全文获取类型
收费全文 | 218589篇 |
免费 | 74078篇 |
国内免费 | 48721篇 |
专业分类
电工技术 | 31483篇 |
技术理论 | 1篇 |
综合类 | 23993篇 |
化学工业 | 28454篇 |
金属工艺 | 26967篇 |
机械仪表 | 8703篇 |
建筑科学 | 14922篇 |
矿业工程 | 14182篇 |
能源动力 | 9291篇 |
轻工业 | 24652篇 |
水利工程 | 8277篇 |
石油天然气 | 14047篇 |
武器工业 | 4136篇 |
无线电 | 33888篇 |
一般工业技术 | 33366篇 |
冶金工业 | 7751篇 |
原子能技术 | 1594篇 |
自动化技术 | 55681篇 |
出版年
2024年 | 3016篇 |
2023年 | 5364篇 |
2022年 | 6962篇 |
2021年 | 8394篇 |
2020年 | 10506篇 |
2019年 | 19204篇 |
2018年 | 20670篇 |
2017年 | 22139篇 |
2016年 | 21628篇 |
2015年 | 21081篇 |
2014年 | 20113篇 |
2013年 | 19501篇 |
2012年 | 19191篇 |
2011年 | 15574篇 |
2010年 | 14060篇 |
2009年 | 10830篇 |
2008年 | 8889篇 |
2007年 | 8122篇 |
2006年 | 6848篇 |
2005年 | 6315篇 |
2004年 | 8562篇 |
2003年 | 6930篇 |
2002年 | 6552篇 |
2001年 | 5716篇 |
2000年 | 5245篇 |
1999年 | 4876篇 |
1998年 | 4271篇 |
1997年 | 3812篇 |
1996年 | 3657篇 |
1995年 | 3670篇 |
1994年 | 3026篇 |
1993年 | 2739篇 |
1992年 | 2649篇 |
1991年 | 1927篇 |
1990年 | 1506篇 |
1989年 | 1394篇 |
1988年 | 1073篇 |
1987年 | 329篇 |
1986年 | 299篇 |
1985年 | 218篇 |
1984年 | 148篇 |
1982年 | 156篇 |
1981年 | 153篇 |
1976年 | 240篇 |
1975年 | 213篇 |
1972年 | 235篇 |
1971年 | 128篇 |
1960年 | 205篇 |
1905年 | 118篇 |
1904年 | 150篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
On formalism and stability of switched systems 总被引:1,自引:1,他引:0
In this paper,we formulate a uniform mathematical framework for studying switched systems with piecewise linear partitioned state space and state dependent switching.Based on known results from the the... 相似文献
992.
This paper studies the input-output finite-time stabilization problem for time-varying linear singular systems. The output and the input refer to the controlled output and the disturbance input,respectively.Two classes of disturbance inputs are considered,which belong to L-two and L-infinity.Sufficient conditions are firstly provided which guarantee the input-output finite-time stability.Based on this,state feedback controllers are designed such that the resultant closed-loop systems are input-output finite-time stable.The conditions are presented in terms of differential linear matrix inequalities.Finally,an example is presented to show the validity of the proposed results. 相似文献
993.
In this paper,an adaptive control scheme is introduced for permanent magnet synchronous machines (PMSMs)as an alternative to classical control techniques.The adaptive control strategy capitalizes on the machine’s inverse dynamics to achieve accurate tracking by using an observer to approximate disturbance in the form of friction and load torque.The controller’s output is then fed to a space vector pulse width modulation(SVPWM)algorithm to produce duty cycles for the inverter.The control scheme is validated through a set of simulations on an experimentally validated PMSM model.Results for different situations highlight its high speed tracking accuracy and high performance in compensating for friction and load disturbances of various magnitudes. 相似文献
994.
This article presents a design of the internal model control(IMC)based single degree of freedom(SDF) fractional order(FO)PID controller with a desired bandwidth specification for a class of fractional order system(FOS). The drawbacks of the SDF FO-IMC are eliminated with the help of the two-degree of freedom(TDF)FO PID controller. The robust stability and robust performance of the designed controller are analyzed using an example. 相似文献
995.
A new formation navigation approach derived from multi-robots cooperative online FastSLAM is proposed. In this approach,the leader and follower robots are defined.The posteriori estimation of the leader robot state is treated as a relative reference for all follower robots to correct their state priori estimations.The control volume of individual follower will be achieved from the results of the corrected estimation.All robots are observed as landmarks with known associations by the others and are considered in their landmarks updating.By the method,the errors of the robot posterior estimations are reduced and the formation is well kept.The simulation and physical experiment results show that the multi-robots relative localization accuracy is improved and the formation navigation control is more stable and efficient than normal leader-following strategy.The algorithm is easy in implementation. 相似文献
996.
System identification uses system inputs and outputs to raise mathematical models.Various techniques of system identification exist that offer a nominal model and an uncertainty bound.Many practical systems such as thermal processes & chemical processes have inbuilt time delay.If the time delay used in the system model for controller design does not concur with the actual process time delay,a closed-loop system may be unstable or demonstrate unacceptable transient response characteristics so here the time delay is assumed to be time-invariant. This paper proposes on-line identification of delayed complex/uncertain systems using instrumental variable(Ⅳ) method.Parametric uncertainty has been considered which may be represented by variations of certain system parameters over some possible range.This method allows consistent estimation when the system parameters are associated with the noise terms,as the IV methods(IVM’s)usually make no assumption on the noise correlation configuration.The faster convergence of the parameters including noise terms has been proved in this paper.Iterative prefiltering(IP)method has also been used for the identification of the delayed uncertain system and the graphical results given in this paper demonstrate that the convergence results are inferior to the instrumental variable method. 相似文献
997.
This paper concerns the stability analysis problem of discrete linear systems with state saturation using a saturation-dependent Lyapunov functional.We introduce a free matrix characterized by the sum of the absolute value of each elements for each row less than 1,which makes the state with saturation constraint reside in a convex polyhedron.A saturation-dependent Lyapunov functional is then designed to obtain a sufficient condition for such systems to be globally asymptotically stable.Based on this stability criterion,the state feedback control law synthesis problem is also studied.The obtained results are formulated in terms of bilinear matrix inequalities that can be solved by the presented iterative linear matrix inequality algorithm.Two numerical examples are used to demonstrate the effectiveness of the proposed method. 相似文献
998.
This paper investigates the stability analysis and antiwindup design problem for a class of discrete-time switched linear systems with time-varying norm-bounded uncertainties and saturating actuators by using the switched Lyapunov function approach.Supposing that a set of linear dynamic output controllers have been designed to stabilize the switched system without considering its input saturation,we design antiwindup compensation gains in order to enlarge the domain of attraction of the closed-loop system in the presence of saturation.Then,in terms of a sector condition,the antiwindup compensation gains which aim to maximize the estimation of domain of attraction of the closed-loop system are presented by solving a convex optimization problem with linear matrix inequality(LMI)constraints.A numerical example is given to demonstrate the effectiveness of the proposed design method. 相似文献
999.
随着IPv4地址资源的日益枯竭,互联网从IPv4向IPv6过渡势在必行。为了进一步推动该校IPv4向IPv6的平稳过渡,文章经过技术论证后,采用MP-BGP扩展的4over6隧道技术,构建了一个IPv4over IPv6实验网络平台,使运行IPv4单协议栈的网络能够跨越IPv6骨干网络实现互联互通。 相似文献
1000.
双星定位系统的应用是外弹道估计中的一种发展趋势。文章给出基于双星、光雷的联合测量模型,建立基于半参数回归的外弹道节省参数估计模型;给出基于半参数回归的外弹道节省参数估计算法及计算步骤,并从理论上分析了基于半参数回归的外弹道节省参数估计算法能有效地消除非线性因素对参数估计性能的影响,其估计精度优于经典的节省参数建模方法,并通过仿真得到:该算法确实有效。 相似文献