全文获取类型
收费全文 | 25597篇 |
免费 | 4361篇 |
国内免费 | 4351篇 |
专业分类
化学 | 13921篇 |
晶体学 | 294篇 |
力学 | 1119篇 |
综合类 | 374篇 |
数学 | 2415篇 |
物理学 | 7169篇 |
无线电 | 9017篇 |
出版年
2024年 | 79篇 |
2023年 | 560篇 |
2022年 | 757篇 |
2021年 | 885篇 |
2020年 | 946篇 |
2019年 | 878篇 |
2018年 | 758篇 |
2017年 | 807篇 |
2016年 | 1018篇 |
2015年 | 1169篇 |
2014年 | 1420篇 |
2013年 | 1821篇 |
2012年 | 2023篇 |
2011年 | 2107篇 |
2010年 | 1699篇 |
2009年 | 1669篇 |
2008年 | 1836篇 |
2007年 | 1771篇 |
2006年 | 1666篇 |
2005年 | 1442篇 |
2004年 | 1113篇 |
2003年 | 987篇 |
2002年 | 1064篇 |
2001年 | 923篇 |
2000年 | 836篇 |
1999年 | 640篇 |
1998年 | 449篇 |
1997年 | 378篇 |
1996年 | 399篇 |
1995年 | 329篇 |
1994年 | 315篇 |
1993年 | 279篇 |
1992年 | 236篇 |
1991年 | 195篇 |
1990年 | 149篇 |
1989年 | 144篇 |
1988年 | 106篇 |
1987年 | 100篇 |
1986年 | 67篇 |
1985年 | 71篇 |
1984年 | 65篇 |
1983年 | 36篇 |
1982年 | 36篇 |
1981年 | 19篇 |
1980年 | 25篇 |
1979年 | 10篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1957年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
121.
高阶线性微分方程的解及其解的导数的不动点 总被引:2,自引:0,他引:2
研究了复域齐次和非齐次线性微分方程的解及其解的导数的不动点与超级问题,得到了整函数系数的齐次和非齐次线性微分方程的解及其解的导数的不动点的两个结果,所得结果推广了一些相关结果. 相似文献
122.
123.
JIN Lu 《数学年刊B辑(英文版)》2004,25(4):483-492
A unicity theorem concerning the total derivative for entire functions of several complex variables is proved. 相似文献
124.
Qing Shi Dong Yang Yanlei Su Jian Li Zhongyi Jiang Yanjun Jiang Weikang Yuan 《Journal of nanoparticle research》2007,9(6):1205-1210
Lipase from Candida rugosa was covalently anchored onto acid-treated multi-walled carbon nanotubes (MWNTs) through a self-catalytic mechanism. A variety
of characterization techniques including FTIR, Raman spectroscopy, and XPS were employed to demonstrate the formation of the
ester linkage between lipase and MWNTs. The MWNTs-lipase biocomposites showed significantly increased solubility in some common-used
organic solvents, such as THF, DMF and chloroform. This study may offer a novel and facile route for covalent modification
of carbon nanotubes, and expand the potential utilization of both lipases and MWNTs in the fields of biocatalyst and biosensor. 相似文献
125.
The main aim of this paper is to provide convergence analysis of Quasi-Wilson nonconforming finite element to Maxwell's equations under arbitrary quadrilateral meshes.The error estimates are derived,which are the same as those for conforming elements under conventional regular meshes. 相似文献
126.
A wireless LAN service integration architecture based on current wireless LAN hot spots is proposed so that migration to a new service becomes easier and cost effective. The proposed architecture offers wireless LAN seamless roaming in wireless LAN/cellular mobile networks. In addition, a link-layer-assisted mobile IP handoff mechanism is introduced to improve the network/domain switching quality in terms of handoff delay and packet loss. An application layer end-to-end authentication and key negotiation scheme is proposed to overcome the open-air connection problem existing in wireless LAN deployment. The scheme provides a general solution for Internet applications running on a mobile station under various authentication scenarios and keeps the communications private to other wireless LAN users and foreign network. A functional demonstration of the scheme is given. The research results can contribute to rapid deployment of wireless LANs. 相似文献
127.
128.
Hua Jin Zhuangqi Hu Qingmin Liu Yunlong Ge Changxu Shi 《Applied Physics A: Materials Science & Processing》1992,54(5):399-403
A crystallization study has been carried out for rapidly solidified Bi2Pb0.5Sr2Ca4Cu5Ox glass. Glass transition temperature T
g, crystallized superconducting phases and microstructural changes were measured and analysed by differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The crystallization mechanism of the three superconducting phases — (2201) 20 K phase, (2212) 80 K phase, and (2223) 110 K phase — has been discussed, and a time-temperature-transformation diagram for the glass has been constructed. 相似文献
129.
The cross-spectral estimation methods are efficient in estimating the parameters of sinusoidal signals embedded in colored noise. But up to now, only FPT and cross-periodogram methods are used in this field, the modern auto-spectral estimation method is introduced into cross-spectral estimation in this paper, meanwhile the cross-correlation based Yule-Walker equation is proposed theoretically and the moment and singular-value decomposition (SVD)) algorithms for cross-spectral estimation have been developed. Finally, a numerical example is given for comparing the presented methods with the well-known Cadzow's SVD method. 相似文献
130.
近几年来,由于超辐射发光二极管在光纤陀螺和光时域反射仪等方面的重要应用,已引起了人们的极大关注,许多国家都在竞相研制和开发.本文综述了目前超辐射发光二极管的主要结构和特性及其应用前景. 相似文献