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91.
Arabinose 5-phosphate (A5P) is the aldopentose version of the ketohexose fructose 6-phosphate (F6P), having identical stereochemistry but lacking atoms corresponding to the 1-carbon and 1-hydroxyl. Despite structural similarity and conservation of the reactive portion of F6P, F6P acts as a substrate whereas A5P is reported to be an inhibitor of transaldolase. To address the lack of A5P reactivity we determined a crystal structure of the Francisella tularensis transaldolase in complex with A5P. This structure reveals that like F6P, A5P forms a covalent Schiff base with active site Lys135. Unlike F6P, A5P binding fails to displace an ordered active site water molecule. Retaining this water necessitates conformational changes at the A5P-protein linkage that possibly hinder reactivity. The findings presented here show the basis of A5P inhibition and suggest an unusual mechanism of competitive, reversible-covalent transaldolase regulation. 相似文献
92.
The purification and characterization of bovine enterokinase from membrane fragments in the duodenal mucosal fluid 总被引:4,自引:0,他引:4
Bovine enterokinase has been purified from the mucosal fluid adhering to the intestinal wall. Enterokinase is predominantly present as membrane fragments which must be treated with Triton X-100 to release the enzyme. The purification resulted in a higher yield of enzyme in fewer steps and in less time than when mucosal cells were used. The properties of the enzyme in the fluid are identical with those found previously with the mucosal cell preparation (Liepnieks, J. J., and Light, A. (1979) J. Biol. Chem. 254, 1677-1683), but differ in the size of the subunits and in amino acid composition from the enzyme purified from intestinal contents (Anderson, L. E. Walsh, K. A., and Neurath, H. (1977) Biochemistry 16, 3354-3360). It is highly unlikely that the existence of isoenzymes could explain these differences. It is more likely that the enzyme isolated from the intestinal contents represents an extensively degraded form with retention of enzymatic activity. 相似文献
93.
94.
Unusual composition of peptidoglycan in Bordetella pertussis 总被引:3,自引:0,他引:3
E Tuomanen J Schwartz S Sande K Light D Gage 《The Journal of biological chemistry》1989,264(19):11093-11098
The composition of the peptidoglycan of Bordetella pertussis and the nature of its turnover products was determined by a new combination of analytical techniques: high performance liquid chromatography of an enzymatic peptidoglycan hydrolysate and fast atom bombardment mass spectrometry and fast atom bombardment collision-activated dissociation tandem mass spectrometry. Sixteen major components of the peptidoglycan were purified, and assignment of complete or partial chemical structures was achieved for nine and seven species, respectively. At this level of resolution, a previously unrecognized heterogeneity of monomeric (five new species; nine total) and dimeric species (five new species; five total) was detected. No species containing diaminopimelyl-diaminopimelic acid cross-links or lysyl-arginine substitutions were found. Previous estimates of total cross-linkage and average chain length were revised downward to 32% and 21 disaccharide residues, respectively. Detection of a chemically novel species, a disaccharide octapeptide monomer, in both the peptidoglycan hydrolysate and culture supernatant fluid, suggests that an N-acetyl-muramyl-L-alanine amidase acts on the intact peptidoglycan of Bordetella and participates in cell wall turnover. Five peptidoglycan turnover products were identified in the supernatant fluid of late logarithmic phase cultures, including the 1,6-anhydro monomeric species known as tracheal cytotoxin. Peptidoglycan turnover was detected at a low rate of approximately 10%/generation, a value sufficient to account for the generation of all tracheal cytotoxin found in culture supernatant fluids. 相似文献
95.
96.
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98.
Nicholas D. Light 《Biochemical and biophysical research communications》1978,81(2):261-267
Studies reproted here indicate that a major cell surface glycoprotein of the rabbit bone marrow erythroid cell may be involved in binding transferrin. The glycoprotein has an apparent molecular weight of 18,000. It is suggested that bone marrow erythroid cells may provide an invaluable source of the red cell membrane transferrin receptor for future studies. 相似文献
99.
Baer-Lehman ML Light T Fuller NW Barry-Landis KD Kindlin CM Stewart RL 《Experimental & applied acarology》2012,58(3):301-314
Competition among ticks, and among ectoparasites generally, has rarely been demonstrated. Ixodes scapularis and Dermacentor albipictus are both hard ticks commonly found feeding on deer harvested at Letterkenny Army Depot, in south central Pennsylvania, USA. The two species have contrasting life histories resulting in D. albipictus spending notably more time on the shared host. We hypothesized that this would give D. albipictus an advantage in locating and occupying optimal attachment sites (highly vascularized areas like the head and ears). Ticks were collected from 224 hunter-killed deer in December 2005 and November 2006 to determine if there is evidence of competition for attachment sites when these two species concurrently infest deer. A timed sample (3?min per region) of representative ticks was collected from the head (ears, face and neck regions) and body (axillae regions). Ixodes scapularis was more abundant and prevalent overall than D. albipictus. Dermacentor albipictus was found almost exclusively on the head, whereas I. scapularis was more evenly distributed, but somewhat more abundant on the body than on the head. The proportion of I. scapularis on the head was reduced at high D. albipictus abundances, but I. scapularis abundance did not alter the distribution of D. albipictus. This study supports the hypothesis of competition for preferred attachment sites between these two species of ticks, and suggests that D. albipictus may be competitively dominant over I. scapularis on the head region of concurrently infested white-tailed deer. 相似文献
100.
Light SH Halavaty AS Minasov G Shuvalova L Anderson WF 《Protein science : a publication of the Protein Society》2012,21(6):887-895
3-Deoxy-D-arabino-heptulosonate 7-phosphate synthase (DAHPS) catalyzes the first step in the biosynthesis of a number of aromatic metabolites. Likely because this reaction is situated at a pivotal biosynthetic gateway, several DAHPS classes distinguished by distinct mechanisms of allosteric regulation have independently evolved. One class of DAHPSs contains a regulatory domain with sequence homology to chorismate mutase-an enzyme further downstream of DAHPS that catalyzes the first committed step in tyrosine/phenylalanine biosynthesis-and is inhibited by chorismate mutase substrate (chorismate) and product (prephenate). Described in this work, structures of the Listeria monocytogenes chorismate/prephenate regulated DAHPS in complex with Mn(2+) and Mn(2+) + phosphoenolpyruvate reveal an unusual quaternary architecture: DAHPS domains assemble as a tetramer, from either side of which chorismate mutase-like (CML) regulatory domains asymmetrically emerge to form a pair of dimers. This domain organization suggests that chorismate/prephenate binding promotes a stable interaction between the discrete regulatory and catalytic domains and supports a mechanism of allosteric inhibition similar to tyrosine/phenylalanine control of a related DAHPS class. We argue that the structural similarity of chorismate mutase enzyme and CML regulatory domain provides a unique opportunity for the design of a multitarget antibacterial. 相似文献