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31.
Optical resolution of new quinolone drugs by capillary electrophoresis with ligand-exchange and host-guest interactions 总被引:3,自引:0,他引:3
A method for the optical resolution of new quinolone drugs (NQs) by capillary electrophoresis has been investigated. The NQs were adequately resolved using a γ-cyclodextrin (γ-CD)-Zn(II)-
-phenylalanine (
-Phe) solution as the running solution. The resolution depended on the components of the running solution and their concentrations. When
-Phe was used instead of
-Phe, inversion of the migration order of the enantiomers was observed. The resolution mechanism is considered to be due to a ligand-exchange interaction of the NQs with Zn(II) and
-Phe, in combination with a host-guest interaction of those with γ-CD. 相似文献
32.
33.
Alkylsulfonates from methanesulfonic acid to decanesulfonic acid were separated by isotachophoresis with conductivity detection in a common electrolyte system at pH 4.8. The electrolyte system consisted of 10 mM HCl buffered with epsilon-aminocaproic acid (pH 4.8) and 0.1% methylhydroxyethylcellulose (MHEC) acting as the leading electrolyte. The terminating electrolyte was 20 mM caproic acid also containing 0.05% MHEC. Current settings of 250 microA for the first and 50 microA for the second capillary were applied. On one hand, the method was applied to the determination of the content of methanesulfonate as the salt forming agent (mesilate) in a recently registered drug substance. The results obtained by ITP were compared with an orthogonal titration method. On the other hand, due to the column-coupling configuration of the electrophoretic instrument, the method could be extended to the trace determination in the ppm range in order to monitor methanesulfonic acid as an impurity in a drug substance. The validation confirmed the linearity of the method between 1 and 10 mg/l, limits of detection and quantification below 1 mg/l, recovery rates from 92.4 to 95.4%, and repeatability with a R.S.D. of 3.8% (six runs with a 4 mg/l spiked sample). Finally, three batches of a newly produced drug substance could be checked for methanesulfonic acid giving results of below 0.0014% (concentration related to the drug substance). 相似文献
34.
Al-Arfaj NA 《Talanta》2004,62(2):255-263
A flow-injection (FI) methodology using (2,2′-dipyridyl) ruthenium(II) [Ru(dipy)32+] chemiluminescence (CL) was developed for the rapid and sensitive determination of metoclopramide hydrochloride. The method is based on the CL reaction of metoclopramide with Ru(dipy)32+ and KMnO4 in a sulfuric acid medium. Under the optimum conditions, a calibration graph was obtained over the concentration range 0.005-3.5 μg ml−1 with a limit of detection (S/N=2) of 1 ng ml−1. The correlation coefficient was 0.99993 (n=8) with a relative standard deviation of 0.48% for 10 determinations of 1 μg ml−1 of drug. The method was successfully applied to the determination of metoclopramide in pharmaceutical preparations and biological fluids after IP administration of 25 mg kg−1 dose to rats. The elimination half-life was 2.5±0.4 h. 相似文献
35.
The L-dopa is the immediate precursor of the neurotransmitter dopamine. Unlike dopamine, L-dopa easily enters the central nervous system and is used in the treatment of Parkinson’s disease. A sensitive and selective method is presented for the voltammetric determination of L-dopa in pharmaceutical formulations using a carbon paste electrode modified with trinuclear ruthenium ammine complex [(NH3)5RuIIIORuIV(NH3)4ORuIII(NH3)5]6+ (Ru-red) incorporated in NaY zeolite. The parameters which influence on the electrode response (paste composition, potential scan rate, pH and interference) were also investigated. The optimum conditions were found to an electrode composition (m/m) of 25% zeolite containing 6.7% Ru, 50% graphite and 25% mineral oil in acetate buffer at pH 4.8. Voltammetric peak currents showed a linear response for L-dopa concentration in the range between 1.2×10−4 and 1.0×10−2 mol l−1 (r=0.9988) with a detection limit of 8.5×10−5 mol l−1. The variation coefficient for a 1.0×10−3 mol l−1 L-dopa (n=10) was 5.5%. The results obtained for L-dopa in pharmaceutical formulations (tablet) was in agreement with compared official method. In conclusion, this study has illustrated that the proposed electrode modified with Ru-red incorporated zeolite is suitable valuable for selective measurements of L-dopa. 相似文献
36.
The electrochemical reduction of fenofibrate at a hanging mercury drop electrode (HMDE) was investigated by cyclic voltammetry, square-wave voltammetry, and chronoamperometry. Different buffer solutions were used over a wide pH range (3.0–10.0). The best definition of the analytical signals was found in borate buffer (pH 9.0)–tetrabutylammonium iodide mixture containing 12.5% (v/v) methanol at –1.2 V (versus Ag/AgCl). According to cyclic voltammetric studies, the reduction was irreversible and diffusion controlled. The diffusion coefficient was 2.38×10–6 cm2 s–1 as determined by chronoamperometry. Under optimized conditions of square-wave voltammetry, a linear relationship was obtained between 0.146–4.96 g mL–1 of fenofibrate with a limit of detection of 0.025 g mL–1. Validation parameters such as sensitivity, accuracy, precision, and recovery were evaluated. The proposed method was applied to the determination of fenofibrate in pharmaceutical formulations. The results were compared with those obtained by a published high-performance liquid chromatography method. No difference was found statistically. 相似文献
37.
Eulogio J. Llorent-Martínez 《Analytica chimica acta》2006,555(1):128-133
A multicommuted flow-through optosensor based on the direct fluorescence measurements of Vitamins B2 and B6 using a non-polar sorbent (C18 silica gel) as solid sensing zone (to accomplish the separation and subsequent preconcentration/detection of the target analytes) have been developed. The proposed flow system was controlled by Java-written home-made software and designed using three-way solenoid valves for independent automated manipulation of sample and carrier solutions. The native fluorescence signal was simultaneously monitored at two pairs of excitation/emission wavelengths (450/519 and 294/395 for B2 and B6, respectively). The separation of the analytes was performed in the detection flow cell, using the differences in the sorption/elution process on the solid support between the two vitamins, due to their different polarity. Using an optimised sampling time, the analytical signal showed linearity in the range 0.01-0.4 and 0.15-3 μg ml−1 with detection limits of 0.003 and 0.045 μg ml−1 for B2 and B6, respectively, obtaining R.S.D. (%) values better than 2% for both analytes. The proposed methodology was applied to different pharmaceutical preparations, obtaining remarkably good results with recoveries ranging from 96 to 107.5%. 相似文献
38.
G.E. Taylor 《Journal of chromatography. A》1997,770(1-2):261-271
A validated ion chromatographic method for the determination of anionic impurities in clodronic acid or disodium clodronate is described. Separations are performed by using an anion-exchange column (IonPac AS5) and a sodium hydroxide gradient. Impurities are detected by suppressed conductivity without the need for derivatisation. The most important variable affecting the separation was shown to be the column temperature. 相似文献
39.
40.
Thierry Dana-Picard Aaron Naiman 《International Journal of Mathematical Education in Science & Technology》2013,44(6):865-877
Geometric constructions have previously been shown that can be interpreted as rays of light trapped either in polygons or in conics, by successive reflections. The same question, trapping light in closed Fermat curves, is addressed here. Numerical methods are used to study the behaviour of the reflection points of a triangle when the degree of the curve varies, including a generalization to non integer powers. 相似文献