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21.
Infrared—ultraviolet double resonance spectroscopy is used to demonstrate rapid collision-induced V-V transfer between the v6 and v4 vibrational manifolds of D2CO. The rate of transfer is at least gas-kinetic and is explained in terms of Coriolis coupling and rotationally specific, quasi-resonant relaxation channels 相似文献
22.
F. de Oliveira Santos P. Himpe M. Lewitowicz I. Stefan N. Smirnova N. L. Achouri J. C. Angélique C. Angulo L. Axelsson D. Baiborodin F. Becker M. Bellegui E. Berthoumieux B. Blank C. Borcea A. Cassimi J. M. Daugas G. de France F. Dembinski C. E. Demonchy Z. Dlouhy P. Dolégiéviez C. Donzaud G. Georgiev L. Giot S. Grévy D. Guillemaud Mueller V. Lapoux E. Liénard M. J. Lopez Jimenez K. Markenroth I. Matea W. Mittig F. Negoita G. Neyens N. Orr F. Pougheon P. Roussel Chomaz M. G. Saint Laurent F. Sarazin H. Savajols M. Sawicka O. Sorlin M. Stanoiu C. Stodel G. Thiamova D. Verney A. C. C. Villari 《The European Physical Journal A - Hadrons and Nuclei》2005,24(2):237-247
The excitation function for the elastic-scattering reaction p( 18Ne, p) 18Ne was measured with the first radioactive beam from the SPIRAL facility at the GANIL laboratory and with a solid cryogenic hydrogen target. Several broad resonances have been observed, corresponding to new excited states in the unbound nucleus 19Na. In addition, two-proton emission events have been identified and are discussed. 相似文献
23.
Narrowband tuning of a pulsed optical parametric oscillator (OPO) is achieved with a self-adaptive injection-seeded optical cavity employing a phase-conjugate reflector. This approach is used in a novel OPO system based on periodically poled KTiOPO4 and pumped at 532 nm by a pulsed Nd:YAG laser. The OPO is injection seeded at 835-855 nm by a continuous-wave tunable diode laser, which also enables a Rh:BaTiO3 photorefractive crystal to act as a wavelength-selective phase-conjugate reflector, with no need for active control of cavity length. The single-longitudinal-mode tunability and operational simplicity of this OPO system are demonstrated experimentally. 相似文献
24.
Owens TM Ludwig BJ Schneider KS Fosnacht DR Orr BG Holl MM 《Langmuir : the ACS journal of surfaces and colloids》2004,20(22):9636-9645
The oxidation of alkylsilane monolayers on Au has been studied by X-ray photoelectron spectroscopy, reflection-absorption infrared spectroscopy, contact-angle measurements, and scanning tunneling microscopy. Exposure of the monolayers at 298 K to pure O(2) or H(2)O (>5 x 10(-5) Torr and >150 000 L) does not cause oxidation. Ambient atmosphere only causes oxidation if direct sight lines are maintained to the sample. Ozone exposure results in rapid monolayer oxidation. Oxidation initially occurs only at the Si atom, resulting in formation of a cross-linked siloxane monolayer that retains alkyl surface termination. Prolonged ozone exposures result in the oxidation and subsequent loss of the alkyl chain. 相似文献
25.
Labiche M Orr NA Marqués FM Angélique JC Axelsson L Benoit B Bergmann UC Borge MJ Catford WN Chappell SP Clarke NM Costa G Curtis N D'Arrigo A de Góes Brennand E Dorvaux O Fazio G Freer M Fulton BR Giardina G Grévy S Guillemaud-Mueller D Hanappe F Heusch B Jones KL Jonson B Le Brun C Leenhardt S Lewitowicz M Lopez MJ Markenroth K Mueller AC Nilsson T Ninane A Nyman G de Oliveira F Piqueras I Riisager K Saint Laurent MG Sarazin F Singer SM Sorlin O Stuttgé L 《Physical review letters》2001,86(4):600-603
The two-neutron halo nucleus (14)Be has been investigated in a kinematically complete measurement of the fragments ((12)Be and neutrons) produced in dissociation at 35 MeV/nucleon on C and Pb targets. Two-neutron removal cross sections, neutron angular distributions, and invariant mass spectra were measured, and the contributions from electromagnetic dissociation (EMD) were deduced. Comparison with three-body model calculations suggests that the halo wave function contains a large nu(2s(1/2))(2) admixture. The EMD invariant mass spectrum exhibited enhanced strength near threshold consistent with a nonresonant soft-dipole excitation. 相似文献
26.
27.
Gy?rgy G?nd?s Gy?rgy Dombi James C. Orr 《Monatshefte für Chemie / Chemical Monthly》2000,20(3):1055-1059
The synthesis of a new chiral boroxazolidine was achieved which was used to control the stereochemistry of the borane reduction of the 20-keto group of steroids. The otherwise hardly accessible 20α-(20S)-alcohol can thus be prepared in a yield of 91%. 相似文献
28.
Isoperimetric inequalities are applied to a moving-boundaryproblem for doubly-connected domains. This problem occurs forexample in electrochemistry, in which case the domains in questionare the electrolyte of an electrolytic cell. The two electrodessurrounding the electrolyte are assumed to grow or dissolve,at different rates in general, by electrochemical reaction.We obtain optimal estimates showing, for example, that the leastchange in volume of each electrode always occurs in sphericalsymmetry. 相似文献
29.
Ultraviolet Absorption Induces Hydrogen‐Atom Transfer in G⋅C Watson–Crick DNA Base Pairs in Solution
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Dr. Katharina Röttger Hugo J. B. Marroux Dr. Michael P. Grubb Philip M. Coulter Hendrik Böhnke Dr. Alexander S. Henderson Dr. M. Carmen Galan Prof. Friedrich Temps Prof. Andrew J. Orr‐Ewing Dr. Gareth M. Roberts 《Angewandte Chemie (International ed. in English)》2015,54(49):14719-14722
Ultrafast deactivation pathways bestow photostability on nucleobases and hence preserve the structural integrity of DNA following absorption of ultraviolet (UV) radiation. One controversial recovery mechanism proposed to account for this photostability involves electron‐driven proton transfer (EDPT) in Watson–Crick base pairs. The first direct observation is reported of the EDPT process after UV excitation of individual guanine–cytosine (G?C) Watson–Crick base pairs by ultrafast time‐resolved UV/visible and mid‐infrared spectroscopy. The formation of an intermediate biradical species (G[?H]?C[+H]) with a lifetime of 2.9 ps was tracked. The majority of these biradicals return to the original G?C Watson–Crick pairs, but up to 10 % of the initially excited molecules instead form a stable photoproduct G*?C* that has undergone double hydrogen‐atom transfer. The observation of these sequential EDPT mechanisms across intermolecular hydrogen bonds confirms an important and long debated pathway for the deactivation of photoexcited base pairs, with possible implications for the UV photochemistry of DNA. 相似文献