全文获取类型
收费全文 | 20627篇 |
免费 | 3260篇 |
国内免费 | 2782篇 |
专业分类
电工技术 | 2971篇 |
综合类 | 3297篇 |
化学工业 | 968篇 |
金属工艺 | 258篇 |
机械仪表 | 1386篇 |
建筑科学 | 1947篇 |
矿业工程 | 329篇 |
能源动力 | 494篇 |
轻工业 | 179篇 |
水利工程 | 580篇 |
石油天然气 | 330篇 |
武器工业 | 364篇 |
无线电 | 2789篇 |
一般工业技术 | 2695篇 |
冶金工业 | 227篇 |
原子能技术 | 130篇 |
自动化技术 | 7725篇 |
出版年
2024年 | 167篇 |
2023年 | 390篇 |
2022年 | 535篇 |
2021年 | 596篇 |
2020年 | 853篇 |
2019年 | 806篇 |
2018年 | 788篇 |
2017年 | 982篇 |
2016年 | 1057篇 |
2015年 | 913篇 |
2014年 | 1186篇 |
2013年 | 1663篇 |
2012年 | 1582篇 |
2011年 | 1489篇 |
2010年 | 1141篇 |
2009年 | 1237篇 |
2008年 | 1245篇 |
2007年 | 1473篇 |
2006年 | 1226篇 |
2005年 | 1097篇 |
2004年 | 909篇 |
2003年 | 766篇 |
2002年 | 651篇 |
2001年 | 655篇 |
2000年 | 616篇 |
1999年 | 448篇 |
1998年 | 363篇 |
1997年 | 386篇 |
1996年 | 293篇 |
1995年 | 243篇 |
1994年 | 194篇 |
1993年 | 149篇 |
1992年 | 135篇 |
1991年 | 105篇 |
1990年 | 82篇 |
1989年 | 59篇 |
1988年 | 37篇 |
1987年 | 14篇 |
1986年 | 15篇 |
1985年 | 8篇 |
1984年 | 19篇 |
1983年 | 8篇 |
1982年 | 15篇 |
1981年 | 12篇 |
1980年 | 17篇 |
1979年 | 14篇 |
1978年 | 12篇 |
1977年 | 10篇 |
1959年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
ApplicationsofchaosinspreadspectrumcommunicationsApplicationsofSolitonTransmissionControlinOptimalDesignofLong-HaulSolitonCom... 相似文献
42.
Berlin Wu 《Computational Economics》1994,7(1):37-53
In this paper, the methods of time series for nonlinearity are briefly surveyed, with particular attention paid to a new test design based on a neural network specification. The proposed integrated expert system contains two main components: an identification environment and a robust forecasting design. The identification environment can be viewed as a integrated dynamic design in which cognitive capabilities arise as a direct consequence of their self-organizational properties. The integrated framework used for discussing the similarities and differences in the nonlinear time series behavior is presented. Moreover, its performance in prediction proves to be superior than the former work. For the investigation of robust forecasting, we perform a simulation study to demonstrate the applicability and the forecasting performance. 相似文献
43.
In this short paper we present a discrete-time field oriented controller (FOC) for current-fed induction motors which insures global asymptotic speed regulation as well as rotor flux norm tracking. To the best of our knowledge, this is the first time such a result is rigorously established for a controller implemented in discrete-time. To insure global stability a condition on the reference for the rotor flux norm, which is time-varying, is imposed. This condition disappears as the sampling period goes to zero, hence allowing for independent speed regulation and rotor flux norm tracking. One important feature of our scheme is that, compared with the first-difference approximation of the classical indirect FOC, the additional computational burden is negligible. It is also shown that the result can easily be extended to the case of tracking time-varying references in speed or position. 相似文献
44.
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
45.
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
46.
An adaptive fuzzy decentralized backstepping output-feedback control approach is proposed for a class of nonlinear large-scale systems with completely unknown functions,the interconnections mismatched in control inputs,and without the measurements of the states.Fuzzy logic systems are employed to approximate the unknown nonlinear functions,and an adaptive high-gain observer is developed to estimate the unmeasured states.Using the designed high-gain observer,and combining the fuzzy adaptive control theory with backstepping approach,an adaptive fuzzy decentralized backstepping output-feedback control scheme is developed.It is proved that the proposed control approach can guarantee that all the signals of the closed-loop system are semi-globally uniformly ultimately bounded(SUUB),and that the observer errors and the tracking errors converge to a small neighborhood of the origin by appropriate choice of the design parameters.Finally,a simulation example is provided to show the eectiveness of the proposed approach. 相似文献
47.
This paper addresses the problem of approximating parameter dependent nonlinear systems in a unified framework. This modeling has been presented for the first time in the form of parameter dependent piecewise affine systems. In this model, the matrices and vectors defining piecewise affine systems are affine functions of parameters. Modeling of the system is done based on distinct spaces of state and parameter, and the operating regions are partitioned into the sections that we call ’multiplied simplices’. It is proven that this method of partitioning leads to less complexity of the approximated model compared with the few existing methods for modeling of parameter dependent nonlinear systems. It is also proven that the approximation is continuous for continuous functions and can be arbitrarily close to the original one. Next, the approximation error is calculated for a special class of parameter dependent nonlinear systems. For this class of systems, by solving an optimization problem, the operating regions can be partitioned into the minimum number of hyper-rectangles such that the modeling error does not exceed a specified value. This modeling method can be the first step towards analyzing the parameter dependent nonlinear systems with a uniform method. 相似文献
48.
以贵州尖山营滑坡为工程背景,通过对深度学习的总结与分析,建立多层感知器模型以对该滑坡危险区范围进行非线性预测研究。通过对深度神经网络算法的优化,构建64-128-32-1四层多层感知器模型,并以滑坡最大高差、滑坡体积、滑源区坡度、坡脚坡度、地层倾角作为输入量,以滑坡最大水平运动距离作为输出量对该模型进行训练,实现影响因素与运动距离的非线性映射。根据对贵州省尖山营滑坡调查和研究,尖山营滑坡区域面积约648 700 m2,体积约1 200万 m3,属于特大型滑坡。依据最优模型对该滑坡进行滑距预测,滑坡平面直线距离1 769 m区域内为危险区域。 相似文献
49.
A robustness analysis and synthesis for incomplete nonlinear decoupling for a class of nonlinear systems is discussed. Rigid and elastic-joint robot models belong to this class. For the elastic case, a transformation facilitates the robustness analysis under a weak assumption. Charts with H
1- and H
- norms of closed-loop disturbance transfer functions of the nonlinear-decoupled system are presented for a robust pole assignment. 相似文献
50.
Positioning control systems for robot arms are presented within a general framework in view of unification and classification. Treating coupling torques from other links as an external disturbance reduces the design of the control system to that of SISO servomechanisms driving each of the robot axes individually. A short survey of many control strategies proposed in the literature presents them as different methods aiming at attenuation of this disturbance. The use of disturbance observers is shown to provide a nice and simple way for that purpose. This could be applied to the improvement of actual industrial robots at the cost of slight software modifications. 相似文献