全文获取类型
收费全文 | 426篇 |
免费 | 36篇 |
国内免费 | 6篇 |
专业分类
化学 | 198篇 |
晶体学 | 2篇 |
力学 | 24篇 |
综合类 | 1篇 |
数学 | 102篇 |
物理学 | 141篇 |
出版年
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 9篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2016年 | 12篇 |
2015年 | 4篇 |
2014年 | 14篇 |
2013年 | 14篇 |
2012年 | 16篇 |
2011年 | 23篇 |
2010年 | 15篇 |
2009年 | 14篇 |
2008年 | 19篇 |
2007年 | 25篇 |
2006年 | 14篇 |
2005年 | 14篇 |
2004年 | 13篇 |
2003年 | 13篇 |
2002年 | 11篇 |
2001年 | 9篇 |
2000年 | 20篇 |
1999年 | 13篇 |
1998年 | 12篇 |
1997年 | 10篇 |
1996年 | 17篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 11篇 |
1992年 | 11篇 |
1991年 | 9篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 9篇 |
1986年 | 3篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 13篇 |
1981年 | 11篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有468条查询结果,搜索用时 31 毫秒
41.
Goodman TNT; Micchelli CA; Rodriguez G; Seatzu S 《IMA Journal of Numerical Analysis》1998,18(3):331-354
It is shown that, under certain conditions, orthonormalizingthe positive integer shifts of an exponentially decaying functionon the half line by the Gram-Schmidt process leads to a limitingprofile given by orthonormalizing all their integer shifts onthe whole line. These results derive from properties of Choleskyfactorization of bi-infinite and semi-infinite matrices. Anexample is provided by the negative exponential function andconjectures are given, supported by numerical evidence, forthe Gaussian and Lorentz function. 相似文献
42.
We explore a Plücker-type relation which occurs naturally in the study of maximally supersymmetric solutions of certain supergravity theories. This relation generalises at the same time the classical Plücker relation and the Jacobi identity for a metric Lie algebra and coincides with the Jacobi identity of a metric n-Lie algebra. In low dimension we present evidence for a geometric characterisation of the relation in terms of middle-dimensional orthogonal planes in Euclidean or Lorentzian inner product spaces. 相似文献
43.
4 Summary A simple hot-wire sensor positioning technique is presented. The technique is easily integrated with a personal computer to achieve a completely automated system. A single initial calibration of the system outside of the test section is all that is necessary and no subsequent manual re-positioning is required during experimentation. This gives the capability of performing multiple measurements of near-wall velocity at different locations on a wall surface without the need of cumbersome and extensive alignment of the traverse system with respect to the wall surface. Preliminary tests indicate that the technique is viable for near-wall velocity measurements. 相似文献
44.
Reis H Loboda O Avramopoulos A Papadopoulos MG Kirtman B Luis JM Zaleśny R 《Journal of computational chemistry》2011,32(5):908-914
Electronic and vibrational nuclear relaxation (NR) contributions to the dipole (hyper)polarizabilities of the endohedral fullerene Li@C(60) and its monovalent cation [Li@C(60)](+) are calculated at the (U)B3LYP level. Many results are new, while others differ significantly from those reported previously using more approximate methods. The properties are compared with those of the corresponding hypothetical noninteracting systems with a valence electron transferred from Li to the cage. Whereas the NR contribution to the static linear polarizabilities is small in comparison with the corresponding electronic property, the opposite is true for the static hyperpolarizabilities. A relatively small, but non-negligible, NR contribution to the dc-Pockels effect is obtained in the infinite frequency approximation. 相似文献
45.
Weakly quasi-threshold graphs form a proper subclass of the well-known class of cographs by restricting the join operation. In this paper we characterize weakly quasi-threshold graphs by a finite set of forbidden subgraphs: the class of weakly quasi-threshold graphs coincides with the class of {P 4, co-(2P 3)}-free graphs. Moreover we give the first linear-time algorithm to decide whether a given graph belongs to the class of weakly quasi-threshold graphs, improving the previously known running time. Based on the simplicity of our recognition algorithm, we can provide certificates of membership (a structure that characterizes weakly quasi-threshold graphs) or non-membership (forbidden induced subgraphs) in additional ${{\mathcal O}(n)}$ time. Furthermore we give a linear-time algorithm for finding the largest induced weakly quasi-threshold subgraph in a cograph. 相似文献
46.
P.D. Draggiotis R.H.P. Kleiss A. Lazopoulos C.G. Papadopoulos 《The European Physical Journal C - Particles and Fields》2006,46(3):741-750
We present a proof of the Britto–Cachazo–Feng–Witten tree-level recursion relation for gluon amplitudes in QCD, based on a
direct equivalence between BCFW decompositions and Feynman diagrams. We demonstrate that this equivalence can be made explicit
when working in a convenient gauge. We exhibit that gauge invariance and the particular structure of Yang–Mills vertices guarantee
the validity of the BCFW construction. 相似文献
47.
Let 0<n1<n2<...<nN be N distinct integers, and leta1, a2, ..., aN be complex numbers. We set [formula] and [formula] There are two well-known problems concerning the case a1=a2=...=aN=1.1991 Mathematics Subject Classification 42A05. 相似文献
48.
Kai Johannes Keller Nikolaos A. Papadopoulos Andrés F. Reyes-Lega 《Mathematische Semesterberichte》2008,47(10):149-160
The aim of this paper is to give a simple, geometric proof of Wigner’s theorem on the realization
of symmetries in quantum mechanics that clarifies its relation to projective geometry. Although several
proofs exist already, it seems that the relevance of Wigner’s theorem is not fully appreciated in general.
It is Wigner’s theorem which allows the use of linear realizations of symmetries and therefore guarantees
that, in the end, quantum theory stays a linear theory. In the present paper, we take a strictly geometrical
point of view in order to prove this theorem. It becomes apparent that Wigner’s theorem is nothing else
but a corollary of the fundamental theorem of projective geometry. In this sense, the proof presented here
is simple, transparent and therefore accessible even to elementary treatments in quantum mechanics. 相似文献
49.
50.
The association constants and molar conductivities, extrapolated to zero concentration, have been determined for 3,5-dinitrosalicylic and 5-fluorosalicylic acids in water-methanol mixtures at 25 degrees . 相似文献