全文获取类型
收费全文 | 529篇 |
免费 | 6篇 |
专业分类
化学工业 | 148篇 |
金属工艺 | 53篇 |
机械仪表 | 19篇 |
建筑科学 | 8篇 |
矿业工程 | 4篇 |
能源动力 | 3篇 |
轻工业 | 15篇 |
水利工程 | 4篇 |
石油天然气 | 16篇 |
无线电 | 42篇 |
一般工业技术 | 91篇 |
冶金工业 | 78篇 |
原子能技术 | 25篇 |
自动化技术 | 29篇 |
出版年
2022年 | 4篇 |
2021年 | 16篇 |
2020年 | 9篇 |
2019年 | 11篇 |
2018年 | 17篇 |
2017年 | 21篇 |
2016年 | 7篇 |
2015年 | 7篇 |
2014年 | 15篇 |
2013年 | 26篇 |
2012年 | 37篇 |
2011年 | 20篇 |
2010年 | 21篇 |
2009年 | 15篇 |
2008年 | 20篇 |
2007年 | 13篇 |
2006年 | 11篇 |
2005年 | 20篇 |
2004年 | 7篇 |
2003年 | 10篇 |
2002年 | 14篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1995年 | 8篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1984年 | 13篇 |
1983年 | 9篇 |
1981年 | 10篇 |
1980年 | 4篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 9篇 |
1976年 | 13篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1973年 | 6篇 |
1972年 | 9篇 |
1971年 | 5篇 |
1970年 | 3篇 |
1966年 | 6篇 |
1965年 | 5篇 |
排序方式: 共有535条查询结果,搜索用时 15 毫秒
1.
D. G. Pavel’ev N. V. Demarina Yu. I. Koshurinov A. P. Vasil’ev E. S. Semenova A. E. Zhukov V. M. Ustinov 《Semiconductors》2004,38(9):1105-1110
Characteristics of ohmic InGaAs contacts in planar diodes based on semiconductor superlattices with a small-area active region
(1–10 μm2) are studied. The diodes were formed on the basis of short (18 or 30 periods) heavily doped (1018 cm−3) GaAs/AlAs superlattices with a miniband width of 24.4 meV. The reduced resistance of the ohmic contact was equal to 2×10−7 Ω cm2 at room temperature. It is shown that the properties of fabricated planar diodes make it possible to use these diodes later
on in semiconductor devices that operate in the terahertz frequency region in a wide temperature range (4–300 K).
__________
Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 38, No. 9, 2004, pp. 1141–1146.
Original Russian Text Copyright ? 2004 by Pavel’ev, Demarina, Koshurinov, Vasil’ev, Semenova, Zhukov, Ustinov. 相似文献
2.
L. G. Gerchikov Yu. A. Mamaev A. V. Subashiev Yu. P. Yashin D. A. Vasil’ev V. V. Kuz’michev A. E. Zhukov E. S. Semenova A. P. Vasil’ev V. M. Ustinov 《Semiconductors》2006,40(11):1326-1332
Photoemission of polarized electrons from heterostructures based on InAlGaAs/GaAs superlattices with minimum conduction-band offsets is investigated. The comparison of the excitation energy dependence of the photoemission polarization degree with the calculated spectra make it possible to determine the polarization losses at different stages of the photoemission. A maximum polarization of P = 91% and a quantum yield of 0.14% are close to the best results obtained for photocathodes on the basis of strained semiconductor superlattices. 相似文献
3.
A. N. Gudkov V. M. Zhivun A. V. Zvonarev V. V. Kovalenko A. B. Koldobskii Yu. F. Koleganov S. V. Krivasheev V. B. Pavlovich N. S. Piven' E. V. Semenova 《Atomic Energy》1989,66(2):115-118
Translated from Atomnaya Énergiya, Vol. 66, No. 2, pp. 100–103, February, 1989. 相似文献
4.
L. Ya. Karachinsky T. Kettler N. Yu. Gordeev I. I. Novikov M. V. Maximov Yu. M. Shernyakov N. V. Kryzhanovskaya A. E. Zhukov E. S. Semenova A. P. Vasil’ev V. M. Ustinov N. N. Ledentsov A. R. Kovsh V. A. Shchukin S. S. Mikhrin A. Lochmann O. Schulz L. Reissmann D. Bimberg 《Semiconductors》2005,39(12):1415-1419
Lasers based on InAs/InGaAs quantum dots grown on metamorphic (In,Ga,Al)As layers deposited by MBE on GaAs substrates exhibited emission near 1.5 μm with a differential quantum efficiency of about 50%. The narrow-stripe lasers operate in a single transverse mode and withstand continuous current density above 20 kA cm?2 without significant degradation. A maximum continuous-wave output power of 220 mW is obtained. Neither current nor beam filamentation was observed up to the highest pumping levels. 相似文献
5.
The authors propose an approach to solving problems of deformation of nonsymmetrically loaded shells of revolution whose boundary contours are supported in the general case at individual points. The problem is substituted by a problem with the boundary conditions of the same type around the entire contour which contain unknown parameters determined from the condition of converting to zero the displacements at the support points. Consequently, the problem is reduced to integrating systems of conventional differential equations and solving a system of algebraic equations. The solution of a problem of the stressed state of a hyperbolic shell, supported at four points at the contour, is presented.
Translated from Problemy Prochnosti, No. 8, pp. 31–35, August, 1992. 相似文献
6.
I. I. Novikov N. Yu. Gordeev M. V. Maksimov Yu. M. Shernyakov E. S. Semenova A. P. Vasil’ev A. E. Zhukov V. M. Ustinov G. G. Zegrya 《Semiconductors》2005,39(4):481-484
Semiconductor laser heterostructures containing five and ten sheets of InAs/GaAs QDs on GaAs substrates, with an emission wavelength of ~1.3 μm, have been studied. Dependences of the nonradiative lifetime and effective Auger coefficient in QDs are obtained from an analysis of temperature and current dependences of the efficiency of spontaneous radiative recombination. The zero-threshold Auger recombination channel in QDs is shown to dominate at low (below 200 K) temperature, whereas at higher temperatures the quasithreshold channel becomes dominant. The effective 3D Auger coefficient is estimated in the approximation of a spherical QD, and a good agreement with the experimental data is obtained. 相似文献
7.
8.
Conclusions Heat treatment of the resin-bonded refractories in an atmosphere consisting of the products of sublimation and decomposition of the binder leads to a significant improvement in the properties of the specimens (in particular, in the coked condition). The increase in the content of the residual carbon, the mechanical strength of the specimens, and their hydration resistance are determined by the heat treatment temperature. The highest levels of the physical and the technological properties are obtained after heat treating the specimens in the 400–600°C range. In this case, the most significant effect is observed in the lime-periclase refractories and the minimum effect is obtained in the resin-periclase refractories.The increased hydration resistance of the resin-bonded refractories containing free calcium oxide (the lime-periclase and the periclase-lime refractories) owes mainly to fixing up of CaO during the heat treatment process and to the formation of the protective calcium carbonate films at the surface of the fired dolomite grains.Translated from Ogneupory, No. 2, pp. 10–13, February, 1992. 相似文献
9.
N. P. Kruchinin V. V. Romanov V. G. Kulichikhin A. S. Semenova V. E. Sorokin 《Fibre Chemistry》1985,16(6):431-433
Conclusions Oksalon yarns do not display an accumulation of plastic deformations in sulfuric acid solutions in stretching in a creep regime, up to a concentration of about 80% by wt.The equilibrium reversible deformation which is reached under conditions of constant tension has a maximum at a sulfuric acid content in the solution of about 70%, and a minimum at 72–73%.The characteristic changes in deformation properties of yarns as a function of the sulfuric acid content of the stretching medium are explained by structural changes which occur in the polyoxadiazole.Stretching Oksalon yarns in a 75% sulfuric acid solution leads to a 25–30% rise in the strength of washed and dried yarnsTranslated from Khimicheskie Volokna, No. 6, pp. 34–36, November–December, 1984. 相似文献
10.
The article considers the problem of estimating the parameters of the autoregressive (AR) signal in the presence of background noise. Based on the frequency representation of the AR signal, a technique of calculating the likelihood function of the AR parameters is shown and the implementation of the Expectation-Maximization method for iterative evaluation of the AR parameters is considered. Analysis of different measures of distortion of speech signals shows that the proposed approaches in the frequency domain have the same accuracy as the corresponding approaches in the time domain, but are characterized by significantly lower computing costs.
相似文献