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841.
G Zetler 《Peptides》1984,5(4):729-736
The smooth muscle stimulatory effects of cholecystokinin octapeptide (CCK-8), ceruletide (CER), ten analogues of CER, and carbachol were studied in isolated organs of the guinea pig and the mouse (stomach, ileum, duodenum, colon and gallbladder). On a molar basis, CCK-8 and CER had in all organs except stomach greater potency (lower EC50) than carbachol. The effectiveness (Emax) of CCK-8 and CER was in the gut less than that of carbachol, in the guinea pig gallbladder equal with and in the mouse gallbladder superior to that of carbachol. The alteration of peptide structure was virtually without influence on effectiveness; however, it greatly modified the potency and the organ selectivity of the effect. There was no clear-cut correlation between the potency to stimulate smooth muscle and to alter the behavior of the mouse. 相似文献
842.
Mark Leason Denise Cunliffe Donald Parkin Peter J. Lea Benjamin J. Miflin 《Phytochemistry》1982,21(4):855-857
The kinetics of the inhibition of glutamine synthetase from Pisum sativum leaves by l-methionine sulphoximine and dl-phosphinothricin were determined. Inhibition by both compounds was mixed-competitive, and apparent Ki values of 0.16 mM and 0.073 mM respectively were determined. dl-5-Hydroxylysine, dl-glutamate-4-tetrazole and l-4-methyleneglutamic acid were also strong inhibitors. Analogues of methionine sulphoximine, dl-ethionine sulphoximine and dl-prothionine sulphoximine were poor inhibitors of glutamine synthetase. Other glutamine and glutamate analogues e.g. azaserine, albizziine, asparagine and kainic acid had no inhibitory action. 相似文献
843.
Phosphonic acids are the only phosphorus-containing organic compounds detected in the Murchison meteorite. We earlier described
the synthesis of methyl-, hydroxymethyl-, and 1-hydroxyethyl phosphonic acids using sodium phosphite as a source of phosphite
radicals. We now show that ultraviolet irradiation of dilute aqueous solutions of acetylene in the presence of sodium phosphite
leads to the synthesis of vinyl phosphonic acid. At neutral to basic pH, vinyl phosphonic acid reacts under photochemical
conditions to produce phosphonoacetaldehyde and 2-hydroxyethyl phosphonic acid as the major products, as well as smaller yields
of 1-hydroxyethyl phosphonic acid, phosphonoacetic acid, and ethyl phosphonic acid. Of these products, phosphonoacetaldehyde
is particularly interesting as a potential precursor of prebiotic carbohydrate derivatives.
Received: 22 July 1996 / Accepted: 13 September 1996 相似文献
844.
Two tris(1-organo-imidazol-2-ylthio)methanes, HC(S-timR)3 (R = organo = methyl, tert-butyl), have been prepared by a triphasic reaction between chloroform, the appropriate heterocycle, and saturated aqueous solutions of Na2CO3, in the presence of a phase transfer agent, (NBu4)(Br). These ligands have been characterized both spectroscopically and by single crystal X-ray diffraction. The reaction chemistry of these potentially N,N,N-tripodal ligands with AgBF4 was also explored where simple 1:1 coordination complexes could be isolated from reactions performed in THF solution at room temperature. The derivative {Ag[HC(S-timMe)3]}(BF4) was structurally characterized which showed that the ligand binds in a μ-κ2N,κ1N-mode to give a coordination polymer with an interesting layered supramolecular structure. Surprisingly, heating CH3CN solutions of the silver complexes at reflux resulted in decomposition of the complex and concomitant isomerization of the ligands to give metal-free tris(3-organo-1-imidazole-2-thione)methane, HC(N-imtR)3; the heretofore elusive charge-neutral analogues of the well-studied ‘soft scorpionate’ TmR− anions. The solution isomerization of HC(S-timR)3 to HC(N-imtR)3 was found to be general, occurring in a variety of solvents with any of a host of different Lewis acids [para-toluenesulfonic acid, KPF6, and M(CO)5Br (M = Mn, Re)] but did not occur by heating in the absence of Lewis acid. The compound HC(N-imtMe)3 exhibited unusually low solubility in common organic solvents. Single crystal X-ray diffraction of HC(N-imtMe)3 revealed a remarkable honeycomb supramolecular structure with ca. 5 Å channels filled with solvent. The robust nature of this solid is a result of strong dipolar stacking interactions of molecules into polymer chains bolstered by concerted π-π and CH-π interactions involving the heterocycles, holding the chains together in the remaining two dimensions. 相似文献
845.
Maria Terêsa Machini Miranda A. Grey Craig Charleen Miller Rodger A. Liddle Jean E. Rivier 《Journal of Protein Chemistry》1993,12(5):533-544
The synthesis of [Phe(p-CH2SO3Na)52, Nle32,53,56 Nal55]-CCK20–58, [Tyr52, Nle32,53,56, Nal55]-CCK-58 and of [Phe(p-CH2SO3Na)52, Nle32,53,56, Nal55]-CCK-58 using the (9-fluorenylmethyloxy)-carbonyl (Fmoc) strategy on a 2,4-DMBHA resin is described. The crude peptide preparations were extremely complex when analyzed by RP-HPLC, capillary zone electrophoresis (CZE), and ion-exchange chromatography (IE-FPLC). We found that the most effective strategy for purification included cation-exchange chromatography followed by a RP-HPLC desalting step. The highly purified peptides (purity greater than 90%) were characterized by RP-HPLC, size exclusion HPLC (SEC), IE-FPLC, CZE, mass spectrometry, amino acid analysis, and Edman sequence analysis {for [Tyr52, Nle32,53,56, Nal55]-CCK-58}. The results demonstrate the applicability of the 2,4-DMBHA resin for Fmoc solid-phase synthesis of long peptides amides (58 residues in length in this case) as well as the efficacy of an FPLC/RP-HPLC approach for the purification of very long, heterogeneous crude peptides, allowing a true assessment of the biological properties of these analogs to be carried out. [Phe(p-CH2SO3Na)52, Nle32,53,56, Nal55]-CCK20–58 was less than 1% as potent as CCK-8 while [Tyr52, Nle32,53,56, Nal55]-CCK-58 and [Phe(p-CH2SO3Na)52, Nle32,53,56, Nal55]-CCK-58 were inactive at the doses tested (<0.01%). 相似文献
846.
A vancomycin aglycon analogue that possesses a reduced C-ring and an intact E-ring chloride was prepared and its antimicrobial activity towards Staphylococcus aureus and binding affinity to model cell wall ligands were established. Comparison of the derivative with a series of vancomycin aglycon analogues that possess and lack the chloro substituents on the aryl C- and E-rings defines the impact and further refines the role the C-ring chloride plays in promoting both target binding affinity and binding selectivity for d-Ala-d-Ala and its impact on antimicrobial activity. 相似文献
847.
《Peptides》2017
Currently, antimicrobial peptides have attracted considerable attention because of their broad-sprectum activity and low prognostic to induce antibiotic resistance. In our study, for the first time, a series of side-chain hybrid dimer peptides J-AA (Anoplin-Anoplin), J-RR (RW-RW), and J-AR (Anoplin-RW) based on the wasp peptide Anoplin and the arginine- and tryptophan-rich hexapeptide RW were designed and synthesized by click chemistry, with the intent to improve the antimicrobial efficacy of peptides against bacterial pathogens. The results showed that all dimer analogues exhibited up to a 4–16 fold increase in antimicrobial activity compared to the parental peptides against bacterial strains. Furthermore, the antimicrobial activity was confirmed by time-killing kinetics assay with two strains which showed that these dimer analogues at 1, 2 × MIC were rapidly bactericidal and reduced the initial inoculum significantly during the first 2–6 h. Notably, dimer peptides showed synergy and additivity effects when used in combination with conventional antibiotics rifampin or penicillin respectively against the multidrug-resistant strains. In the Escherichia coli-infected mouse model, all of hybrid dimer analogues had significantly lower degree of bacterial load than the untreated control group when injected once i.p. at 5 mg/kg. In addition, the infected mice by methicillin-resistant (MRSA) strain could be effectively treated with J-RR. All of dimer analogues had membrane-active action mode. And the membrane-dependent mode of action signifies that peptides functions freely and without regard to conventional resistant mechanisms. Circular dichroism analyses of all dimer analogues showed a general predominance of α-helix conformation in 50% trifluoroethanol (TFE). Additionally, the acute toxicities study indicated that J-RR or J-AR did not show the signs of toxicity when adult mice exposed to concentration up to 120 mg/kg. The 50% lethal dose (LD50) of J-AA was 53.6 mg/kg. In conclusion, to design and synthesize side chain-hybrid dimer analogues via click chemistry may offer a new strategy for antibacterial therapeutic option. 相似文献
848.
Biosynthesis and metabolism of brassinosteroids 总被引:4,自引:0,他引:4
Natural brassinosteroids so far identified from various plant species include biosynthetic congeners of brassinolide, such as cathasterone, teasterone, 3-dehydroteasterone, typhasterol and castasterone as well as another series of 6-deoxoteasterone, 3-dehydro-6-deoxoteasterone, 6-deoxotyphasterol and 6-deoxocastasterone. Using cell culture system of Catharanthus roseus , the outlines of biosynthetic pathways of brassinolide, via plant sterol of campesterol, have now been demonstrated. There are two pathways, named early C6-oxidation pathway and late C6-oxidation pathway, both of which would be operating in wide varieties of plants. Metabolic studies with various plant systems revealed multiple paths of metabolism such as hydroxylation, epimerization, side chain cleavage, reduction and conjugation with glucose and fatty acids. Recent progress of biosynthesis and metabolism of brassinosteroids is described. 相似文献
849.
Nine analogues of the opioid pentapeptides leucine-/ methionine-enkephalinamide, involving replacement of amino acid at position
5 or amino acids at positions 2 and 5, have been synthesized by the solid phase method using mainly 9-fluorenylmethyloxycarbonyl
amino acid trichlorophenyl esters in the presence of 1-hydroxybenzotriazole, the solid support being the Merrifield resin.
All the analogues were effective in inhibiting the electri cally stimulated contractions of the guinea pig ileum (in vitro) and one of them, tyrosyl-Dnorvalyl-glycyl-phenylalanyl-methioninamide was found to be about 82 times more active than morphine.
They also exhibited analgesic activity as well as antidiarrhoeal activity in mice (in vivo).
Presented at the 3rd National Symposium on Bioorganic Chemistry, 1987, Hyderabad. 相似文献
850.
Rositsa Zamfirova Nikola Pavlov Petar Todorov Polina Mateeva Jean Martinez Monique Calmès Emilia Naydenova 《Bioorganic & medicinal chemistry letters》2013,23(14):4052-4055
We report the synthesis and the biological activity of new analogues of Ac-RFMWMK-NH2 and Ac-RYYRWK-NH2, modified in position 4 and 5, respectively, with incorporation of newly synthesized β2-tryptophan analogues. Trp was substituted by the (S)-2-(1-methyl-1H-indol-3-yl)propionic residue or by (S)-2-(5-methoxy-1H-indol-3-yl)propionic residue. The biological activity (pEC50 and Emax) of these compounds was tested on electrically stimulated preparations of rat vas deferens. The 5-methoxy β-tryptophan group reverses the affinity of the compounds. 相似文献