全文获取类型
收费全文 | 23727篇 |
免费 | 4074篇 |
国内免费 | 2863篇 |
专业分类
化学 | 17589篇 |
晶体学 | 325篇 |
力学 | 1409篇 |
综合类 | 259篇 |
数学 | 2475篇 |
物理学 | 8607篇 |
出版年
2024年 | 52篇 |
2023年 | 529篇 |
2022年 | 687篇 |
2021年 | 851篇 |
2020年 | 996篇 |
2019年 | 962篇 |
2018年 | 810篇 |
2017年 | 769篇 |
2016年 | 1142篇 |
2015年 | 1147篇 |
2014年 | 1336篇 |
2013年 | 1695篇 |
2012年 | 2151篇 |
2011年 | 2227篇 |
2010年 | 1546篇 |
2009年 | 1379篇 |
2008年 | 1543篇 |
2007年 | 1504篇 |
2006年 | 1305篇 |
2005年 | 1142篇 |
2004年 | 817篇 |
2003年 | 712篇 |
2002年 | 654篇 |
2001年 | 496篇 |
2000年 | 460篇 |
1999年 | 515篇 |
1998年 | 378篇 |
1997年 | 386篇 |
1996年 | 321篇 |
1995年 | 317篇 |
1994年 | 315篇 |
1993年 | 266篇 |
1992年 | 212篇 |
1991年 | 205篇 |
1990年 | 191篇 |
1989年 | 121篇 |
1988年 | 95篇 |
1987年 | 98篇 |
1986年 | 63篇 |
1985年 | 51篇 |
1984年 | 46篇 |
1983年 | 28篇 |
1982年 | 30篇 |
1981年 | 19篇 |
1980年 | 13篇 |
1977年 | 6篇 |
1975年 | 11篇 |
1974年 | 8篇 |
1972年 | 11篇 |
1971年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Tao Jin Feng-Xian Jiang Xiao-Li Li Fang Wang Xiao-Hua Shen Rui-Qiang Zhang Hai-Shun Wu 《Applied Surface Science》2006,253(5):2708-2712
CoPt/Ag and [C/CoPt]n/Ag thin films have been prepared onto the glass substrates by magnetron sputtering. We investigated the evolution of texture and magnetic properties of CoPt/Ag and [C/CoPt]n/Ag films. The results show that C-doping plays an important role in improving (0 0 1) texture, improving the order parameter S, reducing the intergrain interactions, and making the magnetization reversal mechanism more close to Stoner-Wolfarth rotational mechanism. The growth mechanism of (0 0 1) texture also seems to be related strongly to the films thickness. Our results show that the highly (0 0 1)-oriented films with ordered fct phase have a significant potential for the perpendicular media of extremely high-density recording. 相似文献
72.
A novel field emission pressure sensor has been achieved utilizing carbon nanotubes (CNTs) as the electron source. The sensor consists of the anode sensing film fabricated by wet etching process and multi-wall carbon nanotubes (MWNTs) cathode in the micro-vacuum chamber. MWNTs on the silicon substrate were grown by thermal CVD. The prototype pressure sensor has a measured sensitivity of about 0.17-0.77 nA/Pa (101-550 KPa). The work shows the potential use of CNTs-based field-emitter in microsensors, such as accelerometers and tactile sensors. 相似文献
73.
74.
基于一个描述夸克胶子火柱演化的相对论流体力学模型,研究了夸克相、强子相互作用以及非热过程(DrellYan对、粲强子衰变)的中等质量双轻子的产生.发现由于相边对夸克胶子物质演化的影响和RHIC能量核碰撞产生的夸克胶子物质具有高的初始温度,夸克相对双轻子的贡献显著增强,比那些来自强子相互作用的贡献重要,甚至能与来自非热的贡献比较.表明中等质量双轻子的增强是一个在核碰撞中产生了夸克胶子物质的可能信号.
关键词:
夸克-胶子物质
双轻子增强
相对论流体力学模型 相似文献
75.
The behavior of a two-level entangled atom in an optical field with circular polarization is studied in this paper. The interaction of an optical field and one of the entangled atoms is analyzed in detail. A general solution of the SchrAo¨Gdinger equation about the motion of the entangled atom is obtained. The properties of the action are dependent on the initial state of the atom. By detecting the entangled atom out of the field, we can obtain the state of the other atom moving in the field. It is shown that the state of the atom out of the field will influence the energies of the split-levels of the atom in the field. 相似文献
76.
In this note, we study convergence rates in the law of large numbers for independent and identically distributed random variables under sublinear expectations. We obtain a strong L^p-convergence version and a strongly quasi sure convergence version of the law of large numbers. 相似文献
77.
78.
研究了基于级联二阶非线性的铌酸锂波导全光波长变换器的特性.首先从耦合模方程出发,比较了数值分析结果与小信号近似分析的结果.其次在数值分析基础上,分析了铌酸锂晶体的温度变化导致相应基频光波波长与极化反转光栅周期的变化关系.最后分析了在不同相互作用长度下,转换的光波功率与有效基频光波波长带宽、温度调谐带宽、极化反转光栅周期带宽等关系,以对全光波长变换器件进行优化设计
关键词:
级联二阶非线性
波长变换
准位相匹配
铌酸锂光波导 相似文献
79.
Y. Qu J.X. Zhang A. Uddin C.Y. Liu S. Yuan M.C.Y. Chan B. Bo G. Liu H. Jiang 《Applied Physics A: Materials Science & Processing》2006,82(2):305-308
Ridge-waveguide InGaAsN triple-quantum-well strain-compensated lasers grown by metal organic chemical vapor deposition were fabricated with pulsed anodic oxidation. The laser’s output power reached 145 mW in continuous-wave mode at room temperature for a 4-?m -stripe-width laser. Continuous-wave single longitudinal mode operation was maintained at a high injection current level with a wavelength of 1287.3 nm at room temperature. Single longitudinal mode operation at 1317.2 nm was achieved at twice the threshold current at 100 °C. The band gap of InGaAsN in the quantum wells at different temperatures was calculated and compared to the measured temperature-dependent laser wavelength. 相似文献
80.
X.J. Liu E.Y. Jiang Z.Q. Li B.L. Li W.R. Li A. Yu P. Wu H.L. Bai 《Journal of magnetism and magnetic materials》2006
We have investigated the magnetic, electrical transport and electron spin resonance (ESR) properties of polycrystalline Nd0.85Na0.15MnO3 prepared by sol–gel method. A ferromagnetic–paramagnetic (FM–PM) transition is observed around 110 K, which is not accompanied by a metal–insulator transition. The sample displays the complete PM state associated with the ESR spectra fitted by single Lorentzian line shape above 130 K. Below 130 K, ESR spectra become distorted and then linewidth increases rapidly, where short-range magnetic order develops and coexists with PM phase due to the inhomogeneous magnetic state. In addition, the large difference between the activation energies obtained from the resistivity and ESR parameters (peak-to-peak linewidth and line intensity) at the frame of adiabatic small polaron hopping model is pointed out for Nd0.85Na0.15MnO3. 相似文献