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1.
In a variety of tumour systems, individuals carrying progressively growing neoplasms have lymphoid cells with a specific cytotoxic effect on cultured tumour cells from the same individual1–4. Since the sera of tumour-bearing individuals have been shown to prevent tumour cell destruction by immune lymphocytes in vitro2,5–8 and since this serum blocking activity appears early in primary and transplant tumour development5,7, it has been suggested that the appearance of this serum blocking activity might be responsible for the progressive growth of tumours in individuals having cytotoxic lymphocytes. Counteraction of this blocking activity would thus be of primary importance in facilitating the function of an already existing or bolstered cell-mediated immunity. The serum blocking activity might be inhibited in various ways, by preventing the formation of blocking antibody or by interfering with its action (“unblocking”), as demonstrated in Moloney sarcoma regressor sera9. This type of serum also has a therapeutic effect on Moloney sarcomas in vivo10,11, which has been tentatively attributed to its unblocking activity8,9 or, possibly, to a complement-dependent cytotoxicity10. Tumour growth in the Moloney sarcoma system, however, might be due in part to continuous recruitment of neoplastic cells by virus-induced transformation and so the therapeutic effect could be due to a virus-neutralizing serum activity9,10. 相似文献
2.
On the mechanism of ATP-induced shape changes in the human erythrocyte membranes: the role of ATP 下载免费PDF全文
In the preceding paper (Sheetz, M. and S.J. Singer. 1977. J Cell Biol. 73:638-646) it was shown that erythrocyte ghosts undergo pronounced shape changes in the presence of mg-ATP. The biochemical effects of the action of ATP are herein examined. The biochemical effects of the action of ATP are herein examined. Phosphorylation by ATP of spectrin component 2 of the erythrocyte membrane is known to occur. We have shown that it is only membrane protein that is significantly phosphorylated under the conditions where the shape changes are produced. The extent of this phosphorylation rises with increasing ATP concentration, reaching nearly 1 mol phosphoryle group per mole of component 2 at 8mM ATP. Most of this phosphorylation appears to occur at a single site on the protein molecule, according to cyanogen bromide peptide cleavage experiments. The degree of phosphorylation of component 2 is apparently also regulated by a membrane-bound protein phosphatase. This activity can be demonstrated in erythrocyte ghosts prepared from intact cells prelabeled with [(32)P]phosphate. In addition to the phosphorylation of component 2, some phosphorylation of lipids, mainly of phosphatidylinositol, is also known to occur. The ghost shape changes are, however, shown to be correlated with the degree of phosphorylation of component 2. In such experiment, the incorporation of exogenous phosphatases into ghosts reversed the shape changes produced by ATP, or by the membrane-intercalating drug chlorpromazine. The results obtained in this and the preceding paper are consistent with the proposal that the erythrocyte membrane possesses kinase and phosphates activities which produce phosphorylation and dephosphorylation of a specific site on spectrin component 2 molecules; the steady-state level of this phosphorylation regulates the structural state of the spectrin complex on the cytoplasmic surface of the membrane, which in turn exerts an important control on the shape of the cell. 相似文献
3.
The binding of pyridoxal 5'-phosphate to human serum albumin 总被引:1,自引:0,他引:1
Most of the pyridoxal 5'-phosphate (PLP) in plasma is bound to protein, primarily albumin. Binding to protein is probably important in transporting PLP in the circulation and in regulating its metabolism. The binding of PLP to human serum albumin (HSA) was studied using absorption spectral analysis, equilibrium dialysis, and inhibition studies. The kinetics of the changes in the spectrum of PLP when mixed with an equimolar concentration of HSA at pH 7.4 followed a model for two-step consecutive binding with rate constants of 7.72 mM-1 min-1 and 0.088 min-1. The resulting PLP-HSA complex had absorption peaks at 338 and 414 nm and was reduced by potassium borohydride. The 414-nm peak is probably due to a protonated aldimine formed between PLP and HSA. The binding of PLP to bovine serum albumin (BSA) at equimolar concentrations at pH 7.4 occurred at about 10% the rate of its binding to HSA. The final PLP-BSA complex absorbed maximally at 334 nm and did not appear to be reduced with borohydride. Equilibrium dialysis of PLP and HSA indicated that there were more than one class of binding sites of HSA for PLP. There was one high affinity site with a dissociation constant of 8.7 microM and two or more other sites with dissociation constants of 90 microM or greater. PLP binding to HSA was inhibited by pyridoxal and 4-pyridoxic acid. It was not inhibited appreciably by inorganic phosphate or phosphorylated compounds. The binding of PLP to BSA was inhibited more than its binding to HSA by several compounds containing anionic groups. It is concluded that PLP binds differently to HSA than it does to BSA. 相似文献
4.
Phenylglyoxal reacts much more rapidly with N2-acetylarginine than with either N2-acetyllysine or N-acetylcysteine. The rate of the reaction of phenylglyoxal with either N-acetylarginine or arginine increases with increasing pH from 7.5 to 11.5. The model reaction with arginine is much faster in bicarbonate, diethylamine, or triethylamine buffer than in N-ethylmorpholine, borate, phosphate, or Tris buffer. This activation by various buffers should be taken into consideration when glyoxal derivatives are used to modify arginyl residues. 相似文献
5.
F Sicuteri E Del Bene C Fonda 《Bollettino della Società italiana di biologia sperimentale》1975,51(17):1031-1036
The sexual function in man can be modified decreasing brain serotonin by PCPA and increasing brain cathecolamines by monoamineoxidase inhibitors. In 5 volunteers, sexual deficient men, the combination of PCPA with phenelzine (IMAO) stressed an increase in sexual stimulation, measured by number of erections. In two subjects this effect lasted for 2 months. A clear improvement in mood has also been shown. This pharmacological combination opens new and interesting possibilities in sexual deficiency treatment. 相似文献
6.
Gold salts and phenylbutazone selectively inhibit the synthesis of PGF2α and PGE2 respectively. Lowered production of one prostaglandin species is accompanied by an increased production of the other. Selective inhibition by these drugs was observed in the presence of adrenaline, reduced glutathione and copper sulphate under conditions when most anti-inflammatory compounds inhibited PGE2 and PGF2α syntheses equally. It is postulated that selective inhibitors may have a different mode of action
and beneficial effects may be related to the endogenous ratio of PGE to PGF required for normal function. 相似文献
7.
Whole-body cryotherapy (WBC) involves exposing minimally dressed participants to very cold air (injecting liquid nitrogen with temperature −195 °C), either in a specially designed chamber (cryo-chamber) or cabin (cryo-cabin), for a short period of time. The aim of this study was to examine the actual temperature of the air in the cryo-cabin at different locations throughout the cabin by using human subjects and a manikin. Additionally, we monitored skin temperature before and for 60 min after the cryo-cabin session. Twelve subjects completed one 3 min cryo-cabin session. Temperature next to the skin was assessed during the session, while the skin temperature was monitored before, 3 min after and every 10 min for 60 min after completing the session. There was a statistically significant interaction (time×position) for temperature among the different body parts during the WBC, and for skin temperature among different body parts after the cryo-cabin session. Statistically significant time effects during and following cryo-cabin session were present for all body parts. We showed that actual temperature in the cryo-cabin is substantially different from the one reported by the manufacturer. Thermal response after cryo-cabin session is similar to response observed after cryo-chamber cold exposure reported in previously published studies. This could be of great practical value as cryo-cabins are less expensive and easier to use compared to cryo-chambers. 相似文献
8.
9.
Reversible oxidative modification as a mechanism for regulating retroviral protease dimerization and activation 下载免费PDF全文
Davis DA Brown CA Newcomb FM Boja ES Fales HM Kaufman J Stahl SJ Wingfield P Yarchoan R 《Journal of virology》2003,77(5):3319-3325
Human immunodeficiency virus protease activity can be regulated by reversible oxidation of a sulfur-containing amino acid at the dimer interface. We show here that oxidation of this amino acid in human immunodeficiency virus type 1 protease prevents dimer formation. Moreover, we show that human T-cell leukemia virus type 1 protease can be similarly regulated through reversible glutathionylation of its two conserved cysteine residues. Based on the known three-dimensional structures and multiple sequence alignments of retroviral proteases, it is predicted that the majority of retroviral proteases have sulfur-containing amino acids at the dimer interface. The regulation of protease activity by the modification of a sulfur-containing amino acid at the dimer interface may be a conserved mechanism among the majority of retroviruses. 相似文献
10.
Cerveza PJ Mehrbod F Cotton SJ Lomeli N Linder MC Fonda EG Wickler SJ 《Archives of biochemistry and biophysics》2000,373(2):451-461
Concentrations of ceruloplasmin and copper in milk and blood plasma, the nature of milk ceruloplasmin, and the effects of lactation and gestation on these parameters, as well as the expression of ceruloplasmin mRNA by the mammary gland, were examined in pigs. As seen previously in humans, ceruloplasmin and copper concentrations in sow milk were much higher a few days after birth than 1 month later, averaging 26.5 and 6.6 mg ceruloplasmin/L (by immunoassay) and 1.67 and 0.34 mg total Cu/L, on days 3 and 33 postpartum, respectively. Values for ceruloplasmin oxidase activity (measured with p-phenylene diamine) were 7.8 and 1.3 nmol/min/L, respectively. Daily milk ceruloplasmin production went from 61 to 22 mg/day and daily copper output from 38 to 12 mg/day. In contrast, there was little or no variation in serum ceruloplasmin concentration during lactation or gestation, although total plasma copper was high at the end of gestation. Milk ceruloplasmin was of the same apparent size as serum ceruloplasmin, as determined by SDS-PAGE and immunoblotting, and ceruloplasmin mRNAs of liver and mammary gland were indistinguishable by Northern analysis and RT-PCR of the various exons. Expression of total RNA and ceruloplasmin mRNA, as detected in biopsies of mammary gland, increased markedly upon onset of lactation and then declined during the next month in conjunction with a drop in milk ceruloplasmin production. The results indicate that milk ceruloplasmin, while being the same protein as in plasma, is not derived from the plasma but is produced by the mammary gland. 相似文献