全文获取类型
收费全文 | 60878篇 |
免费 | 6089篇 |
国内免费 | 11500篇 |
专业分类
化学 | 54333篇 |
晶体学 | 2160篇 |
力学 | 712篇 |
综合类 | 460篇 |
数学 | 6335篇 |
物理学 | 14467篇 |
出版年
2024年 | 178篇 |
2023年 | 1063篇 |
2022年 | 1898篇 |
2021年 | 1913篇 |
2020年 | 2059篇 |
2019年 | 1947篇 |
2018年 | 1601篇 |
2017年 | 2025篇 |
2016年 | 2126篇 |
2015年 | 2003篇 |
2014年 | 2592篇 |
2013年 | 5567篇 |
2012年 | 3817篇 |
2011年 | 4094篇 |
2010年 | 3506篇 |
2009年 | 4174篇 |
2008年 | 4077篇 |
2007年 | 4121篇 |
2006年 | 3819篇 |
2005年 | 3371篇 |
2004年 | 3236篇 |
2003年 | 2733篇 |
2002年 | 2519篇 |
2001年 | 1869篇 |
2000年 | 1754篇 |
1999年 | 1421篇 |
1998年 | 1239篇 |
1997年 | 1055篇 |
1996年 | 914篇 |
1995年 | 880篇 |
1994年 | 800篇 |
1993年 | 644篇 |
1992年 | 595篇 |
1991年 | 462篇 |
1990年 | 339篇 |
1989年 | 310篇 |
1988年 | 255篇 |
1987年 | 174篇 |
1986年 | 150篇 |
1985年 | 164篇 |
1984年 | 137篇 |
1983年 | 74篇 |
1982年 | 102篇 |
1981年 | 134篇 |
1980年 | 101篇 |
1979年 | 110篇 |
1978年 | 70篇 |
1977年 | 66篇 |
1976年 | 45篇 |
1973年 | 50篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
Alessandro D'Aprano Camillo La Mesa Noemi Proietti Bianca Sesta Sonia Tatone 《Journal of solution chemistry》1994,23(12):1331-1346
The interactions between octyl--D-glucoside and glycine in water have been investigated by surface tension, viscosity, and density measurements. The results show that the -amino acid causes an unexpected lowering of the critical micellar concentration of octyl--D-glucoside. Such a finding has been interpreted in temss of dipole-dipole interactions between the hydrophilic site of the surfactant and the peptidic cosluttes. From three to seven amino acid molecules have been estimated to be coordinated with each glucoside unity in the micellar state. The research has been extended to glycine oligopeptides and L-lysine. The latter compound has effects similar to those observed with glycine whereas diglycine and triglycine show weaker effects on the micellization process. 相似文献
972.
X. -D. Cao 《Periodica Mathematica Hungarica》1994,28(1):43-54
Let
, wheref(n) is the characteristic function of square-full integers. A formula is proved that can be used to obtain better upper bound estimate for (x). We get (x)=O(x
5/33+), which improves the exponent 11/72 obtained by R. Blasubramania and K. Ramachandra. 相似文献
973.
This paper studies the growth function, with respect to the generating set of edge identifications, of a surface group with fundamental domainD in the hyperbolic plane ann-gon whose angles alternate between /p and /q. The possibilities ofn,p andq for which a torsion-free surface group can have such a fundamental polygon are classified, and the growth functions are computed. Conditions are given for which the denominator of the growth function is a product of cyclotomic polynomials and a Salem polynomial.This work was supported in part by NSF Research Grants. 相似文献
974.
Maria Rosaria Enea 《Geometriae Dedicata》1994,51(3):257-286
In this paper we develop a structure theory of algebraic right distributive quasigroups which correspond to closed and connected conjugacy classes
generating algebraic Fischer groups (in the sense of [6]) such that the mappingx x
–1
ax, fora
, is an automorphism of
(as variety). We also give examples of algebraic Fischer groups where this does not happen. It becomes clear that the class of algebraic right distributive quasigroups has nice properties concerning subquasigroups, normal subquasigroups and direct product.We give a complete classification of one- and two-dimensional as well as of minimal algebraic right distributive quasigroups. 相似文献
975.
We study hölder regularity of minimizers of the functional
, wherep(x) takes only two values and jumps across a Lipschitz surface. No restriction on the two values is imposed.This article was processed by the author using the Springer-Verlag TEX PJourlg macro package 1991. 相似文献
976.
G. Alberti G. Bellettini M. Cassandro E. Presutti 《Journal of statistical physics》1996,82(3-4):743-796
We consider an Ising spin system with Kac potentials in a torus of d,d>-2, and fix the temperature below its Lebowitz-Penrose critical value. We prove that when the Kac scaling parameter vanishes, the log of the probability of an interface becomes proportional to its area and the surface tension, related to the proportionality constant, converges to the van der Waals surface tension. The results are based on the analysis of the rate functionals for Gibbsian large deviations and on the proof that they -converge to the perimeter functional of geometric measure theory (which extends the notion of area). Our considerations include nonsmooth interfaces, proving that the Gibbsian probability of an interface depends only on its area and not on its regularity. 相似文献
977.
Summary In this paper it is proved that, for any positive integern 2, 3 (mod 4),n 7, there exists an incomplete idempotent Schröder quasigroup with one hole of size two IISQ(n, 2) except forn = 10. It is also proved that for any positive integern 0, 1 (mod 4), there exists an idempotent Schröder quasigroup ISQ(n) except forn = 5 and 9. These results completely determine the spectrum of ISQ(n) and provide an application to the packing of a class of edge-coloured block designs.Research supported by NSERC grant A-5320.Research supported by NSFC grant 19231060-2. 相似文献
978.
A. Salam 《Numerical Algorithms》1996,11(1):327-337
The vector -algorithm is obtained from the scalar -algorithm by taking the pseudo-inverse of a vector instead of the inverse of a scalar. Thus the vector -algorithm is known only through its rules contrarily to the scalar -algorithm and some other extrapolation algorithms.The aim of this paper is to provide an algebraic approach to the vector -algorithm. 相似文献
979.
We study the topological structure of all 3-manifolds obtained by surgery along principal fibers of a closed orientable
-manifold. As a consequence, we give alternative proofs of some classical results due to W. Heil and L. Moser. Moreover, we completely specify the Seifert invariants for the considered manifolds. Finally we classify the manifolds obtained by surgery along certain Seifert links and determine geometric presentations of their fundamental groups.Work performed under the auspices of C.N.R. (National Research Council) of Italy and partially supported by Ministero della Ricerca Scientifica e Tecnologica within the projects Geometria Reale e Complessa and Topologia. 相似文献
980.
The purpose of this paper is to establish a conjecture of B. Grünbaum, which states that in every n-polygon P in the plane, n 5, some diagonals intersect in a pattern that defines a new n-polygon (P), such that the product of the cross-rations on the diagonals of P is equal to the product of the corresponding cross-ratios on the diagonals of (P). 相似文献