全文获取类型
收费全文 | 39388篇 |
免费 | 3681篇 |
国内免费 | 4236篇 |
专业分类
化学 | 10057篇 |
晶体学 | 128篇 |
力学 | 2515篇 |
综合类 | 234篇 |
数学 | 8155篇 |
物理学 | 11561篇 |
综合类 | 14655篇 |
出版年
2024年 | 119篇 |
2023年 | 354篇 |
2022年 | 655篇 |
2021年 | 788篇 |
2020年 | 959篇 |
2019年 | 883篇 |
2018年 | 894篇 |
2017年 | 1059篇 |
2016年 | 1216篇 |
2015年 | 1217篇 |
2014年 | 1904篇 |
2013年 | 2589篇 |
2012年 | 2129篇 |
2011年 | 2546篇 |
2010年 | 1958篇 |
2009年 | 2397篇 |
2008年 | 2480篇 |
2007年 | 2788篇 |
2006年 | 2431篇 |
2005年 | 2088篇 |
2004年 | 1769篇 |
2003年 | 1694篇 |
2002年 | 1542篇 |
2001年 | 1276篇 |
2000年 | 1231篇 |
1999年 | 989篇 |
1998年 | 934篇 |
1997年 | 767篇 |
1996年 | 640篇 |
1995年 | 551篇 |
1994年 | 466篇 |
1993年 | 466篇 |
1992年 | 438篇 |
1991年 | 354篇 |
1990年 | 384篇 |
1989年 | 353篇 |
1988年 | 300篇 |
1987年 | 260篇 |
1986年 | 187篇 |
1985年 | 154篇 |
1984年 | 152篇 |
1983年 | 80篇 |
1982年 | 117篇 |
1981年 | 108篇 |
1980年 | 95篇 |
1979年 | 98篇 |
1978年 | 78篇 |
1977年 | 76篇 |
1976年 | 70篇 |
1973年 | 61篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
133.
Magnetic properties of Co chain-coated carbon nanotube (CNT) were investigated using a first-principles calculation. Binding energy between Co chain and CNT increased with the coverage ratio, and the adsorption of Co chains on CNT enhanced the conductance channel. Total magnetic moment of Co chains coated on CNT increased with the coverage ratio, while the magnetic moment per Co atom decreased due to spin flip of majority spin states in Co atoms. Spin polarization at the Fermi level of the Co chains was calculated to converge to that of bulk fcc Co. 相似文献
134.
WU Ke ZHAO Weizhong & GUO Hanying Department of Mathematics Capital Normal University Beijing China Institute of Theoretical Physics Chinese Academy of Sciences Beijing China 《中国科学A辑(英文版)》2006,(11)
In a way similar to the continuous case formally, we define in different but equivalent manners the difference discrete connection and curvature on discrete vector bundle over the regular lattice as base space. We deal with the difference operators as the discrete counterparts of the derivatives based upon the differential calculus on the lattice. One of the definitions can be extended to the case over the random lattice. We also discuss the relation between our approach and the lattice gauge theory and apply to the discrete integrable systems. 相似文献
135.
Chen Hao 《中国科学A辑(英文版)》2006,49(5):715-720
In this paper, for the the primes p such that 3 is a divisor of p − 1, we prove a result which reduces the computation of the linear complexity of a sequence over GF(p
m) (any positive integer m) with the period 3n (n and p
m − 1 are coprime) to the computation of the linear complexities of three sequences with the period n. Combined with some known algorithms such as generalized Games-Chan algorithm, Berlekamp-Massey algorithm and Xiao-Wei-Lam-Imamura
algorithm, we can determine the linear complexity of any sequence over GF(p
m) with the period 3n (n and p
m
− 1 are coprime) more efficiently. 相似文献
136.
技术创新具有独特的结构和内含。而职业技校要培养有创新意识的技术工人和技术员,就必须使学生既要掌握理论知识,又要学得生产技能。只有两者有机结合,才能为技术创新打好基础。 相似文献
137.
The plastic deformation field near the horizontal surface of a half space of perfectly plastic material associated with an indenting rotating rigid tooth is studied using slip line theory. The tooth is one of many on a roll surface and indents first into the half-space material and then rotates about the roll center. A slip line field is proposed for the deforming plastic region and a solution scheme is outlined. The emphasis is on determining the shape of the deforming region, especially that of the free surface. The study has a potential application in roughness transfer in metal forming processing. 相似文献
138.
考虑Duffing方程x+g(x,t)=h(t),在g(x,t)满足简单的凸凹性条件。以及g'(x,t)跨越第一共振点时,本文指出,当强迫振动项h(t)充分小时,所讨论的Duffing方程的2π周期解恰有三个. 相似文献
139.
The phase boundary theory and the contact rule of phase regions are compared, and some weaknesses of the latter are manifested.
The comparison between the Gupta’s method and the boundary theory method for constructing multicomponent isobaric sections
is also presented. 相似文献
140.
Tony Donnelly 《Applied Surface Science》2006,252(13):4445-4448
Ultra-thin (0.5-5 nm) films of Ag have been prepared by pulsed laser deposition in vacuum using a 26 ns KrF excimer laser at 1 J cm−2. The deposition was controlled using a Langmuir ion probe and a quartz crystal thickness monitor. Transmission electron microscopy showed that the films are not continuous, but are structured on nanometer size scales. Optical absorption spectra showed the expected surface plasmon resonance feature, which shifted to longer wavelength and increased in strength as the equivalent film thickness was increased. It is shown that Maxwell Garnett effective medium theory can be used to calculate the main features of optical absorption spectra. 相似文献