全文获取类型
收费全文 | 412篇 |
免费 | 11篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 22篇 |
综合类 | 5篇 |
化学工业 | 61篇 |
金属工艺 | 18篇 |
机械仪表 | 6篇 |
建筑科学 | 5篇 |
矿业工程 | 2篇 |
能源动力 | 8篇 |
轻工业 | 33篇 |
水利工程 | 1篇 |
无线电 | 70篇 |
一般工业技术 | 47篇 |
冶金工业 | 114篇 |
原子能技术 | 14篇 |
自动化技术 | 19篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2018年 | 7篇 |
2017年 | 1篇 |
2016年 | 8篇 |
2015年 | 3篇 |
2014年 | 10篇 |
2013年 | 10篇 |
2012年 | 11篇 |
2011年 | 14篇 |
2010年 | 7篇 |
2009年 | 15篇 |
2008年 | 17篇 |
2007年 | 15篇 |
2006年 | 5篇 |
2005年 | 17篇 |
2004年 | 13篇 |
2003年 | 13篇 |
2002年 | 14篇 |
2001年 | 11篇 |
2000年 | 15篇 |
1999年 | 11篇 |
1998年 | 48篇 |
1997年 | 26篇 |
1996年 | 13篇 |
1995年 | 12篇 |
1994年 | 11篇 |
1993年 | 13篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 10篇 |
1989年 | 9篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1976年 | 3篇 |
1973年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有425条查询结果,搜索用时 789 毫秒
411.
Machida Susumu Jun-Ichi Yamada Mukai Takaaki Horikoshi Yoshiji Tsuchiya Haruhiko Miya Tetsuo 《Electronics letters》1979,15(8):219-221
By using an InGaAsP semiconductor laser emitting at 1.5 ?m, where silica fibre loss is at a minimum, single-mode fibre transmission experiments were successfully carried out at 100 Mbit/s with about 30 km repeater spacing, 400 Mbit/s transmission characteristics using 20 km fibres are also reported. 相似文献
412.
Noise in an AlGaAs semiconductor laser amplifier 总被引:1,自引:0,他引:1
The noise characteristics in a Fabry-Perot (FP) cavity type semiconductor laser amplifier, biased at just below its oscillation threshold current, have been studied theoretically and experimentally. Quantum mechanical multimode rate equations containing a Langevin shot noise source and an input signal term were numerically solved for an exponential band-tail model with nok -selection rule. Noise power calculated using this rate equation was compared with a simpler photon statistic master equation method. The experimental results on noise power for an AlGaAs laser amplifier are in reasonable agreement with the two different theoretical predictions. Dominant noise powers in a semiconductor laser amplifier are beat noise powers between signal and spontaneous emission, and between spontaneous emission components. Noise characteristics in a Fabry-Perot cavity type laser amplifier can be improved both by the reduction of the facet mirror reflectivities and by use of an asymmetric cavity configuration with low-input and high-output mirror reflectivities. Two beat noise powers are expressed in simple analytic form by introducing an equivalent noise bandwidth and an excess noise coefficient as figures of merit in an optical amplifier. 相似文献
413.
A dielectric film technology characterized by a novel multilayer structure formed by oxidation of Ta2O5/Si3 N4 films on polysilicon has been developed to realize high-density dRAMs. The dry oxidation of the Ta2O5/Si3N4 layers was performed at temperatures higher than 900°C. This film has a capacitance per unit area from 5.5 to 6.0 fF/ μm2, which is equivalent to that of a 6.0- to 6.5-nm-thick SiO2. The leakage current at an effective electric field of 5 MV/cm is less than 10-9 A/cm2. Under such an electric field, the extrapolated time to failure for 50% cumulative failure can be as high as 1000 years 相似文献
414.
415.
Numerical analysis has been carried out for a waveguide with graded index and gain. It is shown that the radiation peak of the fundamental mode is deflected as the gradient of either the index or gain increases. The high-order modes also change their peak intensity ratio as the gradient of index or gain increases. The behavior of the fundamental mode is suitable for use in a beam scanner while that of higher-order modes is suitable for use in a deflection switching of laser beams. The analysis also shows that the modal gain of higher-order modes becomes larger than that of the fundamental mode as the gradient of the index and gain increases, which provides some explanation for the wide laser beam scanning observed by Scifres et al. 相似文献
416.
Fluctuation spectra due to quantum shot noise in the output from a junction laser are calculated using rate equations for a non-uniform double-sectioned laser with a low quantum-efficiency region. The pumping-rate dependence of the fluctuation spectra for the non-uniform model is found to be roughly the same as that for the ordinary uniform model. The degradation process is then simulated using the uniform and nonuniform models, and it is shown that qualitatively opposite changes, decay or growth of resonance phenomena, are ex- pected in the fluctuations as the degradation proceeds uniformly or nonuniformly. 相似文献
417.
Takashi Miyoshi Tokuya Kozaki Tomoya Yanamoto Yasushi Fujimura Shin‐ichi Nagahama Takashi Mukai 《Journal of the Society for Information Display》2007,15(2):157-160
Abstract— We succeeded in fabricating high‐output‐power blue (445 nm) laser diodes (LDs) with an output power of 500 mW. The operating current, voltage, and wall‐plug efficiency of these LDs were 480 mA, 4.8 V, and 21.7%, respectively. The lifetime of these LDs was estimated to be 10,000 hours under continuous‐wave operation at 25°C. From examination of the degradation mode, we found that the operating current seriously affects the lifetime of LDs. In the next stage, we will focuse on the optimization and sophistication of the manufacturing processes to fabricate longer‐lifetime (>30,000 hours) blue LDs. 相似文献
418.
Viscosities of slags constitute an important physical property needed for an understanding of the mass transfer phenomena in metallurgical processes. Viscosity is also the key that leads to a better understanding of the structure of slags. It is well‐known that the viscosities of silicate slags decrease with the addition of basic oxides due to the breaking of the silicate network. The measurements of slag viscosities often pose experimental challenges, especially with respect to the choice of materials. This paper takes up the experimental problems and the various techniques adopted. Dynamic viscosity measurement, as a powerful tool towards an understanding of the kinetics of some high temperature reactions is brought out. A number of semi‐empirical models have been developed to estimate the slag viscosities in the case of multicomponent slags. A critical survey of these models is presented in this paper. Earlier models by Riboud et al., Urbain et al. and Mills et al. have been developed further into a new generation of models. Some of the current important models are, (1) Model by lida et al., (2) CSIRO model, (3) Pyroresearch Model, (4) Model by Tanaka et al., (5) Model approach by Reddy et al., and (6) KTH‐model. The predictions and capabilities of the various models are compared. Estimations of viscosities from thermodynamic data and prediction of liquidus temperatures from viscosities are presented. The concept of surface viscosities with reference to slags and viscosities of two‐phase mixtures are also taken up in the presentation. 相似文献
419.
Pedro MS Hayashi NR Mukai T Ishii M Yokota A Igarashi Y 《Journal of Bioscience and Bioengineering》1999,88(1):92-97
Physiological and chemotaxonomical studies were carried out on microorganisms isolated from a composter operated at around 50 to 60 degrees C. Only gram-positive rods were isolated and the microbial counts on agar plates were relatively low (10(3) to 10(5) cfu/g-sample). The chemotaxonomic properties of the ten isolates revealed that they were typical of the genus Bacillus. Identification by the Biolog system concurred with the chemotaxonomy; all the strains were determined to be Bacillus. 16S rDNA analysis closely identified five of the isolates as B. licheniformis, one as B. subtilis, and two as B. thermoamylovorans, while the remaining two strains seemed to belong to a new species. However, in several cases 16S rDNA analysis and the Biolog system gave different results at the species level. The stability of microflora within the composter was also investigated using the Biolog system. Analysis of colonies obtained during three sampling periods--December 1997, April 1998, and June 1998--showed that the microflora in the composter remained fairly stable. 相似文献
420.
The dielectric properties of LaB6 crystals and the plasmonic behavior of LaB6 nanoparticles, which have been applied to solar heat-shielding filters, were studied by high energy-resolution electron energy-loss spectroscopy (HR-EELS). An EELS spectrum of a LaB6 crystal showed a peak at 2.0 eV, which was attributed to volume plasmon excitation of carrier electrons. EELS spectra of single LaB6 nanoparticles showed peaks at 1.1-1.4 eV depending on the dielectric effect from the substrates. The peaks were assigned to dipole oscillation excitations. These peak energies almost coincided with the peak energy of optical absorption of a heat-shielding filter with LaB6 nanoparticles. On the other hand, those energies were a smaller than a dipole oscillation energy predicted using the dielectric function of bulk LaB6 crystal. It is suggested that the lower energy than expected is due to an excitation at 1.2 eV, which was observed for oxidized LaB6 area. 相似文献