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81.
Donato Ercole Conte Abdelmaula Aboulaich Josette Olivier-Fourcade Christian Jordy 《Journal of solid state chemistry》2010,183(1):65-6650
A comparative study of two Sn-based composite materials as negative electrode for Li-ion accumulators is presented. The former SnB0.6P0.4O2.9 obtained by in-situ dispersion of SnO in an oxide matrix is shown to be an amorphous tin composite oxide (ATCO). The latter Sn0.72[BPO4]0.28 obtained by ex-situ dispersion of Sn in a borophosphate matrix consists of Sn particles embedded in a crystalline BPO4 matrix. The electrochemical responses of ATCO and Sn0.72[BPO4]0.28 composite in galvanostatic mode show reversible capacities of about 450 and 530 mAh g−1, respectively, with different irreversible capacities (60% and 29%). Analysis of these composite materials by 119Sn Mössbauer spectroscopy in transmission (TMS) and emission (CEMS) modes confirms that ATCO is an amorphous SnII composite oxide and shows that in the case of Sn0.72[BPO4]0.28, the surface of the tin clusters is mainly formed by SnII in an amorphous interface whereas the bulk of the clusters is mainly formed by Sn0. The determination of the recoilless free fractions f (Lamb-Mössbauer factors) leads to the effective fraction of both Sn0 and SnII species in such composites. The influence of chemical composition and especially of the surface-to-bulk tin species ratio on the electrochemical behaviour has been analysed for several Snx[BPO4]1−x composite materials (0.17<x<0.91). The cell using the compound Sn0.72[BPO4]0.28 as active material exhibits interesting electrochemical performances (reversible capacity of 500 mAh g−1 at C/5 rate). 相似文献
82.
使用草酸盐共沉淀法合成了LiNi0.5Mn0.5O2, 并研究了共沉淀时的pH条件对终产物的结构、形貌及电化学性能的影响. 采用X射线衍射(XRD)和扫描电镜(SEM)表征了在pH值为4.0、5.5、7.0和8.5时得到的共沉淀和终产物LiNi0.5Mn0.5O2的结构和形貌. 使用充放电实验研究了不同pH条件下得到的LiNi0.5Mn0.5O2的电化学性能. 结果表明, pH为7.0时, 合成的材料颗粒更小、分布最均匀, 材料具有良好的层状特征, 且材料中锂镍的混排程度最小. 电化学测试结果印证了pH为7.0时合成的材料具有更好的电化学性能, 在0.1C的倍率下, 材料的首次放电比容量达到了185 mAh·g-1, 在循环20周后, 放电比容量仍然保持在160 mAh·g-1. X射线光电子能谱(XPS)测试结果表明, pH为7.0时合成的LiNi0.5Mn0.5O2中Ni为+2价, Mn为+4价. 相似文献
83.
采用稳态平板法测量不良导体的导热系数时,关键是得到稳态时不良导体的传热速率。根据稳态时传热速率与散热铝盘的散热速率相等,可以测定自然冷却过程中,稳态时散热铝盘温度T2所对应的冷却速率。基于Matlab软件,分析并绘制曲线直观反映出温度、时间、冷却速率三者之间的关系,用拟合法研究了不良导体导热系数随温度变化的关系。 相似文献
84.
将镜像法和保角变换法相结合,计算由线电荷与接地半无限大导体板所形成的电场,给出其电势分布和场强分布,进一步得出等势线方程和电场线方程,并利用数学软件MATLAB绘制出等势线图和电场线图. 相似文献
85.
It was investigated whether a perovskite-type proton conductor, here BaCe0.95Y0.05O3 − δ (BCY), is suitable as sensing material for a novel type of thermoelectric hydrogen sensor. Therefore, the hydrogen and oxygen concentration dependence of the thermopower of BaCe0.95Y0.05O3 − δ was determined and was found to be in the same range as the value derived from theory. The hydrogen dependence was also measured at different temperatures, and only a comparatively small temperature dependence of the thermopower was observed. 相似文献
86.
Two kinds of spinel LiMn2O4 thin film for lithium ion micro-batteries were successfully prepared on polycrystal Pt substrates by spin coating methods, which were carried out under ultrasonic irradiation (USG) and magnetic stirring (MSG), respectively. The microstructures and electrochemical performance of LiMn2O4 thin films were characterized by thermogravimetry analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and galvanostatic charge-discharge measurements. It was found that the crystalline structure of USG samples grew better than that of the MSG samples. At the same time, higher discharge capacity and better cycle stability were obtained for the LiMn2O4 thin films of USG at the current density of 50 μAh/cm2 between 3.0 and 4.3 V. The 1st discharge capacity was 57.8 μAh/cm2-μm for USG thin films and 51.7 μAh/cm2-μm for MSG thin films. After 50 cycles, 91.4% and 69% of discharge capacity could be retained respectively, indicating that ultrasonic irradiation condition during spin coating was more suitable for preparing spinel LiMn2O4 thin films with better electrode performance for lithium ion micro-batteries. 相似文献
87.
In order to develop mixed protonic and electronic conductors, we proposed a novel concept for material design that enables to control partial conductivities by fabricating solid solutions of protonic and electronic conductors. In this work, Sr-doped LaBO3 and Sr-doped CeBO3 were chosen as model compounds conducting protons and electron holes, respectively. Solid solutions of the above borates, Sr-doped La1 − xCexBO3, were prepared, and their electrical conductivities were investigated in 8.5 × 102-4.2 × 103 Pa of p(H2O) and 1.0 × 10-1.0 × 105 Pa of p(H2) at 1073 K. From the experimental results of the gas partial pressure dependences of the conductivities, major charge carrier species were identified as a function of x. It was found that proton was the major charge carrier when x < 0.2 while the contribution of the electron hole conduction became remarkable as x increased above 0.2. The contribution of the electron hole conduction can be interpreted by the percolation model. 相似文献
88.
Rare earth doped BaZrO3 is one of most promising proton conducting oxides as it has high proton conductivity and sound chemical stability. Sintering aids such as ZnO, however, should be incorporated in order to improve poor sinterability. In this study, the effects of adding ZnO on proton conductivity of Yb-doped BaZrO3 (BZYb) were investigated. From the electrical conductivities measured under various water vapor pressures, concentration and mobility of the proton were obtained. Proton mobility of BZYb with ZnO (BZYb-Zn) was smaller than that of BZYb while hydration enthalpy of BZYb-Zn was more negative than that of BZYb. 相似文献
89.
We study a rechargeable lithium-ion battery that uses a many-particle FePO4 electrode to reversibly store lithium atoms. This process is accompanied by a phase transition and charging/discharging run along different paths, so that hysteretic behavior is observed.Although there are experimental studies suggesting that the overall behavior of the battery is a many-particle effect, most authors exclusively describe the phase transition within a single particle model of the electrode.In this work, we study in detail a many-particle model for the electrode. The model is capable to describe a kind of phase transition where each individual particle of the electrode is homogeneous. It will be shown that the particles are either in the first phase or in the second phase. This phenomenon is due to the non-monotone relation between the chemical potential and the lithium mole fraction of a single particle.The pressure-radius relation of a spherical elastic rubber balloon also exhibits non-monotone behavior. In fact, a system of many interconnected balloons behaves correspondingly to an electrode consisting of many storage particles. The analogy between the two systems is important, because the predictions of the many-particle model can easily be tested with rubber balloons of macroscopic size than with an ensemble of microscopically small (FePO4) particles. 相似文献
90.
Emiliana Fabbri Isaac Markus Lei BiDaniele Pergolesi Enrico Traversa 《Solid State Ionics》2011,202(1):30-35
BaZr0.8 − xPrxY0.2O3 − δ (BZPYx, 0.1 ≤ x ≤ 0.4) perovskite oxides were investigated for application as cathode materials for intermediate temperature solid oxide fuel cells based on proton conducting electrolytes (protonic-SOFCs). The BZPYx reactivity with CO2 and water vapor was evaluated by thermogravimetric and X-ray diffraction analyses, and good chemical stability was observed for each BZPYx composition. Conductivity measurements of BZPYx sintered pellets were performed as a function of temperature and pO2 in humidified atmospheres, corresponding to cathode operating condition in protonic-SOFCs. Different conductivity values and activation energies were measured depending on the Pr content, suggesting the presence of different charge carriers. For all the compositions, the partial electronic conductivity, calculated from conductivity measurements at different pO2, increased with increasing the temperature from 500 to 700 °C. Furthermore, the larger the Pr content, the larger the electronic conductivity. BaZr0.7Pr0.1Y0.2O3 − δ and BaZr0.4Pr0.4Y0.2O3 − δ showed mostly pure proton and electron conductivity, respectively, whereas the intermediate compositions showed mixed proton/electronic conductivity. Among the two mixed proton/electronic conductors, BaZr0.6Pr0.3Y0.2O3 − δ presented the larger conductivity, which coupled with its good chemical stability, makes this perovskite oxide a candidate cathode materials for protonic-SOFCs. 相似文献