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21.
反倾层状边坡弯曲折断的应力及挠度判据 总被引:4,自引:0,他引:4
以地质分析为基础 ,将反倾层状边坡的任意岩层概化为受复合作用力的板梁模型 ,通过简单的力学解析 ,开展了反倾层状岩石边坡弯曲折断判据的研究。依据岩层折断时和相临岩层的瞬时关系 ,将岩层下部视为瞬时临空状态 ,考虑岩层自重荷载和上部岩层附加荷载 (上部岩层重力荷载、层间摩擦力 )的共同作用 ,基于最大拉应力准则 ,提出了岩层弯曲折断的应力判据 ;依据应力判据 ,得到了岩层弯曲折断的挠度判据 ;利用应力判据及挠度判据 ,可实现反倾层状边坡弯曲折断的现场判定及其控制设计 相似文献
22.
本文提出一种用高密度位相型闪耀光栅测取板的曲率和斜率的单光束错位云纹干涉法,由于这一方法具有高灵敏度。大量程和高反差的优点。可有效地用来求解板的弯曲问题。文中还给出了周边固定圆板和带缺口的方板两个应用实例。 相似文献
23.
Feng-Tao LiuYou-Hua Fan Jian-Hua Yin 《Journal of Computational and Applied Mathematics》2011,235(13):3889-3897
In many mountainous areas, landslides and slope instabilities frequently occur after heavy rainfall and earthquake, and result in enormous casualties and huge economic losses. In order to mitigate the landslides hazard efficiently, a method is required for a better understanding of stability analysis. Fortunately, upper bound theorem of limit analysis provides a practical and effective upper bound approach to evaluate the stability of slopes. And in this approach, the search for the minimum factor of safety can be formulated as a nonlinear constrained optimization. In general, the SQP-type algorithms are used to solve this optimization problem. However, it is quite time consuming and difficult to search the optimum from an arbitrary starting point based on the SQP-type algorithms. Fortunately, a QP-free algorithm based on penalty function and active-set strategy can be globally convergent toward the KKT points with arbitrary starting point, and the rate of convergence is local superlinear or even quadratic. Two classical problems of slope stability are solved by this QP-free algorithm. The results show that the QP-free algorithm would be the better choice than SQP-type algorithms for solving the nonlinear constrained optimization problem which is derived from the upper bound limit analysis of slope stability. 相似文献
24.
25.
The analytical method for the determination of phosphorus in ultrapurified water was developed. Ultrapurified water was evaporated to concentrate phosphorus and the final sample volume for analysis was 10 ml. In 0.55 mol l−1 HCl, orthophosphate forms molybdophosphate, and then the molybdophosphate forms ion associate with Malachite Green (MG), which can be collected on a tiny membrane filter (diameter: 5 mm, and effective filtering diameter: 2 mm). After the ion associate on the membrane filter is dissolved together with the membrane filter in 1 ml of methyl cellosolve (MC), the absorbance of MC solution is measured at 627 nm by a flow injection-spectrophotometric detection technique. When 10 ml of the sample solution was used for the procedures and absorbance measurement, the calibration graph is linear up to about 500 ng l−1 of phosphorus and the detection limit was 8 ng l−1 (S/N=3). For the determination of phosphorus in an ultrapurified water, 10-40 ml of sample solutions were transferred into poly(tetrafluoroethylene) (PTFE) beaker and evaporated to 5 ml or to dryness. To them, 0.003 mol l−1 HCl was added to get 10 ml of final solution, which was used as sample. Phosphate is determined by comparing the slope of the varied sample volume after evaporation/concentration with a slope of the standard calibration graph (a slope comparison method: SCM). The SCM enables to evaluate the concentration of phosphate in ultrapurified waters more sensitively and accurately. 相似文献
26.
We derive the motion energy dissipation model to investigate the relation between the additional energy loss of vehicles and the slope of a gradient. Simulations are carried out to check the validity of the dissipation model. Analysis of the results shows that the total energy consumption is inversely proportional to the slope in an uphill situation and the opposite conclusion can be drawn in a downhill situation. The energy dissipation rate depends on the density of traffic and the road length in two situations in a rule. It is found that the simulation result is in good agreement with real traffic. 相似文献
27.
地下水位上升下黄土斜坡稳定性分析 总被引:4,自引:0,他引:4
黄土高原一些地区,由于塬上引水灌溉使得地下水位不断抬升,造成黄土滑坡频繁发生。地下水位变化严重影响着黄土斜坡的稳定性。基于饱和-非饱和渗流理论和延伸的摩尔-库伦破坏准则,结合室内饱和和非饱和试验结果,针对泾阳南塬一典型黄土斜坡,考虑地下水位上升情况下,对其进行了瞬态饱和-非饱和渗流分析;然后将计算得到的瞬态孔隙水压力分布用于斜坡的极限平衡分析。结果表明:地下水位上升对暂态渗流场和斜坡稳定性有明显影响;考虑非饱和渗流和吸力强度的边坡稳定分析方法更加符合实际情况。 相似文献
28.
A nonlinear planar beam formulation with stretch and shear deformations under end forces and moments
A new nonlinear planar beam formulation with stretch and shear deformations is developed in this work to study equilibria of a beam under arbitrary end forces and moments. The slope angle and stretch strain of the centroid line, and shear strain of cross-sections, are chosen as dependent variables in this formulation, and end forces and moments can be either prescribed or resultant forces and moments due to constraints. Static equations of equilibria are derived from the principle of virtual work, which consist of one second-order ordinary differential equation and two algebraic equations. These equations are discretized using the finite difference method, and equilibria of the beam can be accurately calculated. For practical, geometrically nonlinear beam problems, stretch and shear strains are usually small, and a good approximate solution of the equations can be derived from the solution of the corresponding Euler–Bernoulli beam problem. The bending deformation of the beam is the only important one in a slender beam, and stretch and shear strains can be derived from it, which give a theoretical validation of the accuracy and applicability of the nonlinear Euler–Bernoulli beam formulation. Relations between end forces and moments and relative displacements of two ends of the beam can be easily calculated. This formulation is powerful in the study of buckling of beams with various boundary conditions under compression, and can be used to calculate post-buckling equilibria of beams. Higher-order buckling modes of a long slender beam that have complex configurations are also studied using this formulation. 相似文献
29.
A novel shooting method with excellent simple control strategy is developed for solving the failure to convergence of the traditional shooting methods themselves in fiber lasers model. Compared with the published literature, the novel shooting method provides a clear physical understanding method for getting the threshold pump power and the exact results with given random functions in Yb3+-doped fiber lasers and Er3+-doped fiber lasers. Then, the results in Er3+-doped fiber lasers and Yb3+-doped fiber lasers demonstrate that the solutions using the novel shooting method has high accuracy of 10−8 W with several iteration steps, which have extended the applicable range of the end-pumped power even lower than 1 mW pump power. Furthermore, compared with 1480 nm pump for the threshold and slope efficiencies of the Er3+-doped fiber lasers, 978 nm fiber lasers can extend wider scope of application and be pump source in the coming future. Finally, the lower threshold and higher slope efficiency at 975 nm than those of 910 nm pump in Yb3+-doped fiber lasers, 975 nm pump laser provides for broad band excellent cladding pump source. 相似文献