全文获取类型
收费全文 | 7461篇 |
免费 | 887篇 |
国内免费 | 854篇 |
专业分类
化学 | 513篇 |
晶体学 | 4篇 |
力学 | 668篇 |
综合类 | 325篇 |
数学 | 6555篇 |
物理学 | 1137篇 |
出版年
2024年 | 34篇 |
2023年 | 88篇 |
2022年 | 112篇 |
2021年 | 134篇 |
2020年 | 102篇 |
2019年 | 134篇 |
2018年 | 74篇 |
2017年 | 152篇 |
2016年 | 162篇 |
2015年 | 182篇 |
2014年 | 405篇 |
2013年 | 345篇 |
2012年 | 372篇 |
2011年 | 435篇 |
2010年 | 453篇 |
2009年 | 512篇 |
2008年 | 461篇 |
2007年 | 457篇 |
2006年 | 395篇 |
2005年 | 484篇 |
2004年 | 478篇 |
2003年 | 382篇 |
2002年 | 318篇 |
2001年 | 336篇 |
2000年 | 288篇 |
1999年 | 228篇 |
1998年 | 225篇 |
1997年 | 251篇 |
1996年 | 195篇 |
1995年 | 192篇 |
1994年 | 147篇 |
1993年 | 135篇 |
1992年 | 126篇 |
1991年 | 137篇 |
1990年 | 134篇 |
1989年 | 106篇 |
1988年 | 13篇 |
1987年 | 7篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有9202条查询结果,搜索用时 15 毫秒
91.
激光捷联惯组的双轴位置转台标定仿真 总被引:2,自引:4,他引:2
研究了利用双轴位置转台标定时,水平基准误差和北向基准误差对激光捷联惯组(LSIMU)标定精度的影响。首先建立了LSIMU标定模型和生成惯性器件信息的仿真算法,接着设计了LSIMU标定方案和数据处理方法,最后对LSIMU标定进行仿真和分析。仿真结果表明:水平基准误差为0.4’时,加速度计标定误差将达到116×10^-6;当北向基准误差大于5°时,陀螺标定误差将超过0.0001。 相似文献
92.
93.
本文利用单个平片裂纹的基本解,将三维有限体中的平片裂纹问题,归为解一组超奇异积分方程,然后使用主部分析方法,对这组方程的求解作了理论分析,其结果在本文的第Ⅰ部分给出,关于这组方程的数值法求解,则给出于本文的第Ⅱ部分。 相似文献
94.
ADAPTIVE MESHLESS METHOD BASED ON LOCAL FIT TECHNOLOGY 总被引:1,自引:0,他引:1
LouLuliang ZengPan 《Acta Mechanica Solida Sinica》2005,18(2):164-172
An h-adaptive meshless method is proposed in this paper. The error estimation is based on local fit technology, usually confined to Voronoi Cells. The error is achieved by comparison of the computational results with smoothed ones, which are projected with Taylor series. Voronoi Cells are introduced not only for integration of potential energy but also for guidance of refinement.New nodes are placed within those cells with high estimated error. At the end of the paper, two numerical examples with severe stress gradient are analyzed. Through adaptive analysis accurate results are obtained at critical subdomains, which validates the efficiency of the method. 相似文献
95.
三维非规则非均匀边界元网格的简便的高精度算法 总被引:1,自引:0,他引:1
对三维直接边界元中一阶奇异积分、一阶近奇异积分以及非奇异积分进行统一处理,给出了一种提高积分计算精度的简便有效的方法,对非规则非均匀边界元网格可获得比一般方法高得多的计算精度,非常适合边界形状比较复杂的三维实际问题的边界元分析. 相似文献
96.
97.
弹性地基上四边自由的各向异性矩形板 总被引:4,自引:2,他引:4
通过叠加法得到了弹性地基上的各向异性矩形板的一般解。每个叠加解被展成重傅立叶级数,其自身或其一阶导数在边界上的值被展成单傅立叶级数。利用控制微分方程和一些边界条件,每个叠加解被简化成用边界值的级数的系数表示的傅立叶级数。文后给出了弹性地基上的方板的挠曲面图。 相似文献
98.
99.
ChenJnnming HuangYuying 《Acta Mechanica Solida Sinica》2003,16(3):210-219
Based on the motion differential equations of vibration and acoustic coupling system for thin elastic spherical shell with an elastic plate attached to its internal surface, in which Dirac-δ functions are employed to introduce the moments and forces applied by the attachment on the surface of shell, by means of expanding field quantities as Legendre series, a semi-analytic solution is derived for the vibration and acoustic radiation from a submerged stiffened spherical shell with a deck-type internal plate, which has a satisfactory computational effectiveness and precision for an arbitrary frequency range. It is easy to analyze the effect of the internal plate on the acoustic radiation field by using the formulas obtained by the method proposed. It is concluded that the internal plate can significantly change the mechanical and acoustic characteristics of shell, and give the coupling system a very rich resonance frequency spectrum. Moreover, the method can be used to study the acoustic radiation mechanism in similar structures as the one studied here. 相似文献
100.
A great number of studies have shown the complex nonlinear dynamics of mechanical systems with repeated normal impacts. An
oblique frictional impact introduces even more complicated dynamics such as stick-slip motions to those systems. Hence, the
dynamics of oblique vibro-impacting systems with possible sliding motion is an open problem. Based on a hybrid analysis of
vibro-impact dynamics, kinematics and complementary conditions, a piecewise analysis method is developed in the paper to describe
the sliding motion during an oblique impact. Thereby, a parametrically excited planar pendulum between two parallel rigid
walls is studied as an illustrative example. The example, together with the corresponding numerical results, shows that the
sliding impacts occur in such a system with a set of properly selected parameters.
The project supported by the National Natural Science Foundation of China (59905010) and by the Scientific Research Foundation
for the Returned Overseas Chinese Scholars, Ministry of Education, China 相似文献