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101.
102.
Lai JR Fisk JD Weisblum B Gellman SH 《Journal of the American Chemical Society》2004,126(34):10514-10515
The coiled-coil, which consists of two or more interwoven amphiphilic alpha-helices, is formed by sequences that have a characteristic heptad repeat (abcdefg) where a and d are hydrophobic residues. Most efforts to elucidate the origins of coiled-coil pairing selectivity have focused on electrostatic interactions among side chains that flank the core (positions e and g) and on polar side chains that occur occasionally at core positions. We have used phage display to explore another source of coiled-coil specificity: steric matching among nonpolar side chains in the core. We introduced a destabilizing Leu-->Ala mutation into the core of one helix in a known heterodimer and then screened a phage-based library of potential partner helices in search of compensating mutations. We identified a new heterodimer pair (30 residues/helix) that is comparable in stability to the GCN4-p1 homodimer (33 residues/helix). Furthermore, the Leu-->Ala mutant shows specificity for its phage-derived partner over the original partner despite their similar sequences. These results show that a phage-based approach can provide unique insights on coiled-coil pairing preferences that should facilitate both the analysis of natural sequences and the development of specific dimerization motifs that are orthogonal to one another. 相似文献
103.
Eldred SE Stone DA Gellman SH Stahl SS 《Journal of the American Chemical Society》2003,125(12):3422-3423
The carboxamide group is generally inert, except under harsh conditions or in the presence of highly evolved enzymes. We have identified several metal complexes that efficiently catalyze transamidation reactions of amide/amine mixtures under moderate conditions. This unprecedented reactivity represents an important step toward our long-term goal of using dynamic combinatorial chemistry to generate new amide-based molecules with interesting structures and functions. 相似文献
104.
Vanessa M. Kung Gabriel Cornilescu Samuel H. Gellman 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(48):14544-14547
We have examined whether parallel β‐sheet secondary structure becomes more stable as the number of β‐strands increases, via comparisons among peptides designed to adopt two‐ or three‐stranded parallel β‐sheet conformations in aqueous solution. Our three‐strand design is the first experimental model of a triple‐stranded parallel β‐sheet. Analysis of the designed peptides by nuclear magnetic resonance (NMR) and circular dichroism (CD) spectroscopy supports the hypothesis that increasing the number of β‐strands, from two to three, increases the stability of the parallel β‐sheet. We present the first experimental evidence for cooperativity in the folding of a triple‐stranded parallel β‐sheet, and we show how minimal model systems may enable experimental documentation of characteristic properties, such as CD spectra, of parallel β‐sheets. 相似文献
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We demonstrate that 14-helical beta-peptides can self-assemble to form lyotropic liquid crystalline (LC) phases in water. beta-Peptides 1-4 were designed to form globally amphiphilic 14-helices of increasing length. Optical microscopy showed that several of these beta-peptides formed LC phases in aqueous solutions at concentrations as low as 2.5 wt % (15 mM). Liquid crystallinity appears to require the adoption of a globally amphiphilic conformation because a scrambled sequence, 5, does not display LC behavior. Thermal stability and reversibility of LC phase formation were assessed by variable temperature 2H NMR spectroscopy and optical microscopy. The LC phase formed by beta-peptide 3 at 10 wt % is disrupted above 40 degrees C in D2O and re-forms within minutes upon cooling. LC phase behavior for solutions of 3 is influenced by concentration and net charge. These studies demonstrate that highly folded 14-helical beta-peptides can produce LC phases at shorter lengths than do alpha-helical alpha-peptide mesogens and can provide a basis for tailoring properties of LC phases for future applications. 相似文献
108.
Schmitt MA Choi SH Guzei IA Gellman SH 《Journal of the American Chemical Society》2006,128(14):4538-4539
Foldamers, oligomers with strong folding propensities, are subjects of growing interest because such compounds offer unique scaffolds for the development of molecular function. We report two new foldamer classes, oligopeptides with regular 1:2 or 2:1 patterns of alpha- and beta-amino acid residues. Two distinct helical conformations are detected via 2D NMR in methanol for each backbone. One of the helices for each backbone is characterized via X-ray crystallography. 相似文献
109.
Organocatalytic Mannich addition of aldehydes to a formaldehyde-derived iminium species catalyzed by proline-derived chiral pyrrolidines provides beta-amino aldehydes with >/=90% ee. Mechanistic analysis of the proline-catalyzed reactions suggests that non-hydrogen-bonded ionic interactions at the Mannich reaction transition state can influence stereochemical outcome. The beta-amino aldehydes from our process bear a substituent adjacent to the carbonyl and can be efficiently converted to protected beta2-amino acids, which are important building blocks for beta-peptide foldamers that display useful biological activities. 相似文献
110.
In this paper, we first establish a Schwarz?CPick type theorem for pluriharmonic mappings and then we apply it to discuss the equivalent norms on Lipschitz-type spaces. Finally, we obtain several Landau??s and Bloch??s type theorems for pluriharmonic mappings. 相似文献