全文获取类型
收费全文 | 22585篇 |
免费 | 2130篇 |
国内免费 | 1458篇 |
专业分类
化学 | 16188篇 |
晶体学 | 229篇 |
力学 | 1090篇 |
综合类 | 95篇 |
数学 | 2780篇 |
物理学 | 5791篇 |
出版年
2023年 | 240篇 |
2022年 | 388篇 |
2021年 | 427篇 |
2020年 | 600篇 |
2019年 | 514篇 |
2018年 | 446篇 |
2017年 | 413篇 |
2016年 | 725篇 |
2015年 | 686篇 |
2014年 | 856篇 |
2013年 | 1331篇 |
2012年 | 1651篇 |
2011年 | 1907篇 |
2010年 | 1090篇 |
2009年 | 999篇 |
2008年 | 1429篇 |
2007年 | 1468篇 |
2006年 | 1460篇 |
2005年 | 1388篇 |
2004年 | 1098篇 |
2003年 | 901篇 |
2002年 | 789篇 |
2001年 | 445篇 |
2000年 | 397篇 |
1999年 | 421篇 |
1998年 | 417篇 |
1997年 | 368篇 |
1996年 | 388篇 |
1995年 | 309篇 |
1994年 | 334篇 |
1993年 | 236篇 |
1992年 | 216篇 |
1991年 | 195篇 |
1990年 | 188篇 |
1989年 | 118篇 |
1988年 | 126篇 |
1987年 | 120篇 |
1986年 | 103篇 |
1985年 | 155篇 |
1984年 | 97篇 |
1983年 | 67篇 |
1982年 | 95篇 |
1981年 | 84篇 |
1980年 | 67篇 |
1979年 | 60篇 |
1978年 | 55篇 |
1977年 | 46篇 |
1976年 | 38篇 |
1975年 | 42篇 |
1973年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
111.
112.
Liang Ruixi Peng Jun Shen Jianhua 《Annals of Differential Equations》2006,22(4):502-510
The boundedness of the every solution and the asymptotic behavior of all solutions of the nonlinear neutral delay differential equation [x(t) - P(t)x(t - t)]' Q1 (t)f(x{t-σ1))-Q2(t)f(x(t -σ2))=0,t≥t0 are investigated, whereτ,σ1,σ2∈(0,∞), P∈C([t0,∞),R), and Q1,Q2∈C([t0,∞),R), f∈C(R,R). The sufficient conditions obtained improve the existing results in the literatures. 相似文献
113.
We give a small functorial algebraic model for the 2-stage Postnikov section of the K-theory spectrum of a Waldhausen category and use our presentation to describe the multiplicative structure with respect to biexact functors. 相似文献
114.
The authors introduce a new concept of measure-valued solution for the 3-D incompressible Euler equations in order to incorporate the complex phenomena present in limits of approximate solutions of these equations. One application of the concepts developed here is the following important result: a sequence of Leray-Hopf weak solutions of the Navier-Stokes equations converges in the high Reynolds number limit to a measure-valued solution of 3-D Euler defined for all positive times. The authors present several explicit examples of solution sequences for 3-D incompressible Euler with uniformly bounded local kinetic energy which exhibit complex phenomena involving both persistence of oscillations and development of concentrations. An extensions of the concept of Young measure is developed to incorporate these complex phenomena in the measure-valued solutions constructed here.Partially supported by N.S.F. GrantPartially supported by N.S.F. Grant 84-0223 and 86-11110 相似文献
115.
Summary There has been a rapid growth of interest in techniques for site-directed drug design, fuelled by the increasing availability of structural models of proteins of therapeutic importance, and by studies reported in the literature showing that potent chemical leads can be obtained by these techniques. Structure generation programs offer the prospect of discovering highly original lead structures from novel chemical families. Due to the fact that this technique is more-or-less still in its infancy, there are no case studies available that demonstrate the use of structure generation programs for site-directed drug design. Such programs were first proposed in 1986, and became commercially available in early 1992. They have shown their ability to reproduce, or suggest reasonable alternatives for, ligands in well-defined binding sites. This brief review will discuss the recent advances that have been made in the field of site-directed structure generation. 相似文献
116.
117.
In this paper the sufficient conditions for the existence of positive solutions of the neutral difference equations with positive and negative coefficients are established. The results improve some known conclusions in the literature 相似文献
118.
On free entropy dimension of finite von Neumann algebras 总被引:3,自引:0,他引:3
119.
Hui-Qing Lu Li-Ming Shen Guo-Hong Yang Y. Y. Lai K. S. Cheng 《International Journal of Theoretical Physics》2002,41(5):939-951
We apply the theory developed in quantum cosmology to a model of charged generalized Brans–Dicke gravity. This is a quantum model of gravitation interacting with a charged Brans–Dicke type scalar field which is considered in the Pauli frame. The Wheeler–DeWitt equation describing the evolution of the quantum Universe is solved in the semiclassical approximation by applying the WKB approximation. The wave function of the Universe is also obtained by applying both the Vilenkin-like and the Hartle–Hawking-like boundary conditions. We then make predictions from the wave functions and infer that the Vilenkin's boundary condition is more reasonable in the Brans–Dicke gravity models leading a large vacuum energy density at the beginning of the inflation. 相似文献
120.