全文获取类型
收费全文 | 1349篇 |
免费 | 81篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 19篇 |
综合类 | 7篇 |
化学工业 | 247篇 |
金属工艺 | 30篇 |
机械仪表 | 19篇 |
建筑科学 | 38篇 |
矿业工程 | 2篇 |
能源动力 | 30篇 |
轻工业 | 162篇 |
水利工程 | 4篇 |
石油天然气 | 7篇 |
无线电 | 170篇 |
一般工业技术 | 240篇 |
冶金工业 | 229篇 |
原子能技术 | 7篇 |
自动化技术 | 221篇 |
出版年
2023年 | 15篇 |
2022年 | 24篇 |
2021年 | 57篇 |
2020年 | 46篇 |
2019年 | 57篇 |
2018年 | 50篇 |
2017年 | 40篇 |
2016年 | 70篇 |
2015年 | 39篇 |
2014年 | 57篇 |
2013年 | 97篇 |
2012年 | 73篇 |
2011年 | 68篇 |
2010年 | 38篇 |
2009年 | 45篇 |
2008年 | 55篇 |
2007年 | 35篇 |
2006年 | 35篇 |
2005年 | 40篇 |
2004年 | 26篇 |
2003年 | 27篇 |
2002年 | 25篇 |
2001年 | 19篇 |
2000年 | 11篇 |
1999年 | 22篇 |
1998年 | 81篇 |
1997年 | 46篇 |
1996年 | 29篇 |
1995年 | 22篇 |
1994年 | 20篇 |
1993年 | 16篇 |
1992年 | 7篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 11篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1977年 | 11篇 |
1976年 | 9篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1973年 | 6篇 |
1968年 | 4篇 |
排序方式: 共有1432条查询结果,搜索用时 450 毫秒
71.
72.
73.
W. Zychlinski G. Bach G. Zimmermann V. G. Sokolovskaja L. V. Shevelkova L. E. Guselnikov 《Advanced Synthesis \u0026amp; Catalysis》1987,329(5):824-832
Thermal Reaction of Mono-n-alkyl-benzenes The pyrolysis of ethyl-( 1 ), n-propyl-( 2 ), n-hexyl-( 3 ) and n-octylbenzene ( 4 ) has been studied under conditions of steam cracking (600 to 800°C) in a laboratory scale tubular reactor. The overall activation energies determined for ( 1 ) to ( 4 ) were found to be nearly identical (221 to 227 kJ · mol−1) obviously caused by similar initial steps. The main liquid product observed was styren accompanied by ω-phenyl-1-alkenes and α-olefins. Benzene is an important side product of 1 . It might be formed mainly by a hydrogen assisted dealkylation via a cyclohexadienyl type radical as reactive intermediate. 相似文献
74.
Ho Sn Lam G. Zimmermann G. Anders G. Bach D. Rennecke W. Zychlinski 《Advanced Synthesis \u0026amp; Catalysis》1985,327(5):759-766
Studies on Thermal Conversion of Phenyleyclopentane, -hexane, -heptane, and -octane in the Gas Phase The title compounds were pyrolyzed from 700 to 780°C in a metallic laboratory tubular reactor in the presence of steam. The reaction products were analyzed by gas chromatography and by a combination of gas chromatography and mass spectrometry. From the phenylcyclanes tested, more than 65 hydrocarbons could be detected in the liquids, besides gaseous reaction products. In most cases unambiguous structures could be derived by using different analytical methods. As typical initial-step products phenylcyclenes, ω-phenyl-1-alkenes and 1-phenyl-1-alkenes are formed by dehydrogenation and isomerization of the title compounds. The detection of phenylalkenes corresponds well with the isomerization of unsubstituted cyclanes to the corresponding α-olefines described in former papers. 相似文献
75.
Manfred Schulz Barbara Bach Michael Reinhardt 《Advanced Synthesis \u0026amp; Catalysis》1984,326(4):579-587
Reactions of the 2,6-Di-tert.-butyl-4-(N-tert.-butylnitrono)-phenoxyl Radical The title compound, a phenoxyl radical containing a nitrono group, reacts with alcohols and tert.-butylhydroperoxide yielding phenol and products of secondary radical solvent reactions. The reactions with lead tetraacetate, tert.-butoxy and 2-cyanoisopropyl radicals give high yields of cyclohexadienone adducts ( 6, 7 and 10 ) containing unchanged nitrono function. The reaction with dibenzoylperoxide, however, leads to the modification of the nitrono group yielding the N-benzoyloxycarboxamide ( 8 ). In the acidic decomposition of the tert.-butoxy radical adduct we suggest a nitrenium ion ( 16 ) as an intermediate. 相似文献
76.
V. Quintard B. Parmentier T. Phan D. Lewis S. Dilhaire W. Claeys 《Quality and Reliability Engineering International》1996,12(6):447-452
We present the results of a non-destructive measuring method allowing us to characterize the evolution of solder joints during thermal cycling ageing tests. The method uses a high resolution optical probe to detect selectively pure Joule and Peltier thermal responses of the solder joint subject to a given current pulse. The results show the Peltier and Joule responses to be good indicators for the evaluation of the age and the degradation of solder joints. 相似文献
77.
Frances I. Hurwitz Richard B. Rogers Haiquan Guo Anita Garg Nathaniel S. Olson David Phan Jessica L. Cashman 《Journal of the American Ceramic Society》2020,103(12):6700-6711
High-porosity yttria- and ytterbia-stabilized zirconia aerogels offer the potential of extremely low thermal conductivity materials for high-temperature applications. Yttria- and ytterbia-doped zirconia aerogels were synthesized using a sol-gel approach over the dopant range of 0-20 atomic percent. Surface area, pore volume, and morphology of the as-dried aerogels and materials thermally exposed for short periods of time to temperatures up to 1200°C were characterized by nitrogen physisorption, scanning and transmission electron microscopy, and X-ray diffraction. The aerogels as supercritically dried all were X-ray amorphous. At a 5% dopant level, a tetragonal structure with a smaller monoclinic phase developed on thermal exposure. Mixed tetragonal and cubic phases or predominantly cubic materials were observed at higher dopant levels, depending on the dopant level, temperature and exposure time. The formation of crystalline phases was accompanied by loss of surface area and pore volume, although some mesoporous structure was maintained on short-term exposure to 1000°C. Incorporation of the smaller Yb atom into the lattice structure resulted in smaller lattice dimensions on crystallization than was seen with Y doping and favored a more highly equiaxed structure. Aerogels synthesized with 15% Y maintained the smallest particle size without evidence of sintering at 1100°C. Largest shrinkage and loss of pore volume occurred on crystallization from the amorphous phase, with further loss of pores at temperatures above 1000°C attributable to changes in lattice parameters. 相似文献
78.
Anastasia A. Ivanova Chi Phan Ahmed Barifcani Stefan Iglauer Alexey N. Cheremisin 《Journal of surfactants and detergents》2020,23(2):327-338
Surfactant flooding has widely been used as one of the chemically enhanced oil recovery (EOR) techniques. Surfactants majorly influence the interfacial tension, γ, between oil and brine phase and control capillary number and relative permeability behavior and, thus, influence ultimate recovery. Additives, such as nanoparticles, are known to affect surfactant properties and are regarded as promising EOR agents. However, their detailed interactions with surfactants are not well understood. Thus, in this work, we examined the influence of silica nanoparticles on the ability of surfactants to lower γ and to increase viscosity at various temperatures and salinities. Results show that the presence of nanoparticles decreased γ between n-decane and various surfactant formulations by up to 20%. It was found that γ of nanoparticles–surfactant solutions passed through a minimum at 35 °C when salt was added. Furthermore, the viscosity of cationic surfactant solutions increased at specific salt (1.5 wt.%) and nanoparticle (0.05 wt.%) concentrations. Results illustrate that selected nanoparticles–surfactant formulations appear very promising for EOR as they can lower brine/n-decane interfacial tension and act as viscosity modifiers of the injected fluids. 相似文献
79.
Umberto De Rossi Johannes Moll Monika Spieles Günther Bach Siegfried Dhne Jrg Kriwanek Maria Lisk 《Advanced Synthesis \u0026amp; Catalysis》1995,337(1):203-208
Cyanine dyes ( 1a–d ) with the 5,5′,6,6′-tetrachloro-1,1′-dialkyl-3,3′-di-(3-carboxypropyl)-benzimidocarbocyanine chromophore differing only in the chain length of their alkyl groups in 1,1′-position have been synthesized, spectroscopically characterized, and compared with 5,5′6,6′-tetrachloro-1,1′-diethyl-3,3′-di-(4-sulfobutyl)-benzimidocarbocyanine( TDBC ). In aqueous solution the dyes form J-aggregates which, depending on the alkyl group chain length, exhibit J-bands differing in spectral positions, bandwidth, and in the number of peaks. 相似文献
80.
Toan Dinh Van Dau Canh‐Dung Tran Tuan‐Khoa Nguyen Hoang‐Phuong Phan Nam‐Trung Nguyen Dzung Viet Dao 《大分子材料与工程》2019,304(6)
Flexible multifunctional electronic devices are of high interest for a wide range of applications including thermal therapy and respiratory devices in medical treatment, safety equipment, and structural health monitoring systems. This paper reports a scalable and efficient strategy of manufacturing a polyacrylonitrile‐carbon nanotube‐polyacrylonitrile (PAN‐CNT‐PAN) robust flexible platform for multifunctional electronic devices including flexible heaters, temperature sensors, and flexible thermal flow sensors. The key advantages of this platform include low cost, porosity, mechanical robustness, and electrical stability under mechanical bending, enabling the development of fast‐response flexible heaters with a response time of ≈1.5 s and relaxation time of ≈1.7 s. The temperature‐sensing functionality is also investigated with a range of temperature coefficient of resistances from ?650 to ?900 ppm K?1. A flexible hot‐film sensing concept is successfully demonstrated using PAN‐CNT‐PAN with a high sensitivity of 340 mV (m s?1)?1. The sensitivity enhancement of 50% W?1 is also observed with increasing supply power. The low cost, porosity, versatile, and robust properties of the proposed platform will enable the development of multifunctional electronic devices for numerous applications such as flexible thermal management, temperature stabilization in industrial processing, temperature sensing, and flexible/wearable devices for human healthcare applications. 相似文献