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排序方式: 共有166条查询结果,搜索用时 62 毫秒
31.
给出了在动应力、动位移和动稳定约束下离散变量结构布局优化设计问题的数学模型,用“拟静力”算法,将具有动应力约束、动位移约束和动稳定约束的离散变量结构布局优化设计问题化为静应力、静位移和静稳定约束的优化问题,然后利用两级优化算法求解该模型.优化过程由两级组成,拓扑级优化和形状级优化.在每一级,都使用了综合算法,并且在搜索过程中都根据两类设计变量的相对差商值进行搜索.对包含稳定约束和不包含稳定约束的优化结果做了比较,结果显示稳定性约束对优化结果产生较大的影响. 相似文献
32.
一种桁架结构智能生成与分析系统 总被引:1,自引:0,他引:1
建立了桁架结构的智能生成与分析系统,可以自动完成桁架结构的布局选型、
拓扑生成以及分析计算等系列过程. 主要通过结点布置和有选择的杆件连接实现结构的布局
选型,采用拓扑变化法完成结构的自动生成,并利用基内力阵进行结构的分析计算. 经算例
分析表明,该系统性能良好,使用方便,具有智能、自适应的特点,是辅助完成结构拓扑和
布局优化设计的有力工具之一. 相似文献
33.
Study of total ionizing dose radiation effects on enclosed gate transistors in a commercial CMOS technology 下载免费PDF全文
This paper studies the total ionizing dose radiation effects on MOS
(metal-oxide-semiconductor) transistors with normal and enclosed gate
layout in a standard commercial CMOS (compensate MOS) bulk process.
The leakage current, threshold voltage shift, and transconductance of
the devices were monitored before and after $\gamma $-ray
irradiation. The parameters of the devices with different layout
under different bias condition during irradiation at different total
dose are investigated. The results show that the enclosed layout not
only effectively eliminates the leakage but also improves the
performance of threshold voltage and transconductance for NMOS
(n-type channel MOS) transistors. The experimental results also
indicate that analogue bias during irradiation is the worst case for
enclosed gate NMOS. There is no evident different behaviour observed
between normal PMOS (p-type channel MOS) transistors and enclosed
gate PMOS transistors. 相似文献
34.
本文采用Donnell型扁壳理论,首先利用最小势能原理和广义平均筋条刚度法推导出用位移分量表示的复合材料三角形网格加筋叠层圆锥壳体的稳定性方程,考虑了蒙皮最一般的拉弯与拉扭耦合关系和加筋筋条的偏心效应,并讨论了该方程的基本性质.根据外压实验观察结果,通过选取适当的位移分量表达式,并运用Galerkin法分析了在均布外压作用下复合材料三角形网格加筋叠层圆锥壳体总体稳定性,得到了临界载荷的解析表达式,并对某一类C/E复合材料三角形内网格加筋圆锥壳体的临界外压进行了计算,所得理论值与实验结果很好地吻合.最后,讨论了有关参数对临界载荷的影响.本文所建立的新方程和所得结果对于航空航天结构非常有用. 相似文献
35.
《力学快报》2020,10(5):366-376
A new computational procedure for modelling the structural behavior of stiffened plates with symmetry boundary conditions is here presented. It uses two-dimensional finite elements as a way to decrease computational time without losing precision thanks to a relatively small number of elements applied for analyzing out-of-plane displacements (deflections) and stresses. Adding, the constructal design method was included in the procedure, together with the exhaustive search technique, with the scope to optimize the stress/strain status of stiffened plates by design changes. For the purpose, a reference plate without stiffeners was initially design and used as starting point. Part of the volume was reshaped into stiffeners: thickness was reduced maintaining unchanged weight, length and width. The main goal was to minimize strains and stresses by geometric changes. Results demonstrated that, thanks to this design procedure, it is always possible to find an adequate geometry transformation from reference plate into stiffeners, allowing significant improvements in mechanical behavior. 相似文献
36.
37.
基于第十一届"华为杯"全国研究生数学建模竞赛E题第五问,针对一类多车型多目的地的整车物流运输调度问题,先直接计算完成总任务所需的车辆数来阐明该题的最优解的下界限为113辆,再对原始数据进行预处理,基于对乘用车的分类与排样算法,筛选出每种轿运车的M种装载方案代表,再对目的地位置及结合各目的地的任务需求,确定出3条不绕行路线,根据启发式调整优化算法,并以轿运车使用量最少及总行驶里程最短为优化目标,建立了多目标整数规划模型进行求解,最优可行解为114辆,其中1-1型91辆,1-2型18辆,2-2型5辆. 相似文献
38.
Gianni Royer-Carfagni 《Journal of Elasticity》2000,60(2):103-117
We consider a homogeneous orthotropic elastic wedge in plane stress loaded by a concentrated force at the apex. The orthotropic
material is conceived of to be formed by a matrix reinforced by a triangular net of elastic fibers, so that the fiber size
and the net shape determine the average elastic moduli of the composite material. It is found that maintaining fixed the amount
of material used for the reinforcement, there exists a particular fiber disposal which maximizes the stiffness of the wedge.
The optimal disposal is different-in-type for diverse opening-angles of the wedge.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
39.
The single row facility layout problem (SRFLP) is the problem of arranging facilities with given lengths on a line, while minimizing the weighted sum of the distances between all pairs of facilities. The problem is NP-hard. In this paper, we present two tabu search implementations, one involving an exhaustive search of the 2-opt neighborhood and the other involving an exhaustive search of the insertion neighborhood. We also present techniques to significantly speed up the search of the two neighborhoods. Our computational experiments show that the speed up techniques are effective, and our tabu search implementations are competitive. Our tabu search implementations improved previously known best solutions for 23 out of the 43 large sized SRFLP benchmark instances. 相似文献
40.
《Journal of computational and graphical statistics》2013,22(2):444-472
We discuss methodology for multidimensional scaling (MDS) and its implementation in two software systems, GGvis and XGvis. MDS is a visualization technique for proximity data, that is, data in the form of N × N dissimilarity matrices. MDS constructs maps (“configurations,” “embeddings”) in IRk by interpreting the dissimilarities as distances. Two frequent sources of dissimilarities are high-dimensional data and graphs. When the dissimilarities are distances between high-dimensional objects, MDS acts as a (often nonlinear) dimension-reduction technique. When the dissimilarities are shortest-path distances in a graph, MDS acts as a graph layout technique. MDS has found recent attention in machine learning motivated by image databases (“Isomap”). MDS is also of interest in view of the popularity of “kernelizing” approaches inspired by Support Vector Machines (SVMs; “kernel PCA”).This article discusses the following general topics: (1) the stability and multiplicity of MDS solutions; (2) the analysis of structure within and between subsets of objects with missing value schemes in dissimilarity matrices; (3) gradient descent for optimizing general MDS loss functions (“Strain” and “Stress”); (4) a unification of classical (Strain-based) and distance (Stress-based) MDS.Particular topics include the following: (1) blending of automatic optimization with interactive displacement of configuration points to assist in the search for global optima; (2) forming groups of objects with interactive brushing to create patterned missing values in MDS loss functions; (3) optimizing MDS loss functions for large numbers of objects relative to a small set of anchor points (“external unfolding”); and (4) a non-metric version of classical MDS.We show applications to the mapping of computer usage data, to the dimension reduction of marketing segmentation data, to the layout of mathematical graphs and social networks, and finally to the spatial reconstruction of molecules. 相似文献