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671.
672.
In an effort to find out the mechanism(s) operative in enhancing the pathogenicity of E. histolytica in hosts under heat stress reported earlier, effect of 5-hydroxytryptamine (5-HT) on the virulence of the parasite was examined in just weaned Charles Foster strain of albino rats. Pathogenicity of 10 strains of E. histolytica, from various forms of intestinal amoebiasis, grown in modified Boeck and Drbohlav's medium was assessed by caecal scoring. Administration of 5-HT in infected animals significantly enhanced the pathogenicity of all the seven strains tested. Treatment of the host with the 5-HT precursor L-tryptophan also increased the caecal scores examined with three strains of E. histolytica. Prior blocking of tissue 5-HT receptors by administration of methysergide almost completely abolished the pathogenicity enhancing effect of 5-HT treatment. This suggested that 5-HT itself and not any of its metabolites was responsible for the observed increase in pathogenicity of E. histolytica on 5-HT treatment of the host. 相似文献
673.
674.
High-level expression of three members of the murine angiogenin family in Escherichia coli and purification of the recombinant proteins. 总被引:2,自引:0,他引:2
D E Holloway M C Hares R Shapiro V Subramanian K R Acharya 《Protein expression and purification》2001,22(2):307-317
Angiogenin (Ang) is a small basic protein which belongs to the pancreatic ribonuclease superfamily. It potently induces the formation of new blood vessels and has emerged as a promising anticancer target. Mice possess genes encoding one ortholog (mAng) and three homologs of Ang, designated angiogenin-related protein (mAngrp), angiogenin-3 (mAng-3), and angiogenin-4 (mAng-4). Structural and functional study of these homologs has been hampered by the low yield of protein from the existing heterologous expression system. In the experiments described, we used a pET expression vector to express these proteins in the cytoplasm of Escherichia coli BL21-CodonPlus(DE3)-RIL cells, whereupon substantial amounts of each accumulated in the form of insoluble aggregates. The proteins were renatured using an arginine-assisted procedure and subsequently purified by cation-exchange chromatography and reversed-phase HPLC; each purified protein was shown to be enzymatically active toward tRNA. The yields of pure mAngrp and mAng-3 were 7.6 and 12 mg/liter culture, respectively, representing substantial increases over previously reported experiments. This is also the first report of the expression and purification of mAng-4, obtained here in a yield of 30 mg/liter culture. The ready availability of milligram quantities of these proteins will enable further functional studies and high-resolution structural analyses to be conducted. 相似文献
675.
A S Acharya P J Vithayathil 《International journal of peptide and protein research》1975,7(3):207-219
The esterification of Ribonuclease-A in methanol/0.1 M hydrochloric acid has been studied by measuring the decrease in the number of titratable groups of the protein and estimating the amount of methanol incorporated. Esterification of nearly five of the 11 free carboxyl groups of the protein resulted in almost complete inactivation of the enzyme. The initial products of esterification have been chromatographed on Amberlite columns, and five partially active methyl ester derivatives of Ribonuclease-A have been isolated. The dimethyl ester, the initial product of esterification with reduced catalytic activity, has the carboxyl groups of Glu-49 and Asp-53 modified. Even in the non-aqueous solvent, as in the native structure of the protein in aqueous solution, these carboxyl groups are the fast reacting ones. Subsquently, the esterification reaction appears to proceed preferentially at the C-terminal region of the molecule. Comparison of the reactivities of carboxyl groups of Ribonuclease-A in acidic methanol to that known in aqueous solutions (with carbodiimides) suggests that the structure of Ribonuclease-A in the non-aqueous solvent resembles, at least in part, the structure in aqueous environment. 相似文献
676.
Fantao Meng Belur N. Manjula Amy G. Tsai Pedro Cabrales Marcos Intaglietta Paul K. Smith Muthuchidambaram Prabhakaran Seetharama A. Acharya 《The protein journal》2009,28(5):199-212
A new hexaPEGylated hemoglobin, (TCP-PEG5K)6-Hb (TCP, thiocarbamoyl phenyl) has been developed using PEG-phenyl-isothiocyanate and its vasoactivity and structure has
been investigated. Of the six PEG5K chains of (TCP-PEG5K)6-Hb, 4 are conjugated to the α-amino groups of Hb, and the other 2 chains are distributed on ε-amino groups, identified as
Lys-40(α) (~45%), Lys-56(α) (~25%), and Lys-8(β) (~24%). The studies with hamster infused with a bolus of a 4 gm % solution
of (TCP-PEG5K)6-Hb equivalent to 10% of their blood volume have established that this new hexaPEGylated Hb is vasoinactive. The viscosity
and the colloidal osmotic pressure of (TCP-PEG5K)6-Hb at 4% is 1.9 cP and 69.7 mmHg, respectively. The molecular radius of (TCP-PEG5K)6-Hb is about 4.6 nm and is significantly smaller than hexaPEGylated Hbs developed using other direct and extension arm facilitated
PEGylation platform. The presence of an outside the central cavity intramolecular crosslink, succinimidophenyl-PEG2K between
Cys-93(β, β′) in (TCP-PEG5K)6-ββ-Hb strongly impacts its solution properties. These patterns of influence suggest that the inter-dimeric interactions in
(TCP-PEG5K)6-Hb is weakened just as with other direct PEGylation platforms, and (SP-PEG5K)6-Hb generated by EAF-PEGylation is unique in not inducing this effect. A comparison of the properties of hexaPEGylated Hbs
establishes that rigidity of the conjugation linkage between PEG and Hb plays a significant influence on the resultant dictating
solution properties and/structure/conformation of PEG-Hb adduct. 相似文献
677.
Anita Shete Pratap N. Mukhopadhyaya Arpan Acharya Bikash A. Aich Suresh Joshi Vikram S. Ghole 《Journal of applied genetics》2008,49(4):425-431
Possibility of perchlorate reduction by microbes raises hope for an eco-friendly mode of degradation of this toxic rocket
fuel. This study reports 3 isolates (A1, A2 and A3) capable of molybdenum-independent degradation of perchlorate under aerobic
conditions. The rate of degradation was the highest when perchlorate concentration was 17 mM, and then 3.2 mM, 4.7 mM and
4.1 mM of perchlorate was reduced by isolates A1, A2 and A3 (respectively) after 72 h at 28°C under aerobic conditions. Presence
of perchlorate at a concentration higher than 17 mM resulted in some inhibition of perchlorate reduction. 16S ribosomal RNA
gene analysis revealed isolate A1 to bePseudomonas stutzeri (Proteobacteria) while isolates A2 ad A3 where found to belong to the genusArthrobacter (Actinobacteria). The study, apart from demonstrating ribotyping as a rapid method of identification of economically important
soil microbes, also raised prospects for using artificial consortia for environmental degradation of perchlorate, without
apparent domination ofDechloromonas spp. (a group of microbes known for perchlorate remediation in the environment). 相似文献
678.
N G Oikonomakos K R Acharya A E Melpidou D I Stuart L N Johnson 《Archives of biochemistry and biophysics》1989,270(1):62-68
The binding of beta-glycerophosphate (glycerol-2-P) to glycogen phosphorylase b in the crystal has been studied by X-ray diffraction at 3 A resolution. Glycerol-2-P binds to the allosteric effector site in a position close to that of AMP, glucose-6-P, UDP-Glc, and phosphate. In this position, glycerol-2-P is stabilized through interactions of its phosphate moiety with the guanidinium groups of Arg 309 and Arg 310 which undergo conformational changes, and the hydroxyl group of Tyr 75, while the same residues and solvent are involved in van der Waals interactions with the remaining part of the molecule. Kinetic experiments indicate that glycerol-2-P partially competes with both the activator (AMP) and the inhibitor (glucose 6-phosphate) of phosphorylase b. A comparison of the positions of glycerol-2-P, AMP, glucose 6-phosphate, UDP-Glc, and Pi at the allosteric site is presented. 相似文献
679.
680.
We studied the effects of superfusion of canine heart muscle tissue with a solution that mimicks hypoxia, acidosis and hyperkalemia (altered Tyrode's solution). Contracture (rise in resting tension) develops much sooner (5.2 +/- 0.8 vs. 30-40 min in 5 mM dextrose) in the absence of dextrose. High dextrose (55 mM) stabilizes the rise in tonic tension and protects against the action potential shortening during such superfusion. Presence of verapamil (1-1.5 microM) during altered Tyrode's superfusion considerably lessens the magnitude of the increase in tonic tension (31.7 +/- 8.6 vs. 129.5 +/- 32.6 mg in the control). Presence of high magnesium (5 mM) during altered Tyrode's superfusion also offers some protection against tonic tension increase (12.6 +/- 3.6 mg rise in tonic tension vs. 129.5 +/- 3.2 mg in the control), action potential shortening, and amplitude decrease. These results suggest that (a) magnesium and verapamil both have significant effects on the cellular calcium uptake, and (b) anaerobic metabolism utilizing either glycogen or exogenous glucose is capable of preventing contracture during ischemia. 相似文献