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101.
Susana Filipe João Manuel Maia Catarina Rosa Leal Maria Teresa Cidade 《应用聚合物科学杂志》2007,105(3):1521-1532
The main aim of this work is to study the influence of the application of different processing conditions on the morphological and mechanical properties of thermoplastic/LCP blends, in which the viscosity ratios are inferior to unity and decrease with increasing temperature. The way the microstructure evolves along the extruder determines the final morphology and thus, the mechanical performance of the systems. In the present case, the mechanical properties are related with the degree of fibrillation in the final composites. The best degree of fibrillation was obtained for low screw speeds and temperatures and for intermediate outputs. The use of high screw speeds and processing temperatures results in a decrease of the viscosity ratio, in the former case via an increase in the viscous dissipation, at the regions of higher shear rates (kneading‐elements). The application of a lower processing temperature is advantageous for deformation, break‐up, and fibrillar formation because of the higher viscosity ratios and higher shear stresses involved. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
102.
This paper investigates the interaction between network coding and link-layer transmission rate diversity in multi-hop wireless networks. By appropriately mixing data packets at intermediate nodes, network coding allows a single multicast flow to achieve higher throughput to a set of receivers. Broadcast applications can also exploit link-layer rate diversity, whereby individual nodes can transmit at faster rates at the expense of corresponding smaller coverage area. We first demonstrate how combining rate-diversity with network coding can provide a larger capacity for data dissemination of a single multicast flow, and how consideration of rate diversity is critical for maximizing system throughput. Next we address the following question: given a specific topology of wireless nodes, what is the maximum rate that can be supported by the resultant network exploiting both network coding and multi-rate? We present a linear programming model to compute the maximal throughput that a multicast application can achieve with network coding in a rate-diverse wireless network. We also present analytical results where we observe noticeably better throughput than traditional routing. This suggests there is opportunity for achieving higher throughput by combining network coding and multi-rate diversity. 相似文献
103.
Jérôme MendesAuthor VitaeRui AraújoAuthor Vitae Pedro SousaAuthor Vitae Filipe ApóstoloAuthor Vitae Luís AlvesAuthor Vitae 《Computers in Industry》2011,62(3):364-373
The paper presents an architecture for adaptive fuzzy control of industrial systems. Both conventional and adaptive fuzzy control can be designed. The control methodology can integrate a priori knowledge about the control and/or about the plant, with on-line control adaptation mechanisms to cope with time-varying and/or uncertain plant parameters. The paper presents the fuzzy control software architecture that can be integrated in industrial processing and communication structures. It includes four distinct modules: a mathematical fuzzy library, a graphical user interface (GUI), fuzzy controller, and industrial communication. Three types of adaptive fuzzy control methods have been studied, and compared: (1) direct adaptive, (2) indirect adaptive, and (3) combined direct/indirect adaptive. An experimental benchmark composed of two mechanically coupled electrical DC motors has been employed to study the performance of the presented control architectures. The first motor acts as an actuator, while the second motor is used to generate nonlinearities and/or time-varying load. Results indicate that all tested controllers have good performance in overcoming changes of DC motor load. 相似文献
104.
Jerusa Simone Garcia Gustavo Braga SanvidoSérgio Adriano Saraiva Jorge Jardim ZaccaRicardo Guanaes Cosso Marcos Nogueira Eberlin 《Food chemistry》2012,131(2):722-726
Matrix-assisted laser desorption/ionisation-quadrupole time of flight mass spectrometry (MALDI-QTOF MS) allowed detection of bovine milk powder adulteration with vegetable oils or fats with high speed and reliability, requiring little sample preparation (n-hexane extraction) and no prior separation procedures. This technique was also able to identify the adulterated employed in this fraud. Hydrogenated soybean oil addition in bovine milk powder sample generate a similar TAG profile to that observed on adulterated milk samples apprehended by the Brazilian Federal Police. In this sense, a robust method for high throughput forensic screening of milk powder adulteration by exogenous oils and fats is showed. 相似文献
105.
Botega Leonardo Castro de Souza Jéssica Oliveira Jorge Fábio Rodrigues Coneglian Caio Saraiva de Campos Márcio Roberto de Almeida Neris Vânia Paula de Araújo Regina Borges 《Universal Access in the Information Society》2017,16(4):889-902
Universal Access in the Information Society - Situation Assessment (SA) approaches aim to provide powerful resources to support decision makers in enhancing their Situational Awareness (SAW). The... 相似文献
106.
Carlos Angelo Nunes Gilberto Carvalho Coelho Alfeu Saraiva Ramos 《Journal of Phase Equilibria and Diffusion》2001,22(5):556-559
The Mo-Si system presents two invariant reactions (eutectic and peritectic) in the Mo-rich region; these reactions involve
the Liquid, Moss, Mo3Si, and Mo5Si3 phases. The results presented in the literature show disagreement about the specific reactions, with two proposals being
reported: (1) L + Moss ⇔ Mo3Si and L ⇔ Mo3Si + Mo5Si3; and (2) L + Mo5Si3 ⇔ Mo3Si and L ⇔ Moss + Mo3Si. In order to contribute to this subject, we have produced several Mo-Si alloys (21 to 29 at.% Si) via arc melting and evaluated the as-cast microstructures through x-ray diffraction (XRD), scanning electron microscope/backscattered
electron image (SEM/BSEI), and energy dispersive x-ray analysis (EDS). The primary phases identified in the different samples
were Moss, Mo3Si, and Mo5Si3. The results have indicated clearly the existence of a eutectic reaction involving the phases Mo3Si and Mo5Si3, confirming the existence of the L + Moss ⇔ Mo3Si and L ⇔ Mo3Si + Mo5Si3 invariant reactions. In addition, alloys with composition 26 at.% Si and 27 at.% Si presented Mo3Si and Mo5Si3 as primary phases, respectively, indicating that the liquid eutectic composition is located between those values. 相似文献
107.
108.
Paulo Roberto Saraiva Cavalcante Maria do Socorro Rodrigues Marcel Felipe Sousa Barroso Ricardo Barbieri Carmen Lúcia Martins Serra Rosana Carla Alves Oliveira 《Lakes & Reservoirs: Research and Management》2007,12(1):35-42
The diel variation of limnological parameters, measured in Boa Esperança Reservoir, Brazil during the rainy period, exhibited small temperature gradients characterized by an increase in temperature by midday, followed by a partial homogenization of the water column in the night and the early morning. The result was an increase in the epilimnion to a depth of 17 m. The pH and dissolved oxygen concentrations showed higher values at the surface, with the occurrence of anomalies (concentrations higher than at the surface) of the latter variable in the epilimnion, probably as a result of the activity of primary producers and/or losses of oxygen to the atmosphere. The chemical forms of iron in the reservoir exhibited increasing concentrations with depth, as a result of an increase in the concentration of seston and/or accentuated reduction of the levels of oxygen in the bottom layers. The reduction of Fe3+ to Fe2+ in the bottom water layers in the reservoir, in addition to the primary production process in the epilimnion, could explain the increased phosphorus in the bottom water layer. The concentrations of nitrogen compounds did not exhibit relevant changes or a defined evolution profile, except for nitrate, which showed an outstanding increase in the bottom water layers, suggesting it could be an important nitrogen source for primary producers. Although not unequivocal, these data suggest that ecosystem instability in Boa Esperança Reservoir is the product of short diel thermal variations, and the reduced input of allochthonous materials and nutrients from local catchment. These conditions guarantee the oligotrophic status of Boa Esperança Reservoir for the present time. 相似文献
109.
The addition of a liquid crystalline polymer (LCP) to a matrix of a flexible thermoplastic (TP) has been used in the last two decades as an in situ reinforcement of the matrix. Owing to the immiscibility of the two phases and the high degree of orientation typical of LCPs, the dispersed phase is, after processing, essentially constituted by fibrillar structures, which are responsible for the reinforcement of the matrix and the decrease of viscosity with respect to the matrix. The low degree of adhesion typical of LCP/TP blends often requires the use of compatibilizers, which will act reducing the interfacial tension between the two components. In this work, we present the synthesis of three different compatibilizers, as well as the mechanical characterization of the corresponding compatibilized blends. Some scanning electron microphotographs will be also presented to better explain the mechanical results. The mechanical properties of these blends were compared with the noncompatibilized blend, as well as with the ones presented by blends obtained with two commercial compatibilizers, leading to the conclusion that, considering our compatibilizer C, the one that leads to the higher enhancement of the Young's modulus, when compared with the noncompatibilized blend, we obtain a Young's modulus 27% higher than the one presented by the noncompatibilized blend. Comparing this result with those presented by the blends compatibilized with the two commercial compatibilizers, D and E, we conclude that this enhancement is higher than those presented by those blends (increase in Young's modulus of 16% for both compatibilizers). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
110.
Nuno Costa Nuno Machado Filipe Samuel Silva 《Journal of Materials Engineering and Performance》2008,17(3):352-362
This paper is concerned with the evaluation of different fatigue strength theories to predict the fatigue life of high-strength
nodular cast iron. There have been some studies on the effects of the shape and size of graphite nodules, and of microstructure,
on the fatigue strength of nodular cast iron. However, there is not a consensus on how to correlate the fatigue limit with
material intrinsic properties or with external features such as considering graphite nodules as defects. Some researchers
found good correlations between fatigue strength, σw0, and the geometrical aspects of the graphite nodules, considering it as internal material defects. It will be shown in this
study that geometrical features such as shape, size, and relative position seem to be adequate to be included in those predictions.
In this article, a high-strength cast iron, with rupture strength of about 1300 MPa and Young’s modulus of about 160 GPa,
has been used. Correlations both with intrinsic properties as well as with other geometrical effects have been made. A comparison
of different theories has also been carried out.
This article was presented at Materials Science & Technology 2007, Automotive and Ground Vehicles symposium held September
16–20, 2007, in Detroit, MI. 相似文献