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91.
The reaction kinetics of atomic chlorine with a series of biogenic hydrocarbons, including the two enantiomers of α‐pinene, were studied at 298 K and 1 atm pressure using a relative rate technique. The simultaneous losses of the biogenic of interest and a reference compound, either n‐nonane or n‐butane, were followed using gas chromatography with flame ionization detection as a function of the extent of photolysis of a chlorine atom precursor. Thionyl chloride, trichloroacetyl chloride or in a few trials, acetyl chloride, were photolyzed at 254 nm to generate chlorine atoms, since molecular chlorine reacted in the dark with these organics. The relative rate constants for ethane and isoprene determined relative to n‐butane using SOCl2 and CCl3COCl were compared to those determined using Cl2 to check for possible artifacts. The average relative rate constants for ethane and isoprene (both relative to n‐butane) using these new sources are (0.281 ± 0.021) and (2.49 ± 0.39) (±2 σ) respectively, within experimental error of those measured using Cl2 as the chlorine atom source. The relative rate constants averaged over all sources including Cl2 are (0.277 ± 0.025) for ethane and (2.42 ± 0.45) for isoprene. The ratios of rate constants for the chlorine atom reactions with the biogenics with formula C10H16 relative to n‐nonane were as follows: (R)‐α‐pinene (0.991 ± 0.264); (S)‐α‐pinene (0.946 ± 0.240); β‐pinene (1.09 ± 0.30); (R)‐limonene (1.33 ± 0.15); myrcene (1.36 ± 0.31); 3‐carene (1.16 ± 0.23). That for p‐cymene, C10H14, is (0.433 ± 0.072). Taking k(Cl + n‐nonane) = (4.82 ± 0.14) × 10−10 cm3 molecule−1 s−1, the absolute rate constants (in units of 10−10 cm3 molecule−1 s−1) are: (R)‐α‐pinene (4.8 ± 1.3); (S)‐α‐pinene (4.6 ± 1.2); β‐pinene (5.3 ± 1.5); limonene (6.4 ± 0.8); myrcene (6.6 ± 1.5); 3‐carene (5.6 ± 1.3); p‐cymene (2.1 ± 0.4). (All errors are ± 2 σ). Although abstraction was not measured directly in this study, it is likely a significant contributor to the overall reactions of the C10H16 biogenics. The rate constant for the reaction of the aromatic compound p‐cymene is within experimental error of that predicted from the sum of reaction with toluene plus the isopropyl substituent. A limited number of experiments for methyl vinyl ketone in N2 using CCl3COCl as the chlorine atom source and nonane as the reference compound gave a relative rate constant of (0.422 ± 0.034), corresponding to an absolute rate constant of (2.0 ± 0.2) × 10−10 cm3 molecule−1 s−1. Based on these rate constants, the lifetimes of these biogenics at dawn with respect to reaction with chlorine atoms are expected to be comparable to reaction with OH. Thus, loss of these biogenics by reaction with atomic chlorine must be taken into account in coastal regions in addition to their reactions with OH, O3 and at night, NO3. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 491–499, 1999 相似文献
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Steven Bloom Desta Doro Bume Cody Ross Pitts Prof. Dr. Thomas Lectka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):8060-8063
To expand upon the recent pioneering reports of catalyzed sp3 C?H fluorination methods, the next rational step is to focus on directing “radical‐based fluorination” more effectively. One potential solution entails selective C?C bond activation as a prelude to selective fluorination. Herein, we report the tandem photocatalyzed ring‐opening/fluorination reactions of cyclopropanols by 1,2,4,5‐tetracyanobenzene (TCB) and Selectfluor to afford a process tantamount to site‐selective β‐fluorination of carbonyl‐containing compounds. This new approach provides a synthetically mild and operationally simple route to otherwise difficult‐to‐prepare β‐fluorinated products in good yields and with good‐to‐excellent regioselectivity. Remarkably, substrates that contain other usually reactive (e.g., benzylic) sites undergo ring‐opening fluorination preferably. The versatility of this method to give cyclic β‐fluorides from tertiary cyclopropanols and γ‐fluoro alcohols is also highlighted. 相似文献
95.
Schief WK; Rogers C; Murugesh S 《The Quarterly Journal of Mechanics and Applied Mathematics》2007,60(1):49-64
Evolution of foliations of the plane is shown, under a conditionof constant divergence, to be linked to the scattering problemfor the integrable modified Kortewegde Vries hierarchy.This result is applied to a set of kinematic relations whicharise in the theory of ideal fibre-reinforced fluids. In particular,it is established that the fibres, which are convected withthe fluid, constitute generalized tractrices. 相似文献
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Roger Atkinson William P. L. Carter Christopher N. Plum Arthur M. Winer James N. Pitts 《国际化学动力学杂志》1984,16(7):887-898
Rate constants have been determined at 296 ± 2 K for the gas phase reaction of NO3 radicals with a series of aromatics using a relative rate technique. The rate constants obtained (in cm3 molecule?1 s?1 units) were: benzene, <2.3 × 10?17; toluene, (1.8 ± 1.0) × 10?17; o? xylene, (1.1 ± 0.5) × 10?16; m? xylene, (7.1 ± 3.4) × 10?17; p? xylene, (1.4 ± 0.6) × 10?16; 1,2,3-trimethylbenzene, (5,6 ± 2.6) × 10?16; 1,2,4-trimethylbenzene (5.4 - 2.5) × 10?16; 1,3,5-trimethylbenzene, (2.4 ± 1.1) × 10?16; phenol, (2.1 ± 0.5) × 10?12; methoxybenzene, (5.0 ± 2.8) × 10?17; o-cresol, (1.20 ± 0.34) × 10?11; m-cresol, (9.2 ± 2.4) × 10?12; p-cresol, (1.27 ± 0.36) × 10?11; and benzaldehyde, (1.13 ± 0.25) × 10?15. These kinetic data, together with, in the case of phenol, product data, suggest that these reactions proceed via H-atom abstraction from the substituent groups. The magnitude of the rate constants for the hydroxy-substituted aromatics indicates that the nighttime reaction of NO3 radicals with these aromatics can be an important loss process for both NO3 radicals and these organics, as well as being a possible source of nitric acid, a key component of acid deposition. 相似文献
98.
At certain magnetic fields, intensity changes have been observed in the phosphorescence of 1,2,4,5-tetrachlorobenzene (TCB) doped in a single crystal oFollowing the application of a magnetic field of the proper magnitude and direction to induce CR, the phosphorescence intensity of TCB displays an obse 相似文献
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