全文获取类型
收费全文 | 27647篇 |
免费 | 972篇 |
国内免费 | 99篇 |
专业分类
化学 | 17437篇 |
晶体学 | 207篇 |
力学 | 591篇 |
数学 | 4737篇 |
物理学 | 5746篇 |
出版年
2023年 | 174篇 |
2022年 | 241篇 |
2021年 | 386篇 |
2020年 | 492篇 |
2019年 | 505篇 |
2018年 | 420篇 |
2017年 | 431篇 |
2016年 | 999篇 |
2015年 | 835篇 |
2014年 | 955篇 |
2013年 | 1739篇 |
2012年 | 1508篇 |
2011年 | 1765篇 |
2010年 | 1082篇 |
2009年 | 924篇 |
2008年 | 1318篇 |
2007年 | 1236篇 |
2006年 | 1108篇 |
2005年 | 980篇 |
2004年 | 882篇 |
2003年 | 763篇 |
2002年 | 743篇 |
2001年 | 421篇 |
2000年 | 387篇 |
1999年 | 375篇 |
1998年 | 337篇 |
1997年 | 330篇 |
1996年 | 362篇 |
1995年 | 335篇 |
1994年 | 297篇 |
1993年 | 290篇 |
1992年 | 287篇 |
1991年 | 248篇 |
1990年 | 239篇 |
1989年 | 241篇 |
1988年 | 227篇 |
1987年 | 210篇 |
1986年 | 194篇 |
1985年 | 270篇 |
1984年 | 260篇 |
1983年 | 212篇 |
1982年 | 237篇 |
1981年 | 240篇 |
1980年 | 227篇 |
1979年 | 227篇 |
1978年 | 253篇 |
1977年 | 211篇 |
1976年 | 179篇 |
1975年 | 193篇 |
1974年 | 178篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Gašper Jaklič Jernej Kozak Marjeta Krajnc Vito Vitrih Emil Žagar 《Numerical Algorithms》2007,45(1-4):49-60
In this paper, three-pencil lattices on triangulations are studied. The explicit representation of a lattice, based upon barycentric
coordinates, enables us to construct lattice points in a simple and numerically stable way. Further, this representation carries
over to triangulations in a natural way. The construction is based upon group action of S
3 on triangle vertices, and it is shown that the number of degrees of freedom is equal to the number of vertices of the triangulation.
相似文献
102.
Motivated by Gauss's first proof of the Fundamental Theorem of Algebra, we study the topology of harmonic algebraic curves.
By the maximum principle, a harmonic curve has no bounded components; its topology is determined by the combinatorial data
of a noncrossing matching. Similarly, every complex polynomial gives rise to a related combinatorial object that we call a
basketball, consisting of a pair of noncrossing matchings satisfying one additional constraint. We prove that every noncrossing
matching arises from some harmonic curve, and deduce from this that every basketball arises from some polynomial. 相似文献
103.
Abull is the (self-complementary) graph with verticesa, b, c, d, e and edgesab, ac, bc, bd, ce; a graphG is calledBerge if neitherG not its complement contains a chordless cycle whose length is odd and at least five. We prove that bull-free Berge graphs are perfect; a part of our argument relies on a new property of minimal imperfect graphs.This work was done while both authors were at the School of Computer Science, McGill University; support by NSERC is gratefully acknowledged. 相似文献
104.
Andrew S. Zektzer Gary E. Martin Raymond N. Castle 《Journal of heterocyclic chemistry》1987,24(3):879-884
Phenanthro[3,4:3′,4′]phenanthro[2,1-b]thiophene ( 1 ) served as the model system to evaluate two-dimensional proton zero quantum coherence nmr in order to establish the vicinal proton-proton connectivities. The utility of the two-dimensional proton zero quantum nmr experiment has been compared with the utility of the traditional autocorrelated proton-proton (COSY) experiment. In the case of a molecule such as 1 , where the proton chemical shifts are so highly congested, the zero quantum coherence experiment provides data not obtainable from the COSY experiment. 相似文献
105.
We give a self‐contained proof of the preservation theorem for proper countable support iterations known as “tools‐preservation”, “Case A” or “first preservation theorem” in the literature. We do not assume that the forcings add reals. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
106.
107.
A. Janušauskas 《Lithuanian Mathematical Journal》1996,36(1):22-31
Institute of Mathematics and Informatics. Akademijos 4, 2600 Vilnius, Lithuania. Translated from Lietuvos Matematikos Rinkinys.
Vol. 36, No. 1, pp. 27–38, January–March,. 1996. 相似文献
108.
109.
We prove that the Mellin transform of a function log-concave (convex) is, after division by (+1), where is the argument of the transform, itself log-concave (convex) in . This theorem is first applied to the moments of the ground state wave function of the Schrödinger equation where the Laplacian of the central potential has a given sign, and generalized to other situations. This is used to derive inequalities linking thel
th derivative of the ground state wave function at the origin for angular momentuml and the expectation value of the kinetic energy, and applied to quarkonium physics. A generalization to higher radial excitations is shown to be plausible by using the WKB approximation. Finally, new bounds on ground-state energies in power potentials are obtained. 相似文献
110.
Martin Bordemann 《Communications in Mathematical Physics》1990,135(1):201-216
We generalize the usual Lax equationd/dt L=[M, L] byd/dt L=–(M)L, where is an arbitrary representation of a Lie algebra g (the values ofM) in a representation spaceV (the values ofL). The usual classicalr-matrix programme for Hamiltonian integrable systems is generalized tor-matrices taking values in gV. Ther-matrices are then considered as left invariant torsion-free covariant derivatives on a Lie groupK (with Lie algebraV
*). The Classical Yang-Baxter Equation (CYBE) is equivalent to the flatness ofK whereas the Modified CYBE implies thatK is an affine locally symmetric space. An example is discussed. 相似文献