全文获取类型
收费全文 | 69607篇 |
免费 | 12160篇 |
国内免费 | 11816篇 |
专业分类
化学 | 49410篇 |
晶体学 | 1336篇 |
力学 | 4399篇 |
综合类 | 1183篇 |
数学 | 8587篇 |
物理学 | 28668篇 |
出版年
2024年 | 233篇 |
2023年 | 1295篇 |
2022年 | 2672篇 |
2021年 | 2713篇 |
2020年 | 2844篇 |
2019年 | 2684篇 |
2018年 | 2345篇 |
2017年 | 2644篇 |
2016年 | 3192篇 |
2015年 | 3419篇 |
2014年 | 4094篇 |
2013年 | 5230篇 |
2012年 | 6085篇 |
2011年 | 6164篇 |
2010年 | 4742篇 |
2009年 | 4541篇 |
2008年 | 5027篇 |
2007年 | 4429篇 |
2006年 | 4186篇 |
2005年 | 3629篇 |
2004年 | 2762篇 |
2003年 | 2120篇 |
2002年 | 2005篇 |
2001年 | 1834篇 |
2000年 | 1711篇 |
1999年 | 1539篇 |
1998年 | 1140篇 |
1997年 | 1022篇 |
1996年 | 1030篇 |
1995年 | 904篇 |
1994年 | 801篇 |
1993年 | 681篇 |
1992年 | 618篇 |
1991年 | 511篇 |
1990年 | 462篇 |
1989年 | 349篇 |
1988年 | 287篇 |
1987年 | 292篇 |
1986年 | 242篇 |
1985年 | 204篇 |
1984年 | 165篇 |
1983年 | 161篇 |
1982年 | 108篇 |
1981年 | 86篇 |
1980年 | 61篇 |
1979年 | 53篇 |
1978年 | 25篇 |
1977年 | 28篇 |
1976年 | 24篇 |
1975年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
102.
103.
以噻吩为单体,在等离子体环境中聚合成致密的有机膜。利用Rutherford背散射(RB2S)和质子弹性反冲(ERD)、傅里叶红外谱(FTIR)测定了膜的成分和结构;从近红外-可见-紫外光的反射和透射谱,运用传递矩阵方法研究了膜的光学性质;此外,还探讨了24keV的I+离子束的注入对等离子体噻吩聚合膜的掺杂效应。结果表明,注入层内电荷载流子的输运机理可用Mott的可变自由程跳跃(VRH)理论给以解释。
关键词: 相似文献
104.
In theory, both polarity and steric hindrance are basic factors which affect molecular interactions. To investigate the optical properties and steric structures of chiral compounds having different chiral moieties which affect the wavelength of light reflection in liquid crystal (LC) cells, a series of novel chiral compounds and azobenzene derivatives were synthesized. The liquid crystalline phases of the compounds were identified using small angle X-ray diffraction, differential scanning calorimetry and polarizing optical microscopy. Cholesteric LC cells with various synthesized chiral dopants which selectively reflect visible light were first prepared, the photochemical switching behaviour of colours was then investigated, with special reference to the change in transmittance in cholesteric LC cells containing an azobenzene derivative as a photoisomerizable guest molecule. Reversible isomerization of azobenzene molecules occurred in the cholesteric systems, resulting in a depression of TChI and a shift of the selectively reflected wavelength. We discuss the photochemically driven change in the helical pitch of the cholesteric LCs with respect to structural effects involving the chiral moieties. Molecular interactions caused by the added dopants, reliability and stability of the photoisomerization, and UV irradiation effects on the cholesteric LC cells were also investigated. A real image was recorded through a mask on a cholesteric LC cell fabricated in this investigation. 相似文献
105.
Chii-Wann Lin Kuo-Ping Chen Ming-Chii Su Chih-Kung Lee Chih-Chung Yang 《Optical and Quantum Electronics》2005,37(13-15):1423-1437
We have reported a novel design of surface plasmon resonance (SPR) device, which uses alternating dielectric layers to enhance the SPR signal quality and modulate its resonant position. Admittance loci method of thin film design has been used in the design of such a device. The use of biomolecular thin film, such as DNAs or Porteins, in this design can result in resonant condition of wavelength changes as well. Bio-plasmonics is proposed for the research and development of novel devices, which use biomolecules as a part of the plasmon oscillation system to actively interact with nano/micro structure. 相似文献
106.
等腰三角形Mindlin板的自由振动分析 总被引:2,自引:0,他引:2
提出了一种新方法来对基于 Mindlin剪切变形理论的等腰三角形板进行自由振动分析 .此方法采用了一种新的基函数并利用 pb-2 Rayleigh-Ritz边界函数得到了一种新型的 Ritz方法 .这种方法的有效性通过收敛性和对比性分析得到了证实 .数值结果表明此方法相当精确有效 . 相似文献
107.
Yang Zuosheng 《国际流体数值方法杂志》2005,47(12):1423-1430
A complete boundary integral formulation for compressible Navier–Stokes equations with time discretization by operator splitting is developed using the fundamental solutions of the Helmholtz operator equation with different order. The numerical results for wall pressure and wall skin friction of two‐dimensional compressible laminar viscous flow around airfoils are in good agreement with field numerical methods. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
108.
关于多线性振荡奇异积分在加权Hardy-型空间上的一致估计 总被引:1,自引:0,他引:1
本文对一类具有光滑位相函数的多线性振荡奇异积分算子建立了一致的加权(H^1(R^n),L^1(R^n))估计及一致的加权(HKp(R^n),Kp(R^n)估计。 相似文献
109.
110.
Effects of Substrate Temperature on Helium Content and Microstructure of Nanocrystalline Titanium Films 下载免费PDF全文
Helium-charged nanocrystalline titanium films have been deposited by HeAr magnetron co-sputtering. The effects of substrate temperature on the helium content and microstructure of the nanocrystalline titanium films have been studied. The results indicate that helium atoms with a high concentration are evenly incorporated in the deposited titanium films. When the substrate temperature increases from 60℃ to 350℃ while the other deposition'parameters are fixed, the helium content decreases gradually from 38.6 at.% to 9.2at.%, which proves that nanocrystalline Ti films have a great helium storage capacity. The 20 angle of the Bragg peak of (002) crystal planes of the He-charged Ti film shifts to a lower angle and that of (100) crystal plane is unchanged as compared with that of the pure Ti film, which indicates that the lattice parameter c increases and a keeps at the primitive value. The grain refining and helium damage result in the diffraction peak broadening. 相似文献