全文获取类型
收费全文 | 17876篇 |
免费 | 3315篇 |
国内免费 | 1736篇 |
专业分类
化学 | 8330篇 |
晶体学 | 236篇 |
力学 | 873篇 |
综合类 | 97篇 |
数学 | 580篇 |
物理学 | 12811篇 |
出版年
2023年 | 168篇 |
2022年 | 359篇 |
2021年 | 436篇 |
2020年 | 609篇 |
2019年 | 580篇 |
2018年 | 557篇 |
2017年 | 596篇 |
2016年 | 733篇 |
2015年 | 636篇 |
2014年 | 864篇 |
2013年 | 1362篇 |
2012年 | 1143篇 |
2011年 | 1297篇 |
2010年 | 1000篇 |
2009年 | 1079篇 |
2008年 | 1055篇 |
2007年 | 1103篇 |
2006年 | 965篇 |
2005年 | 828篇 |
2004年 | 697篇 |
2003年 | 650篇 |
2002年 | 673篇 |
2001年 | 514篇 |
2000年 | 441篇 |
1999年 | 332篇 |
1998年 | 304篇 |
1997年 | 209篇 |
1996年 | 185篇 |
1995年 | 174篇 |
1994年 | 154篇 |
1993年 | 136篇 |
1992年 | 114篇 |
1991年 | 87篇 |
1990年 | 84篇 |
1989年 | 61篇 |
1988年 | 63篇 |
1985年 | 195篇 |
1984年 | 196篇 |
1983年 | 151篇 |
1982年 | 200篇 |
1981年 | 171篇 |
1980年 | 138篇 |
1979年 | 138篇 |
1978年 | 162篇 |
1977年 | 204篇 |
1976年 | 194篇 |
1975年 | 187篇 |
1974年 | 228篇 |
1973年 | 220篇 |
1972年 | 116篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
E. García-Matres N. Stüßer M. Hofmann M. Reehuis 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(1):35-42
The magnetic structures of Mn1-xFexWO4 with x
= 0.0, 0.16, 0.21, 0.225, 0.232, 0.24, 0.27, 0.29, and 1.0 were refined from neutron powder diffraction data. The magnetic phase
diagram could be completed in the coexistence range of different magnetic structures up to x
= 0.29. For the magnetic state at 1.5 K a commensurate antiferromagnetic structure with a propagation vector
= (±1/4, 1/2, 1/2) was found for x
⩽ 0.22 while the magnetic spins order with
= (1/2, 0, 0) for x
≥ 0.22. In the latter phase, additionally, weak magnetic reflections indexed to an incommensurate ordering with
= (- 0.214, 1/2, 0.457) occur in the diffraction pattern up to x
= 0.29 indicating the occurence of a reentrant phase. For 0.12 ⩽
x
⩽ 0.29 the low temperature phases are separated from a magnetic high temperature phase showing only magnetic reflections indexed
to a spin arrangement with
= (1/2, 0, 0). The magnetic phase diagram is discussed qualitatively considering random superexchange between the statistically distributed
Mn2+- and Fe2+-ions in the coexistence range 0.12 ⩽
x
⩽ 0.29 of different magnetic structures related to those of pure MnWO4 and FeWO4.
Received 9 October 2002 Published online 14 March 2003 相似文献
92.
稀磁半导体Zn1-xMnxTe吸收光谱压力红移的理论研究 总被引:1,自引:1,他引:0
以自由Mn2+离子的径向波函数为基础,通过引入电子云延伸效应系数κ来修正这一径向波函数,得到了稀磁半导体Zn1-xMnxTe晶体中Mn2+离子的径向波函数.以此波函数为基础,研究了Zn1-xMnxTe晶体吸收光谱的高压谱移特性,并且得到了吸收谱中四条谱线随压力的红移规律. 相似文献
93.
E. A. El-Amri M. I. Al-Jarallah F. Abu-Jarad Fazal-ur-Rehman 《Radiation measurements》2003,36(1-6):453-456
The uniformity in radon exhalation rates for 46 tiles of granite, marble and ceramic used as construction materials were determined using “Can Technique” employing CR-39 nuclear track detectors (NTDs). On each tile, two sealed cans, each enclosing one NTD fixed at the center of the tile surface area covered by the can, were mounted at two different locations of each individual tiles. The track production rates on the NTDs representing radon exhalation rates were measured. The radon exhalation rates from the surface of individual tiles showed uniform exhalations within the calculated uncertainties of the measured values. This makes Can Technique an alternative simple method to measure radon exhalation rates. Calibration required to convert track production rates into radon exhalation rates for the used can and NTD was done using an active technique. The correlation between the measurements by the two techniques shows a good linear correlation coefficient (0.83). 相似文献
95.
96.
Cordula Grüttner Knut Müller Joachim Teller Fritz Westphal Allan Foreman Robert Ivkov 《Journal of magnetism and magnetic materials》2007
Bionized nanoferrite (BNF) particles with high specific power absorption rates were synthesized in the size range of 20–100 nm by high-pressure homogenization for targeted cancer therapy with alternating magnetic fields. Several strategies were used to conjugate antibodies to the BNF particles. These strategies were compared using an immunoassay to find optimal conditions to reach a high immunoreactivity of the final antibody–particle conjugate. 相似文献
97.
An effect of Berry’s phase on the NQR spectrum of the rotating powder sample is described and applied for the determination of the electric field gradient asymmetry. The proposed method involves the analysis of the frequency singularities in the NQR powder patterns of the rotating samples. The Berry’s phases for the eigenstates, associated with an adiabatically changing quadrupole hamiltonian, are calculated for nuclei with a spin I = 3/2 and I = 1 as a function of the asymmetry parameter. 相似文献
98.
A finite element solution of the Navier-Stokes equations for steady flow under the magnetic effect through a double-branched two-dimensional section of a three-dimensional model of the canine aorta is discussed. The numerical scheme involves transforming the physical co-ordinates to a curvilinear boundary-fitted co-ordinate system. The shear stress at the wall is calculated for a Reynolds number of 1000 with the branch-to-main aortic flow rate ratio as a parameter. The results are compared with earlier works involving experimental data and found to be in reasonable qualitative agreement. The steady flow, shear stress and branch flow under the effect of a magnetic field have been discussed in detail. 相似文献
99.
Deák L. Bottyán L. Major M. Nagy D. L. Spiering H. Szilágyi E. Tanczikó F. 《Hyperfine Interactions》2002,144(1-4):45-52
Hyperfine Interactions - Synchrotron Mössbauer Reflectometry (SMR), the grazing incidence nuclear resonant scattering of synchrotron radiation, can be applied to perform depth-selective phase... 相似文献
100.
The methods for the few-body system are introduced to investigate the states of the barrier Li quantumdots (QDs) in an arbitrary strength of magnetic field. The configuration, which consists of a positive ion located on thez-axis at a distance d from the two-dimensional QD plane (the x-y plane) and three electrons in the dot plane boundby the positive ion, is called a barrier Li center. The system, which consists of three electrons in the dot plane bound bythe ion, is called a barrier Li QD. The dependence of energy of the state of the barrier Li QD on an external magneticfield B and the distance d is obtained. The angular momentum L of the ground states is found to jump not only withthe variation of B but also with d. 相似文献