全文获取类型
收费全文 | 2075篇 |
免费 | 41篇 |
国内免费 | 7篇 |
专业分类
化学 | 1162篇 |
晶体学 | 31篇 |
力学 | 55篇 |
数学 | 245篇 |
物理学 | 630篇 |
出版年
2022年 | 26篇 |
2020年 | 34篇 |
2019年 | 39篇 |
2018年 | 34篇 |
2017年 | 28篇 |
2016年 | 54篇 |
2015年 | 35篇 |
2014年 | 38篇 |
2013年 | 138篇 |
2012年 | 88篇 |
2011年 | 114篇 |
2010年 | 65篇 |
2009年 | 56篇 |
2008年 | 65篇 |
2007年 | 76篇 |
2006年 | 69篇 |
2005年 | 53篇 |
2004年 | 54篇 |
2003年 | 45篇 |
2002年 | 46篇 |
2001年 | 47篇 |
2000年 | 40篇 |
1999年 | 29篇 |
1998年 | 24篇 |
1997年 | 18篇 |
1996年 | 23篇 |
1995年 | 19篇 |
1994年 | 44篇 |
1993年 | 30篇 |
1992年 | 46篇 |
1991年 | 28篇 |
1990年 | 39篇 |
1989年 | 28篇 |
1988年 | 26篇 |
1987年 | 23篇 |
1986年 | 27篇 |
1985年 | 26篇 |
1984年 | 35篇 |
1983年 | 27篇 |
1982年 | 30篇 |
1981年 | 25篇 |
1980年 | 19篇 |
1979年 | 36篇 |
1978年 | 36篇 |
1977年 | 27篇 |
1976年 | 19篇 |
1975年 | 20篇 |
1974年 | 18篇 |
1973年 | 23篇 |
1970年 | 14篇 |
排序方式: 共有2123条查询结果,搜索用时 187 毫秒
11.
Heavy ion irradiation in the electronic stopping power region induces macroscopic dimensional change in metallic glasses and introduces magnetic anisotropy in some magnetic materials. The present work is on the irradiation study of ferromagnetic metallic glasses, where both dimensional change and modification of magnetic anisotropy are expected. Magnetic anisotropy was measured using Mössbauer spectroscopy of virgin and irradiated Fe40Ni40B20 and Fe40Ni38Mo4B18 metallic glass ribbons. 90 MeV 127I beam was used for the irradiations. Irradiation doses were 5×1013 and 7.5×1013 ions/cm2. The relative intensity ratios D 23 of the second and third lines of the Mössbauer spectra were measured to determine the magnetic anisotropy. The virgin samples of both the materials display in-plane magnetic anisotropy, i.e., the spins are oriented parallel to the ribbon plane. Irradiation is found to cause reduction in magnetic anisotropy. Near-complete randomization of magnetic moments is observed at high irradiation doses. Correlation is found between the residual stresses introduced by ion irradiation and the change in magnetic anisotropy. 相似文献
12.
D. M. Bhardwaj D. C. Jain S. Dalela Ravi Kumar N. L. Saini K. B. Garg 《Physica B: Condensed Matter》2004,350(4):366-374
We have made the XAFS measurements at the Cr–K-edge on natural Indian ruby single crystals (corundum) and its two irradiated samples with fluence 1×1012 Ni6+ and 5×1012 Ni6+ ions/cm2. Irradiated samples show interesting changes in their physical appearance. XANES measurements show progressive decrease in Δoct value on increase of Ni fluence in irradiated samples. EXAFS measurements on these samples show decrease in Cr–O distance on increase of Ni fluence. Lowering of Δoct value is correlated with the increase of Cr–O distance. 相似文献
13.
The highest resolution in a lithographic process is often determined by the properties of the resist material. With the currently used polymeric resists, a resolution of better than 100 nm has been achieved under manufacturing conditions, but the future nanoscale devices will require a 10 times superior resolution. In this paper we present an overview of the resist materials, especially with regard to limiting resolution. In principle, inorganic resists should have higher limiting resolution than polymer resists due to smaller fundamental structural units and stronger bonds in the former. However, compositional and/or structural inhomogeneities may limit their ultimate resolution. New results are presented that indicate chalcogenide glasses as promising photo and electron beam resists, which also have the advantages of greater hardness, resistance to acids, easy fabrication in thin film form, and the unique phenomena like radiation enhanced diffusion. 相似文献
14.
Model based online diagnosis of unbalance and transverse fatigue crack in rotor systems 总被引:7,自引:0,他引:7
A model based technique for online identification of malfunctions in rotor systems is discussed. Presence of fault changes the dynamic behavior of the system. This change is taken into account by equivalent loads acting on the undamaged system model. Equivalent loads are fictitious forces and moments acting on the undamaged system model, which generate a dynamic behavior identical to that of the real damaged system. The mathematical representation of equivalent loads is referred to as Fault Model. The work focuses on developing a fault model for a transverse fatigue crack in shaft and testing it through simulated studies. The basic principle of the technique is validated for unbalance identification, through numerical simulations as well as by experiments on a real rotor system. 相似文献
15.
16.
A data set of 29 experimentally determined Newby shifts in rare-earth nuclei is examined for the reliability of each values.
Using this data set, Newby shifts are obtained which are free from the Coriolis and the particle-particle coupling effects.
These new empirical values help resolve the failure of a recently proposed rule for the sign of the Newby shift in the {5/2[413]p − 5/2[642]n} configuration of160Tb and the {5/2[402]p − 5/2[512]n} configuration of174Lu. Also the Newby shifts are significantly modified in two other cases namely the {1/2[411]p − 1/2[521]n} configuration in168Tm and the {1/2[541]p − 1/2[521]n} configuration in172Lu. Only marginal changes are seen in the rest of the cases in the rare-earth nuclei. 相似文献
17.
18.
19.
20.