全文获取类型
收费全文 | 10503篇 |
免费 | 1859篇 |
国内免费 | 1089篇 |
专业分类
化学 | 7314篇 |
晶体学 | 98篇 |
力学 | 626篇 |
综合类 | 54篇 |
数学 | 1170篇 |
物理学 | 4189篇 |
出版年
2024年 | 60篇 |
2023年 | 273篇 |
2022年 | 434篇 |
2021年 | 489篇 |
2020年 | 446篇 |
2019年 | 434篇 |
2018年 | 406篇 |
2017年 | 353篇 |
2016年 | 565篇 |
2015年 | 490篇 |
2014年 | 619篇 |
2013年 | 811篇 |
2012年 | 965篇 |
2011年 | 932篇 |
2010年 | 650篇 |
2009年 | 646篇 |
2008年 | 635篇 |
2007年 | 557篇 |
2006年 | 522篇 |
2005年 | 416篇 |
2004年 | 327篇 |
2003年 | 240篇 |
2002年 | 206篇 |
2001年 | 177篇 |
2000年 | 207篇 |
1999年 | 225篇 |
1998年 | 181篇 |
1997年 | 168篇 |
1996年 | 188篇 |
1995年 | 146篇 |
1994年 | 121篇 |
1993年 | 91篇 |
1992年 | 100篇 |
1991年 | 56篇 |
1990年 | 75篇 |
1989年 | 54篇 |
1988年 | 26篇 |
1987年 | 28篇 |
1986年 | 38篇 |
1985年 | 38篇 |
1984年 | 13篇 |
1983年 | 17篇 |
1982年 | 8篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
341.
三层不对称人工电磁材料界面处表面等离子体激元的理论研究 总被引:1,自引:1,他引:1
从P和S偏振出发.研究了由常规材料/左手材料/负介电常数材料、及常规材料/左手材料/负磁导率材料这两种三层不对称结构界面上表面等离子体激元(Surface plasmon polaritons,SPPs)的存在区域、色散曲线及其激发.观察到表面等离子体激元的性质强烈地依赖于人工电磁材料的组成参量,例如介质板的厚度和等离子体的频率.最后,使用衰减全反射(Attenuated total reflection,ATR)技术,探究了激发和观察表面等离子体激元的可能性.并针对P和s偏振两种情况计算了衰减全反射光谱. 相似文献
342.
A modified Fourier transform profilometry (FTP) based on a fringe pattern with two frequency components is proposed, which provides a larger measuring range than that of the traditional FTP. We analyze the maximum measuring range and give an expression to describe the measurable slope of the height variation limitation of this method. The modified FTP provides us another approach to eliminate frequency overlapping. When the spectra distribution of a measured object is not spherical symmetry, we can avoid the frequency aliasing through projecting a fringe pattern with two frequency components, instead of increasing the density of the projected fringe and the resolution of a CCD camera. The theoretical analysis and primary experiments verified the method. 相似文献
343.
Chunyan Cao Weiping Qin Jisen Zhang Guofeng Wang Peifen Zhu Longzhen Jin 《Optics Communications》2008,281(6):1716-1719
Tm3+/Er3+/Yb3+ tri-doped CaF2 phosphors were synthesized using a hydrothermal method. The phosphors were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and up-conversion (UC) emission spectra. After annealing, the phosphors emitted white light under a 980 nm continuous wave diode laser (CW LD 2 W) excitation. As the excitation power density changed in the range of 20-260 W/cm2, the chromaticity coordinates of the UC light of the phosphor Ca0.885Tm0.005Er0.01Yb0.1F2 fell well in the white region of the 1931 CIE diagram. For the proportion of red, green and blue (RGB) in white light is strict, key factors for achieving UC white light, such as host materials, rare earth ions doping concentrations, annealing temperatures, as well as the excitation power densities, were investigated and discussed. 相似文献
344.
Tingyin Ning Hong Shen Heng Lu Zhihui Sun Lingzhu Cao Dongyi Guan Dongxiang Zhang Guozhen Yang 《Applied Surface Science》2008,254(7):1900-1903
The triangular-shaped Au/ZnO nanoparticle arrays were fabricated on fused quartz substrate using nanosphere lithography. The structural characterization of the Au/ZnO nanoparticle arrays was investigated by atomic force microscopy. The absorption peak due to the surface plasmon resonance of Au particles at the wavelength of about 570 nm was observed. The nonlinear optical properties of the nanoparticle arrays were measured using the z-scan method at a wavelength of 532 nm with pulse duration of 10 ns. The real and imaginary part of third-order nonlinear optical susceptibility, Re χ(3) and Im χ(3), were determined to be 1.15 × 10−6 and −5.36 × 10−7 esu, respectively. The results show that the Au/ZnO nanoparticle arrays have great potential for future optical devices. 相似文献
345.
Using the quantum hydrodynamic (QHD) equations with magnetic field on the Wigner-Maxwell system, the general dielectric tensor and dispersion equation for quantum plasmas were derived. Dispersion relations of one-, two-stream and beam-plasma instabilities in uniform quantum magnetized plasmas are investigated through the new dielectric tensor. The magnetic field which is parallel to the fluid velocity does not work on stream instabilities. The quantum and thermal effects have remarkable impact on two-stream instability. The critical wave number for beam-plasma instability with quantum effects correction is given too. 相似文献
346.
Hui-Juan Cao 《Physics letters. A》2008,372(17):2971-2975
We propose a scheme to detect the chirality for a system consisting of three coupled quantum dots. The chirality is found to be determined by the frequency of the transition between chiral states under the chiral symmetry broken perturbation. The results are important to construct quantum gates and to demonstrate chiral entangle states in the triangle spin dots. 相似文献
347.
In this Letter, synchronization of switched system is investigated based on Lyapunov method. A sufficient condition is derived to ensure the synchronization between two switched systems, and a new communication scheme is also proposed based on this. Furthermore, some secure analysis works, such as return map attack and moving average error attack, are also given to show the security of the proposed scheme. Finally, simulation examples are constructed to verify the theoretical analysis and its application for communication. 相似文献
348.
M.K. Jacobsen G. Cao A.L. Cornelius 《Journal of Physics and Chemistry of Solids》2008,69(9):2237-2239
We have performed room temperature high pressure structural studies on the ferromagnetic perovskite SrRuO3 to 34 GPa. We have also used three different pressure media (silicone fluid, 4:1 methanol:ethanol and argon) to test for possible effects of pressure media on compression data. The orthorhombic perovskite structure is stable to the highest pressure, and the data can be fit with a bulk modulus of with a pressure derivative of for all of the pressure media. We have also examined the high pressure behavior of the RuO6 octahedra using a model that assumes the octahedra are not distorted. Various tilt angles around the ideal cubic perovskite axes are found and can be used to estimate the Ru-O-Ru bond angle that is known to be directly related to the ferromagnetic Curie temperature. For all pressure media, there appears to be a minimum in the Ru-O-Ru bond angle around 15 GPa. Implications for the observed high pressure magnetic behavior of SrRuO3 will be discussed. 相似文献
349.
350.