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931.
932.
La0.45Ce0.45F3:Tb (10 mol% Tb) nanoparticles was synthesized via sonochemical method and then coated with silica (SiO2) shells through a microemulsion process, resulting in the formation of core/shell structured LaCeF3:Tb/SiO2 nanoparticles. The obtained core/shell LaCeF3:Tb/SiO2 nanoparticles are spherical and uniform in size (average size about 60 nm), strongly fluorescent, and long fluorescence lifetime
(1.87 ms). This kind of nanoparticles was water-soluble, which could be applied in biological labeling and other fields. 相似文献
933.
Low-lying equilibrium geometric structures of Phosphorus-doped aluminum cluster Al
n
P (n = 2–12) clusters obtained by an all-electron linear combination of atomic orbital approach, within spin-polarized density
functional theory, are reported. The binding energy, dissociation energy, and stability of these clusters are studied within
the local spin density approximation (LSDA) and the three-parameter hybrid generalized gradient approximation (GGA) due to
Becke-Lee-Yang-Parr (B3LYP). Ionization potentials, electron affinities, hardness, and static polarizabilities are calculated
for the ground-state structures within the GGA. It is observed that symmetric structures with the P atom occupying a peripheral
position are lowest-energy geometries of Al
n
P (n = 2, 4–11), while the P impurities of Al3P and Al12P prefer to occupy internal sites in the aluminum clusters. Generalized gradient approximation extends bond lengths as compared
to the LSDA lengths. The odd-even oscillations in the dissociation energy, the second differences in energy, the HOMO–LUMO
gaps, the ionization potential, the electron affinity, and the hardness are more pronounced within both GGA and LSDA. The
stability analysis based on the energies clearly shows the clusters with an even number of valence electrons are more stable
than clusters with odd number of valence electrons. 相似文献
934.
935.
936.
Considering the perturbation, the results of theoretical calculation of five Rydberg series energy levels 6s2ns^2S1/2 (n = 7 - 20), 6s^2nd^2D3/2 (n = 6 - 20), 6s^2nd^2D5/2 (n = 6 - 20), 6s^2np^2P1/2^0 (n = 7- 20), and 6s^2np^2P3/2^0 (n = 7-20) for Tl I are presented using the weakest bound electron potential model (WBEPM) theory. Furthermore, the radiative lifetimes of this five series are also calculated. The calculated values of energy levels and lifetimes are in good agreement with the experimental results. 相似文献
937.
Nine low-lying electronic states of the AsP molecule, including Σ , Ⅱ, and △ symmetries with singlet, triplet, and quintet spin multiplicities, are studied using multi-reference configuration interaction method.The potential energy curves and the spectroscopic constants of these nine states are determined, and compared with the experimental observed data as well as other theoretical works available at present.Three quintet states are reported for the first time.Furthermore, the analytical potential energy functions of these states are fitted using Murrell-Sorbie function and least square fitting method. 相似文献
938.
Kreher and Rees 3 proved that if h is the size of a hole in an incomplete balanced design of order υ and index λ having minimum block size , then, They showed that when t = 2 or 3, this bound is sharp infinitely often in that for each h ≥ t and each k ≥ t + 1, (t,h,k) ≠(3,3,4), there exists an ItBD meeting the bound. In this article, we show that this bound is sharp infinitely often for every t, viz., for each t ≥ 4 there exists a constant Ct > 0 such that whenever (h ? t)(k ? t ? 1) ≥ Ct there exists an ItBD meeting the bound for some λ = λ(t,h,k). We then describe an algorithm by which it appears that one can obtain a reasonable upper bound on Ct for any given value of t. © 2002 Wiley Periodicals, Inc. J Combin Designs 10: 256–281, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jcd.10014 相似文献
939.
A series of well-defined enantiopure 1,1'-binaphthyl-based oligomers linked through their 6,6'-positions, ranging from quaternaphthol to decanaphthol, have been synthesized by Suzuki and Stille coupling reactions. These novel oligonaphthyls have been characterized by (1)H and (13)C[(1)H] NMR spectroscopy and high-resolution mass spectrometry. A combination of X-ray structural and CD studies suggests that these oligonaphthyls adopt zigzag but not helical conformations. As the chain length increases, the compounds show enhanced fluorescence. The fluorescence intensity of oligonaphthols is almost 2 orders of magnitude higher than that of 1,1'-bi-2-naphthol and can be effectively and enantioselectively quenched with trans-1,2-diaminocyclohexane with an enantioselectivity factor of 1.24. The present work thus demonstrates the potential of constructing chiral sensory materials based on well-defined enantiopure oligonaphthols. 相似文献
940.
In the solid state, interlocking of the lateral phen ligands at the acute angle sites of the molecular [Cu2(bpa)2-(phen)2(H2O)]2 rhombi via aromatic pi-pi stacking interactions into the cavities of the adjacent rhombi generates laminated polyrotaxanes that are further assembled into a 3D network via similar interactions between the phen ligands at the obtuse angle sites. 相似文献