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31.
The hmc operon of Desulfovibrio vulgaris subsp. vulgaris Hildenborough encodes a potential transmembrane redox protein complex. 总被引:3,自引:2,他引:1
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M Rossi W B Pollock M W Reij R G Keon R Fu G Voordouw 《Journal of bacteriology》1993,175(15):4699-4711
The nucleotide sequence of the hmc operon from Desulfovibrio vulgaris subsp. vulgaris Hildenborough indicated the presence of eight open reading frames, encoding proteins Orf1 to Orf6, Rrf1, and Rrf2. Orf1 is the periplasmic, high-molecular-weight cytochrome (Hmc) containing 16 c-type hemes and described before (W. B. R. Pollock, M. Loutfi, M. Bruschi, B. J. Rapp-Giles, J. D. Wall, and G. Voordouw, J. Bacteriol. 173:220-228, 1991). Orf2 is a transmembrane redox protein with four iron-sulfur clusters, as indicated by its similarity to DmsB from Escherichia coli. Orf3, Orf4, and Orf5 are all highly hydrophobic, integral membrane proteins with similarities to subunits of NADH dehydrogenase or cytochrome c reductase. Orf6 is a cytoplasmic redox protein containing two iron-sulfur clusters, as indicated by its similarity to the ferredoxin domain of [Fe] hydrogenase from Desulfovibrio species. Rrf1 belongs to the family of response regulator proteins, while the function of Rrf2 cannot be derived from the gene sequence. The expression of individual genes in E. coli with the T7 system confirmed the open reading frames for Orf2, Orf6, and Rrf1. Deletion of 0.4 kb upstream from orf1 abolished the expression of Hmc in D. desulfuricans G200, indicating this region to contain the hmc operon promoter. The expression of two truncated hmc genes in D. desulfuricans G200 resulted in stable periplasmic c-type cytochromes, confirming the domain structure of Hmc. We propose that Hmc and Orf2 to Orf6 form a transmembrane protein complex that allows electron flow from the periplasmic hydrogenases to the cytoplasmic enzymes that catalyze the reduction of sulfate. The domain structure of Hmc may be required to allow interaction with multiple hydrogenases. 相似文献
32.
33.
Summary Sequence-specific 1H and 15N resonance assignments have been made for 137 of the 146 nonprolyl residues in oxidized Desulfovibrio desulfuricans [Essex 6] flavodoxin. Assignments were obtained by a concerted analysis of the heteronuclear three-dimensional 1H-15N NOESY-HMQC and TOCSY-HMQC data sets, recorded on uniformly 15N-enriched protein at 300 K. Numerous side-chain resonances have been partially or fully assigned. Residues with overlapping 1HN chemical shifts were resolved by a three-dimensional 1H-15N HMQC-NOESY-HMQC spectrum. Medium-and long-range NOEs, 3JNH
coupling constants, and 1HN exchange data indicate a secondary structure consisting of five parallel -strands and four -helices with a topology similar to that of Desulfovibrio vulgaris [Hidenborough] flavodoxin. Prolines at positions 106 and 134, which are not conserved in D. vulgaris flavodoxin, contort the two C-terminal -helices.Abbreviations CSI
chemical shift index
- DQF-COSY
double-quantum-filtered correlation spectroscopy
- DIPSI
decoupling in the presence of scalar interactions
- FMN
flavin mononucleotide
- GARP
globally optimized alternating phase rectangular pulse
- HMQC
heteronuclear multiple-quantum coherence
- HSQC
heteronuclear single-quantum coherence
- NOE
nuclear Overhauser effect
- NOESY
nuclear Overhauser enhancement spectroscopy
- TOCSY
total correlation spectroscopy
- TPPI
time-proportional phase increments
- TSP
3-(trimethylsilyl)propionic-2,2,3,3-d
4 acid, sodium salt 相似文献
34.
The lozenge locus is genetically complex, containing two functionally distinct units, cistrons A and B, that influence the structure of
the compound eye. Extreme mutations of either cistron produce adult phenotypes that share similarities and that have striking
differences. We have analyzed the expression of several developmentally important eye genes including boss, scabrous, rhomboid, seven-up, and Bar in lozenge mutant backgrounds representing both cistrons. This analysis follows the progressive recruitment of photoreceptor neurons
during eye development and has confirmed that the initial development of photoreceptors is normal up to the five cell precluster
stage (R8, R2/5 and R3/4). However, when lozenge is mutant, further eye development is perturbed. As cells R1, R6 and R7 are recruited, patterns of gene expression for seven-up and Bar become abnormal. We have also characterized the expression of two different enhancer trap alleles of lozenge. The lozenge product(s) appear to be first expressed in the eye disc in undifferentiated cells shortly after the five cell precluster forms.
Then, as distinct cells are recruited to a fate, lozenge expression persists and is refined in those cells. Our data suggests that lozenge functions in cone cells and pigment cells as well as in specific glia. With respect to photoreceptor neurons, lozenge biases the developmental potential of cells R1, R6 and R7, by directly influencing the expression of genes important for establishing
cell fate.
Received: 26 July 1996 / Accepted: 6 January 1997 相似文献
35.
S Mac Neil S W Walker H J Senior A Pollock B L Brown S S Bleehen D S Munro S Tomlinson 《The Biochemical journal》1984,224(2):453-460
Calmodulin antagonists inhibited hormone-stimulated cyclic AMP accumulation in both cultured cells and cell lysates of mouse B16 melanoma. Particulate preparations of B16 melanoma contained 34-45% of total cell calmodulin, which could not be dissociated by extensive washing irrespective of the presence of EGTA in the buffer. The adenylate cyclase activity in such preparations was unaffected by the addition of exogenous calmodulin. However, the rare-earth-metal ion La3+, which can mimic or replace Ca2+ in many systems, produced an immediate inhibition of agonist-stimulated adenylate cyclase activity and preincubation of particulate preparations was La3+ followed by washing with La3+-free buffer dissociated calmodulin (96% loss) from particulate preparations. The loss of calmodulin from particulate preparations was associated with a decrease in agonist responsiveness (74%) and a marked change in the Ca2+-sensitivity of the enzyme, low concentrations of calcium (approx. 10 nM) now failing to stimulate enzyme activity, high concentrations of calcium (greater than or equal to 100 nM) producing greater-than-normal inhibition of enzyme activity. Direct activation of adenylate cyclase by the addition of pure calmodulin was now demonstrable in such calmodulin-depleted particulate preparations. Half-maximal stimulation of agonist-responsive adenylate cyclase occurred at 80 nM-calmodulin in the presence of 10 microM free Ca2+. Maximal stimulation by calmodulin (at 300-600 nM) restored enzyme activity to 89 +/- 5% (mean +/- S.E.M., n = 7) of the activity in untreated, calmodulin-intact, preparations. 相似文献
36.
Septal deviation is often associated with hypertrophy of the contralateral inferior turbinate. Failure to reduce the size of the turbinate at the time of septal reconstruction may result in persistent nasal obstruction. The authors present their experience with 408 patients who underwent one of four turbinate procedures over a 6-year period. Most patients underwent unilateral turbinate surgery, although bilateral procedures were undertaken in 7 percent of patients. A graduated surgical approach was taken that varied according to the amount of turbinate enlargement and the degree to which mucosa and bone were involved. Full-thickness excision of the anterior third to half of the inferior turbinate (turbinectomy) became a favored procedure. Relief of nasal obstruction was obtained in greater than 90 percent of patients. Healing was satisfactory regardless of the method, and complications, including hemorrhage and infection, were few. Long-term follow-up revealed no untoward sequelae, and no patient developed atrophic rhinitis. The authors conclude that turbinate surgery, particularly when unilateral, in the carefully selected patient with nasal obstruction is a useful adjunct to septal surgery. 相似文献
37.
Abstract— The tetrahydrofolate-dependent serine hydroxymethyl transferase ( l -serine: tetrahydrofolate 10-hydroxymethyl transferase, EC 2.1.2.1) reaction in rat or human brain homogenates incubated aerobically is dependent on added reducing agents for full activity in order to protect the readily oxidized substrate, tetrahydrofolate. In this role, 0.1 m m -NADH is as affective as 10m m -2-mercaptoethanol and it can be shown that the NADH prevents destruction of tetrahydrofolate incubated with brain homogenates. If the dihydropteridine reductase (NADPH:6,7-dihydropteridine oxidoreductase, EC 1.6.99.7) activity of the brain homogenate is inhibited by a specific antiserum, NADH, but not 2-mercaptoeth-anol, is no longer effective. Furthermore, an homogenate of a brain biopsy from a human lacking dihydropteridine reductase requires added dihydropteridine reductase for maximal stimulation by NADH of the serine hydroxymethyl transferase reaction. We conclude that dihydropteridine reductase mediates the NADH stimulation and can play a role in preserving tetrahydrofolate from oxidation. The rinding of greatly reduced folate levels in the brain biopsy from the human lacking dihydropteridine reductase supports this postulated role of dihydropteridine reductase in folate metabolism. 相似文献
38.
B. R. Pollock 《Journal of fish biology》1981,19(4):475-485
Age and growth patterns of luderick, Girella tricuspidata (Quoy and Gaimard), taken in the Moreton Bay net fishery are described. Scales have prominent annuli which are formed during the period May-July. The mean body length is similar for males and females, except for age class III where female fish are significantly larger. This probably results from the early movement of faster growing females onto the fishing ground. The scale method and length-frequency analysis both indicate that the variation in body lengths in each age class is large. The length-weight relationship was obtained and relative condition factor was found to be highest in July which corresponded with the peak in gonosomatic index. 相似文献
39.
40.
J H Brown J L Taylor S H Pollock 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1975,148(1):80-85
Experiments were carried out to determine the effectiveness of steroid therapy in vitamin E-deficiency, as measured by autohemolysis of isolated RBC's body weight gain, serum creatine phosphokinase activity, and stabilization or labilization of isolated hepatic lysosomes. Results of such experiments would indicate whether triamcinolone acetonide could supplant vitamin E in vitamin E-deficiency states via its ability to stablize various membranes. Autohemolysis induced by vitamin E-deficiency could not be prevented by daily administration of triamcinolone. Daily dosages of 0.1 and 0.4 mg/kg (ip) triamcinolone given concomitantly with replacement vitamin E (at sufficient dosages to reverse the autohemolysis) resulted in an increased autohemolysis. No changes in lysosomal membrane fragility were noted when hepatic lysosomes were obtained from vitamin E-deficient rats with triamcinolone resulted in a greater attenuation of body-weight gain. Creatine phosphokinase levels were not augmented in vitamin E-deficient rats. Vitamin E-deficient rats supplemented with vitamin E and treated with triamcinolone, manifested an increase in creatine, phosphokinase. It was therefore concluded that although triamcinolone and vitamin E possess a common ability to stablize membranes and proteins, their mechanisms must be different since triamcinolone could not substitute for vitamin E in a deficiency state. Indeed, triamcinolone was found to be more toxic in the absence of vitamin E. 相似文献