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排序方式: 共有296条查询结果,搜索用时 15 毫秒
1.
Marek Markowski Ireneusz Bialobrzewski Janusz Bowszys Stanislaw Suchecki 《Drying Technology》2007,25(9):1527-1536
A neural-deterministic simulation model applied for calculating distributions of temperatures and moisture content in a bed of wheat stored in a steel silo without aeration is presented in the article. The model consists of differential equations of heat and moisture transfer, initial and boundary conditions, and three artificial neural networks used during simulated ambient air conditions. Experiments and computer simulations were carried out in order to determine temperature fields in wheat grain stored in a steel silo for two months. The computer simulations were carried using MATLAB and FEMLAB software. The difference between measured and simulated temperature in grain near the silo wall at a height of 2.5 m from the bottom was less than 3.0°C. On the basis of the analysis performed it was concluded that the temperature distributions obtained with the model were consistent with the measured results obtained for grain stored in a steel silo without aeration. 相似文献
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Hydrogen transport through amorphous Pd82−yNiySi18 alloys (y=0-32) was investigated in 0.1 M NaOH solution by analysis of the anodic current transient. It was found that the anodic current transient shows the non-Cottrell behaviour, but its shape and value remain nearly constant regardless of the hydrogen discharging potential. From the coincidence of the anodic current transient theoretically calculated with that experimentally measured, it is suggested that the change in surface concentration of hydrogen with time is uniquely given by the rate of hydrogen transfer from absorbed state at the electrode sub-surface to adsorbed state on the electrode surface. This means that neither the ‘constraint of constant concentration’ nor the ‘constraint by Butler-Volmer behaviour’ is effective at the electrode surface during hydrogen extraction. On the basis of the theoretical current-time relation under the ‘constraint by hydrogen transfer of absorbed state to adsorbed state’, the hydrogen diffusivity was determined to have an almost constant value of (1.3±0.4)×10−8 cm2 s−1, irrespective of the Ni content and in the absence of Ni. On the other hand, it is inferred that the rate constant of hydrogen transfer decreases markedly with increasing Ni content due to the Ni(OH)2 layer formed on the electrode surface. 相似文献
4.
Following our previous papers on mechanism of cyclic esters' polymerization coinitiated by tin(II) octoate [tin(II) bis-(2-ethylhexanoate), (Sn(Oct)2)] in the presence of either the low molar mass coinitiator (an alcohol, hydroxy acid, or H2O) or a macromolecule fitted with a hydroxy end group (ROH), the present work deals with ?-caprolactone (CL) and l,l-lactide (LA) polymerizations coinitiated with zinc octoate (Zn(Oct)2) or aluminum acetylacetonate (Al(Acac)3). A series of kinetic measurements revealed that similarly as in the Sn(Oct)2 coinitiated process, these polymerizations proceed by simple monomer insertion into the …Mt-OR bond, reversibly formed in the reaction -Mt-L + ROH ? …-Mt-OR + LH (where Mt = Sn, Zn or Al; L = Oct or Acac), taking place throughout the whole polymerization process. MtLn itself does not play an active role in the polymerization. Applicability of the commercially available Zn(Oct)2 or Al(Acac)3 for the aliphatic polyester (103 ≤ Mn ≤ 4 × 105) synthesis is also discussed. 相似文献
5.
Slawomir Koziel Stanislaw Szczepanski Rolf Schaumann 《International Journal of Circuit Theory and Applications》2004,32(6):565-589
Starting from a set of matrices describing a general Gm‐C filter topology, a procedure is developed for generating structures of lowpass filters. As the matrices and the filter topologies have a one‐to‐one correspondence, an algebraic method is used to identify filter topologies with desired properties, here, transfer functions with finite jω‐axis transmission zeros, specifically elliptic filters. Sensitivity expressions for these structures are derived and a performance comparison based on a set of chosen criteria is made. For a specified elliptic transfer function, filters with only grounded capacitors and those containing also floating capacitors emerge as alternative realizations, as are filters with a single input and those with distributed inputs. For third‐order functions, a detailed comparison is performed of leapfrog (LF) and inverse follow‐the‐leader‐feedback (IFLF), the most popular special cases, and of topologies that have also floating capacitors (LFf, IFLFf), as well as of a novel configuration that uses also distributed inputs (DIf) and leads to a reduced element count. Design guidelines and restrictions are given, which follow from the derived results with focus on the circuits' sensitivity performance and other properties important for IC implementation. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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Multi‐objective design optimization of antennas for reflection,size, and gain variability using kriging surrogates and generalized domain segmentation 下载免费PDF全文
Cost‐efficient multi‐objective design optimization of antennas is presented. The framework exploits auxiliary data‐driven surrogates, a multi‐objective evolutionary algorithm for initial Pareto front identification, response correction techniques for design refinement, as well as generalized domain segmentation. The purpose of this last mechanism is to reduce the volume of the design space region that needs to be sampled in order to construct the surrogate model, and, consequently, limit the number of training data points required. The recently introduced segmentation concept is generalized here to allow for handling an arbitrary number of design objectives. Its operation is illustrated using an ultra‐wideband monopole optimized for best in‐band reflection, minimum gain variability, and minimum size. When compared with conventional surrogate‐based approach, segmentation leads to reduction of the initial Pareto identification cost by over 20%. Numerical results are supported by experimental validation of the selected Pareto‐optimal antenna designs. 相似文献
8.
Masakazu Anpo Shinya Higashimoto Masaya Matsuoka Nurbosyn Zhanpeisov Yasushi Shioya Stanislaw Dzwigaj Michel Che 《Catalysis Today》2003,78(1-4):211-217
V-silicalite catalysts (VS-1 and VS-2) prepared by hydrothermal synthesis have been studied by ESR, XAFS (XANES and EXAFS) and photoluminescence spectroscopy. The in situ characterization of these V-silicalites shows that vanadium is present within the zeolitic framework as a highly dispersed tetrahedrally coordinated V-oxides, VO4 unit, having a short V=O bond length. Photoluminescence spectroscopy in static and dynamic mode, as well as XAFS studies allow to detect in the V-silicalites different V species than that present in V-HMS or V/SiO2, in terms of V=O bond length, vibrational energy,
bond angle and lifetime of the excited triplet state. It is suggested that the combined contribution of the neighboring Si---OH group attached to the VO4 unit and the zeolitic rigid framework structure of V-silicalites cause a more significant and pronounced effect on the chemical properties of the VO4 unit than the flexible structure of V-HMS or V/SiO2. Moreover, the dynamic quenching of the phosphorescence by the addition of reactant molecules such as NO or propane indicates that the V species in the excited triplet state can be expected to be the active sites for the photocatalytic reactions. 相似文献
9.
On Defined Polyethylene Oxide Adducts. V. Nitrogen Containing Polyethylene Oxide Adducts The authors report on the synthesis and properties of longchain α-hydro-ω-N-alkylamino-polyoxyethylenes, there methylethers, and of α-hydro-ω-N-dodecylacetamidopolyoxyethylenes. Special surface properties as solubility, surface activity and micel formation are discussed. 相似文献
10.
Maciej Gubernat Aneta Fraczek- Szczypta Janusz Tomala Stanislaw Blazewicz 《Ceramics International》2018,44(3):3085-3091
A simple and effective way to manufacture graphene from a coal tar pitch (CTP) is demonstrated. Silica (SiO2) nanoparticles were used to modify the CTP as carbon precursor. A silica nanofiller introduced into the CTP matrix underwent carboreduction during heat treatment to 2000 °C, resulting in the formation of silicon carbide. Surfaces of SiC grains were sites for graphene formation. The influence of SiO2 on the structure and microstructure of CTP- based carbon matrix, after annealing up to 2800 °C, was studied. Carbon samples were analyzed using X- ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Raman Spectroscopy. Crystallite sizes (La, Lc) and interplanar distance (d002) were determined. The presence of SiO2 in CTP carbon precursor favored the crystallites’ growth in the ‘a′ crystallographic graphite direction, and inhibited their growth on the ‘c′ axis. The crystallites composing of graphene layers, were characterized by an elongated dimension in the ‘a′ axis direction. Above 2000 °C silicon carbide decomposed, followed by the sublimation of silicon from the carbon matrix. 相似文献