全文获取类型
收费全文 | 767篇 |
免费 | 8篇 |
国内免费 | 2篇 |
专业分类
化学 | 402篇 |
晶体学 | 1篇 |
力学 | 5篇 |
数学 | 61篇 |
物理学 | 308篇 |
出版年
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 3篇 |
2015年 | 7篇 |
2014年 | 9篇 |
2013年 | 20篇 |
2012年 | 22篇 |
2011年 | 37篇 |
2010年 | 15篇 |
2009年 | 17篇 |
2008年 | 39篇 |
2007年 | 19篇 |
2006年 | 26篇 |
2005年 | 29篇 |
2004年 | 23篇 |
2003年 | 17篇 |
2002年 | 10篇 |
2001年 | 22篇 |
2000年 | 20篇 |
1999年 | 11篇 |
1998年 | 10篇 |
1997年 | 9篇 |
1996年 | 18篇 |
1995年 | 17篇 |
1994年 | 16篇 |
1993年 | 31篇 |
1992年 | 27篇 |
1991年 | 12篇 |
1990年 | 16篇 |
1989年 | 11篇 |
1988年 | 12篇 |
1987年 | 13篇 |
1986年 | 14篇 |
1985年 | 21篇 |
1984年 | 9篇 |
1983年 | 11篇 |
1982年 | 15篇 |
1981年 | 8篇 |
1980年 | 13篇 |
1979年 | 19篇 |
1978年 | 6篇 |
1977年 | 19篇 |
1976年 | 16篇 |
1975年 | 12篇 |
1974年 | 7篇 |
1973年 | 13篇 |
1972年 | 4篇 |
1971年 | 4篇 |
1969年 | 7篇 |
1968年 | 4篇 |
排序方式: 共有777条查询结果,搜索用时 828 毫秒
91.
David M. Walba Charles A. Liberko Eva Korblova Matthew Farrow Thomas E. Furtak Bruce C. Chow Daniel K. Schwartz Adam S. Freeman Kenneth Douglas Scott D. Williams Arthur F. Klittnick Noel A. Clark 《Liquid crystals》2004,31(4):481-489
A simple procedure for the preparation of octadecylsiloxane self-assembled monolayers (SAMs) on float glass substrates is described. The method utilizes commercial octadecyltriethoxysilane, OTE: n-C18H37Si(OCH2CH3)3, as the SAM precursor, with deposition accomplished in toluene solution using n-butylamine as catalyst. This synthetic approach obviates the use of the problematic trichlorosilanes typically required for the preparation of high quality SAMs, and is characterized by a wide 'process window,' utilizing off-the-shelf reagents without special handling. 相似文献
92.
Summary High resolution electron micrographs are shown of samples of colloidal alpha iron. According to the conditions of manufacture
the samples occur as (1) large, well-formed dendrites, (2) shorter, more fragile dendrites, (3) serrated rods, (4) needles
and (5) cubic particulates. The central stem is a line-up of single cubic crystals. Representative dimensions are given for
the various measurable units. A fine laminar structure in the cubic particulates, and some of the side branches and main stems
is noted. The same laminar structure is observed in some of the background platelet material from the mother liquor. Stereoscopic
studies show that the dendrites are three dimensional with their branches and main stem not in the same plane. X-ray diffraction
detects alpha iron plus some form of Fe2O3 in most samples.
The U.S. Navy Department, Bureau of Aeronautics, Industrial Planning Division, is credited with the development and sponsoring of the process for producing these fine powdered irons under contract No a (S) 52–792 C and NO a (S) 54–5190.
Presented in part before the Conference and Exhibit on Magnetism and Magnetic Materials held at Pittsburgh, Pennsylvania, June 14, 15 and 16, 1955 and before the annual meeting of the Electron Microscope Society of America, held at State College, Pennsylvania, October 1955; abstract, J. App. Phys.26, 1391 (1955). 相似文献
Zusammenfassung Es werden elektronenmikroskopische Aufnahmen mit hohem Aufl?sungsverm?gen von kolloiden α-Eisenteilchen gezeigt. Entsprechend den Herstellungsbedingungen fallen die Teilchen als gro\e, gut ausgebildete Dendriten, als kürzere schw?chere Dendriten, als gezackte Stangen, als Nadeln und als kubische Partikeln an. Der zentrale Stamm ist eine lineare Anordnung aus einzelnen kubischen Kristallen. Repr?sentative Dimensionen sind für die verschiedenen me\baren Einheiten eingezeichnet. Eine fein laminierte Struktur der kubischen Teilchen und von einigen Seiten?sten und Hauptachsen ist zu erkennen. Dieselbe Laminarstruktur wird teilweise an dem pl?ttchenartigen Material, das als Untergrund aus der Mutterflüssigkeit dazwischen liegt, beobachtet. Stereoskopische Aufnahmen zeigen, da\ die Dendriten dreidimensional sind und da\ Seitenzweige und Hauptachsen nicht in der gleichen Ebene liegen. R?ntgeninterferenzen lassen aufα-Eisen, sowie eine Form von Fe2O3 in den meisten Proben schlie\en.
The U.S. Navy Department, Bureau of Aeronautics, Industrial Planning Division, is credited with the development and sponsoring of the process for producing these fine powdered irons under contract No a (S) 52–792 C and NO a (S) 54–5190.
Presented in part before the Conference and Exhibit on Magnetism and Magnetic Materials held at Pittsburgh, Pennsylvania, June 14, 15 and 16, 1955 and before the annual meeting of the Electron Microscope Society of America, held at State College, Pennsylvania, October 1955; abstract, J. App. Phys.26, 1391 (1955). 相似文献
93.
94.
Strong correlated resonances have been found in the inelastic and transfer channels of 12C + 14C at energies above the Coulomb barrier. It is argued that the system may be sufficiently transparent to the grazing partial waves to enable predicted resonant effects to be observed. 相似文献
95.
Results are presented of an extensive theoretical study of the origin of high field superconductivity and/or magnetism in a number of Chevrel phase ternary compounds, MMo6X8 (with M=Sn, Eu, Gd and X=S and/or Se) based on self-consistent linear muffin-tin orbital (LMTO) energy band calculations using the local density approach (Hedin et al. exchange correlation) for the paramagnetic structures and local spin density formalism (Gunnarsson and Lundqvist) for the ferromagnetic structures. All electrons and all 15 atoms/cell are included with the core electrons (including the 4f's) recalculated in each iteration in a fully relativistic representation and the conduction electrons treated semirelativistically (all relativistic terms except spin-orbit). Superconductivity is found to be due to the high Mo d-band density of states (DOS) at EF resulting from the unusual large charge transfer of Mo electrons to the chalcogen sites. There is also a large charge transfer from the metal site to the cluster (≈2 electrons in Sn and Eu) giving essentially no occupied conduction bands, for example, at the Eu site and a divalent ion isomer shift in very good agreement with the experiments of Dunlap et al. The conduction-electron DOS at the Eu site is found to be reduced by an order of magnitude from its metallic state value - in close agreement with their spin - lattice relaxation rate measurements. This low conduction-electron DOS yields very weak coupling of the 4f electrons to the conduction electrons and only a very weak Ruderman-Kittel-Kasuya-Yosida magnetic interaction showing why all the Chevrel rare-earth compounds - except Ce and Eu - are superconducting despite their having large local magnetic moments. The unusually high upper critical fields, Hc2, in these materials is found to be due to the unusully flat energy bands near FF. The ferromagnetic (spin polarized) results for the Eu- and Gd-compounds show a net small but positive magnetic moment on the metal site and a small but negative induced spin magnetic moment on the Mo site in the Eu compound. Fermi-contact contributions to the hyperfine field are calculated and found to be in good agreement with the Eu Mössbauer results and the negative NMR Knights shift results of Fradin et al. These results demonstrate theoretically for the first time the validity of the Fischer et al. and Fradin et al. conclusion that the Jaccarino-Peter mechanism is responsible for the large increase in the Hc2 when large concentrations of Eu magnetic impurities are substituted in SnMo6S8. Finally, calculated Stoner factors for the paramegnetic phase and spin magnetization densities for the ferromagnetic phase are used to discuss qualitatively the origin of the different behavior observed for GdMo6S8 and EuMo6S8. 相似文献
96.
Large maxima in the generalized susceptibility of χ(q) of TaC calculated from its APW band structure are found to correlate very well with observed soft phonon modes. Such maxima are not found for HfC where phonon anomalies are not observed. 相似文献
97.
J. Simpson M.A. Riley R.W. Laird D.J. Hartley F.G. Kondev J. Sweeney A.N. Wilson S.J. Gale M.A. Bentley A.M. Bruce R. Chapman R.M. Clark D.M. Cullen P. Fallon P.D. Forsyth S.J. Freeman P.M. Jones J.C. Lisle A.O. Macchiavelli J.F. Sharpey-Schafer A.G. Smith J.F. Smith D.M. Thompson 《The European Physical Journal A - Hadrons and Nuclei》1998,1(3):267-274
A series of new strongly coupled high-K, multi-quasiparticle structures have been observed in the light erbium transitional
nuclei, 159Er and 160Er. The interpretation of these bands is discussed within the framework of the cranked shell model. These sequences, when
taken together with the existing quasiparticle excitations, form a near complete set of low-lying, multi-quasiparticle structures
on which a coherent series of aligned angular momentum, band crossing and blocking arguments can be based. The measured B(M1)/B(E2)
ratios are compared with geometrical calculations to test the proposed configuration assignments.
Received: 19 November 1997 相似文献
98.
99.
M. H. Freeman 《Optics & Laser Technology》1975,7(6):266-270
Optical systems intended for visual use must be designed with reference to both optical technology and physiological optics. This paper describes specific work to relate these fields for the case of biocular magnifiers. 相似文献
100.