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排序方式: 共有350条查询结果,搜索用时 15 毫秒
31.
Nikola Vitković Miloš Stojković Vidosav Majstorović Miroslav Trajanović Jelena Milovanović 《CIRP Annals》2018,67(1):177-180
Bone scaffolds provide a structural support for tissue development. Existing bone scaffolds are mainly characterized by complex porous designs whose shortcomings are a low level of permeability for growing tissue, and a difficult design customization. Scaffolds with nucleuses (rods or lattices) as basic elements should improve bone regeneration and enable higher design flexibility. In this paper, we present two new methods for building 3D geometrical models of personalized scaffolds, which are based on method of anatomical features. Methods are demonstrated in the case of scaffold for the mandible bone. This approach greatly reduces the designer effort and time, while enabling easy personalization of scaffolds’ shape and geometry. 相似文献
32.
Nikola Milašinović Nedeljko Milosavljević Jovanka Filipović Zorica Knežević-Jugović Melina Kalagasidis Krušić 《Reactive and Functional Polymers》2010,70(10):807-814
Temperature- and pH-sensitive hydrogels based on N-isopropylacrylamide (NiPAAm) and itaconic acid (IA) were applied for immobilization of lipase from Candida rugosa (CRL). The hydrogels were synthesized by free radical crosslinking copolymerization in the presence of lipase. Characterization of samples by swelling studies, at pH 2.20 and 6.80 at a temperature of 37 °C, scanning electron microscopy (SEM) and Fourier transform infrared analysis (FT-IR) confirmed that the degree of crosslinking, the non-ionic/ionic (NiPAAm/IA) ratio and the enzyme content had impacts on the hydrogel structure, mechanical properties, morphology and swelling kinetics. All hydrogels demonstrated protein loading efficiencies as high as 95 wt.%. A specific activity of the immobilized lipase of around 38 IU/g was attained for an enzyme loading of 20.0 wt.%. As a result, improved pH and temperature optima values were obtained for the immobilized systems in relation to those for the free lipase. 相似文献
33.
Nikola R. Slavkovic Dragan S. Milutinovic Milos M. Glavonjic 《The International Journal of Advanced Manufacturing Technology》2014,70(9-12):2083-2096
Industrial robots are promising cost-effective and flexible alternatives for multi-axis milling applications in machining of complex parts of light materials with lower tolerances, having freeform surfaces. As it is well-known, the poor accuracy, stiffness, and the complexity of programming are the most important limiting factors for wider adoption of robotic machining in machine shops. The paper presents the developed method for off-line compensation of machining robot tool tip static displacements as a dominant part of cutting force-induced errors. The developed method is based on modification of programmed trajectory in G-code. Off-line modification of programmed trajectory is performed according to the predicted static tool tip displacements calculated based on developed robot compliance model and cutting forces predicted by mechanistic model. The obtained experimental results show the relevance of developed method since the machining errors could be significantly reduced. This allows the desired accuracy of robot machining to converge towards nominal specifications. 相似文献
34.
Sandra Kurko Igor MilanovićJasmina Grbović Novaković Nenad IvanovićNikola Novaković 《International Journal of Hydrogen Energy》2014
Desorption of hydrogen atoms from the (110) surface of rutile magnesium hydride (MgH2) was investigated using density functional theory (DFT) and pseudopotential method. System was represented by (110) (2×2) slab MgH2 supercell with 12 atomic layers along the z-axis. The H-desorption was modeled by the successive release of the four two-fold bonded H atoms from the (110) surface of MgH2. Dependence of the H-desorption energy on number and configuration of remaining surface hydrogen atoms has been determined. The features of the H atoms diffusion from the bulk towards the surface have been investigated, too. The results suggest that decrease in number of surface H atoms generally lowers the H-desorption energy in each desorption step and that both the H–H and the Mg–H interatomic interactions strongly influence the H-desorption process. The hydrogen vacancy formation energy in the first three sub-surface layers also exhibits a pronounced dependence on concentration. These findings lead to the conclusion that tendency of the MgH2 (110) surface to preserve a maximum possible surface H concentration in its most stable configuration is the limiting factor for the H-desorption kinetics. In principle, the obtained results allow us to determine preferred paths of surface and sub-surface H-diffusion for a wide range of H concentrations and the principle features of the MgH2 dehydrogenation process, at least for the H-rich region. Being rather comprehensive, the approach is applicable for other metal hydrides, as well. 相似文献
35.
Antoine Doucet Gabriella Kazai Bodin Dresevic Aleksandar Uzelac Bogdan Radakovic Nikola Todic 《International Journal on Document Analysis and Recognition》2011,14(1):45-52
This paper describes the setup of the Book Structure Extraction competition run at ICDAR 2009. The goal of the competition
was to evaluate and compare automatic techniques for deriving structure information from digitized books, which could then
be used to aid navigation inside the books. More specifically, the task that participants faced was to construct hyperlinked
tables of contents for a collection of 1,000 digitized books. This paper describes the setup of the competition and its challenges.
It introduces and discusses the book collection used in the task, the collaborative construction of the ground truth, the
evaluation measures, and the evaluation results. The paper also introduces a data set to be used freely for research evaluation
purposes. 相似文献
36.
Nikola Vukašinović Drago Bračun Janez Možina Jože Duhovnik 《The International Journal of Advanced Manufacturing Technology》2010,50(1-4):265-274
This article examines the influence of incident angle, object colour and measurement distance on the computer numerically controlled laser scanning process. To determine the physical background of these influences, the operation of the triangulation sensor, the surface reflection and the colour properties of the measured object were analysed. The various influences and their physical background are explained by using a test-measurement setup, which makes it possible to investigate a specific influencing factor. The article concludes with several guidelines that should be followed in order to obtain better measurement results. 相似文献
37.
38.
Computer tomography has been used frequently for the 3‐D visualization of plant anatomical traits but sample preparation has been widely neglected. Without any preparation smaller (i.e., up to 1 × 1 cm2) turgescent or semi‐dry plant samples (especially leaf samples) diminish the image quality of a scan due to gradual water loss and therefore constant movement. A suitable preparation for scans of turgescent and semi‐dry plant samples with a high resolution μCT (<1–5 μm) has to be very thin, heat‐resistant (up to 35°C), have a low attenuation coefficient, and should not alter the water content and structure of the sample. Several agents have been tested, but only a coating with vaseline conserved the water content of a plant sample efficiently. However, water molecules and vaseline both attenuate the X‐ray beam, which decreases the image quality of scans of turgescent or semi‐dry plant samples. Therefore, trade‐offs between the spatial resolution, sample water content, sample size, and image quality have to be considered: larger samples have to be placed further away from the X‐ray tube, which leads to a lower spatial resolution; water and preparation agents attenuate the X‐ray beam, causing low‐quality images which may be accompanied by motion artifacts compared to a scan of a dry sample, where no preparation is necessary. Microsc. Res. Tech., 2011. © 2010 Wiley‐Liss, Inc. 相似文献
39.
Prtljaga N D'Amato E Pitanti A Guider R Froner E Larcheri S Scarpa M Pavesi L 《Nanotechnology》2011,22(21):215704
Stable aqueous solutions of undecylenic-acid-grafted silicon nanocrystals (Si-nc) were prepared. The time evolution of the photoluminescence properties of these hydrophilic silicon nanocrystals has been followed on different timescales (hours and days). On a short timescale (hours), Si-nc tend to agglomerate while the PL lineshape and intensity are stable. Agglomeration can be reduced by using suitable surfactants. On a long timescale (days), oxidation of Si-nc occurs even in the presence of surfactants. These two observations render Si-nc very useful as a labeling agent for biosensing. 相似文献
40.
Vesna Janicki Jordi Sancho-ParramonHrvoje Zorc Krešimir SalamonMaja Buljan Nikola Radi?Uroš Desnica 《Thin solid films》2011,519(16):5419-5423
Mixture layers of Ge:SiO2 of 40:60 mol% respectively, have been prepared by co-sputtering. The thermally induced change of optical properties of the layers was studied by variable angle spectroscopic ellipsometry. The mixture was modelled as an unknown material with optical constants described by multiple oscillators. The optical parameters determined from ellipsometric measurements can be well correlated with structural changes in the mixture. The results indicate that Ge in the mixture deposited or annealed up to 600 °C is in an amorphous state and it redistributes with increase of temperature, changing refractive index through the layer. The crystallization starts between 600 and 650 °C, at first next to the substrate. Crystallites size grows with temperature. Results were compared with findings of grazing incidence wide angle X-ray scattering measurements and a good agreement was found. Ellipsometry has been shown to be an appropriate non-invasive technique for characterization of this kind of layers. 相似文献