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排序方式: 共有449条查询结果,搜索用时 15 毫秒
441.
Acoustical Physics - The conventional beamforming algorithm has been generalized, making it possible to mutually take into account the data of sequential measurements by one microphone array placed... 相似文献
442.
Tsiok O. B. Brazhkin V. V. Tverjanovich A. S. Bychkov E. 《Journal of Experimental and Theoretical Physics》2022,134(1):51-59
Journal of Experimental and Theoretical Physics - The relaxation of the optical absorption edge and of the linear sizes of stoichiometric GeS2 glass densified at a high hydrostatic pressure have... 相似文献
443.
444.
Alkali‐Metal Trichloroacetates for Dichloromethylenation of Fullerenes: Nucleophilic Addition‐Substitution Route 下载免费PDF全文
Marina G. Apenova Vladimir A. Akhmetov Nikita M. Belov Dr. Alexey A. Goryunkov Dr. Ilya N. Ioffe Dr. Natalia S. Lukonina Dr. Vitaliy Yu. Markov Prof. Dr. Lev N. Sidorov 《化学:亚洲杂志》2014,9(3):915-923
The first experimental evidence that fullerenes react with alkali‐metal trichloroacetates through a nucleophilic addition‐substitution route, yielding dichloromethylenefullerenes as the final products, is reported. The intermediates, C60(CCl3)? and C70(CCl3)? anions, have been isolated in their protonated forms as ortho‐C60(CCl3)H, as well as three ortho and one para isomer of C70(CCl3)H. The structures were unambiguously determined by means of 1H, 13C, and 1H–13C HMBC NMR spectroscopy along with UV/Vis spectroscopy. The observed regiochemistry was analyzed with the aid of quantum chemical calculations. Conversion of the protonated compounds into the [6,6]‐closed C60/70(CCl2) cycloadducts under basic conditions can be effected only for the ortho isomers, whereas para‐C70(CCl3)H decomposes back into pristine C70. 相似文献
445.
Plekan O Feyer V Richter R Moise A Coreno M Prince KC Zaytseva IL Moskovskaya TE Soshnikov DY Trofimov AB 《The journal of physical chemistry. A》2012,116(23):5653-5664
The electronic structures of the purine derivatives xanthine, hypoxanthine and caffeine have been investigated in the gas phase using C, N, and O 1s X-ray photoemission (XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The results have been interpreted by means of ab initio calculations using the third-order algebraic-diagrammatic construction (ADC(3)) method for the one-particle Green's function and the second-order ADC method (ADC(2)) for the polarization propagator. The carbon, nitrogen and oxygen K-edge NEXAFS spectra of xanthine and caffeine are very similar, since the molecules differ only by substitution of three hydrogen atoms by methyl groups. For hypoxanthine, the electronic structure and spectra differ considerably from xanthine as the purine ring is more highly conjugated, and there is one less oxo group. Effects due to oxo-hydroxy tautomerism were not observed. However, the two oxo tautomeric forms of hypoxanthine oxo-N(9)-H and oxo-N(7)-H are populated in the gas phase, and the C 1s spectra can be simulated only by taking account of these two tautomers, with appropriate Boltzmann population ratios which we have also calculated. For xanthine and caffeine, single tautomeric forms were observed. 相似文献
446.
Mathematical Notes - The finite groups containing exactly two noncomplemented subgroups are described. 相似文献
447.
Masselin Pascal Le Coq David Calvez Laurent Petracovschi Elena Lépine Eric Bychkov Eugène Zhang Xianghua 《Applied Physics A: Materials Science & Processing》2012,106(3):697-702
Optical properties of chalcogenide glasses belonging to the series (80GeS2–20Ga2S3)100−x
(CsCl)
x
with x=0;5;10;15;20 were investigated. The linear refractive indices (n
0) were determined by prism measurements at four wavelengths: 633 nm, 825 nm, 1311 nm, and 1511 nm. Z-scan experiments were
performed at 800 nm to measure the non-linear indices (n
2) and the absorption coefficients (β). CsCl additions in the base glass (80GeS2–20Ga2S3) are characterized by a white shift of the transmission in the visible range and a strong decrease of both n
0 and n
2. As the same time, β is also decreasing and this results in a figure of merit FOM=2βλ/n
2 that remains relatively low at 800 nm, meaning that this series of highly non-linear glasses should be very suitable for
optical switching applications at telecommunication wavelengths. 相似文献
448.
Helton JS Chen Y Bychkov GL Barilo SN Rogado N Cava RJ Lynn JW 《J Phys Condens Matter》2012,24(1):016003
Single crystal neutron diffraction studies have been performed on the S = 3/2 kagome staircase compound Co(3)V(2)O(8) with a magnetic field applied along the magnetization easy-axis ([Formula: see text]). Previous zero-field measurements (Chen Y et al 2006 Phys. Rev. B 74 014430) reported a rich variety of magnetic phases, with a ferromagnetic ground state as well as incommensurate, transversely polarized spin density wave (SDW) phases (with a propagation vector of [Formula: see text]) interspersed with multiple commensurate lock-in transitions. The magnetic phase diagram with [Formula: see text] adds further complexity. For small applied fields, μ(0)H ≈ 0.05 T, the commensurate lock-in phases are destabilized in favor of the incommensurate SDW ones, while slightly larger applied fields restore the commensurate lock-in phase with δ = 1/2 and yield a new commensurate phase with δ = 2/5. For measurements in an applied field, higher-order scattering is observed that corresponds to the second harmonic. 相似文献
449.
Aleksey.I.Aleksandrov Ivan A.Aleksandrov Vitaliy G.Shevchenko Aleksandr N.Ozerin 《高分子科学》2021,39(5):601-609
Rheological explosion in polymers under uniaxial compression in an open volume occurs at the end of continuous rapid plastic deformation after several stages of creep. Two types of polymers were chosen for this study: brittle glassy amorphous polystyrene and thermoplastic semi-crystalline polypropylene. Electric pulses were detected during explosion, and their spectra were analyzed with two models.X-ray diffraction methods were used to investigate changes in the structure and morphology of polymers during deformation and rheological explosion. The pores appear in polymer in this process, and their shape and size distribution were derived from X-ray experiments. The main reason for the formation of pores in polymer samples in rheological explosion experiments is the intense microshifts in the polymer volume under the action of high applied pressure. 相似文献