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41.
PHOTOTRANSFORMATION OF AGGREGATED FORMS OF PROTOCHLOROPHYLLIDE IN ISOLATED ETIOPLAST INNER MEMBRANES 总被引:1,自引:0,他引:1
Bela Boddi Agneta Lindsten Margareta Ryberg Christer Sundqvist 《Photochemistry and photobiology》1990,52(1):83-87
Abstract— Irradiation of an etioplast inner membrane fraction caused the transformation of two photoactive spectroscopically different protochlorophyllide forms into two chlorophyllide forms. A weak light flash, 6% of a saturating flash, preferentially caused the formation of a short wavelength chlorophyllide form absorbing at 672 nm and emitting at 676 nm. A saturating flash resulted in the formation of the 684 nm absorbing form of chlorophyllide with an emission maximum at 698 nm.
The circular dichroism (CD) signals of the newly formed chlorophyllide forms indicated that they are pigment aggregates of different sizes. These aggregates are probably connected to protochlorophyllide reductase and NADPH or NADP. In the absence of NADPH a decomposition of the pigment aggregates took place as revealed by a decrease in the CD-signal. A model is suggested which describes the structural changes of the pigment-protein aggregates after irradiation. 相似文献
The circular dichroism (CD) signals of the newly formed chlorophyllide forms indicated that they are pigment aggregates of different sizes. These aggregates are probably connected to protochlorophyllide reductase and NADPH or NADP. In the absence of NADPH a decomposition of the pigment aggregates took place as revealed by a decrease in the CD-signal. A model is suggested which describes the structural changes of the pigment-protein aggregates after irradiation. 相似文献
42.
We consider viscous Burgers equations in one dimension of space and derive their solutions from stochastic variational principles on the corresponding group of homeomorphisms. The metrics considered on this group are L p metrics. The velocity corresponds to the drift of some stochastic Lagrangian processes. Existence of minima is proved in some cases by direct methods. We also give a representation of the solutions of viscous Burgers equations in terms of stochastic forward-backward systems. 相似文献
43.
Turecek F Jones JW Towle T Panja S Nielsen SB Hvelplund P Paizs B 《Journal of the American Chemical Society》2008,130(44):14584-14596
Protonated peptides containing histidine or arginine residues and a free carboxyl group (His-Ala-Ile, His-Ala-Leu, Ala-His-Leu, Ala-Ala-His-Ala-Leu, His-Ala-Ala-Ala-Leu, and Arg-Ala-Ile) form stable anions upon collisional double electron transfer from Cs atoms at 50 keV kinetic energies. This unusual behavior is explained by hidden rearrangements occurring in peptide radical intermediates formed by transfer of the first electron. The rearrangements occur on a approximately 120 ns time scale determined by the radical flight time. Analysis of the conformational space for (His-Ala-Ile + H)(+) precursor cations identified two major conformer groups, 1a(+)-1m(+) and 5a(+)-5h(+) , that differed in their H-bonding patterns and were calculated to collectively account for 39% and 60%, respectively, of the gas-phase ions. One-electron reduction in 1a(+) and 5a(+) triggers exothermic hydrogen atom migration from the terminal COOH group onto the His imidazole ring, forming imidazoline radical intermediates. The intermediate from 5a is characterized by its charge and spin distribution as a novel cation radical-COO(-) salt bridge. The intermediate from 1a undergoes spontaneous isomerization by imidazoline N-H migration, re-forming the COOH group and accomplishing exothermic isomerization of the initial (3H)-imidazole radical to a (2H)-imidazole radical. An analogous unimolecular isomerization in simple imidazole and histidine radicals requires activation energies of 150 kJ mol(-1), and its occurrence in 1a and 5a is due to the promoting effect of the proximate COOH group. The rearrangement is substantially reduced in Ala-Leu-His due to an unfavorable spatial orientation of the imidazole and COOH groups and precluded in the absence of a free carboxyl group in His-Ala-Leu amide. In contrast to His-Ala-Ile and Arg-Ala-Ile, protonated Lys-Ala-Ile does not produce stable anions upon double electron transfer. The radical trapping properties of histidine residues are discussed. 相似文献
44.
Jean-Marc Martel Belaïd Aouni 《The Journal of the Operational Research Society》1990,41(12):1121-1132
Many algorithms have been developed for multiple-criteria decision-making problems. Goal programming (GP) is one of these algorithms. This model is a special extension of linear programming. Usually, it is not easy for the decision-maker to choose his aspiration levels a priori. Moreover, the incommensurability of the measurement units of the various objectives creates an aggregation problem. However, in the standard GP formulation, the decision-maker is not required to arbitrate among conflicting objectives. To deal with these difficulties, we explicitly introduce the structure of the decision-maker's preferences into the GP model in order to evaluate the impact of deviations from the decision-maker's aspirations levels. Easily and naturally, the idea of a generalized criterion, as introduced in the Promethee outranking method, will be used to build this structure of preferences. 相似文献
45.
Chass GA Mirasol RS Setiadi DH Tang TH Chin W Mons M Dimicoli I Dognon JP Viskolcz B Lovas S Penke B Csizmadia IG 《The journal of physical chemistry. A》2005,109(24):5289-5302
Computational and experimental determinations were carried out in parallel on the conformational probability of N-Acetyl-Phenylalanine-NH2 (NAPA). Ab initio computations were completed at the BLYP/6-311G(df,p), B3LYP/6-31G(d), B3LYP/6-31G(d,p), and B3LYP/6-31+G(d) levels of theory, labeled L/61fp, B/6, B/6p, and B/6+, respectively. Three experimentally identified conformers were compared with theoretical data, confirming their identities as the betaLanti, gammaLgauche+, and gammaLgauche- (BACKBONESIDECHAIN) conformers. Evidence comes from matching experimental and theoretical data for all three constituent N-H stretches of NAPA, with a Delta(Experimental-Theoretical) = approximately 1-3 cm(-1), approximately 0-5 cm(-1), and approximately 1-6 cm(-1), at the L/61fp and B/6+ levels, respectively. Corrected-ZPE relative energies were computed to be 0.14, 0.00, 0.26 and 0.00, 0.67, 0.57 (kcal*mol(-1)) for the betaLanti, gammaLgauche+, and gamma(Lgauche- conformers, respectively, at the L/61fp and B/6+ levels, respectively. The MP2/6-31+G(d) level of theory was subsequently found to give similar relative energies. Characterization of the intramolecular interactions responsible for red and blue shifting of the N-H stretches showed the existence of the following intramolecular interactions: C=O[i]- - -HN[i], (Ar[i])-Cgamma- - -HN[i+1], (Ar[i])-Cdelta-H- - -O=C[i-1] for betaLanti; C=O[i-1]- - -HN[i+1], (Ar[i])-Cgamma- - -HN[i+1], (Ar[i])-C-H- - -O=C[i] for gammaLgauche+; and C=O[i-1]- - -HN[i+1] for gammaLgauche-. Each of these interactions were further investigated and subsequently characterized by orbital population and Atoms-In-Molecules (AIM) analyses, with the identity of overlap and bond critical points (BCP) serving as 'scoring criteria', respectively. Experimental and theoretical carbonyl stretches were also compared and showed good agreement, adding further strength to the synergy between experiment and theory. 相似文献
46.
We study the weighted integral transform on a compact manifold with boundary over a smooth family of curves Γ. We prove generic
injectivity and a stability estimate under the condition that the conormal bundle of Γ covers T
*
M.
Second author was partly supported by NSF Grant DMS-0400869; third author was partly supported by NSF and a Walker Family
Endowed Professorship. 相似文献
47.
Controlled hydrolysis of proteins to generate peptide ladders combined with mass spectrometric analysis of the resultant peptides
can be used for protein sequencing. In this paper, two methods of improving the microwave-assisted protein hydrolysis process
are described to enable rapid sequencing of proteins containing disulfide bonds and increase sequence coverage, respectively.
It was demonstrated that proteins containing disulfide bonds could be sequenced by MS analysis by first performing hydrolysis
for less than 2 min, followed by 1 h of reduction to release the peptides originally linked by disulfide bonds. It was shown
that a strong base could be used as a catalyst for microwave-assisted protein hydrolysis, producing complementary sequence
information to that generated by microwave-assisted acid hydrolysis. However, using either acid or base hydrolysis, amide
bond breakages in small regions of the polypeptide chains of the model proteins (e.g., cytochrome c and lysozyme) were not detected. Dynamic light scattering measurement of the proteins solubilized in an acid or base indicated
that protein-protein interaction or aggregation was not the cause of the failure to hydrolyze certain amide bonds. It was
speculated that there were some unknown local structures that might play a role in preventing an acid or base from reacting
with the peptide bonds therein. 相似文献
48.
Cellulose synthase (CESA) molecules are the building blocks and catalytic centers of the CESA complex. The study of mutants in Arabidopsis has led to insight into the structure of these nanomachines. Inside the plasma membrane, the CESA molecules are arranged in complexes, which, apart from the CESA molecules proper, contain other, mostly unidentified, proteins. We developed a theory in which CESA density, together with distance between cellulose microfibrils (CMFs) being deposited and cell geometry, determines wall texture. We have shown earlier how this theory is able to explain the production of axial, helical, helicoid and crossed-polylamellate textures. In the present article we extend this theory to random wall textures. 相似文献
49.
D. Eilidh Sood Sue Champion Daniel M. Dawson Sonia Chabbra Bela E. Bode Andrew Sutherland Allan J. B. Watson 《Angewandte Chemie (International ed. in English)》2020,59(22):8460-8463
Deoxyfluorination is a primary method for the formation of C?F bonds. Bespoke reagents are commonly used because of issues associated with the low reactivity of metal fluorides. Reported here is the development of a simple strategy for deoxyfluorination, using first‐row transition‐metal fluorides, and it overcomes these limitations. Using CuF2 as an exemplar, activation of an O‐alkylisourea adduct, formed in situ, allows effective nucleophilic fluoride transfer to a range of primary and secondary alcohols. Spectroscopic investigations have been used to probe the origin of the enhanced reactivity of CuF2. The utility of the process in enabling 18F‐radiolabeling is also presented. 相似文献
50.
Summary We review a new truncation/recoupling method to obtain eigenvalues and eigenvectors of anF-mode vibrational Hamiltonian. In particular we focus on the block diagonalization aspects of the method which are ideal for massive parallelization, and we demonstrate this using H2O2 as an example. We then present vibrational energies for non-rotating HO2 and HCN, which illustrate several key advantages of this method. 相似文献