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51.
WeiJieFENG 《数学学报(英文版)》2004,20(6):983-988
In this paper, we obtain some existence results for a class of singular semilinear elliptic problems where we improve some earlier results of Zhijun Zhang. We show the existence of entire positive solutions without the monotonic condition imposed in Zhang‘s paper. The main point of our technique is to choose an approximating sequence and prove its convergence. The desired compactness can be obtained by the Sobolev embedding theorems. 相似文献
52.
The existence of rub-impact periodic motions in an eccentric rotor system is considered. A criterion for the periodicity condition of n-periodic impacts is derived and other conditions for real rub-impacts are also discussed. A method consisting of analytical and numerical techniques is presented to solve the existence problem of rub-impact periodic motions. Some special results are obtained by theoretical analyses for rub-impact rotor systems, including the existence of grazing circle motions and that of single-impact periodic motions. 相似文献
53.
54.
随着智能交通技术的发展,可变信息标志(VMS)被广泛应用于动态交通管理中.元胞传输模型(CTM)可以较好地模拟交通流激波、排队形成与消散等交通流动力学特性.应用CTM对VMS选址问题进行了研究.数值模拟结果表明,合适的VMS位置可以减少系统内所有车辆的行驶时间.还分析了路径选择概率变化与VMS位置之间的关系.在一定范围内,交通事故越严重,VMS应设置在距离事故地点越远的地方.
关键词:
可变信息标志
选址问题
元胞传输模型
数值模拟 相似文献
55.
56.
通过赝势平面波法(CASTEP)及全电势线性缀加平面波法(FLAPW),以bcc-Fe为对象,研究第一性原理计算立方结构Fe基磁性材料弹性系数的方法,分析影响计算立方结构Fe基磁性材料弹性系数准确度的各项因素. 结果表明,在第一性原理弹性系数计算中,晶格常数是决定弹性系数计算准确度的关键因素;势函数的选择也会影响计算准确度. 使用全电势基矢的FLAPW法可以得到更为精准的弹性系数计算结果. 计算得到bcc-Fe的弹性系数C11,C12,C44分别为246 GPa,121 GPa,113 GPa,与实验值基本一致. 利用本方法,计算了新型Fe-Ga磁致伸缩材料的弹性系数C11,C12,C44分别为207 GPa,166 GPa及108 GPa.
关键词:
弹性系数
磁致伸缩材料
赝势平面波法
全电势线性缀加平面波法 相似文献
57.
光学外差探测信噪比研究 总被引:3,自引:2,他引:3
对于光学外差探测系统而言,为了有效利用回波信号,需要对信噪比这一表征系统性能的重要指标进行研究。从理论分析了信噪比,给出了计算信噪比的一般公式。理论分析表明,当探测器光敏面上本振光与信号光的振幅、相位、偏振都满足严格的匹配时,外差效率最大。对场分布为艾里函数的光外差信噪比进行研究和数值模拟。结果表明,当艾里斑尺寸的比例系数控制在0.8~1.2内,并使信号光斑主轴偏移量x0控制在0.5以下,探测器的尺寸在(0.6~0.8)λf/d内时,可获得大于0.7ηPs/hνB的信噪比。 相似文献
58.
The electronic structure and magnetic properties of the Co at the Co/X (X=Co, Cu, V and Ta) interfaces have been studied by first-principle discrete variational method. We have found that the spin asymmetry and the s-electron itinerancy of the Co interface layer in the Co/X systems are strongly dependent on the electronegativity of the non-magnetic layers. A large difference in the electronegativity between the non-magnetic and Co layers is unfavorable both for s-electron itinerancy and for the spin exchange split of DOS at the Fermi level. Further study on charge density has revealed that a bond is formed across the Co/V and Co/Ta interfaces. 相似文献
59.
The supercurrent through a double Aharonov–Bohm interferometer formed by parallel-coupled four quantum dots is investigated theoretically. The possibility of controlling the supercurrent of the system is explored by tuning the interdot coupling, dot energy levels, and magnetic flux treading the ring connecting dots and leads. Whether the supercurrent sign can be changed depends not only on the magnetic flux but also on the quantum dot energy levels. By tuning the quantum dot energy levels, the behavior of the supercurrent shows swap effects, which might be used to design a qubit. It is also found that the oscillation period of the supercurrent with respect to the magnetic flux depends on the ratio of the two parts fluxes. 相似文献
60.
The electronic band structures of wurtzite GaN with Ga and N vacancy defects are investigated by means of the first-principles total energy calculations in the neutral charge state. Our results show that the band structures can be significantly modified by the Ga and N vacancies in the GaN samples. Generally, the width of the valence band is reduced and the band gap is enlarged. The defect-induced bands can be introduced in the band gap of GMV due to the Ga and N vacancies. Moreover, the GaN with high density of N vacancies becomes an indirect gap semiconductor. Three defect bands due to Ga vacancy defects are created within the band gap and near the top of the valence band. In contrast, the N vacancies introduce four defect bands within the band gap. One is in the vicinity of the top of the valence band, and the others are near the bottom of the conduction band. The physical origin of the defect bands and modification of the band structures due to the Ga and N vacancies are analysed in depth. 相似文献