全文获取类型
收费全文 | 285篇 |
免费 | 16篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 82篇 |
金属工艺 | 5篇 |
机械仪表 | 2篇 |
建筑科学 | 11篇 |
能源动力 | 12篇 |
轻工业 | 28篇 |
无线电 | 34篇 |
一般工业技术 | 46篇 |
冶金工业 | 35篇 |
原子能技术 | 3篇 |
自动化技术 | 41篇 |
出版年
2024年 | 2篇 |
2023年 | 2篇 |
2022年 | 11篇 |
2021年 | 11篇 |
2020年 | 9篇 |
2019年 | 5篇 |
2018年 | 10篇 |
2017年 | 9篇 |
2016年 | 9篇 |
2015年 | 9篇 |
2014年 | 17篇 |
2013年 | 15篇 |
2012年 | 18篇 |
2011年 | 16篇 |
2010年 | 15篇 |
2009年 | 6篇 |
2008年 | 13篇 |
2007年 | 14篇 |
2006年 | 4篇 |
2005年 | 2篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 7篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 13篇 |
1997年 | 6篇 |
1996年 | 7篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1992年 | 9篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1974年 | 4篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有302条查询结果,搜索用时 0 毫秒
1.
Narayanaswami C. Kamijoh N. Raghunath M. Inoue T. Cipolla T. Sanford J. Schlig E. Venkiteswaran S. Guniguntala D. Kulkarni V. Yamazaki K. 《Computer》2002,35(1):33-41
Nearly four years in development, the IBM Linux watch contains a complete computer system that runs Linux, displays X11 graphics, and has wireless connectivity. The system fits in a case that could pass as a slightly unusual analog timepiece with a somewhat odd shape and an extraordinarily brilliant face. The developers have created two versions of the watch, one with an organic light-emitting diode display and the other with a liquid crystal display. Still considered a research prototype, the watch already runs some personal information management applications, and it can communicate with PCs, PDAs, and other wireless-enabled devices, viewing condensed e-mail and directly receiving pager-like messages. Eventually, users will be able to access various Internet-based services, such as up-to-the-minute information about weather, traffic conditions, the stock market, and sports 相似文献
2.
The finite-data performance of a minimum-variance distortionless response (MVDR) beamformer is analyzed with and without spatial smoothing, using first-order perturbation theory. In particular, expressions are developed for the mean values of the power gain in any direction of interest, the output power, and the norm of the weight-error vector, as a function of the number of snapshots and the number of smoothing steps. It is shown that, in general, the smoothing, in addition to decorrelating the sources, can alleviate the effects of finite-data perturbations. The above expressions are reduced to the case in which no spatial smoothing is used. These expressions are valid for an arbitrary array and for arbitrarily correlated signals. For this case, an expression for the variance of the power gain is also developed. For a single interference case it is shown explicitly how the SNR, spacing of the interference from the desired signal and the correlation between them influence the beamformer performance. Simulations verify the usefulness of the theoretical expressions 相似文献
3.
Design aspects of MOS-controlled thyristor elements: technology,simulation, and experimental results
Bauer F. Halder E. Hofmann K. Haddon H. Roggwiller P. Stockmeier T. Burgler J. Fichtner W. Muller S. Westermann M. Moret J.-M. Vuilleumier R. 《Electron Devices, IEEE Transactions on》1991,38(7):1605-1611
2.5-kV thyristor devices have been fabricated with integrated MOS controlled n+-emitter shorts and a bipolar turn-on gate using a p-channel DMOS technology. Square-cell geometries with pitch variations ranging from 15 to 30 μm were implemented in one- and two-dimensional arrays with up to 20000 units. The impact of the cell pitch on the turn-off performance and the on-state voltage was studied for arrays with constant cathode area as well as for single-cell structures. By realizing MOS components with submicrometer channel lengths, scaled single cells are shown to turn off with current densities of several kiloamperes per square centimeter at a gate bias of 5 V. In the case of multi-cell ensembles, turn-off performance is limited due to inhomogeneous current distribution. Critical process parameters as well as the device behavior were optimized through multidimensional numerical simulation 相似文献
4.
G. N. Lilis A. Halder S. Telukunta S. Servetto 《International journal for numerical methods in engineering》2007,71(3):277-312
Many problems in geophysics, acoustics, elasticity theory, cancer treatment, food process control and electrodynamics involve study of wave field synthesis (WFS) in some form or another. In the present work, modelling of wave propagation phenomena is studied as a static problem, using finite element method and treating time as an additional spatial dimension. In particular, WFS problems are analysed using discrete methods. It is shown that a fully finite element-based scheme is very natural and effective method for the solution of such problems. Distributed WFS in the context of two-dimensional problems is outlined and incorporation of any geometric or material non-linearities is shown to be straightforward. This has significant implications for problems in geophysics or biological media, where material inhomogeneities are quite prevalent. Numerical results are presented for several problems referring to media with material inhomogeneities and predefined absorption profiles. The method can be extended to three-dimensional problems involving anisotropic media properties in a relatively straightforward manner. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
5.
Y von Kodolitsch M Raghunath C Dieckmann CA Nienaber 《Canadian Metallurgical Quarterly》1998,87(3):161-172
BACKGROUND: Despite the availability of several different markers for Epstein--Barr virus (EBV) serology, the EBV status of some patients cannot be resolved from a single serum sample with routine testing. To avoid the requirement of follow-up samples, supplementary tests have to be used in these cases. OBJECTIVE: To evaluate the usefulness of avidity and immunoblot assays as supplementary tests for the diagnosis of acute EBV infections. STUDY DESIGN: Three groups of samples for which a definite diagnosis on the EBV status could not be obtained with the routine serological tests were further examined by an EBV IgG avidity assay, by an immunoblot based on a lysate of EBV infected cells, and by a second immunoblot based on recombinant EBV antigens. The three groups consisted of 38 samples with negative/borderline EB nuclear antigen 1 (EBNA-1) antibodies, negative/borderline EBV IgM and positive EBV IgG; 10 samples with indeterminate EBNA-1 and/or EBV IgM assays because of control antigen reactions; and 4 samples with positive EBV IgM results that were not plausible. RESULTS: The avidity assay differentiated between acute and past infections for all samples. In contrast, some cases remained unresolved with both the recombinant and the lysate immunoblot. Two samples were incorrectly classified with the lysate immunoblot. Interpretation of the lysate immunoblot banding patterns was complicated when anticellular antibodies were present. CONCLUSION: Avidity testing appears to be the confirmatory method of choice to differentiate between acute and past EBV infections. 相似文献
6.
Spherical electrode carbon particles prepared from carbon rods of dry cell batteries have been used to study the attrition behaviour in a bubbling fluidized bed combustor. Experiments have been conducted in a 40 mm I.D. and 1 m high fluidized bed combustor operated at 1 m/s superficial velocity. The bed was operated with nitrogen and with two different oxygen concentrations at 850°C to study the effect of combustion on attrition of these particles. The experimental technique used allowed the time resolution of attrited fines generation, providing detailed curves of attrition rates as a function of time. Attrition rate constants have been evaluated. Results show an enhancement of attrition due to combustion even for spherical, homogeneous and smooth particles. 相似文献
7.
Raghunath P. Tripathi Jogindar S. Bahl Ramesh C. Purohit 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1974,24(9):505-514
In the present investigation, the effect of three process variables viz., air rate, temperature and time of oxidation has been studied to determine the possibility of making paving bitumens from North Rumaila Crude Oil. In order to have flexibility in the choice of proper feedstock for bitumen production, the effect of these process parameters was studied on three different vacuum residues. Air rate and temperature of oxidation were optimised to produce a bitumen product having less temperature susceptibility. The composition studies of typical feeds and oxidised products indicate that mainly “saturates” components get converted to “asphaltics” on air blowing. 相似文献
8.
The combustion of single bituminous char particles (4-12 mm diameter) was studied in a turbulent fluidized bed operated at 1098 K using air as the fluidising medium. Results indicated that particles burn with constant density following a shrinking sphere model. Burning rates are much higher than those observed in a bubbling fluidized bed. The rate of transfer of oxygen to the particle surface is also higher than that observed in bubbling beds. A model is proposed to calculate the Sherwood numbers of the burning carbon particles. Experimental values of the Sherwood numbers agree well with those predicted from the model. 相似文献
9.
Raghunath P. Rana Swadesh K. Pratihar Santanu Bhattacharyya 《Journal of Materials Science》2006,41(21):7025-7032
Al2O3–ZrO2 composites containing nominally equal volume fraction of Al2O3 and ZrO2 have been synthesized through combined gel-precipitation technique. Subsequently the gels were subjected to three different post gel processing treatments like ultrasonication, ultrasonication followed by water washing and ultrasonication followed by alcohol washing. It was observed that while in unwashed samples crystallization took place at low temperature, crystallization was delayed in the washed gels. The phase transition of ZrO2 in the calcined gels followed the sequence; amorphous → cubic ZrO2 → tetragonal ZrO2 → monoclinic ZrO2. On the other hand, phase transition in alumina followed the sequence amorphous to γ-Al2O3, the transition taking place at 650 °C. No α-Al2O3 could be detected even after calcination at 950 °C. However, all the sintered samples had α-Al2O3. In spite of high linear shrinkage (19–21%) during sintering, the sintered sample had density of only above 70% for all the four varieties of the powders. However, in spite of the low sintered density of the pellets, 31% tetragonal zirconia could be retained after sintering at 1400 °C and it reduced to about 16% at 1600 °C. 相似文献
10.
Graeve Olivia A. Madadi Abhiram Kanakala Raghunath Sinha Kaustav 《Metallurgical and Materials Transactions A》2010,41(10):2691-2697
Tungsten nanopowders were synthesized by a low-temperature technique and then heat treated in a gaseous reductive atmosphere
in order to study the phase evolution, crystallite size, and particle size of the powders as the heat treatment temperature
was modified. Synthesis of the powders was carried out in aqueous media using NaBH4 as a reducing agent using careful control of the pH of the solutions. The XRD patterns of the as-synthesized powders showed
an amorphous phase. After washing, energy dispersive spectroscopy showed that the powders had peaks for oxygen and tungsten.
In order to promote crystallization and eliminate the oxygen, the powders were heat treated at 773 K, 923 K, and 1073 K (500 °C,
650 °C, and 800 °C) in a H2/CH4 reducing atmosphere for 2 hours. XRD after heat treatment showed α-W peaks for the powders treated at 1073 K and 923 K (800 °C and 650 °C) and a mixture of β-W and α-W for the powders treated at 773 K (500 °C). The crystallite sizes determined from X-ray peak broadening were 12, 16, and
20 nm, whereas the average particle sizes from dynamic light scattering were 260, 450, and 750 nm, for heat treatment temperatures
of 773 K, 923 K, and 1073 K (500 °C, 650 °C, and 800 °C), respectively. The average crystallite size and particle sizes increased
proportionally with the treatment temperature, in contrast to what has been found for some ceramics, in which as the heat
treatment temperature is increased, the crystallite size increases, but the particle size stays constant. 相似文献