全文获取类型
收费全文 | 21694篇 |
免费 | 3137篇 |
国内免费 | 1930篇 |
专业分类
电工技术 | 2420篇 |
综合类 | 2457篇 |
化学工业 | 1254篇 |
金属工艺 | 198篇 |
机械仪表 | 1202篇 |
建筑科学 | 679篇 |
矿业工程 | 263篇 |
能源动力 | 467篇 |
轻工业 | 227篇 |
水利工程 | 274篇 |
石油天然气 | 315篇 |
武器工业 | 458篇 |
无线电 | 5566篇 |
一般工业技术 | 1592篇 |
冶金工业 | 271篇 |
原子能技术 | 133篇 |
自动化技术 | 8985篇 |
出版年
2024年 | 101篇 |
2023年 | 338篇 |
2022年 | 537篇 |
2021年 | 636篇 |
2020年 | 718篇 |
2019年 | 707篇 |
2018年 | 642篇 |
2017年 | 892篇 |
2016年 | 926篇 |
2015年 | 994篇 |
2014年 | 1367篇 |
2013年 | 1606篇 |
2012年 | 1491篇 |
2011年 | 1783篇 |
2010年 | 1316篇 |
2009年 | 1353篇 |
2008年 | 1458篇 |
2007年 | 1602篇 |
2006年 | 1250篇 |
2005年 | 1122篇 |
2004年 | 870篇 |
2003年 | 768篇 |
2002年 | 637篇 |
2001年 | 509篇 |
2000年 | 423篇 |
1999年 | 386篇 |
1998年 | 329篇 |
1997年 | 311篇 |
1996年 | 221篇 |
1995年 | 248篇 |
1994年 | 200篇 |
1993年 | 143篇 |
1992年 | 146篇 |
1991年 | 105篇 |
1990年 | 105篇 |
1989年 | 66篇 |
1988年 | 55篇 |
1987年 | 45篇 |
1986年 | 31篇 |
1985年 | 42篇 |
1984年 | 59篇 |
1983年 | 29篇 |
1982年 | 44篇 |
1981年 | 43篇 |
1980年 | 27篇 |
1979年 | 17篇 |
1978年 | 17篇 |
1977年 | 14篇 |
1974年 | 3篇 |
1959年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
13.
A method for estimating the sway angle using an observer has already been proposed. The state observer estimates the sway angle accurately and must use the detected sway angle value. However, the estimated sway angle has an error owing to rope length error, friction force, and wind. Moreover, the container mass cannot be determined, and therefore the observer parameter is not suitable. We already proposed robust antisway control for overcoming rope length error without adding a new sensor. Further, we designed a friction disturbance observer to cancel out the influence of the friction force. In this paper, we first propose a container mass estimation method when a crane system performs rolling up control. The observer parameter can be selected using the estimated mass value. Second, in crane parallel shift control, we propose a robust antisway control even when there is a wind disturbance. We design a wind disturbance observer and propose a wind disturbance estimator to separate the friction observer output from the wind disturbance observer output. We confirm through experiments that the proposed method can reduce vibration. 相似文献
14.
孙希东 《自动化技术与应用》2015,34(4)
本文给出一种采用DPT估计SNCK信号时宽—带宽积的方法,并通过仿真该估计方法的性能与其它估计方法进行比较.首先给出SNCK信号参数估计的一般过程.为了便于计算和理论推导,根据估计出的中心频率将接收到的SNCK信号搬移到零频,从而进一步估计其它参数,如采用DPT估计SNCK信号时宽带宽积.本文将重点研究采用DPT算法估计SNCK信号值的方法. 相似文献
15.
Yingcai Bi Menglu Lan Jiaxin Li Shupeng Lai Ben M. Chen 《Asian journal of control》2019,21(4):1732-1744
Micro Aerial Vehicles (MAVs) have great potentials to be applied for indoor search and rescue missions. In this paper, we propose a modular lightweight design of an autonomous MAV with integrated hardware and software. The MAV is equipped with the 2D laser scanner, camera, mission computer and flight controller, running all the computation onboard in real time. The onboard perception system includes a laser‐based SLAM module and a custom‐designed visual detection module. A dual Kalman filter design provides robust state estimation by multiple sensor fusion. Specifically, the fusion module provides robust altitude measurement in the circumstance of surface changing. In addition, indoor‐outdoor transition is explicitly handled by the fusion module. In order to efficiently navigate through obstacles and adapt to multiple tasks, a task tree‐based mission planning method is seamlessly integrated with path planning and control modules. The MAV is capable of searching and rescuing victims from unknown indoor environments effectively. It was validated by our award‐winning performance at the 2017 International Micro Air Vehicle Competition (IMAV 2017), held in Toulouse, France. The performance video is available on https://youtu.be/8H19ppS_VXM . 相似文献
16.
In this letter, we address the problem of Direction of Arrival (DOA) estimation with nonuniform linear array in the context of sparse Bayesian learning (SBL) framework. The nonuniform array output is deemed as an incomplete-data observation, and a hypothetical uniform linear array output is treated as an unavailable complete-data observation. Then the Expectation-Maximization (EM) criterion is directly utilized to iteratively maximize the expected value of the complete-data log likelihood under the posterior distribution of the latent variable. The novelties of the proposed method lie in its capability of interpolating the actual received data to a virtual uniform linear array, therefore extending the achievable array aperture. Simulation results manifests the superiority of the proposed method over off-the-shelf algorithms, specially on circumstances such as low SNR, insufficient snapshots, and spatially adjacent sources. 相似文献
17.
为提高稀疏表示跟踪模型性能,提出一种分段加权的反向稀疏跟踪算法,将跟踪问题转化为在贝叶斯框架下寻找概率最高的候选对象问题,构造不同的分段权重函数来分别度量候选目标与正负模板的判别特征系数。通过池化来降低跟踪结果的不确定性干扰,选择正负模板加权系数差值最大的候选表示作为跟踪结果。实验表明,在光照变化、遮挡、快速运动、运动模糊情况下,所提出的算法可以确保跟踪结果的准确性和鲁棒性。 相似文献
18.
Miroslav Kárný Marko Ruman 《International Journal of Adaptive Control and Signal Processing》2021,35(5):660-675
Any knowledge extraction relies (possibly implicitly) on a hypothesis about the modelled-data dependence. The extracted knowledge ultimately serves to a decision-making (DM). DM always faces uncertainty and this makes probabilistic modelling adequate. The inspected black-box modeling deals with “universal” approximators of the relevant probabilistic model. Finite mixtures with components in the exponential family are often exploited. Their attractiveness stems from their flexibility, the cluster interpretability of components and the existence of algorithms for processing high-dimensional data streams. They are even used in dynamic cases with mutually dependent data records while regression and auto-regression mixture components serve to the dependence modeling. These dynamic models, however, mostly assume data-independent component weights, that is, memoryless transitions between dynamic mixture components. Such mixtures are not universal approximators of dynamic probabilistic models. Formally, this follows from the fact that the set of finite probabilistic mixtures is not closed with respect to the conditioning, which is the key estimation and predictive operation. The paper overcomes this drawback by using ratios of finite mixtures as universally approximating dynamic parametric models. The paper motivates them, elaborates their approximate Bayesian recursive estimation and reveals their application potential. 相似文献
19.
This article theoretically and empirically analyzes backtesting portfolio value-at-risk (VaR) with estimation risk in an intrinsically multi-variate framework. It particularly takes into account the estimation of portfolio weights in forecasting portfolio VaR and its impact on backtesting. It shows that the estimation risk from estimating portfolio weights and that from estimating the multi-variate dynamic model make the existing methods in a univariate framework inapplicable. It proposes a general theory to quantify estimation risk applicable to the present problem and suggests practitioners a simple but effective way to implement valid inference to overcome the effect of estimation risk in backtesting portfolio VaR. In particular, we apply our theory to the efficient mean-variance-skewness portfolio for a multi-variate generalized autoregressive conditional heteroscedasticity model with multi-variate general hyperbolic distributed innovations. Some Monte Carlo simulations and an empirical application demonstrate the merits of our method. 相似文献
20.
This paper is concerned with the problem of joint input and state estimation for linear stochastic systems with direct feedthrough. Based on the fact that each unknown input between any two time steps is always bounded, a novel improved algorithm is proposed. Compared with existing results, this algorithm can effectively enhance estimation accuracy. Moreover, the stability of the algorithm is also discussed. Finally, an illustrative example is given to demonstrate the effectiveness of the proposed approach. 相似文献