全文获取类型
收费全文 | 13744篇 |
免费 | 1283篇 |
国内免费 | 466篇 |
专业分类
电工技术 | 577篇 |
综合类 | 446篇 |
化学工业 | 2587篇 |
金属工艺 | 616篇 |
机械仪表 | 535篇 |
建筑科学 | 736篇 |
矿业工程 | 267篇 |
能源动力 | 458篇 |
轻工业 | 1123篇 |
水利工程 | 213篇 |
石油天然气 | 314篇 |
武器工业 | 64篇 |
无线电 | 2303篇 |
一般工业技术 | 2222篇 |
冶金工业 | 865篇 |
原子能技术 | 113篇 |
自动化技术 | 2054篇 |
出版年
2024年 | 43篇 |
2023年 | 229篇 |
2022年 | 440篇 |
2021年 | 671篇 |
2020年 | 512篇 |
2019年 | 455篇 |
2018年 | 518篇 |
2017年 | 508篇 |
2016年 | 629篇 |
2015年 | 545篇 |
2014年 | 684篇 |
2013年 | 1020篇 |
2012年 | 853篇 |
2011年 | 927篇 |
2010年 | 758篇 |
2009年 | 735篇 |
2008年 | 694篇 |
2007年 | 623篇 |
2006年 | 587篇 |
2005年 | 533篇 |
2004年 | 366篇 |
2003年 | 336篇 |
2002年 | 295篇 |
2001年 | 261篇 |
2000年 | 229篇 |
1999年 | 222篇 |
1998年 | 343篇 |
1997年 | 219篇 |
1996年 | 179篇 |
1995年 | 158篇 |
1994年 | 115篇 |
1993年 | 138篇 |
1992年 | 68篇 |
1991年 | 83篇 |
1990年 | 52篇 |
1989年 | 58篇 |
1988年 | 46篇 |
1987年 | 32篇 |
1986年 | 32篇 |
1985年 | 34篇 |
1984年 | 41篇 |
1983年 | 22篇 |
1982年 | 26篇 |
1981年 | 25篇 |
1980年 | 22篇 |
1979年 | 20篇 |
1978年 | 19篇 |
1977年 | 19篇 |
1974年 | 8篇 |
1973年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
Jianlong Zou Xikui Ma Chi K. Tse Dong Dai 《International Journal of Circuit Theory and Applications》2006,34(3):251-264
In this paper, we derive the discrete‐time model for the power‐factor‐correction (PFC) buck‐boost converter in terms of a stroboscopic switching map. Fast‐scale instability is analysed through a fold diagram, which exposes the periodicity of the operation as well as the locations of the critical phase angles of the line voltage at which instability begins to occur along a half‐line cycle. The asymmetrical locations of the critical phase angles along a half‐line cycle is explained in terms of ‘under‐developed’ bifurcation. Border collision bifurcations are observed and analysed in detail. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
62.
A new miniature bandpass filter, comprising three-conductor short-circuited spurline resonators of approximately a quarter-wavelength long, with a very wide bandwidth approaching multioctaves is reported for the first time. The chain matrix of the filter resonator is derived. The new filter has been developed using microstrip line with less than 1 dB insertion loss over a passband from 2 to 8 GHz. Reasonably good agreement between the measured and calculated results is observed 相似文献
63.
StructureandMagneticPropertiesofLaCo_(13-X)M_XIntermetallicCompoundsWUJianMin;LIFeng;TAILiChiandZHEMGQunStructureandMagneticP... 相似文献
64.
短毫米波和亚毫米波接收机的发展现状 总被引:1,自引:0,他引:1
本文概述了短毫米和亚毫米波接收机的发展现状,介绍了接收机的重要组成部件:混频器、振荡器和放大器的发展水平以及毫米波单片集成电路的现状,给出了接收机的最新性能指标。 相似文献
65.
Zheng Ming College of Biology Environment Engineering Jiangsu University Zhenjiang ChinaChen Chi Shanghai University 《机械工程学报(英文版)》2002,15(4):328-333
From basic equations of gas-liquid, solid-liquid, solid-gas two-phase flow, the calculating method on flow transients of two-phase flow is developed by means of characteristic method. As one example, a gas-liquid flow transient is calculated and it agrees well with the experimental result. It is shown that the method is satisfactory for engineering demand. 相似文献
66.
67.
Hayden J.D. Taft R.C. Kenkare P. Mazure C. Gunderson C. Nguyen B.-Y. Woo M. Lage C. Roman B.J. Radhakrishna S. Subrahmanyan R. Sitaram A.R. Pelley P. Lin J.-H. Kemp K. Kirsch H. 《Electron Devices, IEEE Transactions on》1994,41(12):2318-2325
An advanced, high-performance, quadruple well, quadruple polysilicon BiCMOS technology has been developed for fast 16 Mb SRAM's. A split word-line bitcell architecture, using four levels of polysilicon and two self-aligned contacts, achieves a cell area of 8.61 μm2 with conventional I-line lithography and 7.32 μm2 with I-line plus phase-shift or with deep UV lithography. The process features PELOX isolation to provide a 1.0 μm active pitch, MOSFET transistors designed for a 0.80 μm gate poly pitch, a double polysilicon bipolar transistor with aggressively scaled parasitics, and a thin-film polysilicon transistor to enhance bitcell stability. A quadruple-well structure improves soft error rate (SER) and allows simultaneous optimization of MOSFET and bipolar performance 相似文献
68.
Parasitic bipolar gain in fully depleted n-channel SOI MOSFET's 总被引:3,自引:0,他引:3
Ver Ploeg E.P. Nguyen C.T. Wong S.S. Plummer J.D. 《Electron Devices, IEEE Transactions on》1994,41(6):970-977
Fully depleted SOI MOSFET's include an inherent parasitic lateral bipolar structure with a floating base. We present here the first complete physically based explanation of the bipolar gain mechanism, and its dependence on bias and technological parameters. A simple, one-dimensional physical model, with no fitting parameters, is constructed, and is shown to agree well with simulations and measurements performed on a new type of SOI MOSFET structure. It is shown that parameters which affect the gain, such as SOI layer thickness, body doping concentration and gate and drain voltages, do so primarily by affecting the concentration of holes in the body region. Thus, current gain falls dramatically with increasing drain voltage due to the associated impact ionization driven increase in the hole concentration. Gummel plots of this parasitic bipolar indicate an apparent ideality factor of 0.5 for the hole current, due to the body hole concentration's dependence on drain voltage 相似文献
69.
Sanghera J.S. Nguyen V.Q. Pureza P.C. Kung F.H. Miklos R. Aggarwal I.D. 《Lightwave Technology, Journal of》1994,12(5):737-741
Improved purification and processing techniques have been utilized to fabricate Ge30As10Se30Te30 glass fibers with a minimum loss of O.11 dB/m at 6.6 μm. This is the lowest loss reported for any telluride glass fiber in the infrared region. Furthermore, the fibers exhibit less than 1 dB/m loss between 5.25 and 9.5 μm 相似文献
70.