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排序方式: 共有61条查询结果,搜索用时 15 毫秒
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Qu J Fredericks PM 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2000,56(8):1637-1644
Surface-enhanced Raman scattering (SERS) spectra, taken with 632.8 nm excitation are reported for the water-soluble tetrakis(3-N-methylpyridyl)porphyrin chloride (TMPyP(3)), tetrakis(4-N-methylpyridyl)porphyrin chloride (TMPyP(4)) and Sn(IV)tetrakis(4-N-methylpyridyl)porphyrin chloride (Sn(IV)TMPyP(4)) using an electrochemically prepared Ag surface with an area ca. 12.56 mm2. It was found that the spectra vary as increasing amounts of the compounds are placed on the surface, with surface concentrations in the approximate range 1000-5 pmol/12.56 mm2. We suggest that the reasons for the changes be that the reaction means between porphyrin molecules and Ag surface is different and the porphyrin macrocyclic molecules adopt different orientation as the surface concentrations decrease. 相似文献
35.
Cletus B Olds W Izake EL Sundarajoo S Fredericks PM Jaatinen E 《Analytical and bioanalytical chemistry》2012,403(1):255-263
A time-resolved inverse spatially offset Raman spectrometer was constructed for depth profiling of Raman-active substances
under both the lab and the field environments. The system operating principles and performance are discussed along with its
advantages relative to traditional continuous wave spatially offset Raman spectrometer. The developed spectrometer uses a
combination of space- and time-resolved detection in order to obtain high-quality Raman spectra from substances hidden behind
coloured opaque surface layers, such as plastic and garments, with a single measurement. The time-gated spatially offset Raman
spectrometer was successfully used to detect concealed explosives and drug precursors under incandescent and fluorescent background
light as well as under daylight. The average screening time was 50 s per measurement. The excitation energy requirements were
relatively low (20 mW) which makes the probe safe for screening hazardous substances. The unit has been designed with nanosecond
laser excitation and gated detection, making it of lower cost and complexity than previous picosecond-based systems, to provide
a functional platform for in-line or in-field sensing of chemical substances. 相似文献
36.
This study describes the screening of a peptide phage display library for amino acid sequences that bind with different affinities to a novel class of chelating ligands complexed with Ni2+ ions. These chelating ligands are based on the 1,4,7-triazacyclononane (TACN) structure and have been chosen to allow enhanced efficiency in protein capture and decreased propensity for metal ion leakage in the immobilized metal ion affinity chromatographic (IMAC) purification of recombinant proteins. Utilising high stringency screening conditions, various peptide sequences containing multiple histidine, tryptophan, and/or tyrosine residues were identified amongst the different phage peptide sequences isolated. The structures, and particularly the conserved locations of these key amino acid residues within the selected heptapeptides, form a basis to design specific peptide tags for use with these novel TACN ligands as a new mode of IMAC purification of recombinant proteins. 相似文献
37.
S. W. Shalaby Eli M. Pearce Robert J. Fredericks E. A. Turi 《Journal of Polymer Science.Polymer Physics》1973,11(1):1-14
A homologous series of aliphatic polyoxamides, nylon 122, 102, 82, and 62, were prepared by the bulk polycondensation of dialkyl oxalates with diamines. Infrared spectroscopy, x-ray diffraction, differential thermal analysis, thermogravimetric analysis, and gas chromatography were used to study the structure and thermal stability of these polyoxamides. From the fiber pattern of nylon 122, a structural repeat distance of 19.5 Å was measured. This was in close agreement with the expected value for an extended planar, zigzag chain conformation. With the exception of the expected decrease in the structural repeat distance along the chain axis resulting from the different number of methylene groups, nylons 122, 102, and 82 were isostructural. Nylon 62 appeared to pack in a similar manner to the other materials studied. However, there were differences in the diffraction pattern of this polymer; these may be indicative of a different chain conformation or of strain in the crystalline regions of the polymer. The infrared spectra indicate the presence of strong hydrogen bonding in all the polymers. Thermal analysis and pyrolysis data revealed catastrophic polymer degradation between 400 and 500°C in nitrogen, with appreciable homolytic cleavage of the oxamide group. 相似文献
38.
S. W. Shalaby Robert J. Fredericks Eli M. Pearce 《Journal of Polymer Science.Polymer Physics》1972,10(9):1699-1707
Fully methylated nylon 12 was prepared by the hydrolytic polymerization of N-methyllaurolactam. The polymer, with about 20% crystallinity, has a crystal structure different from that of nylon 12. The X-ray diffraction patterns of copolymers of N-methyllaurolactam and laurolactam were shown to be composition-dependent. Copolymers containing up to 15% laurolactam units exhibited a crystal structure essentially the same as poly-N-methyllaurolactam. Copolymers containing from 20 to 50% laurolactam are transition structures, whereas copolymers containing more than 50% laurolactam units exhibit a crystal structure characteristic of polylaurolactam. DSC data on the homopolymers and copolymers are also reported. 相似文献
39.
Tony J Aitchison Milena Ginic‐Markovic Martin Saunders Peter Fredericks Suresh Valiyaveettil Janis G. Matisons George P. Simon 《Journal of polymer science. Part A, Polymer chemistry》2011,49(19):4283-4291
The synthesis and characterization of multiwalled carbon nanotube (MWCNT) polymer brushes produced by activators regenerated by electron transfer (ARGET) in atom‐transfer radical polymerization (ATRP) was discussed. The polymer brushes were synthesized by esterification of the MWCNT carboxylic acid groups with hydroxyethyl‐2‐bromoisobutyrate and subsequently used in ARGET ATRP. This created a well defined living polymer brush carbon nanotube of comparatively low polydispersity and a polymer layer 10 nm thick. As, ARGET ATRP uses only minute concentrations of copper (II) catalyst, and is less sensitive to air compared to other living polymerization techniques, this process is a more industry‐compatible route for the commercialization of such materials. The structural and chemical properties were explored by a range of techniques including high resolution transmission electron microscopy, gel permeation chromatography, elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. In addition, the polymer brush nanotubes were explored for their potential use in films and as fillers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
40.
Shankaran Sundarajoo Emad L. Izake William Olds Biju Cletus Esa Jaatinen Peter M. Fredericks 《Journal of Raman spectroscopy : JRS》2013,44(7):949-956
Time‐resolved Raman spectroscopy, spatially offset Raman spectroscopy and time‐resolved spatially offset Raman spectroscopy (TR‐SORS) have proven their capability for the non‐invasive profiling of deep layers of a sample. Recent studies have indicated that TR‐SORS exhibits an enhanced selectivity toward the deep layers of a sample. However, the enhanced depth profiling efficiency of TR‐SORS, in comparison with time‐resolved Raman spectroscopy and spatially offset Raman spectroscopy, is yet to be assessed and explained in accordance to the synergistic effects of spatial and temporal resolutions. This study provides a critical investigation of the depth profiling efficiency of the three deep Raman techniques. The study compares the efficiency of the various deep Raman spectroscopy techniques for the stand‐off detection of explosive precursors hidden in highly fluorescing packaging. The study explains for the first time the synergistic effects of spatial and temporal resolutions in the deep Raman techniques and their impact on the acquired spectral data. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献