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91.
Kinetic investigation of the interaction of cibacron blue F3G-A with phosphofructokinase from yeast.
H J B?hme R Freyer P Retterrath W Schellenberger E Hofmann 《Acta biologica et medica Germanica》1978,37(1):173-177
Yeast phosphofructokinase is strongly inhibited by Cibacron Blue F3G-A. The inhibition is competitive in respect to the phosphate donor. Fructose 6-phosphate and ATP are able to abolish the dye-inhibition. Replacement of the strong inhibitor ATP by ITP as phosphate donor gives qualitatively analogous effects. The influence of Cibacron Blue F3G-A on the kinetic pattern of yeast phosphofructokinase can be described in terms of the kinetic model of Freyer et al. [8] if one assumes that the dye binds to the ATP-binding sites in a competitive manner. 相似文献
92.
The dynamic properties of a series of in vitro reaction systems with increasing complexity and containing phosphofructokinase as central enzyme have been investigated. An experimental strategy and a principal mathematical treatment was elaborated to search for the minimum requirements with respect to the enzyme composition of a reaction system for generating limit cycle behaviour. As a criterion, such models have been developed which permit experimental realization by application of a specially designed flow-through equipment. In addition to phosphofructokinase, the following enzymes have been stepwise included into the reaction systems composing the Models 1 through 6: pyruvate kinase, adenylate kinase, hexokinase, and glucose 6-phosphate isomerase. It turned out that only a minimum dynamic system containing phosphofructokinase and pyruvate kinase as well as excesses of adenylate kinase and glucose 6-phosphate isomerase for maintaining equilibrium conditions between the respective reacting species, acquires the property of limit cycle behaviour and, hence, to generate sustained self-oscillations. The approach permits to compute the region of the experimentally variable parameters (influx rates of fructose 6-phosphate and ATP, maximum rate of pyruvate kianse) for which self-oscillatory behaviour can be predicted. 相似文献
93.
The digestion of a human IgG1 K myeloma protein with pepsin in the presence of 8M-urea was observed to produce a fragment, designated Fb'2, which differed from the products of aqueous peptic digestion and from other characteristic immunoglobulin digestion products. 2. Fragment Fb's was also found when two other IgG1/K proteins were treated similarly. 3. Sedimentation-equilibrium studies showed the mol.wt. of fragment Fb'2 to be 56800. 4. On reduction, two equivalents of each of three peptides were released from fragment Fb's; these were characterized by N- and C-terminal determinations and by amino acid sequencing. 5. Fragment Fb'2 was shown to consist of the constant regions of both light chains, from residue Ile-117 to the C-terminus, and the CH1 domains and hinge region of the heavy chains, from residue Val-113 to residue Met-252, with a gap of five residues within the intrachain disulphide loop, between residues Leu-174 and Tyr-180. 相似文献
94.
Phosphofructokinase has been purified from pig kidney by extraction with phosphate buffer at pH 8, followed by alcohol treatment, affinity chromatography on matrix-bound Cibacron blue F3G-A, and gel chromatography on Sepharose 6B. Using sodium dodecyl sulphate electrophoresis the enzyme was found to be homogeneous and to have a specific activity of about 80 units/mg protein. Like other phosphofructokinases, at pH 7.0 the enzyme exhibits a sigmoidal dependence in its activity on the fructose 6-phosphate concentration and is strongly inhibited by ATP. The degree of citrate inhibition is influenced by the concentration of the two substrates. ATP strengthens and fructose 6-phosphate relieves the inhibition by citrate. AMP and cAMP are able to overcome the ATP inhibition. The ADP activation curve is biphasic. The molecular weight of the subunit of pig kidney phosphofructokinase was determined to be 88 000 by means of sodium dodecyl sulphate electrophoresis. 相似文献
95.
Gerhard Kopperschläger Elke Usbeck Eberhard Hofmann 《Biochemical and biophysical research communications》1976,71(1):371-378
Intracellular cross-linking of yeast phosphofructokinase with a series of diimidoesters of different chain length resulted in the appearance of tetramers as largest cross-linked product of the enzyme subunits. The native enzyme is evidently composed of eight subunits being arranged in two tetramers α4β4. In the tetramers the monomers are probably assembled in tetrahedral geometry. 相似文献
96.
97.
K W Wenzel B I Kurganov G Zimmermann V A Yakovlev W Schellenberger E Hofmann 《European journal of biochemistry》1976,61(1):181-190
The kinetic behaviour of human erythrocyte phosphofructokinase has been analyzed over a relative wide range of enzyme concentration (0.01 -- 1.7 mug/ml). The kinetic cooperativity which becomes apparent when the enzymic reaction rate is plotted versus the fructose 6-phosphate concentration decreases with increasing enzyme concentration. Simultaneously, a decrease of the half-saturation concentration for fructose 6-phosphate [S]0.5 is observed. Maximum velocity passes through a maximum at increasing enzyme concentrations. Sets of curves representing specific enzymic activity of phosphofructokinase versus enzyme concentration obtained at various fixed concentrations of fructose 6-phosphate and ATP are analyzed. The shapes of these curves are interpreted in terms of an association model of human erythrocyte phosphofructokinase, in which an inactive dimer (Mr 190000) and active multimers of the dimeric form are involved. The conclusion is drawn that the sigmoidal shape of the plots of the enzymic reaction rate versus fructose 6-phosphate concentration is partially caused by a displacement of the equilibrium between different states of association of phosphofructokinase to multimers by this substrate. On the other hand, the inhibition of the enzyme by high concentrations of ATP may be partially caused by a shift of this equilibrium to the state of the inactive dimer. 相似文献
98.
I C McDonald D E Overland R A Leopold M E Degrugillier P B Morgan H C Hofmann 《The Journal of heredity》1975,66(3):137-140
Genetic data were used to compare the structure of native house fly populations collected in North Dakota, Texas, and Florida. Recombination studies with mutant markers on chromosomes 3 and 4 indicated a lack of inversion polymorphism among the three populations in those areas of the genetic map studied. Significant differences were observed among flies from the three regions with regard to the frequency of 1) females that produced only male progeny, and 2) male-determining 3rd chromosomes (IIIm chromosomes). However, the North Dakota and Texas flies were more similar to each other than to the Florida flies since populations from the two former areas possessed a low frequency of both male-producing females and IIIm chromosomes; in contrast, the Florida population was void of females that produced males only and a high percentage if not all Florida males appeared to possess the IIIm male-determining mechanism. Tests for recessive lethal 3rd chromosomes showed that there was no significant difference in the frequency of lethal factors recovered from the North Dakota and Texas flies; the presence of IIIm chromosomes in Florida males precluded the recovery of lethal factors from this population by the method employed. The data suggest that house fly strains to be employed in genetic control programs should 1) originate from target control areas to avoid possible behavioral differences existing among flies from different locales, 2) be initiated with as many flies as possible to provide a background for the maintenance of variability, and 3) be renewed periodically with field-collected material since the genotype may be capable of rapid reorganization in response to laboratory selection pressures. 相似文献
99.
Acyl intermediates in penicillopepsin-catalysed reactions and a discussion of the mechanism of action of pepsins. 下载免费PDF全文
Penicillopepsin catalyses transpeptidation reactions involving the transfer of the N-terminal amino acids of suitable substrates via covalent acyl intermediates to acceptor peptides, usually the substrate. The major products obtained when Phe-Tyr-Thr-Pro-Lys-Ala and Met-Leu-Gly were used as substrates were Phe-Phe and Met-Met respectively. With Met-Leu-Gly the tetrapeptide Met-Met-Leu-Gly was observed as probable intermediate. Co-incubation of Leu-Tyr-Leu and Phe-Tyr-Thr-Pro-Lys-Ala led to the formation of Leu-Phe and Phe-Leu as well as Leu-Leu and Phe-Phe. No reaction was observed with tripeptides in which the first or second amino acid is glycine. It appears that two amino aicds with large hydrophobic residues are needed for the transpeptidation reaction. Nucleophilic compounds other than peptides, such as hydroxylamine, aliphatic alcohols and dinitrophenylhydrazine, were not acceptors for the acyl group. Leucine, phenylalanine and leucine methyl ester also had no effect on the reaction. The transpeptidation reaction proceeded readily at pH 3.6 and 4.7. At pH 6.0 the reaction was slow and at pH 1.9 little or no transpeptidation was observed. Porcine pepsin catalyses similar transpeptidation reactions. Sequence studies show that porcine pepsin and penicillopepsin are homologous. The present study also suggests that they have a very similar mechanism. Evidence available at this time indicates that the mechanism of these enzymes is complex and may be modulated by secondary substrate-enzyme interactions. A hypothesis is presented which proposes that pepsin-catalysed reactions proceed via different covalent intermediates (amino-intermediates or acylintermediates) depending on the nature of the substrate. The possibility that some reactions do not involve covalent intermediates is also discussed. 相似文献
100.
R E Merchant M C Moreillon S Arrenbrecht V Hofmann 《International journal of cell cloning》1985,3(3):156-168
We examined cellular relationships and cytokinetics of hairy cells in colonies formed in an in vitro cloning system. Cells in small colonies and at the periphery of larger ones were separated by wide, irregular intercellular spaces. Cells in the core of large colonies were elaborately intertwined by their cytoplasmic processes and so densely packed that their intercellularity was greatly reduced. Cell labeling with 3H-thymidine revealed indices ranging from less than 1% to 35%. The combination of autoradiography with a stain for tartrate-resistant acid phosphatase showed that the enzyme was not expressed by cells in S-phase. The cellular relationships of hairy cells in colonies grown in this system closely mimic those of their in vivo counterparts in the spleen and bone marrow. 相似文献