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81.
非微扰量子电动力学的发展使我们可以利用精确的波函数和非微扰的散射理论来研究多光子电离问题.文章作者及其合作者发展了光电子角分布的处理方法,利用复合相位Bessel函数来表征光电子的跃迁几率幅,将光电子的角分布与复合相位Bessel函数直接联系起来.研究发现,复合相位Bessel函数的性质决定了光电子角分布的主要特点及其随激光强度、频率以及光电子能量的演化.该理论不但证实了实验上已经观测到的各种光电子角分布,而且还预言了实验上尚未观测到的光电子角分布,确立了光电子角分布的标度定律. 相似文献
82.
Davor Pavuna Daniel Ariosa Dominique Cloetta Claudia Cancellieri Mike Abrecht 《Pramana》2008,70(2):237-243
Since 1997 we systematically perform direct angle resolved photoemission spectroscopy (ARPES) on in-situ grown thin (<30 nm) cuprate films. Specifically, we probe low-energy electronic structure and properties of high-T
c superconductors (HTSC) under different degrees of epitaxial (compressive vs. tensile) strain. In overdoped and underdoped
in-plane compressed (the strain is induced by the choice of substrate) ≈15 nm thin La2 − x
Sr
x
CuO4 (LSCO) films we almost double T
c to 40 K, from 20 K and 24 K, respectively. Yet the Fermi surface (FS) remains essentially two-dimensional. In contrast, ARPES
data under tensile strain exhibit the dispersion that is three-dimensional, yet T
c drastically decreases. It seems that the in-plane compressive strain tends to push the apical oxygen far away from the CuO2 plane, enhances the two-dimensional character of the dispersion and increases T
c, while the tensile strain acts in the opposite direction and the resulting dispersion is three-dimensional. We have established
the shape of the FS for both cases, and all our data are consistent with other ongoing studies, like EXAFS. As the actual
lattice of cuprates is like a ‘Napoleon-cake’, i.e. rigid CuO2 planes alternating with softer ‘reservoir’, that distort differently under strain, our data rule out all oversimplified two-dimensional
(rigid lattice) mean field models. The work is still in progress on optimized La-doped Bi-2201 films with enhanced T
c.
相似文献
83.
Substance P and hemokinin‐1 were predominantly examined by immunoassays with their limitation to differentiate appropriately between both peptides. The use of liquid chromatography coupled with tandem mass spectrometry is a promising, highly selective alternative. Adsorption processes have been identified in preliminary experiments to play a crucial role in the loss of mass spectrometry intensity of both peptides. Therefore, a design of experiments concept was created to minimize nonspecific peptide adsorption. For this purpose, the most critical influencing parameters—(1) the composition of the injection solvent as well as (2) the most suitable container material—were systematically and concordantly investigated. The addition of modifiers, such as formic acid, dimethyl sulfoxide, and organic solvents, to the injection solvent led to a substantial gain of intensity of substance P and hemokinin‐1 compared to the start gradient as an injection solvent. Furthermore, the systematic investigation underlined the high impact of the container material, demonstrating polypropylene as the most favorable material. A conjoint injection solvent optimum was found to determine both peptides simultaneously by the conduction of a sweet‐spot analysis. The experimental design substantially reduced nonspecific peptide adsorption and enabled the simultaneous and selective determination of endogenous substance P and hemokinin‐1 plasma levels. 相似文献
84.
Summary The partition of the spin probe TEMPO between the fluid lipid phase of single-walled vesicles of dipalmitoylphosphatidylcholine
and the aqueous bulk solution have been used to investigate the interaction of monovalent ions with polar head of neutral
phospholipids. The study has been performed by electron spin resonance (ESR) spectroscopy in the temperature range of (20÷60)°C
and in the presence of (0÷3) M 1∶1 electrolyte. In the absence of electrolyte the spin probe TEMPO reveals the characteristic
order→disorder DPPC main phase transition atT
m≈37°C, while the pretransition occurs atT
p≈27.5°C. On increasing the ionic strength of the dispersion medium it results for the partition coefficient,P
C, that, at each temperature,P
C(3)>P
C(2)>P
C(1)>P
C(0). Correspondingly, the pretransition disappears and theT
m value downshifts from ≈37°C with 0 M electrolyte to ≈34°C with 3M salt in the order:T
m(3)>T
m(2)>T
m(1)>T
m(0). The results suggest an increase in the net surface charge density of vesicles due to high ionic-strength values. The
alteration of the electric interactions occurring into the polar zone of DPPC bilayer reduces the hindrances which, in turn,
favour the enhancement of TEMPO partitioning in the hydrophobic core of phospholipid bilayers.
The authors of this paper have agreed to not receive the proofs for correction. 相似文献
85.
G. R. Mason G. A. Beer M. S. Dixit S. K. Kim J. A. MacDonald A. Olin R. M. Pearce 《Nuclear Physics A》1980,340(2):240-248
Energies and lorentzian widths of pionic K X-ray transitions have been measured in liquid 3He with improved accuracy. The strong interaction on the π3He 1s level is found to be attractive and to produce an increase in the K transition energies of 34 ± 4 eV; the measured lorentzian width is 36 ±7 eV. Measured values are also presented for K X-ray energies in liquid π4He and μ4He, the lorentzian width of the 1s level in π4He, and relative intensities of K X-ray transitions in π3He, π4He and μ4He. The measurements are compared with those of others and with recent theoretical calculations. 相似文献
86.
C. Biely R. Hanel S. Thurner 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,67(3):285-289
We consider social systems in which agents are not only characterized by their states but also have the freedom to choose
their interaction partners to maximize their utility. We map such systems onto an Ising model in which spins are dynamically
coupled by links in a dynamical network. In this model there are two dynamical quantitieswhich arrange towards a minimum energy
state in the canonical framework:the spins, si, and the adjacency matrix elements, cij.The model is exactly solvable because microcanonical partition functions reduce to productsof binomial factors as a direct
consequence of the cij minimizing energy. We solve the system for finite sizes and for the two possible thermodynamic limits and discussthe phase
diagrams. 相似文献
87.
88.
We formulate a theory of nonrelativistic scattering in one dimension based on the J-matrix method. The scattering potential is assumed to have a finite range such that it is well represented by its matrix elements in a finite subset of a basis that supports a tridiagonal matrix representation for the reference wave operator. Contrary to our expectation, the 1D formulation reveals a rich and highly nontrivial structure compared to the 3D formulation. Examples are given to demonstrate the utility and accuracy of the method. It is hoped that this formulation constitutes a viable alternative to the classical treatment of 1D scattering problem and that it will help unveil new and interesting applications. 相似文献
89.
90.
B. Tadić V. Priezzhev 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(2):143-146
We investigate by random-walk simulations and a mean-field theory how growth by biased addition of nodes affects flow of the
current through the emergent conducting graph, representing a digital circuit. In the interior of a large network the voltage
varies with the addition time s < t of the node as V(s) ∼ ln(s)/s
θ when constant current enters the network at last added node t and leaves at the root of the graph which is grounded. The topological closeness of the conduction path and shortest path
through a node suggests that the charged random walk determines these global graph properties by using only local search algorithms. The results agree with mean-field theory on tree structures, while the numerical method is applicable
to graphs of any complexity.
Received 26 August 2002 Published online 29 November 2002 相似文献