全文获取类型
收费全文 | 1375篇 |
免费 | 151篇 |
国内免费 | 71篇 |
专业分类
化学 | 72篇 |
晶体学 | 1篇 |
力学 | 421篇 |
综合类 | 16篇 |
数学 | 814篇 |
物理学 | 273篇 |
出版年
2024年 | 2篇 |
2023年 | 12篇 |
2022年 | 19篇 |
2021年 | 29篇 |
2020年 | 39篇 |
2019年 | 27篇 |
2018年 | 29篇 |
2017年 | 58篇 |
2016年 | 65篇 |
2015年 | 46篇 |
2014年 | 53篇 |
2013年 | 106篇 |
2012年 | 84篇 |
2011年 | 82篇 |
2010年 | 73篇 |
2009年 | 65篇 |
2008年 | 78篇 |
2007年 | 70篇 |
2006年 | 88篇 |
2005年 | 74篇 |
2004年 | 64篇 |
2003年 | 54篇 |
2002年 | 43篇 |
2001年 | 31篇 |
2000年 | 26篇 |
1999年 | 29篇 |
1998年 | 27篇 |
1997年 | 32篇 |
1996年 | 23篇 |
1995年 | 16篇 |
1994年 | 12篇 |
1993年 | 19篇 |
1992年 | 23篇 |
1991年 | 18篇 |
1990年 | 15篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 10篇 |
1984年 | 4篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1957年 | 1篇 |
排序方式: 共有1597条查询结果,搜索用时 750 毫秒
61.
提出了基于稳定性准则的延迟非线性反馈控制混沌的方法,即SC延迟非线性反馈控制法. 通过对混沌系统的适当分离,得到一个特殊的非线性函数,并利用混沌输出信号与其延迟信号的非线性函数的差,构造了连续反馈输入干扰,以控制混沌轨到某一期望的不稳周期轨上. 该方法继承了延迟反馈控制方法的优点,实现了自-控制过程. 另外由于该方法基于线性系统的稳定性准则,保证了控制的有效性. 控制过程可随时开始,具有简便、灵活性. 给出耦合Duffing振子的例子,数值模拟结果显示了SC延迟反馈方法控制的有效性.
关键词:
稳定性准则
混沌控制
延迟反馈
干扰 相似文献
62.
63.
研究两个对称非线性耦合混沌系统的同步问题.通过对系统线性项与非线性项的适当分离, 构造一个特殊的非线性耦合项,发现在耦合强度α=05附近的某一区域里存在稳定的 混沌同步现象.提供判断同步误差稳定性的方程,利用线性系统的稳定性分析准则和条件Lya punov指数来检验同步状态的稳定性.新方法适用于连续时间系统的混沌同步,也适用于具有 两个(或多于两个)正Lyapunov指数的超混沌系统.以Lorenz系统,超混沌Rssler 系统作 为算例,数值模拟结果证实所提新方法的有效性.
关键词:
混沌
同步
非线性耦合
稳定性准则
超混沌 相似文献
64.
对薄层柱壳爆炸膨胀断裂过程的研究 总被引:8,自引:2,他引:8
本文提出了一个用于描述动态破坏发展过程的损伤度函数。从这个损伤度函数出发,把材料特征性方程取为强化粘塑性本构方程形式,导出了薄层柱壳爆炸膨胀运动在两种近似下(恒定膨胀速度近似合恒定应变速率近似)断裂判据的解析表达式。结果分析表明,在上述条件下,存在着一个动态断裂“塑性峰”,在这个峰值条件的应变率下,柱壳出现贯穿断裂时刻的应变最大。以软钢为算例,本断裂判据可以比较好地解释Иванов和陈大年等给出的实验结果。这时,动态断裂“塑性峰”对应的应变率为4×104 s-1,相应的应变约为60%~80%。 相似文献
65.
Joshua Lee Yuheng Bu Prasanna Sattigeri Rameswar Panda Gregory W. Wornell Leonid Karlinsky Rogerio Schmidt Feris 《Entropy (Basel, Switzerland)》2022,24(4)
As machine learning algorithms grow in popularity and diversify to many industries, ethical and legal concerns regarding their fairness have become increasingly relevant. We explore the problem of algorithmic fairness, taking an information–theoretic view. The maximal correlation framework is introduced for expressing fairness constraints and is shown to be capable of being used to derive regularizers that enforce independence and separation-based fairness criteria, which admit optimization algorithms for both discrete and continuous variables that are more computationally efficient than existing algorithms. We show that these algorithms provide smooth performance–fairness tradeoff curves and perform competitively with state-of-the-art methods on both discrete datasets (COMPAS, Adult) and continuous datasets (Communities and Crimes). 相似文献
66.
In this paper, the hinged road-mat construction is modeled as a cable structure, and based on the equivalent cable theory the sinkage of the roadway is evaluated. Neglecting details of the interaction between tires and road mats, works caused by the traction, resistance, and drawbar pulling are defined to build a new work criterion to evaluate the mobility of vehicles on the hinged road mats. Mobility diagrams, related to coefficient of adhesion, terrain deformation, beam width, and fastening force, are developed to evaluate the locomotion of vehicles and further guide the design of hinged road mats. The presented method compares well with the field terramechanical experiments of the hinged road mats, thus verifying the validity of equivalent cable modeling and work criterion for hinged road mats. 相似文献
67.
《Acta Mechanica Solida Sinica》2011,(Z1):22-33
The aim of this study is to describe the main behavior of cement-based materials under large compression state based on the recent experimental research. In this paper, the strainstress relations are firstly analyzed and confining pressure state is regarded as low/medium/high state. A generalized cup modeling is introduced by a coupled deviatoric shearing, pore collapse and damage mechanism within thermodynamic framework. A series of numerical simulations are performed for the considered cement paste and concrete. Comparisons between numerical predictions and experimental results show that the proposed model is able to describe the main features of mechanical behavior under large range of compression state. 相似文献
68.
Takesi Hayakawa 《Annals of the Institute of Statistical Mathematics》2002,54(4):918-933
Let
i
be an i-tb population with a probability density function f(· |
i
) with one dimensional unknown parameter
i
= 1, 2, ... , k. Let n
i sample be drawn from each
i
. The likelihood ratio criteria
j|(j–1) for testing hypothesis that the first j parameters are equal against alternative hypothesis that the first (j – 1) parameters are equal and the j-th parameter is different with the previous ones are defined, j = 2, 3, ... , k. The paper shows the asymptotic independence of
j|(j–1)'s up to the order 1/n under a hypothesis of equality of k parameters, where n is a number of total samples. 相似文献
69.
Piotr Hajlasz 《Proceedings of the American Mathematical Society》1999,127(2):417-423
If is an open set with the sufficiently regular boundary, then the Hardy inequality holds for and , where . The main result of the paper is a pointwise inequality , where on the right hand side there is a kind of maximal function. The pointwise inequality combined with the Hardy-Littlewood maximal theorem implies the Hardy inequality. This generalizes some recent results of Lewis and Wannebo.
70.
Hamparsum Bozdogan Stanley L. Sclove 《Annals of the Institute of Statistical Mathematics》1984,36(1):163-180
Summary Multi-sample cluster analysis, the problem of grouping samples, is studied from an information-theoretic viewpoint via Akaike's
Information Criterion (AIC). This criterion combines the maximum value of the likelihood with the number of parameters used
in achieving that value. The multi-sample cluster problem is defined, and AIC is developed for this problem. The form of AIC
is derived in both the multivariate analysis of variance (MANOVA) model and in the multivariate model with varying mean vectors
and variance-covariance matrices. Numerical examples are presented for AIC and another criterion calledw-square. The results demonstrate the utility of AIC in identifying the best clustering alternatives.
This research was supported by Office of Naval Research Contract N00014-80-C-0408, Task NR042-443 and Army Research Office
Contract DAAG 29-82-K-0155, at the University of Illinois at Chicago. 相似文献