全文获取类型
收费全文 | 87349篇 |
免费 | 9550篇 |
国内免费 | 4918篇 |
专业分类
电工技术 | 7230篇 |
技术理论 | 9篇 |
综合类 | 6663篇 |
化学工业 | 12845篇 |
金属工艺 | 5199篇 |
机械仪表 | 5618篇 |
建筑科学 | 7111篇 |
矿业工程 | 2994篇 |
能源动力 | 2687篇 |
轻工业 | 5570篇 |
水利工程 | 2205篇 |
石油天然气 | 4246篇 |
武器工业 | 959篇 |
无线电 | 10521篇 |
一般工业技术 | 9725篇 |
冶金工业 | 3605篇 |
原子能技术 | 1289篇 |
自动化技术 | 13341篇 |
出版年
2024年 | 471篇 |
2023年 | 1625篇 |
2022年 | 3354篇 |
2021年 | 4523篇 |
2020年 | 3375篇 |
2019年 | 2703篇 |
2018年 | 2952篇 |
2017年 | 3255篇 |
2016年 | 3025篇 |
2015年 | 4110篇 |
2014年 | 5051篇 |
2013年 | 5881篇 |
2012年 | 6565篇 |
2011年 | 7047篇 |
2010年 | 6116篇 |
2009年 | 5721篇 |
2008年 | 5459篇 |
2007年 | 5019篇 |
2006年 | 4810篇 |
2005年 | 3859篇 |
2004年 | 2755篇 |
2003年 | 2238篇 |
2002年 | 2240篇 |
2001年 | 1781篇 |
2000年 | 1498篇 |
1999年 | 1363篇 |
1998年 | 971篇 |
1997年 | 766篇 |
1996年 | 754篇 |
1995年 | 539篇 |
1994年 | 456篇 |
1993年 | 342篇 |
1992年 | 289篇 |
1991年 | 187篇 |
1990年 | 166篇 |
1989年 | 124篇 |
1988年 | 117篇 |
1987年 | 59篇 |
1986年 | 51篇 |
1985年 | 36篇 |
1984年 | 23篇 |
1983年 | 16篇 |
1982年 | 20篇 |
1981年 | 11篇 |
1980年 | 15篇 |
1979年 | 15篇 |
1978年 | 7篇 |
1976年 | 12篇 |
1959年 | 12篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
31.
Soap‐free emulsion copolymerization of perfluoroalkyl acrylate (FA)/methyl methacrylate (MMA)/n‐butyl acrylate (n‐BA) was carried out in the presence of sodium 2‐acrylamide‐2‐methyl propanesulfonate (AMPSNa) as a reactive surfactant and potassium persulfate (KPS) as an initiator. An analysis of the effects of concentration of AMPSNa, KPS, FA as well as polymerization temperature on the kinetic features (rate of polymerization) and colloidal characteristics (mean particle diameter, particle disperse index, particle numbers, and surface charge density) was followed. NMR, FTIR, AFM, and fluorine‐selective electrode analysis were used to characterize the composition and morphology of the FA copolymers. Both AFM analysis and contact angle measurements strongly implied that the fluorinated segments migrated to the outmost surface and created films with lower surface energy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2438–2444, 2007 相似文献
32.
Centimeter-size multi-branched tree-like carbon structures have been generated by the catalytic chemical vapor deposition of toluene using ferrocene as the catalyst precursor and investigated by means of SEM, TEM, and EDX. It is found that a temperature of 1000-1200 °C and a carrier gas flow rate of 1000-2500 ml/min are necessary for the generation of the carbon trees. Their morphologies and microstructures change greatly with the changing reaction conditions. The fractal dimensions of the trees are calculated to quantitatively investigate the influence of different reaction temperatures on the morphologies. 相似文献
33.
34.
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
35.
36.
Li?QiuxiaoEmail author Zhang?Gaoyong Peng?Shaoyi 《Journal of surfactants and detergents》2002,5(3):229-233
Amination of fatty alcohols by hydrogenation and dehydrogenation catalysis is one of the main commercial processes for the
production of dimethylalkylamines. The key factor in this process is the preparation of catalysts with high selectivity. A
study of amination catalyzed by Cu−Ni catalysts supported on CaCO3 is reported in this paper. Selectivity of the catalysts was adjustable by varying the ratio of Cu to Ni or by adding a third
element (Zn or Mg). The promotion of catalyst selectivity was mainly attributable to the effect of the components on the reducibility
of Ni2+ in the catalysts. Lower reducibility of Ni2− led to higher catalyst selectivity. 相似文献
37.
论文分析了S/PDIF音频数据流的特点,引入模式识别中的训练机对S/PDIF音频数据流进行现场脉冲宽度特征提取。依据训练机结果建立分类器实现脉冲宽度分类,根据脉冲宽度进行同步前置码和逻辑电平的解码。利用硬件描述语言Verilog进行设计实现与验证,仿真结果说明这种特征提取方法可以提高S/PDIF接收机数据解译码的适应性和准确性。 相似文献
38.
Microcellular foaming of biodegradable Bionolle in supercritical CO2 has been produced. The effects of a series of variable factors, such as saturation temperature, saturation pressure, and depressurization time and step on the foam structures and density, were studied through measurement of density and SEM observation. The experimental results show that higher saturation temperatures lead to an increase in bulk densities; and different depressurization time and step result in different product cell morphology. In addition, at some saturation temperature, the orientation of the cells can be found in the product morphology. XRD experimental results show that the foaming treatment with SC CO2 increased the crystallinity of Bionolle. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2901–2906, 2006 相似文献
39.
GAO Lin LI Sheng JIN HongGuang & LIN Hu Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing China Graduate School of Chinese Academy of Sciences Beijing 《中国科学:信息科学(英文版)》2010,(1)
On basis of adopting polygeneration systems for power and alternative fuels,capturing CO2 with near zero energy penalties,and storing CO2 on sites,a new kind of Energy Network can integrate energy utilization,CO2 capture,transportation and storage synthetically.Techno-economic analysis of this solution focusing on Inner Mongolia and the Yangtze River Delta districts had been carried with comparison to the chain method for energy utilization and CO2 sequestration.This solution can save 21.5% of energy,and re... 相似文献
40.
DALLY B B 《中国科学:信息科学(英文版)》2011,(2)
Moderate or intense low oxygen dilution(MILD)combustion plays a significant role in the mitigation of combustion-generated pollutants and greenhouse gases whilst meeting thermal efficiency needs.However,due to the lack of the fundamental knowledge on this combustion,there is a misconception that MILD combustion should be established by high preheating of the air,which has limited its application.Our research and development on this combustion has been performed for several years. We have found that the requ... 相似文献