全文获取类型
收费全文 | 32460篇 |
免费 | 2482篇 |
国内免费 | 1282篇 |
专业分类
电工技术 | 1730篇 |
技术理论 | 1篇 |
综合类 | 1951篇 |
化学工业 | 5633篇 |
金属工艺 | 1615篇 |
机械仪表 | 2122篇 |
建筑科学 | 2583篇 |
矿业工程 | 1015篇 |
能源动力 | 837篇 |
轻工业 | 1995篇 |
水利工程 | 552篇 |
石油天然气 | 2079篇 |
武器工业 | 212篇 |
无线电 | 3798篇 |
一般工业技术 | 3960篇 |
冶金工业 | 1606篇 |
原子能技术 | 383篇 |
自动化技术 | 4152篇 |
出版年
2024年 | 174篇 |
2023年 | 588篇 |
2022年 | 892篇 |
2021年 | 1269篇 |
2020年 | 936篇 |
2019年 | 843篇 |
2018年 | 929篇 |
2017年 | 997篇 |
2016年 | 870篇 |
2015年 | 1162篇 |
2014年 | 1551篇 |
2013年 | 1839篇 |
2012年 | 1962篇 |
2011年 | 2048篇 |
2010年 | 1801篇 |
2009年 | 1763篇 |
2008年 | 1622篇 |
2007年 | 1645篇 |
2006年 | 1785篇 |
2005年 | 1599篇 |
2004年 | 1022篇 |
2003年 | 935篇 |
2002年 | 897篇 |
2001年 | 780篇 |
2000年 | 892篇 |
1999年 | 957篇 |
1998年 | 786篇 |
1997年 | 694篇 |
1996年 | 679篇 |
1995年 | 531篇 |
1994年 | 436篇 |
1993年 | 324篇 |
1992年 | 258篇 |
1991年 | 202篇 |
1990年 | 152篇 |
1989年 | 118篇 |
1988年 | 97篇 |
1987年 | 50篇 |
1986年 | 35篇 |
1985年 | 28篇 |
1984年 | 17篇 |
1983年 | 17篇 |
1982年 | 22篇 |
1981年 | 13篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
Biodiesel was produced by transesterification of soybean oil with methanol using ZnO loaded with KF as a solid base catalyst.
It was found that the catalyst with 15 wt.% KF loading and calcined at 873 K showed the optimum activity. XRD, IR and Hammett
indicator method were employed for the catalyst characterization. The results showed the activity of the catalysts was correlated
with their basicity. The influence of various reaction variables on the conversion was also discussed. 相似文献
43.
In this study, the reaction kinetics of asymmetric polymer-polymer interface was experimentally and theoretically studied. A new rheological method correlating the change of rheological property of reactive system with the conversion of the in situ formed copolymers was applied to study the reaction kinetics of PBT/epoxy reactive system. Then, the new method was proved to be useful by comparing its results with that obtained from the conventional endgroup determination method. Moreover, the conversion of PBT/epoxy reactive system from rheological method could be well fitted by the numerical analysis, from which the kinetic constant and the diffusion constant of epoxy in PBT could be determined simultaneously. 相似文献
44.
Modification of silk with aminated polyepichlorohydrin to improve dyeability with reactive dyes 总被引:1,自引:0,他引:1
Xie Weibin He Jinxin Chen Shuilin Chen Guoqiang Peng Taozhi 《Coloration Technology》2007,123(2):74-79
Reactive dyes have almost complete exhaustion and ideal fixation on aminated polyepichlorohydrin pretreated silk without addition of salt or alkali. The effects of varying pretreatments and dyeing conditions were studied. The dyeing behaviour of CI Reactive Red 15 on modified silk under pH 6 was investigated. Dyeings of modified silk showed good wash fastness, dry and wet rub fastnesses as well as light fastness. The quality of the dyed silks obtained after pretreatment was shown to be satisfactory and the dyeing effluent was less polluted. 相似文献
45.
Lijin Xie Junfeng Ma Jun Zhou Zhongqiang Zhao Hua Tian Yonggang Wang Jiantao Tao Xiaoyi Zhu 《Journal of the American Ceramic Society》2006,89(5):1717-1720
Well-crystallized bismuth tungstate (Bi2 WO6 ) powders with different morphologies were successfully synthesized via a low-temperature molten salt method. The powders were characterized by X-ray diffraction, transmission electron microscopy, and UV-Vis, respectively. It was found that the variation of morphology of the obtained Bi2 WO6 powder mainly depends on the different reaction temperatures and the weight ratio of LiNO3 –NaNO3 salt to precursor. In addition, the UV-Visible absorption spectra showed that the synthesized powders had strong light absorption properties not only in the ultraviolet light but also in the visible light region. 相似文献
46.
Alumina supported vanadia catalysts (V/Al) for selective oxidehydrogenation of ethylbenzene with CO2 were prepared by impregnation method. During preparation the effect of promoters and calcined temperature was investigated,
it was found these two items had a strong influence on the activity of V/Al catalysts. Dehydrogenation reaction with CO2 was happened in the fixed-bed reactor at 450 °C. Results showed that 15.2% ethylbenzene conversion and 99.2% styrene selectivity
were acquired when V2K/Al catalyst was used. 相似文献
47.
A three-dimensional model is proposed for both furnace-side and wall-side heat transfer in circulating fluidized beds with membrane walls. Following previous publications (Int. J. Heat Mass Transfer (2003a, b)), a core-annulus flow structure is employed in the model, with consideration of the membrane wall influence on bed hydrodynamics. The model couples radiation, conduction and convection on the furnace side to conduction and convection on the wall side. Radiation in the wall layer is simulated by the moment method. A finite-element method is employed to solve the set of non-linear, partial differential equations. The solution is demonstrated for a typical example. The model gives predictions of suspension-to-wall heat transfer which show satisfactory agreement with published experimental data. 相似文献
48.
Colloidal suspensions containing salts of poly(methacrylic acid) which exhibit high electrorheological (ER) activity were synthesized by inverse emulsion polymerization. Factors influencing the ER effect were studied. The results showed that maximum yield stress occurred at optimum amounts of both polymeric stabilizer and crosslinking agent used in the inverse emulsion polymerization as well as a certain water content of the particles, while yield stress increased with electric field strength, average diameter of the particles below 0.9 μm, or the molar ratio of the salt to the acid. The ER activity for the suspensions containing different monovalent counter ions decreased in the following order: Li+ > Na+ > K+ > NH4+. The phenomena were discussed with the ionic polarization mechanism. © 1995 John Wiley & Sons, Inc. 相似文献
49.
在全球性事件的大背景下,流行趋势研究更能显示出其价值,本文通过分析经济危机下时装行业的最新动态,总结并预测时装流行及时装业发展的未来走向,可以提供给中国时装业一些思考。 相似文献
50.
计算机用于化工设计有着独特的优点。比如在分子模拟、稳态流程模拟和计算机辅助设计(Computer Aided Design)等领域。化工设计者应敏锐地看到计算机技术在化工设计中显示出的发展潜力。 相似文献