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11.
J. D. Botha 《Linear and Multilinear Algebra》1996,40(4):365-371
Necessary and sufficient conditions are presented for a square matrix over an arbitrary field to be a product of k ≥ 1 idempotent matrices of prescribed nullities. 相似文献
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N. Eassa R. Betz E. Coetsee H.C. Swart A. Venter J.R. Botha 《Current Applied Physics》2013,13(2):366-370
X-ray photoelectron spectroscopy, field emission scanning electron microscopy, Raman and photoluminescence spectroscopy were used to evaluate the surface properties of n-type InAs (111)A etched in a 1% Br–methanol solution. Etching completely removes the native oxides from the surface and enhances the photoluminescence response. The adsorption of bromine onto the InAs surface leads to the formation of In–Brx and As–Brx bonds (x = 1, 2, 3) as inferred from changes in the In 3d3/2;5/2 and As 3d core level binding energies. The etch rate is found to decrease due to strong anisotropic effects and the high volatility of the bromine species. A 1 min Br–methanol etch was found to enhance the photoluminescence intensity by a factor of 3, probably due to a reduction in the surface state density upon de-oxidation of the surface. This is thought to be due to reductions in the surface state density. The presence of native oxides enhances both the surface accumulation layer and the surface state density. 相似文献
14.
Giant Hysteretic Sorption of CO2: In Situ Crystallographic Visualization of Guest Binding within a Breathing Framework at 298 K 下载免费PDF全文
Dr. Prem Lama Dr. Himanshu Aggarwal Charl X. Bezuidenhout Prof. Leonard J. Barbour 《Angewandte Chemie (International ed. in English)》2016,55(42):13271-13275
A dynamic ZnII‐MOF has been shown to exhibit extreme breathing behavior under gas pressure. The very narrow pore form of the activated framework opens up in the presence of carbon dioxide, thus making it a suitable material for CO2 capture. Sorption of CO2 at 298 K and relatively high pressure clearly shows a two‐step isotherm with giant hysteresis for the second step. In‐situ single‐crystal diffraction analysis was carried out under CO2 gas pressure at 298 K using an environmental gas cell in order to visualize the interaction between CO2 and the host framework. The results are well supported by pressure‐gradient differential scanning calorimetry (P‐DSC) and variable‐pressure powder X‐ray analysis. Theoretical calculations have been carried out in order to further back up the crystallographic data. 相似文献
15.
Guenu S Heng AE Charbonné F Galmier MJ Charlès F Deteix P Souweine B Lartigue C 《Rapid communications in mass spectrometry : RCM》2007,21(2):229-236
Anti-infectious lock is an emerging therapeutic option for preventing and/or controlling catheter-associated infection. Ethanol has widespread bactericidal activity, limited side effects, and low risk of inducing antimicrobial resistance. However, concerns have been raised about ethanol-induced catheter structural degradation. In this study, silicone catheters were immersed at 37 degrees C in three different solvents: 0.9% sodium chloride, 60% ethanol, and 95% ethanol for 4 h, 15 days and 15 days after a first storage of 4 h. Scanning electron microscopy (magnification 1000-20 000 times) of the inner surface of the catheter revealed no damage to the lumen surfaces of catheters immersed in 95% ethanol for 15 days compared with the reference catheter. Gas chromatography/mass spectrometry (GC/MS) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) analysis of the storage solutions revealed a significant release of polydimethylsiloxanes having a number of dimethylsiloxane units lower than 30 in the 95% ethanol solution and a structure highly consistent with a cyclic structure. Most release occurred within the first 4 h of exposure. In contrast, there was no difference in the small amounts of silicone released in 0.9% sodium chloride as reference and 60% ethanol solution, whatever the exposure time. These results should allow the development of clinical trials to assess the efficacy of the 60% ethanol lock technique in preventing or controlling the infectious complications of silicone dialysis catheters. 相似文献
16.
Ni was resistively deposited onto bulk InAs and subsequently oxidized in an O2 atmosphere. The anneal temperature and time were 450 °C and 2.5 h, respectively. X-ray diffraction of the oxidized Ni/InAs sample revealed the formation of In3Ni2 and In2O3 on the front suggesting inter diffusion of In, Ni and O. NiO was not detected by X-ray diffraction. In a preliminary study, using glass as a substrate, NiO readily formed when using these oxidation parameters. Conductivity measurements of the oxidized Ni/InAs surface revealed a conducting front and insulating rear surface while TEM of the Ni/InAs interface revealed an intermediate amorphous diffusion zone between the “oxidized” Ni layer and the bulk InAs. A closer investigation of the intermediate layer supports the X-ray diffraction results, suggesting compound formation due to diffusion of oxygen and nickel into the substrate, and out-diffusion of In and As from the bulk of the sample. AES was used to further elucidate these results. 相似文献
17.
H.A.A. Seed Ahmed O.M. Ntwaeaborwa M.A. Gusowski J.R. Botha R.E. Kroon 《Physica B: Condensed Matter》2012,407(10):1653-1655
Amorphous silica samples doped with 0.1 and 1 mol% of terbium (Tb) were synthesized by the sol–gel method. In addition to the green light associated with 5D4→7FJ transitions of Tb3+, the sample containing 0.1 mol% also emitted blue light as a result of 5D3→7FJ transitions during photoluminescence (PL) measurements. As a result of concentration quenching this blue emission was not observed for the samples doped with the higher concentration (1 mol%). However the blue 5D3 →7FJ emission was observed in the 1 mol% doped samples during cathodoluminescence (CL) measurements. Since a rough calculation indicated that the excitation rate in the CL system where the blue emission is observed may be similar to a laser PL system under conditions where the blue emission is not observed, the difference is attributed to the nature of the excitation sources. It is suggested that during the CL excitation incident electrons can reduce non-luminescent Tb4+ ions in the silica, substituting for Si4+ ions, to the excited (Tb3+)? state and that these are responsible for the blue emission, which does not occur during PL excitation. 相似文献
18.
M.A. Lephoto O.M. Ntwaeaborwa Shreyas S. Pitale H.C. Swart J.R. Botha B.M. Mothudi 《Physica B: Condensed Matter》2012,407(10):1603-1606
Combustion method was used in this study to prepare BaAl2O4:Eu2+ phosphors co-doped with different trivalent rare-earths (Re3+=Dy3+, Nd3+, Gd3+, Sm3+, Ce3+, Er3+, Pr3+ and Tb3+) ions at an initiating temperature of 600 °C. The phosphors were annealed at 1000 °C for 3 h. As confirmed from the X-ray diffraction (XRD) data, both as prepared and post annealed samples crystallized in the well known hexagonal structure of BaAl2O4. All samples exhibited bluish-green emission associated with the 4f65d1→4f7 transitions of Eu2+ at ∼500 nm. Although the highest intensity was observed from Er3+ co-doping, the longest afterglow (due to trapping and detrapping of charge carriers) was observed from Nd3+ followed by Dy3+ co-doping. The traps responsible for the long afterglow were studied using thermoluminescence (TL) spectroscopy. 相似文献
19.
Peter James Carrington Abu Syed Mahajumi Magnus C. Wagener Johannes Reinhardt Botha Qian Zhuang Anthony Krier 《Physica B: Condensed Matter》2012,407(10):1493-1496
We report on the fabrication of GaAs based p–i–n solar cells containing 5 and 10 layers of type II GaSb quantum rings grown by molecular beam epitaxy. Solar cells containing quantum rings show improved efficiency at longer wavelengths into the near-IR extending up to 1500 nm and show enhanced short-circuit current under 1 sun illumination compared to a GaAs control cell. A reduction in the open-circuit voltage is observed due to the build-up of internal strain. The MBE growth, formation and photoluminescence of single and stacked layers of GaSb/GaAs quantum rings are also presented. 相似文献
20.
D.M. Murape N. Eassa C. Nyamhere J.H. Neethling R. Betz E. Coetsee H.C. Swart J.R. Botha A. Venter 《Physica B: Condensed Matter》2012,407(10):1675-1678
Bulk (1 0 0) n-GaSb surfaces have been treated with a sulphur based solution ((NH4)2S/(NH4)2SO4) to which sulphur has been added, not previously reported for the passivation of GaSb surfaces. Au/n-GaSb Schottky barrier diodes (SBDs) fabricated on the treated material show significant improvement compared to that of the similar SBDs on the as-received material as evidenced by the lower ideality factor (n), higher barrier height (?b) and lower contact resistance obtained. Additionally, the reverse leakage current, although not saturating, has been reduced by almost an order of magnitude at −0.2 V. The sample surfaces were studied by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The native oxide, Sb–O, present on the as-received material is effectively removed on treating with ([(NH4)2S/(NH4)2SO4]+S) and (NH4)2S. Analysis of the as-received surface by XPS, prior to and after argon sputtering, suggests that the native oxide layer is ≤8.5 nm. 相似文献