全文获取类型
收费全文 | 337828篇 |
免费 | 2770篇 |
国内免费 | 884篇 |
专业分类
化学 | 162032篇 |
晶体学 | 5036篇 |
力学 | 16557篇 |
综合类 | 2篇 |
数学 | 50590篇 |
物理学 | 107265篇 |
出版年
2020年 | 1764篇 |
2019年 | 2037篇 |
2018年 | 10974篇 |
2017年 | 11783篇 |
2016年 | 7782篇 |
2015年 | 3435篇 |
2014年 | 4009篇 |
2013年 | 11265篇 |
2012年 | 12246篇 |
2011年 | 22149篇 |
2010年 | 13530篇 |
2009年 | 13499篇 |
2008年 | 19308篇 |
2007年 | 22852篇 |
2006年 | 8549篇 |
2005年 | 14616篇 |
2004年 | 10404篇 |
2003年 | 9530篇 |
2002年 | 7507篇 |
2001年 | 7355篇 |
2000年 | 5660篇 |
1999年 | 4248篇 |
1998年 | 3592篇 |
1997年 | 3593篇 |
1996年 | 3455篇 |
1995年 | 3228篇 |
1994年 | 3029篇 |
1993年 | 3071篇 |
1992年 | 3359篇 |
1991年 | 3401篇 |
1990年 | 3211篇 |
1989年 | 3172篇 |
1988年 | 3245篇 |
1987年 | 3107篇 |
1986年 | 2996篇 |
1985年 | 4062篇 |
1984年 | 4244篇 |
1983年 | 3476篇 |
1982年 | 3828篇 |
1981年 | 3720篇 |
1980年 | 3594篇 |
1979年 | 3643篇 |
1978年 | 3882篇 |
1977年 | 3627篇 |
1976年 | 3864篇 |
1975年 | 3435篇 |
1974年 | 3555篇 |
1973年 | 3898篇 |
1972年 | 2363篇 |
1971年 | 1807篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
971.
The mass spectrum ofcb meson is investigated with an effective quark-antiquark potential of the form -αc/r +Ar
νwith ν varying from 0.5 to 2.0. TheS andP-wave masses, pseudoscalar decay constant, weak decay partial widths in spectator model and the lifetime ofB
cmeson are computed. The properties calculated here are found to be in good agreement with other theoretical and experimental
values at potential index,ν = 1 相似文献
972.
For fairly high concentrations, the effective arsenic diffusioncoefficient is known to grow linearly with the concentration.In this paper, we consider the strongly enhanced diffusion ofarsenic by asymptotic methods, and extend the results of a previouspaper (King & Please, 1987) in three ways: we characterizean additional (low-concentration) region; we consider the influenceof the initial data; and we consider the case of constant surfaceconcentration. 相似文献
973.
Jian Ming ZHAN Bijan DAVVAZ K. P. SHUM 《数学学报(英文版)》2007,23(8):1345-1356
We describe the relationship between the fuzzy sets and the algebraic hyperstructures. In fact, this paper is a continuation of the ideas presented by Davvaz in (Fuzzy Sets Syst., 117: 477- 484, 2001) and Bhakat and Das in (Fuzzy Sets Syst., 80: 359-368, 1996). The concept of the quasicoincidence of a fuzzy interval value with an interval-valued fuzzy set is introduced and this is a natural generalization of the quasi-coincidence of a fuzzy point in fuzzy sets. By using this new idea, the concept of interval-valued (α,β)-fuzzy sub-hypermodules of a hypermodule is defined. This newly defined interval-valued (α,β)-fuzzy sub-hypermodule is a We shall study such fuzzy sub-hypermodules and sub-hypermodules of a hypermodule. generalization of the usual fuzzy sub-hypermodule. consider the implication-based interval-valued fuzzy 相似文献
974.
R.S. Kraußhar 《Journal of Mathematical Analysis and Applications》2007,325(1):359-376
In this paper we study Clifford and harmonic analysis on some examples of conformal flat manifolds that have a spinor structure, or more generally, at least a pin structure. The examples treated here are manifolds that can be parametrized by U/Γ where U is a subdomain of either Sn or Rn and Γ is a Kleinian group acting discontinuously on U. The examples studied here include RPn and the Hopf manifolds S1×Sn−1. Also some hyperbolic manifolds will be treated. Special kinds of Clifford-analytic automorphic forms associated to the different choices of Γ are used to construct explicit Cauchy kernels, Cauchy integral formulas, Green's kernels and formulas together with Hardy spaces and Plemelj projection operators for Lp spaces of hypersurfaces lying in these manifolds. 相似文献
975.
We prove that for any given c, 1 < c < 17/11, almost all natural numbers are representable in the form [x
c] + [p
c], where x is a natural number and p is a prime. 相似文献
976.
U. Täuber C.E.M. Carvalho R.F. dos Santos C.G. Carvalhaes C.E. Fellows 《Applied physics. B, Lasers and optics》2007,87(3):475-481
A six level rate equation system was used to investigate the impact of photodepletion to amplified spontaneous emission (ASE)
of intramolecular proton-transfer (IPT) dyes incorporated into polymeric hosts. The model includes the most important transitions
for the normal and tautomer form of the molecule as well as intersystem crossing and triplet–triplet transitions. The experimentally
observed pulse shape as well as photodepletion phenomena, i.e. a first order exponential decay of the ASE intensity and a
shortening in ASE pulse width, have been simulated successfully. Additionally, the model was used to propose an explanation
of the unexpected high photodepletion of proton-transfer dyes in solids. The results show that the emission cross section
and reabsorption cross section of the tautomer form of the molecule are the most important parameter not only for efficiency
but also for photodepletion. The model was tested by comparison with experimental results of 2-(2’-hydroxyphenyl)benzimidazole
in polymethylmethacrylate (PMMA), polystyrene (PS) and a 1:1 alternating copolymer matrix PS-co-PMMA.
PACS 78.45.th; 42.55.Mv; 42.70.Jk 相似文献
977.
Joseph M. Ling 《Discrete and Computational Geometry》2007,37(3):455-469
In this paper we prove four new (infinite) lists of quadratic inequalities, and four cubic inequalities, for the flag f-vectors
of 4-polytopes. These extend and supplement the only four currently known non-linear inequalities, which were proved by Bayer
in 1987. The new lists of inequalities for flag f-vectors yield new lists of inequalities for
f-vectors of 4-polytopes. Using the latter, we managed to improve an estimate discovered by Hoppner and Ziegler concerning
upper bounds of f1 in terms of f0 and f3. 相似文献
978.
R. Hart P. Hue D. Burton G. F. Robertshaw F. G. H. Tate L. A. Warren und P. Eisenstein 《Fresenius' Journal of Analytical Chemistry》1938,115(7-8):272-274
Ohne Zusammenfassung 相似文献
979.
980.
R. M. Hitchens 《Fresenius' Journal of Analytical Chemistry》1938,113(1-2):70
Ohne Zusammenfassung 相似文献