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51.
Sequencing and overexpression of the Escherichia coli aroE gene encoding shikimate dehydrogenase. 总被引:4,自引:0,他引:4
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The Escherichia coli aroE gene encoding shikimate dehydrogenase was sequenced. The deduced amino acid sequence was confirmed by N-terminal amino acid sequencing and amino acid analysis of the overproduced protein. The complete polypeptide chain has 272 amino acid residues and has a calculated Mr of 29,380. E. coli shikimate dehydrogenase is homologous to the shikimate dehydrogenase domain of the fungal arom multifunctional enzymes and to the catabolic quinate dehydrogenase of Neurospora crassa. 相似文献
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L W Coggins 《Journal of general microbiology》1979,113(1):189-193
The denaturation map of EcoRI-digested pCR11, a ColE1-Km plasmid, is described. The 2.0 kilobase ColE1-derived segment contains an adenine+thymine rich site in the colicin immunity gene region. In the 7.2 kilobase kanamycin resistance region, the transposon Tn903 consists of an adenine+thymine rich 0.98 kilobase kan gene region flanked by a guanine+cytosine rich 1.09 kilobase inverted duplication. 相似文献
55.
Hartney JM Coggins KG Tilley SL Jania LA Lovgren AK Audoly LP Koller BH 《American journal of physiology. Lung cellular and molecular physiology》2006,290(1):L105-L113
Prostaglandin E2 (PGE2), similar to beta-adrenergic receptor agonists, can protect airways from bronchoconstriction and resulting increase in airway resistance induced by a number of agents, including cholinergic receptor agonists and antigen. We examined the impact of sustained alterations in PGE2 pathways on changes in airway resistance. Genetic methods were utilized to alter PGE2 metabolism and signal transduction in the murine lung. PGE2 levels were elevated by generating mice lacking 15-hydroxyprostaglandin (Hpgd-/-), the major catabolic enzyme of PGE2, and by generating a transgenic line in which mouse PGE2 synthase (Ptges) expression is driven by a human lung-specific promoter, hSP-C. Conversely, to determine the impact of loss of PGE2 on airway reactivity, we examined mice lacking this synthase (Ptges-/-) and receptors that mediate the actions of PGE2, particularly the PGE2 EP2 receptor (Ptger2). Diminished capacity to produce and respond to PGE2 did not alter the response of mice to cholinergic stimuli. In contrast, the responsiveness to cholinergic stimulation was dramatically altered in animals with elevated PGE2 levels. The Hpgd-/- and hSP-C-Ptges transgenic lines both showed attenuated airway responsiveness to methacholine as measured by lung resistance. Thus, whereas compromise of the Ptges/PGE2/Ptger2 pathway does not alter airway responsiveness, genetic modulation that elevates PGE2 levels in the lung attenuates airway responsiveness. 相似文献
56.
Most estrous cycles in cows consist of 2 or 3 waves of follicular activity. Waves of ovarian follicular development comprise
the growth of dominant follicles some of which become ovulatory and the others are anovulatory. Ovarian follicular activity
in cows during estrous cycle was studied with a special reference to follicular waves and the circulating concentrations of
estradiol and progesterone. Transrectal ultrasound examination was carried out during 14 interovulatory intervals in 7 cows.
Ovarian follicular activity was recorded together with assessment of serum estradiol and progesterone concentrations. Three-wave
versus two-wave interovulatory intervals was observed in 71.4% of cows. The 3-wave interovulatory intervals differed from
2-wave intervals in: 1) earlier emergence of the dominant follicles, 2) longer in length, and 3) shorter interval from emergence
to ovulation. There was a progressive increase in follicular size and estradiol production during growth phase of each wave.
A drop in estradiol concentration was observed during the static phase of dominant anovulatory follicles. The size of the
ovulatory follicle was always greater and produced higher estradiol compared with the anovulatory follicle. In conclusion,
there was a predominance of 3-wave follicular activity that was associated with an increase in length of interovulatory intervals.
A dominant anovulatory follicle during its static phase may initiate the emergence of a subsequent wave. Follicular size and
estradiol concentration may have an important role in controlling follicular development and in determining whether an estrous
cycle will have 2 or 3-waves. 相似文献
57.
Specificity of substrate recognition by type II dehydroquinases as revealed by binding of polyanions
Evans LD Roszak AW Noble LJ Robinson DA Chalk PA Matthews JL Coggins JR Price NC Lapthorn AJ 《FEBS letters》2002,530(1-3):24-30
The interactions between the polyanionic ligands phosphate and sulphate and the type II dehydroquinases from Streptomyces coelicolor and Mycobacterium tuberculosis have been characterised using a combination of structural and kinetic methods. From both approaches, it is clear that interactions are more complex in the case of the latter enzyme. The data provide new insights into the differences between the two enzymes in terms of substrate recognition and catalytic efficiency and may also explain the relative potencies of rationally designed inhibitors. An improved route to the synthesis of the substrate 3-dehydroquinic acid (dehydroquinate) is described. 相似文献
58.
The O-antigen chain from the lipopolysaccharide of Helicobacter pylori
strain UA861 was determined to be composed of an elongated type 2 N -
acetyllactosamine backbone,
-[-->3)-beta-D-Gal-(1-->4)-beta-D-GlcNAc-(1- ]n-->, with
approximately half of the GlcNAc units carrying a terminal alpha-d-Glc
residue at the O -6 position. The O-chain of H.pylori UA861 was terminated
by a N -acetyllactosamine [beta-D-Gal-(1-->4)-beta-D- GlcNAc] (LacNAc)
epitope and did not express terminal Lewis X or Lewis Y blood-group
determinants as previously found in other H.pylori strains. The absence of
terminal Lewis X and Lewis Y blood-group epitopes and the replacement of
Fuc by Glc as a side chain in the O- chain of H.pylori UA861 represents yet
another type of lipopolysaccharide structure from H.pylori species. These
structural differences in H.pylori lipopolysaccharide molecules carry
implications with regard to possible different pathogenic events between
strains and respective hosts.
相似文献
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