全文获取类型
收费全文 | 15957篇 |
免费 | 1539篇 |
国内免费 | 1775篇 |
专业分类
化学 | 1113篇 |
晶体学 | 37篇 |
力学 | 1109篇 |
综合类 | 373篇 |
数学 | 13776篇 |
物理学 | 2863篇 |
出版年
2024年 | 23篇 |
2023年 | 164篇 |
2022年 | 203篇 |
2021年 | 286篇 |
2020年 | 327篇 |
2019年 | 383篇 |
2018年 | 379篇 |
2017年 | 470篇 |
2016年 | 458篇 |
2015年 | 364篇 |
2014年 | 679篇 |
2013年 | 1115篇 |
2012年 | 658篇 |
2011年 | 818篇 |
2010年 | 790篇 |
2009年 | 1037篇 |
2008年 | 1101篇 |
2007年 | 1226篇 |
2006年 | 1037篇 |
2005年 | 977篇 |
2004年 | 743篇 |
2003年 | 780篇 |
2002年 | 719篇 |
2001年 | 607篇 |
2000年 | 673篇 |
1999年 | 559篇 |
1998年 | 533篇 |
1997年 | 463篇 |
1996年 | 313篇 |
1995年 | 197篇 |
1994年 | 201篇 |
1993年 | 134篇 |
1992年 | 109篇 |
1991年 | 99篇 |
1990年 | 79篇 |
1989年 | 46篇 |
1988年 | 59篇 |
1987年 | 36篇 |
1986年 | 33篇 |
1985年 | 61篇 |
1984年 | 54篇 |
1983年 | 22篇 |
1982年 | 49篇 |
1981年 | 33篇 |
1980年 | 34篇 |
1979年 | 30篇 |
1978年 | 29篇 |
1977年 | 22篇 |
1976年 | 12篇 |
1974年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
961.
Banach空间中微分方程解的存在与唯一性 总被引:6,自引:0,他引:6
在一般Banach空间中,作者讨论了微分方程的初值问题u=f(t,u),u(0)=x0.在比文[6]中弱Carathodory条件更弱的情况下,不仅放宽了[6]中的一个重要不等式条件,还去掉了另一与之相关的不等式限制,仍获得了初值问题解的存在与唯一性及解的迭代逼近.对周期边值问题也获得了类似结果. 相似文献
962.
Chi-Kwong Li 《Journal of Mathematical Analysis and Applications》2008,348(2):843-855
For a positive integer k, the rank-k numerical range Λk(A) of an operator A acting on a Hilbert space H of dimension at least k is the set of scalars λ such that PAP=λP for some rank k orthogonal projection P. In this paper, a close connection between low rank perturbation of an operator A and Λk(A) is established. In particular, for 1?r<k it is shown that Λk(A)⊆Λk−r(A+F) for any operator F with rank(F)?r. In quantum computing, this result implies that a quantum channel with a k-dimensional error correcting code under a perturbation of rank at most r will still have a (k−r)-dimensional error correcting code. Moreover, it is shown that if A is normal or if the dimension of A is finite, then Λk(A) can be obtained as the intersection of Λk−r(A+F) for a collection of rank r operators F. Examples are given to show that the result fails if A is a general operator. The closure and the interior of the convex set Λk(A) are completely determined. Analogous results are obtained for Λ∞(A) defined as the set of scalars λ such that PAP=λP for an infinite rank orthogonal projection P. It is shown that Λ∞(A) is the intersection of all Λk(A) for k=1,2,…. If A−μI is not compact for all μ∈C, then the closure and the interior of Λ∞(A) coincide with those of the essential numerical range of A. The situation for the special case when A−μI is compact for some μ∈C is also studied. 相似文献
963.
MATLAB在空间图形中的动态应用 总被引:1,自引:0,他引:1
Ren Minghui 《数学理论与应用》2008,(1)
学生空间思维的不足影响了学生对空间曲面的理解和重积分的学习。本文通过二个实例,重点讨论了用MATLAB动态生成空间图形的技巧。 相似文献
964.
In recent years, the research in integral equations in Banach spaces has achieved many results (refer to [1], [2], [3] etc.). It is well known that, generally, one must first establish the comparison theorem before applying the method of (coupled) lower and upper (quasi)solutions to investigate the (quasi)solutions of integral equations. This can be easily done for Volterra integral equations, but seems impossible for the cases of Fredholm type. Though [3] avoided the establishment of… 相似文献
965.
Leslie C. Cheng 《数学学报(英文版)》2008,24(6):1031-1038
We establish the L^p boundedness of Marcinkiewicz integral operators with kernels in theHardy space on a compact submanifold of finite type. Previously such boundedness properties were obtained when the submanifold is a sphere. Our result shows that what matters is not the symmetry, but a certain type of curvature property of the submanifold. 相似文献
966.
本文讨论赋$\beta$-范空间中的最佳逼近问题.以[1]引进的共轭锥为工具,借助[2]中关于$\beta$-次半范的Hahn-Banach延拓定理,第二节给出赋$\beta$-范空间的闭子空间中最佳逼近元的特征,第三节得到赋$\beta$-范空间中任何凸子集或子空间均为半Chebyshev集的充要条件是空间本身严格凸,文章最后证明了严格凸的赋$\beta$-范空间中任何有限维子空间都是Chebyshev集. 相似文献
967.
Ozer TALO Feyzi BASAR 《数学学报(英文版)》2008,24(7):1205-1212
Recently, the space bvp of real or complex numbers consisting of all sequences whose differences are in the space lp has been studied by Basar, Altay [Ukrainian Math. J. 55(1)(2003), 136-147], where 1 ≤ p ≤ ∞. The main purpose of the present paper is to introduce the space bvp(F) of sequences of p-bounded variation of fuzzy numbers. Moreover, it is proved that the space bvp(F) includes the space lp(F) and also shown that the spaces bvp(F) and lp(F) axe isomorphic for 1 ≤ p ≤∞. Furthermore, some inclusion relations have been given. 相似文献
968.
Serre's nonnegativity conjecture for intersection multiplicities has recently been proven by O. Gabber. In this paper we investigate Serre's positivity conjecture using the methods which he developed. We show in particular that the positivity conjecture has implications for properties of symbolic powers of prime ideals in regular local rings. 相似文献
969.
The Poisson induction and coinduction procedures are used to construct Banach Lie–Poisson spaces as well as related systems of integrals in involution. This general method applied to the Banach Lie–Poisson space of trace class operators leads to infinite Hamiltonian systems of k-diagonal trace class operators which have infinitely many integrals. The bidiagonal case is investigated in detail. 相似文献
970.
O Introduction
We consider the orbital instability of standing waves for the Klein-Gordon-Zakharov system with different propagation speeds in three space dimensions 相似文献