全文获取类型
收费全文 | 16940篇 |
免费 | 1541篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 88篇 |
综合类 | 9篇 |
化学工业 | 6572篇 |
金属工艺 | 160篇 |
机械仪表 | 379篇 |
建筑科学 | 627篇 |
矿业工程 | 26篇 |
能源动力 | 438篇 |
轻工业 | 4644篇 |
水利工程 | 150篇 |
石油天然气 | 102篇 |
无线电 | 633篇 |
一般工业技术 | 2243篇 |
冶金工业 | 651篇 |
原子能技术 | 42篇 |
自动化技术 | 1729篇 |
出版年
2024年 | 46篇 |
2023年 | 184篇 |
2022年 | 1158篇 |
2021年 | 1339篇 |
2020年 | 589篇 |
2019年 | 618篇 |
2018年 | 672篇 |
2017年 | 694篇 |
2016年 | 769篇 |
2015年 | 615篇 |
2014年 | 817篇 |
2013年 | 1228篇 |
2012年 | 1169篇 |
2011年 | 1311篇 |
2010年 | 988篇 |
2009年 | 943篇 |
2008年 | 843篇 |
2007年 | 783篇 |
2006年 | 590篇 |
2005年 | 439篇 |
2004年 | 382篇 |
2003年 | 327篇 |
2002年 | 302篇 |
2001年 | 177篇 |
2000年 | 138篇 |
1999年 | 166篇 |
1998年 | 132篇 |
1997年 | 130篇 |
1996年 | 114篇 |
1995年 | 83篇 |
1994年 | 73篇 |
1993年 | 70篇 |
1992年 | 72篇 |
1991年 | 49篇 |
1990年 | 41篇 |
1989年 | 50篇 |
1988年 | 38篇 |
1987年 | 42篇 |
1986年 | 46篇 |
1985年 | 39篇 |
1984年 | 32篇 |
1983年 | 24篇 |
1982年 | 21篇 |
1981年 | 18篇 |
1980年 | 22篇 |
1979年 | 19篇 |
1978年 | 24篇 |
1977年 | 14篇 |
1976年 | 8篇 |
1975年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
Ana M. García José M. Villora Diego A. Moreno Carlos Ranninger Pío Callejas M. Flora Barba 《Journal of the American Ceramic Society》2003,86(12):2200-2202
The objective of this research was to study the removal of cadmium and lead from an aqueous solution through a biological treatment. For this purpose a glass-ceramic material was manufactured from industrial and urban wastes. Biofilms of microorganisms found in wastewater were developed on its surface, and continuous tests were conducted in the presence and absence of the biofilm to analyze the glass-ceramic's ability to remove the heavy metals from an aqueous environment. The results suggest that this bioremediation process, developed on an industrial scale, could represent an alternative to the chemical processes currently used. 相似文献
62.
Daniela M. Nevskaia Maria Luisa Rojas Cervantes Antonio Guerrero Ruíz Juan de Dios Lpez Gonzlez 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,63(3):249-256
Adsorption of Triton X-100 on various silica substrates has been investigated. A number of solids, including a natural quartz, this quartz washed with HCl acid and subsequently heated at 1273 K; two aerosils and one Kieselgel silicas were studied. These solids exhibit surface areas in the range of 5 to 430 m2 g?1. All the Triton adsorption isotherms display an S-shape at the adsorption temperatures studied (298 and 308 K). It has been found that the pretreatments of natural quartz (by water washing, impurities removed by acid and/or high temperature calcination) affect considerably the amounts of TX-100 adsorbed. Measurements of surface composition have been made by X-ray photoelectron spectroscopy (XPS) with particular emphasis on the presence of impurities and on the number of OH groups at the surface of the samples. The nature of the surface hydroxyl has also been studied by infrared spectroscopy. Furthermore, the specific number of hydroxyl groups on the surface of the silica samples has been determined by thermogravimetric analysis. Finally an attempt to correlate solid surface characteristics with adsorption isotherms has been developed. 相似文献
63.
64.
65.
The possibilities of using monascus to colour gels were studied by comparing it with cochineal. Gels were prepared with four gelling agents—carrageenan, gellan, gelatine and xanthan—and their colour was measured with a Hunter Lab colorimeter. The equations relating L* and h with the concentrations of sugar [SU] and colorant [COL] were deduced, and it was found that [COL] had more influence on colour than [SU]. In general, for these four gelling agents the colour of monascus gels is orange-red and the colour of cochineal gels is purplish red. The gels made with xanthan were always the lightest, whether they were made with cochineal or with monascus. 相似文献
66.
67.
Maria Zemankova 《Information Systems》1989,14(6):473-486
FILIP (fuzzy intelligent learning information processing) system is designed with the goal to model human information processing. The issues addressed are uncertain knowledge representation and approximate reasoning based on fuzzy set theory, and knowledge acquisition by “being told” or by “learning from examples”. Concepts that can be “learned” by the system can be imprecise (fuzzy), or the knowledge can be incomplete. In the latter case, FILIP uses the concept of similarity to extrapolate the knowledge to cases that were not covered by examples provided by the user. Concepts are stored in the Knowledge Base and employed in intelligent query processing, based on flexible inference that supports approximate matches between the data in the database and the query.
The architecture of FILIP is discussed, the learning algorithm is described, and examples of the system's performance in the knowledge acquisition and querying modes, together with its explanatory capabilities are shown. 相似文献
68.
Larissa Canilha Walter Carvalho Marco Giulietti Maria Das Graças Almeida Felipe João Batista Almeida E Silva 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(5):715-721
BACKGROUND: Xylitol bioproduction from lignocellulosic residues comprises hydrolysis of the hemicellulose, detoxification of the hydrolysate, bioconversion of the xylose, and recovery of xylitol from the fermented hydrolysate. There are relatively few reports on xylitol recovery from fermented media. In the present study, ion‐exchange resins were used to clarify a fermented wheat straw hemicellulosic hydrolysate, which was then vacuum‐concentrated and submitted to cooling in the presence of ethanol for xylitol crystallization. RESULTS: Sequential adsorption into two anion‐exchange resins (A‐860S and A‐500PS) promoted considerable reductions in the content of soluble by‐products (up to 97.5%) and in medium coloration (99.5%). Vacuum concentration led to a dark‐colored viscous solution that inhibited xylitol crystallization. This inhibition could be overcome by mixing the concentrated medium with a commercial xylitol solution. Such a strategy led to xylitol crystals with up to 95.9% purity. The crystallization yield (43.5%) was close to that observed when using commercial xylitol solution (51.4%). CONCLUSION: The experimental data demonstrate the feasibility of using ion‐exchange resins followed by cooling in the presence of ethanol as a strategy to promote the fast recovery and purification of xylitol from hemicellulose‐derived fermentation media. Copyright © 2008 Society of Chemical Industry 相似文献
69.
Cypriano G da Trindade Neto Ana LP Fernandes Ana IB Santos Waldenice A Morais Marcos VM Navarro Tereza NC Dantas Mrcia R Pereira Jos LC Fonseca 《Polymer International》2005,54(4):659-666
Complexation of chitosan in aqueous solutions by low molecular weight electrolytes is one of the simplest methods for the preparation of aqueous chitosan dispersions. In this work, the influence of storage time, sulfate concentration, method of preparation and surfactant content on some properties of the resultant chitosan dispersions (turbidity, viscosity and zeta potential) was analyzed. Turbidimetry was adequate to monitor the formation of particles, while viscometry was suitable to monitor changes in the dispersing phase. An analysis of the properties of these systems, mainly in terms of particle–particle and macromolecule–macromolecule interactions was carried out. Copyright © 2004 Society of Chemical Industry 相似文献
70.
The thermal and mechanical properties and the morphologies of blends of poly(propylene) (PP) and an ethylene–(vinyl alcohol) copolymer (EVOH) and of blends of PP/EVOH/ethylene–(methacrylic acid)–Zn2+ ionomer were studied to establish the influence of the ionomer addition on the compatibilization of PP/EVOH blends and on their properties. The oxygen transmission rate (O2TR) values of the blends were measured as well. PP and EVOH are initially incompatible as was determined by tensile tests and scanning electronic microscopy. Addition of the ionomer Zn2+ led to good compatibility and mechanical behaviour was improved in all blends. The mechanical properties on extruded films were studied for 90/10 and 80/20 w/w PP/EVOH blends compatibilized with 10 % of ionomer Zn2+. These experiments have shown that the tensile properties are better than in the injection‐moulded samples. The stretching during the extrusion improved the compatibility of the blends, diminishing the size of EVOH domains and enhancing their distribution in the PP matrix. As was to be expected, the EVOH improved the oxygen permeation of the films, even in compatibilized blends. Copyright © 2004 Society of Chemical Industry 相似文献