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1.
Nano-sized nickel ferrite (NiFe2O4) was prepared by hydrothermal method at low temperature. The crystalline phase, morphology and specific surface area (BET) of the resultant samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and nitrogen physical adsorption, respectively. The particle sizes of the resulting NiFe2O4 samples were in the range of 5–15 nm. The electrochemical performance of NiFe2O4 nanoparticles as the anodic material in lithium ion batteries was tested. It was found that the first discharge capacity of the anode made from NiFe2O4 nanoparticles could reach a very high value of 1314 mAh g−1, while the discharge capacity decreased to 790.8 mAh g−1 and 709.0 mAh g−1 at a current density of 0.2 mA cm−2 after 2 and 3 cycles, respectively. The BET surface area is up to 111.4 m2 g−1. The reaction mechanism between lithium and nickel ferrite was also discussed based on the results of cycle voltammetry (CV) experiments.  相似文献   
2.
本文基于Pythagorean-hodograph (PH)曲线和代数双曲线的良好几何特性,构造了Pythagorean-Hodograph Hyperbolic (PH-H)曲线,并给出了PH-H曲线的定义以及相应性质.同时,分别利用Hyperbolic基函数和Algebraic Hyperbolic (AH) B\''ezier基函数,得到了平面三次AH B\''ezier曲线为PH曲线的两个不同的充要条件.此外,三次PH-H曲线也被用于求解具有确定解的$G^1$ Hermite插值问题.文中给出了具体实例来说明我们的方法.  相似文献   
3.
An analytical model is proposed to study the nonlinear interactions between beam and cable dynamics in stayed-systems. The integro-differential problem, describing the in-plane motion of a simple cable-stayed beam, presents quadratic and cubic nonlinearities both in the cable equation and at the boundary conditions. Mainly studied are the effects of quadratic interactions, appearing at relatively low oscillation amplitude. To this end an analysis of the sensitivity of modal properties to parameter variations, in intervals of technical interest, has evidenced the occurrence of one-to-two and two-to-one internal resonances between global and local modes. The interactions between the resonant modes evidences two different sources of oscillation in cables, illustrated by simple 2dof discrete models.In the one-to-two global–local resonance, a novel mechanism is analyzed, by which cable undergoes large periodic and chaotic oscillations due to an energy transfer from the low-global to high-local frequencies.In two-to-one global–local resonance, the well-known parametric-induced cable oscillation in stayed-systems is correctly reinterpreted through the autoparametric resonance between a global and a local mode. Increasing the load the saturation of the global oscillations evidences the energy transfer from high-global to low-local frequencies, producing large cable oscillations. In both cases, the effects of detuning from internal and external resonance are presented.  相似文献   
4.
The dynamic characteristic of the tires is a key factor in the road-induced interior noise in passenger vehicles. The tire acoustic cavity is a very important factor in the tire dynamics and it must be considered in analyses. This paper describes a closed form analytical model for tire-wheel structures. In order to incorporate the dynamics of the cavity on the tire response, the tire acoustic-structure coupled problem is solved simultaneously. The tire is modeled as an annular cylindrical shell where only the outside shell is flexible, i.e. tire sidewalls and wheel are assumed rigid. From the analytical solution of the eigenproblems, both the tire structure and cavity acoustic responses are expanded in terms of their eigenfunctions. The main objective of the model is to have an efficient tool to investigate the physical coupling mechanisms between the acoustic cavity and the tire structure without the need of complicated numerical model such as finite elements. The result shows that the proposed model captures the main mechanisms of the effect of the tire air acoustic on the tire dynamics.  相似文献   
5.
康廉洁  居荣兵  韩敏  刘言 《应用光学》2016,37(6):913-918
液晶显示领域不断提出缩减成本方案,对于液晶电视LED背光系统,提出了一种大角度背光透镜设计方案,即在目标接收屏面具有较大照度辐射角度的背光透镜设计。采用特定的双自由曲面设计,入光孔设置为类椭圆型结构面将光源出射的光通量进行等角度划分,根据接收屏面的理想照度分布与入光孔每一角度出射光通量对应关系计算出出光面自由曲线。借助底部微结构处理,再根据模具及产品成型要求补全外观结构,得到符合设计指标的方案,有效地解决了因增大角度引起的黄斑问题,并达到目标接受面均匀度的要求。针对32英寸(81 cm)的液晶电视背光模组,采用12颗最大正向电流为350 mA的LED灯珠,在模组高度为30 mm的系统中,设计的背光透镜模组达到了要求的亮度及均匀度。  相似文献   
6.
《Nuclear Physics B》1999,558(3):621-636
For the Lego discrepancy with M bins, which is equivalent with a χ2-statistic with M bins, we present a procedure to calculate the moment generating function of the probability distribution perturbatively if M and N, the number of uniformly and randomly distributed data points, become large. Furthermore, we present a phase diagram for various limits of the probability distribution in terms of the standardized variable if M and N become infinite.  相似文献   
7.
In the pneumatic conveying process, particles move to the bend under the influence of inertia to form a particle rope, which will cause serious wear between the particles and the pipe wall, and then the dune model is designed and installed in the 90° bend to reduce energy consumption and wear in this study. Firstly, the minimum pressure drop velocity of particles transported by different size dune models was obtained through experimental study. Then the energy saving mechanism of the dune model is studied by CFD-DEM coupling. The experimental results show that the installation of the dune model reduces the minimum pressure drop velocity. The numerical simulation results show that the number of collisions between the particles and the tube wall in the vertical tube decreases after the installation of the dune model, which reduces the energy loss. Moreover, the increasing of tail size of the dune model is beneficial to the diffusion and acceleration of the particles in the vertical tube.  相似文献   
8.
董文娟  石琳  孟双  夏磊  左慧  丁桂林 《应用光学》2017,38(5):820-825
针对目前舞台灯的光束角可变范围小、照度均匀性差等缺点,在全反射式透镜结构的基础上,基于变焦透镜组原理,设计出一种采用单颗透镜的变焦透镜系统。该系统包括准直透镜和可移动的调焦片,并且使用SolidWorks软件,依次在准直透镜的镜面上进行不规则六边形复眼圆周填充阵列和调焦片的两侧进行六边形复眼圆周阵列设计。经过光学软件LightTools仿真以及实际光照效果检测,此款透镜在匹配S2WP的全彩LED光源后,上述结构能够有效解决RGBW全彩LED光源在舞台灯照明上均匀性和混光差的难题。此外,设计出的舞台灯变焦透镜的光学效率高达87%,可在0 mm~15 mm的调焦范围内,光束角(1/2光强角)的可变范围为4°~53°。  相似文献   
9.
Diffusion coefficients of the Fe2(SO4)3)/water system at T = 298.15 K and at concentrations between 0.050 mol · dm−3 and 0.200 mol · dm−3 have been measured, using a conductimetric cell and an automatic apparatus to follow diffusion. The cell uses an open-ended capillary method. A conductimetric technique is used to follow the diffusion process by measuring the resistance of a solution inside the capillaries at recorded times. These data are discussed on the basis of the Onsager–Fuoss model. The diffusion of Fe2(SO4)3 is clearly affected by the Fe (III) hydrolysis. These data permit us to have a better understanding of the structure of such systems and the thermodynamic behaviour of ferric sulphate in different media.  相似文献   
10.
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