全文获取类型
收费全文 | 177篇 |
免费 | 0篇 |
专业分类
化学 | 88篇 |
晶体学 | 1篇 |
力学 | 2篇 |
数学 | 18篇 |
物理学 | 68篇 |
出版年
2019年 | 1篇 |
2018年 | 1篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 2篇 |
2013年 | 5篇 |
2012年 | 7篇 |
2011年 | 9篇 |
2010年 | 7篇 |
2009年 | 1篇 |
2008年 | 9篇 |
2007年 | 13篇 |
2006年 | 6篇 |
2005年 | 4篇 |
2004年 | 6篇 |
2003年 | 5篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 8篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 1篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1971年 | 1篇 |
1966年 | 1篇 |
1959年 | 1篇 |
1958年 | 1篇 |
1948年 | 2篇 |
1939年 | 2篇 |
1925年 | 1篇 |
1874年 | 1篇 |
1873年 | 1篇 |
排序方式: 共有177条查询结果,搜索用时 206 毫秒
61.
Two-step one-pot reaction conditions have been developed for synthesizing 1-substituted-1,2,3-triazoles. This transformation involves the base-catalyzed deprotection of trimethylsilylacetylene followed by Cu-catalyzed Huisgen 1,3-dipolar cycloaddition under aqueous reaction conditions. Utilization of potassium carbonate as the base and methanol as the alcoholic aqueous co-solvent resulted in optimal yields of the desired products. The reaction conditions were found to be successful for both alkyl and aryl azide reactants, including analogs with electron-donating and electron-withdrawing functionality. This procedure stands as a simple and regioselective means by which to prepare 1-substituted-1,2,3-triazole compounds directly from azide precursors. 相似文献
62.
D. Walz J. -P. My G. Kamarinos 《Applied Physics A: Materials Science & Processing》1996,62(4):345-353
The recombination lifetime and diffusion length of intentionally iron-contaminated samples were measured by the Surface Photo Voltage (SPV) and the Elymat technique. The lifetime results from these techniques for intentionally iron-contaminated samples were analysed, in particular for the aspect of the injection-level dependency of recombination lifetime. Based on theoretical considerations, a method for the analysis of deep-level parameters combining constant photon flux SPV and Elymat measurements has been developed. This method is based on a detailed numerical analysis of the Elymat technique, including the Dember electric field, the characteristics of the laser beam, the transport parameters of the semiconductor and multilevel Shockley-Read-Hall (SRH) recombination kinetics. The results of the numerical simulation are applied to the analysis of recombination lifetime measurements on intentionally iron-contaminated samples. We compared numerical simulations and experimental results from SPV and Elymat for p-type samples using the classical acceptor level atE
v +0.1 eV and the donor level of FeB pairs atE
c -0.3 eV as recombination centre. Better consistency in the interpretation of the results has been found in the doping range 1014–1016 cm–3 supposing theE
c -0.3 eV level as predominant recombination centre. An attempt to extract the electron and hole capture cross-sections for this defect is made. 相似文献
63.
64.
65.
Kretschmann A Walz MM Flechtner K Steinrück HP Gottfried JM 《Chemical communications (Cambridge, England)》2007,(6):568-570
We demonstrate that adsorbed meso-tetraphenylporphyrin molecules can coordinate Zn atoms that are pre-deposited on an Ag(111) surface, forming a complex that is identical to directly deposited tetraphenylporphyrinato-zinc(II); this reaction, which we studied with XPS, is the first example of an oxidative dissolution of a metal by a large organic ligand under ultrahigh vacuum conditions. 相似文献
66.
The syntheses of catechol-containing mycobactin S and T analogs are described. These analogs incorporate a catechol-glycine moiety in place of the phenol-oxazoline of the naturally occurring mycobactins S and T. Studies indicated that the new siderophore analogs bind iron, and promote the growth of a number of microbes, especially strains of mycobacteria, as expected. 相似文献
67.
Gorham PW Barwick SW Beatty JJ Besson DZ Binns WR Chen C Chen P Clem JM Connolly A Dowkontt PF DuVernois MA Field RC Goldstein D Goodhue A Hast C Hebert CL Hoover S Israel MH Kowalski J Learned JG Liewer KM Link JT Lusczek E Matsuno S Mercurio B Miki C Miocinović P Nam J Naudet CJ Ng J Nichol R Palladino K Reil K Romero-Wolf A Rosen M Ruckman L Saltzberg D Seckel D Varner GS Walz D Wu F;ANITA Collaboration 《Physical review letters》2007,99(17):171101
We report on observations of coherent, impulsive radio Cherenkov radiation from electromagnetic showers in solid ice. This is the first observation of the Askaryan effect in ice. As part of the complete validation process for the ANITA experiment, we performed an experiment at the Stanford Linear Accelerator Center in June 2006 using a 7.5 metric ton ice target. We measure for the first time the large-scale angular dependence of the radiation pattern, a major factor in determining the solid-angle acceptance of ultrahigh-energy neutrino detectors. 相似文献
68.
Walz MM Vollnhals F Schirmer M Steinrück HP Marbach H 《Physical chemistry chemical physics : PCCP》2011,13(38):17333-17338
Upon exposure to Fe(CO)(5), the formation of pure cubic Fe nanocrystals with dimensions up to ~75 nm is reported on ultra-thin SiO(x) films (thickness ≈ 0.5 nm) on Si(001), which have been prepared in situ under UHV conditions. The active centers for initial decomposition of Fe(CO)(5) resulting in the growth of the Fe clusters are proposed to be SiO sites. After nucleation at these sites, further crystal growth is observed due to autocatalytic dissociation of Fe(CO)(5) at room temperature. The density of the Fe clusters can be increased by irradiating the surface with a focused electron beam (15 keV) prior to gas exposure. The formation of the active SiO sites upon electron irradiation is attributed to oxygen desorption via the Knotek-Feibelman mechanism. 相似文献
69.
Vittadini A Schirmer M Walz MM Vollnhals F Lukasczyk T Steinrück HP Marbach H Riss A Elser MJ Schürer B Diwald O 《Langmuir : the ACS journal of surfaces and colloids》2012,28(20):7851-7858
The identification of defects and their controlled generation in titanate nanostructures is a key to their successful application in photoelectronic devices. We comprehensively explored the effect of vacuum annealing on morphology and composition of Na(2)Ti(3)O(7) nanowires and protonated H(2)Ti(3)O(7) nanoscrolls using a combination of scanning electron microscopy, Auger and Fourier-transform infrared (FT-IR) spectroscopy, as well as ab initio density functional theory (DFT) calculations. The observation that H(2)Ti(3)O(7) nanoscrolls are more susceptible to electronic reduction and annealing-induced n-type doping than Na(2)Ti(3)O(7) nanowires is attributed to the position of the conduction band minimum. It is close to the vacuum level and, thus, favors the Fermi level-induced compensation of donor states by cation vacancies. In agreement with theoretical predictions that suggest similar formation energies for oxygen and sodium vacancies, we experimentally observed the annealing induced depletion of sodium from the surface of the nanowires. 相似文献
70.
C. C. Rodegheri K. Blaum H. Kracke S. Kreim A. Mooser C. Mrozik W. Quint S. Ulmer J. Walz 《Hyperfine Interactions》2009,194(1-3):93-98
The measurement and comparison of the magnetic moment (or g-factor) of the proton and antiproton provide a stringent experimental test of the CPT-theorem in the baryonic sector (Quint et al., Nucl Instrum Methods Phys Res, B 214:207, 2004). We present an experimental setup for the first direct high-precision measurement of the g-factor of a single isolated proton in a double cylindrical Penning trap. The application of the continuous Stern-Gerlach effect to detect quantum jumps between the two spin states of the particle, together with a novel trap design specially developed for this purpose, offers the possibility of measuring the magnetic moment not only of a single proton but also of a single antiproton. It is aimed to achieve a relative uncertainty of 10???9 or better. Preliminary results including mass spectra of particle clouds as well as single proton preparation and detection are shown. 相似文献