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61.
T Zidki L Zhang V Shafirovich SV Lymar 《Journal of the American Chemical Society》2012,134(35):14275-14278
A novel, highly efficient, and stable water oxidation catalyst was prepared by a pH-controlled adsorption of Co(II) on ~10 nm diameter silica nanoparticles. A lower limit of ~300 s(-1) per cobalt atom for the catalyst turnover frequency in oxygen evolution was estimated, which attests to a very high catalytic activity. Electron microscopy revealed that cobalt is adsorbed on the SiO(2) nanoparticle surfaces as small (1-2 nm) clusters of Co(OH)(2). This catalyst is optically transparent over the entire UV-vis range and is thus suitable for mechanistic investigations by time-resolved spectroscopic techniques. 相似文献
62.
Irina Perdivara Leesa J. Deterding Michael Przybylski Kenneth B. Tomer 《Journal of the American Society for Mass Spectrometry》2010,21(7):1114-1117
Oxidative modification of tryptophan to kynurenine (KYN) and N-formyl kynurenine (NFK) has been described in mitochondrial
proteins associated with redox metabolism, and in human cataract lenses. To a large extent, however, previously reported identifications
of these modifications were performed using peptide mass fingerprinting and/or tandem-MS data of proteins separated by gel
electrophoresis. To date, it is uncertain whether NFK and KYN may represent sample handling artifacts or exclusively post-translational
events. To address the problem of the origin of tryptophan oxidation, we characterized several antibodies by liquid chromatography-tandem
mass spectrometry, with and without the use of electrophoretic separation of heavy and light chains. Antibodies are not normally
expected to undergo oxidative modifications, however, several tryptophan (Trp) residues on both heavy and light chains were
found extensively modified to both doubly oxidized Trp and KYN following SDS-PAGE separation and in-gel digestion. In contrast,
those residues were observed as non-modified upon in-solution digestion. These results indicate that Trp oxidation may occur
as an artifact in proteins separated by SDS-PAGE, and their presence should be carefully interpreted, especially when gel
electrophoretic separation methods are employed. 相似文献
63.
Christine Hager-Braun Elisabeth O. Hochleitner Miroslaw K. Gorny Susan Zolla-Pazner Rachelle J. Bienstock Kenneth B. Tomer 《Journal of the American Society for Mass Spectrometry》2010,21(10):1687-1698
A subset of the neutralizing anti-HIV antibodies recognize epitopes on the envelope protein gp120 of the human immunodeficiency
virus. These epitopes are exposed during conformational changes when gp120 binds to its primary receptor CD4. Based on chemical
modification of lysine and arginine residues followed by mass spectrometric analysis, we determined the epitope on gp120 recognized
by the human monoclonal antibody 559/64-D, which was previously found to be specific for the CD4 binding domain. Twenty-four
lysine and arginine residues in recombinant full-length glycosylated gp120 were characterized; the relative reactivities of
two lysine residues and five arginine residues were affected by the binding of 559/64-D. The data show that the epitope is
discontinuous and is located in the proximity of the CD4-binding site. Additionally, the reactivities of a residue that is
located in the secondary receptor binding region and several residues distant from the CD4 binding site were also altered
by Ab binding. These data suggest that binding of 559/64-D induced conformational changes which result in altered surface
exposure of specific amino acids distant from the CD4-binding site. Consequently, binding of 559/64-D to gp120 affects not
only the CD4-binding site, which is recognized as the epitope, but appears to have a global effect on surface exposed residues
of the full-length glycosylated gp120. 相似文献
64.
The Entropy/Influence conjecture, raised by Friedgut and Kalai (1996) [9], seeks to relate two different measures of concentration of the Fourier coefficients of a Boolean function. Roughly saying, it claims that if the Fourier spectrum is “smeared out”, then the Fourier coefficients are concentrated on “high” levels. In this note we generalize the conjecture to biased product measures on the discrete cube. 相似文献
65.
66.
Kenneth B. Tomer 《Journal of the American Society for Mass Spectrometry》2002,13(1):107-108
67.
Active control of sound can be employed globally to reduce noise levels in an entire enclosure, or locally around a listener's head. Recently, spherical loudspeaker arrays have been studied as multiple-channel sources for local active control of sound, presenting the fundamental theory and several active control configurations. In this paper, important aspects of using a spherical loudspeaker array for local active control of sound are further investigated. First, the feasibility of creating sphere-shaped quiet zones away from the source is studied both theoretically and numerically, showing that these quiet zones are associated with sound amplification and poor system robustness. To mitigate the latter, the design of shell-shaped quiet zones around the source is investigated. A combination of two spherical sources is then studied with the aim of enlarging the quiet zone. The two sources are employed to generate quiet zones that surround a rigid sphere, investigating the application of active control around a listener's head. A significant improvement in performance is demonstrated in this case over a conventional headrest-type system that uses two monopole secondary sources. Finally, several simulations are presented to support the theoretical work and to demonstrate the performance and limitations of the system. 相似文献
68.
69.
Thirumal Yempala Tomer Babu Subhendu Karmakar Alina Nemirovski Maisaloon Ishan Valentina Gandin Dan Gibson 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(50):18386-18391
Most multi‐action PtIV prodrugs have bioactive ligands containing carboxylates. This is probably due to the ease of carboxylating the OH axial ligands and because following reduction, the active drug is released. A major challenge is to expand the arsenal of bioactive ligands to include those without carboxylates. We describe a general approach for synthesis of PtIV prodrugs that release drugs with OH groups. We linked the OH groups of gemcitabine (Gem), paclitaxel (Tax), and estramustine (EM) to the PtIV derivative of cisplatin by a carbonate bridge. Following reduction, the axial ligands lost CO2, rapidly generating the active drugs. In contrast, succinate‐linked drugs did not readily release the free drugs. The carbonate‐bridged ctc‐[Pt(NH3)2(PhB)(Gem‐Carb)Cl2] was significantly more cytotoxic than the succinate‐bridged ctc‐[Pt(NH3)2(PhB)(Gem‐Suc)Cl2], and more potent and less toxic than gemcitabine, cisplatin, and co‐administration of cisplatin and gemcitabine. 相似文献
70.
Acharya Balkrishna Meenu Tomer Monali Joshi Seema Gujral Rajesh Kumar Mishra Jyotish Srivastava Anurag Varshney 《Journal of separation science》2022,45(10):1616-1635
Mahayograj Guggul is an ancient ayurvedic medicine, prescribed for various joint disorders like arthritis, gout, and rheumatism. The present research was envisaged to develop a simple, sensitive, and comprehensive analytical method for standardization of Mahayograj Guggul. The analysis was conducted for gallic acid, protocatechuic acid, vanillic acid, cinnamic acid, piperine, guggulsterone-E, and guggulsterone-Z by high-performance thin-layer chromatography, and additionally ferulic acid, ellagic acid, and picroside I by ultra high-performance liquid chromatography. These developed methods were validated as per international guidelines, and were found linear (r2 > 0.99), sensitive, precise (relative standard deviation < 5%), and accurate with recovery values (85–105%). The limit of detection and quantification were in the range of 0.11–23.6 and 0.33–71.51 μg/g. Gas chromatography tandem mass spectrometry was used to develop Mahayograj Guggul fingerprinting profile and to identify mid-polar or nonpolar compounds. Proximate analysis was used to ascertain the functional groups present in Mahayograj Guggul. Ultra high-performance liquid chromatography and gas chromatography tandem mass spectrometry were further employed to authenticate quality reproducibility in the active ingredients of Mahayograj Guggul in six commercial batches. Taken together, these analytical methods provide a scientific basis and reference for quality control evaluation of Mahayograj Guggul and similar traditional broad-spectrum formulations. 相似文献