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排序方式: 共有193条查询结果,搜索用时 78 毫秒
181.
M. S. Haque U. V. Patel H. A. Naseem W. D. Brown 《Journal of Electronic Materials》1995,24(6):761-766
Atmospheric pressure chemical vapor deposition (APCVD) of tungsten films using WF6/H2 chemistry has been studied. A statistical design of experiments approach and a surface response methodology were used to
determine the most important process parameters and to obtain the best quality film possible in the parameter range studied.
It was found that the deposition rate depends strongly on WF6 flow rate, temperature, and the interaction between hydrogen flow rate and temperature. The resistivity was found to have
a strong dependence on WF6 and H2 flow rates and temperature. An activation energy of 0.4 eV was calculated for the reaction rate limited growth regime. Empirical
equations for predicting the deposition rate and resistivity were obtained. The resistivity decreases with both increasing
film thickness and grain size. The films grown in the studied process parameter range indicate that (110) is the preferred
orientation for films deposited with low WF6/H2 flow rate ratios at all deposition temperatures (350–450°C), whereas, the (222) orientation dominates at high WF6/H2 flow ratios and high deposition temperatures. Also, the grain size is larger for (222) oriented films than for (110) oriented
films. The results of this study suggest that high-quality, thin film tungsten can be deposited using APCVD. 相似文献
182.
The binding characteristics of saxitoxin (STX), a known voltage-gated sodium channel blocker, and its analog saxitoxinol (STXOL), were studied in neuroblastoma, peritoneal macrophage, hepatocytes and PC-12 cell lines. 3H-STXOL bound to the cell-surface sites which appear to be the same as those occupied by 3H-STX and which can, therefore, be identified as STX receptors. The relative agreement of respective Kd obtained by saturation, competition, association and dissociation kinetics for STX and STXOL suggest the absence of any artifact in binding measurements. Unlike STX, STXOL was non-toxic to mice by intratracheal instillation. The major advantage of using 3H-STXOL is that the tritium label is not exchangeable. Data from this study suggest that 3H-STXOL can be used to identify STX receptors at 37 degrees C. 相似文献
183.
Oleg Rybin Muhammad Raza Tahira Nawaz Tahir Abbas 《AEUE-International Journal of Electronics and Communications》2009,63(8):648-652
In this paper, analytical modeling and numerical simulation of the complex effective dielectric, magnetic constants and refractive index of a metallic rod metamaterial in microwave frequency range are presented. Analytical modeling has been done using modified mathematical models of the complex dielectric and magnetic constants obtained for rod metamaterial structure. Numerical simulation of the above-mentioned parameters has been made using S-parameters obtained with the help of finite-difference time-domain (FDTD) calculations. The numerical simulation has been carried out for different thickness of rods. Remarkable coincidence between analytical and numerical results was found. The effective dielectric constant enhancement of the considered composite has been obtained. Recommendations for the practical application of considered metamaterial structure for designing patch antennas have been discussed. 相似文献
184.
Robert Christopher; Probst Tahira M.; Martocchio Joseph J.; Drasgow Fritz; Lawler John J. 《Canadian Metallurgical Quarterly》2000,85(5):643
Although variations in national cultures predominate as explanations for the belief that universal approaches to management do not exist, there have been few reports of systematic studies. Data from employees of a single firm with operations in the United States, Mexico, Poland, and India were used to test the fit of empowerment and continuous improvement practices with national culture. Using the theoretical constructs of individualism–collectivism and power distance, the authors predicted that the practices would be more congruent in some cultures than in others and that value congruence would result in job satisfaction. Using structural equations modeling, the authors found that empowerment was negatively associated with satisfaction in India but positively associated in the other 3 samples. Continuous improvement was positively associated with satisfaction in all samples. Substantive, theoretical, and methodological implications are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
185.
Husam H. Abu-Safe Marouf Hossain Hameed Naseem William Brown Abdullah Al-Dhafiri 《Journal of Electronic Materials》2004,33(2):128-134
The CdS:Cl thin films have been prepared using thermally evaporated, CdCl2-mixed CdS powder at 200°C substrate temperature. The percentage of CdCl2 in the mixture varied from 0% to 0.20%. The electrical properties and the grain size of the deposited films were investigated.
The results show that light doping, resistivity, carrier concentration, and mobility follow Seto’s model for polycrystalline
material. However, with heavy doping, these properties undergo a saturation trend. The saturation behavior can be understood
in terms of the rapid formation of the A-center complexes in the films. The deposited films were annealed at 250°C and 300°C.
The resistivity of pure and lightly doped CdS films increased with annealing temperature, whereas carrier concentration and
mobility in these films decreased. However, for the higher doping concentrations, the resistivity decreased, whereas carrier
concentration and mobility showed improvement. These changes in electrical properties of the deposited films with annealing
and doping concentration are attributed to a reduction in the lattice defect sites in CdS upon annealing. The experimental
results are interpreted in terms of a modified version of Seto’s model for polycrystalline materials. 相似文献
186.
Physical properties of memory quality PECVD silicon nitride 总被引:1,自引:0,他引:1
M. A. Khaliq Q. A. Shams W. D. Brown H. A. Naseem 《Journal of Electronic Materials》1988,17(5):355-359
Memory-quality silicon nitride has been deposited using plasma-enhanced chemical vapor deposition (PECVD). Film composition
was varied by controlling the nitrogen concentration of the reactant gases. The effects of the source and content of the nitriding
agent on the physical properties of the film were studied using ellipsometry and ultraviolet (UV), fourier transform infrared
(FTIR) and Auger electron spectroscopy. Refractive index of the films varied from 1.77 to 1.95 corresponding to Si/N ratios
of 0.75 to 1.03. Ultraviolet spectroscopy yielded band edge values of 4.9 to 2.2 eV depending on the Si/N ratio. Window size,
endurance and retention performance is comparable to that reported for both atmospheric- and low-pressure chemical vapor deposited
films. A strong correlation between the Si-H bond concentration and the memory performance was observed. Although some excess
silicon in the film is needed for memory operation in a metal-nitride-oxide-silicon (MNOS) structure, excessive amounts result
in low breakdown fields, small memory windows and poor retention characteristics.
This work was supported by a grant from the National Science Foundation. 相似文献
187.
Auger Depth Profiling of Carbonized SiC/Si Samples 总被引:1,自引:0,他引:1
Silicon carbide (SiC) has been prepared by passing natural gas over (100) oriented hot Si substrate at different temperatures in the range 930~1000℃. Reaction times of 60 and 90 min are used.Depth profile, using Auger Electron Spectroscopy, shows the formation of SiC under a thin coating of carbon for the samples prepared at 930 and 950℃. Annealing, at 1050℃ for 12 h,results in a more pronounced formation of SiC. It is found that at the temperature of 1000℃and reaction times of 60 and 90 min, a hard diamond-like coating is formed. 相似文献
188.
Tuuli Toivonen Risto Kalliola Kalle Ruokolainen Riffat Naseem Malik 《Remote sensing of environment》2006,100(4):550-562
An analysis of tropical rain forest covering Amazonian lowlands has highlighted a systematic across-path, east–west radiometric gradient within Landsat TM imagery. Visual assessment of 45 and quantitative analysis of 20 Amazonian Landsat-4 and -5 TM scenes show that the gradient is band dependent and pronounced in visible light bands 1 to 3 but significant also in IR bands 4 to 7. The results show that the scan line location of a pixel explains a considerable amount of the DN variation of forests in the width of the entire scene (B1: 70%, B2: 52%, B3: 44%, B4: 34%, B5: 46%, B7: 39%). In digital numbers, the difference between east and west side of a scene may be small (9, 4, 3, 10, 9, 3, respectively) but these differences become significant if the images are to be mosaicked, or the data are used for mapping relatively subtle differences of natural forests. Apparently, the gradient is a result of at least three factors: 1) shadows caused by the undulating terrain, 2) anisotropic reflectance of the varying surfaces, and 3) atmospheric scattering. The phenomenon becomes more significant when the sun is high and the scanning line is close to solar azimuth direction—a condition more easily encountered in lower latitudes of the earth. 相似文献
189.
Usman Allauddin Rafay Mohiuddin Hafiz Mohammad Usman Khan Naseem Uddin Waqar A. Khan 《亚洲传热研究》2021,50(1):81-104
In the current numerical study, the thermal and flow field performance of an array of confined multiple jets with air, water, and water‐Al2O3 nanofluid in the maximum crossflow configuration over the target plate with and without pin fins is investigated. The numerical results are validated with the experimental data; it is found that a reasonable prediction related to heat transfer can be made. For this study, steady‐state Reynolds‐averaged Navier‐Stokes simulations with the shear‐stress transport turbulence model in ANSYS Fluent were performed. The simulations are performed with volumetric concentration to 3% and the jet's Reynolds number Re = 15 000 to 35 000. In all cases, the jet outlet‐to‐target plate distance is 3. It is found that the increase in values of the volumetric concentration of nanoparticles results in a decrease of the Nusselt number and an increase of the convective heat transfer coefficient. This is because there is an increase in thermal conductivity of the working fluid with the increase in the volumetric concentration of nanoparticles for the same Reynolds number. About 81.5% and 89.1% enhancement in the average heat transfer flux values is observed for flat and pin fin‐roughened target plates, respectively, for . 相似文献
190.
Waqas Wakil Muhammad Ashfaq M.U. Ghazanfar Tahira Riasat 《Journal of Stored Products Research》2010,46(4):248-249
Mortality of adult Rhyzopertha dominica (F.), Sitophilus oryzae (L.) and Tribolium castaneum (Herbst) was recorded after exposure for different times to application rates of 0, 0.5, 1, 1.5 or 2 g/m2 of the diatomaceous earth (DE) DEBBM-P/WP and to 0, 3, 4, 5 or 6 g/m2 of the DE Protect-It®. Mortality of all insects increased with increasing exposure interval; dry dusts were more effective than slurries, and overall mortality was greater for DEBBM-P/WP than Protect-It®. 相似文献