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51.
Requirements engineering (RE) research often ignores or presumes a uniform nature of the context in which the system operates.
This assumption is no longer valid in emerging computing paradigms, such as ambient, pervasive and ubiquitous computing, where
it is essential to monitor and adapt to an inherently varying context. Besides influencing the software, context may influence
stakeholders’ goals and their choices to meet them. In this paper, we propose a goal-oriented RE modeling and reasoning framework
for systems operating in varying contexts. We introduce contextual goal models to relate goals and contexts; context analysis to refine contexts and identify ways to verify them; reasoning techniques to derive requirements reflecting the context and
users priorities at runtime; and finally, design time reasoning techniques to derive requirements for a system to be developed
at minimum cost and valid in all considered contexts. We illustrate and evaluate our approach through a case study about a
museum-guide mobile information system. 相似文献
52.
CAD based shape optimization for gas turbine component design 总被引:1,自引:0,他引:1
Djordje Brujic Mihailo Ristic Massimiliano Mattone Paolo Maggiore Gian Paolo De Poli 《Structural and Multidisciplinary Optimization》2010,41(4):647-659
In order to improve product characteristics, engineering design makes increasing use of Robust Design and Multidisciplinary
Design Optimisation. Common to both methodologies is the need to vary the object’s shape and to assess the resulting change
in performance, both executed within an automatic loop. This shape change can be realised by modifying the parameter values
of a suitably parameterised Computer Aided Design (CAD) model. This paper presents the adopted methodology and the achieved
results when performing optimisation of a gas turbine disk. Our approach to hierarchical modelling employing design tables
is presented, with methods to ensure satisfactory geometry variation by commercial CAD systems. The conducted studies included
stochastic and probabilistic design optimisation. To solve the multi-objective optimisation problem, a Pareto optimum criterion
was used. The results demonstrate that CAD centric approach enables significant progress towards automating the entire process
while achieving a higher quality product with the reduced susceptibility to manufacturing imperfections. 相似文献
53.
We consider incompressible flow problems with defective boundary conditions prescribing only the net flux on some inflow and outflow sections of the boundary. As a paradigm for such problems, we simply refer to Stokes flow. After a brief review of the problem and of its well posedness, we discretize the corresponding variational formulation by means of finite elements and looking at the boundary conditions as constraints, we exploit a penalty method to account for them. We perform the analysis of the method in terms of consistency, boundedness and stability of the discrete bilinear form and we show that the application of the penalty method does not affect the optimal convergence properties of the finite element discretization. Since the additional terms introduced to account for the defective boundary conditions are non-local, we also analyze the spectral properties of the equivalent algebraic formulation and we exploit the analysis to set up an efficient solution strategy. In contrast to alternative discretization methods based on Lagrange multipliers accounting for the constraints on the boundary, the present scheme is particularly effective because it only mildly affects the structure and the computational cost of the numerical approximation. Indeed, it does not require neither multipliers nor sub-iterations or additional adjoint problems with respect to the reference problem at hand. 相似文献
54.
Paolo Cotogno 《Minds and Machines》2009,19(3):391-405
Hypercomputation—the hypothesis that Turing-incomputable objects can be computed through infinitary means—is ineffective,
as the unsolvability of the halting problem for Turing machines depends just on the absence of a definite value for some paradoxical
construction; nature and quantity of computing resources are immaterial. The assumption that the halting problem is solved
by oracles of higher Turing degree amounts just to postulation; infinite-time oracles are not actually solving paradoxes,
but simply assigning them conventional values. Special values for non-terminating processes are likewise irrelevant, since
diagonalization can cover any amount of value assignments. This should not be construed as a restriction of computing power:
Turing’s uncomputability is not a ‘barrier’ to be broken, but simply an effect of the expressive power of consistent programming
systems. 相似文献
55.
Paolo Vicig 《Minds and Machines》2016,26(3):303-305
Constrained coherence is compared to coherence and its role in the behavioural interpretation of coherence is discussed. The equivalence of these two notions is proven for coherent conditional previsions, showing that the same course of reasoning applies to several similar concepts developed in the realm of imprecise probability theory. 相似文献
56.
A novel frequency–based definition of dynamic compliance is introduced within the framework of H ∞ –norm based structural dynamics in the presence of load uncertainties. The system itself is supposed to depend on a vector of design parameters with respect to which an optimal design is pursued. A three-step worst-case-scenario is then developed that finds the minimum-compliance structure capable of accounting for the entire norm–bounded load sets. Once the problem is initialized, the current worst load is found that is used as input to the minimization of the structural compliance and the procedure is repeated until convergence. Numerical examples are eventually proposed that deal with viscoelastic beams discretized via a truly–mixed finite–element scheme. 相似文献
57.
Contrast-enhanced ultrasound (CEUS) has recently become an important technology for lesion detection and characterization in cancer diagnosis. CEUS is used to investigate the perfusion kinetics in tissue over time, which relates to tissue vascularization. In this paper we present a pipeline that enables interactive visual exploration and semi-automatic segmentation and classification of CEUS data.For the visual analysis of this challenging data, with characteristic noise patterns and residual movements, we propose a robust method to derive expressive enhancement measures from small spatio-temporal neighborhoods. We use this information in a staged visual analysis pipeline that leads from a more local investigation to global results such as the delineation of anatomic regions according to their perfusion properties. To make the visual exploration interactive, we have developed an accelerated framework based on the OpenCL library, that exploits modern many-cores hardware. Using our application, we were able to analyze datasets from CEUS liver examinations, being able to identify several focal liver lesions, segment and analyze them quickly and precisely, and eventually characterize them. 相似文献
58.
Data-Intensive Web Sites: Design and Maintenance 总被引:1,自引:0,他引:1
59.
Seng KY Figueroa-Masot X Folch A Vicini P 《Computer methods and programs in biomedicine》2007,85(3):220-228
A new approach for objectively analyzing the aggregation of acetylcholine receptors (AChRs) through power spectrum analysis derived from fast Fourier transform (FFT) of images has been developed. Presently, detection of AChR aggregates at neuromuscular junctions is not easily accomplished. Though the formation of AChR clusters results in periodic gray-level variations that differ with time, no study reporting their correlation with frequency information in the Fourier domain for aggregates' detection purposes exists. To this end, we processed time-lapse images of AChR aggregates' formation on murine myotubes to extract peak values of power spectra. To validate interpretation of the Fourier spectra analysis, a computer routine was developed to semi-automatically count AChR aggregates. We found: (1) logarithmic maxima of Fourier spectra correlated significantly with experimentation time; (2) cluster count correlated significantly with time only after clusters were discernable from images, signifying that this method heavily depended on definitive growth data and thresholding values; (3) exponents of Fourier maxima versus time and cluster count versus time profiles during this phase compared favorably, indicating that both methods were analyzing identical cluster growth rates. Our observations suggest that analysis via FFT power spectrum is sensitive and robust enough to automatically quantify AChR aggregates. 相似文献
60.
The multimod application framework: a rapid application development tool for computer aided medicine 总被引:1,自引:0,他引:1
Viceconti M Zannoni C Testi D Petrone M Perticoni S Quadrani P Taddei F Imboden S Clapworthy G 《Computer methods and programs in biomedicine》2007,85(2):138-151
This paper describes a new application framework (OpenMAF) for rapid development of multimodal applications in computer-aided medicine. MAF applications are multimodal in data, in representation, and in interaction. The framework supports almost any type of biomedical data, including DICOM datasets, motion-capture recordings, or data from computer simulations (e.g. finite element modeling). The interactive visualization approach (multimodal display) helps the user interpret complex datasets, providing multiple representations of the same data. In addition, the framework allows multimodal interaction by supporting the simultaneous use of different input-output devices like 3D trackers, stereoscopic displays, haptics hardware and speech recognition/synthesis systems. The Framework has been designed to run smoothly even on limited power computers, but it can take advantage of all hardware capabilities. The Framework is based on a collection of portable libraries and it can be compiled on any platform that supports OpenGL, including Windows, MacOS X and any flavor of Unix/linux. 相似文献