全文获取类型
收费全文 | 7278篇 |
免费 | 518篇 |
国内免费 | 732篇 |
专业分类
化学 | 488篇 |
晶体学 | 8篇 |
力学 | 734篇 |
综合类 | 175篇 |
数学 | 6438篇 |
物理学 | 685篇 |
出版年
2024年 | 9篇 |
2023年 | 91篇 |
2022年 | 116篇 |
2021年 | 141篇 |
2020年 | 172篇 |
2019年 | 166篇 |
2018年 | 221篇 |
2017年 | 204篇 |
2016年 | 199篇 |
2015年 | 160篇 |
2014年 | 304篇 |
2013年 | 777篇 |
2012年 | 306篇 |
2011年 | 399篇 |
2010年 | 324篇 |
2009年 | 461篇 |
2008年 | 471篇 |
2007年 | 434篇 |
2006年 | 459篇 |
2005年 | 359篇 |
2004年 | 309篇 |
2003年 | 353篇 |
2002年 | 317篇 |
2001年 | 255篇 |
2000年 | 241篇 |
1999年 | 229篇 |
1998年 | 224篇 |
1997年 | 202篇 |
1996年 | 119篇 |
1995年 | 89篇 |
1994年 | 71篇 |
1993年 | 61篇 |
1992年 | 36篇 |
1991年 | 30篇 |
1990年 | 20篇 |
1989年 | 17篇 |
1988年 | 14篇 |
1987年 | 13篇 |
1986年 | 12篇 |
1985年 | 26篇 |
1984年 | 22篇 |
1983年 | 12篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1980年 | 19篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1974年 | 3篇 |
排序方式: 共有8528条查询结果,搜索用时 62 毫秒
991.
E. Serrano C. Piñ eiro J. M. Delgado 《Proceedings of the American Mathematical Society》2006,134(3):689-695
Let and be Banach spaces. We say that a set denotes the space of all compact operators from into ) is equicompact if there exists a null sequence in such that for all and all . It is easy to show that collectively compactness and equicompactness are dual concepts in the following sense: is equicompact iff is collectively compact. We study some properties of equicompact sets and, among other results, we prove: 1) a set is equicompact iff each bounded sequence in has a subsequence such that is a converging sequence uniformly for ; 2) if does not have finite cotype and is a maximal equicompact set, then, given and a finite set in , there is an operator such that for and all .
992.
Martin Kummer 《Transactions of the American Mathematical Society》2006,358(1):59-86
We show that some natural games introduced by Lachlan in 1970 as a model of recursion theoretic constructions are undecidable, contrary to what was previously conjectured. Several consequences are pointed out; for instance, the set of all -sentences that are uniformly valid in the lattice of recursively enumerable sets is undecidable. Furthermore we show that these games are equivalent to natural subclasses of effectively presented Borel games.
993.
We classify the indecomposable pure injective modules over a wide class of -domestic string algebras and calculate the Krull–Gabriel dimension of these algebras.This paper was written during the visit of the second author to the University of Manchester supported by EPSRC grant GR/R44942/01. 相似文献
994.
Leonid G. Fel 《Functional Analysis and Other Mathematics》2006,1(2):119-157
We find the matrix representation of the set Δ(d
3), where d
3=(d
1,d
2,d
3), of integers that are unrepresentable by d
1,d
2,d
3 and develop a diagrammatic procedure for calculating the generating function Φ(d
3;z) for the set Δ(d
3). We find the Frobenius number F(d
3), the genus G(d
3), and the Hilbert series H(d
3;z) of a graded subring for nonsymmetric and symmetric semigroups
and enhance the lower bounds of F(d
3) for symmetric and nonsymmetric semigroups.
相似文献
995.
Exponential Attractor for a Nonlinear Boussinesq Equation 总被引:1,自引:0,他引:1
Ahmed Y. Abdallah 《应用数学学报(英文版)》2006,22(3):443-450
This paper is devoted to prove the existence of an exponential attractor for the semiflow generated by a nonlinear Boussinesq equation. We formulate the Boussinesq equation as an abstract equation in the Hilbert space H0^2(0, 1) × L^2(0, 1). The main step in this research is to show that there exists an absorbing set for the solution semiflow in the Hilbert space H0^3(0, 1) × H0^1(0, 1). 相似文献
996.
Xiong Shuangping 《数学物理学报(B辑英文版)》1999,19(2):226-233
1IntroductionSelf-similarMarkoyprocesseson(0,co)wereintroducedbyLamperti[ZI.AnormalMarkovprocessX=(fi,F,R,Xt,ot,p")withstatespace(0,co)iscalledself-similarMarkovprocessoforderorjor>0,ifitstransitionfunctionPt(x,A)satisfiesPt(x,A)=Pa,(a"x,a"A)Vt>9,a>0,x>0,AEB(0,co).Itwasshownin[2]and[11]thateveryself-similarMarkovprocesson(0,co)automaticllyisstronglyMarkovianandhasanicepath",soitisaHuntprocessinthesenseof[1].Thefractalpropertiesoftheprocesseswerestudiedin[6]and[8].TheitoExcursiontheor… 相似文献
997.
This Letter presents a new technique for measuring the variation of the material properties along the thickness in a freestanding inhomogeneous thin film. The analytical results reveal a simple relation between the material properties and the set of cut-off frequencies of Lamb waves. The influence of the graded properties on the variation of cut-off frequencies in three different kinds of models, including artificial FGM model, sub-surface damage model, and nano-porous thin film model, is discussed. These results provide theoretical guidance for characterizing the material property variations of MEMS/NEMS. 相似文献
998.
F. Paravento 《Journal of computational physics》2010,229(12):4613-4647
In this study we present a model for the interaction of premixed flames with obstacles in a channel flow. Although the flow equations are solved with Direct Numerical Simulation using a low Mach number approximation, the resolution used in the computation is limited (∼1 mm) hence the inner structure of the flame and the chemical scales are not solved. The species equations are substituted with a source term in the energy equation that simulates a one-step global reaction. A level set method is applied to track the position of the flame and its zero level is used to activate the source term in the energy equation only at the flame front. An immersed boundary method reproduces the geometry of the obstacles. The main contribution of the paper is represented by the proposed numerical approach: an IMEX (implicit–explicit) Runge–Kutta scheme is used for the time integration of the energy equation and a new pressure correction algorithm is introduced for the time integration of the momentum equations. The approach presented here allows to calculate flames which produce high density ratios between burnt and unburnt regions. The model is verified by simulating first simple solutions for one- and two-dimensional flames. At last, the experiments performed by Masri and Ibrahim with square and rectangular bodies are calculated. 相似文献
999.
An inverse problem of inhomogeneity identification inside a nonlinear magnetic material from the local measurements of the magnetic induction is investigated. The representation of the shape of the inhomogeneity and its evolution during an iterative reconstruction process is achieved by the level set method. The reconstruction is realized by the minimization of a cost function using the steepest descent method. The gradient directions are evaluated using the sensitivity equation and the adjoint variable method. Simulations has been performed showing the robustness of the algorithm and its ability to reconstruct single inhomogeneities, convex and non-convex, as well as multiple inhomogeneities. 相似文献
1000.
Two linear orderings of a same set are perpendicular if the only self-mappings of this set that preserve them both are the identity and the constant mappings. Two linear orderings are orthogonal if they are isomorphic to two perpendicular linear orderings. We show that two countable linear orderings are orthogonal as soon as each one has two disjoint infinite intervals. From this and previously known results it follows in particular that each countably infinite linear ordering is orthogonal to itself. 相似文献