全文获取类型
收费全文 | 909篇 |
免费 | 17篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 41篇 |
化学工业 | 127篇 |
金属工艺 | 43篇 |
机械仪表 | 3篇 |
建筑科学 | 10篇 |
能源动力 | 26篇 |
轻工业 | 13篇 |
水利工程 | 3篇 |
石油天然气 | 2篇 |
无线电 | 232篇 |
一般工业技术 | 211篇 |
冶金工业 | 102篇 |
原子能技术 | 3篇 |
自动化技术 | 112篇 |
出版年
2022年 | 8篇 |
2021年 | 11篇 |
2020年 | 15篇 |
2019年 | 16篇 |
2018年 | 19篇 |
2017年 | 15篇 |
2016年 | 16篇 |
2015年 | 11篇 |
2014年 | 13篇 |
2013年 | 39篇 |
2012年 | 18篇 |
2011年 | 39篇 |
2010年 | 23篇 |
2009年 | 43篇 |
2008年 | 29篇 |
2007年 | 33篇 |
2006年 | 36篇 |
2005年 | 27篇 |
2004年 | 21篇 |
2003年 | 30篇 |
2002年 | 26篇 |
2001年 | 26篇 |
2000年 | 17篇 |
1999年 | 16篇 |
1998年 | 30篇 |
1997年 | 28篇 |
1996年 | 26篇 |
1995年 | 36篇 |
1994年 | 25篇 |
1993年 | 17篇 |
1992年 | 20篇 |
1991年 | 23篇 |
1990年 | 19篇 |
1989年 | 10篇 |
1988年 | 22篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 5篇 |
1983年 | 13篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1974年 | 6篇 |
1971年 | 4篇 |
1970年 | 4篇 |
排序方式: 共有928条查询结果,搜索用时 46 毫秒
91.
M. H. Kim S. S. Bose B. J. Skromme B. Lee G. E. Stillman 《Journal of Electronic Materials》1991,20(9):671-679
Variable temperature Hall effect and low temperature photoluminescence measurements have been performed on high purityp- andn-type GaAs grown at atmospheric pressure by metalorganic chemical vapor deposition. These high purity epitaxial GaAs layers
were grown as a function of the arsine (AsH3) to trimethylgallium (TMG) ratio (V/III ratio). The accurate quantitative assessment of the electronic properties of thep-type layers was emphasized. Analysis of the material focussed on the variation of the concentration of the shallow impurities
for different V/III ratios. Surface and interface depletion effects are included to accurately estimate the concentration
of impurities. The model of the merging of the excited states of the acceptor with the valence band is used to include the
dependence the activation energy of the impurity on the acceptor concentration as well as on acceptor species identity. The
characteristicp- ton-type conversion with increasing V/III ratio was observed in these samples and the reason for thep- ton-type conversion is that the background acceptor concentration of carbon decreases and the germanium donor concentration increases
as the V/III ratio is increased. 相似文献
92.
The nonisothermal oxidation behavior of pure iron and a few iron-chromium alloys in dry air has been studied. The effects of a superficial coating of a reactive oxide, CeO2, on the oxidation behavior were studied. Linear heating rates of 3 K/min and 6 K/min were maintained up to a final temperature ranging from 1273–1473 K. Coatings were applied either from a slurry or an aqueous bath. The CeO2 coating has been found to be effective not only in decreasing the nonisothermal oxidation rate but also in improving the scale adherence. Moreover, the coated samples withstood a number of heating cycles without scale rupture. The mass gain of the samples as a function of temperature was recorded by means of a sensitive balance, and the scales have been characterized by SEM, EPMA, and x-ray diffraction analysis. 相似文献
93.
94.
95.
Khemka V. Parthasarathy V. Zhu R. Bose A. Roggenbauer T. 《Electron Devices, IEEE Transactions on》2002,49(6):1049-1058
Thermal and electrical destruction of 55 V single and double reduced surface field (RESURF) lateral double-diffused MOSFETs (LDMOSFETs) in smart power ICs are investigated by experiments, simulations, and theoretical modeling. Static safe operating area (SOA) and single pulse dynamic SOA (energy capability) have been studied and correlated. Single RESURF device failure and hence the energy capability is controlled by electrical phenomenon for drain to source voltage near breakdown voltages, whereas the energy capability of the double RESURF device is shown to be controlled by thermal phenomenon for voltage ranges up to about 5 V below the breakdown voltage. Measured energy capability data have been used to obtain critical temperatures for device failure, which decreases with an increase in drain to source voltage. We have empirically shown using experimental data that if the dynamic SOA of the device comes within about 2-5× of the static SOA boundary, the device failure is strongly influenced by avalanche multiplication. An analytical model based on Green's function formulation is derived and proposed which can predict energy capability of LDMOSFETs for a wide range of device geometry. The calculated data show excellent matching with the measurements and are within ±10%. A new technique of distributing power within a device by applying less power at the center and more at the edges is proposed, which realizes significant improvement in energy capability by optimizing the temperature distribution within the device 相似文献
96.
Water-dispersible graphene was prepared by reacting graphite oxide and 6-amino-4-hydroxy-2-naphthalenesulfonic acid (ANS). X-ray diffraction study showed that the basal reflection (002) peak of graphite oxide was absent in the ANS-functionalized graphene (ANS-G), indicating crystal layer delamination. Ultraviolet-visible spectral data were recorded to assess the solubility of the ANS-G in water. Fourier transform infrared spectral analysis suggested the attachment of ANS molecules to the surface of graphene. Raman and x-ray photoelectron spectroscopy revealed that oxygen functionality in the graphite oxide had been removed during reduction. Atomic force microscopy found that the thickness of ANS-G in water was about 1.8 nm, much higher than that of single layer graphene. Thermal stability measurements also indicated successful removal of oxygen functionality from the graphite oxide and the attachment of thermally unstable ANS to the graphene surfaces. The electrical conductivity of ANS-G, determined by a four-point probe, was 145 S m(-1) at room temperature. 相似文献
97.
Aniruddha Chandra Chayanika Bose Manas Kr. Bose 《International Journal of Communication Systems》2011,24(2):153-167
Following a unified analytical framework, the bit error rate (BER) of several coherent and non‐coherent binary modulation schemes is derived for a switched diversity system. The two variants of switched combining that have been investigated are switch and stay combining and switch and examine combining. For channel modelling, at first a simple slow flat fading channel is assumed, where the amplitude attenuation obeys the Rayleigh distribution. Later the BER calculations are repeated for cascaded Rayleigh fading channel case. Rayleigh fading is the most popular model for electromagnetic signal propagation in wireless media when both or either of the transmitter/receiver is fixed. On the other hand, when both the transmitter and the receiver are mobile, a cascaded (or double) Rayleigh fading model is better suited. The applicability of these two models, namely simple and cascaded Rayleigh model, has been indicated by several theoretical studies and their suitability is established by various field measurements. In our paper, simple closed‐form BER expressions as a function of switching threshold have been found and optimum switching thresholds have been computed for both these models as well as for both types of diversity combining described earlier. The results presented in this paper can be very useful for communication system designers to analyze link quality of switched diversity assisted systems in various wireless environments. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
98.
Aniruddha Chandra Srinivasa Rao Poram Chayanika Bose 《International Journal of Communication Systems》2011,24(2):202-224
In this paper, the authors derive symbol error probability (SEP) expressions for coherent M‐ary frequency shift keying (MFSK) modulation schemes in multipath fading channels. The multipath or small‐scale fading process is assumed to be slow and frequency non‐selective. In addition, the channel is also subjected to the usual degradation caused by the additive white Gaussian noise (AWGN). Different small‐scale fading statistics such as Rayleigh, Rician (Nakagami‐n), Hoyt (Nakagami‐q), and Nakagami‐m have been considered to portray diverse wireless environments. Further, to mitigate fading effects through space diversity, the receiver front‐end is assumed to be equipped with multiple antennas. Independent and identically distributed (IID) as well as uncorrelated signal replicas received through all these antennas are combined with a linear combiner before successive demodulation. As the detection is coherent in nature and thus involves phase estimation, optimum phase‐coherent combining algorithms, such as predetection maximal ratio combining (MRC), may be used without any added complexity to the receiver. In the current text, utilizing the alternate expressions for integer powers (1≤n≤4) of Gaussian Q function, SEP values of coherent MFSK are obtained through moment generating function (MGF) approach for all the fading models (with or without MRC diversity) described above. The derived end expressions are composed of finite range integrals, which can be numerically computed with ease, dispenses with the need of individual expressions for different M, and gives exact values up to M=5. When the constellation size becomes bigger (M≥6), the same SEP expressions provide a quite realistic approximation, much tighter than the bounds found in previous literatures. Error probabilities are graphically displayed for each fading model with different values of constellation size M, diversity order L, and for corresponding fading parameters (K, q, or m). To validate the proposed approximation method extensive Monte‐Carlo simulations were also performed, which show a close match with the analytical results deduced in the paper. Both these theoretical and simulation results offer valuable insight to assess the efficacy of relatively less studied coherent MFSK in the context of the optimum modulation choice in wireless communication. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
99.
Micro editor in chief Pradip Bose talks about the issue of workload characterization in the modern setting. 相似文献
100.
S. Chattopadhyay L. K. Bera C. K. Maiti S. K. Ray P. K. Bose D. Dentel L. Kubler J. L. Bischoff 《Journal of Materials Science: Materials in Electronics》1998,9(6):403-407
PtSi/p-strained-Si1-xGex (x=0.19 and x=0.29) Schottky barrier diodes have been fabricated and characterized for the determination of barrier height, ideality factor and the interface state density distribution with energy. Diodes having an epitaxial layer thickness of 20 and 52 nm were modeled with emphasis on comparison with experiment. To achieve better agreement with experimental data, an interfacial layer and associated series resistance were included in the model. The capacitance–voltage (C–V) technique has been used for the determination of the energy distribution of interface state density. The interface state density distribution for the Si0.81Ge0.19 and Si0.71Ge0.29 diodes is found to decrease with increasing energy from the valence band edge. 相似文献