全文获取类型
收费全文 | 959篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 13篇 |
综合类 | 3篇 |
化学工业 | 252篇 |
金属工艺 | 29篇 |
机械仪表 | 15篇 |
建筑科学 | 32篇 |
能源动力 | 33篇 |
轻工业 | 72篇 |
水利工程 | 5篇 |
石油天然气 | 1篇 |
无线电 | 133篇 |
一般工业技术 | 182篇 |
冶金工业 | 34篇 |
原子能技术 | 16篇 |
自动化技术 | 142篇 |
出版年
2023年 | 5篇 |
2022年 | 7篇 |
2021年 | 11篇 |
2020年 | 8篇 |
2019年 | 15篇 |
2018年 | 10篇 |
2017年 | 10篇 |
2016年 | 8篇 |
2015年 | 5篇 |
2014年 | 27篇 |
2013年 | 55篇 |
2012年 | 47篇 |
2011年 | 52篇 |
2010年 | 50篇 |
2009年 | 53篇 |
2008年 | 50篇 |
2007年 | 43篇 |
2006年 | 45篇 |
2005年 | 43篇 |
2004年 | 25篇 |
2003年 | 31篇 |
2002年 | 34篇 |
2001年 | 12篇 |
2000年 | 12篇 |
1999年 | 23篇 |
1998年 | 20篇 |
1997年 | 16篇 |
1996年 | 18篇 |
1995年 | 20篇 |
1994年 | 17篇 |
1993年 | 7篇 |
1992年 | 15篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1983年 | 8篇 |
1982年 | 11篇 |
1981年 | 14篇 |
1980年 | 14篇 |
1979年 | 6篇 |
1977年 | 4篇 |
1976年 | 7篇 |
1975年 | 6篇 |
1974年 | 7篇 |
1971年 | 5篇 |
排序方式: 共有962条查询结果,搜索用时 7 毫秒
91.
In this article, two topologies of L-C parallel active resonators are presented. These circuits are realized in MMIC technology, using three transistors which could be MESFET, hemt or HBT. The survey of these resonators shows the possibility, by controling the values of a resistor and/or a capacitor, on the one hand, to tune the resonance frequency of these circuits, and on the other hand, to cancel out their losses so as to obtain negative conductance. Compact, lossless and narrow-band filters are then implemented using previous active resonators. To date, the use of mesfet technology has reduced the synthesis of such active filters in S-band and at X-band low frequencies. Now, however, hemt and HBT technologies allow the extension of their implementation to the whole X-band. This survey is illustrated by the simulated response of a 10 GHz filter with a 500 MHz 3 dB bandwidth. The mmic technology is a 0.2 μm hemt one. The simulated performances of this filter achieve a mean transmission gain of 0. 5 dB, with a reflection loss higher than 10 dB at 10 GHz, 相似文献
92.
93.
Thomas J. Ellis Jean-Pierre Raskin 《Journal of Infrared, Millimeter and Terahertz Waves》2002,23(9):1357-1369
A broadband vertical transition from coplanar waveguide (CPW)-to-microstrip modes is presented. The transition has a double resonance and can be tuned for very wide-band operation. The CPW-to-microstrip modes coupling technique is useful for the vertical integration of multi-layer millimeter-wave circuits, packaging and antenna feeding networks. A vertical transition has been fabricated on 100 μm silicon substrate for operation at W-band frequencies and shows less than 0.3 dB of insertion loss and better than 12 dB of return loss from 75 to 110 GHz. A 94 GHz CPW-fed microstrip antenna showing a 10-dB bandwidth of about 30 % has been built using the same transition technique. 相似文献
94.
95.
Equilibrium stress-strain relationships in uniaxial extension for high cis-1,4-polyisoprene (Shell IR 307) networks were obtained by extrapolation of relaxation measurements to infinite time through a BKZ constitutive equation. Three series of networks were investigated, each series being characterized by its polymer precursor molecular weight. Influence of crosslinking density was studied through varying amounts of dicumyl peroxide as crosslinking agent. These results were used to test Flory and Erman's recent molecular elasticity theory of imperfect networks with constraints on junctions. It was shown that this later theory treating entanglements as restrictions on junction fluctuations could be reasonably used to characterize network topology. A universal value of 0.50 for the interpenetration parameter I is confirmed and an interpretation of parameter ζ in terms of network inhomogeneity is tentatively given. 相似文献
96.
The influence of γ-butyrolactone (γ-BL), used as solvent of BF3-amine complexes, on the polymerization of monoepoxides was studied. Different intermediate reaction products of PGE initiated by BF3-4-methoxyaniline (BF3-4MA) previously solubilized in γ-BL (55% by weight), were separated and analyzed by 1H-NMR. It is shown that there is the opening of both epoxy and γ-BL. The latter does not homopolymerize, but copolymerizes well with epoxy groups. The use of a large quantity of γ-BL leads to a decreasing molar mass of the formed polymer. The kinetic study allowed to propose the mechanism of the cationic polymerization of epoxy initiated by BF3-amine complex in the presence of γ-BL. © 1994 John Wiley & Sons, Inc. 相似文献
97.
James?M.?Ma Samad?A.?Firdosy Richard?B.?Kaner Jean-Pierre?Fleurial Vilupanur?A.?RaviEmail author 《Journal of Materials Science》2014,49(3):1150-1156
Lanthanum telluride (La3?x Te4) is a state-of-the-art n-type high temperature thermoelectric material that behaves as a weak and brittle ceramic. Vickers microindentation hardness testing was explored as a rapid analysis technique to characterize the mechanical properties of this material. An indentation size effect was observed with hardness values ranging from 439 ± 31 kgf/mm2 (0.01 kgf/10 s contact time) to 335 ± 6 kgf/mm2 (0.5 kgf/10 s contact time). The Vickers indentation fracture toughness, K VIF, based on measurements of crack lengths emanating from the corners of the Vickers indents was 0.70 ± 0.06 MPa m1/2. 相似文献
98.
99.
Chi-Woo Lee Dimitri Lederer Aryan Afzalian Ran Yan Nima Dehdashti Weize Xiong Jean-Pierre Colinge 《Solid-state electronics》2008,52(11):1815-1820
The performances of accumulation-mode and inversion-mode multigate FETs are compared. The influence of gate underlap on the electrical properties is analyzed. Both simulation results and experimental data show that in a device with gate underlap, accumulation-mode devices have a higher current drive, lower source and drain resistance and less process variability than inversion-mode FETs. 相似文献
100.
Jean-Pierre Delahaye 《电信纪事》1996,51(1-2):19-26
This paper presents an overview of the implementation of a difference-set cyclic code (1057,813,34). It is easy to achieve coding and decoding circuits. The decoding lays on the analysis of the composite remainder Rc (x) and the use of a decoding matrix of 33 Boolean equations. The error-correcting algorithm has been improved, so the difference-set cyclic code (1057,813,34) can correct up to 26 random errors instead of the 16 previous random errors found by the theory. Moreover, 3 decoding algorithms have been simulated and allow the comparison of their respective efficiency. The hardware achievement is quite easy because the necessary logical elements such as shift delay registers, positive-and gates, positive-or gates, positive-exclusive-or gates exist as a set of libraries. 相似文献