993.
Samples of bismuth lead vanadium oxide (BIPBVOX) (Bi2V1–xPbxO5.5–x/2) singly substituted system in the composition range 0.05 ≤ x ≤ 0.20 were prepared by sol–gel synthesis route. Structural investigations were carried out by using a combination of differential thermal analysis (DTA) and powder X-ray diffraction (PXRD) technique. Energy dispersive X-ray spectroscopy analysis (EDXA) of doped samples was carried out to predict the sample purity and doping concentration. Transitions, α?β, β?γ and γ′?γ were detected by XRD, DTA and variation in the Arrhenius plots of conductivity. The ionic conductivity was measured by AC impedance spectroscopy. The solid solutions with composition x ≤ 0.07 undergo α?β phase transition, at 329 °C and β?γ phase transition at 419 °C. The highly conducting γ′-phase was effectively stabilized at room temperature for compositions with x ≥ 0.17 whose thermal stability increases with Pb content. At 300 °C, the highest value of conductivity 6.234 × 10?5 S cm?1 was obtained for composition x = 0.15 and at 600 °C the highest value of conductivity 0.65 S cm?1 is observed for x = 0.17. AC impedance plots reveal that the conductivity is mainly due to the grain contribution to oxide ion conductivity. 相似文献
994.
995.
The polycrystalline sample of Li2Pb2Nd2W2Ti4Nb4O30 was prepared by a solid-state reaction technique. Room temperature X-ray structural analysis confirms the formation of a single-phase compound. The morphology of the sintered sample recorded by scanning electron microscope exhibits a uniform grain distribution. Detailed studies of the nature of variation of dielectric constant, tangent loss, and polarization with temperature and frequency confirmed the existence of ferroelectricity in the material at room temperature. The temperature and frequency dependence of impedance parameters (impedance, modulus, etc.) of the material exhibits a strong correlation of its microstructure (i.e., bulk, grain boundary, etc.). Furthermore, the temperature dependence of DC conductivity shows a typical Arrhenius behavior of the material. The nature of variation of pyroelectric coefficient and current with temperature suggests that material has good pyroelectric properties useful for pyroelectric detector. 相似文献
996.
本文建立了Chodorow型耦合腔慢波结构的解析模型, 利用并矢格林函数结合矩量法求解了场匹配方程, 给出了色散方程和耦合阻抗的计算式, 并数值计算出一个X波段Chodorow型慢波结构的高频特性. 结果表明, 本文方法的色散特性以及耦合阻抗与仿真软件HFSS计算的结果有很好的一致性, 且计算效率更高, 同时精度远高于等效电路法, 对工程设计有好的参考价值.
关键词:
Chodorow型耦合腔慢波结构
色散特性
耦合阻抗
场匹配 相似文献
997.
为能够较好的计算混合介质等效复介电常数和复磁导率, 提出了一种基于等效电路理论的阻抗模拟方法.导出了材料的电磁参数与材料容抗、感抗之间的对应关系, 并建立了能够较完整、精确地刻画实际复合材料的模型.通过求解混合介质的等效阻抗, 进一步反演其等效电磁参数.将计算结果与经典理论公式以及基于有限差分的数值方法进行了比较, 结果都符合得很好, 说明该方法可以用于计算材料的等效电磁参数.另外, 引入薄膜层结构来刻画表面效应等因素, 使得计算结果更加符合实验结果, 弥补了经典公式在这方面的不足, 同时也体现了该方法在刻画实际模型时所具有的优势.
关键词:
等效电磁参数
阻抗模拟
等效电路
混合介质 相似文献
998.
N. Vijayakumar E. Subramanian D. Pathinettam Padiyan 《Journal of Macromolecular Science: Physics》2013,52(8):1617-1636
Polyaniline (PANI) blends with single and double soft-templates (polyvinylpyrrolidone – PVP and/or sodium dodecylbenzenesulfonate – SDBS) were synthesized using interfacial polymerization. Fourier transform infrared (FTIR) spectral study confirmed blend formation. Polyaniline-polyvinylpyrrolidone (PANI-PVP) blend had submicron aggregates of 50–150 nm nanoparticles while PANI-SDBS blend had extensively agglomerated large size flakes/grains. Polyaniline-polyvinylpyrrolidone-sodium dodecylbenzenesulfonate (PANI-PVP-SDBS) blend had larger aggregates, besides significant number of smaller grains. Alternating current (AC) impedance analysis was performed to determine their electrical properties. At room temperature the AC conductivity of the blend materials was in the increasing order, PANI < PANI-PVP < PANI-SDBS < PANI-PVP-SDBS. But other parameters, like critical frequency and power law index s, exhibited a decreasing trend in the blend materials. With regard to frequency-dependence, all the materials showed constant AC conductivity at low frequencies, but at higher frequencies and at higher temperatures conductivity increased gradually. The obeyance of a universal power law and the range of s values (0.12 < s < 0.78) suggested a correlated barrier hopping (CBH) mechanism for AC conductivity of all the materials. The trends in electrical properties that were characteristic of the role of single/double soft-templates were explained in terms of improved π-electron delocalization and hopping mechanism. 相似文献
999.
This paper studies a model of energy harvester that consists of an electromechanical pendulum system subjected to nonlinear springs. The output power is analyzed in terms of the intrinsic parameters of the device leading to optimal parameters for energy harvesting. It is found that in an appropriate range of the springs constant, the power attains higher values as compared to the case without springs. The dynamical behavior of the device shows transition to chaos. 相似文献
1000.
讨论了RL-C并联电路阻抗值随电感、电容,以及电源频率变化的关系,给出了3种情况下最大阻抗值和谐振时的阻抗值,论证了调节电源频率或电感达到谐振时,其阻抗模并非最大值. 相似文献