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31.
Derek F. Laine 《Microchemical Journal》2009,91(1):78-268
A new concept for the electrochemical detection of hydrogen peroxide, and organic hydroperoxides is presented. One advantage of the significance of this technique is that it does not require chemical modification of the electrode or addition of enzymes. Direct electro-reduction of the peroxides was not observed on the carbon disk electrode as it is a kinetically slow process. Redox cycling of the iron complex is apparent as FeIIEDTA rapidly reduces the O-O bond of the peroxides (Fenton Reaction) upon its production by the kinetically facile electro-reduction of FeIIIEDTA. This provides an enhanced and steady-state reductive current as observed by cyclic voltammetry. These features are indicative of the electrocatalytic (EC′) mechanism. A calibration curve was constructed based on the chronoamperometric response at 32 s and a detection limit for H2O2 and t-butyl hydroperoxide was calculated to be 0.4 μM and 20 µM, respectively. This difference is attributable to the rate in which the iron(II) complex reduces the O-O bond, H2O2 (2.3 × 105 M− 1 s− 1) being faster than for the organic peroxide (5.1 × 104 M− 1 s− 1). The FeIIEDTA complex was observed to be unreactive toward dialkyl peroxides. This method may find use in the detection of peroxide-based explosives or in enzymatic assays as it is rapid, simple, inexpensive and should prove to be robust. 相似文献
32.
Avoiding Carbothermal Reduction: Distillation of Alkoxysilanes from Biogenic,Green, and Sustainable Sources 下载免费PDF全文
Richard M. Laine Joseph C. Furgal Phi Doan David Pan Vera Popova Xingwen Zhang 《Angewandte Chemie (International ed. in English)》2016,55(3):1065-1069
The direct depolymerization of SiO2 to distillable alkoxysilanes has been explored repeatedly without success for 85 years as an alternative to carbothermal reduction (1900 °C) to Simet, followed by treatment with ROH. We report herein the base‐catalyzed depolymerization of SiO2 with diols to form distillable spirocyclic alkoxysilanes and Si(OEt)4. Thus, 2‐methyl‐2,4‐pentanediol, 2,2,4‐trimethyl‐1,3‐pentanediol, or ethylene glycol (EGH2) react with silica sources, such as rice hull ash, in the presence of NaOH (10 %) to form H2O and distillable spirocyclic alkoxysilanes [bis(2‐methyl‐2,4‐pentanediolato) silicate, bis(2,2,4‐trimethyl‐1,3‐pentanediolato) silicate or Si(eg)2 polymer with 5–98 % conversion, as governed by surface area/crystallinity. Si(eg)2 or bis(2‐methyl‐2,4‐pentanediolato) silicate reacted with EtOH and catalytic acid to give Si(OEt)4 in 60 % yield, thus providing inexpensive routes to high‐purity precipitated or fumed silica and compounds with single Si?C bonds. 相似文献
33.
High and low molecular weight (Mw) carboxymethyl celluloses (CMC) were adsorbed on a well-characterized fiber substrate (long fibers of a commercial bleached birch kraft pulp with the carboxylic acid groups in Na-form) to increase the charge of the fibers in a controlled fashion. The Mw played a role in the utilization of CMCs as a strength additive in paper sheets nearly doubling the tensile strength with the high Mw CMC. Swelling properties of the CMC treated fibers were measured with water retention value (WRV). The WRV increased more with the high Mw CMC. The swelling was further tuned by two highly cationic polyelectrolytes; high Mw poly(diallyldimethyl ammonium chloride) (PDADMAC) and low Mw polybrene (hexadimethrine bromide, [3,6]-ionene). They were chosen because of their known ability to neutralize the anionic charge either exclusively on the surface or in the whole fiber, respectively. Adsorption of PDADMAC could reduce WRV of the CMC pre-treated fibers to the level of the untreated reference, while polybrene adsorbed pulps with 3–10 times more cationic polyelectrolyte deswelled the fibers only slightly more than the surface neutralized fibers. These results indicated surface conformation differences with low and high Mw CMCs. While the conformation did play a role after physical alteration (drying and rewetting) of the fibers, the paper sheets produced from these fibers showed remarkable differences. In extreme cases, the strength of the paper could be retained after drying (low Mw CMC + PDADMAC) or paper, resistant to disintegration, could be achieved (CMC + polybrene). 相似文献
34.
Spatially resolved OSL (SR-OSL) measurements are made with a scanning or imaging system that records luminescence emissions from known sources within a sample. This work is a first step toward the development of an SR-OSL methodology based on the imaging of ultraviolet OSL emissions with an EMCCD camera. We present UV OSL images of natural quartz extracts, OSL/TL/IR images of sandstone, image-based OSL measurements from aluminum oxide grains, and dose recovery experiments on aluminum oxide and Risø calibration quartz. Camera sensitivity and quantitative reproducibility indicate that EMCCD-based OSL dating is feasible. Further experimentation is necessary to adequately define the error sources and measurement limitations of EMCCDs in the OSL regime. 相似文献
35.
Octa(aminophenyl)silsesquioxane as a nanoconstruction site. 总被引:10,自引:0,他引:10
R Tamaki Y Tanaka M Z Asuncion J Choi R M Laine 《Journal of the American Chemical Society》2001,123(49):12416-12417
36.
We consider in this paper the numerical solution of the Falkner-Skan differential equation, modelling under some similarity assumptions the boundary layer equation. We look for the extremal solution of this third order differential equation. The methods we use are basically the Newton method with a shooting process, which is coupled with a continuation method: they allow us to follow the solution arcs which contain regular and turning point solutions. 相似文献
37.
The room temperature oxidation of porous silicon 总被引:1,自引:0,他引:1
The room temperature oxidation of porous silicon was studied using isothermal methods. The oxidation was found to depend on the type of the porous silicon. The microcalorimetric signals from the oxidation of the p+- and n-type porous silicon in dry air were different. In humid air the signals from the oxidation could not be distinguished from the strong signal due to adsorption of water vapour, but when the samples were placed in water similar differences were observed. The reason for differences in reactions is discussed. The oxidation in different liquids was also studied. The signal from reactions in methanol and ethanol were found to be 100 times higher than in water. In FTIR studies the reaction gas produced by reactions between alcohols and the porous silicon, silane (SiH4) was found in the gas. Traces of SiOCH3 and SiOC2H5 groups were also found in FTIR spectra indicating Si---O---CxHy passivation of the surface. 相似文献
38.
39.
40.
Lehto V.-P. Rahkola M. Laine E. Ylianttila L. Hyssalo P. Jokela K. 《Journal of Thermal Analysis and Calorimetry》1998,53(3):685-695
The specific heat capacities (cp) for the brain and muscle equivalent liquids were determined with isothermal heat conduction microcalorimetry (IMC) and differential
scanning calorimetry (DSC). IMC was found to afford an accurate technique to measure cp for solid and liquid samples, when an appropriate reference is employed. The accuracy of obtained cp values was estimated to be better than 0.7% with the equivalent liquids. Intercomparison with a conventional isoperibolic
calorimeter showed an excellent agreement within the estimated uncertainty of the isoperibolic calorimeter (±3%). Additionally,
suitability of different kinds of IMC sample vessels was tested, and the standard electrical calibration procedure of IMC
was evaluated through the determination of cp with and without a reference material.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献