全文获取类型
收费全文 | 6610篇 |
免费 | 261篇 |
国内免费 | 369篇 |
专业分类
化学 | 2877篇 |
晶体学 | 49篇 |
力学 | 148篇 |
综合类 | 5篇 |
数学 | 110篇 |
物理学 | 4051篇 |
出版年
2023年 | 45篇 |
2022年 | 69篇 |
2021年 | 85篇 |
2020年 | 139篇 |
2019年 | 117篇 |
2018年 | 149篇 |
2017年 | 114篇 |
2016年 | 223篇 |
2015年 | 200篇 |
2014年 | 250篇 |
2013年 | 317篇 |
2012年 | 770篇 |
2011年 | 760篇 |
2010年 | 555篇 |
2009年 | 613篇 |
2008年 | 452篇 |
2007年 | 515篇 |
2006年 | 306篇 |
2005年 | 224篇 |
2004年 | 213篇 |
2003年 | 156篇 |
2002年 | 177篇 |
2001年 | 96篇 |
2000年 | 105篇 |
1999年 | 103篇 |
1998年 | 110篇 |
1997年 | 43篇 |
1996年 | 40篇 |
1995年 | 40篇 |
1994年 | 23篇 |
1993年 | 30篇 |
1992年 | 17篇 |
1991年 | 15篇 |
1990年 | 27篇 |
1989年 | 17篇 |
1988年 | 16篇 |
1987年 | 8篇 |
1986年 | 15篇 |
1985年 | 13篇 |
1984年 | 9篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 11篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 5篇 |
排序方式: 共有7240条查询结果,搜索用时 15 毫秒
101.
F. Honda A.V. Andreev V. Sechovský Y. Homma Y. Shiokawa 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(3):313-318
Single crystals of U(Ni1-xPdx)2Si2 with x = 0.05, 0.09 and 0.135 have been grown. Magnetization and electrical resistivity measurements were performed in a wide range
of temperatures and magnetic fields in order to study stability of magnetic phases in the solid solutions between UNi2Si2 and UPd2Si2 with a special emphasis on the type of ground state. In UPd2Si2 the simple AFI-type antiferromagnetic structure of U moments is observed at low temperatures. UNi2Si2 adopts the uncompensated AF structure (UAF) with the + + - stacking of U moments along the c-axis and consequently this compound exhibits a spontaneous magnetization corresponding to 1/3 of the U moment. The substitution
of Pd for Ni leads to a rapid decay of the spontaneous magnetization. The evolution of magnetization and electrical resistivity
behavior with Pd doping is tentatively attributed to the coexistence of the AF-I and UAF phases in the ground state of U(Ni0.91Pd0.09)2Si2 and U(Ni0.865Pd0.135)2Si2. In this scenario, the volume fraction of the AF-I phase rapidly grows with Pd doping on account of the UAF. At lowest temperatures
an irreversible transition to the UAF phase is observed when a sufficiently high magnetic field is applied along the c-axis.
Received 28 March 2002 / Received in final form 8 August 2002 Published online 19 December 2002
RID="a"
ID="a"e-mail: sech@mag.mff.cuni.cz 相似文献
102.
Microwave-assisted synthesis of SrFe12O19 hexaferrites 总被引:1,自引:0,他引:1
Wang Zhanyong Zhong Liuming Qian Huichun Fang Yongzheng Xu Jiayue 《Journal of magnetism and magnetic materials》2010,322(18):2782-2785
Ultra-fine and homogeneous SrFe12O19 hexaferrites were synthesized by a microwave-assisted calcination route. The calcined precursors were prepared by a sol-gel auto-combustion method using Fe(NO3)3·9H2O, Sr(NO3)2 and citric acid as starting materials. The structures, powder morphology and magnetic properties of the products were characterized by X-ray diffraction, scanning electron microscope and vibrating sample magnetometer. The results showed that microwaves are helpful to reduce the calcination temperature and shorten the calcination time. The ferrites with saturation magnetization, remanence and intrinsic coercivity of 54.80 emu/g, 29.52 emu/g and 5261 Oe, respectively, were obtained in samples calcined at 800 °C for 80 min. 相似文献
103.
在EAST中n=4的共振磁扰动下观察到明显的等离子体旋转制动效应,其分布具有全局性,且峰值靠近等离子体中心。利用模拟得到的新经典环向粘滞(NTV)力矩来反演等离子体环向角速度的变化,结果表明在大部分径向区域与实验测量的速度变化符合得较好,量值上相差约1~2倍。 相似文献
104.
《Physics letters. A》2020,384(4):126101
Classical electromagnetism with magnetic monopoles is not a Hamiltonian field theory because the Jacobi identity for the Poisson bracket fails. The Jacobi identity is recovered only if all of the species have the same ratio of electric to magnetic charge or if an electron and a monopole can never collide. Without the Jacobi identity, there are no local canonical coordinates or Lagrangian action principle. To build a quantum field of magnetic monopoles, we either must explain why the positions of electrons and monopoles can never coincide or we must resort to new quantization techniques. 相似文献
105.
《Physics letters. A》2020,384(32):126826
In this paper, hydrogenation is used for the generation of band gap in silicene and the hydrogenated silicene is then studied for its spintronic application. Upon hydrogenation, silicene transforms into a wide band gap material with a band gap of 3.32 eV. Parameters like magneto-resistance and spin-filtering efficiency of magnetic tunnel junction (MTJ) with CrO2 as semi-metallic electrodes and hydrogenated silicene as scattering region are found to increase compared to pristine silicene as scattering region. The simulation results show that the magneto-resistance of hydrogenated silicene remains above 85% (higher than the pristine counterpart) for the entire bias range. In addition, the spin-filtering efficiency in hydrogenated silicene reaches a value as high as 96% whereas in case of pristine silicene it remains below 90% for the entire bias range. 相似文献
106.
《Current Applied Physics》2020,20(5):638-642
A series of bio-silica incorporated barium-ferrite-composites with the composition of (x)Bio-SiO2:(80-x)γ-Fe2O3:(20)BaO, where x = 0, 1, 2, and 3 wt% were prepared using the modified solid-state reaction method. The influence of different bio-silica (extricated from sintered rice husk) contents on the surface morphologies, structures, and magnetic characteristics of these composites were assessed. The relative complex permittivity and permeability were resolved using the Nicholson-Ross-Weir strategy in the frequency range of 8–13 GHz. Meanwhile, the reflection loss was estimated through the transmission/reflection line theory to assess the MW absorption properties of the composites. Incorporation of the bio-silica in the barium ferrite composites generated a new hexagonal phase (Ba3Fe32O51) and a tetragonal phase (BaFeSi4O10) which led to a decrease in the saturation magnetization and significant shift in the MW frequency absorption peak positions. 相似文献
107.
M. C. Desjonquères C. Barreteau G. Autès D. Spanjaard 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(1):23-27
We show that considerable orbital magnetic moments and magneto-crystalline anisotropy energies are obtained for a Fe monatomic
wire described in a tight-binding method with intra-atomic electronic interactions treated in a full Hartree Fock (HF) decoupling
scheme.
Even though the use of the orbital polarization ansatz with simplified Hamiltonians leads to fairly good results when the
spin magnetization is saturated this is not the case of unsaturated systems. We conclude that the full HF scheme is necessary
to investigate low dimensional systems. 相似文献
108.
J. Bansmann A. Kleibert F. Bulut M. Getzlaff P. Imperia C. Boeglin K.-H. Meiwes-Broer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(3):521-528
Mass-filtered cobalt clusters with a size of 8 nm have been deposited in-situ under soft-landing conditions onto Au(111).
The spin and orbital moments of the Co nanoparticles on a Au (111) single crystal have been investigated as a function of
the temperature using the element-specific method of X-ray magnetic circular dichroism in photoabsorption. The results hint
at an temperature-dependent spin-reorientation transition which is discussed with respect to different contribution to the
magnetic anisotropy. Furthermore, by means of an in-situ oxidation experiment, the influence of an exposure to oxygen on the
properties of the cobalt clusters has been investigated. 相似文献
109.
K. Kärkkäinen M. Borgh M. Manninen S. M. Reimann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):225-228
We compare magnetism in two artificial lattice structures, a
quantum dot array formed in a two-dimensional electron gas and an optical lattice loaded with repulsive, contact-interacting
fermionic atoms. When the tunneling between the
lattice sites is strong, both lattices are non-magnetic. With reduced tunneling in the tight-binding limit, the shell-filling
of the single-site quantum wells combined with Hund's rule determines the
magnetism. This leads to a systematic magnetic phase diagram with non-magnetic, ferromagnetic and antiferromagnetic phases. 相似文献
110.
Coronary magnetic resonance angiography (MRA) acquired using steady-state free precession (SSFP) sequences tends to suffer from image artifacts caused by local magnetic field inhomogeneities. Flow- and gradient-switching-induced eddy currents are important sources of such phase errors, especially under off-resonant conditions. In this study, we propose to reduce these image artifacts by using a linear centric-encoding (LCE) scheme in the phase-encoding (PE) direction. Abrupt change in gradients, including magnitude and polarity between consecutive radiofrequency cycles, is minimized using the LCE scheme. Results from numeric simulations and phantom studies demonstrated that signal oscillation can be markedly reduced using LCE as compared to conventional alternating centric-encoding (ACE) scheme. The image quality of coronary arteries was improved at both 1.5 and 3.0 T using LCE compared to those acquired using ACE PE scheme (1.5 T: ACE/LCE=2.2+/-0.8/3.0+/-0.6, P=.02; 3.0 T: ACE/LCE=2.1+/-1.1/3.0+/-0.8, P=.01). In conclusion, flow- and eddy-currents-induced imaging artifacts in coronary MRA using SSFP sequence can be markedly reduced with LCE acquisition of PE lines. 相似文献