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81.
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84.
Three new porphyrins bearing in the meso positions 4-(pyrazol-1-yl)-2,3,5,6-tetrafluorophenyl substituents have been prepared and characterized by nmr spectroscopy. 相似文献
85.
In the paper we prove two inequalities involving Gelfand numbers of operators with values in a Hilbert space. The first inequality is a Rademacher version of the main result in [Pa-To-1] which relates the Gelfand numbers of an operator from a Banach spaceX intol
2
n
with a certain Rademacher average for the dual operator. The second inequality states that the Gelfand numbers of an operatoru froml
1
N
into a Hilbert space satisfy the inequality
相似文献
86.
D. Bisello G. Busetto A. Castro M. Nigro M. Penzo L. Pescara M. Posocco P. Sartori L. Stanco Z. Ajaltouni A. Falvard J. Jousset B. Michel J. C. Montret A. Antonelli R. Baldini A. Calcaterra G. Capon M. Schioppa J. -E. Augustin G. Cosme F. Couchot B. Dudelzak F. Fulda G. Grosdidier B. Jean-Marie S. Jullian D. Lalanne V. Lepeltier F. Manè C. Paulot R. Riskalla Ph. Roy G. Szklarz DM Collaboration 《Zeitschrift fur Physik C Particles and Fields》1988,39(1):13-19
Thee + e ?→K + K ? cross section has been measured from about 750 events in the energy interval \(1350 \leqq \sqrt s \leqq 2400 MeV\) with the DM2 detector at DCI. TheK ± form factor |F F ±| cannot be explained by the ρ, ω, ? and ρ′(1600). An additional resonant amplitude at 1650 MeV has to be added as suggested by a previous experiment. 相似文献
87.
Strong, low-energy two-photon absorption in extended amine-terminated cyano-substituted phenylenevinylene oligomers 总被引:8,自引:0,他引:8
Chung SJ Rumi M Alain V Barlow S Perry JW Marder SR 《Journal of the American Chemical Society》2005,127(31):10844-10845
Three quadrupolar oligophenylenevinylenes with five rings in the conjugated backbone, terminal donor groups, and various acceptors and/or donors along the backbone were synthesized and their two-photon spectroscopic properties investigated. These chromophores exhibit large two-photon absorption cross sections over a wide wavelength range and two distinct peaks, the strongest of which (deltamax > 3600 GM) is observed at 960-970 nm, a wavelength close to twice the value of the linear absorption maximum (2lambda(1)max). The findings on these chromophores are compared with those for analogous molecules with shorter conjugation length, for which the main two-photon band is at significantly shorter wavelength than 2lambda(1)max. 相似文献
88.
Sabbe MK Saeys M Reyniers MF Marin GB Van Speybroeck V Waroquier M 《The journal of physical chemistry. A》2005,109(33):7466-7480
A complete and consistent set of 95 Benson group additive values (GAV) for the standard enthalpy of formation of hydrocarbons and hydrocarbon radicals at 298 K and 1 bar is derived from an extensive and accurate database of 233 ab initio standard enthalpies of formation, calculated at the CBS-QB3 level of theory. The accuracy of the database was further improved by adding newly determined bond additive corrections (BAC) to the CBS-QB3 enthalpies. The mean absolute deviation (MAD) for a training set of 51 hydrocarbons is better than 2 kJ mol(-1). GAVs for 16 hydrocarbon groups, i.e., C(C(d))(3)(C), C-(C(d))(4), C-(C(t))(C(d))(C)(2), C-(C(t))(C(d))(2)(C), C-(C(t))(C(d))(3), C-(C(t))(2)(C)(2), C-(C(t))(2)(C(d))(C), C-(C(t))(2)(C(d))(2), C-(C(t))(3)(C), C-(C(t))(3)(C(d)), C-(C(t))(4), C-(C(b))(C(d))(C)(H), C-(C(b))(C(t))(H)(2), C-(C(b))(C(t))(C)(H), C-(C(b))(C(t))(C)(2), C(d)-(C(b))(C(t)), for 25 hydrocarbon radical groups, and several ring strain corrections (RSC) are determined for the first time. The new parameters significantly extend the applicability of Benson's group additivity method. The extensive database allowed an evaluation of previously proposed methods to account for non-next-nearest neighbor interactions (NNI). Here, a novel consistent scheme is proposed to account for NNIs in radicals. In addition, hydrogen bond increments (HBI) are determined for the calculation of radical standard enthalpies of formation. In particular for resonance stabilized radicals, the HBI method provides an improvement over Benson's group additivity method. 相似文献
89.
Denise Baudry Michel Ephritikhine Hugh Felkin Yves Dromzee Yves Jeannin 《Journal of organometallic chemistry》1984,272(3):403-409
Bis(triphenylphosphine)(η-cyclohexa-1,3-diene)rhenium trihydride, (Ph3P)2(η-C6H8)ReH3 (I) crystallises in the space group C2/c with cell dimensions a 22.76(2), b 10.14(1) c 29.813(6) Å, β 97.69(8)°. The final refinement of 126 variables using 1580 non-zero reflections resulted in a final R value of 0.064. In spite of uncertainties in some of the atomic positions, the structure of I is compatible with a trihydrido diene compound with a distorted pentagonal bipyramidal configuration, rather than with a dihydrido cyclohexenyl compound having an “agostic” CH ? Re interaction. The factors which govern the structure of the complexes (Ph3P)2(η-1,3-diene)ReH3 are discussed. 相似文献
90.
The reaction between dibutyltin dilaurate (DBTL) and chloro-4-hexene-2 (containing its isomer chloro-2-hexene-3) as a model compound for the allylic chlorine atom in poly(vinyl chloride) has been studied in dichlorobutane solution at 80°C. The reactions observed—elimination of HCl to give hexadiene and substitution of the laurate group to give hexenyl laurate—are believed to obey E2 and SN2 mechanisms through a common intermediate carbocation, with a rather low selectivity towards the substitution owing to the associated structure of the DBTL. The kinetics are complex because of the complex nature of the exchange reaction between DBTL and Bu2SnCl2. A reverse reaction between the hexenyl laurate and the organo-tin chloride is proposed to explain the limitation of the substitution reaction. 相似文献
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