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排序方式: 共有190条查询结果,搜索用时 513 毫秒
61.
Polyene antibiotic amphotericin B in monomolecular layers: spectrophotometric and scanning force microscopic analysis 总被引:3,自引:0,他引:3
The effect of cytokines on the taurine uptake by human intestinal epithelial Caco-2 cells was investigated. Among the various cytokines tested, tumor necrosis factor alpha (TNF-alpha) markedly increased the taurine uptake by Caco-2 cells, resulting in an increase in the intracellular taurine level. TNF-alpha did not induce up-regulation of the taurine uptake in hepatic HepG2, renal human embryo kidney 293, and macrophage-like THP-1 cells. The uptake of glycine, L-leucine, and L-glutamic acid by Caco-2 cells was not affected by TNF-alpha. A kinetic analysis of the taurine uptake by TNF-alpha-treated Caco-2 cells suggests that this up-regulation was associated with both an increase in the amount of the taurine transporter (TAUT) and an increase in its affinity. TNF-alpha-treated cells showed a higher mRNA level of the TAUT than did the control cells. 相似文献
62.
Flexible transfer lines or mixed-model assembly lines are capable of diversified small-lot production due to negligible switch-over costs. With these lines, it is possible to implement just-in-time (JIT) production, which involves producing only the necessary parts in the necessary quantities at the necessary times. The problem of sequencing flexible transfer lines according to the JIT philosophy can be formulated as a nonlinear integer programming problem. Heuristic algorithms to solve the problem have appeared in the literature. In this paper, we show that the problem can be explicitly reduced to an assignment problem. Thus, we provide an efficient algorithm for an optimal solution to the JIT sequencing problem. 相似文献
63.
Maurice Manning Ling Ling Cheng Stoytcho Stoev Wieslaw A. Klis Eleonora Nawrocka Aleksandra Olma Wilbur H. Sawyer Nga Ching Wo W. Y. Chan 《Journal of peptide science》1997,3(1):31-46
We report the solid-phase synthesis and some pharmacological properties of 12 position three modified analogues (peptides 1–12) of the potent non-selective antagonist of the antidiuretic (V2-receptor), vasopressor (V1a-receptor) responses to arginine vasopressin (AVP) and of the uterine contracting (OT-receptor) responses to oxytocin (OT), [1(-β mercapto-β,β-pentamethy lenepropionic acid)-2-O-ethyl-d -tyrosine 4-valine] arginine vasopressin [d(CH2)5D -Tyr(Et) 2VAVP] (A) and two analogues of ( B ) (peptides 13,14), the 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid3 (Tic3) analogue of ( A ). Peptides 1–12 have the following substituents at position three in ( A ): (1) Pro; (2) Oic; (3) Atc; (4) D -Atc; (5) Aic; (6) D -Phe; (7) Ile; (8) Leu; (9) Tyr; (10) Trp; (11) Hphe; (12) [HO]Tic; Peptide (13) is the Tyr-NH2 9 analogue of ( B ): Peptide (14) is the D -Cys 6 analogue of ( B ). All 14 new peptides were evaluated for agonistic and antagonistic activities in in vivo V2 and V1a assays and in in vitro (no Mg2+) n oxytocic assays. With the exception of the D -Phe3 peptide (No. 6), which exhibits very weak V2 agonism (…0.0017 u/mg), none of the remaining 13 peptides exhibit any agonistic activities in these assays. In striking contrast to their deleterious effects on agonistic activities in AVP, the Pro3, Oic3, Tyr3, Trp3 and Hphe3 substitutions in ( A ) are very well tolerated, leading to excellent retention of V2, V1a and OT antagonistic potencies. All are more potent as V2 antagonists than the Ile3 and Leu3 analogues of ( A ). The Tyr-NH29 and D -Cys6 substitutions in ( B ) are also well tolerated. The anti-V2 pA2 values of peptides 1–5 and 7–14 are as follows (1) 7.77±0.03; (2) 7.41± 0.05; (3) 6.86±0.02; (4) 5.66±0.09; (5) …5.2; (7) 7.25± 0.08; (8) 6.82±0.06; (9) 7.58±0.05; (10) 7.61±0.08; (11) 7.59±0.07; (12) 7.20±0.05; (13) 7.57±0.1; (14) 7.52± 0.06. All analogues antagonize the vasopressor responses to AVP, with anti-V 1a pA2 values ranging from 5.62 to 7.64, and the in vitro responses to OT, with anti-OT pA2 values ranging from 5.79 to 7.94. With an anti-V2 potency of 7.77±0.03, the Pro3 analogue of ( A ) is surprisingly equipotent with ( A ), (anti-V2 pA2=7.81±0.07). These findings clearly indicate that position three in AVP V2/V1a antagonists, in contrast to position three in AVP agonists, is much more amenable to structural modification than had heretofore been anticipated. Furthermore, the surprising retention of V2 antagonism exhibited by the Pro3, Oic3, Tyr3, Trp3 and Hphe3 analogues of ( A ), together with the excellent retention of V2 antagonism by the Tyr-NH29 and D -Cys6 analogues of ( B ) are promising new leads to the design of potent and possibly orally active V2 antagonists for use as pharmacological tools and/or as radioiodinatable ligands and for development as potential therapeutic agents for the treatment of the hyponatremia caused by the syndrome of the inappropriate secretion of the antidiuretic hormone (SIADH). © 1997 European Peptide Society and John Wiley & Sons, Ltd. 相似文献
64.
Structure of a lactic acid ether-containing and glycerol phosphate-containing O-polysaccharide from Proteus mirabilis O40 总被引:1,自引:0,他引:1
Kondakova AN Fudala R Senchenkova SN Shashkov AS Knirel YA Kaca W 《Carbohydrate research》2005,340(9):1612-1617
An O-polysaccharide was isolated by mild acid hydrolysis from the lipopolysaccharide of Proteus mirabilis O40 and studied by NMR spectroscopy, including 2D 1H, 1H COSY, TOCSY, ROESY, and 1H, 13C HMQC experiments, along with chemical methods. The polysaccharide was found to contain an ether of GlcNAc with lactic acid and glycerol phosphate in the main chain and to have the following structure: --> 3)-beta-D-GlcpNAc4(R-Lac)-(1 --> 3)-alpha-D-Galp-(1 --> 3)-D-Gro-1-P-(O --> 3)-beta-D-GlcpNAc-(1 --> where D-GlcpNAc4(R-Lac) stands for 2-acetamido-4-O-[(R)-1-carboxyethyl]-2-deoxy-D-glucose. This structure is unique among the known structures of the Proteus O-polysaccharides, which is in agreement with the classification of the strain studied into a separate O-serogroup. A serological relatedness of P. mirabilis O40 with some other Proteus strains was revealed and discussed in view of the O-polysaccharide structures. 相似文献
65.
Olek RA Ziolkowski W Kaczor JJ Greci L Popinigis J Antosiewicz J 《Journal of biochemistry and molecular biology》2004,37(4):416-421
The antioxidant activities of NADH and of its analogue, 1,4-dihydro-2,6-dimethyl-3,5-dicarbethoxy-pyridine (PyH(2)), were evaluated in vitro. NADH was found to be oxidized by the peroxyl radical derived from 2,2-azobis-(2-amidinopropane) dihydrochloride (AAPH) decomposition, in a pH-dependent manner. Both NADH and PyH(2) inhibited the peroxidation of egg yolk lecithin (EYL) liposomes, although PyH(2) was more effective than NADH when 2,2'-azobis-4-methoxy-2,4-dimethyl-valeronitrile (methoxy-AMVN) was employed to induce EYL liposome peroxidation. The antioxidant activities of NADH and PyH(2) were also evaluated by measuring their influences on 1,3-diphenylisobenzofuran (DPBF) fluorescence decay in the presence of peroxyl radicals. NADH and PyH(2) were much more effective at inhibiting DPBF quenching in Triton X-100 micelles than in liposomes. These results indicate that NADH can inhibit lipid peroxidation despite being hydrophilic. Nevertheless, membrane penetration is an important factor and limits its antioxidant activity. 相似文献
66.
67.
Li X Zhang S Zhang YK Liu Y Ding CZ Zhou Y Plattner JJ Baker SJ Bu W Liu L Kazmierski WM Duan M Grimes RM Wright LL Smith GK Jarvest RL Ji JJ Cooper JP Tallant MD Crosby RM Creech K Ni ZJ Zou W Wright J 《Bioorganic & medicinal chemistry letters》2011,21(7):2048-2054
We have synthesized and evaluated a new series of acyclic P4-benzoxaborole-based HCV NS3 protease inhibitors. Structure-activity relationships were investigated, leading to the identification of compounds 5g and 17 with low nanomolar potency in the enzymatic and cell-based replicon assay. The linker-truncated compound 5j was found to exhibit improved absorption and oral bioavailability in rats, suggesting that further reduction of molecular weight and polar surface area could result in improved drug-like properties of this novel series. 相似文献
68.
Wieslaw A. Kliś Eleonora Nawrocka Ignacy Z. Siemion Andrzej Plech Zdzisław Stachura Zbigniew S. Herman 《Bioorganic chemistry》1979,8(2):255-262
Two analogs of Leu5-enkephalin, (1-O-methyltyrosine,5-leucine)-enkephalin and [1-(3′-amino)-tyrosine,5-leucine]-enkephalin, were synthesized by classical methods. Both analogs show high biological potency after injection into the lateral brain ventricle of the rat. In both cases substitution of the Tyr residue of enkephalin leads to a pronounced prolongation of analgesic action, as compared with the unsubstituted peptide. 相似文献
69.
Bożena Pawlikowska-Pawlęga Lucjan E. Misiak Anna Jarosz-Wilkołazka Barbara Zarzyka Roman Paduch Antoni Gawron Wieslaw I. Gruszecki 《生物化学与生物物理学报:生物膜》2014
With application of EPR and 1H NMR techniques genistein interaction with liposomes formed with egg yolk lecithin and with erythrocyte membranes was assessed. The present study addressed the problem of genistein localization and its effects on lipid membrane fluidity and protein conformation. The range of microscopic techniques was employed to study genistein effects on HeLa cells and human erythrocytes. Moreover, DPPH bioassay, superoxide anion radical test and enzymatic measurements were performed in HeLa cells subjected to genistein. The gathered results from both EPR and NMR techniques indicated strong ordering effect of genistein on the motional freedom of lipids in the head group region and the adjacent hydrophobic zone in liposomal as well as in red blood cell membranes. EPR study of human ghost showed also the changes in the erythrocyte membrane protein conformation. The membrane effects of genistein were correlated with the changes in internal membranes arrangement of HeLa cells as it was noticed using transmission electron microscopic and fluorescent techniques. Scanning electron and light microscopy methods showed that one of the aftermaths of genistein incorporation into membranes was creation of echinocytic form of the red blood cells with reduced diameter. Genistein improved redox status of HeLa cells treated with H2O2 by lowering radicals' level. 相似文献
70.
Małgorzata Kikowska Barbara Thiem Elwira Sliwinska Monika Rewers Mariusz Kowalczyk Anna Stochmal Wiesław Oleszek 《Journal of Plant Growth Regulation》2014,33(4):809-819
Eryngium maritimum L. is a valuable medicinal species, but since it is protected plant, collection from natural populations is forbidden. Therefore, establishing an efficient system for micropropagation of this species is desirable. To determine the optimal nutritional factors needed for shoot multiplication, root development and secondary metabolites accumulation, different media and plant growth regulators were tested. The highest plant regeneration efficiency (over 96 %), with 4.4 shoots per explant was induced on Murashige and Skoog (MS) medium supplemented with 1.0 mg L?1 benzyladenine (BA) and 0.1 mg L?1 indole-3-acetic acid (IAA). The in vitro-regenerated shoots were rooted (83.3–100 %) and transferred to an experimental plot with 62 % efficiency. Flow cytometric analysis revealed no variation in nuclear DNA content in field- and in vitro-delivered plant material. Ultra high performance liquid chromatography (UHPLC) indicated that multiple shoots and roots from in vitro-regenerated plantlets and adventitious root cultures maintained the production of rosmarinic (RA) and chlorogenic (CGA) acids and triterpenoid saponins found in the rosette leaves and roots of E. maritimum intact plants. UHPLC revealed a 12-fold increase of RA and CGA and 3.2-fold higher accumulation of triterpenoid saponins in roots of in vitro-derived plantlets in comparison to roots from field-grown plants. Adventitious root cultures allowed continuous growth of excised root in liquid media with or without exogenous auxins. The roots grown in liquid medium supplemented with 0.1 mg L?1 IAA showed higher (227-fold) phenolic acids accumulation than those without auxin. Obtained results confirmed that micropropagation is a useful strategy in the protection of endangered species and a renewable source of a high quality plant material for secondary metabolites production. 相似文献