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81.
Recently, we have developed a new tight-binding quantum chemical molecular dynamics program “Colors” for combinatorial computational chemistry approach. This methodology is based on our original tight-binding approximation and realized over 5000 times acceleration compared to the conventional first-principles molecular dynamics method. In the present study, we applied our new program to the simulations on various realistic large-scale models of the automotive three-way catalysts, ultrafine Pt particle/CeO2(111) support. Significant electron transfer from the Pt particle to the CeO2(111) surface was observed and it was found to strongly depend on the size of the Pt particle. Furthermore, our simulation results suggest that the reduction of the Ce atom due to the electron transfer from the Pt particle to the CeO2 surface is a main reason for the strong interaction of the Pt particle and CeO2(111) support. 相似文献
82.
Jean-Marie Lehn 《Journal of Chemical Sciences》1994,106(5):915-922
The article discusses molecular recognition and overviews the key concepts -storage and retrieval of chemical information
by molecular structures, supramolecular reagents and catalysts, molecular transport, semiochemistry and self assembly. The
prospects of controlling supramolecular architecture through engineered molecular recognition and design of ‘programmed systems’
controlled by molecular information are also discussed. 相似文献
83.
84.
F.F. Karpeshin J. da Providência C. Providência J. da Providência Jr 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(3):319-326
Two types of extreme collective motion, large-amplitude many-phonon vibration of the ionic core and rotation of the cluster
with high angular momenta, are considered. The interplay between vibration and collective motion towards fission is discussed.
A new mechanism of formation and rupture of the neck is proposed which is based on the Franck-Condon principle, and accounts
for the interplay between vibration and fission. Under rotation, the change of the shape of the cluster and a phase transition
from axially symmetric to triaxial ellipsoid are predicted. For studying the effects, vibrational motion can be induced by
laser radiation. Rotational motion may arise in collisions of clusters.
Received 26 April 2001 and Received in final form 15 October 2001 相似文献
85.
Thermotropic copolyester fibers of oxynaphthoate and oxybenzoate have been subjected to conditions that promote solid-state polymerization as well as annealing. The annealing process causes the crystals to perfect with a simultaneous increase in heat of fusion and melting temperature. Solid-state polymerization, a reaction rate-controlled process, causes the polymer viscosity average molecular weight to increase by chain extension from about 14,000 g/mole to more than 87,000 g/mole with a simultaneous impressive increase in tenacity from about 10 g/d (1.2 GPa) to almost 30 g/d (3.7 GPa). To understand the changes in mechanical properties, we have modeled the fiber structure as short rod-like molecules poorly bonded to a continuous matrix of parallel molecules. Lengthening of the reinforcing molecules facilitates better transfer of load from matrix to molecules, resulting in higher tenacity fibers. © 1994 John Wiley & Sons, Inc. 相似文献
86.
87.
We have studied the temperature dependence of the radiative deactivation of the Pd-porphine triplet states in Shpol’skii matrices
in the temperature range 1.2–210 K. A substantial transformation of the phosphorescence spectra is observed as the temperature
increases and is due to the inclusion of thermally activated Pd-porphine states in the radiative deactivation processes. The
activation energy Ea of these Pd-porphine states is measured in matrices of n-octane and n-nonane. The splitting of the lowest quasidegenerate
triplet state ΔE(T2−T1) is determined for planar and distorted conformations of the Pd-porphine macrocycle in the n-octane matrix as 40 and 57 cm−1, respectively. The ability to use the temperature dependence of the phosphorescence properties of Pd-porphine to fabricate
molecular thermometers for the low-temperature range is analyzed.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 4, pp. 460–464, July–August, 2007. 相似文献
88.
89.
S. F. Chekmarev R. Mitri V. Bonaci-Koutecký 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):45-48
The ab initio molecular
dynamics (AIMD) [1] is combined with the heuristic, successive
confinement method of surveying a potential energy surface (PES)
[2], thereby offering a framework for the simulation study of
kinetics and equilibrium properties of metallic clusters. This
approach is applied to the study of Au4,
a cluster possessing a simple but specific PES, which consists
of very shallow and deep basins and due to this presents a
challenge to the conventional AIMD methods. Among other things,
the probabilities of the transitions between isomers have been
found, and on this basis, both the time-dependent and
equilibrium populations of the isomers have been calculated for
the conditions typical of the NeNePo experiments [3] in the
femtosecond pump-probe spectroscopy. 相似文献
90.
Let G = (V,E) be a graph or digraph and r : V → Z+. An r‐detachment of G is a graph H obtained by ‘splitting’ each vertex ν ∈ V into r(ν) vertices. The vertices ν1,…,νr(ν) obtained by splitting ν are called the pieces of ν in H. Every edge uν ∈ E corresponds to an edge of H connecting some piece of u to some piece of ν. Crispin Nash‐Williams 9 gave necessary and sufficient conditions for a graph to have a k‐edge‐connected r‐detachment. He also solved the version where the degrees of all the pieces are specified. In this paper, we solve the same problems for directed graphs. We also give a simple and self‐contained new proof for the undirected result. © 2003 Wiley Periodicals, Inc. J Graph Theory 43: 67–77, 2003 相似文献