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11.
We present a modular technique for analyzing probe-fed, multilayered microstrip phased-array antennas. Each patch layer is assumed to be infinite in extent and represented by its generalized scattering matrix (GSM) with respect to a finite number of Floquet modes. For multilayer patch analysis, the individual GSMs are combined appropriately to yield the overall GSM of the structure. The individual GSM are obtained using the Galerkin method. The probe layer is represented by its generalized impedance matrix (GIM) which is deduced using Floquet modal analysis and the variational method. The GSMs and GIM are combined appropriately to yield the input impedance seen by the probe. Numerical results computed with this technique are shown to agree favorably with available data. Results for two-layered patch arrays and capacitively coupled patches are also presented 相似文献
12.
The 1,3-specific lipase-catalyzed interesterified fats were distinguished from chemically catalyzed products by the fatty
acids in the 2-position. The fatty acid contents in the 2-position of the 1,3-lipase-catalyzed and the original triglycerides
were similar but different from that of chemically interesterified fat. Also, the saturated-to-unsaturated fatty acid ratio
in the 2-monoglycerides was lower for the 1,3-specific lipase-catalyzed interesterified fats than for the corresponding chemical
products. 相似文献
13.
D. K. Bhattacharyya M. M. Chakrabarty K. Kar 《European Journal of Lipid Science and Technology》1985,87(7):278-282
Acidolysis reaction of sal fat (Shorea robusta) with palmitic acid has been studied in relation to the operating variables like catalyst system and concentration, reaction temperature and time and molar ratios of reactants with the object of introducing more palmitic acid which is low in sal fat. The results demonstrate that as low as 2.5% and as high as 39% palmitic acid can be introduced in sal fat at the expense of other acids under the influence of various operating conditions. The products obtained differ from original sal fat in respect of chemical composition and slip point. The importance of such study is that there are possibilities of getting plastic fats of diverse properties for edible and industrial uses. 相似文献
14.
R. Maji S. Bhattacharyya S. Dasgupta S. Bandyopadhyay R. Mukhopadhyay A. S. Deuri 《应用聚合物科学杂志》2007,104(4):2735-2742
The basic objective of this article is to improve the polymer blend properties by changing mixing sequence. Blending of two elastomers does not lead to a molecularly homogeneous blend (true solution), but to a heterogeneous system in which both polymer phases are present. In this article, the detailed study of heterogeneous distribution of carbon black as well as blend inhomogenity and the physicomechanical including dynamic mechanical properties of the blend has been carried out. The choice of the blend was natural rubber/polybutadiene rubber as 85:15. Heterogeneous carbon black distribution study was also performed in differential scanning calorimeter. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2735–2742, 2007 相似文献
15.
Anindita Bhattacharyya 《Chemical engineering science》2004,59(21):4481-4492
An arbitrary flow of a viscous, incompressible fluid past a porous sphere of radius `a' with an impermeable core of radius `b', using Brinkman's equation in the porous region is discussed. At the interface of the clear fluid and porous region, stress jump boundary condition for the tangential stresses along with the continuity of normal stresses and the velocity components are used. On the surface of the impermeable core no slip condition is used. The corresponding Faxen's laws are derived to compute the drag and torque acting on the surface r=a. It is found that the drag and torque not only change with the change of the permeability, but also a significant effect of the stress jump co-efficient is observed. The variation of drag and torque with permeability for different thickness (a-b) of the porous region as well as for different values of stress jump coefficient is discussed when the basic flow is due to uniform flow, two dimensional irrotational flow, doublet in a uniform flow, stokeslet, rotlet. In case of uniform flow the flow field has been plotted. In all the cases, a significant effect of the stress jump coefficient has been realized. 相似文献
16.
Poly(o‐toluidine) (POT) is an electroactive polymer with poor mechanical and thermal characteristics. We examined the scope for improving such properties by making blends of POT with ethylene–propylene–diene rubber (EPDM). We prepared POT–EPDM blends containing different weight fractions of POT by intimately mixing known volumes of separate solutions of the two polymers (POT in THF and EPDM in toluene). Films of EPDM and POT–EPDM blends in solution were obtained by spreading, solvent evaporation, and film casting techniques. POT, EPDM, and their blends were characterized in solution by ultraviolet‐visible spectroscopy, and the respective dried samples were analyzed by Fourier transform infrared spectroscopy and thermogravimetry. The polymer samples were further analyzed morphologically by scanning electron microscopy, and their tensile strengths were also evaluated. Spectroscopic and thermal studies of the blends indicated some sort of interaction between the two constituent polymers. The direct current electrical conductivity of the blends in increasing order of POT loading (12.5–100%) was in the range 9.9 × 10?5 to 11.6 × 10?2 S cm?1. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2550–2555, 2003 相似文献
17.
Radiation-initiated copolymerization of solid trioxane (TOX) with tetrahydrofuran (THF) was investigated. The effects of radiation dose, THF concentration, and post-polymerization temperature and duration on copolymer yield and THF incorporation were studied. These results are compared with the results of TOX homopolymerization under identical conditions. Copolymer yield was lower than that of homopolymer. Only a fraction of charged THF entered into the polymer chain. THF content and radiation dose also altered the MW of the copolymer but it showed better thermal stability. The initial reaction rates of the copolymerization were determined and from these the activation energy was found to be 36.2 kcal mol?1. 相似文献
18.
The preparation of dibasic acid-containing soy phospholipid was made by transesterification reaction with alkyl ester of diabasic acid with both lipase and alkoxide as a catalyst. The extent of incorporation of a dibasic acid varied with the molecular size of the dibasic acid. The extent of incorporation in soy phospholipids was 4–13% in the case of adipic acid and 9–20% in the case of sebacic acid. The surface-active properties of these modified soy phospholipids were examined and were found to be different from those of the original (unmodified) soy phospholipid. The interfacial properties such as critical micelle concentration (CMC), γCMC, surface excess concentration Γmax, and minimum area per molecule (Å), and thermodynamic parameters such as standard free energy of micellization, were found to depend on the hydrophobic part of the dibasic acids. 相似文献
19.
Mechanical properties and morphological studies of compatibilised blends of PA6/EVA-g-MA and PA6/EVA/EVA-g-MA were studied as functions of maleic anhydride content (MA) and dispersed phase (EVA-g-MA) concentrations, respectively at blending composition of 20 wt% dispersed phase (EVA-g-MA or combination of EVA and EVA-g-MA). The maleic anhydride (MA) was varied from 1 to 6 wt% in the PA6/EVA-g-MA blend, whereas MA concentration was fixed at 2 wt% in the ternary compositions with varying level of EVA-g-MA. ATR-IR spectroscopy revealed the formation of in situ copolymer during reactive compatibilisation of PA6 and EVA-g-MA. It was found that notched Izod impact strength of PA6/EVA-g-MA blends increased significantly with MA content in EVA-g-MA. The brittle to tough transition temperature of reactively compatibilised blends was found to be at 23 °C. The impact fractured surface topology reveals extensive deformation in presence of EVA-g-MA whereas; uncompatibilised PA6/EVA blend shows dislodging of EVA domains from the matrix. Tensile strength of the PA6/EVA-g-MA blends increased significantly as compared to PA6/EVA blends. Analysis of the tensile data using predictive theories showed an enhanced interaction of the dispersed phase and the matrix. It is observed from the phase morphological analysis that the average domain size of the PA6/EVA-g-MA blends is found to decrease gradually with increase in MA content of EVA-g-MA. A similar decrease is also found to observe in PA6/EVA/EVA-g-MA blends with increase in EVA-g-MA content, which suggest the coalescence process is slower in presence of EVA-g-MA. An attempt has been made to correlate between impact strength and morphological parameters with regard to the compatibilised system over the uncompatibilised system. 相似文献
20.
Styrene portion of the radiation-induced graft copolymer comprising styrene and acrylamide was separated by acid hydrolysis and the effects of various grafting parameters (e.g., reaction time, reaction temperature, solvents, monomer composition, etc.) on molecular weight distribution were evaluated by means of gel permeation chromatography. When a single monomer or mixture of two monomers are grafted, the molecular weights is found to increase, but polymer dispersity decreases with the increase of reaction time or reaction temperature except at a higher reaction time due to the continuous enlargment of the growing chain through increased swelling and molecular motion of the trapped radicals. At higher reaction time the degradation of the graft chains lead to lower molecular weight and higher polymer dispersity. Effects of solvents (e.g., methanol, ethanol, and t-butanol) on the molecular weight and molecular weight distribution were discussed on the basis of swelling property and chain transfer constants of the solvents. Styrene-type graft radical being long lived compared to acrylamide type, gave long-chain styrene graft with the increase of styrene content in the reaction mixture. A comparison of the effect of one-and two-component systems on a molecular weight distribution is also discussed. 相似文献