全文获取类型
收费全文 | 160333篇 |
免费 | 24854篇 |
国内免费 | 17406篇 |
专业分类
化学 | 108811篇 |
晶体学 | 1705篇 |
力学 | 10049篇 |
综合类 | 1148篇 |
数学 | 20555篇 |
物理学 | 60325篇 |
出版年
2024年 | 501篇 |
2023年 | 2953篇 |
2022年 | 5238篇 |
2021年 | 5366篇 |
2020年 | 5950篇 |
2019年 | 5689篇 |
2018年 | 5342篇 |
2017年 | 4828篇 |
2016年 | 7247篇 |
2015年 | 7243篇 |
2014年 | 8880篇 |
2013年 | 11594篇 |
2012年 | 13870篇 |
2011年 | 14279篇 |
2010年 | 9926篇 |
2009年 | 9614篇 |
2008年 | 10166篇 |
2007年 | 9188篇 |
2006年 | 8594篇 |
2005年 | 7272篇 |
2004年 | 5800篇 |
2003年 | 4586篇 |
2002年 | 4165篇 |
2001年 | 3580篇 |
2000年 | 3235篇 |
1999年 | 3445篇 |
1998年 | 2910篇 |
1997年 | 2585篇 |
1996年 | 2649篇 |
1995年 | 2337篇 |
1994年 | 2146篇 |
1993年 | 1782篇 |
1992年 | 1597篇 |
1991年 | 1373篇 |
1990年 | 1148篇 |
1989年 | 948篇 |
1988年 | 710篇 |
1987年 | 666篇 |
1986年 | 607篇 |
1985年 | 545篇 |
1984年 | 379篇 |
1983年 | 321篇 |
1982年 | 259篇 |
1981年 | 187篇 |
1980年 | 137篇 |
1979年 | 71篇 |
1978年 | 78篇 |
1976年 | 71篇 |
1975年 | 79篇 |
1973年 | 74篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
971.
线性嵌套阵可以很好地在很宽的频率(N个倍频程,N=7)上实现恒定束宽。这种方法设计简单,又节省线阵阵元。本文给出了线性嵌套阵具体的数字化实现方法,解决了FIR滤波器设计,滤波器时间延迟等问题。由于数字化实现过程中使用了很多组FIR滤波器,计算量很大,文章采用了DSP信号处理板实现数字化算法,利用DSP处理板可以多任务同时处理优势,解决了计算量大的问题。经过实验验证,在DSP上实现的数字化的线性嵌套阵宽带恒定束宽方法满足了工程上实时处理的需要。 相似文献
972.
Li Likang 《数学年刊B辑(英文版)》1987,8(3):285-295
In this paper, the author solves the nonlinear Dirichlet problem with nonhomo- genous boundary condition by use of the isoparametric finite element method, and obtains the optimal error estimate. 相似文献
973.
974.
975.
The Randi? index R(G) of a (chemical) graph G is also called connectivity index. Hansen and Mélot [Variable neighborhood search for extremal graphs 6: analyzing bounds for the connectivity index, J. Chem. Inf. Comput. Sci. 43 (2003) 1-14] in their paper, characterized the chemical trees of given order and number of pendent vertices which have the minimum and maximum Randi? index, respectively. In this note, we point out the mistakes in the proofs of their results Theorems 8 and 10, while we still believe that the two theorems are true, and then we give their corrected proofs. 相似文献
976.
In this article,two uniqueness theorems of meromorphic mappings on moving targets with truncated multiplicities are proved. 相似文献
977.
Films of polytetrafluoroethylene (PTFE) were exposed to sodium naphthalenide (Na/naphtha) etchant so as to defluorinate the surface for obtaining hydroxyl functionality. Surface-initiators were immobilized on the PTFE films by esterification of 4,4′-azobis(4-cyanopentanoic acid) (ACP) and the hydroxyl groups covalently linked to the surface. Grafting of polymer brushes on the PTFE films was carried out by the surface-initiated free radical polymerization. Homopolymers brushes of methyl methacrylate (MMA) were prepared by free radical polymerization from the azo-functionalized PTFE surface. The chemical composition and topography of the graft-functionalized PTFE surfaces were characterized by X-ray photoelectron spectroscopy (XPS), attenuated total reflectance (ATR) FT-IR spectroscopy and atomic force microscopy (AFM). Water contact angles on PTFE films were reduced by surface grafting of MMA. 相似文献
978.
F.T. Yuan S.K. Chen W.M. Liao C.W. Hsu S.N. Hsiao W.C. Chang 《Journal of magnetism and magnetic materials》2006
The Au/FePt samples were prepared by depositing a gold cap layer at room temperature onto a fully ordered FePt layer, followed by an annealing at 800 °C for the purpose of interlayer diffusion. After the deposition of the gold layer and the high-temperature annealing, the gold atoms do not dissolve into the FePt Ll0 lattice. Compared with the continuous FePt film, the TEM photos of the bilayer Au(60 nm)/FePt(60 nm) show a granular structure with FePt particles embedded in Au matrix. The coercivity of Au(60 nm)/FePt(60 nm) sample is 23.5 kOe, which is 85% larger than that of the FePt film without Au top layer. The enhancement in coercivity can be attributed to the formation of isolated structure of FePt ordered phase. 相似文献
979.
Xia Chen 《Journal of Theoretical Probability》2006,19(3):721-739
We establish moderate and small deviations for the ranges of integer valued random walks. Our theorems apply to the limsup
and the liminf laws of the iterated logarithm.
We establish moderate and small deviations for the ranges of integer valued random walks. Our theorems apply to the limsup
and the liminf laws of the iterated logarithm. 相似文献
980.