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1.
The metabolism of pregnenolone in subcellular fractions of the testes of the macaque (Macaca fascicularis) has been studied using capillary gas chromatography to characterize and quantify the metabolites, after their conversion into the O-methyloxime and/or trimethylsilyl ether derivatives. The microsomal incubations yielded the greatest quantities of metabolites, with lesser amounts in the mitochondrial fraction. The cytosolic fraction contained no significant quantity of metabolites after incubation, except for 5alpha-androst-16-en-3 beta-ol. This, and other odorous androst-16-enes, found in the microsomal fraction, are of particular interest in the context of animal communication because of their possible pheromonal role. Pregnenolone was converted into androst-5-ene-3 beta,17 beta-diol, androst-4-ene-3,17-dione and testosterone, suggesting that both classical pathways for testosterone synthesis were operating. Testosterone was further converted into 5 alpha-reduced androstanediols, especially in the microsomal fraction. 相似文献
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Nuclear Overhauser effect and computational characterization of the beta-spiral of the polypentapeptide of elastin 总被引:1,自引:0,他引:1
D K Chang C M Venkatachalam K U Prasad D W Urry 《Journal of biomolecular structure & dynamics》1989,6(5):851-858
The structure of the elastin polypentapeptide, poly(VPGVG), was studied by nuclear Overhauser effect experiments using perdeuterated Val1 and Val4 samples under the condition where intermolecular interactions are absent. More extensive interaction was found between the Val1 gamma CH and Pro2 beta CH protons than between the Val4 gamma CH and Pro2 beta CH protons. The Val1 gamma CH3-Pro2 beta CH interaction does not occur within the same pentamer as previously shown experimentally and as expected from steric considerations. The results are incompatible with the presence of a random chain network in poly(VPGVG) at room temperature but are readily explicable in terms of interturn interactions in a beta-spiral structure. More specifically, the results indicate that the beta-spiral conformation with 2.9 pentamers/turn is more prevalent than that with 2.7 pentamers/turn. Using conformations developed by molecular mechanics calculations, molecular dynamics simulations were carried out to compare the relative energies of these two variants of this class of beta-spiral structures. It was found in vacuo that the structure with 2.9 pentamers/turn is indeed more stable than that of 2.7 pentamers/turn by approximately 1 kcal/mole-pentamer. 相似文献
4.
The polyamines stimulated tyrosine hydroxylase in whole homogenates of bovine caudate nuclei approximately 2 fold. TheV
max forl-tyrosine increased by 2.3 fold while theK
m
s forl-tyrosine and for the cofactor (DMPH4) were unchanged.l-Aromatic amino acid decarboxylase from whole rat brain homogenate was stimulated by about 40% in the presence of polyamines. These findings suggest that increased polyamine levels associated with increased cellular synthetic activity can modify the synthesis of neurotransmitters. 相似文献
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Abstract— It has been reported that myelin basic protein (MBP) forms a specific complex with S-100 protein in the presence of either Ca2+ or Mn2+, as detected by Immunoelectrophoresis. We have now studied the binding of Ca2+ and Mn2+ to these two proteins. We find that MBP binds 1 mol of Mn2+/mol of protein, and this binding produces an increment in its fluorescence, indicating a conformational change. Ca2+ does not bind to MBP nor does it affect the fluorescence of MBP. S-100 protein, as has been reported, binds about 10 mol of Ca2+/mol and this binding produces a conformational change. S-100 protein also has 25 binding sites for Mn2+, but this binding does not alter fluorescence and does not appear to affect conformation. Competitive binding experiments demonstrate that the binding sites of S-100 protein for Ca2+ and Mn2+ are independent. The alteration of electrophoretic migration in gels of S-100 protein produced by Ca2+ and of MBP produced by Mn2+ are in accord with the observations based on fluorescence. Mn2+ does not affect the electrophoretic mobility of S-100. These results indicate that the formation of the complex between MBP and S-100 protein in the presence of either Ca2+ or Mn2+ is due to the conformational change induced by these ions in S-100 protein, MBP, or both. 相似文献
6.
Semi-empirical energy calculations for an internal Pro-Pro dimer are presented that take into account the nature of the flexibility of the proline ring due to its puckering. Calculations show that three stable conformations are available for the dimer: the cis (ω = 0°, ψ = 160°); the trans (ω = 180°, ψ = 160°, also referred to as trans′); and the cis′ (ω = 180°, ψ = ?40°) conformations. The best conformational pathways between these stable conformations are determined. Calculations also show that the barrier for cis′–trans′ conversion is of the same order of magnitude as that for cis–trans conversion. 相似文献
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Zhang Guanshi Zhang Jialing DeHoog Rachel J. Pennathur Subramaniam Anderton Christopher R. Venkatachalam Manjeri A. Alexandrov Theodore Eberlin Livia S. Sharma Kumar 《Metabolomics : Official journal of the Metabolomic Society》2020,16(1):1-12
Metabolomics - Food and dietary ingredients have significant effects on metabolism and health. To evaluate whether and how different diets affected the serum lipidomic profile of dogs. Sixteen... 相似文献
9.
Mandal Anup Mani Anjali Kottayil Lamech Ruban Anandajothi Elamaran Venkatachalam Shanmuga Arasu Dinakaran Gajendiran K. Quinitio Emilia T. Kandan Shanmuganathan 《Biochemical genetics》2021,59(4):856-869
Biochemical Genetics - Misleading identification and subsequent publications on biological, molecular, and aquaculture data of mangrove mud crab (genus Scylla de Hann 1833) is a major concern in... 相似文献
10.
Prakash Maran Jeganathan Sivakumar Venkatachalam Thirugnanasambandham Karichappan Sridar Ramasamy 《Preparative biochemistry & biotechnology》2013,43(1):56-67
The objective of the present study is to find out the optimum extraction conditions for extraction of polyphenols from red grapes using Box–Behnken design. Red grapes polyphenols were extracted using acid–ethanol solvent at various extraction temperature (40–60°C), extraction time (20–100 min) and different solid–liquid ratio (1:5–1:15 g:ml). The effect (main and interactive) of extraction conditions on total anthocyanin, phenolic and flavonoid content were studied using Box–Behnken design (three factors at three levels). The results showed that the contribution of the quadratic model was significant for all the responses. Second-order mathematical regression models were developed and were found to fit well with observed data. Derringer's desirability function methodology was performed to find out the optimal conditions based on both individual and combinations of all responses (extraction temperature: 57°C, time: 61 min, and solid–liquid ratio: 1:8.7 g:ml) were established. At this optimal condition, the anthocyanin yield, total phenolic and flavonoid content were 73.92 mg/100 g, 221.4 mg GAE/100 g, and 79.08 mg CE/100 g, respectively. A desirability value of 0.902 was achieved at this point. 相似文献