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91.
Demetrios Zeinalipour-Yazti Zografoula Vagena Vana Kalogeraki Dimitrios Gunopulos Vassilis J. Tsotras Michail Vlachos Nick Koudas Divesh Srivastava 《Computer Networks》2009,53(9):1431-1449
In this paper, we present an algorithm for finding the k highest-ranked (or Top-k) answers in a distributed network. A Top-K query returns the subset of most relevant answers, in place of all answers, for two reasons: (i) to minimize the cost metric that is associated with the retrieval of all answers; and (ii) to improve the recall and the precision of the answer-set, such that the user is not overwhelmed with irrelevant results. Our study focuses on multi-hop distributed networks in which the data is accessible by traversing a network of nodes. Such a setting captures very well the computation framework of emerging Sensor Networks, Peer-to-Peer Networks and Vehicular Networks. We present the Threshold Join Algorithm (TJA), an efficient algorithm that utilizes a non-uniform threshold on the queried attribute in order to minimize the transfer of data when a query is executed. Additionally, TJA resolves queries in the network rather than in a centralized fashion which further minimizes the consumption of bandwidth and delay. We performed an extensive experimental evaluation of our algorithm using a real testbed of 75 workstations along with a trace-driven experimental methodology. Our results indicate that TJA requires an order of magnitude less communication than the state-of-the-art, scales well with respect to the parameter k and the network topology. 相似文献
92.
rfid has already found its way into a variety of large scale applications and arguably it is already one of the most successful technologies in the history of computing. Beyond doubt, rfid is an effective automatic identification technology for a variety of objects including natural, manufactured and handmade artifacts; humans and other species; locations; and increasingly media content and mobile services. In this survey we consider developments towards establishing rfid as the cost-effective technical solution for the development of open, shared, universal pervasive computing infrastructures and look ahead to its future. In particular, we discuss the ingredients of current large scale applications; the role of network services to provide complete systems; privacy and security implications; and how rfid is helping prototype emerging pervasive computing applications. We conclude by identifying common trends in the new applications of rfid and ask questions related to sustainable universal deployment of this technology. 相似文献
93.
Vassilis Kostakos Tom Nicolai Eiko Yoneki Eamonn O’Neill Holger Kenn Jon Crowcroft 《Personal and Ubiquitous Computing》2009,13(5):355-364
The increasing popularity of mobile computing devices has allowed for new research and application areas. Specifically, urban
areas exhibit an elevated concentration of such devices enabling potential ad-hoc co-operation and sharing of resources among
citizens. Here, we argue that people, architecture and technology together provide the infrastructure for these applications
and an understanding of this infrastructure is important for effective design and development. We focus on describing the
metrics for describing this infrastructure and elaborate on a set of observation, analysis and simulation methods for capturing,
deriving and utilising those metrics.
相似文献
Vassilis KostakosEmail: |
94.
Can we do without GUIs? Gesture and speech interaction with a patient information system 总被引:2,自引:1,他引:1
Eamonn?O’NeillEmail author Manasawee?Kaenampornpan Vassilis?Kostakos Andrew?Warr Dawn?Woodgate 《Personal and Ubiquitous Computing》2006,10(5):269-283
We have developed a gesture input system that provides a common interaction technique across mobile, wearable and ubiquitous computing devices of diverse form factors. In this paper, we combine our gestural input technique with speech output and test whether or not the absence of a visual display impairs usability in this kind of multimodal interaction. This is of particular relevance to mobile, wearable and ubiquitous systems where visual displays may be restricted or unavailable. We conducted the evaluation using a prototype for a system combining gesture input and speech output to provide information to patients in a hospital Accident and Emergency Department. A group of participants was instructed to access various services using gestural inputs. The services were delivered by automated speech output. Throughout their tasks, these participants could see a visual display on which a GUI presented the available services and their corresponding gestures. Another group of participants performed the same tasks but without this visual display. It was predicted that the participants without the visual display would make more incorrect gestures and take longer to perform correct gestures than the participants with the visual display. We found no significant difference in the number of incorrect gestures made. We also found that participants with the visual display took longer than participants without it. It was suggested that for a small set of semantically distinct services with memorable and distinct gestures, the absence of a GUI visual display does not impair the usability of a system with gesture input and speech output. 相似文献
95.
Vrahatis Michael N. Magoulas George D. Plagianakos Vassilis P. 《Neural Processing Letters》2000,12(2):159-170
A mathematical framework for the convergence analysis of the well-known Quickprop method is described. Furthermore, we propose a modification of this method that exhibits improved convergence speed and stability, and, at the same time, alleviates the use of heuristic learning parameters. Simulations are conducted to compare and evaluate the performance of the new modified Quickprop algorithm with various popular training algorithms. The results of the experiments indicate that the increased convergence rates achieved by the proposed algorithm, affect by no means its generalization capability and stability. 相似文献
96.
Wang J Athitsos V Sclaroff S Betke M 《IEEE transactions on pattern analysis and machine intelligence》2008,30(3):477-492
This paper proposes a method for detecting object classes that exhibit variable shape structure in heavily cluttered images. The term "variable shape structure" is used to characterize object classes in which some shape parts can be repeated an arbitrary number of times, some parts can be optional, and some parts can have several alternative appearances. Hidden State Shape Models (HSSMs), a generalization of Hidden Markov Models (HMMs), are introduced to model object classes of variable shape structure using a probabilistic framework. A polynomial inference algorithm automatically determines object location, orientation, scale and structure by finding the globally optimal registration of model states with the image features, even in the presence of clutter. Experiments with real images demonstrate that the proposed method can localize objects of variable shape structure with high accuracy. For the task of hand shape localization and structure identification, the proposed method is significantly more accurate than previously proposed methods based on chamfer-distance matching. Furthermore, by integrating simple temporal constraints, the proposed method gains speed-ups of more than an order of magnitude, and produces highly accurate results in experiments on non-rigid hand motion tracking. 相似文献
97.
A novel method of improving the spatial resolution of scanned images, by means of neural networks, is presented in this paper.
Images of different resolution, originating from scanner, successively train a neural network, which learns to improve resolution
from 25 to 50 pixels-per-inch (ppi), then from 100 to 200 ppi and finally, from 50 to 100 ppi. Thus, the network is provided
with consistent knowledge regarding the point spread function (PSF) of the scanner, whilst it gains the generalization ability
to reconstruct finer resolution images unfamiliar to it. The novelty of the proposed image-resolution-enhancement technique
lies in the successive training of the neural structure with images of increasing resolution. Comparisons with the image scanned
at 400 ppi demonstrate the superiority of our method to conventional interpolation techniques. 相似文献
98.
Vassilis S. Kodogiannis 《International journal of systems science》2013,44(3):149-162
Unmanned underwater vehicles (UUVs) typically operate in uncertain and changing environments. Since the dynamics of UUVs are highly nonlinear and their hydrodynamic coefficients vary with different operating conditions, a high-performance control system of a UUV is needed to have the capacities of learning and adaptation to the variations in the UUV's dynamics. This paper presents the utilization of an adaptive neuro-control scheme as a controller for controlling a UUV in six degrees of freedom. No prior offline training phase and no explicit knowledge of the structure of the vehicle are required, and the proposed scheme exploits the advantages of both neural network control and adaptive control. Asymptotic convergence of the UUV's tracking errors and stability of the presented control system is guaranteed on the basis of the Lyapunov theory. In this paper, neural network architectures based on radial basis functions and multilayer structures have been used to evaluate the performance of the adaptive controller via computer simulation. 相似文献
99.
The Maximum Weight Independent Set (MWIS) problem on graphs with vertex weights asks for a set of pairwise nonadjacent vertices of maximum total weight. Being one of the most investigated and most important problems on graphs, it is well known to be -complete and hard to approximate. The complexity of MWIS is open for hole-free graphs (i.e., graphs without induced subgraphs isomorphic to a chordless cycle of length at least five). By applying a combination of clique separator and modular decomposition, we obtain a polynomial time solution of MWIS for hole- and co-chair-free graphs (the co-chair consists of five vertices four of which form a clique minus one edge – a diamond – and the fifth has degree one and is adjacent to one of the degree two vertices of the diamond). 相似文献
100.