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   929篇
  免费   29篇
  国内免费   22篇
教育   663篇
科学研究   231篇
体育   28篇
综合类   28篇
信息传播   30篇
  2023年   31篇
  2022年   43篇
  2021年   38篇
  2020年   23篇
  2019年   15篇
  2018年   4篇
  2017年   4篇
  2016年   15篇
  2015年   10篇
  2014年   65篇
  2013年   50篇
  2012年   117篇
  2011年   112篇
  2010年   88篇
  2009年   111篇
  2008年   53篇
  2007年   72篇
  2006年   80篇
  2005年   22篇
  2004年   6篇
  2003年   3篇
  2002年   6篇
  2001年   1篇
  2000年   6篇
  1999年   1篇
  1998年   3篇
  1997年   1篇
排序方式: 共有980条查询结果,搜索用时 22 毫秒
1.
This paper studies the stability problem of linear time-varying delay system. Firstly, a double integral inequality based on the second-order derivative is proposed in this paper. Secondly, novel Lyapunov–Krasovskii functional consisting of integral terms based on the second-order derivative is constructed to enhance the feasible region of delay-dependent stability. Based on the two aspects, new delay-dependent stability criteria which guarantee the asymptotic stability of linear systems with time-varying delay are given in the form of linear matrix inequality (LMI). Finally, several numerical examples are given to show the advantages of the proposed methods.  相似文献   
2.
3.
      后发企业在追赶过程中如何选择最佳追赶时机、如何规避追赶陷阱、如何进行能力重构等问题一直是学界和业界关注的焦点。本文采用案例研究方法,通过剖析一家芯片企业过去15年间的成败得失,对上述问题进行逐一解答。研究发现:市场需求状况、市场分层结构、技术迭代速率、技术获取成本、产业分工体系、产业知识流动等时机因素在后发企业快速崛起和高速发展过程中发挥着重要的作用。研究还发现:组织惯性陷阱、创新范式陷阱、品牌低端化陷阱是后发企业在追赶过程中所面临的主要陷阱,企业要想规避上述陷阱,需要从组织学习、组织保障、创新协同、创新来源、品牌定位、品牌维护等方面寻求相应的对策和方案。上述研究发现丰富了现有后发追赶理论体系,同时,为处在探索和追赶之中的中国后发企业提供了宝贵的经验和借鉴。  相似文献   
4.
海洋生态系统的健康和安全,直接关系到全人类的健康和福祉。有效监测数据不足、科学决策信息缺失等因素一定程度上影响了海洋可持续发展目标(SDG 14)的顺利实施。地球大数据具备宏观、动态、客观监测能力,可在支撑SDG 14实现中起到重要作用。在中国科学院战略性先导科技专项(A类)的支持下,基于地球大数据相关技术和方法,我国已有效开展了海洋缺失数据集生产、目标本地化模型构建等具体实践。在以上分析基础上,文章提出了积极参与国际社会地球大数据共享,加强科技创新对SDG 14实现的驱动,深度参与联合国海洋治理计划等建议。  相似文献   
5.
Aiming at the consensus tracking control problem of multiple autonomous underwater vehicles (AUVs) with state constraints, a new neural network (NN) and barrier Lyapunov function based finite-time command filtered backstepping control scheme is proposed. The finite-time command filter is utilized to filtering the virtual control signal, the error compensation signal is constructed to eliminate filtering error due to the use of filter, and the NN approximation technology is used to deal with the unknown nonlinear dynamics. The control scheme can guarantee that the consensus tracking errors of position states converge into the desired neighborhood of the origin in finite-time while not exceeding the predefined constraints. Finally, simulation studies prove the feasibility of proposed control algorithm.  相似文献   
6.
The existing studies on prescribed-time control cannot directly deal with nonlinear functions which don’t satisfy Lipschitz growth conditions. No results are available for prescribed-time containment control of pure-feedback UNMASs with prescribed performance. Therefore, completely unknown nonlinear function, prescribed-time tracking of system states and prescribed performance of containment errors are simultaneously considered in this paper. Fuzzy logic systems are utilized to approximate completely unknown nonlinear function. Prescribed-performance function is introduced and further incorporated into a novel speed function. Combining the proposed speed function and barrier Lyapunov function, this article presents a novel adaptive fuzzy prescribed-time containment control method which can guarantee, under prescribed performance, all followers converge to a convex formed by dynamic leaders in a prescribed time. Moreover, all tracking errors converge to predefined regions in a prescribed time. The effectiveness of the proposed prescribed-time containment control method are confirmed by strict proof and simulation.  相似文献   
7.
In the paper, a control algorithm for output regulation problem of nonlinear pure-feedback systems with unknown functions is proposed. The main contributions of the proposed method are not only to avoid Assumptions of unknown functions, but also adopt a non-backstepping control scheme. First, a high-gain state observer with disturbance signals is designed based on the new system that has been converted. Second, an internal model with the observer state is established. Finally, based on Lyapunov analysis and the neural network approximation theory, the control algorithm is proposed to ensure that all the signals of the closed-loop system are the semi-globally uniformly ultimately bounded, and the tracking error converges to a small neighborhood of the origin. Three simulation studies are worked out to show the effectiveness of the proposed approach.  相似文献   
8.
In this paper, a command filtered fault-tolerant control (CFFTC) approach is investigated for induction motors (IMs) discrete-time system in the presence of actuator faults and unknown load disturbances. Firstly, the IMs system discrete-time model is obtained by Euler method. Then, the fuzzy logic systems (FLSs) is utilized to compensate for unknown actuator faults. Besides, introducing the error compensation mechanism into discrete-time systems via command filters, “complexity of computation” and noncausal problem can be conquered, and the filtering error is avoided concurrently. Finally, simulation results demonstrate the validity of the presented fault-tolerant method for IMs system.  相似文献   
9.
The stabilization problem concerning the user datagram protocol (UDP) for networked control systems (NCSs) is investigated in this paper. More specifically, both the state and control signal can be lost during transmission, and the networked induced delay occurs while the control signal delivered to the actuator. On the other hand, no communication channel can be accessed from the actuator to the estimator (no acknowledge signal). The innovations of this paper include: (1) Based on the modified Riccati-ZXL equations, the necessary and sufficient stabilization conditions are developed for the NCSs with packet losses and transmission delay (UDP case); (2) We have verified that the separation principle holds for the finite horizon optimal output feedback control problem; (3) For 1-dimensional case, the maximal delay bound and the maximal packet losses rate are derived.  相似文献   
10.
This paper investigates the expected static group synchronization problem of the second-order multi-agent systems via pinning control. For directed communication topology with spanning tree, based on Gershgorin disk theorem and the matrix property, a static pinning control protocol with fixed gains is first introduced and some sufficient and necessary static group synchronization criteria are also established. It is worth mentioning that a rigorous proof is also given that only one pinning node is needed to guarantee static group synchronization, which could be inferred that our protocol might be more economical and effective in large scale of multi-agent systems. Then, for weakly connected directed communication topology with nodes of zero in-degree, an adaptive pinning control applied to the node with zero in-degree is also proposed to achieve static group synchronization. Finally, the efficiency of the proposed protocols is verified by two simulation examples.  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