全文获取类型
收费全文 | 677篇 |
免费 | 58篇 |
国内免费 | 41篇 |
专业分类
化学 | 26篇 |
晶体学 | 1篇 |
力学 | 4篇 |
综合类 | 10篇 |
数学 | 180篇 |
物理学 | 555篇 |
出版年
2023年 | 1篇 |
2022年 | 18篇 |
2021年 | 19篇 |
2020年 | 10篇 |
2019年 | 13篇 |
2018年 | 10篇 |
2017年 | 17篇 |
2016年 | 20篇 |
2015年 | 22篇 |
2014年 | 28篇 |
2013年 | 38篇 |
2012年 | 19篇 |
2011年 | 33篇 |
2010年 | 26篇 |
2009年 | 42篇 |
2008年 | 49篇 |
2007年 | 49篇 |
2006年 | 45篇 |
2005年 | 47篇 |
2004年 | 41篇 |
2003年 | 32篇 |
2002年 | 31篇 |
2001年 | 32篇 |
2000年 | 28篇 |
1999年 | 20篇 |
1998年 | 34篇 |
1997年 | 18篇 |
1996年 | 8篇 |
1995年 | 2篇 |
1994年 | 6篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1981年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有776条查询结果,搜索用时 15 毫秒
81.
Samples from a high-dimensional first-order auto-regressive process generated by an independently and identically distributed random innovation sequence are observed by a sender which can communicate only finitely many bits per unit time to a receiver. The receiver seeks to form an estimate of the process value at every time instant in real-time. We consider a time-slotted communication model in a slow-sampling regime where multiple communication slots occur between two sampling instants. We propose a successive update scheme which uses communication between sampling instants to refine estimates of the latest sample and study the following question: Is it better to collect communication of multiple slots to send better refined estimates, making the receiver wait more for every refinement, or to be fast but loose and send new information in every communication opportunity? We show that the fast but loose successive update scheme with ideal spherical codes is universally optimal asymptotically for a large dimension. However, most practical quantization codes for fixed dimensions do not meet the ideal performance required for this optimality, and they typically will have a bias in the form of a fixed additive error. Interestingly, our analysis shows that the fast but loose scheme is not an optimal choice in the presence of such errors, and a judiciously chosen frequency of updates outperforms it. 相似文献
82.
背景主色的确定是迷彩伪装的关键问题,针对现有提取方法的不足,提出一种基于八叉树颜色量化和链表统计的背景主色提取算法.首先对图像进行八叉树颜色量化,然后统计量化后图像的颜色,并用链表存储,最后依据人眼视觉特性和相应准则确定背景主色.该算法可以对多 幅图像进行处理且运算时间较短.实验表明这种方法能够满足迷彩伪装颜色确定的要... 相似文献
83.
84.
Let G be a real reductive Lie group, let H=TA be the identity component of a Cartan subgroup, and let h be the corresponding Cartan subalgebra. This leads to a parabolic subgroup of G whose identity component is MAN. The unitary G-representations induced by MAN are known as the H -series. We study symplectic geometry of G×h and apply geometric quantization to construct unitary G-representations by partially harmonic forms. They are direct integrals of the H-series, indexed by the image of the moment map. We also perform symplectic reduction and symplectic induction, and consider their analogues in representation theory via geometric quantization. 相似文献
85.
In this work, we present a rather simple method to study the Casimir effect on a spherical shell for a massless scalar field with Dirichlet boundary condition by applying the indefinite metric field (Krein) quantization technique. In this technique, the field operators are constructed from both negative and positive norm states. Having understood that negative norm states are un-physical, they are only used as a mathematical tool for renormalizing the theory and then one can get rid of them by imposing some proper physical conditions. 相似文献
86.
The bulk quantization method is used for regularizing a conventional four dimensional theory of massless fermions coupled to an external non‐Abelian gauge field and for subsequently evaluating the associated Ward identity. As a result one obtains the well‐known chiral anomaly. 相似文献
87.
88.
An adaptive tracking design strategy based on quantized state feedback is developed for uncertain nonholonomic mobile robots with unknown wheel slippage effects. All state variables and control torques are assumed to be quantized by the state and input quantizers, respectively, in a network control environment. Thus, the quantized state feedback information is only available for the tracking control design. An approximation-based adaptive controller using quantized states is recursively designed to ensure the robust adaptive tracking against unknown wheel slippage effects where the quantized-states-based adaptive mechanism is derived to compensate for unknown wheel slippage effects, system nonlinearities, and quantization errors. The boundedness of the quantization errors and estimated parameters in the closed-loop system is analyzed by presenting some theoretical lemmas. Based on these lemmas, we prove the uniform ultimate boundedness of closed-loop signals and the convergence of the trajectory tracking error in the presence of wheel slippage effects. Simulations verify the effectiveness of the resulting tracking scheme. 相似文献
89.
90.