全文获取类型
收费全文 | 243篇 |
免费 | 3篇 |
专业分类
化学 | 139篇 |
晶体学 | 2篇 |
力学 | 7篇 |
数学 | 31篇 |
物理学 | 67篇 |
出版年
2019年 | 2篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2015年 | 3篇 |
2013年 | 7篇 |
2012年 | 9篇 |
2011年 | 12篇 |
2010年 | 8篇 |
2009年 | 7篇 |
2008年 | 10篇 |
2007年 | 12篇 |
2006年 | 9篇 |
2005年 | 13篇 |
2004年 | 16篇 |
2003年 | 15篇 |
2002年 | 8篇 |
2001年 | 8篇 |
2000年 | 6篇 |
1999年 | 7篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1985年 | 1篇 |
1984年 | 5篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1974年 | 1篇 |
1973年 | 4篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 3篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1935年 | 2篇 |
1934年 | 1篇 |
1932年 | 1篇 |
1929年 | 1篇 |
排序方式: 共有246条查询结果,搜索用时 15 毫秒
51.
Carmen Molina-París Paul R. Anderson Stephen A. Ramsey 《International Journal of Theoretical Physics》2001,40(12):2231-2258
The renormalization of a scalar field theory with a quartic self-coupling via adiabatic regularization in a Robertson-Walker spacetime is discussed. The adiabatic counterterms are presented in a way that is most conducive to numerical computations. A variation of the adiabatic regularization method is presented which leads to analytic approximations for the energy–momentum tensor of the quantum field and the quantum contribution to the effective mass of the mean field. Conservation of the energy–momentum tensor for the field is discussed and it is shown that the part of the energy–momentum tensor which depends only on the mean field is not conserved but the full renormalized energy–momentum tensor is conserved, as expected and required by the semiclassical Einstein's equation. It is also shown that if the analytic approximations are used the resulting approximate energy–momentum tensor is conserved. This allows a self-consistent backreaction calculation to be performed using the analytic approximations. The usefulness of the approximations is discussed. 相似文献
52.
Robert I. R. Blyth Renate Duschek Georg Koller Falko P. Netzer Michael G. Ramsey 《Monatshefte für Chemie / Chemical Monthly》2001,11(3):509-518
We highlight the importance of interfacial properties in determining the performance of devices based on electroactive organic materials. Investigations of the interfaces of benzene with Al(111) and In2O3 are presented as a model of interface properties for devices based on complex aromatic molecules. At both interfaces the binding is shown to be electrostatic, with the resulting interface dipole determining the band alignment. It is also argued that chemical modification of substrates can be used to tailor both electronic and structural properties. 相似文献
53.
54.
55.
Stephen Berkebile Georg Koller Gregor Hlawacek Christian Teichert Falko P. Netzer Michael G. Ramsey 《Surface science》2006,600(24):L313-L317
The molecular/crystal orientation and morphology of active molecular structures is a key determinant for the function of nanoscaled organic devices, yet little is known regarding the processes that govern thin film growth. Here, we show that either sticking or diffusion anisotropy can control the growth depending on preparation conditions. This is illustrated by an investigation into the growth of sexiphenyl (6P) on the anisotropic TiO2(1 1 0)-(1 × 1) single crystal surface. The great differences in crystallite orientation and morphology observed are explained by the domination of the growth kinetics by either sticking or diffusion anisotropy depending on growth temperature. 相似文献
56.
N. F. Ramsey 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1988,10(2-3):121-125
It is an honor to contribute to this celebration of the hundredth anniversary of the birth of Otto Stern, who developed molecular beams to become one of the most nowerful and fruitful physics research methods. 相似文献
57.
L. A. Ramsey A. Patersom P. M. A. Broda J. D. Pownall I. J. F. Poplett 《Applied biochemistry and biotechnology》1984,9(4):409-410
Grass lignins are formed by the polymerization of phenoxy radicals and contain a variety of carbon-carbon and carbon-oxygen
bonds. They are similar to the hardwood lignins, but differ by containing a substantial proportion of esterified cinnamic
acids.
Detailed nuclear magnetic resonance studies in conjunction with chemical analysis have given new information on the structure
of grass lignins.
Milled straw lignins (MSL) from barley were examined by both solution and solid-state (CP/MAS) NMR before and after acetylation.
The assignment of the carbon-13 (100 MHz) solution spectra was achieved using model compound data, nuclear Overhauser enhancement
(NOE) suppression, and insensitive nuclei enhanced by polarization transfer (INEPT) techniques. The NOE suppression permitted
quantitative analysis of lignin, giving information on the ratio of specific carbon atoms. Use of the relaxation agent, chromium
acetylacetonate, enabled accumulation of sufficient spectral data to give a spectrum suitable for integration after 90 h.
The INEPT technique, which had not previously been used for lignin analysis, was successfully applied to acetylated MSL. This
technique increased signal intensities 3–4-fold and simplified the spectrum by inverting methylene carbons and eliminating
or inverting quaternary carbons. Comparison of this spectrum with the normal spectrum permitted accurate assignment of quaternary
and methine carbons.
The solid-state carbon-13 CP/MAS NMR was used to examinein situ lignin and the isolated MSL. The13C-CP/MAS spectrum ofin situ lignin shows that cellulose and hemicellulose resonances dominate with little evidence ot the aromatic structure of lignin.
the13C-CP/MAS of MSL shows reduced carbohydrate resonances and increased aromatic resonances. The extent of modification to the
barley straw was estimated and results indicate the presence oflignin-carbohydrate complexes.
Detailed information on the nature of the linkages between lignin components and between lignin and carbohydrate components
has been obtained from these spectra. 相似文献
58.
J. Schoiswohl S. Eck M.G. Ramsey J.N. Andersen S. Surnev F.P. Netzer 《Surface science》2005,580(1-3):122-136
The adsorption of CO and the reaction of CO with pre-adsorbed oxygen at room temperature has been studied on the (2 × 1)ORh(1 1 1) surface and on vanadium oxideRh(1 1 1) “inverse model catalyst” surfaces using scanning tunnelling microscopy (STM) and core-level photoemission with synchrotron radiation. Two types of structurally well-defined model catalyst V3O9Rh(1 1 1) surfaces have been prepared, which consist of large (mean size of 50 nm, type I model catalyst) and small (mean size <15 nm, type II model catalyst) two-dimensional oxide islands and bare Rh areas in between; the latter are covered by chemisorbed oxygen. Adsorption of CO on the oxygen pre-covered (2 × 1)ORh(1 1 1) surface leads to fast CO uptake in on-top sites and to the removal of half (0.25 ML) of the initial oxygen coverage by an oxidation clean-off reaction and as a result to the formation of a coadsorbed (2 × 2)O + CO phase. Further removal of the adsorbed O with CO is kinetically hindered at room temperature. A similar kinetic behaviour has been found also for the CO adsorption and oxidation reaction on the type I “inverse model catalyst” surface. In contrast, on the type II inverse catalyst surface, containing small V-oxide islands, the rate of removal of the chemisorbed oxygen is significantly enhanced. In addition, a reduction of the V-oxide islands at their perimeter by CO has been observed, which is suggested to be the reason for the promotion of the CO oxidation reaction near the metal-oxide phase boundary. 相似文献
59.
60.