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排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
利用Galerkin方法,研究了一类具有结构阻尼的kirchhoff型波动方程,方程是截面弹性杆运动的模型.通过各种不等式技巧及算子半群理论,证明了方程的解半群具有全局吸引子. 相似文献
992.
A theorem upon refractive index as a function of wavelength is derived starting from the Taylor expansion around the origin of this function. Our result involves the above index, the group index, and the coefficient of material dispersion all extrapolated to zero wavelength. 相似文献
993.
Régis Brugiere et Pierre Lucasson 《辐射效应与固体损伤》2013,168(1):55-57
The nature of the electron bombarded aluminium electrical recovery process has been studied by combining quenches with irradiations. Measured Frenkel pair formation rates per incident electrons as well as annealing kinetics emphasize the role of impurity interstitial trapping. 相似文献
994.
995.
996.
A. M. Il'in R. Z. Khasminskii G. Yin 《Journal of Optimization Theory and Applications》1999,102(3):555-591
Motivated by many problems in optimization and control, this paper is concerned with singularly perturbed systems involving both diffusions and pure jump processes. Two models are treated. In the first model, the jump process changes very rapidly by comparison with the diffusion processes. In the second model, the diffusions change rapidly in comparison with the jump process. Asymptotic expansions are developed for the transition density vectors via a constructive method; justification of the asymptotic expansions and analysis of the remainders are provided. 相似文献
997.
998.
This paper discusses the importance of realistic implementation of the physical boundary conditions into computational domain for the simulation of the oscillatory turbulent boundary layer flow over smooth and rough flat beds. A mathematical model composed of the Reynolds averaged Navier–Stokes equation, turbulent kinetic energy (k) and dissipation rate of the turbulent kinetic energy (ε) has been developed. Control‐volume approach is used to discretize the governing equations to facilitate the numerical solution. Non‐slip condition is imposed on the bottom surface, and irrotational main flow properties are applied to the upper boundary. The turbulent kinetic energy is zero at the bottom, whereas the dissipation rate is approaching to a constant value, which is proportional to the kinematic viscosity times the second derivative of the turbulent kinetic energy. The output of the model is compared with the available experimental studies conducted in oscillatory tunnels and wave flume. It is observed that the irrotational flow assumption at the upper boundary is not realistic in case of water tunnels. Therefore, new upper boundary conditions are proposed for oscillatory tunnels. The data of wave flume show good agreement with the proposed numerical model. Additionally, several factors such as grid aspect ratio, staggered grid arrangement, time‐marching scheme and convergence criteria that are important to obtain a robust, realistic and stable code are discussed. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
999.
V. Svetsov 《Shock Waves》2001,11(3):229-244
A new nonstationary regime of the flow around a step and a cylinder was found to exist at high free-stream Mach numbers for
gas specific heat ratios below 1.2. The main features of the flow are strong vortices in the shock-compressed region with
supersonic reversal velocities at the body face. The bow shock wave takes on a complicated shape, fluctuating in time. The
vortical regimes can result from local heterogeneities in the free stream. The case of the heterogeneity is studied in this
paper in the form of a thin thermal layer of limited length. The vortical regime remains in existence after the source of
disturbances is removed. The results have been obtained through computer simulations through the use of Eulerian hydrodynamic
equations and by way of several numerical methods: FLIC, Godunov's scheme, TVD, and PPM. The influence of viscosity on the
development of the vortical regime has been studied by computer solving the Navier–Stokes equations.
Received 21 August 1998 / Accepted 6 June 2001 相似文献
1000.
This paper presents a comprehensive comparison of the mean velocity and turbulence measurements from a four-hole pressure probe, also known as the Cobra probe, and an X-probe in plane mixing layers. The objective is to validate the measurement accuracy of the Cobra probe in a flow where the turbulence reaches high levels, but whose properties are well known. The comparison is made for the mean velocities, Reynolds stresses, triple products, and spectra, and demonstrates that the Cobra probe has reasonable accuracy for some of these quantities, such as the mean streamwise velocity and primary shear stress, but not for others, such as the mean normal velocity. The correlation of the pressure and the streamwise velocity, measured by the Cobra probe, behaves correctly in the potential flow. However, the correlation of the pressure and the cross-stream velocity, which appears in the transport equation for the turbulent kinetic energy, and the pressure redistribution term in the corresponding equation for the streamwise normal stress, are poorly measured. 相似文献