首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   249篇
  免费   12篇
  国内免费   2篇
电工技术   3篇
综合类   1篇
化学工业   75篇
金属工艺   8篇
机械仪表   5篇
建筑科学   16篇
能源动力   16篇
轻工业   19篇
石油天然气   4篇
无线电   17篇
一般工业技术   34篇
冶金工业   22篇
原子能技术   8篇
自动化技术   35篇
  2024年   2篇
  2023年   11篇
  2022年   8篇
  2021年   16篇
  2020年   15篇
  2019年   11篇
  2018年   14篇
  2017年   10篇
  2016年   11篇
  2015年   6篇
  2014年   9篇
  2013年   24篇
  2012年   6篇
  2011年   10篇
  2010年   10篇
  2009年   26篇
  2008年   22篇
  2007年   10篇
  2006年   6篇
  2005年   2篇
  2004年   2篇
  2003年   5篇
  2000年   1篇
  1999年   1篇
  1998年   5篇
  1997年   2篇
  1996年   5篇
  1992年   3篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1984年   1篇
  1983年   1篇
  1979年   1篇
  1977年   3篇
  1976年   1篇
排序方式: 共有263条查询结果,搜索用时 15 毫秒
101.
The incorporation of imidazolium‐based ionic liquids into a poly(ether sulfone) (PES) polymeric membrane resulted in a dense and void‐free polymeric membrane. As determined through the ideal gas permeation test, the carbon dioxide (CO2) permeation increased about 22% compared to that of the pure PES polymeric membrane whereas the methane (CH4) permeation decreased tremendously. This made the CO2/CH4 ideal separation increase substantially by more than 100%. This study highlighted the utilization of imidazolium‐based ionic liquids in the synthesis of ionic liquid polymeric membranes (ILPMs). Two different ionic liquids were used to compare the CO2 separation performance through the membranes. The glass‐transition temperatures (Tgs) of ILPMs were found to be lower than the Tg of the pure PES polymeric membranes; this supported the high CO2 permeation of the ILPMs due to the increase in PES flexibility caused by ionic liquid addition. The results also draw attention to new trends of ionic liquids as a potential green candidates for future membrane synthesis. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43999.  相似文献   
102.
A poly(linolenic acid)‐g‐poly(tert‐butyl acrylate) graft copolymer was synthesized from polymeric linolenic acid peroxide possessing peroxide groups in the main chain by free radical polymerization of tert‐butyl acrylate. Graft copolymers having structures of poly(linolenic acid)‐g‐poly(caprolactone)‐g‐poly(tert‐butyl acrylate) were synthesized from polymeric linolenic acid, possessing peroxide groups on the main chain by the combination of free radical polymerization of tert‐butyl acrylate and ring‐opening polymerization of ε‐caprolactone in one‐pot. The obtained graft copolymers were characterized by proton nuclear magnetic resonance, gel permeation chromatography, thermal gravimetric analysis, differential scanning calorimetry, and scanning electron microscopy techniques. Furthermore, Au/n‐Si diodes were fabricated with and without poly(linolenic acid)‐g‐poly(caprolactone)‐g‐poly(tert‐butyl acrylate)‐4 to form a new interfacial polymeric layer for the purpose of investigating this polymer's conformity in electronic applications. Some main electrical characteristics of these diodes were investigated using experimental current–voltage measurements in the dark and at room temperature.  相似文献   
103.
Nanostructured M-type hexaferrite Ba1?x Ca x Fe11.5Cr0.5O19 (x=0.0–0.5) powders have been synthesized by means of the sol-gel autocombustion method. The materials are characterized by differential scanning calorimetry, thermogravimetry, Fourier transform infra-red spectroscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and vibrating sample magnetometry. X-ray diffraction analysis confirms the formation of M-type hexagonal phase and few traces of α-Fe2O3 are also observed. The c/a ratio falls in the expected range from a value of 3.97 to 3.94 of M-type hexaferrites. The average crystallite size is found to be in the range 15 to 36 nm, which is good enough to obtain the suitable signal-to-noise ratio in the high-density recording media. DC electrical resistivity at room temperature enhances up to 11.2×109 Ω?cm (x=0.4) and then drops upon increasing the Ca2+ contents further. The magnetic properties such as saturation magnetization (M s ), remanence (M r ), squareness ratio (M r /M s ) and coercivity (H c ) are calculated from the MH-loops. The maximum magnetization and remanence reduces from a value of 52 to 33 and 33 to 16 emu/g, respectively, which attributes to the decrease of magnetic moment, and hence reduction in the superexchange interaction. The coercivity enhances from 4378 to 4706 Oe, which attributes to the increase in magnetocrystalline anisotropy due to the reduction of particle size. Owing to these properties, the synthesized nanomaterials can be considered useful for high-density recording media and permanent magnets.  相似文献   
104.
Two studies test the assertion that anger, sadness, fear, pride, and happiness are typically narrated in different ways. Everyday events eliciting these 5 emotions were narrated by young women (Study 1) and 5- and 8-year-old girls (Study 2). Negative narratives were expected to engender more effort to process the event, be longer, more grammatically complex, more often have a complication section, and use more specific emotion labels than global evaluations. Narratives of Hogan’s (2003) juncture emotions anger and fear were expected to focus more on action and to contain more core narrative sections of orientation, complication, and resolution than narratives of the outcome emotions sadness and happiness. Hypotheses were confirmed for adults except for syntactic complexity, whereas children showed only some of these differences. Hogan’s theory that juncture emotions are restricted to the complication section was not confirmed. Finally, in adults, indirect speech was more frequent in anger narratives and internal monologue in fear narratives. It is concluded that different emotions should be studied in how they are narrated, and that narratives should be analyzed according to qualitatively different emotions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
105.
In this study, an organic semiconductor 5,10,15,20-tetrakis(4′-isopropylphenyl) porphyrin (TIPP) was synthesized and investigated as an active material in surface-type multifunctional sensor. As electrodes, 100 nm thick Ag films were deposited on 25 mm × 25 mm glass substrate with 40 μm gap between them. Thin film of TIPP of area 15 mm × 15 mm was thermally sublimed to cover the gap between the silver electrodes. Thickness of TIPP film was 100 nm. A change in electrical resistance and capacitance of the fabricated device was observed with the increase in relative humidity (RH), temperature, and illumination. Hysteresis, response, and recovery times were investigated over a wide range of RH (0–94%). Activation energy of the TIPP was estimated. An equivalent circuit of the Ag/TIPP/Ag humidity, temperature, and illumination sensor was developed. Humidity, temperature, illumination dependent capacitive, and resistive properties of this sensor make it promising for use in a humidity, temperature, and lux multi-meters.  相似文献   
106.
Yttrium and cerium co-doped ZnO nanoparticles were synthesized by combustion route and characterized using X-ray diffraction(XRD),scanning electron microscopy(SEM),Brunauer-Emmett-Teller(BET),energy dispersive spectroscopy(EDS),X-ray photoelectron spectroscopy(XPS),UV-visible diffuse reflectance spectroscopy(UV-vis DRS),photoluminescence(PL)and electrochemical impedance spectroscopy(EIS)techniques.The introduction of yttrium ions has efficiently increased the relative percentage of Ce3+ions in ZnO.Yttrium and cerium co-doped ZnO shows efficient photo activity for hydrogen evolution(10.61 mmol/((g·h))higher than previously reported optimal value for rare earth codoped ZnO photocatalysts.This remarkably increased hydrogen evolution can be ascribed to the synergy between electronic anchoring effect of Y3+/Y2+and Ce4+/Ce3+redox couples.This report presents new idea for the synthesis of efficient photocatalyst using economical route and ion anchoring effect.The hydrogen evolution was also tested using Na2S and Na2SO3as electron donors under visible light illumination.The synthesized photocatalysts also exhibit high stability.  相似文献   
107.
108.
109.
110.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号