全文获取类型
收费全文 | 74222篇 |
免费 | 13732篇 |
国内免费 | 9765篇 |
学科分类
工业技术 | 97719篇 |
出版年
2024年 | 449篇 |
2023年 | 1490篇 |
2022年 | 2672篇 |
2021年 | 2930篇 |
2020年 | 3161篇 |
2019年 | 2600篇 |
2018年 | 2522篇 |
2017年 | 2903篇 |
2016年 | 3307篇 |
2015年 | 3959篇 |
2014年 | 5143篇 |
2013年 | 5046篇 |
2012年 | 6257篇 |
2011年 | 6497篇 |
2010年 | 5301篇 |
2009年 | 5485篇 |
2008年 | 5743篇 |
2007年 | 6373篇 |
2006年 | 5113篇 |
2005年 | 4215篇 |
2004年 | 3450篇 |
2003年 | 2743篇 |
2002年 | 2048篇 |
2001年 | 1684篇 |
2000年 | 1388篇 |
1999年 | 1122篇 |
1998年 | 882篇 |
1997年 | 678篇 |
1996年 | 556篇 |
1995年 | 389篇 |
1994年 | 343篇 |
1993年 | 254篇 |
1992年 | 235篇 |
1991年 | 123篇 |
1990年 | 157篇 |
1989年 | 104篇 |
1988年 | 89篇 |
1987年 | 39篇 |
1986年 | 40篇 |
1985年 | 35篇 |
1984年 | 28篇 |
1983年 | 27篇 |
1982年 | 26篇 |
1981年 | 15篇 |
1980年 | 25篇 |
1979年 | 11篇 |
1978年 | 11篇 |
1977年 | 10篇 |
1975年 | 11篇 |
1959年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Jianhuai Dong Zhixuan Dong 《International Journal of Adaptive Control and Signal Processing》2020,34(10):1466-1482
This article studies the optimal filtering and control for wireless networked control systems (WNCSs). In WNCSs, packets may be lost in both control and feedback channels and user datagram protocol is usually used to improve the performance of the real-time control. Relevant literature indicates that the conventional optimal filtering for such a system cannot be applied in practice due to the complex calculation with Gaussian mixtures. This paper proposes a novel scheme to realize the optimal filtering and the linear quadratic Gaussian control for WNCSs, in which the controlled node performs a local estimation and the remote-control node performs the final estimation and control, and a synchronization of two estimators is guaranteed by a communication mechanism. An optimal filtering algorithm is developed, the stability condition of the filtering error covariance is obtained, optimal finite-horizon and infinite-horizon control are derived, and the stability of the closed-loop control system is proved. Numerical simulations show the validity and feasibility of the theoretical results. 相似文献
52.
This paper proposes the application of Covariance Matrix Adaptation Evolution Strategy (CMA-ES) in fixed structure H∞ loop shaping controller design. Integral Time Absolute Error (ITAE) performance requirement is incorporated as a constraint with an objective of maximization of stability margin in the fixed structure H∞ loop shaping controller design problem. Pneumatic servo system, separating tower process and F18 fighter aircraft system are considered as test systems. The CMA-ES designed fixed structure H∞ loop-shaping controller is compared with the traditional H∞ loop shaping controller, non-smooth optimization and Heuristic Kalman Algorithm (HKA) based fixed structure H∞ loop shaping controllers in terms of stability margin. 20% perturbation in the nominal plant is used to validate the robustness of the CMA-ES designed H∞ loop shaping controller. The effect of Finite Word Length (FWL) is considered to show the implementation difficulties of controller in digital processors. Simulation results demonstrated that CMA-ES based fixed structure H∞ loop shaping controller is suitable for real time implementation with good robust stability and performance. 相似文献
53.
随着大数据和云计算的技术的深入应用,人工智能时代的机器学习和深度学习更需要日益增长的数据,因此数据安全与隐私保护变得更加迫切。本文介绍人工智能的定义以及特征,探究数据安全和隐私保护现状,分析数据安全和隐私保护面临的诸多问题,并提出在人工智能时代对数据安全和隐私保护的措施。 相似文献
54.
Central force optimization (CFO) is an efficient and powerful population-based intelligence algorithm for optimization problems. CFO is deterministic in nature, unlike the most widely used metaheuristics. CFO, however, is not completely free from the problems of premature convergence. One way to overcome local optimality is to utilize the multi-start strategy. By combining the respective advantages of CFO and the multi-start strategy, a multi-start central force optimization (MCFO) algorithm is proposed in this paper. The performance of the MCFO approach is evaluated on a comprehensive set of benchmark functions. The experimental results demonstrate that MCFO not only saves the computational cost, but also performs better than some state-of-the-art CFO algorithms. MCFO is also compared with representative evolutionary algorithms. The results show that MCFO is highly competitive, achieving promising performance. 相似文献
55.
Fresh and frozen-thawed (F-T) pork meats were classified by Vis–NIR hyperspectral imaging. Eight optimal wavelengths (624, 673, 460, 588, 583, 448, 552 and 609 nm) were selected by successive projections algorithm (SPA). The first three principal components (PCs) obtained by principal component analysis (PCA) accounted for over 99.98% of variance. Gray-level-gradient co-occurrence matrix (GLGCM) was applied to extract 45 textural features from the PC images. The correct classification rate (CCR) was employed to evaluate the performance of the partial least squares-discriminate analysis (PLS-DA) models, by using (A) the reflected spectra at full wavelengths and (B) those at the optimal wavelengths, (C) the extracted textures based on the PC images, and (D) the fused variables combining spectra at the optimal wavelengths and textures. The results showed that the best CCR of 97.73% was achieved by applying (D), confirming the high potential of textures for fresh and F-T meat discrimination. 相似文献
56.
57.
目前,基于因素空间理论的背景基提取算法计算过程复杂,初始化必须依赖各因素极值,基点数量提取冗余等原因,未能在应用中取得很好效果。为此,结合内点判别法和知识可继承、可扩展的思想,提出一种计算简单、初始化独立、基点数量小的改进的背景基提取算法。然后,利用改进的背景基提取算法构造出一种全新的数据分类算法-基点分类算法,基点分类算法以提取每一类样本的背景基为预测模型,再通过新定义的λ-背景基,优化预测模型。数值实验表明:基点分类算法原理简单、构造难度小、分类模型泛化能力强,预测能力准确率高,同时严格的模型限定区域又能为识别新类别提供新方法。 相似文献
58.
Defects are often present in rolled products, such as wire rod. The market demand for wire rod without any defects has increased. In the final wire rod products, defects originating from steel making, casting, pre‐rolling of billets and during wire rod rolling can appear. In this work, artificial V‐shaped longitudinal surface cracks have been analysed experimentally and by means of FEM. The results indicate that the experiments and FEM calculations show the same tendency except in two cases, where instability due to fairly “round” false round bars disturbed the experiment. FE studies in combination with practical experiments are necessary in order to understand the behaviour of the material flows in the groove and to explain whether the crack will open up as a V‐shape or if it will be closed as an I‐shape. 相似文献
59.
60.