全文获取类型
收费全文 | 9229篇 |
免费 | 1299篇 |
国内免费 | 577篇 |
专业分类
电工技术 | 2378篇 |
综合类 | 664篇 |
化学工业 | 1271篇 |
金属工艺 | 185篇 |
机械仪表 | 623篇 |
建筑科学 | 225篇 |
矿业工程 | 122篇 |
能源动力 | 221篇 |
轻工业 | 741篇 |
水利工程 | 91篇 |
石油天然气 | 387篇 |
武器工业 | 48篇 |
无线电 | 1236篇 |
一般工业技术 | 1642篇 |
冶金工业 | 168篇 |
原子能技术 | 290篇 |
自动化技术 | 813篇 |
出版年
2024年 | 48篇 |
2023年 | 203篇 |
2022年 | 299篇 |
2021年 | 342篇 |
2020年 | 379篇 |
2019年 | 322篇 |
2018年 | 339篇 |
2017年 | 394篇 |
2016年 | 452篇 |
2015年 | 436篇 |
2014年 | 626篇 |
2013年 | 683篇 |
2012年 | 677篇 |
2011年 | 739篇 |
2010年 | 460篇 |
2009年 | 523篇 |
2008年 | 501篇 |
2007年 | 522篇 |
2006年 | 479篇 |
2005年 | 361篇 |
2004年 | 368篇 |
2003年 | 310篇 |
2002年 | 215篇 |
2001年 | 188篇 |
2000年 | 203篇 |
1999年 | 140篇 |
1998年 | 117篇 |
1997年 | 131篇 |
1996年 | 118篇 |
1995年 | 88篇 |
1994年 | 74篇 |
1993年 | 55篇 |
1992年 | 45篇 |
1991年 | 60篇 |
1990年 | 34篇 |
1989年 | 27篇 |
1988年 | 17篇 |
1987年 | 17篇 |
1986年 | 14篇 |
1985年 | 23篇 |
1984年 | 20篇 |
1983年 | 14篇 |
1982年 | 27篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
22.
References: 《中国炼油与石油化工》2007,(3):35-42
The proton nuclear magnetic resonance spectroscopy (1H-NMR), the synchronous fluorescence spectrometry (SFS) and the ruthenium ions catalyzed oxidation (RICO) method were used to determine the chemical structure of polyaromatic nucleus in Oman residue fractions. The results of 1H-NMR analyses showed that the average numbers of aromatic rings in the aromatics, resins and asphaltenes units were 3.2, 5.6 and 8.2, respectively. SFS was used to investigate the distribution of aromatic rings in residue fractions, the main distribution range of aromatic rings in aromatics, resins and asphaltenes were 3 4 rings, 3--5 rings and more than 5 rings, respectively. The aromatic network in residue fractions was oxidized to produce numerous carboxylic acids. The types and content of benzenepolycarboxylic acids, such as phthalic acid, benzenetricarboxylic acids, benzenetetracarboxylic acids, benzenepentacarboxylic acid and benzenehexacarboxylic acid disclosed the condensed types of aromatic nuclei in the core. The biphenyl fraction (BIPH), the cata-condensed fraction (CATA), the peri-condensed fraction (PERI) and the condensed index (BCI) were calculated based on the benzenepolycarboxylic acids formed. The results implied that there was less biphenyl type structures in all residue fractions. The aromatics fraction was almost composed of the cata-condensed type system, and the asphaltenes fraction was wholly composed of the peri-condensed type system, while in the resins fraction co-existed the two types, herein the peri-con- densed type was predominant over the cata-condensed type. Based on the analytical results obtained in the study, the components --aromatics, resins and asphaltenes -- were given the likely structural models. 相似文献
23.
Koji Yamada Noboru Miura Chihiro Hamaguchi Norihiko Kamata 《Solid-state electronics》1989,32(12):1113-1117
Hot carrier magnetophonon resonances of n-type Si, short channel InP and p-type InSb were investigated in pulsed high magnetic fields up to 40 T. Using a recently developed high resolution technique in pulsed high fields, many new features of the hot carrier-phonon interactions in high magnetic fields were found. 相似文献
24.
L. V. El’nikova 《Journal of Superconductivity and Novel Magnetism》2007,20(2):197-199
We describe the lyotropic liquid crystalline phase transitions in the lipid mixture dipalmitoil-PC/dilauroy-PC/cholesterol
by 3D spin-1 lattice model. The formation of nanoscale domains with the characteristic size about 300 nm was studied in experiments
on confocal fluorescence microscopy (CFM) (G. V. Feigenson and J. T. Buboltz, Biophys. J.
80, 2775 (2001)). The structure parameters of the lamellar vesicle in dipalmitoil-PC-rich phase, corresponding to these regions,
are verified by numerical Monte Carlo simulations on the lattice. We point its superconductivity analogy properties at the
region of phase stability for composition-dependent nanoscopic region. 相似文献
25.
钕电解阳极过电位的测定 总被引:2,自引:0,他引:2
用慢扫描示波法测定了钕电解的阳极过电位 .考察了温度、阳极电流密度、Nd2 O3添加量、电解质组成等因素对阳极过电位的影响 ,探讨了降低阳极过电位的可能途径 .结果表明 ,阳极过电位随阳极电流密度的增加而增大 ,随温度的升高而减小 ,一定范围内 ,阳极过电位与阳极电流密度的对数呈线性关系 ,满足塔菲尔方程 ;电解质中LiF和Nd2 O3浓度增加 ,阳极过电位降低 ;适当控制阳极电流密度、升高温度、增加电解质中LiF和Nd2 O3的浓度并尽可能减小极间距 ,均有利于降低阳极过电位 相似文献
26.
V.J. Logeeswaran F.E.H. Tay M.L. Chan F.S. Chau Y.C. Liang 《Analog Integrated Circuits and Signal Processing》2003,37(1):17-33
In this paper, the response to the first harmonic component (2f) of the electrostatic force in single terminal driven electrostatic comb-drive and parallel-plate drive was used as a signal to extract device parameters, namely, the Q-factor and resonant frequency instead of the fundamental (1f) resonance response. It is shown that the difficulty in motional measurement due to electrical cross-talk (parasitics) using 1f measurement can be overcome with a higher signal-to-noise ratio of the 2f signal. Both atmospheric (low-Q) and reduced pressure environment were investigated using off-chip electronics and lock-in amplifier. The measurements were done on the electrostatic comb-drive and capacitive parallel plate sensing plates that form the two core modules of a yaw rate sensor (dual-axis resonator). The effects of AC and DC bias voltages on the measured response have been investigated. Experimental amplitude and phase response data have been analysed using the Lorentzian curve-fit, Resonance Curve Area (RCA) method, the half-power bandwidth method (3 dB) and the Nyquist plot for data fitting and determination of the Q-factor and resonance frequency. 相似文献
27.
28.
29.
Bruce C. Bunker R. James Kirkpatrick Richard K. Brow Gary L. Turner Carolyn Nelson 《Journal of the American Ceramic Society》1991,74(6):1430-1438
30.
活塞式压缩机吸排气管道的振动与控制 总被引:1,自引:0,他引:1
阐述了活塞式压缩机吸、排气管道强烈振动的危害,分析了产生共振的原因,介绍了现场消减管道振动的有效措施。 相似文献