首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   452篇
  免费   46篇
  国内免费   25篇
化学   74篇
力学   68篇
综合类   6篇
数学   211篇
物理学   164篇
  2023年   6篇
  2022年   18篇
  2021年   26篇
  2020年   17篇
  2019年   25篇
  2018年   20篇
  2017年   33篇
  2016年   23篇
  2015年   32篇
  2014年   50篇
  2013年   46篇
  2012年   37篇
  2011年   38篇
  2010年   27篇
  2009年   23篇
  2008年   16篇
  2007年   15篇
  2006年   17篇
  2005年   4篇
  2004年   2篇
  2003年   4篇
  2002年   1篇
  2001年   9篇
  2000年   6篇
  1999年   11篇
  1998年   7篇
  1997年   2篇
  1996年   2篇
  1995年   1篇
  1992年   3篇
  1991年   1篇
  1985年   1篇
排序方式: 共有523条查询结果,搜索用时 156 毫秒
1.
Let A be an infinite dimensional stably finite unital simple separable C*-algebra.Let B■A be a stably(centrally)large subalgebra in A such that B is m-almost divisible(m-almost divisible,weakly(m,n)-divisible).Then A is 2(m+1)-almost divisible(weakly m-almost divisible,secondly weakly(m,n)-divisible).  相似文献   
2.
3.
About 11 reactions related to ethylbenzene are studied in this paper using transition state theory. The YL method proposed by Yao and Lin is utilized to calculate the anharmonic and the harmonic rate constants in these reaction processes in the temperature range of 300–4,000 K, energy diagram and the temperature dependence of the rate coefficients are also presented. The calculations indicate that the harmonic rate constants are larger than the anharmonic rate constants in most cases. Especially, there is a temperature junction between the high and low relationship between the anharmonic and harmonic rate constants in several reactions. Furthermore, the calculated values are in good agreement with other theoretical ones within the allowable error. Finally, the kinetic parameters and the thermodynamic parameters are calculated. To sum up, it can be concluded that the anharmonic effect in these reactions is very significant and cannot be ignored.  相似文献   
4.
5.
This paper investigates the problem of trajectory tracking control for quadrotor unmanned aerial vehicle (UAV) in the presence of dynamic obstacles and external disturbance forces/torques. More specifically, two new sliding mode disturbance observers are firstly designed to estimate the external disturbances, in which the observation errors can converge to zero in finite time. Furthermore, utilizing the observation information, a new sliding mode surface-like variable-based position tracking control scheme and a novel nonsingular terminal sliding mode-based attitude synchronization control scheme are developed to drive the UAV tracking the reference trajectory with obstacle avoiding. Moreover, the tracking errors of the close-loop control system can converge to zero within finite time by the analyses of Lyapunov methodology. Finally, the numerical simulation results are presented to illustrate the effectiveness of the proposed control schemes.  相似文献   
6.

In this paper, an improved controlled bidirectional quantum teleportation protocol of the special three-qubit state is proposed. In a little bit more detail, under the control of the third supervisor Charlie, Alice wants to send one special three-qubit entangled state to Bob, and at the meantime, Bob also wants to transmit another special three-qubit entangled state to Alice. In other words, both Alice and Bob can be the sender and receiver simultaneously. To achieve this aim, a specific eleven-qubit entangled state is shared among Alice, Bob and Charlie in advance acting as the quantum channel. Then, Alice and Bob first implement the GHZ-state measurement and Bell-state measurement respectively, and following Charlie’s single-qubit measurement. Finally, upon the foregoing measurement results, Alice and Bob can respectively implement the specific unitary operators on their local particles to recover the initial state transmitted by the other.

  相似文献   
7.

Quantum entanglement is one of the key methods in quantum information processing, but it is difficult to prepare quantum entanglement. Quantum walk is widely used in quantum computation and quantum simulation, it can be applied to the preparation of quantum entangled states. In this paper, a controllable quantum network coding scheme based on quantum walk is proposed. With the help of quantum walk, the scheme preliminary realized the entanglement distribution of butterfly network, reduced entanglement resources and enhanced scalability. According to the existing technology, it is feasible to implement the quantum network coding scheme proposed in this paper.

  相似文献   
8.
Protein oxidation leads to covalent modification of structure and deterioration of functional properties of quinoa protein. The objective of this study was to investigate the effects of ultrasonic treatment on the functional and physicochemical properties of quinoa protein oxidation aggregates. In this concern, 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH) was selected as oxidative modification of quinoa protein. The microstructure of quinoa protein displayed by scanning electron microscope (SEM) indicated that oxidation induced extensive aggregation, leading to carbonylation and degradation of sulfhydryl groups. Aggregation induced by oxidation had a negative effect on the solubility, turbidity, emulsifying stability. However, according to the analysis of physicochemical properties, ultrasonic significantly improved the water solubility of quinoa protein. The quinoa protein treated by ultrasonic for 30 min exhibited the best dispersion stability in water, which corresponded to the highest ζ-potential, smallest particle size and most uniform distribution. Based on the FT-IR, SDS-PAGE and surface hydrophobicity analysis, the increase of α-helix, β-turn and surface hydrophobicity caused by cavitation effect appeared to be the main mechanism of quinoa protein solubilization. In addition, the hydrophobic region of the protein was re-buried by excessive ultrasonic treatment, and the protein molecules were reaggregated by disulfide bonds. Microstructural observations further confirmed that ultrasonic treatment effectively inhibited protein aggregation and improved the functional properties of quinoa protein.  相似文献   
9.
This paper will deal with an anisotropic area-preserving flow which keeps the convexity of the evolving curve and the limiting curve converges to a homothety of a symmetric smooth strictly convex plane curve.  相似文献   
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号