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1.
Three Al-Cr alloys containing additions of Zr and Fe have been fabricated via cold compaction and hot extrusion. The decomposition
of the powder microstructure and the subsequent coarsening during thermomechanical treatment have been studied. Detailed electron
microscopy investigations were performed at different locations of partially extruded billets at 450 °C. The microstructure
of the dead metal zone reflects the effect the induction heating exerts on the as-atomized powder microstructure. In the low
Cr alloys, Al-4Cr-1 Fe and Al-5Cr-2Zr, decomposition of the rapidly solidified microstructure commences at the rich intercellular
network, whereas the microstructure of the Al-6.43Cr-1.67Zr alloy remains relatively unaffected. Within the deformation zone
the precipitation kinetics are affected by the shearing and the temperature rise. The cells and the powder particles are aligned
along the extrusion direction. Precipitation is taking place within the primary segregation-free areas, observed in Al-4Cr-1
Fe and Al-5Cr-2Zr alloys, whereas in the Al-6.43Cr-1.67Zr alloy, decomposition of the powder microstructure starts at the
Cr-rich intermetallic particles. The as-extruded microstructure is fibrous and heterogeneous. The heterogeneity of the as-extruded
microstructure is a result of the microstructural variation observed within different size powder particles and within individual
ones. 相似文献
2.
When a set of rules generates (conflicting) values for a virtual attribute of some tuple, the system must resolve the inconsistency and decide on a unique value that is assigned to that attribute. In most current systems, the conflict is resolved based on criteria that choose one of the rules in the conflicting set and use the value that it generated. There are several applications, however, where inconsistencies of the above form arise, whose semantics demand a different form of resolution. We propose a general framework for the study of the conflict resolution problem, and suggest a variety of resolution criteria, which collectively subsume all previously known solutions. With several new criteria being introduced, the semantics of several applications are captured more accurately than in the past. We discuss how conflict resolution criteria can be specified at the schema or the rule-module level. Finally, we suggest some implementation techniques based on rule indexing, which allow conflicts to be resolved efficiently at compile time, so that at run time only a single rule is processed.An earlier version of this work appeared under the title Conflict Resolution of Rules Assigning Values to Virtual Attributes inProceedings of the 1989 ACM-Sigmod Conference, Portland, OR, June 1989, pp. 205–214.Partially supported by the National Science Foundation under Grant IRI-9157368 (PYI Award) and by grants from DEC, HP, and AT&T.Partially supported by the National Science Foundation under Grant IRI-9057573 (PYI Award), IBM, DEC, and the University of Maryland Institute for Advanced Computer Studies (UMIACS). 相似文献
3.
M. Horstmann M. Lorenz A. Watkowski G. Ioannidis O. Herzog A. King 《New Review of Hypermedia and Multimedia》2013,19(2):141-163
The EU-supported TeDUB (Technical Drawings Understanding for the Blind) project is developing a software system that aims to make technical diagrams accessible to blind and visually impaired people. It consists of two separate modules: one that analyses drawings either semi-automatically or automatically, and one that presents the results of this analysis to blind people and allows them to interact with it. The system is capable of analysing and presenting diagrams from a number of formally defined domains. A diagram enters the system as one of two types: first, diagrams contained in bitmap images, which do not explicitly contain the semantic structure of their content and thus have to be interpreted by the system, and second, diagrams obtained in a semantically enriched format that already yields this structure. The TeDUB system provides blind users with an interface to navigate and annotate these diagrams using a number of input and output devices. Extensive user evaluations have been carried out and an overall positive response from the participants has shown the effectiveness of the approach. 相似文献
4.
Ioannidis JP 《Proteomics. Clinical applications》2011,5(5-6):241-247
Despite over 30,000 publications on proteomics in the last decade, and the accumulation of extensive interesting information on the human proteome in diverse observations, the clinical translation of proteomics to-date has had major setbacks. I review here a roadmap for improving the success rate of clinical proteomics. The roadmap includes steps for improvements that need to be made in analytical tools, discovery, validation, clinical application, and post-clinical application appraisal. It is likely that most if not all of the components that are necessary for clinical success are either readily available, or should be possible to put in place with more rigorous research standards and concerted efforts of the research community, clinicians, and health agencies. Enthusiasm for the clinical impact of proteomics may need to be tempered currently until robust evidence can be obtained, but some clinical successes should eventually be feasible. 相似文献
5.
Yannis Ioannidis Diego Milano Hans-Jörg Schek Heiko Schuldt 《International Journal on Digital Libraries》2008,9(2):101-114
DelosDLMS is a novel digital library management system (DLMS) that has been developed as an integration effort within the
DELOS Network of Excellence, a European Commission initiative funded under its fifth and sixth framework programs. In this
paper, we describe DelosDLMS that takes into account the recommendations of several activities that were initiated by DELOS
including the DELOS vision for digital libraries (DLs). A key aspect of DelosDLMS is its novel generic infrastructure that
allows the generation of digital library systems out of a set of basic system services and DL services in a modular and extensible
way. DL services like feature extraction, visualization, intelligent browsing, media-type-specific indexing, support for multilinguality,
relevance feedback and many others can easily be incorporated or replaced. A further key aspect of DelosDLMS is its robustness
against failures and its scalability for large collections and many parallel user requests. We discuss the current status
of an effort to build DelosDLMS, a Digital Library Management System that integrates in various ways several components developed
by DELOS members and showcases a great variety of functionality that is outlined as part of the DELOS vision. 相似文献
6.
Kostas G. Anagnostakis Michael B. Greenwald Sotiris Ioannidis Angelos D. Keromytis 《International Journal of Information Security》2007,6(6):361-378
Cooperative defensive systems communicate and cooperate in their response to worm attacks, but determine the presence of a worm attack solely on local information. Distributed worm detection and immunization systems track suspicious behavior at multiple cooperating nodes to determine whether a worm attack is in progress. Earlier work has shown that cooperative systems can respond quickly to day-zero worms, while
distributed detection systems allow detectors to be more conservative (i.e., paranoid) about potential attacks because they
manage false alarms efficiently. In this paper we present our investigation into the complex tradeoffs in such systems between
communication costs, computation overhead, accuracy of the local tests, estimation of viral virulence, and the fraction of
the network infected before the attack crests. We evaluate the effectiveness of different system configurations in various
simulations. Our experiments show that distributed algorithms are better able to balance effectiveness against worms and viruses
with reduced cost in computation and communication when faced with false alarms. Furthermore, cooperative, distributed systems
seem more robust against malicious participants in the immunization system than earlier cooperative but non-distributed approaches. 相似文献
7.
Konstantinos Ioannidis Georgios Ch. Sirakoulis Ioannis Andreadis 《Applied Artificial Intelligence》2013,27(8):721-745
A Cellular Automaton-based technique suitable for solving the path planning problem in a distributed robot team is outlined. Real-time path planning is a challenging task that has many applications in the fields of artificial intelligence, moving robots, virtual reality, and agent behavior simulation. The problem refers to finding a collision-free path for autonomous robots between two specified positions in a configuration area. The complexity of the problem increases in systems of multiple robots. More specifically, some distance should be covered by each robot in an unknown environment, avoiding obstacles found on its route to the destination. On the other hand, all robots must adjust their actions in order to keep their initial team formation immutable. Two different formations were tested in order to study the efficiency and the flexibility of the proposed method. Using different formations, the proposed technique could find applications to image processing tasks, swarm intelligence, etc. Furthermore, the presented Cellular Automaton (CA) method was implemented and tested in a real system using three autonomous mobile minirobots called E-pucks. Experimental results indicate that accurate collision-free paths could be created with low computational cost. Additionally, cooperation tasks could be achieved using minimal hardware resources, even in systems with low-cost robots. 相似文献
8.
Evangelos E. Ioannidis 《时间序列分析杂志》2011,32(6):618-630
In this article we propose a new correction for the penalty term of the Akaike’s information criterion (AIC), when it is used in the context of order selection for an autoregressive fit of the spectral density of a stationary time series. The classical AIC penalty term may be viewed as an approximation of an appropriate target quantity. Simulations show that the quality of this approximation strongly depends on the type of autoregressive estimator used, as well as on the discrepancy used. Therefore here we consider the least squares autoregressive estimator and the Whittle discrepancy only. In this context we propose a closed formula correction of the AIC penalty term. We also develop asymptotic theory which justifies this proposal: an asymptotically valid second‐order expansion of a stochastic approximation of the target quantity. This expansion assumes a non‐parametric framework: it does not assume gaussianity of the process and only requires its spectral density to be smooth enough. Simulations show that, as compared to previously introduced corrections, this new correction performs similarly to finite sample information criterion, while they both outperform AIC corrected and AIC. 相似文献
9.
Karayiannis NB Xiong Y Frost JD Wise MS Mizrahi EM 《IEEE transactions on bio-medical engineering》2005,52(4):747-749
This paper presents an approach for improving the accuracy and reliability of motion tracking methods developed for video based on block motion models. This approach estimates the displacement of a block of pixels between two successive frames by minimizing an error function defined in terms of the pixel intensities at these frames. The minimization problem is made analytically tractable by approximating the error function using a second-order Taylor expansion. The improved reliability of the proposed method is illustrated by its application in the extraction of temporal motor activity signals from video recordings of neonatal seizures. 相似文献
10.
Amir Mowla Mehrez Agnaou Tanyakarn Treeratanaphitak Hector M. Budman Nasser M. Abukhdeir Marios A. Ioannidis 《American Institute of Chemical Engineers》2020,66(6):e16959
We quantify the ability of the two-fluid Euler–Euler model to predict the overall gas hold-up during two-phase flow in vertical columns using a combination of experiments and simulations. Gas hold-up in a bubble column and gas hold-up in the less-frequently studied co-current flow are investigated. For homogeneous flow characterized by nearly uniform bubble size, Euler–Euler model predictions are within 10% of the experimental values for both modes of operation, if the bubble diameter supplied as input to the model is the average bubble diameter in the physical system. This also holds true for heterogeneous flow in bubble columns despite the presence of a broad distribution of bubble sizes, if turbulence and bubble swarm effects on momentum exchange between phases are properly accounted for. Swarm corrections adequate for bubble columns, are less successful for co-current heterogeneous flow, for which gas hold-up predictions are least accurate (average error of 22%). 相似文献