全文获取类型
收费全文 | 12234篇 |
免费 | 312篇 |
国内免费 | 1626篇 |
专业分类
化学 | 8315篇 |
晶体学 | 112篇 |
力学 | 100篇 |
综合类 | 192篇 |
数学 | 902篇 |
物理学 | 2716篇 |
无线电 | 1835篇 |
出版年
2023年 | 114篇 |
2022年 | 185篇 |
2021年 | 111篇 |
2020年 | 168篇 |
2019年 | 166篇 |
2018年 | 130篇 |
2017年 | 188篇 |
2016年 | 203篇 |
2015年 | 174篇 |
2014年 | 359篇 |
2013年 | 818篇 |
2012年 | 636篇 |
2011年 | 534篇 |
2010年 | 456篇 |
2009年 | 631篇 |
2008年 | 707篇 |
2007年 | 917篇 |
2006年 | 755篇 |
2005年 | 661篇 |
2004年 | 585篇 |
2003年 | 481篇 |
2002年 | 417篇 |
2001年 | 358篇 |
2000年 | 1171篇 |
1999年 | 828篇 |
1998年 | 765篇 |
1997年 | 224篇 |
1996年 | 231篇 |
1995年 | 194篇 |
1994年 | 181篇 |
1993年 | 156篇 |
1992年 | 139篇 |
1991年 | 102篇 |
1990年 | 63篇 |
1989年 | 54篇 |
1988年 | 35篇 |
1987年 | 33篇 |
1986年 | 21篇 |
1985年 | 32篇 |
1984年 | 20篇 |
1983年 | 14篇 |
1982年 | 21篇 |
1981年 | 35篇 |
1980年 | 15篇 |
1979年 | 14篇 |
1978年 | 18篇 |
1977年 | 11篇 |
1976年 | 9篇 |
1974年 | 8篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
81.
M. Pinterić M. Miljak N. Biškup O. Milat I. Aviani S. Tomić D. Schweitzer W. Strunz I. Heinen 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(2):217-225
We report a detailed characterization of the magnetism and AC transport in single crystals of the organic conductor -(BEDT-TTF)2Cu[N(CN)2]Cl by means of magnetic anisotropy measurements and low-frequency dielectric spectroscopy. Magnetic anisotropy obeys Curie-Weiss
law with negative Curie-Weiss temperature in the temperature range 300 K-70 K. An antiferromagnetic transition with concomitant
canted antiferromagnetic state is established at 22 K. A large hysteresis in the spin-flop transition and magnetic field reversal
of the weak ferromagnetic magnetization are documented for the first time. A broad dielectric relaxation mode of moderate
strength () emerges at 32 K, and weakens with temperature. The mean relaxation time, much larger than that expected for single-particle
excitations, is thermally activated in a manner similar to the DC conductivity and saturates below 22 K. These features suggest
the origin of the broad relaxation as an intrinsic property of the weak ferromagnetic ground state. We propose a charged domain
wall in a random ferromagnetic domain structure as the relaxation entity. We argue that the observed features might be well
described if Dzyaloshinsky-Moriya interaction is taken into account. A Debye relaxation with similar temperature dependence
was also observed and seems to be related to an additional ferromagnetic-like, most probably, field-induced phase. We tentatively
associate this phase, whose tiny contribution was sample dependent, with a Cu2+ magnetic subsystem.
Received 15 June 1998 and Received in final form 1 February 1999 相似文献
82.
M. Grifoni E. Paladino U. Weiss 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(4):719-729
The dynamics of the reduced density matrix of the driven dissipative two-state system is studied for a general diagonal/off-diagonal
initial state. We derive exact formal series expressions for the populations and coherences and show that they can be cast
into the form of coupled nonconvolutive exact master equations and integral relations. We show that neither the asymptotic
distributions, nor the transition temperature between coherent and incoherent motion, nor the dephasing rate and relaxation
rate towards the equilibrium state depend on the particular initial state chosen. However, in the underdamped regime, effects
of the particular initial preparation, e.g. in an off-diagonal state of the density matrix, strongly affect the transient dynamics. We find that an appropriately tuned external ac-field
can slow down decoherence and thus allow preparation effects to persist for longer times than in the absence of driving.
Received 23 October 1998 and Received in final form 26 February 1999 相似文献
83.
A. Bhattacharyay J.K. Bhattacharjee 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(1):137-141
Reaction diffusion systems can exhibite both spatial and temporal patterns. We show that the effect of spatial variation of
the removal rate can have significant effect on the stability boundaries. In particular there can be a case of parametric
resonance.
Received 11 March 1998 相似文献
84.
W. Kwang-Hua Chu J. Fang 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(3):543-547
Continuum-mechanic derivation of the entrainment of rarefied gases induced by a surface wave along walls (or peristaltic transport)
in a confined parallel-plane microchannel is conducted by the perturbation method. Both no-slip and slip flow cases are investigated
with the former ones matched with the previous approach by Fung and Yih. Critical reflux values due to first order slip-flow
effects become trivial for the free pumping case, and decrease due to second order slip-flow effects after we compared them
with no-slip cases.
Received 27 August 1999 and Received in final form 10 January 2000 相似文献
85.
M. Schöck C. Sürgers H. v. Löhneysen 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(1):1-10
The superconducting and magnetic properties of Nb/Pd1-xFex/Nb triple layers with constant Nb layer thickness dNb=200 ? and different interlayer thicknesses 3 ?≤ dPdFe ≤ ? are investigated. The thickness dependence of the magnetization and of the superconducting transition temperature shows
that for small iron concentration x the Pd1-xFex layer is likely to be in the paramagnetic state for very thin films whereas ferromagnetic order is established for x ≥ 0.13.
The parallel critical field Bc2||(T){B_{c2||}}(T) exhibits a transition from two-dimensional (2D) behavior where the Nb films are coupled across the interlayer, towards a
2D behavior of decoupled Nb films with increasing dPdFeand/or x. This transition allows a determination of the penetration depth xF{\xi _F} of Cooper pairs into the Pd1-xFex layer as a function of x. For samples with a ferromagnetic interlayer xF{\xi _F} is found to be independent of x. 相似文献
86.
A. Chakraborti B.K. Chakrabarti 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(1):167-170
We consider a simple model of a closed economic system where the total money is conserved and the number of economic agents
is fixed. Analogous to statistical systems in equilibrium, money and the average money per economic agent are equivalent to
energy and temperature, respectively. We investigate the effect of the saving propensity of the agents on the stationary or
equilibrium probability distribution of money. When the agents do not save, the equilibrium money distribution becomes the
usual Gibb's distribution, characteristic of non-interacting agents. However with saving, even for individual self-interest,
the dynamics becomes cooperative and the resulting asymmetric Gaussian-like stationary distribution acquires global ordering
properties. Intriguing singularities are observed in the stationary money distribution in the market, as functions of the
marginal saving propensity of the agents.
Received 2 May 2000 相似文献
87.
A. Milekhin N.P. Stepina A.I. Yakimov A.I. Nikiforov S. Schulze D.R.T. Zahn 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(2):355-359
Self-organised Ge dot superlattices grown by molecular beam epitaxy of Ge and Si layers utilizing Stranski-Krastanov growth
mode were investigated by Raman spectroscopy. An average size of Ge quantum dots was obtained from transmission electron microscopy
measurements. The strain and interdiffusion of Ge and Si atoms in Ge quantum dots were estimated from the analysis of frequency
positions of optical phonons observed in the Raman spectra. Raman scattering by folded longitudinal acoustic phonons in the
Ge dot superlattices was observed and explained using of elastic continuum theory.
Received 25 January 2000 相似文献
88.
Ding Changgeng Yang Jinlong Cui Xiangyuan Wang Kelin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(1):123-126
Geometrical and electronic structures of C35X fullerenes with , N and Si as substitutional dopants have been studied. Three non-equivalent sites in the D6h structure of C36 have been considered for the substitution. We have found that the dopant has a strong tendency to substitute at sites where
the carbon atom contributes significantly to the frontier orbitals of C36 and has the weakest interaction with its nearest-neighbor atoms. The relative stability of C35Si and C35B (C35N) has been investigated and high chemical reactivity of C35Si has been predicted.
Received 8 July 1999 and Received in final form 4 October 1999 相似文献
89.
A. Maignan C. Martin M. Hervieu B. Raveau 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(1):41-45
The substitution of manganese for cobalt in the perovskite La
0.8
Sr
0.2
CoO
3
has been studied. A significant increase of the magnetoresistance (MR) is obtained, reaching 60% at 5 K under 7 T for . This behavior originates from a spectacular increase of the resistivity correlated to a significant decrease of ferromagnetism
by Mn doping. This enhancement of magnetoresistance can be interpreted by the growth of ferromagnetic clusters in the insulating
matrix, by applying a magnetic field.
Received 7 May 1999 相似文献
90.
V.I. Zubov N.P. Tretiakov I.V. Zubov 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(4):629-633
From simple topological considerations on the molecular shapes, a new method for calculating the coefficients of the Girifalco
intermolecular potential for various fullerenes is proposed. This eliminates the necessity for fitting the coefficients to
data of measurements for each specific fullerene. We calculate them for C76 and C84 and apply this potential to perform research on the equilibrium of these fullerites with their vapors. The temperature dependence
of the lattice parameters, the saturated vapor pressures and the enthalpies of sublimation is studied. Results are in good
agreement with available experimental data.
Received 13 January 2000 and Received in final form 18 June 2000 相似文献