全文获取类型
收费全文 | 35547篇 |
免费 | 4426篇 |
国内免费 | 2307篇 |
专业分类
电工技术 | 2421篇 |
综合类 | 5496篇 |
化学工业 | 1894篇 |
金属工艺 | 2416篇 |
机械仪表 | 4951篇 |
建筑科学 | 5690篇 |
矿业工程 | 1166篇 |
能源动力 | 1067篇 |
轻工业 | 578篇 |
水利工程 | 1727篇 |
石油天然气 | 1405篇 |
武器工业 | 612篇 |
无线电 | 1792篇 |
一般工业技术 | 7050篇 |
冶金工业 | 780篇 |
原子能技术 | 194篇 |
自动化技术 | 3041篇 |
出版年
2024年 | 136篇 |
2023年 | 395篇 |
2022年 | 681篇 |
2021年 | 875篇 |
2020年 | 1061篇 |
2019年 | 924篇 |
2018年 | 950篇 |
2017年 | 1254篇 |
2016年 | 1397篇 |
2015年 | 1524篇 |
2014年 | 2247篇 |
2013年 | 2393篇 |
2012年 | 2994篇 |
2011年 | 2956篇 |
2010年 | 2246篇 |
2009年 | 2338篇 |
2008年 | 2154篇 |
2007年 | 2717篇 |
2006年 | 2364篇 |
2005年 | 1819篇 |
2004年 | 1468篇 |
2003年 | 1200篇 |
2002年 | 1002篇 |
2001年 | 860篇 |
2000年 | 764篇 |
1999年 | 646篇 |
1998年 | 511篇 |
1997年 | 502篇 |
1996年 | 429篇 |
1995年 | 332篇 |
1994年 | 257篇 |
1993年 | 201篇 |
1992年 | 162篇 |
1991年 | 115篇 |
1990年 | 103篇 |
1989年 | 75篇 |
1988年 | 65篇 |
1987年 | 38篇 |
1986年 | 24篇 |
1985年 | 14篇 |
1984年 | 20篇 |
1983年 | 7篇 |
1982年 | 12篇 |
1981年 | 9篇 |
1980年 | 16篇 |
1979年 | 10篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1959年 | 2篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
81.
Comparison of finite element reliability methods 总被引:7,自引:0,他引:7
The spectral stochastic finite element method (SSFEM) aims at constructing a probabilistic representation of the response of a mechanical system, whose material properties are random fields. The response quantities, e.g. the nodal displacements, are represented by a polynomial series expansion in terms of standard normal random variables. This expansion is usually post-processed to obtain the second-order statistical moments of the response quantities. However, in the literature, the SSFEM has also been suggested as a method for reliability analysis. No careful examination of this potential has been made yet. In this paper, the SSFEM is considered in conjunction with the first-order reliability method (FORM) and with importance sampling for finite element reliability analysis. This approach is compared with the direct coupling of a FORM reliability code and a finite element code. The two procedures are applied to the reliability analysis of the settlement of a foundation lying on a randomly heterogeneous soil layer. The results are used to make a comprehensive comparison of the two methods in terms of their relative accuracies and efficiencies. 相似文献
82.
M. M. Rashid 《International journal for numerical methods in engineering》2002,55(4):431-450
A computational procedure for remapping material state information from one finite element mesh to another is described. The procedure is useful in connection with evolving meshes for inelastic problems, as for example occur in the context of fracture simulation and adaptive mesh refinement. The proposed method is based on weak enforcement of equality between corresponding fields on the two meshes, where piecewise‐constant fields on both meshes are generalized from the quadrature‐point values. The essential algorithmic problem is that of calculating the volume partition of an arbitrary convex region with respect to a covering set of disjoint convex regions. Instead of geometrically resolving the associated intersections, the problem is herein approximated by a constrained optimization problem, which may be readily and efficiently solved computationally. This formulation is a main contribution of the paper. Computational examples are given that illustrate the effectiveness of the proposed procedure. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
83.
Charbel Farhat Ulrich Hetmaniuk 《International journal for numerical methods in engineering》2002,54(9):1309-1332
We present a fictitious domain decomposition method for the fast solution of high‐frequency acoustic scattering problems characterized by a partially axisymmetric sound‐soft scatterer. We apply this method to the solution of various mockup submarine problems, and highlight its computational advantages and intrinsic parallelism. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
84.
铝电解槽磁流体稳定性有限元分析 总被引:2,自引:0,他引:2
本文采用有限元法求解分层磁流体小扰动方程系统特征值,研究铝电解槽稳定性。研究结果表明,在没有电磁力时,铝液表面波动(内波)是稳定的。存在电磁力时,它会激发铝液表面波动的某些低频长波分量不稳定性,高频短波不受影响。被激发的不稳定波动频率和扰动增长率与电流密度,磁感应强度垂直分量,铝电解槽长宽比,电解质和铝液的密度差,厚度等因素密切相关。减少电流密度,磁感应强度,增加电极距离和铝液厚度可以提高铝电解槽的稳定性。这对铝电解槽优化设计和在线控制有重要意义。 相似文献
85.
A. V. Lyamin S. W. Sloan 《International journal for numerical methods in engineering》2002,55(5):573-611
This paper describes a new formulation, based on linear finite elements and non‐linear programming, for computing rigorous lower bounds in 1, 2 and 3 dimensions. The resulting optimization problem is typically very large and highly sparse and is solved using a fast quasi‐Newton method whose iteration count is largely independent of the mesh refinement. For two‐dimensional applications, the new formulation is shown to be vastly superior to an equivalent formulation that is based on a linearized yield surface and linear programming. Although it has been developed primarily for geotechnical applications, the method can be used for a wide range of plasticity problems including those with inhomogeneous materials, complex loading, and complicated geometry. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
86.
87.
88.
潜孔锤冲击作用下土体变形的有限元分析 总被引:1,自引:0,他引:1
潜孔锤冲击挤密钻进过程中周围土体的变形机理是一个高度非线性问题。针对潜孔锤在土中的面-面接触问题,运用Drucker-Prager屈服准则为判据,将土体视为DP材料,通过钻具与土之间的接触及施加冲击载荷来模拟钻进过程,从而建立了潜孔锤在土中冲击挤密钻进的有限元模型。利用非线性瞬态动力学有限元分析手段,对钻进过程中冲击力对土的作用加以研究,分析了钻具周围土体的应力、应变以及钻具与土体的摩擦情况。结果表明,在冲击载荷作用下,锥形钻头前端土体应力集中,并形成应力泡,冲击功主要用于竖向压缩土体,而水平方向的挤压作用相对较小,摩擦应力在钻头锥面附近出现峰值,是影响钻进速度的主要原因之一。 相似文献
89.
I. N. Ishchuk 《Measurement Techniques》2007,50(10):1081-1086
A three-dimensional solution of the direct problem of heat conduction when a linear pulsed heat source acts in the plane of
contact of two semibounded bodies is presented. The solution is obtained by the method of finite differences. An example of
the modeling is considered.
__________
Translated from Izmeritel’naya Tekhnika, No. 10, pp. 42–45, October, 2007. 相似文献
90.