全文获取类型
收费全文 | 76296篇 |
免费 | 5657篇 |
国内免费 | 7163篇 |
专业分类
化学 | 29220篇 |
晶体学 | 321篇 |
力学 | 6791篇 |
综合类 | 1354篇 |
数学 | 29493篇 |
物理学 | 21937篇 |
出版年
2023年 | 643篇 |
2022年 | 1142篇 |
2021年 | 1331篇 |
2020年 | 1504篇 |
2019年 | 1820篇 |
2018年 | 1500篇 |
2017年 | 1806篇 |
2016年 | 2028篇 |
2015年 | 1751篇 |
2014年 | 2610篇 |
2013年 | 5105篇 |
2012年 | 2960篇 |
2011年 | 3399篇 |
2010年 | 2942篇 |
2009年 | 4167篇 |
2008年 | 4615篇 |
2007年 | 4836篇 |
2006年 | 4509篇 |
2005年 | 3894篇 |
2004年 | 3570篇 |
2003年 | 3594篇 |
2002年 | 3300篇 |
2001年 | 2759篇 |
2000年 | 2691篇 |
1999年 | 2411篇 |
1998年 | 2259篇 |
1997年 | 1881篇 |
1996年 | 1642篇 |
1995年 | 1498篇 |
1994年 | 1370篇 |
1993年 | 1175篇 |
1992年 | 1120篇 |
1991年 | 860篇 |
1990年 | 723篇 |
1989年 | 616篇 |
1988年 | 563篇 |
1987年 | 447篇 |
1986年 | 381篇 |
1985年 | 459篇 |
1984年 | 443篇 |
1983年 | 220篇 |
1982年 | 362篇 |
1981年 | 423篇 |
1980年 | 324篇 |
1979年 | 310篇 |
1978年 | 240篇 |
1977年 | 220篇 |
1976年 | 171篇 |
1974年 | 113篇 |
1973年 | 111篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
991.
LuisaDiPiazza 《数学研究》1994,27(1):148-153
Some relationships between pointwise and weak convergence of a sequence of Henstock integrable functions are studied, In particular it is provided an example of a sequence of Henstock integrable functions whose pointwise limit is different from the weak one. By introducing an asymptotic version of the Henstock equiintegrability notion it is given a necessary and sufficient condition in order that a pointwisely convergent sequence of Henstock integrable functions is weakly convergent to its pointwise limit. 相似文献
992.
Luciano Galeone Roberto Garrappa 《Journal of Computational and Applied Mathematics》1997,80(2):377-195
We study convergence properties of time-point relaxation (TR) Runge-Kutta methods for linear systems of ordinary differential equations. TR methods are implemented by decoupling systems in Gauss-Jacobi, Gauss-Seidel and successive overrelaxation modes (continuous-time iterations) and then solving the resulting subsystems by means of continuous extensions of Runge-Kutta (CRK) methods (discretized iterations). By iterating to convergence, these methods tend to the same limit called diagonally split Runge-Kutta (DSRK) method. We prove that TR methods are equivalent to decouple in the same modes the linear algebraic system obtained by applying DSRK limit method. This issue allows us to study the convergence of TR methods by using standard principles of convergence of iterative methods for linear algebraic systems. For a particular problem regions of convergence are plotted. 相似文献
993.
994.
Complete Surjections and Complete Epimorphisms over Completely Distributive Lattices 总被引:1,自引:0,他引:1
Generators and lattice properties of the poset of complete homomorphisic images of a completely distributive lattice are exploited via the localic methods. Some intrinsic and extrinsic conditions about this poset to be a completely distributive lattice are given. It is shown that the category of completely distributive lattices is co-well-powered,and complete epimorphisms on completely distributive lattice are not necessary to be surjections. Finally, some conditions about complete epimorphisms to be surjections are given. 相似文献
995.
Bingzheng Li 《应用数学学报(英文版)》1997,13(2):209-220
We modify Szász-Durrmeyer operators by means of three-diagonal generalized matrix which overcomes a difficulty in extending a Berens-Lorentz result to the Szász-Durrmeyer operators for second order of smoothness. The direct and converse theorems for these operators inL
p
are also presented by Ditzian-Totik modulus of smoothness.This project is supported by Zhejiang Provincial Foundation of China. 相似文献
996.
997.
提出了一种用于修正光学神经网络硬件系统误差的虚拟神经网络模型,光学实验结果表明该网络能够有效地消除硬件系统误差对实验结果的影响。 相似文献
998.
ON THE COHOMOLOGY OF GENERALIZED RESTRICTED LIE ALGEBRAS 总被引:2,自引:0,他引:2
Shu Bin 《数学年刊B辑(英文版)》1998,19(4):421-432
0.IntroductionThispaperisaimedatdevelopingthecohomologytheoryofmodularLiealgebrasandthendeterminingthefirstcohomologygroupsofCartantypeLiealgebras.AsgeneralizationoftheconceptofrestrictedLiealgebras,ageneralizedrestrictedLiealgebra(GRLiealgebra)wasintroducedin[21],whichisassociatedwithabasisandamappingofthebasisintotheLiealgebrasatisfyingthegeneralized-restrictednessconditions.Generalizedrestrictedrepresentations(GRrepresentations)werethenintroduced,whichcanbereducedtotherepresentationsofa… 相似文献
999.
A q × n array with entries from 0, 1,…,q − 1 is said to form a difference matrix if the vector difference (modulo q) of each pair of columns consists of a permutation of [0, 1,… q − 1]; this definition is inverted from the more standard one to be found, e.g., in Colbourn and de Launey (1996). The following idea generalizes this notion: Given an appropriate δ (-[−1, 1]t, a λq × n array will be said to form a (t, q, λ, Δ) sign-balanced matrix if for each choice C1, C2,…, Ct of t columns and for each choice = (1,…,t) Δ of signs, the linear combination ∑j=1t jCj contains (mod q) each entry of [0, 1,…, q − 1] exactly λ times. We consider the following extremal problem in this paper: How large does the number k = k(n, t, q, λ, δ) of rows have to be so that for each choice of t columns and for each choice (1, …, t) of signs in δ, the linear combination ∑j=1t jCj contains each entry of [0, 1,…, q t- 1] at least λ times? We use probabilistic methods, in particular the Lovász local lemma and the Stein-Chen method of Poisson approximation to obtain general (logarithmic) upper bounds on the numbers k(n, t, q, λ, δ), and to provide Poisson approximations for the probability distribution of the number W of deficient sets of t columns, given a random array. It is proved, in addition, that arithmetic modulo q yields the smallest array - in a sense to be described. 相似文献
1000.
D—^3He聚变动力可行性研究 总被引:9,自引:3,他引:6
本文首先简要地讨论D-3He聚变的物理要求并与D-T聚变作相应的比较,然后运用目前的约束定律和第一稳定区β极限,对计划的近期ETR规模装置(如CIT,TIBER,FER,NET)进行D-3He得失相当和点火实验的可行性研究,并对高径比第二稳定区D-3He托卡马克堆进行参数学研究,最后指出潜在的缩短商用化进程可能性。 相似文献