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11.
In this endeavor, a new multiple‐input‐multiple‐output antenna with a sharp rejection at wireless local area network (WLAN) band is designed and practically examined for portable wireless ultra‐wideband applications. The intended diversity antenna possess a small size of 15 mm × 26 mm and two inverted L‐strip are loaded over the conventional rectangular patch antenna to form protrudent‐shaped radiator that acts as a radiating element. The sharp band‐rejection capability at WLAN is established by incising the L‐shaped slits at the decoupling structure. More than ?21 dB isolation is accomplished for the complete working band (ie, 2.87 ‐17 GHz). Degradation in the antenna efficiency at the center frequency of band rejection corroborates the good interference rejection capability. The working capabilities of the intended antenna are tested by using the isolation between the ports, total efficiency, gain, envelope correlation coefficient, radiation pattern, mean effective gain, and total active reflection coefficient. 相似文献
12.
Hernandez Y Nicolosi V Lotya M Blighe FM Sun Z De S McGovern IT Holland B Byrne M Gun'Ko YK Boland JJ Niraj P Duesberg G Krishnamurthy S Goodhue R Hutchison J Scardaci V Ferrari AC Coleman JN 《Nature nanotechnology》2008,3(9):563-568
Fully exploiting the properties of graphene will require a method for the mass production of this remarkable material. Two main routes are possible: large-scale growth or large-scale exfoliation. Here, we demonstrate graphene dispersions with concentrations up to approximately 0.01 mg ml(-1), produced by dispersion and exfoliation of graphite in organic solvents such as N-methyl-pyrrolidone. This is possible because the energy required to exfoliate graphene is balanced by the solvent-graphene interaction for solvents whose surface energies match that of graphene. We confirm the presence of individual graphene sheets by Raman spectroscopy, transmission electron microscopy and electron diffraction. Our method results in a monolayer yield of approximately 1 wt%, which could potentially be improved to 7-12 wt% with further processing. The absence of defects or oxides is confirmed by X-ray photoelectron, infrared and Raman spectroscopies. We are able to produce semi-transparent conducting films and conducting composites. Solution processing of graphene opens up a range of potential large-area applications, from device and sensor fabrication to liquid-phase chemistry. 相似文献
13.
Investigations on the Behavior of HVOF and Cold Sprayed Ni-20Cr Coating on T22 Boiler Steel in Actual Boiler Environment 总被引:1,自引:0,他引:1
Niraj Bala Harpreet Singh Satya Prakash J. Karthikeyan 《Journal of Thermal Spray Technology》2012,21(1):144-158
High temperature corrosion accompanied by erosion is a severe problem, which may result in premature failure of the boiler
tubes. One countermeasure to overcome this problem is the use of thermal spray protective coatings. In the current investigation
high velocity oxy-fuel (HVOF) and cold spray processes have been used to deposit commercial Ni-20Cr powder on T22 boiler steel.
To evaluate the performance of the coatings in actual conditions the bare as well as the coated steels were subjected to cyclic
exposures, in the superheater zone of a coal fired boiler for 15 cycles. The weight change and thickness loss data were used
to establish kinetics of the erosion-corrosion. X-ray diffraction, surface and cross-sectional field emission scanning electron
microscope/energy dispersive spectroscopy (FE-SEM/EDS) and x-ray mapping techniques were used to analyse the as-sprayed and
corroded specimens. The HVOF sprayed coating performed better than its cold sprayed counterpart in actual boiler environment. 相似文献
14.
Imprinted silver nanovoid arrays are investigated via angle-resolved reflectometry to demonstrate their suitability for plasmonic light trapping. Both wavelength-?and subwavelength-scale nanovoids are imprinted into standard solar cell architectures to achieve nanostructured metallic electrodes which provide enhanced absorption for improving solar cell performance. The technique is versatile, low-cost and scalable and can be applied to a wide range of organic semiconductors. Absorption features which are independent of incident polarization and weakly dependent on incident angle reveal localized plasmonic modes at the structured interface. Metallic nanostructure-PCPDTBT:PCBM samples demonstrate absorption enhancements of up to 40%. The structured interface provides light trapping, which boosts absorption at wavelengths where the semiconductors absorb poorly. 相似文献
15.
In the current investigation, Cr2O3–50% Al2O3 coating was deposited on ASTM-SA213-T-22 boiler steel and Fe-based superalloy Superfer 800H by D-gun spray process. The high-temperature corrosion performance of the coated as well as bare alloys was evaluated in Na2SO4–60%V2O5 molten salt, an aggressive environment at 900 °C under cyclic conditions. The kinetics of the corrosion were analyzed by the change in weight measurements which were taken after each cycle (i.e., 1-h heating in a tube furnace followed by 20-min cooling in ambient air) for a total period of 50 cycles. The X-ray diffraction and scanning electron microscopy/energy-dispersive X-ray analysis techniques were used for the analysis of corrosion products. During investigations, it was found that both the selected bare alloys have suffered intensive spallation in the form of removal of their oxide scales, which may be attributed to the formation of non-protective Fe2O3-dominated oxide scales, whereas the coated alloys have shown lesser weight gains along with better adhesiveness of the oxide scales with the substrate till the end of the experiment. The oxides of chromium and aluminum were the main phases revealed in the oxide scales of the coated specimens, which are reported to be protective against the hot corrosion. 相似文献
16.
Niraj Chawake Sri Harish Kumar Paleti B. S. Murty Ravi S. Kottada 《Transactions of the Indian Institute of Metals》2013,66(4):419-424
In the present work, nanocrystalline FeAl and FeAl–Al2O3 composite were synthesized by high energy ball milling and subsequent compaction by spark plasma sintering. Microstructural changes during all stages of processing are studied using X-ray analysis. After 20 h of milling, the disordered FeAl and some amount of Fe rich solid solution was obtained in both of these compositions. Subsequent heat treatment results in formation of ordered FeAl. However, disordering of FeAl was observed in both compositions after spark plasma sintering. Nanocrystallinity is retained in both the compositions even after sintering at high temperature of 1,000 °C. Very high hardness of ~575 HV1 and ~600 HV1 was exhibited by FeAl and FeAl–Al2O3 composite. 相似文献
17.
18.
Chandra Sekhar Biswas Vijay Kumar Patel Niraj Kumar Vishwakarma Avnish Kumar Mishra Rajasekhar Bhimireddi RamaNand Rai Biswajit Ray 《应用聚合物科学杂志》2012,125(3):2000-2009
Poly(N-isopropylacrylamide) (PNIPAM) hydrogels were simply prepared by free radical polymerization in different methanol–water mixture. A scanning electron microscopy study revealed that the freeze-dried hydrogels were macroporous. The swelling ratios in water at 20°C of the resulting hydrogels followed the order: X0.43>X0.21>X0.76 ≈ X0.57>X0.31>X0.13>X0.06>X0, where Xm denotes a gel prepared in a methanol–water mixture with m mole fraction of methanol (xm). Below the lower critical solution temperature, the swelling ratio values of all of the hydrogels gradually decreased with the increase in the temperature. The complete collapse of the PNIPAM chain of all the gels occurred at about 38°C, whereas the same was observed at about 35°C for the conventional gel prepared in water. The swelling ratio values of all the PNIPAM gels in the methanol–water mixtures with different xm values at 20°C passed through a minimum in the cononsolvency zone. The deswelling rates of the hydrogels decreased in the following order: X0.43> X0.31> X0.21> X0.57> X0.76 ≈ X0.13> X0.06> X0. The reswelling rates of these hydrogels decreased in the following order: X0> X0.31> X0.06 ≈ X0.13 > X0.76> X0.57> X0.21> X0.43. The release rates of the Tramadol Hydrochloride drug at 37°C from the drug-loaded hydrogels were almost same for all of the hydrogels. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
19.
Pallavi Kulkarni Umaprasana Ojha Xinyu Wei Niraj Gurung Kasyap Seethamraju Rudolf Faust 《应用聚合物科学杂志》2013,130(2):891-897
We investigated thermal and mechanical properties of thermoplastic polyurethanes (TPUs) with the soft segment comprising of both polyisobutylene (PIB) and poly(tetramethylene)oxide (PTMO) diols. Thermal analysis reveals that the hard segment in all the TPUs investigated is completely amorphous. Significant mixing between the hard and soft segments was also observed. By adjusting the ratio between the hard and soft segments, the mechanical properties of these TPUs were tuned over a wide range, which are comparable to conventional polyether‐based TPUs. Constant stress creep and cyclic stress hysteresis analysis suggested a strong dependence of permanent deformation on hard segment content. The melt viscosity correlation with shear rate and shear stress follows a typical non‐Newtonian behavior, showing decrease in shear viscosity with increase in shear rate. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 891‐897, 2013 相似文献
20.
Vijay Kumar Patel Niraj Kumar Vishwakarma Avnish Kumar Mishra Chandra Sekhar Biswas Pralay Maiti Biswajit Ray 《应用聚合物科学杂志》2013,127(6):4305-4317
Two new alkyne‐terminated xanthate reversible addition‐fragmentation chain‐transfer (RAFT) agents: (S)‐2‐(Propynyl propionate)‐(O‐ethyl xanthate) (X3) and (S)‐2‐(Propynyl isobutyrate)‐(O‐ethyl xanthate) (X4) were synthesized and characterized and used for the controlled radical polymerization of N‐vinylpyrrolidone (NVP). X3 showed better chain transfer ability in the polymerization at 60°C. Molecular weight of the resulted polymer increased linearly with the increase in monomer loading. Kinetics study with X3 showed the pseudo‐first order kinetics up to 67% monomer conversion. Molecular weight (Mn) of the resulting polymer increased linearly with the increase in the monomer conversion up to around 67%. With the increase in the monomer conversion, polydispersity of the corresponding poly(NVP)s initially decreased from 1.34 to 1.32 and then increased gradually to 1.58. Chain‐end analysis of the resulting polymer by 1H‐NMR and FTIR showed clearly that polymerization started with radical forming out of xanthate RAFT agent. Living nature of the polymerization was also confirmed from the successful homo‐chain extension experiment and the hetero‐chain extension experiment involving synthesis of poly(NVP)‐b‐polystyrene amphiphilic diblock copolymer. Formed alkyne‐terminated poly(NVP) also allowed easy conjugation to azide‐terminated polystyrene by click chemistry to prepare well‐defined poly(NVP)‐b‐polystyrene block copolymers. Resulting polymers were characterized by GPC, 1H‐NMR, FTIR, and thermal study. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献