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931.
Synthesis and characterization of interpenetrating polymer network based on sodium alginate and methacrylic acid and potential application for immobilization of TiO2 nanoparticles 下载免费PDF全文
Marija Lučić Škorić Nedeljko Milosavljević Maja Radetić Zoran Šaponjić Marija Radoičić Melina Kalagasidis Krušić 《Polymer Engineering and Science》2015,55(11):2511-2518
An interpenetrating polymer network (IPN) based on the sodium alginate (A) and partially neutralized poly(methacrylic acid) (MAA) was prepared by free radical polymerization followed by additional cross‐linking of sodium alginate with calcium ions. Obtained material (A/MAA IPN) was characterized by FTIR spectroscopy, thermogravimetric analysis, scanning electron microscopy, and rheological measurements. Swelling behavior of synthetized IPN has been also investigated. TiO2 nanoparticles (TiO2 NPs) were immobilized onto A/MAA IPN by dip‐coating method and obtained TiO2/IPN nanocomposite was used for removal of the methylene blue (MB) from aqueous solution. The photodegradation (under illumination) and sorption (in the dark) processes for dye removal were monitored through decrease of dye concentration in the solution by UV/VIS spectrometer. The TiO2/IPN nanocomposite sorbed approximately 93% of the MB from a 10 mg L?1 MB solution in the dark, but no degradation occurred. Likewise, more than 93% of dye was removed after 8 h of illumination. However, after 24 h of illumination, the samples were discolored indicating that dye molecules were successfully degraded. Thus, the TiO2/IPN nanocomposite could be utilized in the photodegradation–sorption process for the abatement of pollutants in water. POLYM. ENG. SCI., 55:2511–2518, 2015. © 2015 Society of Plastics Engineers 相似文献
932.
Novel Utilization of Fly Ash for High‐Temperature Mortars: Phase Composition,Microstructure and Performances Correlation 下载免费PDF全文
Anja Terzić Ljubica Pavlović Zagorka Radojević Vladimir Pavlović Vojislav Mitić 《International Journal of Applied Ceramic Technology》2015,12(1):133-146
In this study, the feasibility of using fly ash to manufacture high‐temperature mortars was investigated. The investigation was set to define preliminary characteristics of new types of mortars based on ordinary and/or refractory cement with fly ash addition, and to establish mutual correlation between thermally induced changes of mineral phases, microstructure, and final performances of the mortars. New mortars, made up of 21% cement (PC‐CEM I 42.5R/HAC‐Secar 70/71), 70% river sand, and 9% fly ash, were chemically, physically, and mechanically characterized to determine possibilities of fly ash re‐utilization for high‐temperature purposes. The fly ash samples, which originated from four different power plants, were mechanically activated. Mortars were heat‐treated up to 1300°C in a laboratory tunnel furnace with retention time 2 h. Thermal stability of crystalline phases were studied by differential thermal analysis (DTA); thermally induced changes in mineral phase composition were analyzed by XRD; and microstructure were investigated by scanning electron microscopy. Correlated results of DTA, XRD, and SEM analyses indicated initiation of sintering processes at approximately 1300°C and formation of thermally stable minerals (rankinite, gehlenite, anorthite, cristobalite). The investigation highlights a sustainable approach of using fly ash in developing ecofriendly mortars for high‐temperature application. 相似文献
933.
Aleksandar Radojković Danijela Luković Golić Jovana Ćirković Zorica Marinković Stanojević Damir Pajić Filip Torić Aleksandra Dapčević Predrag Vulić Zorica Branković Goran Branković 《Ceramics International》2018,44(14):16739-16744
Bulk ceramic samples of BiFeO3 were light doped (up to 1%) with Nb5+ in the place of Fe3+ (B-site doping) and their multiferroic properties were investigated using XRD, SEM, polarization (PMTS) and magnetization (SQUID) techniques. It is shown that even the small percentages of doping can notably change electric and magnetic behavior. Electric conductivity differs by two orders of magnitude between samples doped with 0.2% and 1% Nb. The ferroelectric behavior strongly depended on conduction mechanism, and transition from space-charge-limited current (SCLC) conduction to trap-filled limited (TFL) conduction regime reflected on a change in hysteresis patterns, particularly for the samples with 0.2% and 0.5% Nb. Separation of ZFC-FC magnetization curves occurred for all Nb concentrations and increased with Nb doping. Weak ferromagnetic behavior and the increase of remnant magnetization with Nb concentration was observed from the hysteresis measurements. Coercive field changed drastically compared to the pure BiFeO3, namely, the sample with 1% Nb exhibited very high coercive magnetic field of ~ 10?kOe. 相似文献
934.
Experimental and theoretical consideration of the factors influencing cationic pollutants retention by seashell waste 下载免费PDF全文
935.
Owing to their ability to adsorb at interfaces, polysorbates have an important role in pharmaceutical formulations. Because surfactant mixtures can have improved properties, it was hypothesized in this work that introduction of poloxamer 407 to aqueous solutions of polysorbates (polysorbate 60, polysorbate 80 and polysorbate 85) might improve their surface properties. Nonideal behavior of surfactant mixtures at the air/water interface was investigated using Rosen's model and recently introduced method for the determination and quantification of nonideal behavior regarding surface tension reduction and adsorption effectiveness. Although nonideal behavior was noticed in all mixed monolayers, it was shown that the structure of the hydrophobic domain of the polysorbates and the conformation of poloxamer 407 at the interface have strong influence on the nonideality. 相似文献
936.
Hydrodynamics,mass transfer,and photocatalytic phenol selective oxidation reaction kinetics in a fixed TiO2 microreactor 下载免费PDF全文
Matic Krivec Andrej Pohar Blaž Likozar Goran Dražić 《American Institute of Chemical Engineers》2015,61(2):572-581
Photocatalytic phenol dissociation was studied in a microreactor, with a TiO2 layer immobilized on the reactor inner walls. Experiments were conducted for various residence times, initial concentrations, pH values, and UV light irradiation intensities. The intermediates and products (catechol, hydroquinone, and resorcinol) were quantitatively investigated to determine the predominant reaction pathways for the investigated anatase catalyst. A three‐dimensional mathematical model was used to simulate the heterogeneous photocatalysis reaction conditions with Langmuir–Hinshelwood mechanism, considering the adsorption/desorption thermodynamic equilibria, and for kinetic parameter estimation via regression analysis. The effectiveness factor, Thiele modulus, and the correction function were calculated to determine the pore diffusion effects. The value of pH had the dramatic effect of lowering the reaction rate due to the competitive adsorption of hydroxide ions and protons on the catalyst surface. A phenol conversion of 79.5% was achieved at the residence time of 7.22 min, but without total mineralization. © 2014 American Institute of Chemical Engineers AIChE J, 61: 572–581, 2015 相似文献
937.
Oskar Bera Jelena Pavličević Bojana Ikonić Jelena Lubura Dragan Govedarica Predrag Kojić 《Polymer Engineering and Science》2021,61(3):879-890
Although extensive research has been carried out on the understanding of the complex vulcanization process, the influence of reversion through exposure time and temperature on the vulcanization degree remains unclear. Therefore, the main aim of this study was a novel optimization approach that can help the industrial practitioners to select the optimal operating parameters, exposure time, and molding temperature, to achieve desired vulcanization degree of selected product. Spheres of four different diameters (2.5, 5, 10, and 20 cm) were selected as test geometry for simulation and optimization of rubber molding. Obtained vulcanization rheometer data for commercially available rubber blend (NR/SBR) were fitted by a new modeling approach, dividing vulcanization curve into two fitting sets: curing and reversion. The heat transfer equations for chosen geometry were coupled with proposed kinetic model. A new temperature-dependent kinetic parameter x, as the maximal reversion degree, was introduced, enabling determination of the lowest operating molding temperature (Tmin = 132.36 °C), preventing high reversion and overheating of the rubber product. The final optimization goal was assessment of the optimal temperature and vulcanization time dependence on the rubber products dimensions. Proposed models have precise prediction with R2 values greater than 0.8328 and MAPE less than 2.3099%. 相似文献
938.
Jian Hong Dragana Radojčić Xiao-Qin Yang Xianmei Wan Zoran S. Petrović 《应用聚合物科学杂志》2020,137(13):48509
Rubber seed oil (RSO), extracted from the seeds of rubber trees, is inedible oil with high free fatty acid content. In order to add value to RSO, we prepared a polyol with primary OH groups via hydroformylation/hydrogenation. Free hydroxy fatty acids formed in the process were utilized as reactive diluents, viscosity reducers, and adhesion promoters through hydrogen bonding with the substrate. The structures of the oil and polyol were analyzed using a range of analytical methods. The polyol had a hydroxyl number of 244 mg KOH g−1 and an acid number of 21 mg KOH g−1. The polyurethane prepared from this polyol and diphenylmethane diisocyanate was a highly crosslinked, tough material with a glass transition at 44 °C, high tensile strength and elongation, and attractive electrical properties. When used as a wood adhesive, it displayed extraordinary shear strength characterized by substrate wood failure rather than cohesive failure of the polymer. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48509. 相似文献
939.
Dr. Kamil J. Kuder Michał Załuski Jakub Schabikowski Dr. Gniewomir Latacz Agnieszka Olejarz-Maciej Piotr Jaśko Agata Doroz-Płonka Andreas Brockmann Prof. Christa E. Müller Prof. Katarzyna Kieć-Kononowicz 《ChemMedChem》2020,15(9):772-786
Annelated purinedione derivatives have been shown to act as possible multiple-target ligands, addressing adenosine receptors and monoaminooxidases. In this study, based on our previous results, novel annelated pyrimido- and diazepino[2,1-f]purinedione derivatives were designed as dual-target-directed ligands combining A2A adenosine receptor (AR) antagonistic activity with blocking monoamine oxidase B. A library of 19 novel compounds was synthesized and biologically evaluated in radioligand binding studies at AR subtypes and for their ability to inhibit MAO-B. This allowed 9-(2-chloro-6-fluorobenzyl)-3-ethyl-1-methyl-6,7,8,9-tetrahydropyrimido[2,1-f]purine-2,4(1H,3H)-dione ( 13 e ; Ki human A2AAR: 264 nM and IC50 human MAO-B: 243 nM) to be identified as the most potent dual-acting ligand from this series. ADMET parameters were estimated in vitro, and analysis of the structure-activity relationships was complemented by molecular-docking studies based on previously published X-ray structures of the protein targets. Such dual-acting ligands, by selectively blocking A2A AR, accompanied by the inhibition of dopamine metabolizing enzyme MAO-B, might provide symptomatic and neuroprotective effects in, among others, the treatment of Parkinson disease 相似文献
940.
Summary
The results of investigating starch benzoate (SB) synthesis in aqueous media are presented in this study. Starch esterification
with benzoyl chloride was performed in two steps, the first step being the alkalization of starch and the second step esterification.
The influence of the concentration of reactants, reaction medium composition, temperature and time of synthesis on the degree
of substitution (DS), degree of swelling in water and thermal stability of the synthesized starch benzoate was investigated.
The optimal conditions for the synthesis of starch benzoate with degree of substitution from 0.23 to 1.76 were determined.
It was shown that starch benzoate with a DS of 1.76 practically did not swell in water. However, starch benzoate is less thermally
stable than native starch probably due to a change in the supermolecular order induced by the esterification reaction.
Received: 18 March 2002/Revised version: 18 October 2002/ Accepted: 28 October 2002
Correspondence to Katarina Jeremić 相似文献