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The first-principles calculations are employed to investigate the stability, magnetic, and electrical properties of the oxide heterostructure of LaAlO3/SrTiO3(110). By comparing their interface energies, it is obtained that the buckled interface is more stable than the abrupt interface. This result is consistent with experimental observation. At the interface of LaAlO3/SrTiO3(110) heterostructure, the Ti–O octahedron distortions cause the Ti t2 gorbitals to split into the twofold degenerate dxz/dyz and nondegenerate dxy orbitals. The former has higher energy than the latter. The partly filled two-fold degenerate t2 gorbitals are the origin of two-dimensional electron gas, which is confined at the interface. Lattice mismatch between LaAlO3 and SrTiO3leads to ferroelectric-like lattice distortions at the interface, and this is the origin of spin-splitting of Ti 3d electrons. Hence the magnetism appears at the interface of LaAlO3/SrTiO3(110). 相似文献
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运用激光雷达方程和Fernald方法,对西藏那曲地区和北京地区对流层气溶胶的微脉冲激光雷达(MPL)探测数据进行时空反演和比较,结果表明:气溶胶散射比廓线有着较为相似的结构分布,分层锯齿结构非常明显,主要包括贴地层、气溶胶混合层和气溶胶对流层。那曲测站上空气溶胶散射比在无云条件下最大值基本上保持在2.0左右;在测站上空均存在密度较大且较厚的积云;夏季的混合层或残留层(浅蓝色部分)高度抬高;夏季对流层低层积云的云量和积云出现的概率较冬季要少。 相似文献
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Molecular dynamics with the stochastic process provides a convenient way to compute structural and thermodynamic properties of chemical, biological, and materials systems. It is demonstrated that the virtual dynamics case that we proposed for the Langevin equation[J. Chem. Phys. 147, 184104 (2017)] in principle exists in other types of stochastic thermostats as well. The recommended "middle" scheme[J. Chem. Phys. 147, 034109 (2017)] of the Andersen thermostat is investigated as an example. As shown by both analytic and numerical results, while the real and virtual dynamics cases approach the same plateau of the characteristic correlation time in the high collision frequency limit, the accuracy and efficiency of sampling are relatively insensitive to the value of the collision frequency in a broad range. After we compare the behaviors of the Andersen thermostat to those of Langevin dynamics, a heuristic schematic representation is proposed for understanding efficient stochastic thermostatting processes with molecular dynamics. 相似文献
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研究了不同粒度的Si3N4粉体对制备的逆反应烧结Si3N4-SiC复合材料性能的影响。结果表明:同一升温制度下,Si3N4粒度从0.074 mm减小到0.045 mm,Si3N4-SiC复合材料体积密度增大,显气孔率变低,抗折强度降低。随着Si3N4粒度减小,材料中的Si3N4含量降低;中温保温从900℃升到1200℃,Si3N4含量升高;高温保温温度从1350℃到1500℃,材料内部氧化程度增高,Si3N4含量降低,SiO2含量升高;Si3N4-SiC复合材料玻璃相增多,玻璃相中有SiO2晶体析出,使得孔隙被生成的玻璃相和发育的SiO2晶粒填充,材料的气孔减少。 相似文献
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本文通过对Nd1.85Ce0.15CuO4±δ单晶ab面(ρab)和c方向电阻率(ρc)的测量,发现未经过氮气退火的样品的ρc与温度成线性依赖关系,但是同一个样品经过氮气退火后的ρc中不仅有一次方的温度依赖关系还有二次方的.这说明样品经过氮气退火后,电子与空穴两种载流子共同参与导电.样品在退火处理前的各向异性比(ρc-ρc0)/(ρab-ρab0)存在强的温度依赖关系,这是由于ρc与温度成线性依赖关系,然而ρab不仅有一次方的温度依赖关系还有二次方的.样品经过退火处理后的各向异性比存在弱的温度依赖赖关系,这是由于ρc与ρab中都同时有一次方和二次方的温度依赖关系.我们用电子和空穴沿c方向有不同的隧穿几率来解释ρc和(ρc-ρc0)/(ρab-ρab0). 相似文献
60.
Ferroelectric Properties of Polycrystalline Ceramics with Dipolar Defect Simulated from the Potts--Ising Model
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Physical properties of polycrystailine ferroelectrics including the contributions of the fixed dipolar defects and the average grain size in the Potts-Ising model are simulated by using the Monte Carlo method. Domain pattern, hysteresis loop and switching current of the polarization reversal process are obtained. Two processes are considered in our simulation. In the first one, the grain texture of ferroelectric ceramics are produced from the Ports model, and then the Ising model is implemented in the obtained polycrystailine texture to produce the domain pattern, hysteresis loop and switching current. It is concluded that the defect has the ability to decrease the remnant polarization P~ as well as the coercive field E~. The back switching is obviously observed after the electric field is off, and it shows some variation after introducing the fixed dipolar defect. Meanwhile, the spike of the switching current is found to lower with the increasing defect concentration and the decreasing average grain size. 相似文献