全文获取类型
收费全文 | 2455篇 |
免费 | 134篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 31篇 |
综合类 | 1篇 |
化学工业 | 723篇 |
金属工艺 | 46篇 |
机械仪表 | 86篇 |
建筑科学 | 93篇 |
矿业工程 | 5篇 |
能源动力 | 108篇 |
轻工业 | 319篇 |
水利工程 | 25篇 |
石油天然气 | 18篇 |
无线电 | 135篇 |
一般工业技术 | 373篇 |
冶金工业 | 82篇 |
原子能技术 | 13篇 |
自动化技术 | 534篇 |
出版年
2024年 | 2篇 |
2023年 | 27篇 |
2022年 | 99篇 |
2021年 | 125篇 |
2020年 | 93篇 |
2019年 | 120篇 |
2018年 | 95篇 |
2017年 | 106篇 |
2016年 | 115篇 |
2015年 | 90篇 |
2014年 | 117篇 |
2013年 | 223篇 |
2012年 | 172篇 |
2011年 | 202篇 |
2010年 | 131篇 |
2009年 | 110篇 |
2008年 | 120篇 |
2007年 | 105篇 |
2006年 | 79篇 |
2005年 | 56篇 |
2004年 | 60篇 |
2003年 | 47篇 |
2002年 | 41篇 |
2001年 | 29篇 |
2000年 | 17篇 |
1999年 | 21篇 |
1998年 | 23篇 |
1997年 | 19篇 |
1996年 | 17篇 |
1995年 | 13篇 |
1994年 | 10篇 |
1993年 | 12篇 |
1992年 | 11篇 |
1991年 | 12篇 |
1989年 | 12篇 |
1988年 | 7篇 |
1987年 | 10篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1975年 | 2篇 |
1972年 | 1篇 |
1966年 | 1篇 |
1961年 | 1篇 |
1949年 | 1篇 |
排序方式: 共有2592条查询结果,搜索用时 15 毫秒
991.
Effect of calcium hydroxide on the bond strength of two bioactive cements and SEM evaluation of failure patterns 下载免费PDF全文
992.
993.
Rafael Ferraz Cella Guilherme Davi Mumbach Karina Luzia Andrade Patricia Oliveira Cintia Marangoni Ariovaldo Bolzan Samuel Bernard Ricardo Antonio Francisco Machado 《应用聚合物科学杂志》2018,135(18)
This study evaluated the thermal, morphological, chemical, and mechanical properties of virgin and recycled polystyrene. The recycling process was carried out by dissolution of polystyrene (extruded and crystal) in ethyl acetate, followed by two processes for solvent removal: vaporization by direct contact with water at 85 °C in a tubular evaporator and vaporization during the extrusion process. For the samples produced by solvent evaporation in the tubular evaporator, there was practically no degradation on polymer chain, neither reduction in glass transition temperature. For the samples produced by solvent evaporation during the extrusion, a polymer chain degradation was noted by reduction in molar weight and in glass transition temperature. The FTIR evaluation suggests that polymer oxidative degradation, in both samples, was more pronounced in the extruded sample. The removal of plasticizing additives could be evidenced by the glass transition temperature increase in the recycled samples produced in the tubular evaporator. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46208. 相似文献
994.
Crystallization,mechanical, and optical properties of transparent,nanocrystalline gahnite glass‐ceramics 下载免费PDF全文
Atiar R. Molla Alisson M. Rodrigues Shiv Prakash Singh Ricardo Felipe Lancelotti Edgar D. Zanotto Ana C.M. Rodrigues Mohammad Reza Dousti Andrea S.S. de Camargo Claudio José Magon Igor D′Anciães Almeida Silva 《Journal of the American Ceramic Society》2017,100(5):1963-1975
This paper describes the preparation of a transparent glass‐ceramic from the SiO2‐K2O‐ZnO‐Al2O3‐TiO2 system containing a single crystalline phase, gahnite (ZnAl2O4). TiO2 was used as a nucleating agent for the heat‐induced precipitation of gahnite crystals of 5‐10 nm. The evolution of the ZnAl2O4 spinel structure through the gradual formation of Al‐O bonds was examined by infrared spectroscopy. The dark brown color of the transparent precursor glass and glass‐ceramic was eliminated using CeO2. The increase in transparency of the CeO2‐doped glass and glass‐ceramics was demonstrated by UV‐visible absorption spectroscopy. EPR measurements confirmed the presence of Ce3+ ions, indicating that CeO2 was effective in eliminating the brown color introduced by Ti3+ ions via oxidation to Ti+4. The hardness of the glass‐ceramic was 30% higher than that of the as‐prepared glasses. This work offers key guidelines to produce hard, transparent glass‐ceramics which may be potential candidates for a variety of technological applications, such as armor and display panels. 相似文献
995.
Analysis and optimization of continuous organic solvent nanofiltration by membrane cascade for pharmaceutical separation 下载免费PDF全文
Ricardo Abejón Aurora Garea Angel Irabien 《American Institute of Chemical Engineers》2014,60(3):931-948
The major part of the production costs of pharmaceuticals can be imputed to the downstream processing, where membrane technologies have to deal with some challenges as separations involving solutes with similar sizes or solvent recovery and recycling. This work contributes to the progress in the design of continuous organic solvent nanofiltration systems for this purpose and includes the configuration of dual membrane cascades, sensitivity analysis of the operation variables, and economic optimization as innovations. Analyzed configurations include multistage cascades up to three stages, and dual membrane cascades up to five stages. The total costs (TC) were chosen as the formulated objective function to minimize in the economic optimization strategy. The treatment of the residual stream leaving the system resulted the main cost of the process (more than 85% for dual cascades), but the solvent recovery units can significantly reduce the TC (64–77% depending on the required solvent quality). © 2014 American Institute of Chemical Engineers AIChE J, 60: 931–948, 2014 相似文献
996.
Juan Castillo Tomas Lozano Ricardo Garcia Luisiana Morales-Zamudio Juventino López-Barroso Pierre G. Lafleur Shahir Karami Saul Sanchez-Valdes Guillermo Martinez-Colunga Francisco Rodriguez Catalina Perez-Berumen Sergio Flores Antonio García 《应用聚合物科学杂志》2020,137(10):48258
A study of the improvement of the mechanical and thermal properties of nanocomposites prepared with polypropylene (PP) and different graphene samples [graphene oxide (GO), reduced GO (RGO), and commercial graphene (G)] is presented. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy characterization were applied to the graphene samples. The nanocomposites were characterized by thermogravimetric analysis, XRD, differential scanning calorimetry, transmission electron microscopy (TEM), tensile, and impact resistance tests. PP/RGO nanocomposites showed significant improvement in mechanical and thermal properties. Sample PP/RGO-0.75 resulted in an increment in Young's modulus (51%), tensile strength (24%), and elongation at break (15%). This is attributed to a good dispersion state, a higher crystallinity percentage, and a good interfacial adhesion between PP and RGO. Sample PP/RGO-0.50 exhibited an increase of 197 °C in the temperature at which a loss in weight of 5% occurred, compared to that for pure PP. The height of stacked layers calculated by XRD measurements was similar to the value observed by TEM. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48258. 相似文献
997.
Kristiany Moreira Diniz Mariana Gava Segatelli César Ricardo Teixeira Tarley 《Reactive and Functional Polymers》2013,73(6):838-846
A hybrid copolymer [poly(ethylene glycol dimethacrylate-co-protoporphyrin)-silica], synthesized by free radical copolymerization and sol–gel process was evaluated as novel adsorbent for solid-phase extraction of Cd2+ ions. Characterization of hybrid polymer was performed by FTIR, SEM and surface area analyzes. Adsorption isotherms built at pH 8.9 were very well adjusted (R2 = 0.9982) to hybrid non-linear Langmuir–Freundlich model for two sites, indicating the existence of different affinity constants for binding sites, which was confirmed by Scatchard plot. The estimated maximum adsorption capacity was found to be 8.28 mg g?1. The adsorption kinetics data also corroborated to the isotherm, where the Cd2+ ions adsorption followed the pseudo-second-order kinetic (R2 = 0.998). The on-line preconcentration procedure, optimized by means of factorial designs, was based on sample preconcentration (16 mL) at pH 8.9 through 50.0 mg of hybrid copolymer packed in mini-column at 8.0 mL min?1 flow rate. The on-line desorption of Cd2+ ions towards the FAAS detector was carried out in countercurrent at 5.0 mL min?1 flow rate using 0.8 mol L?1 HNO3. Using the on-line preconcentration procedure, the maximum adsorption capacity determined from breakthrough curve was found to be 2.25 mg g?1. Analytical curve ranged from 0.0 up to 50.0 μg L?1 (r = 0.997), limit of detection of 0.27 μg L?1, preconcentration factor of 38.4, sample throughput of 30 h?1 and consumptive index of 0.41 mL, were achieved. The preconcentration method, very tolerable to several foreign ions, was successfully applied to the Cd2+ ions determination in water samples and cigarette sample. The accuracy was checked from analysis of certified reference materials. 相似文献
998.
Carmen Gutiérrez‐Lázaro Iñigo Bretos Ricardo Jiménez Jesús Ricote Hitham El Hosiny Dulce Pérez‐Mezcua Rafael J. Jiménez Rioboó Mar García‐Hernández Maria L. Calzada 《Journal of the American Ceramic Society》2013,96(10):3061-3069
Single‐BiFeO3 perovskite films onto Pt‐coated silicon substrates have been fabricated by chemical solution deposition using a synthesis strategy based on the use of nonhazardous reagents. Different routes were tested to obtain precursors for the deposition of the films, inferring that bismuth (III) nitrate and iron (III) 2,4‐pentanedionate dissolved in acetic acid and 1,3‐propendiol led to the best solution. Ferroelectric, magnetic, and optical functionalities were demonstrated in these films, obtaining a high ferroelectric polarization at room temperature, ~67 μC × cm?2, a dependence of the magnetization with the film thickness, 0.60 and 2.50 emu × g?1 for the ~215 and ~42‐nm‐thick films, and a direct band gap in the visible range, Eg ~2.82 eV. These results support the interest of solution methods for the fabrication of BiFeO3 thin films onto the silicon substrates required in microelectronic devices. 相似文献
999.
Cintia Marangoni Tiago Peruzzo Iaçanã G. B. Parisotto Valdete W. Ricardo Carlos A. Claumann Kenia W. Milanez 《Chemical Engineering Communications》2019,206(8):1006-1014
Based on previous results and a new proposal for the configuration of falling film distillation columns heated by a vapor chamber operating at atmospheric pressure, the present study analyzed a different application for heat transfer by means of an the axial temperature profile in the same vapor chamber, generated by the presence of non-condensable gases. Experimental tests were performed with an ethanol–water mixture by varying the feed flow rate and vapor chamber temperature. This new heat transfer proposal allowed the formation of a temperature gradient inside the distillation tube (similarly to the isothermal proposal previously reported), thus indicating that this heat transfer method is feasible for a distillation unit. The results demonstrated that higher flow rates are suitable for the distillation of ethanol and water in this new proposal; the temperature profile operation shows the feasibility of this new heat transfer proposal in falling film distillation columns and encourages further studies on the optimization of the process and the evaluation of the energy consumption. 相似文献
1000.
Marco Sangermano Monica Cerrone Giovanna Colucci Ignazio Roppolo Ricardo Acosta Ortiz 《Polymer International》2010,59(8):1046-1051
Hybrid thiol‐ene/epoxy coatings were prepared by combining thiol‐ene photo‐curable formulations with epoxy monomers, through a dual UV–thermal curing process. An increase in glass transition temperature and in storage modulus was observed for the hybrid thiol‐ene/epoxy coatings when compared with the pristine thiol‐ene UV‐cured system. Also, the bisphenol A moieties introduced into the hybrid networks during the dual‐curing process induced an increase in thermal stability of the cured materials. It has been demonstrated that the addition of epoxy monomer to the thiol‐ene photo‐curable system is a good strategy to follow in order to improve the final properties of thiol‐ene‐based coatings leading to a wide range of possible applications for the hybrid materials. Copyright © 2010 Society of Chemical Industry 相似文献