全文获取类型
收费全文 | 211637篇 |
免费 | 5410篇 |
国内免费 | 2281篇 |
专业分类
化学 | 119911篇 |
晶体学 | 3294篇 |
力学 | 8809篇 |
综合类 | 71篇 |
数学 | 20350篇 |
物理学 | 66893篇 |
出版年
2020年 | 1770篇 |
2019年 | 1836篇 |
2018年 | 1957篇 |
2016年 | 3205篇 |
2015年 | 2479篇 |
2014年 | 3410篇 |
2013年 | 9167篇 |
2012年 | 6877篇 |
2011年 | 8290篇 |
2010年 | 5525篇 |
2009年 | 5405篇 |
2008年 | 7124篇 |
2007年 | 7156篇 |
2006年 | 6852篇 |
2005年 | 6145篇 |
2004年 | 5519篇 |
2003年 | 4821篇 |
2002年 | 4709篇 |
2001年 | 6065篇 |
2000年 | 4635篇 |
1999年 | 3880篇 |
1998年 | 3012篇 |
1997年 | 3057篇 |
1996年 | 2997篇 |
1995年 | 2753篇 |
1994年 | 2592篇 |
1993年 | 2497篇 |
1992年 | 2918篇 |
1991年 | 2816篇 |
1990年 | 2735篇 |
1989年 | 2734篇 |
1988年 | 2665篇 |
1987年 | 2655篇 |
1986年 | 2467篇 |
1985年 | 3317篇 |
1984年 | 3337篇 |
1983年 | 2740篇 |
1982年 | 2937篇 |
1981年 | 2865篇 |
1980年 | 2777篇 |
1979年 | 2903篇 |
1978年 | 3148篇 |
1977年 | 2970篇 |
1976年 | 2862篇 |
1975年 | 2710篇 |
1974年 | 2656篇 |
1973年 | 2690篇 |
1968年 | 1938篇 |
1967年 | 2134篇 |
1966年 | 1924篇 |
排序方式: 共有10000条查询结果,搜索用时 718 毫秒
991.
R. Guerrero F.G. Aliev R. Villar J. Hauch M. Fraune G. Güntherodt K. Rott H. Brückl G. Reiss 《Journal of magnetism and magnetic materials》2006
We report on tunnelling magnetoresistance (TMR), current–voltage (IV) characteristics and low-frequency noise in epitaxially grown Fe(1 1 0)/MgO(1 1 1)/Fe(1 1 0) magnetic tunnel junctions (MTJs) with dimensions from 2×2 to 20×20 μm2. The evaluated MgO energy barrier (0.50±0.08 eV), the barrier width (13.1±0.5 Å) as well as the resistance times area product (7±1 MΩ μm2) show relatively small variation, confirming a high quality epitaxy and uniformity of all MTJs studied. At low temperatures (T<10 K) inelastic electron tunneling spectroscopy (IETS) shows anomalies related to phonons (symmetric structures below 100 meV) and asymmetric features above 200 meV. We explain the asymmetric features in IETS as due to generation of electron standing waves in one of the Fe electrodes. The noise power, though exhibiting a large variation, was observed to be roughly anti-correlated with the TMR. Surprisingly, for the largest junctions we observed a strong enhancement of the normalized low-frequency noise in the antiparallel magnetic configuration. This behavior could be related to the influence of magnetostriction on the characteristics of the insulating barrier through changes in local barrier defects structure. 相似文献
992.
Half-lives of the 2νββ decay are calculated in the proton-neutron QRPA for76Ge,82Se,100Mo,128,130Te,136Xe and150Nd. The strength of the particle-particle interaction, which plays a decisive role for a reliable evaluation of the half-lives, is determined from a QRPA calculation of singleβ + decays. The 2ν decay rates calculated with the interaction strength fitted in this way are strongly suppressed and found to be consistent with the existing experimental data. Effects of the ground-state correlations on the suppression are investigated. On the other hand, the present calculation indicates limitations of the QRPA approach. 相似文献
993.
Oil migration in filled chocolates limits shelf life due to texture changes and loss of visual appeal. Spatial and temporal
oil concentration changes of a two-layer chocolate and peanut butter filling system, which models a filled chocolate, were
monitored by magnetic resonance imaging. Formulations of chocolate varied with respect to particle size, milk fat content
and emulsifier level. Sorption-time experimental data was used to establish the best fit diffusion coefficient for a Fickian
diffusion model. On the basis of the comparison of spatial experimental data to the model, Fickian diffusion alone does not
account for oil migration.
Authors' address: Michael J. McCarthy, Department of Food Science and Technology, University of California, One Shields Avenue,
Davis, CA 95616, USA 相似文献
994.
We discuss how synergetic information, i.e. the compressed Shannon information of the order parameters, which is produced by the cooperativity of the system, can be determined experimentally, especially in fluids. 相似文献
995.
T Niwa H Yoshizumi A Tatematsu S Matsuura T Nagatsu 《Journal of chromatography. A》1989,493(2):347-352
996.
997.
998.
999.
1000.
We study the transversal spin–spin correlations in the non-equilibrium steady state of the XY chain constructed by coupling a finite cutout of the chain to the two infinite parts to its left and right acting as thermal reservoirs at different temperatures. We prove that the spatial decay of these correlations is at least exponentially fast. 相似文献