全文获取类型
收费全文 | 3174篇 |
免费 | 401篇 |
国内免费 | 283篇 |
专业分类
化学 | 253篇 |
晶体学 | 7篇 |
力学 | 442篇 |
综合类 | 60篇 |
数学 | 2027篇 |
物理学 | 1069篇 |
出版年
2024年 | 4篇 |
2023年 | 39篇 |
2022年 | 46篇 |
2021年 | 62篇 |
2020年 | 71篇 |
2019年 | 86篇 |
2018年 | 83篇 |
2017年 | 88篇 |
2016年 | 114篇 |
2015年 | 99篇 |
2014年 | 209篇 |
2013年 | 278篇 |
2012年 | 154篇 |
2011年 | 215篇 |
2010年 | 172篇 |
2009年 | 215篇 |
2008年 | 218篇 |
2007年 | 211篇 |
2006年 | 189篇 |
2005年 | 176篇 |
2004年 | 150篇 |
2003年 | 128篇 |
2002年 | 130篇 |
2001年 | 104篇 |
2000年 | 76篇 |
1999年 | 94篇 |
1998年 | 78篇 |
1997年 | 54篇 |
1996年 | 60篇 |
1995年 | 42篇 |
1994年 | 18篇 |
1993年 | 28篇 |
1992年 | 27篇 |
1991年 | 23篇 |
1990年 | 14篇 |
1989年 | 12篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 13篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有3858条查询结果,搜索用时 31 毫秒
61.
各向异性非线性固体力学的规范空间理论 总被引:8,自引:0,他引:8
本文在弹性规范空间概念基础上,利用非平衡态热力学理论,证明了各向异性固体力学非线性问题规范空间场以及不可逆过程本征解的存在。损伤对结构刚度的弱化效应和损伤诱发各向异性效应分别反映在本征弹性和相应的模态向量中。在简正坐标中考察各向异性体变形时,材料的行为以六个普通的粘弹性Maxwell方程描述,总的响应由模态叠加得到。以此为基础给出的非线性本构方程具有坐标转换不变性,最后给出了二个具体的算例。 相似文献
62.
水平地震时斜面水坝受到的非线性动水压力的全过程的解析解 总被引:1,自引:0,他引:1
本文给出在非线性Rayleigh阻尼作用下,由水平地震激发的水库内动水压力变化全过程的解析解:在激发初期其幅值较小,可用小参数法使控制方程线性化,从而求得各阶渐近控制方程的解析解;当动水压力的幅值增大到小参数展开不适用时,用van derpol法求得非线性控制方程的渐近解,从而显示了动水压力的幅值从有序变化到发生突然跳跃的多值性的非线性本质。 相似文献
63.
In previous studies on plasma-particle interaction, as far as we know, the rf plasma flow and temperature fields are all simulated
by the non-self-consistent one-dimensional electromagnetic (1-D EM) field model. In the present paper, the complete self-consistent
two-dimensional electromagnetic (2-D EM) field model incorporating the axial Lorentz force component, which is neglected in
the 1-D model, is firstly adopted to calculate the aluminium particle trajectory and thermal history in atmospheric rf Ar
plasma with the particle evaporation effect included. The crucial effect of reverse flow within the coil region on the particle
trajectory is discovered and the results show that the 2-D EM field model must be adopted instead of the 1-D model when the
plasma-particle interaction is studied. The effect of carrier gas flux on the particle movement and heating are also studied,
resulting in some useful conclusions for both plasma theory and application.
recommended by Prof. Wu Chengkang
The project supported by the National Natural Science Foundation of China 相似文献
64.
横向磁场激励下铁磁梁式板的混沌运动分析 总被引:9,自引:0,他引:9
在磁体力分布的磁弹性理论模型和磁场准静态假定模式基础上,对于处在周期时变磁场 中的不可移简支铁磁梁式板非线性磁弹性动力特性进行定性与定量分析.首先利用磁场的摄 动技术和结构变形的模态法,导出了关于模态坐标的非线性动力方程;然后利用Melnikov方 法,从理论上给出这一磁弹性动力系统可能出现混沌运动的必要条件及参数范围;最后采用变 步长Runge-Kutta数值积分方法对其磁弹性相互作用的混沌现象进行了定量搜索与模拟,并 利用其轨迹的Poincare截面图与Liapunov指数加以判断.结果表明磁弹性简支梁式板在横 向周期时变磁场中存在混沌吸引子,且在机械阻尼很小时其混沌吸引子表现出稠的特性. 相似文献
65.
Previous studies suggesting that people predict chaotic sequences better than chance have not discriminated between sensitivity to nonlinear determinism and facilitation using autocorrelation. Since prediction accuracy declines with increases in the look-ahead window in both cases, a decline in prediction accuracy does not imply chaos sensitivity. To overcome this problem, phase-randomized surrogate time series are used as a control. Such series have the same linear properties as the original chaotic sequence but contain no nonlinear determinism, i.e. chaos. In the experimental task, using a chaotic Hénon attractor, participants viewed the previous eight days temperatures and then predicted temperatures for the next four days, over 120 trials. The control group experienced a sample from a corresponding phase-randomized surrogate series. Both time series were linearly transformed to provide a realistic temperature range. A transformation of the correlation between observed and predicted values decreased over days for the chaotic time series, but remained constant and high for the surrogate series. The interaction between the days and series factors was statistically significant, suggesting that people are sensitive to chaos, even when the autocorrelation functions and power spectra of the control and experimental series are identical. Implications for the psychological assessment of individual differences in human prediction are discussed. 相似文献
66.
67.
Y. -G. Oh N. Sreenath P. S. Krishnaprasad J. E. Marsden 《Journal of Dynamics and Differential Equations》1989,1(3):269-298
We give a complete bifurcation and stability analysis for the relative equilibria of the dynamics of three coupled planar rigid bodies. We also use the equivariant Weinstein-Moser theorem to show the existence of two periodic orbits distinguished by symmetry type near the stable equilibrium. Finally we prove that the dynamics is chaotic in the sense of Poincaré-Birkhoff-Smale horseshoes using the version of Melnikov's method suitable for systems with symmetry due to Holmes and Marsden. 相似文献
68.
We consider a weakly dissipative quasilinear system of PDEs, governingthe unsteady one-dimensional motion of a relaxing gas, and investigatethe effects ofhigher order terms and the source term, present in the differentialsystem, on the wave motion associated with it. The undisturbed stateof the medium, which is assumed to be uniform and at restadmits mixed nonlinearity, i.e., the quadratic nonlinearity parameter inherent in the system changes sign depending on the basestate. The method of multiple scales is employed to determine theevolution equation governing small perturbations to the state where is of O(), and the effects of nonlinearity arenoticeable over times of order O(–2). 相似文献
69.
70.
半刚性钢框架的内力分析 总被引:21,自引:1,他引:21
采用二阶非线性分析方法分析和设计半刚性钢框架,包括连接的柔性以及构件的几何非线性的影响,提出了半刚性钢框架中梁柱单元刚度矩阵和半刚性梁的单元刚度矩阵;推导了半刚性梁在集中荷载,均布荷载,线性荷载作用下的固端弯矩的求解公式;连接的柔性对无支撑框架的侧移有很大的影响,设计时通过变化连接的刚度以平衡梁的跨中和端弯矩。 相似文献