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471.
Constantinos Sakarellos Vassilios Tsikaris Eugenia Panou-Pomonis Charalampos Alexopoulos Maria Sakarellos-Daitsiotis Constantinos Petrovas Panayiotis G. Vlachoyiannopoulos Haralampos M. Moutsopoulos 《International journal of peptide research and therapeutics》1997,4(4-6):447-454
Summary The PPGMRPP sequence, found in several copies in the Sm and U1RNP autoantigens, is the main target of anti-Sm and anti-U1RNP
antibodies in systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD) patient's sera. It is also recognized,
to a lower extent, by anti-Ro/SSA and anti-La/SSB specificities. The PPGMRPP-NH2 peptide amide and the PPGMRPP peptide, which is bound to a pentameric sequential oligopeptide carrier (SOC5), were examined by1H-NMR spectroscopy and ELISA assays, using sera from patients with autimmune rheumatic diseases. Among the three main conformers
found for the free PPGMRPP, the extended one was also identified for PPGMRPP-NH2 and (PPGMRPP)5-SOC5. This can be attributed to the absence of ionic interactions between the Arg-guanidinium and the carboxylate group in the
amide and SOC5-bound forms of the peptide. Immunoassays using sera from various specificities showed an enhanced anti-Sm and anti-U1RNP
recognition of PPGMRPP-NH2 and (PPGMRPP)5-SOC5, and lowering of the anti-Ro/SSA and anti-La/SSB reactivity. The presence of multiple conformers of free PPGMRPP may explain
the unexpected cross-reactivity to the anti-Ro/La positive sera, while the prevalence of the extended conformation in PPGMRPP-NH2 and (PPGMRPP)5-SOC5 is mainly responsible for the enhanced recognition from the anti-Sm and anti-U1RNP autoantibodies. it is concluded that the
antigenic specificity of PPGMRPP-NH2 and (PPGMRPP)5-SOC5 is mainly induced by conformational changes resulting from the conversion of the C-terminal carboxylate group to the amide
form. 相似文献
472.
473.
474.
Constantinos J. Limas Catherine Limas 《Biochimica et Biophysica Acta (BBA)/General Subjects》1979,582(3):533-536
Responsiveness to inotropic agents is altered in hypertension and may contribute to its initiation and maintenance. A biochemical basis for this change was provided by the observation that the number of β-adrenergic receptors, as reflected in specific [3H]dihydroalprenolol binding, was diminished in both arteries and veins of spontaneously hypertensive rats. There was no change in the affinity of dihydroalprenolol for the binding sites or in the capacity of isoproterenol to displace dihydroalprenolol. The decline in β-adrenergic receptor numbers is not secondary to blood pressure elevation but may, instead, contribute to the pathogenesis of hypertension. 相似文献
475.
Suppression of lymphocyte transformation by 16, (16) dimethyl prostaglandin E2 and unsaturated fatty acids. 总被引:4,自引:0,他引:4
A A Mihas R G Gibson B I Hirschowitz 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1975,149(4):1026-1028
A new synthetic prostaglandin (16, 16-PGE2) and unsaturated fatty acids have been shown to inhibit the incorporation of [3H]thymidine in the lymphocyte transformation reaction in response to phytohemagglutinin (PHA). This inhibition was not due to toxicity of these substances, for the lymphocytes remained intact and capable of excluding trypan blue. 相似文献
476.
477.
Constantinos J. Limas 《Biochemical and biophysical research communications》1980,96(3):1378-1383
Cardiac sarcoplasmic reticulum is phosphorylated by a cytosolic Ca2+-activated, phospholipid-dependent protein kinase. This phosphorylation is independent of cyclic nucleotides and enhanced by unsaturated diacylglycerols; saturated diacylglycerols, mono- and tri-glycerides are ineffective. Diacylglycerol stimulation is due to increased Ca2+ sensitivity of the kinase reaction. Protein kinase catalyzed phosphorylation results in enhanced Ca2+-transport ATPase activity and may be an important determinant of cardiac sarcoplasmic reticulum function. 相似文献
478.
Vassilios Tsikaris Evangelos Detsikas Maria Sakarellos-Daitsiotis Constantinos Sakarellos Efstratia Vatzaki Socrates J. Tzartos Michel Marraud Manh Thong Cung 《Biopolymers》1993,33(7):1123-1134
The conformational properties of two [D -A70, A76] and [Aib70, A76] analogues of the α67–76 Torpedo acetylcholine receptor fragment, with low binding capacity for the anti main immunogenic region (MIR) antibodies, were studied in DMSO by two-dimensional nmr techniques and molecular dynamics simulations. The results were compared to the free and bound conformations of the [A76] analogue, which has twice more affinity for the anti-MIR monoclonal antibody 6 (mAb6), than the natural Torpedo sequence. It appeared that a single substitution of the A70, at a crucial position, by the D -A70 or Aib70, could modify completely the conformational behavior of the peptide and reduced its recognition by the anti-MIR antibody. The WNPADY rigid structure at the N-terminal part was essential for antibody recognition. The adjacent more flexible C-terminal sequence (GGIK) gives additional stability to the monoclonal antibody–peptide complex probably due to an adequate orientation of the peptide side chains in the complex, by setting them in close contact with the antibody. © 1993 John Wiley & Sons, Inc. 相似文献
479.
480.
Athanassios Stavrakoudis Ioannis N. Demetropoulos Constantinos Sakarellos Maria Sakarellos-Daitsiotis Vassilios Tsikaris 《International journal of peptide research and therapeutics》1997,4(4-6):481-487
Summary The design, synthesis and catalytic properties of a cyclic branched peptide carrier that possesses the catalytic triad residues
of the serine proteases is reported. The synthesis of the peptide model was totally completed on solid support using three
different orthogonal amino protecting groups. Hydrolytic activity measurements against Suc-Ala-Ala-Ala-pNA substrate showed
that it is hydrolysed by the peptide model to a small extent. Despite this small hydrolytic activity, it is the first time,
to our knowledge, that hydrolysis of such a substrate is reported by an enzyme model compound. Contrary, this enzyme model
peptide showed considerable activity against the Boc-Ala-pNP substrate (k
cat
=0.414 min−1 andK
m
=0.228 mm). These results suggest that the designed carrier brings in appropriate contact the catalytic triad residues (Ser,
His, Asp) resulting in the obtained hydrolytic activity. 相似文献