全文获取类型
收费全文 | 7350篇 |
免费 | 781篇 |
国内免费 | 685篇 |
专业分类
化学 | 871篇 |
晶体学 | 34篇 |
力学 | 906篇 |
综合类 | 141篇 |
数学 | 4800篇 |
物理学 | 2064篇 |
出版年
2024年 | 9篇 |
2023年 | 93篇 |
2022年 | 191篇 |
2021年 | 166篇 |
2020年 | 242篇 |
2019年 | 225篇 |
2018年 | 220篇 |
2017年 | 267篇 |
2016年 | 240篇 |
2015年 | 172篇 |
2014年 | 303篇 |
2013年 | 574篇 |
2012年 | 353篇 |
2011年 | 454篇 |
2010年 | 387篇 |
2009年 | 550篇 |
2008年 | 533篇 |
2007年 | 497篇 |
2006年 | 433篇 |
2005年 | 404篇 |
2004年 | 330篇 |
2003年 | 304篇 |
2002年 | 266篇 |
2001年 | 223篇 |
2000年 | 207篇 |
1999年 | 192篇 |
1998年 | 206篇 |
1997年 | 155篇 |
1996年 | 118篇 |
1995年 | 72篇 |
1994年 | 62篇 |
1993年 | 50篇 |
1992年 | 50篇 |
1991年 | 42篇 |
1990年 | 27篇 |
1989年 | 25篇 |
1988年 | 25篇 |
1987年 | 23篇 |
1986年 | 19篇 |
1985年 | 13篇 |
1984年 | 20篇 |
1983年 | 5篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1978年 | 11篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1972年 | 3篇 |
排序方式: 共有8816条查询结果,搜索用时 15 毫秒
51.
Let E
n:y
2=x
3−n
2
x denote the family of congruent number elliptic curves. Feng and Xiong (2004) equate the nontriviality of the Selmer groups
associated with E
n
to the presence of certain types of partitions of graphs associated with the prime factorization of n. In this paper, we extend the ideas of Feng and Xiong in order to compute the Selmer groups of E
n.
2000 Mathematics Subject Classification Primary—11G05; Secondary—14H52, 14H25, 05C90 相似文献
52.
Eckhard Steffen 《Discrete Mathematics》2004,280(1-3):191-214
Cubic bridgeless graphs with chromatic index four are called uncolorable. We introduce parameters measuring the uncolorability of those graphs and relate them to each other. For k=2,3, let ck be the maximum size of a k-colorable subgraph of a cubic graph G=(V,E). We consider r3=|E|−c3 and
. We show that on one side r3 and r2 bound each other, but on the other side that the difference between them can be arbitrarily large. We also compare them to the oddness ω of G, the smallest possible number of odd circuits in a 2-factor of G. We construct cyclically 5-edge connected cubic graphs where r3 and ω are arbitrarily far apart, and show that for each 1c<2 there is a cubic graph such that ωcr3. For k=2,3, let ζk denote the largest fraction of edges that can be k-colored. We give best possible bounds for these parameters, and relate them to each other. 相似文献
53.
We show that the tensor product B-spline basis and the triangular Bernstein basis are in some sense best conditioned among all nonnegative bases for the spaces of tensor product splines and multivariate polynomials, respectively. We also introduce some new condition numbers which are analogs of component-wise condition numbers for linear systems introduced by Skeel. 相似文献
54.
David S. Dummit Brett A. Tangedal Paul B. van Wamelen. 《Mathematics of Computation》2004,73(247):1525-1546
Systematic computation of Stark units over nontotally real base fields is carried out for the first time. Since the information provided by Stark's conjecture is significantly less in this situation than the information provided over totally real base fields, new techniques are required. Precomputing Stark units in relative quadratic extensions (where the conjecture is already known to hold) and coupling this information with the Fincke-Pohst algorithm applied to certain quadratic forms leads to a significant reduction in search time for finding Stark units in larger extensions (where the conjecture is still unproven). Stark's conjecture is verified in each case for these Stark units in larger extensions and explicit generating polynomials for abelian extensions over complex cubic base fields, including Hilbert class fields, are obtained from the minimal polynomials of these new Stark units.
56.
极紫外望远镜各通道夹角的测量 总被引:1,自引:1,他引:0
极紫外望远镜是由四个单通道的望远镜捆绑在一起,以便同时对太阳的相同部分观测,由于受地面装调以及发射过程中的影响,无法保证四个通道光轴严格平行,必然带来观测位置上的误差。只要测出各通道之间的光轴夹角,便可在像面上采取适当的处理方法,以便减小这种误差,但这一夹角的测量精度必须控制在0.1″内。为达到如此高的精度,采用了太阳局部边缘探测的方法,很好地解决了这一问题。 相似文献
57.
介绍未确知数学方法,并用未确知数学方法分析处理物理实验数据,与传统的数据处理方法比较,未确知数学方法不必对数据作任何假设,因此更合理,也更符合实际。 相似文献
58.
Monique Laurent 《Mathematical Programming》2007,109(2-3):239-261
We give a hierarchy of semidefinite upper bounds for the maximum size A(n,d) of a binary code of word length n and minimum distance at least d. At any fixed stage in the hierarchy, the bound can be computed (to an arbitrary precision) in time polynomial in n; this is based on a result of de Klerk et al. (Math Program, 2006) about the regular ∗-representation for matrix ∗-algebras.
The Delsarte bound for A(n,d) is the first bound in the hierarchy, and the new bound of Schrijver (IEEE Trans. Inform. Theory 51:2859–2866, 2005) is located
between the first and second bounds in the hierarchy. While computing the second bound involves a semidefinite program with
O(n
7) variables and thus seems out of reach for interesting values of n, Schrijver’s bound can be computed via a semidefinite program of size O(n
3), a result which uses the explicit block-diagonalization of the Terwilliger algebra. We propose two strengthenings of Schrijver’s
bound with the same computational complexity.
Supported by the Netherlands Organisation for Scientific Research grant NWO 639.032.203. 相似文献
59.
60.
V. P. Maslov 《Theoretical and Mathematical Physics》2007,150(1):102-122
From the standpoint of thermodynamic averaging of fission microprocesses, we investigate the origin of radioactive release
in an NPP after an accident or after resource depletion. The genesis of the NPP release is interpreted as a new thermodynamic
phenomenon, a zeroth-order phase transition. This problem setting results in a problem in probabilistic number theory. We
prove the corresponding theorem leading to quantization of the Zipf law for the frequency of a zeroth-order phase transition
with different values of the jump of the Gibbs thermodynamic potential. We introduce the notion of hole dimension.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 150, No. 1, pp. 118–142, January, 2007. 相似文献