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71.
Joseph G. Atkinson Burton K. Wasson José J. Fuentes Yves Girard C.Stanley Rooney Edward L. Engelhardt 《Tetrahedron letters》1979,20(31):2857-2860
2-Nitroaryl triflates undergo efficient base-catalyzed nucleophilic displacement by dimethyl malonate anion to yield dimethyl nitroarylmalonates, which subsequently are converted in high yields to nitroarylacetic acids and oxindoles. 相似文献
72.
The chiral axis in the title glycine derivative has allowed its resolution into enantiomers: the barrier Δ G≠ for racemisation (rotation around the bond) is 26.2 Kcal mol?1. 相似文献
73.
Rate constants for the gas phase reactions of O3 and OH radicals with 1,3-cycloheptadiene, 1,3,5-cycloheptatriene, and cis- and trans-1,3,5-hexatriene and also of O3 with cis-2,trans-4-hexadiene and trans -2,trans -4-hexadiene have been determined at 294 ± 2 K. The rate constants determined for reaction with O3 were (in cm3 molecule-1s?1 units): 1,3-cycloheptadiene, (1.56 ± 0.21) × 10-16; 1,3,5-cycloheptatriene, (5.39 ± 0.78) × 10?17; 1,3,5-hexatriene, (2.62 ± 0.34) × 10?17; cis?2,trans-4-hexadiene, (3.14 ± 0.34) × 10?16; and trans ?2, trans -4-hexadiene, (3.74 ± 0.61) × 10?16; with the cis- and trans-1,3,5-hexatriene isomers reacting with essentially identical rate constants. The rate constants determined for reaction with OH radicals were (in cm3 molecule?1 s?1 units): 1,3-cycloheptadiene, (1.31 ± 0.04) × 10?10; 1,3,5-cycloheptatriene, (9.12 × 0.23) × 10?11; cis-1,3,5-hexatriene, (1.04 ± 0.07) × 10?10; and trans 1,3,5-hexatriene, (1.04 ± 0.17) × 10?10. These data, which are the first reported values for these di- and tri-alkenes, are discussed in the context of previously determined O3 and OH radical rate constants for alkenes and cycloalkenes. 相似文献
74.
The homogeneous gas-phase reaction of N2H4 with O3 in air atmospheric pressure has been used to generate OH radicals in the dark, allowing the determination of relative OH radical rate constants for compounds which photolyze rapidly. This technique was first validated by determining the OH radical rate constant ratios for n-butane/cyclohexane and methanol/dimethyl ether, both of which are in excellent agreement with the literature values. The rate constant for the reaction of OH radicals with methyl nitrite at 300 ± 3 K was then determined relative to those for the reaction of OH radicals with n-hexane and dimethyl ether. The resulting rate constant of 1.8 × 10?13 cm3/molecule·s is about seven times lower than those of previous measurements which employed a different nonphotolytic relative rate method. 相似文献
75.
James N. Pitts Eugenio Sanhueza Roger Atkinson William P. L. Carter Arthur M. Winer Geoffrey W. Harris Christopher N. Plum 《国际化学动力学杂志》1984,16(7):919-939
The formation of nitrous acid (HONO) in the dark from initial concentrations of NO2 of 0.1–20 ppm in air, and the concurrent disappearance of NO2, were monitored quantitatively by UV differential optical absorption spectroscopy in two different environmental chambers of ca.4300- and 5800-L volume (both with surface/volume ratios of 3.4 m?1). In these environmental chambers the initial HONO formation rate was first order in the NO2 concentration and increased with the water vapor concentration. However, the HONO formation rate was independent of the NO concentration and relatively insensitive to temperature. The initial pseudo-first-order consumption rate of NO2 was (2.8 ± 1.2) × 10?4 min?1 in the 5800-L Teflon-coated evacuable chamber and (1.6 ± 0.5) × 10?4 min?1 in a 4300-L all-Teflon reaction chamber at ca.300 K and ca.50% RH. The initial HONO yields were ca.40–50% of the NO2 reacted in the evacuable chamber and ca.10–30% in the all-Teflon chamber. Nitric oxide formation was observed during the later stages of the reaction in the evacuable chamber, but ca.50% of the nitrogen could not be accounted for, and gas phase HNO3 was not detected. The implications of these data concerning radical sources in environmental chamber irradiations of NOx? organic-air mixtures, and of HONO formation in polluted atmospheres, are discussed. 相似文献
76.
Correlation analysis of the physiological factors controlling fundamental voice frequency 总被引:1,自引:0,他引:1
J E Atkinson 《The Journal of the Acoustical Society of America》1978,63(1):211-222
A technique has been developed to obtain a quantitative measure of correlation between electromyographic (EMG) activity of various laryngeal muscles, subglottal air pressure, and the fundamental frequency of vibration of the vocal folds (Fo). Data were collected and analyzed on one subject, a native speaker of American English. The results show that an analysis of this type can provide a useful measure of correlation between the physiological and acoustical events in speech and, furthermore, can yield detailed insights into the organization and nature of the speech production process. In particular, based on these results, a model is suggested of Fo control involving laryngeal state functions that seems to agree with present knowledge of laryngeal control and experimental evidence. 相似文献
77.
78.
T. Shigematsu S. Staniek R. A. Brand W. Keune R. H. Nussbaum H. -D. Pfannes D. Liljequist G. Longworth R. Atkinson 《Hyperfine Interactions》1983,15(1-4):383-386
The DCEMS technique has been applied to observe drastic changes with time of the ion-implanted57Fe concentration profilein a Cu foil. Spectral changes observed at selected electron energies may be related to changes as a function of depth in the57Fe local surroundings. 相似文献
79.
80.