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81.
Hari D Upadhyaya Sangam L Dwivedi Michael Baum Rajeev K Varshney Sripada M Udupa Cholenahalli LL Gowda David Hoisington Sube Singh 《BMC plant biology》2008,8(1):106
Background
Plant genetic resources (PGR) are the basic raw materials for future genetic progress and an insurance against unforeseen threats to agricultural production. An extensive characterization of PGR provides an opportunity to dissect structure, mine allelic variations, and identify diverse accessions for crop improvement. The Generation Challenge Program conceptualized the development of "composite collections" and extraction of "reference sets" from these for more efficient tapping of global crop-related genetic resources. In this study, we report the genetic structure, diversity and allelic richness in a composite collection of chickpea using SSR markers, and formation of a reference set of 300 accessions. 相似文献82.
Alanine substitutions were made for 15 amino acids in the cytoplasmic loop between transmembrane helices 6 and 7 (L6/7) of the human alpha(1)-subunit of Na,K-ATPase. Most mutations reduced Na,K-ATPase activity by less than 50%; however, the mutations R834A, R837A, and R848A reduced Na,K-ATPase activity by 75, 89, and 66%, respectively. Steady-state phosphoenzyme formation from ATP was reduced in mutants R834A, R837A, and R848A, and R837A also had a faster E(2)P --> E(2) dephosphorylation rate compared with the wild-type enzyme. Effects of L6/7 mutations on the phosphorylation domain of the protein were also demonstrated by (18)O exchange, which showed that intrinsic rate constants for P(i) binding and/or reaction with the protein were altered. Although most L6/7 mutations had no effect on the interaction of Na(+) or K(+) with Na,K-ATPase, the E825A, E828A, R834A, and R837A mutations reduced the apparent affinity of the enzyme for both Na(+) and K(+) by 1.5-3-fold. 1-Bromo-2,4,6-tris(methylisothiouronium)benzene (Br-TITU(3+)), a competitive antagonist of Rb(+) and Na(+) occlusion, was used to test whether charged residues in L6/7 are involved in binding monovalent cations and cation antagonists. Br-TITU(3+) inhibited ouabain binding to wild type Na,K-ATPase with an IC(50) of 30 microM. Ouabain binding to the E825A, E828A, R834A, or R837A mutants was still inhibited by Br-TITU(3+), indicating that Br-TITU(3+) does not bind to charged residues in L6/7. This observation makes it unlikely that L6/7 functions as a cytoplasmic cation binding site in Na,K-ATPase, and together with the effects of L6/7 mutations on phosphate interactions with the enzyme suggests that L6/7 is important in stabilizing the phosphorylation domain and its relationship to the ion binding sites of the protein. 相似文献
83.
84.
Three species of dwarf, prostrate willow ( Salix arctica , S. rotundifolia and S. herbacea ) were subjected to experimental summer warming in high arctic Canada, arctic Alaska, and subarctic Sweden, respectively, as part of the International Tundra Experiment. Phenological and growth responses of these species were compared for the second season of the experiment. Stigmas became receptive and pollen dispersal occurred significantly earlier for S. rotundifolia and S. herbacea in the ITEX open-top chambers, but not for S. arctica . Warming had no effect on the timing of seed dispersal, leaf yellowing, or leaf senescence. The length and dry weight of the largest leaves were greater for warmed plants, and was significant for S. rotundifolia . The number of catkins/plot did not differ among species or treatments, but the fruit : flower ratio was reduced in the experimental plots. 相似文献
85.
86.
Trapaidze A Hureau C Bal W Winterhalter M Faller P 《Journal of biological inorganic chemistry》2012,17(1):37-47
The peptides Asp-Ala-His-Lys (DAHK) and Gly-His-Lys (GHK) are naturally occurring Cu(II)-chelating motifs in human serum and
cerebrospinal fluid. Here, the sensitive thermodynamic technique isothermal titration calorimetry was used to study the energetics
of Cu(II) binding to DAHK and GHK peptides in the presence of the weaker ligand glycine as a competitor. DAHK and GHK bind
Cu(II) predominantly in a 1:1 stoichiometry with conditional dissociation constants [i.e., at pH 7.4, in the absence of the
competing chelators glycine and 2-(4-(2-hydroxyethyl)-1-piperazinyl)ethanesulfonic acid buffer] of 2.6 ± 0.4 × 10−14 M and 7.0 ± 1.0 × 10−14 M, respectively. Furthermore, the apparent ΔH values were measured and the number of protons released upon Cu(II) binding was determined by performing experiments in different
buffers. This allowed us to determine the conditional ΔG, ΔH, and ΔS, i.e., corrected for the contributions of the weaker ligand glycine and the buffer at pH 7.4. We found that the entropic
and enthalpic contributions to the Cu(II) binding to GHK and DAHK are distinct, with a enthalpic contribution for GHK. The
thermodynamic parameters obtained correspond well to those in the literature obtained by other techniques, suggesting that
the use of the weaker ligand glycine as a competitor in isothermal titration calorimetry provides accurate data for Cu(II)
binding to high-affinity peptides, which cannot be accurately determined without the use of a competitor ligand. 相似文献
87.
Luc Guilloreau Luminita Damian Yannick Coppel Honoré Mazarguil Mathias Winterhalter Peter Faller 《Journal of biological inorganic chemistry》2006,11(8):1024-1038
The aggregation of the peptide amyloid-β (Aβ) to form amyloid plaques is a key event in Alzheimer’s disease. It has been shown that CuII can bind to soluble Aβ and influence its aggregation properties. Three histidines and the N-terminal amine have been proposed to be involved in its coordination. Here, for the first time, we show isothermal titration calorimetry (ITC) measurements of the CuII binding to Aβ16 and Aβ28, models of the soluble Aβ. Moreover, different spectroscopic methods were applied. The studies revealed new insights into these CuII–Aβ complexes: (1) ITC showed two CuII binding sites, with an apparent K
d of 10−7 and 10−5 M, respectively; (2) the high-affinity site has a smaller enthalpic contribution but a larger entropic contribution than the low-affinity binding site; (3) azide did not bind to CuII in the higher-affinity binding site, suggesting the absence of a weak, labile ligand; (4) azide could bind to the CuII in the low-affinity binding site in Aβ28 but not in Aβ16; (5) 1H-NMR suggests that the carboxylate of aspartic acid in position 1 is involved in the ligation to CuII in the high-affinity binding site; (6) the pK
a of 11.3 of tyrosine in position 10 was not influenced by the binding of 2 equivalents of CuII.Electronic Supplementary Material Supplementary material is available to authorized users in the online version of this article at . 相似文献
88.
Durand J Meloni G Talmard C Vašák M Faller P 《Metallomics : integrated biometal science》2010,2(11):741-744
The reactive oxygen species H?O? promotes the Zn?-metallothionein-3 induced Aβ(40) aggregation of fibrillar type structures via slow cysteine oxidation and Zn(2+) release, whereas amorphous aggregates are formed by addition of Zn(2+) to Aβ(40). 相似文献
89.
90.
Bailey S Bolognese B Faller A Louis-Flamberg P MacPherson DT Mayer RJ Marshall LA Milner PH Mistry J Smith DG Ward JG 《Bioorganic & medicinal chemistry letters》1999,9(21):3165-3170
Using a variety of alpha-hydroxy hydroxamic acid derivatives, the size and shape of the S1' pocket for the CD23 processing metalloprotease has been explored. It has been demonstrated that a P1' 2-naphthylmethyl group occupies most of the available space and gives excellent selectivity against fibroblast collagenase (matrix metalloproteinase-1, MMP-1) and other MMPs. 相似文献