全文获取类型
收费全文 | 753篇 |
免费 | 175篇 |
国内免费 | 76篇 |
专业分类
化学 | 311篇 |
晶体学 | 14篇 |
力学 | 7篇 |
综合类 | 5篇 |
数学 | 22篇 |
物理学 | 645篇 |
出版年
2024年 | 3篇 |
2023年 | 6篇 |
2022年 | 46篇 |
2021年 | 32篇 |
2020年 | 54篇 |
2019年 | 18篇 |
2018年 | 16篇 |
2017年 | 29篇 |
2016年 | 44篇 |
2015年 | 27篇 |
2014年 | 41篇 |
2013年 | 52篇 |
2012年 | 52篇 |
2011年 | 49篇 |
2010年 | 38篇 |
2009年 | 58篇 |
2008年 | 59篇 |
2007年 | 57篇 |
2006年 | 37篇 |
2005年 | 36篇 |
2004年 | 35篇 |
2003年 | 33篇 |
2002年 | 28篇 |
2001年 | 32篇 |
2000年 | 22篇 |
1999年 | 16篇 |
1998年 | 17篇 |
1997年 | 13篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有1004条查询结果,搜索用时 265 毫秒
911.
A generalized finite element formulation is proposed for the study of the spin-dependent ballistic transport of electron through the two-dimensional quantum structures with Rashba spin-orbit interactions (SOI). Thetransmission coefficient, conductance, the total and local polarization are numerically calculated and discussed as the Rashba coefficient, the geometric sizes, and incident energy are changed in the T-shaped devices. Some interesting features are found in the proper parameter regime. The polarization has an enhancement as the Rashba coefficient becomes stronger. The polarization valley is rigid in the regime of the conductance plateaus since the local interference among the polarized multi-wave modes. The Rashba interactions coupling to geometry in sizes could form the structure-induced Fano-Rashba resonance. In the wider stub, the localized spin lattice of electron could be produced. The conductance plateaus correspond to weakpolarizations. Strong polarizations appear when the stub sizes, incident energy, and the Rashba coupling coefficient are matched. The resonances are formed in a wide Fermi energy segment easily. 相似文献
912.
In this study, we analyzed three fabricated pigments from ancient artifacts in China. The purple pigment was obtained from a painted pottery figurine unearthed from the Chu Tombs group of the Western Han dynasty in Xuzhou, Jiangsu Province. The dark blue dye was from silk textiles in the Palace Museum. The green pigment was from decorative paintings on ancient architectures in the Palace Museum. These pigments were analyzed with Raman microscopy (RM), energy‐dispersive X‐ray (EDX) analytic spectroscopy and polarized light microscopy (PLM). By comparing their Raman spectra with standard samples, the primary ingredients of the purple pigment and the dark blue dye were found to be Han purple and indigo, respectively. However, the green pigment could not be identified by RM because of strong fluorescence. It was then confirmed to be emerald green by using EDX analytic microscopy and PLM. We also describe the traditional manufacturing methods of these pigments and their applications on artifacts in Chinese history. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
913.
F. Q. Liu H. R. Xia W. L. Gao D. G. Ran S. Q. Sun Z. C. Ling P. Zhao H. J. Zhang S. R. Zhao J. Y. Wang 《Crystal Research and Technology》2007,42(3):260-265
Polarized absorption spectra of Nd:LuVO4 crystal were measured at room temperature. The optical parameters of π polarization and σ polarization were calculated by Judd‐Ofelt theory. Meanwhile, the phenomenological intensity parameters: Ω2, Ω4, and Ω6 were obtained, then the parameters were used to calculate the luminescence parameters of Nd:LuVO4 crystal, including oscillator strengths, fluorescence branching ratio, radiative lifetime and integrated emission cross‐sections. Experiments of a‐cut and c‐cut Nd:LuVO4 lasers were also performed, and opt‐opt conversion efficiency and slope efficiency were 40.3%, 50.5% for a‐cut and 23.6%, 30.9% for c‐cut, respectively. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
914.
An experimental approach to two-dimensional, viscoelastic, steadily moving rolling contact is described. The photoviscoelastic technique is employed for the analysis of rolling contact stresses between a viscoelastic plate and a rigid rolling cylinder in which the principal axes of stress, strain and birefringence are not coincident with each other. Using an elliptically polarized white light, the distribution of isochromatic fringe order and the principal axes of birefringence at an instant are determined from a single photoviscoelastic image. The time variations of the differences of the principal stresses and strains, as well as their directions, are obtained by use of the optical constitutive equations of photoviscoelasticity. The experimental results involving the time variation of the stresses around the contact surface and their distributions are analyzed. 相似文献
915.
916.
Sourendu Gupta D Indumathi S Banerjee R Basu M Dittmar RV Gavai F Gelis D Ghosh Sourendu Gupta D Indumathi Asmita Mukherjee 《Pramana》2000,55(1-2):327-333
This is the report of the QCD working group at WHEPP-6. Discussions and work on heavy ion collisions, polarized scattering,
and collider phenomenology are reported. 相似文献
917.
Tsukahara S 《Analytica chimica acta》2006,556(1):112-120
Attenuated total internal reflection (ATR) spectroscopy with an s- or p-polarized visible light was examined for some species of protonated 5,10,15,20-tetraphenylporphine (tpp) at toluene/aqueous H2SO4 (3-6 mol dm−3) interface. Tpp initially dissolved in the toluene phase was diprotonated at the interface to form monomeric H2tpp2+, the absorption peak of which was 438 nm. At the same time, a long H2tpp2+ oligomer was formed, the absorption peak of which was 448 nm. The two interfacial species were transient. Just after their disappearance, a rod-shaped H2tpp2+ associate was formed at the interface, the absorption peak of which was 417 and 478 nm. The former and latter wavelengths corresponded to H- and J-bands of the associate, respectively. Theoretical calculation of the strength of electric field of light at the interface allowed one to estimate the interfacial concentration of the three species with measured reflection absorbance (AR). The monomeric H2tpp2+ and its oligomer were at sub-monolayer levels, whereas the associate was at a multilayer level. Reflection absorption anisotropy (KR), which was calculated from AR with the s- and p-polarized lights, was adopted for the evaluation of out-of-plane orientation of the interfacial species for the first time. The KR value suggested that the rod-shaped associate lay at the interface. 相似文献
918.
Isolated attosecond pulse generation with few-cycle two-color counter-rotating circularly polarized laser pulses
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Most of the schemes for generating isolated attosecond pulses(IAP) are sensitive to the carrier-envelope phase(CEP)of the driving lasers. We propose a scheme for generating IAP using two-color counter-rotating circularly polarized(TCCRCP) laser pulses. The results demonstrate that the dependence of the IAP generation on CEP stability is largely reduced in this scheme. IAP can be generated at most of CEPs. Therefore, the experiment requirements become lower. 相似文献
919.
Atomic magnetometer(AM) operated in a spin-exchange relaxation-free(SERF) regime features superior sensitivity and non-cryogenic operation, and thus is competitive with the best superconducting quantum interference devices.Previously, SERF AM with f T/Hz~(1/2) level sensitivity commonly acted as a single-axis sensor. Here we demonstrate a dual-axis SERF AM capable of simultaneously and independently detecting x-and y-field components with a sensitivity of 20 f T/Hz~(1/2). As there is no necessity to worry about the cross-talk effects arising from field modulations, the dual-axis scheme proposed here is of particular interest to AM array and hence the biomagnetic applications. 相似文献
920.
为了研究调整架角度误差以及波片与光源波长不匹配对线偏振光经过1/4波片之后偏振态的影响,本文利用坐标变换法得到1/4波片的琼斯矩阵,并用琼斯矩阵表示各偏振态。推导出波片与光源不匹配时对偏振态的影响理论模型。当考虑到调整架的角度误差时,对入射光偏振态以及波片的琼斯矩阵表达式做引入角度误差的泰勒展开,最后得到和实验结果匹配的仿真曲线。仿真结果表明,当采用808 nm 1/4波片对795 nm波长的线偏振光作用时,在不考虑调整误差的理想情况下出射光椭圆度最高为0.9746,考虑调整误差时,对应理想情况下椭圆度最高为0.96,椭圆度最高点偏移1.72°。仿真和实验结果为进一步分析泵浦光椭圆度对原子参数的影响提供了依据。 相似文献