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71.
An extension of the Cauer ladder development for synthesizing singly terminated filters with symmetric and asymmetric responses is presented. Basically, a driving‐point immittance including reactive constant elements is carried out in such a way that provides the transmission zeros. The reactive constant elements are introduced into the synthesis for two reasons. The first is to consider the possibility of the asymmetric position of transmission zeros in the real frequency axis. The second one is to obtain canonical forms, i.e. networks with the minimum number of elements in the case of symmetrical responses. To validate the proposed method, a filter with asymmetrical response has been synthesized, comparing different topologies for its use in multiplexers. This fact is illustrated with a Ku‐band elliptic response diplexer designed in H‐plane rectangular waveguide. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009. 相似文献
72.
The development and computational implementation, on a multibody dynamics environment, of a constitutive relation to model
bushing elements associated with mechanical joints used in the models of road and rail vehicles is presented here. These elements
are used to eliminate vibrations in vehicles, due to road irregularities, to allow small misalignment of axes, to reduce noise
from the transmission, or to decrease wear of the mechanical joints. Bushings are made of a special rubber, used generally
in energy dissipation, which presents a nonlinear viscoelastic relationship between the forces and moments and their corresponding
displacements and rotations. In the methodology proposed here a finite element model of the bushing is developed in the framework
of the finite element code ABAQUS to obtain the constitutive relations of displacement/rotation versus force/moment for different
loading cases. The bushing is modeled in a multibody code as a nonlinear restrain that relates the relative displacements
between the bodies connected with the joint reaction forces, and it is represented by a matrix constitutive relation. The
basic ingredients of the multibody model are the same vectors and points relations used to define kinematic constraints in
any multibody formulation. One particular, and relevant, characteristic of the formulation now presented is its ability to
represent standard kinematic joints, clearance, and bushing joints just by defining appropriate constitutive relations. Spherical,
revolution, cylindrical, and translational bushing joints are modeled, implemented, and demonstrated through the simulation
of two multibody models of a road vehicle, one with perfect kinematic joints for the suspension sub-systems, and other with
bushing joints. The tests conducted include an obstacle avoidance maneuver and a vehicle riding over bumps. It is shown that
the bushing models for vehicle multibody models proposed here are accurate and computationally efficient so that they can
be included in the vehicle models leading reliable simulations. 相似文献
73.
Ortega-Cabezas Pedro Miguel Colmenar-Santos Antonio Borge-Diez David Blanes-Peiró Jorge Juan Higuera-Pérez Jorge Alcaide Eric 《Software Quality Journal》2022,30(3):687-728
Software Quality Journal - The number of electronic control units (ECU) installed in vehicles is increasingly high. Manufacturers must improve the software quality and reduce cost by proposing... 相似文献
74.
Sensitive and Reversible Detection of Methanol and Water Vapor by In Situ Electrochemically Grown CuBTC MOFs on Interdigitated Electrodes 下载免费PDF全文
Sumit Sachdeva Manjunath R. Venkatesh Brahim El Mansouri Jia Wei Andre Bossche Freek Kapteijn Guo Qi Zhang Jorge Gascon Louis C. P. M. de Smet Ernst J. R. Sudhölter 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(29)
The in situ electrochemical growth of Cu benzene‐1,3,5‐tricarboxylate (CuBTC) metal–organic frameworks, as an affinity layer, directly on custom‐fabricated Cu interdigitated electrodes (IDEs) is described, acting as a transducer. Crystalline 5–7 µm thick CuBTC layers are grown on IDEs consisting of 100 electrodes with a width and a gap of both 50 µm and a height of 6–8 µm. These capacitive sensors are exposed to methanol and water vapor at 30 °C. The affinities show to be completely reversible with higher affinity toward water compared to methanol. For exposure to 1000 ppm methanol, a fast response is observed with a capacitance change of 5.57 pF at equilibrium. The capacitance increases in time followed diffusion‐controlled kinetics (k = 2.9 mmol s?0.5 g?1CuBTC). The observed capacitance change with methanol concentration follows a Langmuir adsorption isotherm, with a value for the equilibrium affinity K e = 174.8 bar?1. A volume fraction f MeOH = 0.038 is occupied upon exposure to 1000 ppm of methanol. The thin CuBTC affinity layer on the Cu‐IDEs shows fast, reversible, and sensitive responses to methanol and water vapor, enabling quantitative detection in the range of 100–8000 ppm. 相似文献
75.
This paper presents a syntactic approach based on Adjacency Grammars (AG) for sketch diagram modeling and understanding. Diagrams are a combination of graphical symbols arranged according to a set of spatial rules defined by a visual language. AG describe visual shapes by productions defined in terms of terminal and non-terminal symbols (graphical primitives and subshapes), and a set functions describing the spatial arrangements between symbols. Our approach to sketch diagram understanding provides three main contributions. First, since AG are linear grammars, there is a need to define shapes and relations inherently bidimensional using a sequential formalism. Second, our parsing approach uses an indexing structure based on a spatial tessellation. This serves to reduce the search space when finding candidates to produce a valid reduction. This allows order-free parsing of 2D visual sentences while keeping combinatorial explosion in check. Third, working with sketches requires a distortion model to cope with the natural variations of hand drawn strokes. To this end we extended the basic grammar with a distortion measure modeled on the allowable variation on spatial constraints associated with grammar productions. Finally, the paper reports on an experimental framework an interactive system for sketch analysis. User tests performed on two real scenarios show that our approach is usable in interactive settings. 相似文献
76.
Mark Anderson Rajiv D. Banker Nirup M. Menon Jorge A. Romero 《Information Technology and Management》2011,12(3):197-212
This paper examines the impact of the duration of ERP implementation on firm performance both during and after implementation.
Organizations choose either an accelerated implementation approach or a traditional (longer) implementation approach. The
former approach gives the organization the advantage of speed, but the disadvantage of fitting its processes to that of a
packaged (thus, undifferentiated from competitors) ERP. The latter approach allows the organization to redesign strategy and
processes, and thus, search for ways to be unique from its competition. The study uses a regression model to capture the changes
in various performance measures during and after implementation between firms that implemented the ERP, using the performance
measure of a matched group of firms that did not implement an ERP as a benchmark/control sample, on the basis of the duration
of the implementation. Financial data from Compustat, and data on start date and end date of ERP implementation between 1990
and 2005 for firms in the Oil and Gas industry was collected from an ERP vendor. Results show that measures such as return
on sales improved after implementation. However, measures such as inventory turnover, which reflect operational benefits,
improve during implementation. We find that accelerated implementation confers both operational and strategic benefits. This
study highlights the strategic consequences of the different choices of implementation. 相似文献
77.
This paper proposes a new approach for the segmentation of both near-end and far-end intima-media regions of the common carotid artery in ultrasound images. The method requires minimal user interaction and is able to segment the near-end wall in arteries with large, hypoechogenic and irregular plaques, issues usually not considered previously due to the increased segmentation difficulty. 相似文献
78.
Jorge E. Mendoza Bruno Castanier Christelle Guéret Andrés L. Medaglia Nubia Velasco 《Computers & Operations Research》2010,37(11):1886-1898
The multi-compartment vehicle routing problem (MC-VRP) consists of designing transportation routes to satisfy the demands of a set of customers for several products that, because of incompatibility constraints, must be loaded in independent vehicle compartments. Despite its wide practical applicability the MC-VRP has not received much attention in the literature, and the few existing methods assume perfect knowledge of the customer demands, regardless of their stochastic nature. This paper extends the MC-VRP by introducing uncertainty on what it is known as the MC-VRP with stochastic demands (MC-VRPSD). The MC-VRPSD is modeled as a stochastic program with recourse and solved by means of a memetic algorithm. The proposed memetic algorithm couples genetic operators and local search procedures proven to be effective on deterministic routing problems with a novel individual evaluation and reparation strategy that accounts for the stochastic nature of the problem. The algorithm was tested on instances of up to 484 customers, and its results were compared to those obtained by a savings-based heuristic and a memetic algorithm (MA/SCS) for the MC-VRP that uses a spare capacity strategy to handle demand fluctuations. In addition to effectively solve the MC-VRPSD, the proposed MA/SCS also improved 14 best known solutions in a 40-problem testbed for the MC-VRP. 相似文献
79.
Inés González-Rodríguez Camino R. Vela Jorge Puente 《Journal of Intelligent Manufacturing》2010,21(1):65-73
In this work we consider a multiobjective job shop problem with uncertain durations and crisp due dates. Ill-known durations
are modelled as fuzzy numbers. We take a fuzzy goal programming approach to propose a generic multiobjective model based on
lexicographical minimisation of expected values. To solve the resulting problem, we propose a genetic algorithm searching
in the space of possibly active schedules. Experimental results are presented for several problem instances, solved by the
GA according to the proposed model, considering three objectives: makespan, tardiness and idleness. The results illustrate
the potential of the proposed multiobjective model and genetic algorithm. 相似文献
80.
Iván García-Magariño Rubén Fuentes-Fernández Jorge J. Gómez-Sanz 《Information and Software Technology》2010,52(4):422-435
Computer-Aided Software Engineering (CASE) tools support modeling-related activities in development projects. Given the variety of tools and functionalities, it is quite common to work with several tools in the same project. However, data cannot usually be exchanged between these tools without loss of information. Recent approaches address this model interchange problem using metamodels to characterize the involved information and transformations to export/import it. Nevertheless, most of these solutions focus on the abstract syntax of models. They fail to consider aspects such as the presentation of models or tool-specific information, which are either disregarded or represented in ad-hoc ways that make difficult their processing. In order to overcome these limitations, this paper introduces a framework to define metamodels of CASE tools and a process to carry out the model interchange using them. The proposed metamodels have a modular organization with several internal metamodels. Each of them is aimed at describing some specific information about content, structure and presentation for both models and tools. The paper illustrates this approach with a case study used for comparison with existing works for this problem. 相似文献