全文获取类型
收费全文 | 16491篇 |
免费 | 2074篇 |
国内免费 | 1279篇 |
专业分类
化学 | 7003篇 |
晶体学 | 266篇 |
力学 | 297篇 |
综合类 | 33篇 |
数学 | 544篇 |
物理学 | 11701篇 |
出版年
2024年 | 14篇 |
2023年 | 102篇 |
2022年 | 261篇 |
2021年 | 295篇 |
2020年 | 295篇 |
2019年 | 354篇 |
2018年 | 364篇 |
2017年 | 461篇 |
2016年 | 702篇 |
2015年 | 592篇 |
2014年 | 796篇 |
2013年 | 1583篇 |
2012年 | 957篇 |
2011年 | 1252篇 |
2010年 | 888篇 |
2009年 | 1174篇 |
2008年 | 1079篇 |
2007年 | 1241篇 |
2006年 | 927篇 |
2005年 | 835篇 |
2004年 | 753篇 |
2003年 | 604篇 |
2002年 | 607篇 |
2001年 | 503篇 |
2000年 | 499篇 |
1999年 | 429篇 |
1998年 | 325篇 |
1997年 | 225篇 |
1996年 | 269篇 |
1995年 | 231篇 |
1994年 | 190篇 |
1993年 | 161篇 |
1992年 | 168篇 |
1991年 | 98篇 |
1990年 | 74篇 |
1989年 | 65篇 |
1988年 | 80篇 |
1987年 | 58篇 |
1986年 | 37篇 |
1985年 | 50篇 |
1984年 | 41篇 |
1983年 | 21篇 |
1982年 | 35篇 |
1981年 | 35篇 |
1980年 | 17篇 |
1979年 | 17篇 |
1978年 | 15篇 |
1976年 | 14篇 |
1975年 | 9篇 |
1973年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
81.
82.
Yang Ruike Wu Zhensen You Jinguang 《International Journal of Infrared and Millimeter Waves》2003,24(8):1383-1392
The influence of sand and dust storms on modern MMW and satellite communication systems reliability have been paid more attention to. The attenuations induced by sand and dust storms are estimated by means of Mie-theory and Rayleigh approximation, in the case of the tenuous distribution of particles. With the particle density increasing, however, these method become inadequate, the multiple scattering effects then become dominant for attenuation estimation. The attenuations considering multiple scattering effects are estimated by Monte-Carlo and four fluxes method at horizontal paths. At slant paths, based on multi-layer media model, the attenuations considering multiple scattering effects are calculated by layered Monte-Carlo method at 100, 37, 24, and 14GHz. It is shown that the multiple scattering effects should be considered at the attenuation prediction in the sand and dust storm, which the visibility is about 0.5km and smaller than 0.5km and frequency is about 20GHz. Above 30GHz, the multiple scattering effects due to sand and dust particles should be considered, as visibility is about 1km and smaller than 1km at slant paths. 相似文献
83.
单壁碳纳米管的SERS研究 总被引:2,自引:2,他引:0
本文通过改进实验方法,将单壁碳纳米管的乙醇溶液与金胶混合并制作成固体薄膜,使单壁碳纳米管夹裹在金纳米粒子之间,保证了吸附的紧密性,获得了高质量的单壁碳纳米管SERS光谱。不但观测到文献中报道的径向呼吸振动模(RBM)和C-C正切拉伸模(GM)的增强,还在1100-1500cm-1区域观测到一组新峰,其峰形完整并有相当的强度。这些峰在现有的文献中几乎没有报导。文章对这组新峰的出现进行了初步的分析。 相似文献
84.
85.
86.
Using a high resolution Raman spectrometer, we have measured Ar-broadening coefficients in the ν2Q branch of C2H2 for 22 lines at 295 K, 20 lines at 174 K, and 16 lines at 134 K. These lines with J values ranging from 1 to 23 are located in the spectral range 1970.9-1974.3 cm−1. The collisional widths are obtained by fitting each spectral line with a Rautian profile. The resulting broadening coefficients are compared with theoretical values arising from close coupling and coupled states calculations. A satisfactory agreement is obtained at room as well as at low temperatures, especially for odd J lines. By comparing broadening coefficients at 295, 174, and 134 K from a simple power law, the temperature dependence of these broadenings has been determined both experimentally, and theoretically. 相似文献
87.
利用拉曼型的Jaynes-Cummings模型传送两比特的未知原子态 总被引:6,自引:3,他引:3
实现量子态的隐形传送、尤其是多比特量子态的隐形传送在量子信息领域中有非常重要的作用,提出了一种隐形传送两比特未知原子态的方案,在此方案中,用两个两粒子纠缠态代替一个三粒子纠缠态作为量子信道,而且此方案可推广到隐形传送N比特的未知原子态。 相似文献
88.
Fabiano Severo Rodembusch Ndya Pesce da Silveira Dimitrios Samios Leandra Franciscato Campo Valter Stefani 《Journal of Polymer Science.Polymer Physics》2003,41(4):341-350
The solution behavior of new copolymers of methyl methacrylate and benzazole dyes emitting fluorescence because of an intramolecular proton‐transfer mechanism in the electronically excited state has been investigated by static light scattering, fluorescence spectroscopy, ultraviolet–visible, and gel permeation chromatography. In the dilute regime, with tetrahydrofuran (THF) and chloroform as solvents, the copolymers behave as typical polydisperse linear chains in good solvents. The analysis of the osmotic modulus for concentrated solutions in THF (c ≥ 60 g L?1) indicates the existence of an interchain association mechanism. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 341–350, 2003 相似文献
89.
Two structure functions W1(x,Q2) and W2(x,Q2) are determined by using the cross sections measured in the deep inelastic electron-proton scattering experiments at Stanford Linac in the energy range of 5 to 20 GeV. In this paper an alternative mathematical approach have been used in such determination, resulting in a larger number of points in the graphs of the structure functions. 相似文献
90.
采用显微Raman光谱方法对红外目标模拟器中重掺杂Si微电阻桥单元的热传导特性进行研究,根据Si桥的实际特性建立相应的Raman散射模型,通过测量Raman峰位的移动得到高功率激光辐照下测量点的温度.对Si桥桥面分别进行了沿某些特殊线段的逐点线扫描和覆盖全部桥面的面扫描,得到各点的温升及其分布.用基于有限元分析的软件结合Si桥结构参数对各测量点的温升进行了模拟计算,其结果在热导分布的基本趋势上与实验相一致.实验细致地揭示了热导分布的局域起伏,反映出实际器件的不均匀性,为改进器件设计、优化器件性能提供了实验依据.
关键词:
Raman光谱
Si桥
温度分布
热导 相似文献