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   1148篇
  免费   246篇
  国内免费   106篇
化学   142篇
力学   183篇
综合类   6篇
数学   169篇
物理学   526篇
无线电   474篇
  2024年   10篇
  2023年   26篇
  2022年   42篇
  2021年   47篇
  2020年   48篇
  2019年   29篇
  2018年   31篇
  2017年   51篇
  2016年   66篇
  2015年   61篇
  2014年   104篇
  2013年   101篇
  2012年   91篇
  2011年   88篇
  2010年   75篇
  2009年   85篇
  2008年   65篇
  2007年   53篇
  2006年   52篇
  2005年   51篇
  2004年   32篇
  2003年   24篇
  2002年   35篇
  2001年   30篇
  2000年   29篇
  1999年   31篇
  1998年   32篇
  1997年   14篇
  1996年   11篇
  1995年   11篇
  1994年   20篇
  1993年   7篇
  1992年   7篇
  1991年   5篇
  1990年   5篇
  1989年   8篇
  1988年   7篇
  1987年   4篇
  1986年   3篇
  1985年   1篇
  1984年   2篇
  1982年   1篇
  1981年   1篇
  1979年   1篇
  1977年   1篇
  1975年   1篇
  1957年   1篇
排序方式: 共有1500条查询结果,搜索用时 15 毫秒
71.
The quantum trajectory renders the optimal estimation of quantum state. It is a classical Itô stochastic differential equation. The Lyapunov global stabilization problem is solved for squeezed noise quantum trajectory. Lyapunov control stabilizes the quantum system toward one eigenstate. A two-level bistable quantum system is simulated as an example.  相似文献   
72.
针对嫦娥三号软着陆轨道设计与控制策略问题,在合理假设的前提下,建立动力学模型,求解得到了嫦娥三号着陆准备轨道近月点和远月点的速度。针对软着陆过程的6个阶段,通过受力分析,建立了嫦娥三号运动的微分方程模型,以燃料消耗最小为优化目标,以每个阶段的起止状态为约束条件,将软着陆轨道的优化设计问题转化为主发动机推力的泛函极值问题,并将其控制函数转化为近似的多项式函数优化问题。运用四阶Runge-Kutta差分迭代方法进行求解计算,从而得到各个阶段的最优控制函数和控制策略。结果表明,嫦娥三号软着陆过程耗时695s,消耗燃料1 269.1kg。  相似文献   
73.
74.
The hydrogen molecule ion is a two‐center force system expressed under the prolate spheroidal coordinates, whose quantum motions and quantum trajectories have never been addressed in the literature before. The momentum operators in this coordinate system are derived for the first time from the Hamilton equations of motion and used to construct the Hamiltonian operator. The resulting Hamiltonian comprises a kinetic energy T and a total potential VTotal consisting of the Coulomb potential and a quantum potential. It is shown that the participation of the quantum potential and the accompanied quantum forces in the force interaction within H2+ is essential to develop an electronic motion consistent with the prediction of the probability density function |Ψ|2. The motion of the electron in H2+ can be either described by the Hamilton equations derived from the Hamiltonian H = TK + VTotal or by the Lagrange equations derived from the Lagrangian H = TK ? VTotal. Solving the equations of motion with different initial positions, we show that the solutions yield an assembly of electronic quantum trajectories whose distribution and concentration reconstruct the σ and π molecular orbitals in H2+. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011  相似文献   
75.
This paper addresses a master-slave synchronization strategy for complex dynamic systems based on feedback control.This strategy is applied to 3-DOF planar manipulators in order to obtain synchronization in such complicated as chaotic motions of end-effectors.A chaotic curve is selected from Duffing equation as the trajectory of master end-effector and a piecewise approximation method is proposed to accurately represent this chaotic trajectory of end-effectors.The dynamical equations of master-slave mani...  相似文献   
76.
An application to fuzzy economic systems of the fuzzy multi-valued functions theory elaborated by both of us in our previous papers is presented. First, stationary and dynamic fuzzy economic models are defined. Next the optimality of fuzzy trajectories of these models is introduced and investigated.  相似文献   
77.
提高应答机测距精度的环节与测量技术探讨   总被引:3,自引:2,他引:1  
胡建平 《电讯技术》2003,43(1):15-20,37
本文提出了提高飞行器载应答机测距精度的方法与思路,并对一些典型误差源进行了定性的分析。  相似文献   
78.
We introduce and describe the Multiple Gravity Assist problem, a global optimisation problem that is of great interest in the design of spacecraft and their trajectories. We discuss its formalization and we show, in one particular problem instance, the performance of selected state of the art heuristic global optimisation algorithms. A deterministic search space pruning algorithm is then developed and its polynomial time and space complexity derived. The algorithm is shown to achieve search space reductions of greater than six orders of magnitude, thus reducing significantly the complexity of the subsequent optimisation. This work was partially funded under the Ariadna scheme of the European Space Agency, contract number 18138/04/NL/MV.  相似文献   
79.
A revised iterative method based on Green function defined by quadratures along a single trajectory is proposed to solve the low-lying quantum wave function for Schrodinger equation. Specially a new expression of the perturbed energy is obtained, which is much simpler than the traditional one. The method is applied to solve the unharmonic oscillator potential. The revised iteration procedure gives exactly the same result as those based on the single trajectory quadrature method. A comparison of the revised iteration method to the old one is made using the example of Stark effect. The obtained results are consistent to each other after making power expansion.  相似文献   
80.
We consider quasistable multicriteria problems of discrete optimization on systems of subsets (trajectory problems). We single out the class of problems for which new Pareto optima can appear, while other optima for the problems do not disappear when the coefficients of the objective functions are slightly perturbed (in the Chebyshev metric). For the case of linear criteria (MINSUM), we obtain a formula for calculating the quasistability radius of the problem. Translated fromMatemalicheskie Zametki, Vol. 63, No. 1, pp. 21–27, January, 1998. This research was supported by the Belarus Foundation for Basic Research under grant No. F95-70.  相似文献   
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