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41.
Loren G. Hepler 《Journal of solution chemistry》1987,16(12):1049-1049
42.
Loren D. Olson 《manuscripta mathematica》1974,14(2):195-205
Let E be an elliptic curve defined overQ. The group ofQ- rational points of finite order on E is a finite group T(E). In this article T(E) is computed for all elliptic curves defined overQ admitting complex multiplication. The only possible values for the order t of T(E) are 1, 2, 3, 4, or 6 in these cases. A standard form for an affine equation describing an elliptic curve with a given j-invariant is obtained. This is used to show that if j ≠ 0, 26 33, then the number ofQ- rational points of order 2 on E depends only on j. The results are summarized in the accompanying table. 相似文献
43.
NMR Spectroscopic Assignment of Backbone and Side‐Chain Protons in Fully Protonated Proteins: Microcrystals,Sedimented Assemblies,and Amyloid Fibrils 下载免费PDF全文
Dr. Jan Stanek Dr. Loren B. Andreas Dr. Kristaps Jaudzems Dr. Diane Cala Dr. Daniela Lalli Andrea Bertarello Dr. Tobias Schubeis Dr. Inara Akopjana Dr. Svetlana Kotelovica Prof. Kaspars Tars Dr. Andrea Pica Dr. Serena Leone Prof. Delia Picone Dr. Zhi‐Qiang Xu Prof. Nicholas E. Dixon Dr. Denis Martinez Mélanie Berbon Nadia El Mammeri Dr. Abdelmajid Noubhani Dr. Sven Saupe Dr. Birgit Habenstein Dr. Antoine Loquet Dr. Guido Pintacuda 《Angewandte Chemie (International ed. in English)》2016,55(50):15504-15509
We demonstrate sensitive detection of alpha protons of fully protonated proteins by solid‐state NMR spectroscopy with 100–111 kHz magic‐angle spinning (MAS). The excellent resolution in the Cα‐Hα plane is demonstrated for 5 proteins, including microcrystals, a sedimented complex, a capsid and amyloid fibrils. A set of 3D spectra based on a Cα–Hα detection block was developed and applied for the sequence‐specific backbone and aliphatic side‐chain resonance assignment using only 500 μg of sample. These developments accelerate structural studies of biomolecular assemblies available in submilligram quantities without the need of protein deuteration. 相似文献
44.
Assignment of congested NMR spectra: carbonyl backbone enrichment via the Entner-Doudoroff pathway 总被引:1,自引:0,他引:1
Goldbourt A Day LA McDermott AE 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,189(2):157-165
In NMR spectra of complex proteins, sparse isotope enrichment can be important, in that the removal of many (13)C-(13)C homonuclear J-couplings can narrow the lines and thereby facilitate the process of spectral assignment and structure elucidation. We present a simple scheme for selective yet extensive isotopic enrichment applicable for production of proteins in organisms utilizing the Entner-Doudoroff (ED) metabolic pathway. An enrichment scheme so derived is demonstrated in the context of a magic-angle spinning solid-state NMR (MAS SSNMR) study of Pf1 bacteriophage, the host of which is Pseudomonas aeruginosa, strain K (PAK), an organism that uses the ED pathway for glucose catabolism. The intact and infectious Pf1 phage in this study was produced by infected PAK cells grown on a minimal medium containing 1-(13)C d-glucose ((13)C in position 1) as the sole carbon source, as well as (15)NH(4)Cl as the only nitrogen source. The 37MDa Pf1 phage consists of about 93% major coat protein, 1% minor coat proteins, and 6% single-stranded, circular DNA. As a consequence of this composition and the enrichment scheme, the resonances in the MAS SSNMR spectra of the Pf1 sample were almost exclusively due to carbonyl carbons in the major coat protein. Moreover, 3D heteronuclear NCOCX correlation experiments also show that the amino acids leucine, serine, glycine, and tyrosine were not isotopically enriched in their carbonyl positions (although most other amino acids were), which is as expected based upon considerations of the ED metabolic pathway. 3D NCOCX NMR data and 2D (15)N-(15)N data provided strong verification of many previous assignments of (15)N amide and (13)C carbonyl shifts in this highly congested spectrum; both the semi-selective enrichment patterns and the narrowed linewidths allowed for greater certainty in the assignments as compared with use of uniformly enriched samples alone. 相似文献
45.
Easson MW Condon B Dien BS Iten L Slopek R Yoshioka-Tarver M Lambert A Smith J 《Applied biochemistry and biotechnology》2011,165(5-6):1322-1331
In a series of experiments, untreated and ammonium hydroxide pretreated Klenow lowland variety switchgrasses are converted to reducing sugars using low-frequency (20 kHz) ultrasound and commercially available cellulase enzyme. Results from experiments using untreated and pretreated switchgrasses with and without ultrasound are presented and discussed. In untreated switchgrass experiments, the combination of ultrasound and enzymes resulted in an increase of 7.5% in reducing sugars compared to experiments using just enzymes. In experiments using ammonium hydroxide pretreated switchgrass, the combination of ultrasound and enzymes resulted in an increase of 9.3% in reducing sugars compared to experiments using just enzymes. Experimental evidence indicates that there is a synergistic effect from the combination of ultrasound and enzymes which lowers the diffusion-limiting barrier to enzyme/substrate binding and results in an increase in reaction rate. Scanning electron microscopic images provide evidence that ultrasound-induced pitting increases substrate surface area and affects reaction rate and yield. 相似文献
46.
Background
Like all tripartite motif (TRIM) proteins, the retroviral restriction factor TRIM5α consists of RING, B-box 2 and coiled-coil domains, with a C-terminal B30.2(SPRY) domain. Although structures have been determined for some individual TRIM domains, the structure of an intact TRIM protein is unknown. 相似文献47.
Eudes Loren?on Rodrigo G. Lacerda Luiz O. Ladeira Rodrigo R. Resende André S. Ferlauto Ulf Schuchardt Rochel M. Lago 《Journal of Thermal Analysis and Calorimetry》2011,105(3):953-959
Three different forms of carbon, i.e., multi-walled carbon nanotubes (CNTs), single-walled CNTs, and soot, were decorated
with gold nanoparticles by a new method. In this method C10H8
− ions transfer electrons to the CNTs or soot. These electrons on the carbon surface can then reduce Au3+ species to form supported Au nanoparticles with a narrow particle size distribution. Thermogravimetric/differential thermal
analyses (TG/DTA), XRD, Raman, and TEM show that naphthalene molecules remain trapped inside the Au nanoparticles and can
only be removed by treatment at ca. 300 °C. Remarkable effect of the Au nanoparticles on the oxidation of carbon by O2 is also observed by TG/DTA, i.e., on-set oxidation temperature and activation energy (E
a). It is shown that as the Au particle size decreases from 25 to 2 nm a linear decrease of the oxidation temperature is observed.
Au particles larger than 25 nm do not produce any significant effect on carbon oxidation. These results are discussed in terms
of spillover catalytic effect where Au nanoparticles activate O2 molecules to produce active oxygen species which oxidize the different carbon supports. 相似文献
48.
In the late 1970s, in two celebrated papers, Aizenman and Higuchi independently established that all infinite-volume Gibbs measures of the two-dimensional ferromagnetic nearest-neighbor Ising model at inverse temperature ${\beta\geq 0}$ are of the form ${\alpha\mu^{+}_\beta + (1-\alpha)\mu^{-}_\beta}$ , where ${\mu^{+}_\beta}$ and ${\mu^{-}_\beta}$ are the two pure phases and ${0\leq\alpha\leq 1}$ . We present here a new approach to this result, with a number of advantages: (a) We obtain an optimal finite-volume, quantitative analogue (implying the classical claim); (b) the scheme of our proof seems more natural and provides a better picture of the underlying phenomenon; (c) this new approach might be applicable to systems for which the classical method fails. 相似文献
49.
Eszter E. Najbauer Kumar Tekwani Movellan Dr. Tobias Schubeis Dr. Tom Schwarzer Prof. Dr. Kathrin Castiglione Karin Giller Prof. Dr. Guido Pintacuda Dr. Stefan Becker Dr. Loren B. Andreas 《Chemphyschem》2019,20(2):302-310
Determination of the environment surrounding a protein is often key to understanding its function and can also be used to infer the structural properties of the protein. By using proton-detected solid-state NMR, we show that reduced spin diffusion within the protein under conditions of fast magic-angle spinning, high magnetic field, and sample deuteration allows the efficient measurement of site-specific exposure to mobile water and lipids. We demonstrate this site specificity on two membrane proteins, the human voltage dependent anion channel, and the alkane transporter AlkL from Pseudomonas putida. Transfer from lipids is observed selectively in the membrane spanning region, and an average lipid-protein transfer rate of 6 s−1 was determined for residues protected from exchange. Transfer within the protein, as tracked in the 15N-1H 2D plane, was estimated from initial rates and found to be in a similar range of about 8 to 15 s−1 for several resolved residues, explaining the site specificity. 相似文献
50.
Tomas Orlando Rza Derviolu Marcel Levien Igor Tkach Thomas F. Prisner Loren B. Andreas Vasyl P. Denysenkov Marina Bennati 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(5):1416-1420
Nuclear magnetic resonance (NMR) techniques play an essential role in natural science and medicine. In spite of the tremendous utility associated with the small energies detected, the most severe limitation is the low signal‐to‐noise ratio. Dynamic nuclear polarization (DNP), a technique based on transfer of polarization from electron to nuclear spins, has emerged as a tool to enhance sensitivity of NMR. However, the approach in liquids still faces several challenges. Herein we report the observation of room‐temperature, liquid DNP 13C signal enhancements in organic small molecules as high as 600 at 9.4 Tesla and 800 at 1.2 Tesla. A mechanistic investigation of the 13C‐DNP field dependence shows that DNP efficiency is raised by proper choice of the polarizing agent (paramagnetic center) and by halogen atoms as mediators of scalar hyperfine interaction. Observation of sizable DNP of 13CH2 and 13CH3 groups in organic molecules at 9.4 T opens perspective for a broader application of this method. 相似文献