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Microencapsulated phase change materials with paraffin as the core material were synthesized by interfacial polymerization of isophorone diisocyanate with diethylene triamine. The particle size and particle size distribution, morphology, thermal performance and the encapsulation efficiency of the prepared materials were investigated. The results of Fourier transform infrared spectrometer and X-ray photoelectron spectroscopy suggested that the paraffin core was well encapsulated by the polyurea resin. The particle size of the prepared materials decreased and its distribution became narrow with the increase of the emulsification time, stirring speed and emulsifier amount. The thermal gravimetric analysis indicated that the prepared materials exhibited good thermal stability, while the differential scanning calorimetry their high encapsulation efficiency. 相似文献
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物理气相沉积减摩与耐磨薄膜 总被引:9,自引:5,他引:9
在摩擦学研究的基础上,综合评述与探讨了物理气相沉积薄膜摩擦和磨损的机械-化学作用机理;根据这种机理分析讨论了对物理气相沉积润滑和耐磨薄膜的基本要求,提出了实现这些要求的物理气相沉积的技术基础。 相似文献
27.
G.J. Weng 《International Journal of Non》1979,14(2):123-132
The parametric response of a metallic column at elevated temperature is investigated, taking into account its non-linear viscous characteristics. An asymptotic method for the determination of the region of self-excitation and the amplitudes and phase angles for both stationary and non-stationary responses is outlined briefly. This method is applied to predict the parametric response of a 2618-T61 Al alloy column at 200°C. It is shown that the region of selfexcitation shifts away from the elastic frequency axis, that the amplitude of the stationary response increases sharply as the excitation parameters move from the stability region into the selfexcitation region and that the amplitude of the non-stationary response can be approximated by the stationary response solution for slow varying excitation frequency. 相似文献
28.
The stored energy functional of a homogeneous isotropic elastic body is invariant with respect to translation and rotation
of a reference configuration. One can use Noether's Theorem to derive the conservation laws corresponding to these invariant
transformations. These conservation laws provide an alternative way of formulating the system of equations governing equilibrium
of a homogeneous isotropic body. The resulting system is mathematically identical to the system of equilibrium equations and
constitutive relations, generally, of another material. This implies that each solution of the system of equilibrium equations
gives rise to another solution, which describes the reciprocal deformation and solves the system of equilibrium equations
of another material. In this paper we derive conservation laws and prove the theorem on conjugate solutions for two models
of elastic homogeneous isotropic bodies – the model of a simple material and the model of a material with couple stress (Cosserat
continuum).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
29.
本文提出一种解析的方法,将竖井结构看作一端简支,一端轴向弹性支承的有限长中厚园柱壳,求得其在冲击波作用下的动力响应,着重考察了地层基床系数的影响。算例表明,当主要关心Nzx值时,竖井底部简化处理成刚性固结,没有造成很大偏差。 相似文献
30.
Zhu?He Zhaohui?LiuEmail author Sheng?Chen Lei?Weng Chuguang?Zheng 《Acta Mechanica Sinica》2005,21(2):112-120
Direct numerical simulations were conducted to investigate the behavior of heavy particles in homogeneous isotropic turbulence. The present study focused on the effect of particle inertia and drift on the autocorrelations of the particle velocity and the fluid seen by particles and the dispersion characteristics of particles. The Lagrangian integral time scale of particles monotonically increased as the magnitude of the particle response time increased, while that of the fluid seen by particles remained relatively constant; it reached a maximum when the particle response time was close to the Kolmolgorov time scale of the flow. Particle dispersion increased as the particle inertia increased for small particles, while for larger particles, it decreased as particle inertia increased; particle eddy diffusion coefficient was maximal, and greater than that of the fluid by about 30%, at the preferential concentration. The concentration field of the particles with τp/τk≈1.0 showed that particles tend to collect in regions of low vorticity (high strain) due to preferential concentration. As the drift velocity of a particle is increased it crosses the paths of fluid elements more rapidly and will tend to lose correlation with its previous velocity faster than a fluid element will. And the correlation of particle velocities along the drift direction is more persistent than that perpendicular to the direction of drift. Simulations also showed that the continuity effect and the crossing-trajectory effect are weakened for particles with infinite inertia. 相似文献