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11.
Papapostolou D Bromley EH Bano C Woolfson DN 《Journal of the American Chemical Society》2008,130(15):5124-5130
Attempts to design peptide-based fibers from first principles test our understanding of protein folding and assembly, and potentially provide routes to new biomaterials. Several groups have presented such designs based on alpha-helical and beta-strand building blocks. A key issue is this area now is engineering and controlling fiber morphology and related properties. Previously, we have reported the design and characterization of a self-assembling peptide fiber (SAF) system based on alpha-helical coiled-coil building blocks. With preceding designs, the SAFs are thickened, highly ordered structures in which many coiled coils are tightly bundled. As a result, the fibers behave as rigid rods. Here we report successful attempts to design new fibers that are thinner and more flexible by further programming at the amino-acid sequence level. This was done by introducing extended, or "smeared", electrostatic networks of arginine and glutamate residues to the surfaces of the coiled-coil building blocks. Furthermore, using arginine--rather than lysine--in these networks plays a major role in the fiber assembly, presumably by facilitating multidentate intra and intercoiled-coil salt bridges. 相似文献
12.
A detailed survey of the low energy isomer spectrum of (SiO(2))(N), N= 6-10, 13, 16 has been performed using interatomic potential based global optimisations refined via high-level density functional calculations. Within these spectra, including many isomers reported for the first time, structurally and energetically viable pathways for the initial stages of silica cluster growth through SiO(2) nucleation are identified. The role of the exceptionally stable (SiO(2))(8) ground state "magic" cluster is highlighted in the possible formation of highly symmetric fully tetrahedral clusters of size (SiO(2))(10) and (SiO(2))(16). These clusters are found to form a part of a natural (SiO(2))(N)N= 7, 10, 13, 16 sequence together with the C(3v) ground states for (SiO(2))(7) and (SiO(2))(13). The fully tetrahedral clusters are argued to be likely relatively long-lived metastable species in the process of gas phase SiO(2) nucleation due to the manner of their termination. It is speculated that larger tetrahedral (SiO(2))(40) clusters may exhibit porous structures. 相似文献
13.
J. Mitroy J. Y. Zhang M. W. J. Bromley K. G. Rollin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(1):15-19
The blackbody radiation shift of the Al+ 3s2
1Se
0 ↦ 3s3p 3P○
0 clock transition is evaluated. The polarizabilities of the two states are determined by means of configuration interaction
calculations in conjunction with oscillator strength sum rules. The ground state polarizability was 24.14 ±0.12 a.u. while
the metastable state polarizability was 24.62 ±0.25 a.u. The derived frequency shift at 300 K was Δν= -0.0042 ±0.0032 Hz.
Some auxiliary sum rules are evaluated that allow for the conversion of a finite frequency polarizability difference to a
static polarizability difference. 相似文献
14.
Particulate gels are known to be formed by bovine β-lactoglobulin near the isoelectric point when partial unfolding is allowed
to occur under heating. The aggregation process of the protein has been investigated within the context of a nucleation and
growth process by preparing gels under precisely controlled thermal histories. This was achieved using a Differential Scanning
Calorimeter (DSC) to provide controlled heating rates, and known final temperatures and incubation times. The resulting particulate
gels were characterized by their particle size and polydispersity using Environmental Scanning Electron Microscopy (ESEM),
which permits hydrated samples to be observed. Particle size was found to decrease with increasing final temperature, with
the aggregation taking longer to reach completion for lower temperatures. Particle size was also found to decrease with increasing
heating rate. This system could be modelled as evolving via nucleation and growth by taking into account the fact that the
concentration of the aggregating species was varying as a function of temperature as well as time. The intrinsic tryptophan
fluorescence as a function of temperature was used as a guide to the fraction of unfolded protein in solution, thereby permitting
successful comparisons between the model predictions and the particle sizes to be made.-1 相似文献
15.
We investigate Si(8)- and Si(16)-based silicate species via global optimisation searches and ab initio calculations and propose a new multi-mechanism interpretation of the experimentally observed atomic mixing of silicate oligomers in solution. 相似文献
16.
17.
Diana Gimenez Dr. Juan A. Aguilar Prof. Elizabeth H. C. Bromley Prof. Steven L. Cobb 《Angewandte Chemie (International ed. in English)》2018,57(33):10549-10553
Stability towards protease degradation combined with modular synthesis has made peptoids of considerable interest in the fields of chemical biology, medicine, and biomaterials. Given their tertiary amide backbone, peptoids lack the capacity to hydrogen‐bond, and as such, controlling secondary structure can be challenging. The incorporation of bulky, charged, or chiral aromatic monomers can be used to control conformation but such building blocks limit applications in many areas. Through NMR and X‐ray analysis we demonstrate that non‐chiral neutral fluoroalkyl monomers can be used to influence the Kcis/trans equilibria of peptoid amide bonds in model systems. The cis‐isomer preference displayed is highly unprecedented given that neither chirality nor charge is used to control the peptoid amide conformation. The application of our fluoroalkyl monomers in the design of a series of linear peptoid oligomers that exhibit stable helical structures is also reported. 相似文献
18.
19.
Bromley ST Mas-Torrent M Hadley P Rovira C 《Journal of the American Chemical Society》2004,126(21):6544-6545
We report on a computational study to understand the high mobility found in dithiophene-tetrathiafulvalene (DT-TTF) transistors, with respect to that known for pentacene, using an extended measure of the reorganization energy (lambdareorg). We demonstrate the high importance of considering intermolecular interactions to assess hole-hopping mobilities. We find that due to the steric, polarizable environment and the structural changes induced by local intermolecular charge delocalization, the calculated lambdareorg for DT-TTF decreases from 0.574 eV in the isolated molecule to 0.042 eV in the crystal embedded molecule, which is of the same order of the previously reported value found for the isolated pentacene molecule, 0.098 eV. 相似文献
20.
To examine the hypothetical cooperative role of enamelin and amelogenin in controlling the growth morphology of enamel crystals in the post-secretory stage, we applied a cation selective membrane system for the growth of octacalcium phosphate (OCP) in the truncated recombinant porcine amelogenin (rP148) with and without the 32kDa enamelin fragment. Enamelin alone inhibited the growth in the c-axis direction more than rP148, yielding OCP crystals with the smallest aspect ratio of all conditions tested. When enamelin was added to the amelogenin "gel-like matrix", the inhibitory action of the protein mixture on the growth of OCP in the c-axis direction was diminished, while that in the b-axis direction was increased. As a result, the length to width ratio (aspect ratio) of OCP crystal was markedly increased. Addition of enamelin to amelogenin enhanced the potential of amelogenin to stabilize the amorphous calcium phosphate (ACP) transient phase. The ratio of enamelin and amelogenin was crucial for stabilization of ACP and the growth of OCP crystals with larger aspect ratio. The cooperative regulatory action of enamelin and amelogenin was attained, presumably, through co-assembling of enamelin and amelogenin. These results have important implications in understanding the growth mechanism of enamel crystals with large aspect ratio. 相似文献