全文获取类型
收费全文 | 758篇 |
免费 | 11篇 |
国内免费 | 10篇 |
专业分类
化学 | 440篇 |
晶体学 | 4篇 |
力学 | 15篇 |
数学 | 139篇 |
物理学 | 181篇 |
出版年
2020年 | 7篇 |
2019年 | 6篇 |
2016年 | 10篇 |
2014年 | 10篇 |
2013年 | 26篇 |
2012年 | 20篇 |
2011年 | 39篇 |
2010年 | 18篇 |
2009年 | 16篇 |
2008年 | 33篇 |
2007年 | 22篇 |
2006年 | 36篇 |
2005年 | 36篇 |
2004年 | 23篇 |
2003年 | 28篇 |
2002年 | 33篇 |
2001年 | 29篇 |
2000年 | 20篇 |
1999年 | 15篇 |
1998年 | 7篇 |
1997年 | 11篇 |
1996年 | 19篇 |
1995年 | 13篇 |
1994年 | 15篇 |
1993年 | 17篇 |
1992年 | 22篇 |
1991年 | 12篇 |
1990年 | 12篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1975年 | 10篇 |
1974年 | 9篇 |
1973年 | 10篇 |
1972年 | 6篇 |
1971年 | 7篇 |
1970年 | 11篇 |
1969年 | 5篇 |
1939年 | 5篇 |
排序方式: 共有779条查询结果,搜索用时 31 毫秒
1.
2.
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
3.
4.
J. Telser H. -I. Lee E. T. Smith H. Huang P. Brereton M. W. W. Adams R. C. Conover M. K. Johnson B. M. Hoffman 《Applied magnetic resonance》1998,14(2-3):305-321
The hyperthermophilic archaeonPyrococcus furiosus contains a four-Fe ferredoxin (Pf- Fd) that differs from most other 4Fe-Fd’s in that its [Fe4S4] cluster is anchored to protein by only three cysteinyl residues.Pf- Fd also is of interest because in its reduced form, [Fe4S4]+, the cluster exhibits bothS = 1/2 andS = 3/2 spin states. Addition of excess cyanide ion converts the cluster exclusively to anS = 1/2 state (g1 = 2.09, g2 = 1.95, g3 = 1.92), however dialysis restores the EPR signal of native reduced protein indicating that the cluster is not irreversibly altered by cyanide. Both the native protein and protein in the presence of excess cyanide ion (Pf- Fd 4Fe-CN) were investigated here using the techniques of electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopy. In particular,Pf- Fd 4Fe-CN was investigated using13CN? and C15N? ligands.13C and15N ENDOR indicated that a single cyanide ion bound directly, with the cluster showing an unusually small contact interaction (aiso(13C)~ ?3 MHz, aiso(15N) ~ 0). This is in contrast to cyanide bound to monomeric low-spin Fe(III)-containing proteins such as transferrin and myoglobin, for which the13C hyperfine coupling has a large isotropic component (aiso(13C) ≈ ?30 MHz). This small contact interaction is not due to low spin density of Fe, as57Fe ENDOR of the singly and triply labeledPf- Fd 4FeCN isotopologs, [57FeFe3S4]+ and [Fe57Fe3S4]+, show hyperfine coupling characteristic for [Fe4S4]+ clusters, particularly for the Fe to which cyanide binds. Thus, the low spin density on13C is not due to low spin density on the Fe ion to which it binds. Further theoretical work is needed to explain the contrast between the strong electronic effect of cyanide ion binding with the low spin density on the ligand. 相似文献
5.
6.
7.
8.
9.
Grosnick D Wright SC Bolton RD Cooper MD Frank JS Hallin AL Heusi PA Hoffman CM Hogan GE Mariam FG Matis HS Mischke RE Piilonen LE Sandberg VD Sanders GH Sennhauser U Werbeck R Williams RA Wilson SL Hofstadter R Hughes EB Ritter MW Highland VL McDonough J 《Physical review letters》1986,57(26):3241-3244
10.