全文获取类型
收费全文 | 18412篇 |
免费 | 1115篇 |
国内免费 | 1554篇 |
专业分类
化学 | 6454篇 |
晶体学 | 78篇 |
力学 | 766篇 |
综合类 | 224篇 |
数学 | 9063篇 |
物理学 | 4496篇 |
出版年
2023年 | 217篇 |
2022年 | 398篇 |
2021年 | 406篇 |
2020年 | 379篇 |
2019年 | 442篇 |
2018年 | 423篇 |
2017年 | 436篇 |
2016年 | 462篇 |
2015年 | 399篇 |
2014年 | 644篇 |
2013年 | 1227篇 |
2012年 | 642篇 |
2011年 | 767篇 |
2010年 | 717篇 |
2009年 | 1090篇 |
2008年 | 1209篇 |
2007年 | 1250篇 |
2006年 | 1108篇 |
2005年 | 844篇 |
2004年 | 736篇 |
2003年 | 740篇 |
2002年 | 743篇 |
2001年 | 598篇 |
2000年 | 580篇 |
1999年 | 527篇 |
1998年 | 484篇 |
1997年 | 368篇 |
1996年 | 257篇 |
1995年 | 207篇 |
1994年 | 189篇 |
1993年 | 176篇 |
1992年 | 255篇 |
1991年 | 140篇 |
1990年 | 111篇 |
1989年 | 85篇 |
1988年 | 102篇 |
1987年 | 96篇 |
1986年 | 83篇 |
1985年 | 86篇 |
1984年 | 95篇 |
1983年 | 54篇 |
1982年 | 106篇 |
1981年 | 177篇 |
1980年 | 201篇 |
1979年 | 191篇 |
1978年 | 175篇 |
1977年 | 114篇 |
1976年 | 114篇 |
1973年 | 79篇 |
1972年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
161.
J. M. Kumpula J. Saramäki K. Kaski J. Kertész 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(1):41-45
According to Fortunato and Barthélemy, modularity-based community detection
algorithms have a resolution threshold such that small communities in a large
network are invisible. Here we generalize their work and show that the q-state
Potts community detection method introduced by Reichardt and Bornholdt
also has a resolution threshold. The model contains a parameter by which this threshold can be tuned, but no a priori principle
is known to select the proper value.
Single global optimization criteria do not seem capable for detecting all
communities if their size distribution is broad. 相似文献
162.
Alexander J. Zaslavski 《Journal of Mathematical Analysis and Applications》2007,335(2):962-973
The Tonelli existence theorem in the calculus of variations and its subsequent modifications were established for integrands f which satisfy convexity and growth conditions. In this paper we consider a large class of optimal control problems which is identified with a complete metric space of integrands without convexity assumptions and show that for a generic integrand the corresponding optimal control problem possesses a unique solution and this solution is Lipschitzian. 相似文献
163.
胡长松 《应用泛函分析学报》2007,9(2):153-157
设E是Banach空间,T∶E→2E*是极大单调算子,T-10≠ф.令x0∈E,yn=(J λnT)-1xn en,xn 1=J-1(αnJxn (1-αn)Jyn),n0,λn>0,αn∈[0,1],文章研究了{xn}收敛性. 相似文献
164.
Martin I. Karakhanyan 《Journal of Contemporary Mathematical Analysis (Armenian Academy of Sciences)》2007,42(3):146-150
The paper proves some general facts on commutators that refer to Fuglede-Putnam classical theorem in the spectral theory of not necessarily selfadjoint operators. 相似文献
165.
L. Bartosch P. Kopietz 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(1):29-36
We consider the effect of Coulomb interactions on the average density of states (DOS) of disordered low-dimensional metals
for temperatures T and frequencies ω smaller than the inverse elastic life-time 1/τ. Using the fact that long-range Coulomb interactions in two dimensions (2d) generate ln2-singularities in the DOS ν(ω) but only ln-singularities in the conductivity σ(ω), we can re-sum the most singular contributions
to the average DOS via a simple gauge-transformation. If σ(ω) > 0, then a metallic Coulomb gapν(ω) ∝ |ω|/e
4 appears in the DOS at T = 0 for frequencies below a certain crossover frequency Ω
2 which depends on the value of the DC conductivity σ(0). Here, - e is the charge of the electron. Naively adopting the same procedure to calculate the DOS in quasi 1d metals, we find ν(ω) ∝ (|ω|/Ω
1)1/2exp(- Ω
1/|ω|) at T = 0, where Ω
1 is some interaction-dependent frequency scale. However, we argue that in quasi 1d the above gauge-transformation method is on less firm grounds than in 2d. We also discuss the behavior of the DOS at finite temperatures and give numerical results for the expected tunneling conductance
that can be compared with experiments.
Received 28 August 2001 / Received in final form 28 January 2002 Published online 9 July 2002 相似文献
166.
设Λ={λn}n∞=1为正的实数数列,且当n→∞时,有λn↘0.本文给出了当λn≤Mn-1/2,n=1,2,…,(其中M>0为一正常数)时Müntz系统{xλn}的有理函数在Lp[0,1]空间的逼近速度,主要结论为Rn(f,Λ) Lp≤CMω(f,n-1/2)Lp,1≤p≤∞. 相似文献
167.
Wengu Chen Yixin Lai 《分析论及其应用》2006,22(2):195-200
Let μ be a Borel measure on Rd which may be non doubling. The only condition that μ must satisfy is μ(Q) ≤ col(Q)n for any cube Q () Rd with sides parallel to the coordinate axes and for some fixed n with 0 < n ≤ d. The purpose of this paper is to obtain a boundedness property of fractional integrals in Hardy spaces H1 (μ). 相似文献
168.
A number of generalized metric spaces have been defined or characterized in terms of g-functions. Symmetric g-functions are discussed by C. Good, D. Jennings and A. M. Mohamad. In this paper, some questions about symmetric g-functions are answered, particularly it is shown that every sym-wg-space is expandable.
The project is supported by the NNSF (10571151) and NSF (2006J0397) of Fujian Province of China. 相似文献
169.
V. S. Klimov 《Mathematical Notes》2007,81(1-2):61-71
We study homology characteristics of critical values and extremals of Lipschitz functionals defined on bounded closed convex subsets of a reflexive space that are invariant under deformations. Sufficient conditions for the existence of a bifurcation point of a multivalued potential operator (the switch principle for the typical number of an extremal) are established. 相似文献
170.
Yu. Gangrsky 《Hyperfine Interactions》2006,171(1-3):203-208
This review summarizes the experimental data on charge radii differences among ground state and high spin isomeric states
determined by high-resolution laser spectroscopic methods. A comparison is presented between radii changes obtained from the
isomeric shifts in the atomic spectra and from the quadrupole moments of both ground and isomeric states under the assumption
that the radii changes are determined by the difference of the quadrupole deformations. Special attention is paid to isomers
arising from the break-up of nucleon pairs and isomers of odd–odd nuclei. The characteristic features of the radii changes
for isomeric states of different origin are discussed. 相似文献