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891.
The Individual Haplotyping MFR problem is a computational problem that, given a set of DNA sequence fragment data of an individual,
induces the corresponding haplotypes by dropping the minimum number of fragments. Bafna, Istrail, Lancia, and Rizzi proposed
an algorithm of time O(22k
m
2
n+23k
m
3) for the problem, where m is the number of fragments, n is the number of SNP sites, and k is the maximum number of holes in a fragment. When there are mate-pairs in the input data, the parameter k can be as large as 100, which would make the Bafna-Istrail-Lancia-Rizzi algorithm impracticable. The current paper introduces
a new algorithm PM-MFR of running time
, where k
1 is the maximum number of SNP sites that a fragment covers (k
1 is smaller than n), and k
2 is the maximum number of fragments that cover a SNP site (k
2 is usually about 10). Since the time complexity of the algorithm PM-MFR is not directly related to the parameter k, the algorithm solves the Individual Haplotyping MFR problem with mate-pairs more efficiently and is more practical in real
biological applications.
This research was supported in part by the National Natural Science Foundation of China under Grant Nos. 60433020 and 60773111,
the Program for New Century Excellent Talents in University No. NCET-05-0683, the Program for Changjiang Scholars and Innovative
Research Team in University No. IRT0661, and the Scientific Research Fund of Hunan Provincial Education Department under Grant
No. 06C526. 相似文献
892.
In this paper we describe a general grouping technique to devise faster and simpler approximation schemes for several scheduling
problems. We illustrate the technique on two different scheduling problems: scheduling on unrelated parallel machines with
costs and the job shop scheduling problem. The time complexity of the resulting approximation schemes is always linear in
the number n of jobs, and the multiplicative constant hidden in the O(n) running time is reasonably small and independent of the error ε.
Supported by Swiss National Science Foundation project 200020-109854, “Approximation Algorithms for Machine scheduling Through
Theory and Experiments II”.
A preliminary version of this paper appeared in the Proceedings of ESA’01. 相似文献
893.
Ali Khoshgozaran Ali Khodaei Mehdi Sharifzadeh Cyrus Shahabi 《Knowledge and Information Systems》2008,17(3):265-286
Vector data and in particular road networks are being queried, hosted and processed in many application domains such as in
mobile computing. Many client systems such as PDAs would prefer to receive the query results in unrasterized format without
introducing an overhead on overall system performance and result size. While several general vector data compression schemes
have been studied by different communities, we propose a novel approach in vector data compression which is easily integrated
within a geospatial query processing system. It uses line aggregation to reduce the number of relevant tuples and Huffman
compression to achieve a multi-resolution compressed representation of a road network database. Our experiments performed
on an end-to-end prototype verify that our approach exhibits fast query processing on both client and server sides as well
as high compression ratio.
相似文献
Cyrus ShahabiEmail: |
894.
Given a graph with edges colored Red and Blue, we study the problem of sampling and approximately counting the number of matchings with exactly k
Red edges. We solve the problem of estimating the number of perfect matchings with exactly k
Red edges for dense graphs. We study a Markov chain on the space of all matchings of a graph that favors matchings with k
Red edges. We show that it is rapidly mixing using non-traditional canonical paths that can backtrack. We show that this chain
can be used to sample matchings in the 2-dimensional toroidal lattice of any fixed size ℓ with k
Red edges, where the horizontal edges are Red and the vertical edges are Blue.
An extended abstract appeared in J.R. Correa, A. Hevia and M.A. Kiwi (eds.) Proceedings of the 7th Latin American Theoretical Informatics Symposium, LNCS 3887, pp. 190–201, Springer, 2006.
N. Bhatnagar’s and D. Randall’s research was supported in part by NSF grants CCR-0515105 and DMS-0505505.
V.V. Vazirani’s research was supported in part by NSF grants 0311541, 0220343 and CCR-0515186.
N. Bhatnagar’s and E. Vigoda’s research was supported in part by NSF grant CCR-0455666. 相似文献
895.
Huimin Zhao 《Knowledge and Information Systems》2008,15(3):321-334
In real-world classification problems, different types of misclassification errors often have asymmetric costs, thus demanding cost-sensitive learning methods that attempt to minimize average misclassification cost rather than plain error rate. Instance weighting and post hoc threshold adjusting are two major approaches to cost-sensitive classifier learning. This paper compares the effects of these two approaches on several standard, off-the-shelf classification methods. The comparison indicates that the two approaches lead to similar results for some classification methods, such as Naïve Bayes, logistic regression, and backpropagation neural network, but very different results for other methods, such as decision tree, decision table, and decision rule learners. The findings from this research have important implications on the selection of the cost-sensitive classifier learning approach as well as on the interpretation of a recently published finding about the relative performance of Naïve Bayes and decision trees. 相似文献
896.
We study the problem of segmenting a sequence into k pieces so that the resulting segmentation satisfies monotonicity or unimodality constraints. Unimodal functions can be used
to model phenomena in which a measured variable first increases to a certain level and then decreases. We combine a well-known
unimodal regression algorithm with a simple dynamic-programming approach to obtain an optimal quadratic-time algorithm for
the problem of unimodal k-segmentation. In addition, we describe a more efficient greedy-merging heuristic that is experimentally shown to give solutions
very close to the optimal. As a concrete application of our algorithms, we describe methods for testing if a sequence behaves
unimodally or not. The methods include segmentation error comparisons, permutation testing, and a BIC-based scoring scheme.
Our experimental evaluation shows that our algorithms and the proposed unimodality tests give very intuitive results, for
both real-valued and binary data.
Niina Haiminen received the M.Sc. degree from the University of Helsinki in 2004. She is currently a Graduate Student at the Department
of Computer Science of University of Helsinki, and a Researcher at the Basic Research Unit of Helsinki Institute for Information
Technology. Her research interests include algorithms, bioinformatics, and data mining.
Aristides Gionis received the Ph.D. degree from Stanford University in 2003, and he is currently a Senior Researcher at the Basic Research
Unit of Helsinki Institute for Information Technology. His research experience includes summer internship positions at Bell
Labs, AT&T Labs, and Microsoft Research. His research areas are data mining, algorithms, and databases.
Kari Laasonen received the M.Sc. degree in Theoretical Physics in 1995 from the University of Helsinki. He is currently a Graduate Student
in Computer Science at the University of Helsinki and a Researcher at the Basic Research Unit of Helsinki Institute for Information
Technology. His research is focused on algorithms and data analysis methods for pervasive computing. 相似文献
897.
In this paper, we describe an implementation of use in demonstrating the effectiveness of architectures for real-time multi-agent
systems. The implementation provides a simulation of a simplified RoboCup Search and Rescue environment, with unexpected events,
and includes a simulator for both a real-time operating system and a CPU. We present experimental evidence to demonstrate
the benefit of the implementation in the context of a particular hybrid architecture for multi-agent systems that allows certain
agents to remain fully autonomous, while others are fully controlled by a coordinating agent. In addition, we discuss the
value of the implementation for testing any models for the construction of real-time multi-agent systems and include a comparison
to related work.
相似文献
Robin CohenEmail: |
898.
Learning often occurs through comparing. In classification learning, in order to compare data groups, most existing methods compare either raw instances or learned classification rules against each other. This paper takes a different approach, namely conceptual equivalence, that is, groups are equivalent if their underlying concepts are equivalent while their instance spaces do not necessarily overlap and their rule sets do not necessarily present the same appearance. A new methodology of comparing is proposed that learns a representation of each group’s underlying concept and respectively cross-exams one group’s instances by the other group’s concept representation. The innovation is fivefold. First, it is able to quantify the degree of conceptual equivalence between two groups. Second, it is able to retrace the source of discrepancy at two levels: an abstract level of underlying concepts and a specific level of instances. Third, it applies to numeric data as well as categorical data. Fourth, it circumvents direct comparisons between (possibly a large number of) rules that demand substantial effort. Fifth, it reduces dependency on the accuracy of employed classification algorithms. Empirical evidence suggests that this new methodology is effective and yet simple to use in scenarios such as noise cleansing and concept-change learning. 相似文献
899.
Peter Baumann 《Informatik-Spektrum》2008,31(5):435-450
Zusammenfassung Navigationssysteme, ortsbezogene Suchdienste wie Google Maps, interaktive Augmented-Reality-Spiele, Handy-basierte FindMe-Dienste
– diese wenige Beispiele zeigen bereits, wie direkt oder indirekt raumbezogene Dienste unser Alltagsleben immer mehr durchdringen.
Wir beobachten, wie sich die Nutzung von Geodaten schrittweise vom pers?nlichen Desktop-Geoinformationssystem (GIS) über hausinternen
Zugriff auf die Geodatenbank bis zum Webzugriff durch Clients und Servern unterschiedlicher Provenienz ausweitet (,,Web-GIS“).
Klassische Aufgaben wie Kartenproduktion und Beauskunftung treten dabei gegenüber komplexen, situationsbezogenen Verknüpfungen
von Geo- mit anderen Daten eher in den Hintergrund. Damit geht offensichtlich ein Paradigmenwechsel von der einfachen, passiven
Geodatenbereitstellung via WWW zu funktional komplexeren Geodiensten einher.
Sollen solche Mehrwertdienste offen und flexibel orchestrierbar sein, so müssen Geodaten systemübergreifend ad hoc abgefragt werden k?nnen. Unabdingbar sind dafür offene Standards, nicht nur auf der Ebene von Datenaustauschformaten, sondern
auch bei den Zugriffsdiensten; diese Geoservice-Standardisierung leistet das Open GeoSpatial Consortium (OGC).
Im vorliegenden Beitrag geben wir einen überblick über die Modellierung von Web-basierten Geodiensten auf Basis ausgew?hlter
OGC-Standards. Modellierung bedeutet in diesem Kontext die Gestaltung von Funktionalit?t und Schnittstellen eines potenziell
komplexen Dienstes auf Basis offener Standards und ihrer Basisdienste und -operationen. Diskutiert werden Standards für den
Meta-, Vektor- und Rasterdatenzugriff sowie ein anwendungsorientierter Standard für Sensordaten. 相似文献
900.
Sabine Timpf 《Informatik-Spektrum》2008,31(1):70-74
Zusammenfassung Im Zeitalter der Informationsgesellschaft, so wurde postuliert, spielten r?umliche Distanzen keine Rolle mehr und unsere r?umliche
Mobilit?t n?hme ab. Die Mobilit?t in den letzten Jahren, speziell die Freizeitmobilit?t, hat hingegen zugenommen. Die Bereitstellung
ortsbezogener Dienste – ,,Location-based Services“ – unterstützt und f?rdert dieses Verhalten. 相似文献