全文获取类型
收费全文 | 10135篇 |
免费 | 1816篇 |
国内免费 | 1563篇 |
专业分类
化学 | 5974篇 |
晶体学 | 80篇 |
力学 | 359篇 |
综合类 | 138篇 |
数学 | 937篇 |
物理学 | 2542篇 |
无线电 | 3484篇 |
出版年
2024年 | 37篇 |
2023年 | 179篇 |
2022年 | 221篇 |
2021年 | 295篇 |
2020年 | 329篇 |
2019年 | 392篇 |
2018年 | 322篇 |
2017年 | 305篇 |
2016年 | 420篇 |
2015年 | 476篇 |
2014年 | 566篇 |
2013年 | 743篇 |
2012年 | 801篇 |
2011年 | 828篇 |
2010年 | 671篇 |
2009年 | 708篇 |
2008年 | 731篇 |
2007年 | 654篇 |
2006年 | 641篇 |
2005年 | 549篇 |
2004年 | 527篇 |
2003年 | 488篇 |
2002年 | 581篇 |
2001年 | 414篇 |
2000年 | 318篇 |
1999年 | 286篇 |
1998年 | 181篇 |
1997年 | 133篇 |
1996年 | 91篇 |
1995年 | 90篇 |
1994年 | 82篇 |
1993年 | 53篇 |
1992年 | 62篇 |
1991年 | 68篇 |
1990年 | 51篇 |
1989年 | 37篇 |
1988年 | 31篇 |
1987年 | 25篇 |
1986年 | 30篇 |
1985年 | 25篇 |
1984年 | 14篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1974年 | 3篇 |
1968年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
972.
973.
974.
LI ZhiHong LI ErTao SU Jun LI YunJu BAI XiXiang GUO Bing WANG YouBao CHEN YongShou HOU SuQing ZENG Sheng LIAN Gang SHI JianRong & LIU WeiPing China Institute of Atomic Energy Beijing China National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国科学:物理学 力学 天文学(英文版)》2011,(Z1)
Lithium isotopes have attracted an intense interest because the abundance of both 6Li and 6Li from big bang nucleosynthesis (BBN) is one of the puzzles in nuclear astrophysics. Many investigations of both astrophysical observation and nucleosynthesis calculation have been carried out to solve the puzzle, but it is not solved yet. Several nuclear reactions involving lithium have been indirectly measured at China Institute of Atomic Energy, Beijing. The Standard BBN (SBBN) network calculations are then perfo... 相似文献
975.
H. Sheng H.G. Sun C. Coopmans Y.Q. Chen G.W. Bohannan 《The European physical journal. Special topics》2011,193(1):93-104
Recent research results have shown that many complex physical phenomena can be better described using variable-order fractional
differential equations. To understand the physical meaning of variable-order fractional calculus, and better know the application
potentials of variable-order fractional operators in physical processes, an experimental study of temperature-dependent variable-order
fractional integrator and differentiator is presented in this paper. The detailed introduction of analogue realization of
variable-order fractional operator, and the influence of temperature to the order of fractional operator are presented in
particular. Furthermore, the potential applications of variable-order fractional operators in PI
λ(t)
D
μ(t) controller and dynamic-order fractional systems are suggested. 相似文献
976.
A survey on the mechanisms of powerful terahertz (THz) radiation from laser plasmas is presented.Firstly,an analytical model is described,showing that a transverse net current formed in a plasma can be converted into THz radiations at the plasma oscillation frequency.This theory is applied to explain THz generation in a gas driven by two-color laser pulses.It is also applied to THz generation in a tenuous plasma driven by a chirped laser pulse,a few-cycle laser pulse,a DC/AC bias electric field.These are well verified by particle-in-cell simulations,demonstrating that THz radiations produced in these approaches are nearly single-cycles and linear polarized.In the chirped laser scheme and the few-cycle laser scheme,THz radiations with the peak field strength of tens of MV/cm and the peak power of gigawatt can be achieved with the incident laser intensity less than 10 17 W/cm 2. 相似文献
977.
Composite fibrous membranes based on poly(acrylonitrile)(PAN)-poly(vinyl chloride)(PVC) have been prepared by electrospinning. The fibrous membranes are made up of fibers of 850- to 1,300-nm diameters. These fibers are stacked in layers to produce a fully interconnected pore structure. Polymer electrolytes were prepared by immersing the fibrous membranes in 1 M LiClO4-PC solution for 60 min. The condition of pure PAN polymer electrolytes is jelly, which has poor mechanical performance and cannot be used. But when PVC with a good mechanical stiffener was added to PAN, the condition of composite PAN?CPVC polymer electrolytes becomes free-standing. In addition, the optimum electrochemical properties have been observed for the polymer electrolyte based on PAN?CPVC (8:2, w/w) to show ionic conductivity of 1.05?×?10?3 S cm?1 at 25 °C, anodic stability up to 4.9 V versus Li/Li+, and a good compatibility with lithium metal resulting in low interfacial resistance. The promising results showed that fibrous PEs based on PAN?CPVC (8:2, w/w) have good mechanical stability and electrochemical properties. This shows a great potential application in polymer lithium-ion batteries. 相似文献
978.
979.
基于正交投影散度的高光谱遥感波段选择算法 总被引:2,自引:0,他引:2
由于高光谱数据的海量高维特征,对其进行降维处理成为高光谱遥感研究的一个重要问题.波段选择算法由于能够有效地保留原始数据的信息,在高光谱数据降维及后续的遥感识别与分类等方面具有明显的优越性.文章提出了一种基于正交投影散度(OPD)的波段选择方法,该方法继承了正交子空间投影(OSP)算法的特点,通过把原始数据投影到特征空间... 相似文献
980.