全文获取类型
收费全文 | 17341篇 |
免费 | 1297篇 |
国内免费 | 858篇 |
专业分类
化学 | 753篇 |
晶体学 | 10篇 |
力学 | 2008篇 |
综合类 | 307篇 |
数学 | 14160篇 |
物理学 | 2258篇 |
出版年
2023年 | 115篇 |
2022年 | 195篇 |
2021年 | 223篇 |
2020年 | 318篇 |
2019年 | 305篇 |
2018年 | 336篇 |
2017年 | 428篇 |
2016年 | 420篇 |
2015年 | 330篇 |
2014年 | 786篇 |
2013年 | 1087篇 |
2012年 | 823篇 |
2011年 | 951篇 |
2010年 | 803篇 |
2009年 | 1007篇 |
2008年 | 1089篇 |
2007年 | 1115篇 |
2006年 | 917篇 |
2005年 | 874篇 |
2004年 | 703篇 |
2003年 | 698篇 |
2002年 | 664篇 |
2001年 | 516篇 |
2000年 | 533篇 |
1999年 | 480篇 |
1998年 | 447篇 |
1997年 | 406篇 |
1996年 | 370篇 |
1995年 | 332篇 |
1994年 | 268篇 |
1993年 | 218篇 |
1992年 | 207篇 |
1991年 | 180篇 |
1990年 | 153篇 |
1989年 | 99篇 |
1988年 | 129篇 |
1987年 | 92篇 |
1986年 | 116篇 |
1985年 | 138篇 |
1984年 | 113篇 |
1983年 | 34篇 |
1982年 | 84篇 |
1981年 | 62篇 |
1980年 | 51篇 |
1979年 | 42篇 |
1978年 | 68篇 |
1977年 | 53篇 |
1976年 | 36篇 |
1975年 | 15篇 |
1974年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
In this paper, the deformation of the Heisenberg algebra, consistent with both the generalized uncertainty principle and doubly special relativity, has been analyzed. It has been observed that, though this algebra can give rise to fractional derivative terms in the corresponding quantum mechanical Hamiltonian, a formal meaning can be given to them by using the theory of harmonic extensions of function. Depending on this argument, the expression of the propagator of the path integral corresponding to the deformed Heisenberg algebra, has been obtained. In particular, the consistent expression of the one dimensional free particle propagator has been evaluated explicitly. With this propagator in hand, it has been shown that, even in free particle case, normal generalized uncertainty principle and doubly special relativity show very much different result. 相似文献
4.
In this paper, we consider a viscoelastic wave equation of variable coefficients in the presence of past history with nonlinear damping and delay in the internal feedback and dynamic boundary conditions. Under suitable assumptions, we establish an explicit and general decay rate result without imposing restrictive assumption on the behavior of the relaxation function at infinity by Riemannian geometry method and Lyapunov functional method. 相似文献
5.
Boundedness of commutators on homogeneous Herz spaces 总被引:9,自引:0,他引:9
The boundedness on homogeneous Herz spaces is established for a large class of linear commutators generated by BMO(R
n
) functions and linear operators of rough kernels which include the Calderón-Zygmund operators and the Ricci-Stein oRfiUatory
singular integrals with rough kernels.
Project supponed in pan by the National h’atural Science Foundation of China (Grant No. 19131080) and the NEDF of China. 相似文献
6.
Nobuaki Obata 《Acta Appl Math》1997,47(1):49-77
A general theory of operators on Boson Fock space is discussed in terms of the white noise distribution theory on Gaussian space (white noise calculus). An integral kernel operator is generalized from two aspects: (i) The use of an operator-valued distribution as an integral kernel leads us to the Fubini type theorem which allows an iterated integration in an integral kernel operator. As an application a white noise approach to quantum stochastic integrals is discussed and a quantum Hitsuda–Skorokhod integral is introduced. (ii) The use of pointwise derivatives of annihilation and creation operators assures the partial integration in an integral kernel operator. In particular, the particle flux density becomes a distribution with values in continuous operators on white noise functions and yields a representation of a Lie algebra of vector fields by means of such operators. 相似文献
7.
In this paper we consider a wavelet algorithm for the piecewise constant collocation method applied to the boundary element solution of a first kind integral equation arising in acoustic scattering. The conventional stiffness matrix is transformed into the corresponding matrix with respect to wavelet bases, and it is approximated by a compressed matrix. Finally, the stiffness matrix is multiplied by diagonal preconditioners such that the resulting matrix of the system of linear equations is well conditioned and sparse. Using this matrix, the boundary integral equation can be solved effectively. 相似文献
8.
本文是文[1-7]的继续,研究变权综合问题,从确定变权的经验公式入手引出了变权原理,给出了变权的公理化定义,讨论了与之有关的均衡函数及其梯度向量。 相似文献
9.
四气门发动机可变涡流稀薄燃烧特性研究 总被引:1,自引:0,他引:1
本文研究了可变涡流对四气门发动机稀薄燃烧特性的影响情况。在稀薄燃烧情况下,发动机负荷大小对CO和HC排放的影响不大,对NOx排放的影响主要表现在对13~17空燃比范围内NOx排放的影响,负荷越大,NOx排放越大;对空燃比小于13或大于17以后的NOx排放影响较小。阀片位置对发动机排放特性的影响较小,对发动机的燃油经济性存在一定影响,这是因为不同阀片位置的进气涡流比不同所致,同时也表明较强的涡流运动对燃油经济性更有利。涡流运动在不同转速条件下对发动机燃油经济性的影响情况不同,它更有利于改善低速条件下的燃油经济性。 相似文献
10.
M. M. Kostreva 《Journal of Optimization Theory and Applications》1989,62(1):63-76
Murty's algorithm for the linear complementarity problem is generalized to solve the optimality conditions for linear and convex quadratic programming problems with both equality and inequality constraints. An implementation is suggested which provides both efficiency and tight error control. Numerical experiments as well as field tests in various applications show favorable results.The author thanks K. G. Murty for his encouragement and helpful comments. 相似文献