全文获取类型
收费全文 | 3066篇 |
免费 | 490篇 |
国内免费 | 212篇 |
专业分类
化学 | 639篇 |
晶体学 | 13篇 |
力学 | 293篇 |
综合类 | 44篇 |
数学 | 1489篇 |
物理学 | 1290篇 |
出版年
2024年 | 2篇 |
2023年 | 24篇 |
2022年 | 43篇 |
2021年 | 44篇 |
2020年 | 77篇 |
2019年 | 89篇 |
2018年 | 88篇 |
2017年 | 104篇 |
2016年 | 126篇 |
2015年 | 112篇 |
2014年 | 164篇 |
2013年 | 245篇 |
2012年 | 158篇 |
2011年 | 205篇 |
2010年 | 158篇 |
2009年 | 209篇 |
2008年 | 202篇 |
2007年 | 221篇 |
2006年 | 193篇 |
2005年 | 193篇 |
2004年 | 151篇 |
2003年 | 132篇 |
2002年 | 138篇 |
2001年 | 114篇 |
2000年 | 104篇 |
1999年 | 88篇 |
1998年 | 93篇 |
1997年 | 56篇 |
1996年 | 44篇 |
1995年 | 35篇 |
1994年 | 21篇 |
1993年 | 27篇 |
1992年 | 12篇 |
1991年 | 13篇 |
1990年 | 10篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 10篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有3768条查询结果,搜索用时 15 毫秒
961.
Well‐balanced finite difference weighted essentially non‐oscillatory schemes for the blood flow model
下载免费PDF全文
![点击此处可从《国际流体数值方法杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The blood flow model maintains the steady‐state solutions, in which the flux gradients are non‐zero but exactly balanced by the source term. In this paper, we design high order finite difference weighted essentially non‐oscillatory (WENO) schemes to this model with such well‐balanced property and at the same time keeping genuine high order accuracy. Rigorous theoretical analysis as well as extensive numerical results all indicate that the resulting schemes verify high order accuracy, maintain the well‐balanced property, and keep good resolution for smooth and discontinuous solutions. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
962.
Petr Čársky 《International journal of quantum chemistry》2007,107(1):56-62
An efficient way of calculation is presented for matrix elements between two plane waves interacting with a molecular Coulombic field. In concurrence with the absolute value of the momentum transfer vector, K = k1 ? k 2 , the most effective method of calculation is selected. The case of K = 0 requires special treatment. For 0 < |K| ≤ 0.3, it is profitable to evaluate the integrals by means of the multipole expansion, and for |K| > 0.3 the density fitting can be applied. For the large |K| the electronic part of the integral is much smaller than the nuclear part and the integral may be approximated by the nuclear contribution only. Some examples for testing the accuracy and time saved are presented. The primary purpose of this paper is to accelerate electron scattering calculations, but it also may be profitable for the electronic structure theory in attempts to use mixed Gaussian and plane‐wave basis sets. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
963.
964.
SangDongKIM ByeongChunSHIN 《计算数学(英文版)》2003,21(2):113-124
The bounds for the eigenvalues of the stiffness matrices in the finite element discretiza-tion corresponding to Lu:=-u″with zero boundary conditions by quadratic hierarchical basic are shown explicitly.The condition numberof the resulting system behaves like O(1/h)where h is the mesh size.We also analyze a main diagonal preconditioner of the stiffness matrix which reduces the condition number of the preconditioned system to O(1). 相似文献
965.
This paper introduces a new algorithm for solving mixed integer programs. The core of the method is an iterative technique for changing the representation of the original mixed integer optimization problem.
Supported by grants FKZ 0037KD0099 and FKZ 2495A/0028G of the Kultusministerium of Sachsen-Anhalt.Supported by a Gerhard-Hess-Preis and grant WE 1462 of the Deutsche Forschungsgemeinschaft, and by the European DONET program TMR ERB FMRX-CT98-0202.Mathematics Subject Classification (1991):90C11 相似文献
966.
There have been extensive studies on non-uniform Gabor bases and frames in recent years. But interestingly there have not been a single example of a compactly supported orthonormal Gabor basis in which either the frequency set or the translation set is non-uniform. Nor has there been an example in which the modulus of the generating function is not a characteristic function of a set. In this paper, we prove that in the one dimension and if we assume that the generating function g(x) of an orthonormal Gabor basis is supported on an interval, then both the frequency and the translation sets of the Gabor basis must be lattices. In fact, the Gabor basis must be the trivial one in the sense that |g(x)|=c(x) for some fundamental interval of the translation set. We also give examples showing that compactly supported non-uniform orthonormal Gabor bases exist in higher dimensions. 相似文献
967.
We prove that for any fixed the generating function of the projection of the set of integer points in a rational -dimensional polytope can be computed in polynomial time. As a corollary, we deduce that various interesting sets of lattice points, notably integer semigroups and (minimal) Hilbert bases of rational cones, have short rational generating functions provided certain parameters (the dimension and the number of generators) are fixed. It follows then that many computational problems for such sets (for example, finding the number of positive integers not representable as a non-negative integer combination of given coprime positive integers ) admit polynomial time algorithms. We also discuss a related problem of computing the Hilbert series of a ring generated by monomials.
968.
Gangsong Leng 《Proceedings of the American Mathematical Society》2003,131(10):3039-3042
For any -dimensional simplex , we confirm a conjecture of Klamkin and Pook (1988) that there are always at least acute dihedral angles in .
969.
The basis number of a graph G was defined by Schmeichel to be the least integer h such that G has an h-fold basis for its cycle space. He proved that for m, n 5, the basis number b(K
m,n
) of the complete bipartite graph K
m,n
is equal to 4 except for K
6,10, K
5,n
and K
6,n
with n = 5, 6, 7, 8. We determine the basis number of some particular non-planar graphs such as K
5,n
and K
6,n
, n = 5, 6, 7, 8, and r-cages for r = 5, 6, 7, 8, and the Robertson graph. 相似文献
970.
It is known that the pattern containment order on permutations is not a partial well-order. Nevertheless, many naturally defined subsets of permutations are partially well-ordered, in which case they have a strong finite basis property. Several classes are proved to be partially well-ordered under pattern containment. Conversely, a number of new antichains are exhibited that give some insight as to where the boundary between partially well-ordered and not partially well-ordered classes lies. 相似文献