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101.
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
102.
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
103.
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105.
Pitts JD Howell AR Taboada R Banerjee I Wang J Goodman SL Campagnola PJ 《Photochemistry and photobiology》2002,76(2):135-144
We report the synthesis and optical characterization of two new photoactivators and demonstrate their use for multiphoton excited three-dimensional free-form fabrication with proteins. These reagents were developed with the goal of cross-linking Type 1 collagen. This cross-linking process produces structures on the micron and submicron size scales. A rose bengal diisopropyl amine derivative combines the classic photoactivator and co-initiator system into one molecule, reducing the reaction kinetics and increasing cross-linking efficiency. This derivative was successful at producing stable structures from collagen, whereas rose bengal alone was not effective. A benzophenone dimer connected by a flexible diamine tether was also synthesized. This activator has two photochemically reactive groups and is highly efficient in cross-linking bovine serum albumin and Type 1 collagen to form stable, robust structures. This approach is more flexible in terms of cross-linking a variety of proteins than by traditional benzophenone photochemistry. The photophysical properties vary greatly from that of benzophenone, with the appearance of a new, lower energy absorption band (lambda max approximately 370 nm in water) and broad, visible emission band (approximately 500 nm maximum). This absorption band is highly solvatochromic, suggesting it arises, at least in part, from a charge transfer interaction. Collagens are typically difficult to cross-link photochemically, and the results here suggest that these two new activators will be suitable for cross-linking other forms of collagen and additional proteins for biomedical applications such as the de novo assembly of biomimetic tissue scaffolds. 相似文献
106.
Paralleling the formal derivation of general relativity as a flat spacetime theory, we introduce in addition a preferred temporal foliation. The physical interpretation of the formalism is considered in the context of 5-dimensional parametrized and 4-dimensional preferred frame contexts. In the former case, we suggest that our earlier proposal of unconcatenated parametrized physics requires that the dependence on be rather slow. In the 4-dimensional case, we consider and tentatively reject several areas of physics that might require a preferred foliation, but find a need for one in the process (flowing) theory of time. We then suggest why such a foliation might reasonably be unobservable. 相似文献
107.
A series of NOx–air irradiations, with trace amounts of propane and propene present to monitor OH radical concentrations, have been carried out in a 5800-L evacuable environmental chamber to investigate radical levels and sources during such irradiations. The data obtained show conclusively that unknown radical sources are present, and that photolysis of initial nitrous acid can be, at best, only a minor source of radicals after ~30–60 min of irradiation. 相似文献
108.
Laser induced fluorescence of C2O is observed following the 266 nm laser photodissociation Of C3O2. Excitation spectra of C2O(Ã3Πi?-~X3Σ? are consistent with previous absorption studies of C2O. A number of new transitions are identified and assigned. Fluorescence spectra have been recorded following single vibrational level laser excitation. Bands are assigned to ground state vibrational progressions. Values of 1967 and 1063 cm?1 are found for υ1″ and υ3″ stretching vibrations in the X?3Σ ? state. A subband structure in the fluorescence spectrum is observed and discussed. 相似文献
109.
The fluorescence decay and bimolecular electronic quenching behavior of C2O (3Πi) is reported. C2O(3Σ?) is produced by laser photolysis of C3O2 at 266 nm and is subsequently excited by a tunable flashlamp pumped dye laser. The fluorescence decay is highly nonexponential and dominated by both short (≈ 15 μs) and long (50–250 μs) decay components. The long-lived emission, itself, is nonexponential. The fluorescence decay is modeled as the sum of three exponential components. The short-lived emission is quenched by C3O2 at higher than the gas kinetic rate while the long-lived fluorescence is quenched much less efficiently. Fluorescence quenching measurements are also reported for collisions with Ar, N2 and O2. 相似文献
110.
Roger Atkinson William P. L. Carter Sara M. Aschmann Arthur M. Winer James N. Pitts 《国际化学动力学杂志》1984,16(4):469-481
Relative rate constants for the reaction of OH radicals with a series of branched alkanes have been determined at 297 ± 2 K, using methyl nitrite photolysis in air as a source of OH radicals. Using a rate constant for the reaction of OH radicals with n-butane of 2.58 × 10?12 cm3/molecule · s, the rate constants obtained are (× 1012 cm3/molecule · s): isobutane, 2.29 ± 0.06; 2-methylbutane, 3.97 ± 0.11; 2,2-dimethylbutane, 2.66 ± 0.08; 2-methylpentane, 5.68 ± 0.24; 3-methylpentane, 5.78 ± 0.11; 2,2,3-trimethylbutane, 4.21 ± 0.08; 2,4-dimethylpentane, 5.26 ± 0.11; methylcyclohexane, 10.6 ± 0.3; 2,2,3,3-tetramethylbutane, 1.06 ± 0.08; and 2,2,4-trimethylpentane, 3.66 ± 0.16. Rate constants for 2,2-dimethylbutane, 2,4-dimethylpentane, and methylclohexane have been determined for the first time, while those for the other branched alkanes are in generally good agreement with the literature data. Primary, secondary, and tertiary group rate constants at room temperature have been derived from these and previous data for alkanes and unstrained cycloalkanes, with the secondary and tertiary group rate constants depending in a systematic manner on the identity of the neighboring groups. The use of these group rate constants, together with a previous determination of the effect of ring strain energy on the OH radical rate constants for a series of cycloalkanes, allows the a priori estimation of OH radical rate constants for alkanes and cycloalkanes at room temperature. 相似文献