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991.
The polycrystalline sample of KBa2V5O15 ceramics was prepared by a mixed oxide method at low temperature (i.e., at 560 °C). The formation of the compound was confirmed using an X-ray diffraction technique at room temperature. Scanning electron micrograph of the material showed uniform grain distribution on the surface of the sample. Detailed studies of dielectric properties of the compound as a function of temperature at different frequencies suggest that the compound has a dielectric anomaly of ferroelectric to paraelectric type at 323 °C, and exhibits diffuse phase transition. Electrical properties of the material were analyzed using a complex impedance technique. The Nyquists plot showed the presence of both grain (>103 Hz) and the grain boundary (<103 Hz) effects in the material. Studies of electrical conductivity over a wide temperature range suggest that the compound exhibits the negative temperature coefficient of resistance behavior. The ac conductivity spectrum was found to obey Jonscher's universal power law. 相似文献
992.
Biofiltration and kinetic aspects of a biotrickling filter for the removal of paint solvent mixture laden air stream 总被引:10,自引:0,他引:10
In the present study, removal of methyl ethyl ketone (MEK), toluene, n-butyl acetate and o-xylene (MTBX) emitted from the paint industry was carried out in a coal based biotrickling filter. When the influent MTBX loadings were less than 120 gm(-3)h(-1), nearly 100% removal could be achieved. A maximum elimination capacity of 184.86 gm(-3)h(-1) was obtained at a MTBX load of 278.27 gm(-3)h(-1) with an empty bed residence time of 42.4s in phase V. Results showed that the condition was the most favorable for n-butyl acetate degradation followed by MEK, toluene and then o-xylene. The corresponding maximum removal rate, r(max) values of MTBX were calculated as 0.085, 0.033, 0.16 and 0.024 gm(-3)h(-1), respectively. Standard deviation of error in prediction of MEK, toluene and o-xylene removal were within limit of 10%, while in the case of n-butyl acetate this was approximately 60%. The MTBX concentration profiles along the depth were also determined by using convection-diffusion reaction (CDR) model. It was observed that at low concentration and low flow rate, the model is in good agreement with the experimental values for MEK, toluene and n-butyl acetate, but for o-xylene the model results deviated from the experimental. 相似文献
993.
A phase-transited, nondisintegrating, controlled release, asymmetric membrane capsular system for poorly water-soluble model drug flurbiprofen was developed and evaluated both in vitro and in vivo for osmotic and controlled release of the drug. Asymmetric membrane capsules (AMCs) were prepared using fabricated glass mold pins through wet phase inversion process. Effect of varying osmotic pressure of the dissolution medium on drug release was studied. Membrane characterization by scanning electron microscopy showed an outer dense region with less pores and an inner porous region for the prepared asymmetric membrane. In vitro release studies for all the prepared formulations were carried out (n = 6). Statistical test was applied for in vitro drug release at p > .05. Predicted in vivo concentration from in vitro release data closely matched the minimum effective concentration (in vivo) level achieved by the drug from its release through phase-transited AMC in rabbits for the first hour. The drug release was found to be independent of the pH but dependent on the osmotic pressure of the dissolution medium. In vivo pharmacokinetic studies showed level A correlation (R(2) > .99) with 42.84% relative bioavailability compared to immediate release tablet of flurbiprofen. Excellent correlation achieved suggested that the in vivo performance of the AMCs could be accurately predicted from their in vitro release profile. 相似文献
994.
Carbon nanofiber (CNF) is one of the stiffest materials produced commercially, having excellent mechanical, electrical, and
thermal properties. The reinforcement of rubbery matrices by CNFs was studied in the case of ethylene vinyl acetate (EVA).
The tensile strength was greatly (61%) increased, even for very low fiber content (i.e., 1.0 wt.%). The surface modification
of the fiber by high energy electron beam and gamma irradiation led to better dispersion in the rubber matrix. This in turn
gave rise to further improvements in mechanical and dynamic mechanical properties of EVA. The thermal conductivity also exhibited
improvements from that of the neat elastomer, although thermal stability of the nanocomposites was not significantly altered
by the functionalization of CNFs. Various results were well supported by the morphological analysis of the nanocomposites. 相似文献
995.
Ha Heon Phil Maddigapu Pratap Reddy Pullur Anil Kumar Lee Kyung Ju Jung Soon Hyo 《Applied catalysis. B, Environmental》2008,78(3-4):301-308
To get the low temperature sulfur resistant V2O5/TiO2 catalysts quantum chemical calculation study was carried out. After selecting suitable promoters (Se, Sb, Cu, S, B, Bi, Pb and P), respective metal promoted V2O5/TiO2 catalysts were prepared by impregnation method and characterized by X-ray diffraction (XRD) and Brunner Emmett Teller surface area (BET-SA). Se, Sb, Cu, S promoted V2O5/TiO2 catalysts showed high catalytic activity for NH3 selective catalytic reduction (NH3-SCR) of NOx carried at temperatures between 150 and 400 °C. The conversion efficiency followed in the order of Se > Sb > S > V2O5/TiO2 > Cu but Se was excluded because of its high vapor pressure. An optimal 2 wt% ‘Sb’ loading was found over V2O5/TiO2 for maximum NOx conversion, which also showed high resistance to SO2 in presence of water when compared to other metal promoters. In situ electrical conductivity measurement was carried out for Sb(2%)/V2O5/TiO2 and compared with commercial W(10%)V2O5/TiO2 catalyst. High electrical conductivity difference (ΔG) for Sb(2%)/V2O5/TiO2 catalyst with temperature was observed. SO2 deactivation experiments were carried out for Sb(2%)/V2O5/TiO2 and W(10%)/V2O5/TiO2 at a temperature of 230 °C for 90 h, resulted Sb(2%)/V2O5/TiO2 was efficient catalyst. BET-SA, X-ray photoelectron spectroscopy (XPS) and carbon, hydrogen, nitrogen and sulfur (CHNS) elemental analysis of spent catalysts well proved the presence of high ammonium sulfate salts over W(10%)/V2O5/TiO2 than Sb(2%)/V2O5/TiO2 catalyst. 相似文献
996.
Endosulfan, one of the most widely used pesticides in various sectors including agriculture, has been reported posing a threat to the ecology as well as to the environment. Contamination of groundwater and surface water sources with various pesticides is well documented, and this problem is prominent, particularly in rural areas. In the present study, efforts are made to remove endosulfan from water using wood charcoal, a local and low cost adsorbent. It gave removal efficiency of more than 90%. Equilibrium time was found to be around 5?h. Wood charcoal showed an uptake capacity of 0.53?mg/g with initial endosulfan concentration in the range of 0.25–5?mg/L and 1.77?mg/g for the range of 2–50?mg/L. Langmuir isotherm gave a better prediction of adsorption capacity than the Freundlich. The Langmuir isotherm fit also gave a better correlation with the experimental data. In the desorption study carried out, 10% solutions of acetone, methanol, acetic acid, saturated EDTA solution, and distilled water were used as eluents. Ten percent methanol solution was found performing well with an adsorbent regeneration of more than 80% after four cycles of adsorption desorption. Desorption was found to follow a zero order equation in the case of 10% solutions of both acetone and methanol. 相似文献
997.
Perkas N Amirian G Applerot G Efendiev E Kaganovskii Y Ghule AV Chen BJ Ling YC Gedanken A 《Nanotechnology》2008,19(43):435604
A glass substrate was coated with silver by ultrasound irradiation. The structure and morphology of the nanoparticles in the deposited film were characterized using methods such as XRD, TEM, HR TEM, HRSEM, AFM, TOF-SIMS and optical spectroscopy. It was demonstrated that nucleation and the ensuing growth of the nanoparticles occurs in solution and is influenced by the concentration of the precursor, temperature and time of sonication. TOF-SIMS measurements revealed that silver nanoparticles passed through the glass interface and diffused within the glass substrate up to ~60?nm. An analysis of the thermal effects accompanying the sonochemical cavitation of micro-bubbles in the solution near the solid surfaces shows that the collision of nanoparticles can lead to their melting and coalescence. Sonochemical deposition takes place layer by layer, so that the completion of the deposition of each layer of nanoparticles is followed by the sintering of adjacent particles and the formation of a close-packed layer. Using PVP as a stabilizing agent, a monolayer coating of silver nanoparticles on the glass surface was obtained. The coated glass demonstrated antibacterial activity. 相似文献
998.
Anil D. Garje Rohini C. Aiyer 《Journal of Materials Science: Materials in Electronics》2008,19(6):547-552
Synthesized nanophase SnO2 powder was used as a functional material along with optimized 15 wt% of glass, fired at 550 °C for better adhesion, to fabricate
thick films using screen printing on alumina substrate. Their surface was modified by dip coating in platinum chloride solution
(PtCl2) of different molarities (0.05–0.2 M). A subsequent thermal treatment to these thick films was carried out at an optimized
temperature of 750 °C in air atmosphere. The films were tested for 400 ppm concentration of H2, CO and LPG. Sensors dip coated with 0.15 M solution of PtCl2 show the highest sensitivity towards the test gases which is ten times higher than undoped SnO2 sensors.XRD, EDX and SEM measurements showed that the behavior could be associated with the spatial distribution of the platinum
within the tin oxide film. The sensors have fast response time of 10 s to all the three gases with a minimum detection limit
of 10 ppm. 相似文献
999.
Gupta S Maiti P Krishnamoorthy K Krishnamurthy R Menon A Bhowmick AK 《Journal of nanoscience and nanotechnology》2008,8(4):2114-2126
Reinforcement of a novel poly(phenylene ether) (PPE) based thermoplastic elastomer (TPE), i.e., styrene-ethylene-butylene-styrene (SEBS)/ethylene vinyl acetate (EVA) and PPE-polystyrene (PS), was studied to develop a reinforced thermoplastic elastomer or thermoplastic vulcanizate (TPV). An effort was made to reinforce selectively the elastomeric dispersed phase of EVA by silica nanoparticles and silica sol-gel precursors, like alkoxy orthosilanes, using twin-screw extrusion and injection molding processes. Improvement of tensile strength and percent elongation at break was observed both with silica nanoparticles and tetraethoxy orthosilane (TEOS). Addition of TEOS transformed the dispersed EVA lamellar morphology into semispherical domains as a consequence of possible crosslinking. Soxhlet extraction was done on the silica and TEOS reinforced materials. The insoluble residues collected from both the silica and TEOS reinforced samples were analyzed in detail using both morphological and spectroscopic studies. This extensive study also provided an in-depth conceptual understanding of the PPE based TPE behavior upon reinforcement with silica nanoparticles and silica sol-gel precursors and the effect of reinforcement on recycling behavior. 相似文献
1000.