全文获取类型
收费全文 | 5215篇 |
免费 | 122篇 |
国内免费 | 9篇 |
专业分类
化学 | 3714篇 |
晶体学 | 12篇 |
力学 | 65篇 |
数学 | 852篇 |
物理学 | 703篇 |
出版年
2021年 | 30篇 |
2020年 | 34篇 |
2019年 | 31篇 |
2016年 | 94篇 |
2015年 | 67篇 |
2014年 | 96篇 |
2013年 | 190篇 |
2012年 | 173篇 |
2011年 | 183篇 |
2010年 | 114篇 |
2009年 | 110篇 |
2008年 | 151篇 |
2007年 | 173篇 |
2006年 | 177篇 |
2005年 | 179篇 |
2004年 | 172篇 |
2003年 | 124篇 |
2002年 | 130篇 |
2001年 | 92篇 |
2000年 | 69篇 |
1999年 | 75篇 |
1998年 | 88篇 |
1997年 | 93篇 |
1996年 | 95篇 |
1995年 | 75篇 |
1994年 | 95篇 |
1993年 | 87篇 |
1992年 | 97篇 |
1991年 | 70篇 |
1990年 | 81篇 |
1989年 | 87篇 |
1988年 | 84篇 |
1987年 | 96篇 |
1986年 | 121篇 |
1985年 | 128篇 |
1984年 | 94篇 |
1983年 | 83篇 |
1982年 | 84篇 |
1981年 | 77篇 |
1980年 | 100篇 |
1979年 | 59篇 |
1978年 | 91篇 |
1977年 | 82篇 |
1976年 | 73篇 |
1975年 | 52篇 |
1974年 | 64篇 |
1973年 | 62篇 |
1972年 | 55篇 |
1971年 | 45篇 |
1970年 | 53篇 |
排序方式: 共有5346条查询结果,搜索用时 31 毫秒
11.
12.
Gerhard Starke 《Numerische Mathematik》1997,78(1):103-117
Summary. The convergence rate of Krylov subspace methods for the solution of nonsymmetric systems of linear equations, such as GMRES
or FOM, is studied. Bounds on the convergence rate are presented which are based on the smallest real part of the field of
values of the coefficient matrix and of its inverse. Estimates for these quantities are available during the iteration from
the underlying Arnoldi process. It is shown how these bounds can be used to study the convergence properties, in particular,
the dependence on the mesh-size and on the size of the skew-symmetric part, for preconditioners for finite element discretizations
of nonsymmetric elliptic boundary value problems. This is illustrated for the hierarchical basis and multilevel preconditioners
which constitute popular preconditioning strategies for such problems.
Received May 3, 1996 相似文献
13.
The change of the superstructure of different polyethylenes during uniaxial deformation is investigated. The method used is small-angle scattering with synchrotron radiation. For branched polyethylene (Lupolen 1840D) the whole deformation range is analyzed. Beginning with superstructure of the lamellar cluster type, the superstructure partly disappears on a time scale of a few minutes and the fibrillar structure is built up. The degree of destruction and rebuilding depends on the drawing temperature. For very high molecular weight polyethylene (GUR) a reversible change of the superstructure at higher deformation ratios and at different temperatures is observed. The superstructure of (ethylene—hexene) copolymers (TIPELIN) at high draw ratios depends on the drawing temperature and is almost independent of the side group content. Interfibrillar microcracks parallel to the draw direction are produced in samples with a low side group content for draw ratios λ ≥ 1.5. 相似文献
14.
15.
16.
17.
We derive a complex line integral representation for the
ebyshev norm of periodic spline interpolation operators of odd degree on uniform lattices. Several generalizations are indicated. 相似文献
18.
Gerhard Ströhmer 《Journal of Mathematical Fluid Mechanics》2006,8(1):36-63
This paper is concerned with the question of linear stability of motionless, spherically symmetric equilibrium states of viscous,
barotropic, self-gravitating fluids. We prove the linear asymptotic stability of such equilibria with respect to perturbations
which leave the angular momentum, momentum, mass and the position of the center of gravity unchanged. We also give some decay
estimates for such perturbations, which we derive from resolvent estimates by means of analytic semigroup theory. 相似文献
19.
In 1997 Lampert and Slater introduced parallel knock-out schemes, an iterative process on graphs that goes through several rounds. In each round of this process, every vertex eliminates exactly one of its neighbors. The parallel knock-out number of a graph is the minimum number of rounds after which all vertices have been eliminated (if possible). The parallel knock-out number is related to well-known concepts like perfect matchings, hamiltonian cycles, and 2-factors.We derive a number of combinatorial and algorithmic results on parallel knock-out numbers: for families of sparse graphs (like planar graphs or graphs of bounded tree-width), the parallel knock-out number grows at most logarithmically with the number n of vertices; this bound is basically tight for trees. Furthermore, there is a family of bipartite graphs for which the parallel knock-out number grows proportionally to the square root of n. We characterize trees with parallel knock-out number at most 2, and we show that the parallel knock-out number for trees can be computed in polynomial time via a dynamic programming approach (whereas in general graphs this problem is known to be NP-hard). Finally, we prove that the parallel knock-out number of a claw-free graph is either infinite or less than or equal to 2. 相似文献
20.