全文获取类型
收费全文 | 42180篇 |
免费 | 2396篇 |
国内免费 | 59篇 |
学科分类
工业技术 | 44635篇 |
出版年
2023年 | 359篇 |
2022年 | 339篇 |
2021年 | 888篇 |
2020年 | 756篇 |
2019年 | 691篇 |
2018年 | 1545篇 |
2017年 | 1546篇 |
2016年 | 1601篇 |
2015年 | 1130篇 |
2014年 | 1457篇 |
2013年 | 2800篇 |
2012年 | 2455篇 |
2011年 | 2244篇 |
2010年 | 1784篇 |
2009年 | 1583篇 |
2008年 | 1846篇 |
2007年 | 1636篇 |
2006年 | 1217篇 |
2005年 | 1018篇 |
2004年 | 952篇 |
2003年 | 834篇 |
2002年 | 751篇 |
2001年 | 485篇 |
2000年 | 483篇 |
1999年 | 642篇 |
1998年 | 3428篇 |
1997年 | 2058篇 |
1996年 | 1337篇 |
1995年 | 778篇 |
1994年 | 661篇 |
1993年 | 651篇 |
1992年 | 213篇 |
1991年 | 230篇 |
1990年 | 226篇 |
1989年 | 220篇 |
1988年 | 197篇 |
1987年 | 175篇 |
1986年 | 192篇 |
1985年 | 219篇 |
1984年 | 190篇 |
1983年 | 137篇 |
1982年 | 166篇 |
1981年 | 183篇 |
1980年 | 165篇 |
1979年 | 132篇 |
1978年 | 121篇 |
1977年 | 209篇 |
1976年 | 438篇 |
1975年 | 94篇 |
1973年 | 84篇 |
排序方式: 共有10000条查询结果,搜索用时 640 毫秒
991.
Christian Bessiere Stéphane Cardon Romuald Debruyne Christophe Lecoutre 《Constraints》2011,16(1):25-53
In this paper, we propose two original and efficient approaches for enforcing singleton arc consistency. In the first one,
the data structures used to enforce arc consistency are shared between all subproblems where a domain is reduced to a singleton.
This new algorithm is not optimal but it requires far less space and is often more efficient in practice than the optimal
algorithm SAC-Opt. In the second approach, we perform several runs of a greedy search (where at each step, arc consistency
is maintained), possibly detecting the singleton arc consistency of several values in one run. It is an original illustration
of applying inference (i.e., establishing singleton arc consistency) by search. Using a greedy search allows benefiting from
the incrementality of arc consistency, learning relevant information from conflicts and, potentially finding solution(s) during
the inference process. We present extensive experiments that show the benefit of our two approaches. 相似文献
992.
Adaptive IPTV services based on a novel IP Multimedia Subsystem 总被引:1,自引:1,他引:0
Julien Arnaud Daniel Négru Mamadou Sidibé Julien Pauty Harilaos Koumaras 《Multimedia Tools and Applications》2011,55(2):333-352
Heterogeneous communication devices are emerging and changing the way of communication. Innovative multimedia applications
are now accessible through these embedded systems. The 3GPP IP Multimedia Subsystem (IMS) provides a basic architecture framework
for the Next Generation Network (NGN) supporting the convergence platform for service provisioning in heterogeneous networks.
ETSI TISPAN standardization effort focuses on delivering IPTV services on such platform. Nevertheless, IPTV on IMS standardization
suffers from a lack of efficient user-centric network management mechanisms as the end-user may consume IPTV service from
different access networks, on different mobile devices, at anytime. User’s Perceived Quality of Service (PQoS) or Quality
of Experience (QoE) of IPTV service may also suffer from wireless access network impairments. This paper introduces new functionalities
in IPTV over IMS architecture which optimize satisfaction of the end-user and resource utilization of the operator’s networks.
A context-sensitive User Profile (UP) model is used to deliver IPTV streams adapted to the user’s environment. In order to
optimize the operator network usage, the impact of spatiotemporal dynamics of the video content on the deduced perceptual
quality is considered. A Multimedia Content Management System (MCMS) is proposed to perform dynamic cross-layer adaptation
of the IPTV stream based on PQoS measurements at the end-user side. 相似文献
993.
Even though there is abundant literature on successful cases of organizations applying knowledge management (KM) measures,
many KM initiatives have failed to achieve their knowledge and business goals. In order to foster decisions about the design
of such initiatives, information is required on success factors and barriers when selecting KM measures. Multi agent-based
simulation (MABS) is suggested as instrument to investigate potential effects of KM measures on dependent variables such as
sharing of knowledge in organizations or business performance. For such a simulation, the concept of knowledge sharing, influencing
factors and their impact on business and knowledge goals are modeled based on an extensive multi-disciplinary literature survey.
An extensive domain model is operationalized in a simulation model which is then further simplified and implemented in a MABS
tool used for a series of experiments contrasting results with/without KM measures, specifically skill and experience management.
Skill management is found highly sensitive with respect to conditions of application and has no significant impact on knowledge
or business goals. Experience management positively impacts knowledge and business goals. Personal documentation leads to
specialist, project debriefings to generalist knowledge workers. Finally, the paper discusses the simulation’s limitations
and further areas of application. 相似文献
994.
Kalou Cabrera Castillos Frédéric Dadeau Jacques Julliand 《International Journal on Software Tools for Technology Transfer (STTT)》2011,13(5):431-448
We present in this article a way to produce test suites applied to the POSIX mini-challenge based on a behavioral model of
a file system manager written in UML/OCL. We illustrate the limitations of a fully automated test generation approach, which
justifies the use of test scenarios as a complement to a functional testing approach. Scenarios are expressed through regular
expressions describing sequences of operations, possibly punctuated by intermediate states that have to be reached by the
execution of the model. Scenarios are unfolded into extended sequences of operations that are played on the model using symbolic
animation techniques. We experimented our approach by testing the conformance of two different file systems w.r.t. the POSIX
standard: a recent Linux distribution and a customized Java implementation of POSIX used to evaluate the relevance of our
approach and its complementarity with a structural test generation approach. 相似文献
995.
996.
Antonio Fernández Anta José Luis López-Presa M. Araceli Lorenzo Pilar Manzano Juan Martinez-Romo Alberto Mozo Christopher Thraves 《Theory of Computing Systems》2011,48(1):1-22
In this paper we generalize the Continuous Adversarial Queuing Theory (CAQT) model (Blesa et al. in MFCS, Lecture Notes in
Computer Science, vol. 3618, pp. 144–155, 2005) by considering the possibility that the router clocks in the network are not synchronized. We name the new model Non Synchronized
CAQT (NSCAQT). Clearly, this new extension to the model only affects those scheduling policies that use some form of timing.
In a first approach we consider the case in which although not synchronized, all clocks run at the same speed, maintaining
constant differences. In this case we show that all universally stable policies in CAQT that use the injection time and the
remaining path to schedule packets remain universally stable. These policies include, for instance, Shortest in System (SIS)
and Longest in System (LIS). Then, we study the case in which clock differences can vary over time, but the maximum difference
is bounded. In this model we show the universal stability of two families of policies related to SIS and LIS respectively
(the priority of a packet in these policies depends on the arrival time and a function of the path traversed). The bounds
we obtain in this case depend on the maximum difference between clocks. This is a necessary requirement, since we also show
that LIS is not universally stable in systems without bounded clock difference. We then present a new policy that we call
Longest in Queues (LIQ), which gives priority to the packet that has been waiting the longest in edge queues. This policy
is universally stable and, if clocks maintain constant differences, the bounds we prove do not depend on them. To finish,
we provide with simulation results that compare the behavior of some of these policies in a network with stochastic injection
of packets. 相似文献
997.
The localization of the components of an object near to a device before obtaining the real interaction is usually determined by means of a proximity measurement to the device of the object’s features. In order to do this efficiently, hierarchical decompositions are used, so that the features of the objects are classified into several types of cells, usually rectangular.In this paper we propose a solution based on the classification of a set of points situated on the device in a little-known spatial decomposition named tetra-tree. Using this type of spatial decomposition gives us several quantitative and qualitative properties that allow us a more realistic and intuitive visual interaction, as well as the possibility of selecting inaccessible components. These features could be used in virtual sculpting or accessibility tasks.In order to show these properties we have compared an interaction system based on tetra-trees to one based on octrees. 相似文献
998.
999.
Sónia M. Almeida-Luz Miguel A. Vega-Rodríguez Juan A. Gómez-Púlido Juan M. Sánchez-Pérez 《Applied Soft Computing》2011,11(1):410-427
In this work we present two new approaches to solve the location management problem, respectively, based on the location areas and the reporting cells strategies. The location management problem corresponds to the management of the network configuration with the objective of minimizing the costs involved. We use the differential evolution algorithm to find the best configuration for the location areas and the reporting cells strategies, which principally considers the location update and paging costs. With this work we want to define the best values to the differential evolution configuration, using test networks and also realistic networks, as well as compare our results with the ones obtained by other authors. These two new approaches applied to this problem have given us very good results, when compared with those obtained by other authors. 相似文献
1000.