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891.
José G. Aguirre-De Paz Davir González-Calderón Aydeé Fuentes-Benítes Carlos González-Romero 《Tetrahedron letters》2018,59(18):1760-1762
The exploration of azide-enolate cycloaddition in the synthesis of novel Rufinamide analogs is reported for the first time. A very simple procedure involving the use of β-ketonitriles as dipolarophiles afforded 5-aril/heteroayl Rufinamide derivatives in two steps. 相似文献
892.
Díaz Rizo Oscar Barrios Cossio Josiel González Hernández Patricia Suárez Muñoz Margaret D’Alessandro Rodríguez Katia Melián Rodríguez Clara M. Martínez-Villegas Nadia V. Badawy Wael Frontasieva Marina 《Journal of Radioanalytical and Nuclear Chemistry》2018,317(2):1079-1087
Journal of Radioanalytical and Nuclear Chemistry - Peloids from some Cuban spas (San Diego, Elguea, Santa Lucía, Cajío and Colony) have been studied using Instrumental Neutron Activation... 相似文献
893.
Christina C Roggatz Mercedes González-Wangüemert Hugo Pereira Catarina Vizetto-Duarte Maria João Rodrigues Luísa Barreira 《Natural product research》2018,32(1):116-120
This work reports for the first time the nutritional profile, including proximate chemical composition, amino acids, fatty acids and minerals of Parastichopus regalis from the Mediterranean Sea (SE Spain). The studied species had a high moisture content, moderate protein and low lipid levels. The most abundant amino acids were glutamic acid, arginine and tyrosine. Polyunsaturated fatty acids, especially arachidonic acid, dominated the fatty acid profile. Iron, sodium, calcium and zinc were the most abundant mine rals. In general, P. regalis has a balanced nutritional quality suitable for human consumption. 相似文献
894.
895.
896.
J. F. Marco M. Gracia J. R. Gancedo T. González-Carreño A. Arcoya X. L. Seoane 《Hyperfine Interactions》1995,95(1):53-70
The characterization of an iron-containing natural zeolitic sample from the deposit of Tasajeras (Cuba) has been carried out by means of X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS),57Fe Mössbauer spectroscopy and Fe K-edge X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). The results show that iron is mainly located (ca. 96%) as Fe3+ in an octahedral site of the clinoptilolite framework. No evidence of tetrahedrally coordinated Fe3+ was found. The remaining 4% Fe is located as Fe2+ in an extraframework octahedral site, probably as a solvated ion, within the clinoptilolite structure. 相似文献
897.
González-Díaz PF 《Physical review D: Particles and fields》1995,51(12):7144-7147
898.
The dissociation constant of acetic acid in N-methylpropionamide (NMP) has been determined at 11 temperatures from 5 to 55°C by measurement of the electromotive force of cells without liquid junction containing hydrogen gas electrodes and silver-silver chloride electrodes. The pK at 25°C was found to be 7.995 (molal scale) as compared with 4.756 in water; thus, acetic acid is much weaker in NMP than in water despite the higher dielectric constant of the nonaqueous solvent (176 as compared with 78.3 at 25°C). The standard changes of enthalpy and entropy for the dissociation of acetic acid were calculated from the temperature coefficient of pK, and thermodynamic functions for the transfer dissociation process were obtained. The weakness of acetic acid in NMP is discussed in terms of electrostatic effects and solute-solvent interactions. 相似文献
899.
Alessandro Cembran Remedios González-Luque Luis Serrano-Andrés Manuela Merchán Marco Garavelli 《Theoretical chemistry accounts》2007,118(1):173-183
CASPT2//CASSCF/6-31G* computations are used on the singlet S
1 and S
2 states to map the photoisomerization process of the 11-cis retinal protonated Schiff base in vacuo and to characterize its
optical properties. It is shown that the spectroscopic observations recorded in Rhodopsin are reproduced quite well, calling
for a substantially neutral effect of the protein. Furthermore, a rationale is proposed for the unreactive population recently
observed in Rhodopsin, which is here addressed to the accessible S
2 state, behaving as a trap. The experimental transient absorption and (absorption-wavelength dependent) emission are discussed
and interpreted under the light of this novel model. Finally, a planarization of the β-ionone ring is observed on S
1, which may cause a steric lever effect into the protein pocket, thus assisting photoisomerization catalysis. The reported
results constitute a solid reference for further studies aimed to rationalize the effect of the environment on the photochemical
reactivity of retinal chromophores.
Electronic Supplementary Material The online version of this article (doi:) contains supplementary
material, which is available to authorized users.
Contribution to the Fernando Bernardi Memorial Issue. 相似文献
900.
Pisano L Farriol M Asensio X Gallardo I González-Lafont A Lluch JM Marquet J 《Journal of the American Chemical Society》2002,124(17):4708-4715
Fragmentation reactions of radical anions (mesolytic cleavages) of cyanobenzyl alkyl ethers (intramolecular dissociative electron transfer, heterolytic cleavages) have been studied electrochemically. The intrinsic barriers for the processes have been established from the experimental thermodynamic and kinetic parameters. These values are more than 3 kcal/mol lower as an average than the related homolytic mesolytic fragmentations of radical anions of 4-cyanophenyl ethers. In the particular case of isomers 4-cyanobenzyl phenyl ether and 4-cyanophenyl benzyl ether, the difference in intrinsic barriers amounts to 5.5 kcal/mol, and this produces an energetic crossing where the thermodynamically more favorable process (homolytic) is the kinetically slower one. The fundamental reasons for this behavior have been established by means of theoretical calculations within the density functional theory framework, showing that, in this case, the factors that determine the kinetics are clearly different (mainly present in the transition state) from those that determine the thermodynamics and they are not related to the regioconservation of the spin density ("spin regioconservation principle"). Our theoretical results reproduce quite well the experimental energetic difference of barriers and demonstrate the main structural origin of the difference. 相似文献