全文获取类型
收费全文 | 10332篇 |
免费 | 1439篇 |
国内免费 | 394篇 |
专业分类
化学 | 856篇 |
晶体学 | 16篇 |
力学 | 1305篇 |
综合类 | 359篇 |
数学 | 6114篇 |
物理学 | 3515篇 |
出版年
2024年 | 24篇 |
2023年 | 97篇 |
2022年 | 318篇 |
2021年 | 292篇 |
2020年 | 207篇 |
2019年 | 235篇 |
2018年 | 251篇 |
2017年 | 377篇 |
2016年 | 493篇 |
2015年 | 331篇 |
2014年 | 592篇 |
2013年 | 687篇 |
2012年 | 567篇 |
2011年 | 623篇 |
2010年 | 484篇 |
2009年 | 645篇 |
2008年 | 667篇 |
2007年 | 700篇 |
2006年 | 563篇 |
2005年 | 511篇 |
2004年 | 438篇 |
2003年 | 388篇 |
2002年 | 367篇 |
2001年 | 316篇 |
2000年 | 278篇 |
1999年 | 257篇 |
1998年 | 229篇 |
1997年 | 207篇 |
1996年 | 155篇 |
1995年 | 134篇 |
1994年 | 96篇 |
1993年 | 119篇 |
1992年 | 93篇 |
1991年 | 60篇 |
1990年 | 57篇 |
1989年 | 35篇 |
1988年 | 41篇 |
1987年 | 32篇 |
1986年 | 41篇 |
1985年 | 40篇 |
1984年 | 33篇 |
1983年 | 10篇 |
1982年 | 22篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1959年 | 5篇 |
1957年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
P. Z. Lugovoi V. F. Meish B. P. Rybakin G. V. Sekrieru 《International Applied Mechanics》2006,42(5):536-540
Dynamic problems for cylindrical shells reinforced with discrete ribs are examined. A numerical algorithm based on Richardson
extrapolation is developed. Specific problems are solved, and the results are analyzed
__________
Translated from Prikladnaya Mekhanika, Vol. 42, No. 5, pp. 50–56, May 2006. 相似文献
992.
This paper investigates multiple modeling choices for analyzing the rich and complex dynamics of high-speed milling processes.
Various models are introduced to capture the effects of asymmetric structural modes and the influence of nonlinear regeneration
in a discontinuous cutting force model. Stability is determined from the development of a dynamic map for the resulting variational
system. The general case of asymmetric structural elements is investigated with a fixed frame and rotating frame model to
show differences in the predicted unstable regions due to parametric excitation. Analytical and numerical investigations are
confirmed through a series of experimental cutting tests. The principal results are additional unstable regions, hysteresis
in the bifurcation diagrams, and the presence of coexisting periodic and quasiperiodic attractors which is confirmed through
experimentation. 相似文献
993.
利用一维扩展过程的奇点理论并结合能量包络的随机平均法,考查“隐藏在余维2分岔点之后”的同宿分岔系统受参激白噪声影响的分岔行为。 相似文献
994.
A parametrically excited Rayleigh–Liénard oscillator is investigatedby an asymptotic perturbation method based on Fourier expansion and timerescaling. Two coupled equations for the amplitude and the phase ofsolutions are derived and the stability of steady-state periodic solutionsas well as parametric excitation-response and frequency-response curvesare determined. Comparison with the parametrically excited Liénardoscillator is performed and analytic approximate solutions are checkedusing numerical integration. Dulac's criterion, thePoincaré–Bendixson theorem, and energy considerations are used in order to study the existence and characteristics of limit cycles of the twocoupled equations. A limit cycle corresponds to a modulated motion forthe Rayleigh–Liénard oscillator. Modulated motion can be also obtainedfor very low values of the parametric excitation, and in this case, anapproximate analytic solution is easily constructed. If the parametricexcitation is increased, an infinite-period bifurcation is observed because the modulation period lengthens and becomes infinite, while themodulation amplitude remains finite and suddenly the attractor settlesdown into a periodic motion. Floquet's theory is used to evaluatethe stability of the periodic solutions, and in certain cases,symmetry-breaking bifurcations are predicted. Numerical simulationsconfirm this scenario and detect chaos and unbounded motions in theinstability regions of the periodic solutions. 相似文献
995.
996.
V. T. Golovchan 《International Applied Mechanics》2006,42(1):84-89
An algorithm for solving plane boundary-value problems of elasticity for a rectangular domain is expounded. The algorithm
is based on a complex-valued representation of the general solution to the differential equations of the plane problem and
on the use of Lagrange polynomials to satisfy the boundary conditions. The algorithm can quite easily be implemented in a
computer program. This is probably the simplest way of solving boundary-value problems of this class
__________
Translated from Prikladnaya Mekhanika, Vol. 42, No. 1, pp. 97–102, January 2006. 相似文献
997.
998.
参数激励与强迫激励联合作用下非线性振动系统的余维2退化分叉 总被引:4,自引:0,他引:4
在本文里我们首先研究了具有Z_2-对称性的范式理论和退化向量场的普适开折理论。然后利用上述理论研究了参数激励与强迫激励联合作用下非线性振动系统的余维2退化分叉,从而解决了当解具有两个零特征值时解的稳定性问题。最后利用Melnikov方法求出了参数平面上的同宿分叉曲线,讨论了全局分叉的存在性。 相似文献
999.
捷联惯性导航中一种算法的推证 总被引:9,自引:0,他引:9
捷联惯性导航系统中,常常用到解算四元数矩阵微分方程的问题。为此给出了解四元数矩阵微分方程的一个强有力的算式,并给出了详细的数学推导和证明。 相似文献
1000.
基于结构动力修改的桩基检测方法 总被引:1,自引:0,他引:1
采用结构动力修改技术研究桩身损伤检测,将其转化为在一定约束条件下拟合桩顶频响函数的优化问题。用遗传算法加以求解。文中给出的数值模拟试验和工程应用实例,显示该方法能在较大范围内可靠地反演出桩身横截面积、桩长、波速等参数,达到检测桩身缺陷的目的,实现测试和分析一体化,使桩基检测易于进行并且结果实用可靠。 相似文献