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71.
On pulse radiolysis of N2O saturated aqueous solutions of atropine, an optical absorption band (max at 320 nm,e=2.81·103 dm3·mol–1·cm–1) was observed, which is assigned to the product of reaction of OH radicals with the solute. This absorption decayed following second order kinetics with a rate constant of 4.5·108 dm3·mol–1·s–1. The rate constant for the reaction of OH radicals with atropine as estimated by following the build-up kinetics is 2.7·109 dm3·mol–1·s–1. The H atoms also reacted with this compound to produce a transient absorption band behaving similarly to the one observed in the case of reaction with OH radicals. The transient species formed in both cases is assigned to a radical derived by H atom abstraction by H/OH radicals from the parent compound. This radical was unreactive towards 2-mercaptoethanol. e
aq
–
was found to react with atropine forming a transient band with max at 310 nm (=3.55·103 dm3·mol–1). Its decay was also second order with a rate constant of 1.64·109 dm3·mol–1·s–1. The bimolecular rate constant for the reaction of e
aq
–
with atropine as estimated from the decay of e
aq
–
absorption at 720 nm is 3.9·109 dm3·mol–1·s–1. Specific one-electron oxidizing and reducing agents (such as Cl
2
–
, Tl2+, SO
4
–
and (CH3)2COH, CO
2
–
, respectively) failed to oxidize or reduce this compound in aqoues solutions. The radical anion of atropine formed by its reaction with e
aq
–
was found to reduce thionine and methyl viologen with bimolecular rate constant of 3.8·109 and 3.2·109 dm3·mol–1·s–1, respectively. 相似文献
72.
Gamma irradiation of aerated aqueous solutions of ammonia leads to the formation of nitrite as a radiolytic product. Its yield increases with increasing concentration of NH3 as well as O2. OH radicals react with NH3 to give NH2 radicals, which in the presence of O2 form NH2O2 radicals. These radicals finally lead to the formation of nitrite. G(NO2−) decreases with increasing radiation dose due to secondary reactions. Its initial yield, however, is more than 1/2GOH, while hydrogen peroxide yield is less than the expected value viz. G(H2O2) + 1/2G(eaq−), indicating its participation in reactions with radiation produced free radicals. G(H2) is 0.35 in aerated aqueous solutions of 10−3 mol dm−3 NH3 and 0.23 in the absence of oxygen. Implications of these results to the use of NH3 in primary coolant water of pressurized water nuclear power reactors of the VVER type are discussed. 相似文献
73.
Nature of the transient species formed during pulse radiolysis of thioacetamide in aqueous solutions
K. Kishore P. Dwibedy G. R. Dey D. B. Naik P. N. Moorthy 《Research on Chemical Intermediates》1998,24(1):35-45
Thioacetamide (TA) is an organic compound having thioamide group similar to that in thiourea derivatives. Its reactions with
eaq−, H-atom and OH radicals were studied using the pulse radiolysis technique at various pHs and the kinetic and spectral characteristics
of the transient species were determined. The initial adduct formed by the reaction of TA with OH radicals at pH 7 does not
absorb light in the 300–600 nm region but reacts with the parent compound to give a transient species with an absorption maximum
around 400 nm. At pH 0, the reaction of OH radicals with TA directly gives a similar transient species with absorption maximum
at 400 nm. Transient species formed by H-atom reaction with TA and pH 0 has no absorption in the 300–600 nm region but at
higher acidity a new transient species is formed which has absorption maximum at 400 nm. This transient absorption observed
in the case of both OH and H atom reaction with TA is ascribed to the formation of a resonance stabilized radical similar
to that obtained in the case of thiourea derivatives. The species produced by electron reaction viz. electron adduct was found to be a strong reductant and could reduce MV2+ with a high rate constant. H2S was produced as a stable product in the reaction of eaq− and its G-value was determined to be about 0.8. 相似文献
74.
One-electron oxidation of thionine has been studied using specific oxidizing radicals such as Cl−Tl(II) and N3 generated by pulse radiolysis of aqueous solutions. The semioxidized thionine exhibited threepK’s indicating four conjugate acid-base forms. N3 radicals were found to be less efficient in oxidizing thionine as compared to Cl
2
−
, Tl2+ and Tl(OH)+. The rate constants for electron abstraction from thionine by Cl
2
−
, Tl2+, Tl(OH)+, Tl(OH)2 and N3 were evaluated. The spectra of different protonated forms of semioxidized thionine and the extinction coefficients at λmax are presented. Reaction of OH radicals with thionine gave transient products whose spectra and acid-base properties were
different from those of semioxidized thionine. The rate constant for formation of the product transient agrees well with competition
kinetic value for reaction of OH with thionine reported earlier. 相似文献
75.
Subramanian MK Anbarasan PM Ilangovan V Babu SM 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,71(1):59-67
The gas phase infrared spectrum of 3-aminoacetophenone (3AAP) was measured in the range 5000-500cm(-1) and with a resolution of 0.5cm(-1). The Fourier transform Raman (FT-Raman) and Fourier transform infrared (FT-IR) spectra of 3AAP were recorded in the solid phase. Geometry optimizations were done without any constraint and several thermodynamic parameters were calculated for the minimum energy conformer at ab initio and density functional theory (DFT) levels invoking 6-311G(2df 2p) basis set and the results are compared with the experimental values. Harmonic-vibrational wavenumber was also calculated for the minimum energy conformer at ab initio and DFT levels using 6-31G(d,p) basis set and the results are compared with related molecules. With the help of specific scaling procedures, the observed vibrational wavenumbers in gas phase, FT-IR and FT-Raman spectra were analyzed and assigned to different normal modes of the molecule. Most of the modes have wavenumbers in the expected range, the error obtained was in general very low. The appropriate theoretical spectrogram for the FT-IR spectra of the title molecule is also constructed. 相似文献
76.
A new rhodamine-based reversible chemosensor (L1 ) is reported, which could bind Hg2+ and Cu2+ in aqueous methanol solution with detectable change in color. Cu2+ and Hg2+ ions responded differently toward the fluorescence output signals on binding to L1.L1 could also be used as a selective probe for monitoring Hg2+ adsorbed on bacteria using an optical microscope. 相似文献
77.
Both aliphatic and aromatic nitriles are conveniently and selectively converted in a single step, via an indirect acid-catalyzed hydration, into the corresponding amides in 1-8 h using a TFA-H2SO4 mixture as a reagent system. Although the same reagent did not work for the sterically hindered nitriles such as mesitonitrile, the transformation could be accomplished by changing TFA to AcOH at higher temperatures (>90 degrees C). 相似文献
78.
V. G. Thomas S. B. Srivastava P. N. Moorthy 《Journal of Radioanalytical and Nuclear Chemistry》1989,136(6):443-447
Using the pulse radiolysis competition kinetic technique, OH radical rate constants with 12 metal DTPA complexes were determined in neutral aerated aqueous solutions. They are in the range of /1.3–5.9/×109 dm3 mol–1s–1. To a first approximation, the rate constant was found to decrease linearly with an increase in the field strength of the metal ion (q/r2). 相似文献
79.
Manchuri Krishna Moorthy Shaik Mahammad Ali Gopireddy Venkata Subba Reddy 《Biomedical chromatography : BMC》2022,36(4):e5336
The foremost objective of the present study was to develop and validate a new LC–QTOF–MS/MS method for the identification and quantitative determination of 4,6-dichloro-5-nitro-2-(propylthio)pyrimidine (DPP) genotoxic impurity through the derivatization process in ticagrelor active pharmaceutical ingredient (API). Owing to the low response of DPP at the specification level, DPP was converted to 4,6-dibenzylamino-5-nitro-2-(propylthio)pyrimidine (DPP derivative) by addition of benzyl amine, then analyzed using mass spectrometry with a time-of-flight analyzer, and good separation was accomplished under the experimental conditions described. The effective separation of DPP derivative was achieved using an Acquity UPLC BEH C18 reverse-phase column (100 × 4.6 mm × 1.7 μm) with an isocratic program with mobile phase A as 0.1% formic acid in milli Q water and mobile phase B as acetonitrile in the ratio of 20:80 v/v. The flow rate was maintained as 0.4 ml/min, the injection volume was 2 μl, the autosampler temperature was 5°C, the column oven temperature was ambient and the run time was 6.0 min. The diluent used was 0.2% benzyl amine in water and acetonitrile in the ratio of 30:70 v/v. The retention time of the DPP derivative was 2.87 min. The limit of detection and limit of quantification were 0.03 and 0.08 ppm, respectively. The DPP derivative was linear from 1.68 to 12.78 ppm with R2 of 0.9958. Thus, the developed method is valid for the identification and quantitative determination of DPP derivative in ticagrelor API. 相似文献
80.
A new coumarin-based sensor molecule (L1) has been synthesized and this was found to bind calcium and magnesium ions more effectively as compared to other alkali/alkaline earth/lanthanide and certain transition metal ions. A significant enhancement in fluorescence intensity was observed on binding to Ca2+ and Mg2+ ions; while a minor quenching was observed for weakly bound Hg2+, Ni2+, Fe3+, and Co2+ ions. PET process, coupled with the ICT process, is proposed to explain the observed spectral response. 相似文献