全文获取类型
收费全文 | 3245篇 |
免费 | 106篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 62篇 |
综合类 | 6篇 |
化学工业 | 528篇 |
金属工艺 | 33篇 |
机械仪表 | 53篇 |
建筑科学 | 178篇 |
矿业工程 | 10篇 |
能源动力 | 49篇 |
轻工业 | 1018篇 |
水利工程 | 23篇 |
石油天然气 | 9篇 |
无线电 | 246篇 |
一般工业技术 | 409篇 |
冶金工业 | 366篇 |
原子能技术 | 21篇 |
自动化技术 | 342篇 |
出版年
2022年 | 29篇 |
2021年 | 59篇 |
2020年 | 39篇 |
2019年 | 39篇 |
2018年 | 46篇 |
2017年 | 44篇 |
2016年 | 51篇 |
2015年 | 47篇 |
2014年 | 78篇 |
2013年 | 144篇 |
2012年 | 85篇 |
2011年 | 134篇 |
2010年 | 95篇 |
2009年 | 76篇 |
2008年 | 111篇 |
2007年 | 98篇 |
2006年 | 77篇 |
2005年 | 64篇 |
2004年 | 70篇 |
2003年 | 70篇 |
2002年 | 39篇 |
2001年 | 39篇 |
2000年 | 35篇 |
1999年 | 44篇 |
1998年 | 85篇 |
1997年 | 59篇 |
1996年 | 58篇 |
1995年 | 46篇 |
1994年 | 55篇 |
1993年 | 43篇 |
1992年 | 30篇 |
1989年 | 27篇 |
1986年 | 25篇 |
1981年 | 24篇 |
1976年 | 34篇 |
1971年 | 26篇 |
1923年 | 30篇 |
1917年 | 58篇 |
1916年 | 48篇 |
1915年 | 33篇 |
1912年 | 40篇 |
1911年 | 46篇 |
1910年 | 28篇 |
1909年 | 32篇 |
1908年 | 33篇 |
1907年 | 33篇 |
1906年 | 44篇 |
1905年 | 45篇 |
1904年 | 51篇 |
1903年 | 29篇 |
排序方式: 共有3353条查询结果,搜索用时 31 毫秒
51.
We continue our study of the complexity of MSO-definable local temporal logics over concurrent systems that can be described by Mazurkiewicz traces. In previous papers, we showed that the satisfiability problem for any such logic is in PSPACE (provided the dependence alphabet is fixed, Gastin and Kuske (2003) [10]) and remains in PSPACE for all classical local temporal logics even if the dependence alphabet is part of the input, Gastin and Kuske (2007) [8]. In this paper, we consider the uniform satisfiability problem for arbitrary MSO-definable local temporal logics. For this problem, we prove multi-exponential lower and upper bounds that depend on the number of alternations of set quantifiers present in the chosen MSO-modalities. 相似文献
52.
Sliding Mode Control with Adaptive Fuzzy Dead-Zone Compensation of an Electro-hydraulic Servo-System 总被引:2,自引:0,他引:2
Wallace M. Bessa Max S. Dutra Edwin Kreuzer 《Journal of Intelligent and Robotic Systems》2010,58(1):3-16
Electro-hydraulic servo-systems are widely employed in industrial applications such as robotic manipulators, active suspensions,
precision machine tools and aerospace systems. They provide many advantages over electric motors, including high force to
weight ratio, fast response time and compact size. However, precise control of electro-hydraulic systems, due to their inherent
nonlinear characteristics, cannot be easily obtained with conventional linear controllers. Most flow control valves can also
exhibit some hard nonlinearities such as dead-zone due to valve spool overlap. This work describes the development of an adaptive
fuzzy sliding mode controller for an electro-hydraulic system with unknown dead-zone. The boundedness and convergence properties
of the closed-loop signals are proven using Lyapunov stability theory and Barbalat’s lemma. Numerical results are presented
in order to demonstrate the control system performance. 相似文献
53.
Sliding mode control is a very attractive control scheme because of its robustness against both structured and unstructured uncertainties as well as external disturbances. In this way, it has been widely employed for the dynamic positioning of remotely operated underwater vehicles. Nevertheless, in such situations the discontinuities in the control law must be smoothed out to avoid the undesirable chattering effects. The adoption of properly designed boundary layers has proven effective in completely eliminating chattering, however, leading to an inferior tracking performance. This work describes the development of a dynamic positioning system for remotely operated underwater vehicles. The adopted approach is primarily based on the sliding mode control strategy and enhanced by an adaptive fuzzy algorithm for uncertainty/disturbance compensation. Using the Lyapunov stability theory and Barbalat’s lemma, the boundedness and convergence properties of the closed-loop signals are analytically proven. The performance of the proposed control scheme is also evaluated by means of numerical simulations. 相似文献
54.
Andreas Birk Burkhard Wiggerich Heiko Bülow Max Pfingsthorn Sören Schwertfeger 《Journal of Intelligent and Robotic Systems》2011,64(1):57-76
Several missions with an Unmanned Aerial Vehicle (UAV) in different realistic safety, security, and rescue field tests are
presented. First, results from two safety and security missions at the 2009 European Land Robot Trials (ELROB) are presented.
A UAV in form of an Airrobot AR100-B is used in a reconnaissance and in a camp security scenario. The UAV is capable of autonomous
waypoint navigation using onboard GPS processing. A digital video stream from the vehicle is used to create photo maps—also
known as mosaicking—in real time at the operator station. This mapping is done using an enhanced version of Fourier Mellin
based registration, which turns out to be very fast and robust. Furthermore, results from a rescue oriented scenario at the
2010 Response Robot Evaluation Exercises (RREE) at Disaster City, Texas are presented. The registration for the aerial mosaicking
is supplemented by an uncertainty metric and embedded into Simultaneous Localization and Mapping (SLAM), which further enhances
the photo maps as main mission deliveries. 相似文献
55.
Stefan Klein Josien P. W. Pluim Marius Staring Max A. Viergever 《International Journal of Computer Vision》2009,81(3):227-239
We present a stochastic gradient descent optimisation method for image registration with adaptive step size prediction. The
method is based on the theoretical work by Plakhov and Cruz (J. Math. Sci. 120(1):964–973, 2004). Our main methodological contribution is the derivation of an image-driven mechanism to select proper values for the most
important free parameters of the method. The selection mechanism employs general characteristics of the cost functions that
commonly occur in intensity-based image registration. Also, the theoretical convergence conditions of the optimisation method
are taken into account. The proposed adaptive stochastic gradient descent (ASGD) method is compared to a standard, non-adaptive
Robbins-Monro (RM) algorithm. Both ASGD and RM employ a stochastic subsampling technique to accelerate the optimisation process.
Registration experiments were performed on 3D CT and MR data of the head, lungs, and prostate, using various similarity measures
and transformation models. The results indicate that ASGD is robust to these variations in the registration framework and
is less sensitive to the settings of the user-defined parameters than RM. The main disadvantage of RM is the need for a predetermined
step size function. The ASGD method provides a solution for that issue. 相似文献
56.
Patrick Duessel Christian Gehl Ulrich Flegel Sven Dietrich Michael Meier 《International Journal of Information Security》2017,16(5):475-490
Anomaly detection allows for the identification of unknown and novel attacks in network traffic. However, current approaches for anomaly detection of network packet payloads are limited to the analysis of plain byte sequences. Experiments have shown that application-layer attacks become difficult to detect in the presence of attack obfuscation using payload customization. The ability to incorporate syntactic context into anomaly detection provides valuable information and increases detection accuracy. In this contribution, we address the issue of incorporating protocol context into payload-based anomaly detection. We present a new data representation, called \({c}_n\)-grams, that allows to integrate syntactic and sequential features of payloads in an unified feature space and provides the basis for context-aware detection of network intrusions. We conduct experiments on both text-based and binary application-layer protocols which demonstrate superior accuracy on the detection of various types of attacks over regular anomaly detection methods. Furthermore, we show how \({c}_n\)-grams can be used to interpret detected anomalies and thus, provide explainable decisions in practice. 相似文献
57.
58.
59.
Max Mignotte 《Pattern recognition letters》2011,32(2):359-367
This paper presents a new and simple segmentation method based on the K-means clustering procedure and a two-step process. The first step relies on an original de-texturing procedure which aims at converting the input natural textured color image into a color image, without texture, that will be easier to segment. Once, this de-textured (color) image is estimated, a final segmentation is achieved by a spatially-constrained K-means segmentation. These spatial constraints help the iterative K-means labeling process to succeed in finding an accurate segmentation by taking into account the inherent spatial relationships and the presence of pre-estimated homogeneous textural regions in the input image. This procedure has been successfully applied on the Berkeley image database. The experiments reported in this paper demonstrate that the proposed method is efficient (in terms of visual evaluation and quantitative performance measures) and performs competitively compared to the best existing state-of-the-art segmentation methods recently proposed in the literature. 相似文献
60.
The bootstrap method is a computer intensive statistical method that is widely used in performing nonparametric inference. Categorical data analysis, in particular the analysis of contingency tables, is commonly used in applied field. This work considers nonparametric bootstrap tests for the analysis of contingency tables. There are only a few research papers which exploit this field. The p-values of tests in contingency tables are discrete and should be uniformly distributed under the null hypothesis. The results of this article show that corresponding bootstrap versions work better than the standard tests. Properties of the proposed tests are illustrated and discussed using Monte Carlo simulations. This article concludes with an analytical example that examines the performance of the proposed tests and the confidence interval of the association coefficient. 相似文献