全文获取类型
收费全文 | 301998篇 |
免费 | 2288篇 |
国内免费 | 919篇 |
专业分类
电工技术 | 5107篇 |
综合类 | 136篇 |
化学工业 | 48010篇 |
金属工艺 | 17100篇 |
机械仪表 | 11579篇 |
建筑科学 | 5519篇 |
矿业工程 | 4030篇 |
能源动力 | 5525篇 |
轻工业 | 15354篇 |
水利工程 | 4678篇 |
石油天然气 | 14035篇 |
武器工业 | 67篇 |
无线电 | 25658篇 |
一般工业技术 | 73240篇 |
冶金工业 | 41793篇 |
原子能技术 | 12645篇 |
自动化技术 | 20729篇 |
出版年
2021年 | 3276篇 |
2019年 | 3165篇 |
2018年 | 6185篇 |
2017年 | 6498篇 |
2016年 | 6888篇 |
2015年 | 3595篇 |
2014年 | 6194篇 |
2013年 | 12609篇 |
2012年 | 8810篇 |
2011年 | 10780篇 |
2010年 | 8865篇 |
2009年 | 9877篇 |
2008年 | 9955篇 |
2007年 | 9642篇 |
2006年 | 7911篇 |
2005年 | 6917篇 |
2004年 | 6794篇 |
2003年 | 6640篇 |
2002年 | 6391篇 |
2001年 | 6222篇 |
2000年 | 6131篇 |
1999年 | 5505篇 |
1998年 | 10456篇 |
1997年 | 8089篇 |
1996年 | 6073篇 |
1995年 | 4963篇 |
1994年 | 4546篇 |
1993年 | 4725篇 |
1992年 | 3954篇 |
1991年 | 4147篇 |
1990年 | 4279篇 |
1989年 | 4134篇 |
1988年 | 3960篇 |
1987年 | 3866篇 |
1986年 | 3780篇 |
1985年 | 3989篇 |
1984年 | 3809篇 |
1983年 | 3695篇 |
1982年 | 3483篇 |
1981年 | 3551篇 |
1980年 | 3542篇 |
1979年 | 3727篇 |
1978年 | 3907篇 |
1977年 | 4025篇 |
1976年 | 4620篇 |
1975年 | 3601篇 |
1974年 | 3657篇 |
1973年 | 3715篇 |
1972年 | 3311篇 |
1971年 | 3057篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
A. V. Butko A. A. Klimov S. A. Nikitov Yu. A. Filimonov 《Journal of Communications Technology and Electronics》2006,51(8):944-947
The magneto-optical Kerr effect for red (628 nm) and green (532 nm) light is used to study magnetization processes in 2D magnonic crystals obtained by etching pits with the diameter D ≈ 32 μm to a depth of t ≤ 2 μm in a 16.1-μm-thick film of yttrium iron garnet (YIG). Hysteresis loops obtained in the case of the inplane crystal magnetization at 628 nm are characterized by lower saturation fields H s and higher remanent magnetizations than those obtained at 532 nm, a result that is attributed to different absorption coefficients of the YIG film at these wavelengths. This difference between the magnetization curves reflects the fact that the magnonic-crystal surface probed with the green light makes a greater contribution to the magneto-optical Kerr effect. Therefore, the green light is more sensitive to the demagnetizing fields, which govern magnetization processes in the magnonic crystals. 相似文献
42.
The electrical properties and microstructure of (Ba,Y)TiO3 PTCR ceramics were studied. The results indicate that the Mn ions increase the intergranular barrier height and produce a high-resistance layer on the grain surface. The temperature-dependent resistances of the grain bulk, surface layer, and grain boundaries, the temperature coefficient of resistance, and the magnitude of the varistor effect were assessed as a function of Mn content. 相似文献
43.
Kilchytska V. Neve A. Vancaillie L. Levacq D. Adriaensen S. van Meer H. De Meyer K. Raynaud C. Dehan M. Raskin J.-P. Flandre D. 《Electron Devices, IEEE Transactions on》2003,50(3):577-588
This work presents a systematic comparative study of the influence of various process options on the analog and RF properties of fully depleted (FD) silicon-on-insulator (SOI), partially depleted (PD) SOI, and bulk MOSFET's with gate lengths down to 0.08 /spl mu/m. We introduce the transconductance-over-drain current ratio and Early voltage as key figures of merits for the analog MOS performance and the gain and the transition and maximum frequencies for RF performances and link them to device engineering. Specifically, we investigate the effects of HALO implantation in FD, PD, and bulk devices, of film thickness in FD, of substrate doping in SOI, and of nonstandard channel engineering (i.e., asymmetric Graded-channel MOSFETs and gate-body contacted DTMOS). 相似文献
44.
Static energy reduction techniques for microprocessor caches 总被引:1,自引:0,他引:1
Hanson H. Hrishikesh M.S. Agarwal V. Keckler S.W. Burger D. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2003,11(3):303-313
Microprocessor performance has been improved by increasing the capacity of on-chip caches. However, the performance gain comes at the price of static energy consumption due to subthreshold leakage current in cache memory arrays. This paper compares three techniques for reducing static energy consumption in on-chip level-1 and level-2 caches. One technique employs low-leakage transistors in the memory cell. Another technique, power supply switching, can be used to turn off memory cells and discard their contents. A third alternative is dynamic threshold modulation, which places memory cells in a standby state that preserves cell contents. In our experiments, we explore the energy and performance tradeoffs of these techniques. We also investigate the sensitivity of microprocessor performance and energy consumption to additional cache latency caused by leakage-reduction techniques. 相似文献
45.
T. Choi J.‐H. Jang C.K. Ullal M.C. LeMieux V.V. Tsukruk E.L. Thomas 《Advanced functional materials》2006,16(10)
The probing of the micromechanical properties within a two‐dimensional polymer structure with sixfold symmetry fabricated via interference lithography reveals a nonuniform spatial distribution in the elastic modulus “imprinted” with an interference pattern in work reported by Tsukruk, Thomas, and co‐workers on p. 1324. The image prepared by M. Lemieux and T. Gorishnyy shows how the interference pattern is formed by three laser beams and is transferred to the solid polymer structure. The elastic and plastic properties within a two‐dimensional polymer (SU8) structure with sixfold symmetry fabricated via interference lithography are presented. There is a nonuniform spatial distribution in the elastic modulus, with a higher elastic modulus obtained for nodes (brightest regions in the laser interference pattern) and a lower elastic modulus for beams (darkest regions in the laser interference pattern) of the photopatterned films. We suggest that such a nonuniformity and unusual plastic behavior are related to the variable material properties “imprinted” by the interference pattern. 相似文献
46.
S. V. Doronin 《Chemical and Petroleum Engineering》2006,42(7-8):461-464
Current features are considered in the calculation of carrying capacities for constructions in engineering plant (EP). Methods
and algorithms are described for EP calculations with comprehensive incorporation of the effects from technological and working
defects on the behavior of structures under standard and emergency conditions.
__________
Translated from Khimicheskoe i Neftegazovoe Mashinostroenie, No. 8, pp. 38–40, August, 2006. 相似文献
47.
du Burck F. Lopez O. El Basri A. 《IEEE transactions on instrumentation and measurement》2003,52(2):288-291
We have developed a narrow-band controller in the MHz range, based on a field-programmable gate array. It is used to control the probe beam intensity in frequency-modulated spectroscopy experiments with an acoustooptic modulator. The residual amplitude modulation at the modulation frequency (2.5 MHz) is reduced by 50 dB. The first-harmonic detection of the signals is operated in saturation spectroscopy of I/sub 2/ at 514.5 nm and 501.7 nm. A reduction of the background noise and a large increase in the signal-to-noise ratio are obtained. 相似文献
48.
V. N. Pavlechko 《Journal of Engineering Physics and Thermophysics》2004,77(1):115-120
Relations for determining a motive force in a complex model of mass transfer as applied to concurrent, countercurrent, and cross motion of the vapor and liquid phases have been introduced. These forces have been compared for different forms of organization of the flow, and their comparison with similar quantities from the known Murphree and Hausen models is presented. 相似文献
49.
50.
D. Vignolles D. Smirnov G. Rikken B. Raquet H. Rakoto C. Proust M. Nardone J. Léotin F. Lecouturier M. Goiran O. Drachenko J. M. Broto L. Brossard A. Audouard 《Journal of Low Temperature Physics》2003,133(1-2):97-120
An overview over past and present activities and future developments at the Toulouse pulsed magnetic field facility is given, both as far as technical developments of the infrastructure, as well as low temperature physics performed at the LNCMP are concerned. 相似文献