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991.
A third-order numerical scheme is presented to give approximate solutions to multi-dimensional hyperbolic conservation laws only using modified coefficients of an essentially non-oscillatory (MCENO) scheme without increasing the base points during construction of the scheme. The construction process shows that the modified coefficient approach preserves favourable properties inherent in the original essentially nonoscillatory (ENO) scheme for its essential non-oscillation, total variation bounded (TVB), etc. The new scheme improves accuracy by one order compared to the original one. The proposed MCENO scheme is applied to simulate two-dimensional Rayleigh-Taylor (RT) instability with densities 1:3 and 1:100, and solve the Lax shock-wave tube numerically. The ratio of CPU time used to implement MCENO, the .third-order ENO and fifth-order weighed ENO (WENO) schemes is 0.62:1:2.19. This indicates that MCENO improves accuracy in smooth regions and has higher accuracy and better efficiency compared to the original ENO scheme. 相似文献
992.
The theory of an eddy viscosity model is applied to the study of the flow in a compound channel which is partially vegetated. The governing equation is constituted by analyzing the longitudinal forces acting on the unit volume where the effect of the vegetation on the flow is considered as a drag force item, The compound channel is divided into 3 sub-regions in the transverse direction, and the coefficients in every region's differential equations were solved simultaneously. Thus, the analytical solution of the transverse distribution of the depth-averaged velocity for uniform flow in a partially vegetated compound channel was obtained. The results can be used to predict the transverse distribution of bed shear stress, which has an important effect on the transportation of sediment. By comparing the analytical results with the measured data, the analytical solution in this paper is shown to be sufficiently accurate to predict most hydraulic features for engineering design purposes. 相似文献
993.
994.
Although boundary displacement and traction are independent field variables in boundary conditions of an elasticity problem at a non-singular boundary point, there exist definite relations of singularity intensities between boundary displacement derivatives and tractions at a singular boundary point. The analytical forms of the relations at a singular smooth point for 2D isotropic elastic problems have been established in this work. By using the relations, positions of the singular boundary points and the corresponding singularity intensities of the unknown boundary field variables can be determined a priori. Therefore, more appropriate shape functions of the unknown boundary field variables in singular elements can be constructed. A numerical example shows that the accuracy of the BEM analysis using the developed theory is greatly increased. 相似文献
995.
Design method for fluid viscous dampers 总被引:2,自引:0,他引:2
Jia Jiuhong Du Jianye Wang yu Hua Hongxing 《Archive of Applied Mechanics (Ingenieur Archiv)》2008,78(9):737-746
A basic design method of doubly acting fluid viscous dampers with double guide bars is presented. The flow of the viscoelastic
fluid between two parallel plates, one of which is started suddenly and the other of which is still, is analyzed. According
to this solution, the velocity and the shear stress of the fluid at the fringe of the piston are solved approximately. A mathematical
model of viscous dampers is derived, and the shock test is carried out. From experimental results, the parameters of the mathematical
model are determined. Consequently, a semi-empirical design equation is obtained. Applying this equation to a certain practical
damper, the damping material is chosen and the physical dimensions of the damper are determined. Shock tests using this damper
are performed. Theoretical results are in good agreement with experimental results, which validates the reliability of the
calculated physical dimensions of the specimen damper and the validity of the basic design equation.
An erratum to this article can be found at 相似文献
996.
997.
The paper studies the fall and ascent in air of a spherical body with radius linearly decreasing with time. The first integral
of the nonlinear equation of motion is expressed in closed form in terms of Bessel functions on the assumption that the aerodynamic
drag depends on the velocity as a quadratic polynomial. The second integral is evaluated by an approximate formula. The reliability
of the analytic solution is confirmed by comparing it with a numerical solution of the Cauchy problem
__________
Translated from Prikladnaya Mekhanika, Vol. 44, No. 6, pp. 118–125, June 2008. 相似文献
998.
T形型钢混凝土柱正截面承载力的计算方法探讨 总被引:3,自引:0,他引:3
在总结了型钢混凝土(SRC)柱承载力计算一般方法的基础上,针对T形型钢混凝土柱,
结合中国现行规范,分析了此种柱的受力特点和破坏模式,提出T形型钢混凝土柱正截面极
限承载力的计算方法,并采用该方法对一T形型钢混凝土柱的承载力进行验算. 结果表明与
试验数据吻合较好,说明本文方法具有较好的精确度和适用性. 相似文献
999.
Measurements of aerosol number concentration and particulate matter with diameter less than 10μm (PM10) mass concentrations of urban background aerosols were performed in Fengtai area, Beijing in 2006. Black carbon (BC) was collected simultaneously from the ground and analyzed to determine the particulate matter components. To satisfy the interest in continuous monitoring of temporal and spatial distribution of aerosols, the relationship between extinction coefficient (visibility) measured by lidar remote sensing and the aerosol number concentration measured from the ground was derived by using statistical method. Vertical particle number concentration profile within the planetary boundary layer could be inversed through the lidar data as well as the statistical relation. 相似文献
1000.
Aerosol observation in Fengtai area, Beijing 总被引:1,自引:0,他引:1
Zengdong Liu Jianguo Liu Bei Wang Fan Lu Shuhua Huang Dexia Wu Daowen Han 《Particuology》2008,6(3):214-217
Measurements of aerosol number concentration and particulate matter with diameter less than 10 μm (PM10) mass concentrations of urban background aerosols were performed in Fengtai area, Beijing in 2006. Black carbon (BC) was collected simultaneously from the ground and analyzed to determine the particulate matter components. To satisfy the interest in continuous monitoring of temporal and spatial distribution of aerosols, the relationship between extinction coefficient (visibility) measured by lidar remote sensing and the aerosol number concentration measured from the ground was derived by using statistical method. Vertical particle number concentration profile within the planetary boundary layer could be inversed through the lidar data as well as the statistical relation. 相似文献