全文获取类型
收费全文 | 430717篇 |
免费 | 3954篇 |
国内免费 | 983篇 |
专业分类
电工技术 | 7960篇 |
综合类 | 404篇 |
化学工业 | 63815篇 |
金属工艺 | 21370篇 |
机械仪表 | 15047篇 |
建筑科学 | 8196篇 |
矿业工程 | 4333篇 |
能源动力 | 8463篇 |
轻工业 | 23486篇 |
水利工程 | 5632篇 |
石油天然气 | 14564篇 |
武器工业 | 51篇 |
无线电 | 46031篇 |
一般工业技术 | 96149篇 |
冶金工业 | 75398篇 |
原子能技术 | 13875篇 |
自动化技术 | 30880篇 |
出版年
2021年 | 3983篇 |
2019年 | 3895篇 |
2018年 | 7254篇 |
2017年 | 7443篇 |
2016年 | 7860篇 |
2015年 | 4461篇 |
2014年 | 7683篇 |
2013年 | 17535篇 |
2012年 | 11361篇 |
2011年 | 14544篇 |
2010年 | 11823篇 |
2009年 | 13338篇 |
2008年 | 13854篇 |
2007年 | 13499篇 |
2006年 | 11574篇 |
2005年 | 10501篇 |
2004年 | 10359篇 |
2003年 | 10015篇 |
2002年 | 9714篇 |
2001年 | 9857篇 |
2000年 | 9516篇 |
1999年 | 9418篇 |
1998年 | 22402篇 |
1997年 | 15790篇 |
1996年 | 12095篇 |
1995年 | 9231篇 |
1994年 | 8249篇 |
1993年 | 8398篇 |
1992年 | 6371篇 |
1991年 | 6308篇 |
1990年 | 6395篇 |
1989年 | 6107篇 |
1988年 | 5747篇 |
1987年 | 5216篇 |
1986年 | 5182篇 |
1985年 | 5660篇 |
1984年 | 5304篇 |
1983年 | 4967篇 |
1982年 | 4659篇 |
1981年 | 4831篇 |
1980年 | 4613篇 |
1979年 | 4709篇 |
1978年 | 4897篇 |
1977年 | 5202篇 |
1976年 | 6395篇 |
1975年 | 4386篇 |
1974年 | 4411篇 |
1973年 | 4418篇 |
1972年 | 3861篇 |
1971年 | 3505篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
Crosstalk between microstrip transmission lines 总被引:1,自引:0,他引:1
Hill D.A. Cavcey K.H. Johnk R.T. 《Electromagnetic Compatibility, IEEE Transactions on》1994,36(4):314-321
Methods for prediction of crosstalk between microstrip transmission lines are reviewed and simplified for the weak-coupling case. Classical coupled transmission line theory is used for uniform lines, and potential and induced EMF methods are used for crosstalk between nonuniform lines. It is shown that the potential method is equivalent to classical coupled transmission line theory for the case of uniform lines. An experiment was performed for uniform coupled microstrip lines for frequencies from 50 MHz to 5 GHz, and good agreement between theory and measurement was obtained for both near- and far-end crosstalk 相似文献
112.
Varani L. Reggiani L. Kuhn T. Gonzalez T. Pardo D. 《Electron Devices, IEEE Transactions on》1994,41(11):1916-1925
We present a microscopic interpretation of electronic noise in semiconductor materials and two-terminal devices. The theory is based on Monte Carlo simulations of the carrier motion self-consistently coupled with a Poisson solver. Current and voltage noise operations are applied and their respective representations discussed. As application we consider the cases of homogeneous materials, resistors, n+nn + structures, and Schottky-barrier diodes. Phenomena associated with coupling between fluctuations in carrier velocity and self-consistent electric field are quantitatively investigated for the first time. At increasing applied fields hot-carrier effects are found to be of relevant importance in all the cases considered here. As a general result, noise spectroscopy is found to be a source of valuable information to investigate and characterize transport properties of semiconductor materials and devices 相似文献
113.
114.
115.
S V Bhat 《Bulletin of Materials Science》1994,17(7):1271-1285
When examined using continuous wave electron paramagnetic resonance and nuclear magnetic resonance spectrometers, the highT
c superconductors give rise to intense, low field, ‘non-resonant’ absorption signals in the superconducting state. This phenomenon
can be used as a highly sensitive, contactless technique for the detection and characterization of superconductivity even
in samples containing only minute amounts of the superconducting phase. Further, it can also be applied to the determination
of material parameters of interest such asJ
c andH
c2 in addition to being a powerful way of distinguishing between weak-link superconductivity and bulk superconductivity. The
details of these aspects are discussed. 相似文献
116.
An instrument is proposed for continuously tracking the Sun and measuring its height by the use of a laser gyrometer as measuring
converter. The accuracy in photoelectric sighting on the Sun is improved by greatly reducing the light fluxes to be compared
by screening out the central part of the Sun's image in the focal plane.
Translated from Izmeritel'naya Tekhnika, No. 3, pp. 7–9, March, 1994. 相似文献
117.
A method is given for calculating the monitoring reliability parameters (MRP) for an engineering system with allowance for the drift in the measurement error of the means of measurement (MM). The approach is based on introducing a biased MM error distribution into the traditional formulas for the conditional probabilities of spurious and unobserved failure. The bias at the center of the distribution is determined by the systematic error at the given instant. An example is given to illustrate the performance in MRP calculation.Translated from Izmeritel'naya Tekhnika, No. 1, pp. 12–13, January, 1994. 相似文献
118.
This paper proposes a method to reduce the vibration of the three-phase HB-type stepping motor with cogging torque by the feedforward compensation control. The compensation signal to suppress the vibration of the motor frame is obtained by the repetitive controller installing an online Fourier transformer and utilizing an acceleration sensor attached to the motor frame or an acoustic sensor such as a microphone placed close to the frame. The sensor is used only for the acquisition of the feedforward compensation data. The feedforward compensation signal at an arbitrary operating point is derived from the amplitude and phase data of the frequency components and the operating point data. Compensation data obtained by the repetitive controller is applied to the operating point changed by reference frequency and load condition in steady state. The compensation signal for the new operating point will be generated from compensation data utilizing polynomial equation approximation and linear interpolation method. The effectiveness of this proposed method is confirmed by the experimental results. 相似文献
119.
120.