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We apply the master equation and non-linear Fokker-Planck techniques to a model with autocatalysis and (Michaelis-Menten, Langmuir-Hinshelwood) saturation law and the minimal set of reactive steps for a well posed problem is given.  相似文献   
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Monolithic carbon aerogels were obtained by carbonization of organic aerogels prepared by polymerization of resorcinol and formaldehyde under different conditions. Some carbon aerogels obtained were further CO2-activated. Samples were characterized by gas adsorption, scanning electron microscopy, high-resolution transmission electron microscopy, and mechanical tests. Benzene, toluene and xylenes were adsorbed from dry air by using carbon bed columns, obtaining the breakthrough curves. There was no correlation between the amount adsorbed at the breakthrough point and the volume of micropores narrower than 0.7 nm. Conversely, a good linear relationship between the amount adsorbed at the breakthrough point and the total micropore volume up to a mean micropore width of around 1.05 nm was found. In addition, the height of the mass transfer zone decreased with the mean width of the total micropores up to a value of around 1.05-1.10 nm. One of the best adsorbents obtained showed the lowest height of the mass transfer zone and one of the highest amounts adsorbed at the breakthrough point, either per mass or volume unit. However, it had a lower elastic modulus and compressive strength than other monolithic carbon aerogels, although its compressive strength (3 MPa) was still high enough to use it in carbon bed columns. The sample with the best mechanical properties was a poorer adsorbent. Regeneration of the exhausted adsorbents allowed the recovery of the hydrocarbons adsorbed without any appreciable loss of adsorption capacity of the carbon bed.  相似文献   
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The pressure variation of the optical edge of GaS has been measured. The direct exciton has been studied up to 6 kbar at 77 K and the indirect edge up to 40 kbar at 300 K. The exciton is shown to have a coefficient of ?2 ± 0.5 × 10?6eV/bar and the indirect edge of ?ll ± 1.5× 10?6eV/bar. A discussion of the values of the pressure coefficients for direct and indirect transitions in gallium chalcogenides is given.  相似文献   
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The decomposition of D2CO, CH3OD and HCOOH on Pt(110) and of D2CO on Pt(S)-[9(111) × (100)] was studied by molecular beam relaxation spectroscopy. D2CO and CH3OD evolved CO and H2 via a desorption limited sequence of elementary steps. The rate constant for CO desorption from Pt(110) was 6 × 1014exp(? 35.5 kcalgmol · RT) s?1, and from Pt(S)-[9(111) × (100)] it was 1 × 1015 exp(?36.2 kcalgmol·RT) s?1. On Pt(110) the rate constant for hydrogen formation was 100 ± 1exp(?24 kcalgmol·RT) m?2atom · s. On Pt(S)-[9(111) × (100)] two pathways for H2 formation existed with rate constants of 8.7 × 10?2exp( ?24.9 kcalgmol· RT) cm2atom· s and 3.2 × 10?3 exp(?19.5 kcalgmol·RT) cm2atom· s. These pre-exponential factors are in order of magnitude agreement with values typical of hydrogen recombination on other metals. When a small amount of sulfur ( ~ 0.1 ML) was adsorbed on the stepped Pt surface, only one pathway for H2 formation existed due to blockage of stepped sites. A similar result was obtained when a beam of CO was impinged on the surface. Formic acid decomposed via a branched process to form primarily CO2 and H2.  相似文献   
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Lissamine Green B (LGB) was carefully selected as a potential candidate for the development of a new U.S. Environmental Protection Agency (EPA) method that is intended for use at water utilities to determine chlorine dioxide (ClO2) in drinking water. Chlorine dioxide reacts with LGB in aqueous solution to decrease the absorbance of LGB in direct proportion to the ClO2 concentration. LGB was confirmed to have adequate sensitivity, and to suffer less interference than other dyes reported in the literature. The stoichiometry for the reaction between LGB and ClO2 was found not to be 1:1 and is dependent on the LGB concentration. This required calibration of each LGB stock solution and prompted the investigation of alternate means of calibration, which utilized a horseradish peroxidase (HRP)-catalyzed conversion of chlorite ion (ClO2) to ClO2. This approach allowed the simultaneous determination of ClO2 concentration, which is also required each day at water plants that use ClO2. Studies were conducted to characterize and carefully optimize the HRP-conversion of ClO2 to ClO2 in order to yield reaction conditions that could be accomplished in less than 30 min at modest cost, yet meet EPA's sensitivity and robustness requirements for routine monitoring. An assessment of method detection limit, linearity and slope (or sensitivity), precision, and accuracy in finished drinking water matrices indicated that this approach was suitable for publication as EPA Method 327.0.  相似文献   
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