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991.
Hugo Martínez‐Gutiérrez Víctor M. Ovando‐Medina René D. Peralta Eduardo Mendizábal Jorge E. Puig 《Polymer Engineering and Science》2013,53(9):1990-1995
Vinyl acetate (VAc) was polymerized by a seeded semicontinuous heterogeneous process. Stable latexes with a polymer/surfactant weight ratio of 65 were obtained, which is comparable with the highest value reported in the literature for emulsion polymerization but with the advantage of obtaining smaller particles (average diameter, Dp = 53 nm) which are similar to those obtained by microemulsion polymerization. The surfactant (sodium dodecylsulfate, SDS) concentration used in the recipe (0.32 wt%) is much lower than those typically used in microemulsion polymerization. Although molar masses increased during the continuous monomer addition period, they were small at the end of the reaction (Mn = 69 × 103 g·mol–1) and this was attributed to bimolecular termination inside the particles. The values of polymerization rate (Rp) and monomer addition rate (Fm) were nearly the same, indicating that polymerization was performed under monomer starved conditions. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers 相似文献
992.
María S. Sánchez-Adsuar M. Mercedes Pastor-Blas José Miguel Martín-Martínez 《The Journal of Adhesion》2013,89(1-4):327-345
Three polyurethane elastomers (PU) containing different hard/soft (h/s) segment ratios were prepared. The PUs were characterized using Gel Permeation Chromatography (GPC), DSC, Wide Angle X-ray Diffraction (WAXD). Dynamic Mechanical Thermal Analysis (DMTA), and Stress-controlled rheometry. The surface properties were evaluated from contact angle measurements. The PUs were used as raw materials for solvent-based adhesives, whose adhesion properties were measured from T-peel tests of solvent-wiped polyvinyl chloride (PVC)/polyurethane adhesive joints. The increase in the amount of h/s segment ratio affected the structure and morphology of the PUs, reducing the degree of phase separation and the extent of the secondary interactions between polymer chains. The h/s segment ratio determined the thermal, mechanical, rheological and adhesion properties of the PUs. 相似文献
993.
Yanina Luciani Dosinda González-Mendizabal Filippo Pironti 《Chemical Engineering Communications》2013,200(12):1653-1670
In this work, solid-liquid wetting factors were determined from liquid holdup and pressure drop measurements according to the model proposed by Pironti et al. for different air-liquid systems: distilled water and CMC solutions at viscosity values of 3, 6, 9, and 12 mPa.s. The experiments were carried out at atmospheric conditions in a column of 10.2 cm internal diameter and 2 m high, packed with a cylindrical material. The superficial mass velocities varied from 0.67 to 18.6 kg/m 2 s for liquid flow and from 0.024 to 0.31 kg/m 2 s for gas flow. Under these operating conditions, regime of continuous gas flow was observed. The wetting factors obtained were in agreement with those reported by other methods, which allow us to confirm that the model used in this work is applicable to fluids of different properties at low gas velocities. 相似文献
994.
995.
Isabel Martínez Ramon Murillo Gemma Grasa Jose R. Fernández Juan Carlos Abanades 《American Institute of Chemical Engineers》2013,59(8):2780-2794
The integration in a natural gas combined cycle (NGCC) of a novel process for H2 production using a chemical Ca–Cu loop was proposed. This process is based on the sorption‐enhanced reforming process for H2 production from natural gas with a CaO/CaCO3 chemical loop, but including a second Cu/CuO loop to regenerate the Ca‐sorbent. An integration of this system into a NGCC was proposed and a full process simulation exercise of different cases was carried out. Optimizing the operating conditions in the Ca–Cu looping process, 8.1% points of efficiency penalty with respect to a state‐of‐the‐art NGCC are obtained with a CO2 capture efficiency of 90%. It was demonstrated that the new process can yield power generation efficiencies as high as any other emerging and commercial concepts for power generation from NGCC with CO2 capture, but maintaining competing advantages of process simplification and compact pressurized reactor design inherent to the Ca–Cu looping system. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2780–2794, 2013 相似文献
996.
Dajun Yue Gonzalo Guillén‐Gosálbez Fengqi You 《American Institute of Chemical Engineers》2013,59(11):4255-4272
Mixed‐integer linear fractional program (MILFP) is a class of mixed‐integer nonlinear programs (MINLP) where the objective function is the ratio of two linear functions and all constraints are linear. Global optimization of large‐scale MILFPs can be computationally intractable due to the presence of discrete variables and the pseudoconvex/pseudoconcave objective function. We propose a novel and efficient reformulation–linearization method, which integrates Charnes–Cooper transformation and Glover's linearization scheme, to transform general MILFPs into their equivalent mixed‐integer linear programs (MILP), allowing MILFPs to be globally optimized effectively with MILP methods. Extensive computational studies are performed to demonstrate the efficiency of this method. To illustrate its applications, we consider two batch scheduling problems, which are modeled as MILFPs based on the continuous‐time formulations. Computational results show that the proposed approach requires significantly shorter CPU times than various general‐purpose MINLP methods and shows similar performance than the tailored parametric algorithm for solving large‐scale MILFP problems. Specifically, it performs with respect to the CPU time roughly a half of the parametric algorithm for the scheduling applications. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4255–4272, 2013 相似文献
997.
Inverse gas chromatography was used to estimate surface activity expressed by the dispersive component of the surface free energy, γ, as well as parameters KA and KD describing surface ability to act as electron acceptor and donor, respectively. These parameters characterize the ability of the surface to specific interactions. The method was also applied to describe the magnitude of filler‐phenolic resin interaction by Flory‐Huggins parameter, χ′23. Granulation, surface area and porosity were also determined. The minimum number of parameters required to complete characterization of filler properties has been selected by principal component analysis. The usefulness of the selection for the abrasive industry has been proven. Moreover, the similarities and deviations from “an average” filler was determined by chemometric methods. Principal component analysis (PCA) and a novel procedure based on sum of ranking differences (SRD) were successfully applied for selection of the best fillers, and of advantageous parameters for characterization of the fillers. Similar and diverse fillers have been chosen based on clustering pattern by PCA and SRD. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
998.
Víctor M. Ovando‐Medina Paola E. Díaz‐Flores René D. Peralta Eduardo Mendizábal Gladis Y. Cortez‐Mazatan 《应用聚合物科学杂志》2013,127(4):2458-2464
Vinyl acetate (VAc) and butyl acrylate (BuA) were copolymerized in heterophase by a semicontinuous process (unseeded) and compared with the seeded semicontinuous microemulsion polymerization of the same monomers. A mixture of sodium dodecyl sulfate (SDS) and poly(ethylene oxide) dodecyl ether (Brij‐35®) were used as surfactants. The effects of monomer addition rate (Ra) and surfactants concentrations (4 or 1 wt % with respect to the initial mixture of reaction) on polymer and latex properties were studied. High copolymer content latexes (24–36 wt %) with average particle diameters (Dp) from 38 to 55 nm and relatively narrow particle size distributions, high polymerization rates, weight ratios of polymer to surfactant (P/S) from 13.3 to 32.8 were obtained. The number‐average molecular weights (Mn) were between 96,000 and 188,000 g/mol. Homogeneous copolymer compositions were obtained throughout the reaction for both, seeded and unseeded processes, which is not possible by the usual batch microemulsion process. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
999.
F. J. Sánchez-Velasco C. López Del Prá Luis E. Herranz 《Aerosol science and technology》2013,47(5):349-361
This article summarizes the main results of a bench-scale program focused on experimentally assessing the aerosol retention near the tube breach in a tube bundle. The major variables investigated were particle nature (polydispersed TiO 2 agglomerates vs. solid, monodisperse SiO 2 spheres) and Re D (0.8?2.7· 10 5 ). In addition, comparisons to other data sets provided insights into the particle aerodynamic size effect on retention efficiency. Results showed that particle nature substantially affects aerosol retention in the tube bundle: mass retention efficiency was low for TiO 2 agglomerates (less than 30%) whereas it was much higher for SiO 2 particles (around 85%). Retention efficiency is also affected by Re D : its sensitivity was found to follow a log-normal behavior with a maximum retention attained at Re D near 1· 10 5 . This evolution with Re D was similar for both types of compounds. Particle size also influences retention efficiency: the bigger the TiO2 agglomerates the lower retention efficiency (no data were available for SiO 2 ). Among all these variables, particle nature was noted to have a prime importance for in-bundle retention, whereas Re D and particle aerodynamic size, although also affect retention efficiency, did not play such a key role. In light of the results, the presence of retention-inhibiting mechanisms such as fragmentation, resuspension or bouncing has been discussed. The data recorded will enhance the overall understanding of the governing mechanisms involved and will serve as a database against which compare model predictions. Nevertheless, further experimental data would be desirable to set up a sound database. 相似文献
1000.