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排序方式: 共有188条查询结果,搜索用时 46 毫秒
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Anatol Jaworek Andrzej Krupa Arkadiusz T. Sobczyk Artur Marchewicz Michał Szudyga Teresa Antes Wamadeva Balachandran Francesco Di Natale Claudia Carotenuto 《Journal of Electrostatics》2013,71(3):345-350
New regulations regarding the PM1 emission by power plants and transport vehicles require novel technical solutions for the abatement of particulate matter emission in submicron size range. Particles of this size are difficult to remove by conventional methods, and therefore various variants of wet electrostatic scrubbers have been developed. In such devices, the electrostatic forces between charged particles and collectors (water droplets) are used to permanently remove them from the gas. The paper focuses on the state-of-the-art of wet electrostatic scrubbing technique used for the removal of submicron particulate matter from exhaust gases with particular emphasis upon marine Diesel engines. 相似文献
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Frelek J Kowalska P Masnyk M Kazimierski A Korda A Woźnica M Chmielewski M Furche F 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(23):6732-6744
The biological activity of bicyclic beta-lactam antibiotics depends strongly on the absolute configuration of the bridgehead carbon atom. Frelek and co-workers proposed an empirical helicity rule relating the configuration of the bridgehead carbon atom to the sign of the 220 nm band in the electronic circular dichroism (CD) spectrum of beta-lactams. Here we use synthetic organic chemistry, CD spectroscopy, and time-dependent density functional theory (TDDFT) to investigate the validity of this structure-property relationship for eight model compounds. For conformationally flexible beta-lactams, substantial thermal effects are found which must be included in calculations. To this end, we combine TDDFT calculations of CD with full quantum-mechanical Born-Oppenheimer molecular dynamics (MD) simulations for the first time. The CD spectra are sampled with ground-state density functional trajectories of up to 60 ps. The MD simulations show a surprisingly high sensitivity of the CD to the molecular conformation. On the other hand, the relation between CD and thermally averaged structural parameters is much less complex. While the helicity rule does not seem to hold for individual conformers, it is confirmed by the calculations for seven out of eight systems studied if thermally averaged CD spectra and structures are considered. Since thermal effects on CD can be larger than typical inherent inaccuracies of TDDFT, our results emphasize the need for a systematic treatment of conformational dynamics in CD calculations even for moderately flexible systems. Temperature-dependent CD measurements are very useful for this purpose. Our results also suggest that CD spectroscopy may be used as a sensitive probe of conformational dynamics if combined with electronic structure calculations. 相似文献
165.
Reaction of 3,3′,4,4′-tetramethyl-1,1′-diphosphaferrocene (1) with [Re2(CO)8(CH3CN)2] afforded two trimetallic complexes in which the heterometallocene is ligated across the Re-Re bond. The structure of the complex having 1 bridging the Re2(CO)8 moiety through two P atoms was determined by X-ray diffraction and compared with those of analogous complexes with organic bridging bis-phosphines. The second complex obtained in this reaction presumably contains 1 acting as a (P,Fe) bridging ligand. 相似文献
166.
Ciesielski A Krygowski TM Cyrański MK 《Journal of chemical information and modeling》2008,48(7):1358-1366
A topological model for estimating the stability of benzenoid hydrocarbons (BHs) is presented showing an acceptable linear dependence on Hess-Schaad resonance energy per pi-electron values. The topological measure of stability is accessible by use of pencil calculation and is based on counting cis-type fragments of double bonds in all canonical structures of a given BH. Evidence is given that infinite chains of straight linear polyacenes are always less stable than the kinked ones. 相似文献
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István Szilágyi Gergely Kovács Mária Farkas Gábor L. Zügner Agnieszka Gola Sándor Dóbé Attila Demeter 《Reaction Kinetics and Catalysis Letters》2009,96(2):437-446
The pressure dependence of the photodissociation quantum yield of acetone has been determined in different buffer gases at
308 nm. Results by Stern-Volmer analyses are in accordance with a suggested photolysis mechanism. Luminescence spectra, lifetimes
and transition dipole moments have been determined. The energy transfer process by O2 to give O2(1Δg) is of minor importance in the case of the singlet excited state of acetone, while it is the dominant deactivation process
for the triplet state. 相似文献
170.
Grzegorz Litak Marek Borowiec Arkadiusz Syta Kazimierz Szabelski 《Chaos, solitons, and fractals》2009,40(5):2414-2429
We examine the Melnikov criterion for a global homoclinic bifurcation and a possible transition to chaos in case of a single degree of freedom nonlinear oscillator with a symmetric double well nonlinear potential. The system was subjected simultaneously to parametric periodic forcing and self-excitation via negative damping term. Detailed numerical studies confirm the analytical predictions and show that transitions from regular to chaotic types of motion are often associated with increasing the energy of an oscillator and its escape from a single well. 相似文献