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281.
The use of web-based learning and assessment tools is growing in tertiary institutions around the world. To date, very few papers have reported the development and evaluation of a web-based formative assessment tool for postgraduate students. The aim of the present paper was to report on the development and evaluation of an online formative assessment tool for this student group. The web-based formative assessment tool was evaluated by a sample of undergraduate students, postgraduate students and academic staff within a psychology department in order to determine the suitability and sensitivity of the tool. The results of this pilot test suggest that the development of such a tool is both appropriate and feasible for Masters students studying psychology. 相似文献
282.
A new way of devising numerical methods is introduced whose distinctive feature is the computation of a finite element approximation
only in a polyhedral subdomain
D{\mathsf{D}}
of the original, possibly curved-boundary domain. The technique is applied to a discontinuous Galerkin method for the one-dimensional
diffusion-reaction problem. Sharp a priori error estimates are obtained which identify conditions, on the subdomain
D{\mathsf{D}}
and the discretization parameters of the discontinuous Galerkin method, under which the method maintains its original optimal
convergence properties. The error analysis is new even in the case in which
D=W{\mathsf{D}}=\Omega
. It allows to see that the uniform error at any given interval is bounded by an interpolation error associated to the interval
plus a significantly smaller error of a global nature. Numerical results confirming the sharpness of the theoretical results
are displayed. Also, preliminary numerical results illustrating the application of the method to two-dimensional second-order
elliptic problems are shown. 相似文献
283.
Graph constraints were introduced in the area of graph transformation, in connection with the notion of (negative) application conditions, as a form to limit the applicability of transformation rules. However, we believe that graph constraints may also play a significant role in the area of visual software modelling or in the specification and verification of semi-structured documents or websites (i.e. HTML or XML sets of documents). In this sense, after some discussion on these application areas, we concentrate on the problem of how to prove the consistency of specifications based on this kind of constraints. In particular, we present proof rules for two classes of graph constraints and show that our proof rules are sound and (refutationally) complete for each class. In addition, we study clause subsumption in this context as a form to speed up refutation. 相似文献
284.
Ricardo V. de Oliveira Rodrigo A. Ramos Newton G. Bretas 《Control Engineering Practice》2010,18(1):45-54
The main objective of this paper is to relieve the power system engineers from the burden of the complex and time-consuming process of power system stabilizer (PSS) tuning. To achieve this goal, the paper proposes an automatic process for computerized tuning of PSSs, which is based on an iterative process that uses a linear matrix inequality (LMI) solver to find the PSS parameters. It is shown in the paper that PSS tuning can be written as a search problem over a non-convex feasible set. The proposed algorithm solves this feasibility problem using an iterative LMI approach and a suitable initial condition, corresponding to a PSS designed for nominal operating conditions only (which is a quite simple task, since the required phase compensation is uniquely defined). Some knowledge about the PSS tuning is also incorporated in the algorithm through the specification of bounds defining the allowable PSS parameters. The application of the proposed algorithm to a benchmark test system and the nonlinear simulation of the resulting closed-loop models demonstrate the efficiency of this algorithm. 相似文献
285.
Rafael Marín-LópezAuthor Vitae Fernando Pereñíguez Author VitaeGabriel López Author Vitae Alejandro Pérez-Méndez Author Vitae 《Computer Standards & Interfaces》2011,33(5):494-504
Kerberos is a well-known standard protocol which is becoming one of the most widely deployed for authentication and key distribution in application services. However, whereas service providers use the protocol to control their own subscribers, they do not widely deploy Kerberos infrastructures to handle subscribers coming from foreign domains, as happens in network federations. Instead, the deployment of Authentication, Authorization and Accounting (AAA) infrastructures has been preferred for that operation. Thus, the lack of a correct integration between these infrastructures and Kerberos limits the service access only to service provider's subscribers. To avoid this limitation, we design an architecture which integrates a Kerberos pre-authentication mechanism, based on the use of the Extensible Authentication Protocol (EAP), and advanced authorization, based on the standards SAML and XACML, to link the end user authentication and authorization performed through an AAA infrastructure with the delivery of Kerberos tickets in the service provider's domain. We detail the interfaces, protocols, operation and extensions required for our solution. Moreover, we discuss important aspects such as the implications on existing standards. 相似文献
286.
Francisco Almeida Domingo Giménez Jose J. López-Espín 《The Journal of supercomputing》2011,58(3):292-301
This paper presents a parameterized shared-memory scheme for parameterized metaheuristics. The use of a parameterized metaheuristic
facilitates experimentation with different metaheuristics and hybridation/combinations to adapt them to the particular problem
we are working with. Due to the large number of experiments necessary for the metaheuristic selection and tuning, parallelism
should be used to reduce the execution time. To obtain parallel versions of the metaheuristics and to adapt them to the characteristics
of the parallel system, a unified parameterized shared-memory scheme is developed. Given a particular computational system
and fixed parameters for the sequential metaheuristic, the appropriate selection of parameters in the unified parallel scheme
eases the development of parallel efficient metaheuristics. 相似文献
287.
Mauri Aparecido de Oliveira 《Neural computing & applications》2011,20(5):687-701
The objective of this article is to find out the influence of the parameters of the ARIMA-GARCH models in the prediction of
artificial neural networks (ANN) of the feed forward type, trained with the Levenberg–Marquardt algorithm, through Monte Carlo
simulations. The paper presents a study of the relationship between ANN performance and ARIMA-GARCH model parameters, i.e.
the fact that depending on the stationarity and other parameters of the time series, the ANN structure should be selected
differently. Neural networks have been widely used to predict time series and their capacity for dealing with non-linearities
is a normally outstanding advantage. However, the values of the parameters of the models of generalized autoregressive conditional
heteroscedasticity have an influence on ANN prediction performance. The combination of the values of the GARCH parameters
with the ARIMA autoregressive terms also implies in ANN performance variation. Combining the parameters of the ARIMA-GARCH
models and changing the ANN’s topologies, we used the Theil inequality coefficient to measure the prediction of the feed forward
ANN. 相似文献
288.
Paulo Anselmo da Mota Silveira Neto Ivan do Carmo Machado John D. McGregorEduardo Santana de Almeida Silvio Romero de Lemos Meira 《Information and Software Technology》2011,53(5):407-423
Context
In software development, Testing is an important mechanism both to identify defects and assure that completed products work as specified. This is a common practice in single-system development, and continues to hold in Software Product Lines (SPL). Even though extensive research has been done in the SPL Testing field, it is necessary to assess the current state of research and practice, in order to provide practitioners with evidence that enable fostering its further development.Objective
This paper focuses on Testing in SPL and has the following goals: investigate state-of-the-art testing practices, synthesize available evidence, and identify gaps between required techniques and existing approaches, available in the literature.Method
A systematic mapping study was conducted with a set of nine research questions, in which 120 studies, dated from 1993 to 2009, were evaluated.Results
Although several aspects regarding testing have been covered by single-system development approaches, many cannot be directly applied in the SPL context due to specific issues. In addition, particular aspects regarding SPL are not covered by the existing SPL approaches, and when the aspects are covered, the literature just gives brief overviews. This scenario indicates that additional investigation, empirical and practical, should be performed.Conclusion
The results can help to understand the needs in SPL Testing, by identifying points that still require additional investigation, since important aspects regarding particular points of software product lines have not been addressed yet. 相似文献289.
J. L. Martinez W. A. R. J. Weerakkody W. A. C. Fernando G. Fernandez-Escribano H. Kalva A. Garrido 《The Visual computer》2009,25(1):69-82
Distributed Video Coding (DVC) has been proposed for increasingly new application domains. This rise is apparently motivated
by the very attractive features of its flexibility for building very low cost video encoders and the very high built-in error
resilience when applied over noisy communication channels. Yet, the compression efficiency of DVC is notably lagging behind
the state-of-the-art in video coding and compression, H.264/AVC in particular. In this context, a novel coding solution for
DVC is presented in this paper, which promises to improve its rate-distortion (RD) performance towards the state-of-the-art.
Here, Turbo Trellis Coded Modulation (TTCM), with its attractive coding gain in channel coding, is utilized and its resultant
impact in both pixel domain and transform domain DVC framework is discussed herein. Simulations have shown a significant gain
in the RD performance when compared with the state-of-the-art Turbo coding based DVC implementations.
相似文献
A. GarridoEmail: |
290.
Alvaro E. Cuno Parari Claudio Esperança Antonio A. F. Oliveira 《The Visual computer》2009,25(10):911-922
This work presents methods for deforming meshes in a shape-sensitive way using Moving Least Squares (MLS) optimization. It
extends an approach for deforming space (Cuno et al. in Proceedings of the 27th Computer Graphics International Conference,
pp. 115–122, 2007) by showing how custom distance metrics may be used to achieve deformations which preserve the overall mesh shape. Several
variant formulations are discussed and demonstrated, including the use of geodesic distances, distances constrained to paths
contained in the mesh, the use of skeletons, and a reformulation of the MLS scheme which makes it possible to affect the bending
behavior of the deformation. Finally, aspects of the implementation of these techniques in parallel architectures such as
GPUs (graphics processing units) are described and compared with CPU-only implementations. 相似文献