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排序方式: 共有276条查询结果,搜索用时 15 毫秒
1.
2.
The anterograde axonal transport of choline-phosphoglycerides was studied in sciatic nerve motoneurons of adult (3-month-old) and aged (24-month-old) rats. After the spinal cord injection of [2-3H]glycerol, choline-phosphoglycerides; the major phospholipid class was transported along the nerve. The axonal transport rate was determined by plotting the distance covered by the front of transported radioactivity as a function of the time employed. In aged animals the rate of the choline-phosphoglyceride anterograde axonal transport was about 68% lower than that of adults; furthermore, the rate slowed down along the nerve in the proximal-distal direction. This alterated axonal transport mechanism might contribute to the degenerative processes observed in distal regions of peripheral nerve fibers of aged animals. 相似文献
3.
M Cigolini C Zancanaro O Fezzi R Dalle Grave P Bertoldi L Brunetti O Bosello 《Hormones et métabolisme》1986,18(2):88-90
Several authors have not been able to find any antilipolytic effect of insulin in adipose tissue "in vitro". We investigated the possible role of cell size and/or age of donors on this phenomenon. The lipolytic rates (glycerol release per cell) were lower in the small cells of the 4-6 weeks old rats than in the larger cells of the 25-30 weeks old animals; however, the difference disappeared when the data were expressed per unit of cell surface area. Insulin (0.5-50 ng/ml) failed to inhibit both maximally and submaximally noradrenaline stimulated lipolysis in the adipocytes of the young rats, but its antilipolytic action was fully restored by using glucose-free medium. Therefore, at our experimental conditions, a glucose dependent factor, possibly involving the preferential hydrolysis of newly synthetized triglycerides, seems to blunt or to mask the insulin induced inhibition of glycerol release. Relatively higher rates of glucose metabolism and a lower lipolysis in small fat cells might explain the difference in the action of insulin on glycerol release in the adipose tissue of young rats as compared to the older ones. 相似文献
4.
V Trischitta K Y Wong A Brunetti R Scalisi R Vigneri I D Goldfine 《The Journal of biological chemistry》1989,264(9):5041-5046
The endocytosis, recycling, and degradation of the insulin receptor were studied in IM-9 cells and U-937 cells by employing two monoclonal antibodies directed at the alpha subunit of the human insulin receptor, antibodies MA-5 and MA-10. Antibody MA-5 is an insulin agonist and MA-10 is an insulin antagonist (Forsayeth, J., Caro, J.F., Sinha, M.K., Maddux, B.A., and Goldfine, I.D. (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 3448-3451). Both monoclonal antibodies, like insulin, induced the endocytosis of the insulin receptor within 15 min. Upon removal of extracellular ligand the internalized receptor recycled to the cell surface. At this time there was no degradation of the receptor as measured by a sensitive insulin receptor radioimmunoassay. After 20 h of incubation, insulin and MA-5, but not MA-10, induced significant receptor degradation as measured by both insulin receptor radioimmunoassay and metabolic labeling studies. These studies demonstrated, therefore, that: 1) internalization and recycling of the receptor can be induced by antireceptor monoclonal antibodies that are either insulin agonists or insulin antagonists; 2) enhanced receptor degradation can be induced by monoclonal antibodies that are insulin agonists; and 3) the process of receptor internalization does not necessarily lead to enhanced receptor degradation. Since prior studies have indicated that neither MA-5 nor MA-10 enhance insulin receptor kinase activity, the present studies also suggest that insulin receptor endocytosis and degradation induced by ligands different than insulin can occur without activation of this process. 相似文献
5.
Insulin receptor monoclonal antibodies that mimic insulin action without activating tyrosine kinase 总被引:9,自引:0,他引:9
D M Hawley B A Maddux R G Patel K Y Wong P W Mamula G L Firestone A Brunetti E Verspohl I D Goldfine 《The Journal of biological chemistry》1989,264(5):2438-2444
HTC rat hepatoma cells were transfected with human insulin receptor cDNA to a level of 40,000 receptors/cell. In these cells, as well as in nontransfected cells, insulin stimulated the uptake of alpha-aminoisobutyric acid. Two monoclonal antibodies directed against the human insulin receptor alpha subunit, like insulin, stimulated amino acid uptake in transfected HTC cells, but not in nontransfected HTC cells. The antibodies, in contrast to insulin, failed to stimulate insulin receptor tyrosine kinase activity, both in intact transfected cells and in cell free extracts prepared from them. These data suggest, therefore, that activation of insulin receptor tyrosine kinase may not be an obligatory step in all of the transmembrane signaling mechanisms of the insulin receptor. 相似文献
6.
Role of mannose-6-phosphate receptors in herpes simplex virus entry into cells and cell-to-cell transmission. 总被引:18,自引:14,他引:4 下载免费PDF全文
C R Brunetti R L Burke B Hoflack T Ludwig K S Dingwell D C Johnson 《Journal of virology》1995,69(6):3517-3528
Herpes simplex virus (HSV) glycoprotein D (gD) is essential for virus entry into cells, is modified with mannose-6-phosphate (M-6-P), and binds to both the 275-kDa M-6-P receptor (MPR) and the 46-kDa MPR (C. R. Brunetti, R. L. Burke, S. Kornfeld, W. Gregory, K. S. Dingwell, F. Masiarz, and D. C. Johnson, J. Biol. Chem. 269:17067-17074, 1994). Since MPRs are found on the surfaces of mammalian cells, we tested the hypothesis that MPRs could serve as receptors for HSV during virus entry into cells. A soluble form of the 275-kDa MPR, derived from fetal bovine serum, inhibited HSV plaques on monkey Vero cells, as did polyclonal rabbit anti-MPR antibodies. In addition, the number and size of HSV plaques were reduced when cells were treated with bovine serum albumin conjugated with pentamannose-phosphate (PM-PO4-BSA), a bulky ligand which can serve as a high-affinity ligand for MPRs. These data imply that HSV can use MPRs to enter cells; however, other molecules must also serve as receptors for HSV because a reasonable fraction of virus could enter cells treated with even the highest concentrations of these inhibitors. Consistent with the possibility that there are other receptors, HSV produced the same number of plaques on MPR-deficient mouse fibroblasts as were produced on normal mouse fibroblasts, but there was no inhibition with PM-PO4-BSA with either of these embryonic mouse cells. Together, these results demonstrate that HSV does not rely solely on MPRs to enter cells, although MPRs apparently play some role in virus entry into some cell types and, perhaps, act as one of a number of cell surface molecules that can facilitate entry. We also found that HSV produced small plaques on human fibroblasts derived from patients with pseudo-Hurler's polydystrophy, cells in which glycoproteins are not modified with M-6-P residues and yet production of infectious HSV particles was not altered in the pseudo-Hurler cells. In addition, HSV plaque size was reduced by PM-PO4-BSA; therefore, it appears that M-6-P residues and MPRs are required for efficient transmission of HSV between cells, a process which differs in some respects from entry of exogenous virus particles. 相似文献
7.
Nucleotide variation at the hypervariable esterase 6 isozyme locus of Drosophila simulans 总被引:2,自引:0,他引:2
Esterase 6 (Est-6/EST6) is polymorphic in both Drosophila melanogaster and
D. simulans for two common allozyme forms, as well as for several other
less common variants. Parallel latitudinal clines in the frequencies of the
common EST6-F and EST6-S allozymes in these species have previously been
interpreted in terms of a shared amino acid polymorphism that distinguishes
the two variants and is subject to selection. Here we compare the sequences
of four D. simulans Est-6 isolates and show that overall estimates of
nucleotide heterozygosity in both coding and 5' flanking regions are more
than threefold higher than those obtained previously for this gene in D.
melanogaster. Nevertheless, the ratio of replacement to exon silent-site
polymorphism in D. simulans is less than the ratio of replacement to silent
divergence between D. simulans and D. melanogaster, which could be the
result of increased efficiency of selection against replacement
polymorphisms in D. simulans or to divergent selection between the two
species. We also find that the amino acid polymorphisms separating EST6- F
and EST6-S in D. simulans are not the same as those that separate these
allozymes in D. melanogaster, implying that the shared clines do not
reflect shared molecular targets for selection. All comparisons within and
between the two species reveal a remarkable paucity of variation in a
stretch of nearly 400 bp immediately 5' of the gene, indicative of strong
selective constraint to retain essential aspects of Est-6 promoter
function.
相似文献
8.
The mechanisms and pathways of synthesis of phosphatidylcholine in the giant fibre system of the squid (Loligo vulgaris) have been examined by incubating the stellate ganglion-nerve preparation or its separated compartments in an artificial bathing solution with labelled choline. Other experiments were done by dissecting the whole stellate ganglion into axoplasm, axon sheath, giant fibre lobe, small fibres and ganglion residue, after incubation. The initial rate of choline incorporation into choline phosphoglycerides was severalfold higher in the lobe than in the axon. Higher lipid radioactivity was recovered in the axon sheath as compared to the axoplasm, and in the small fibres as compared to the ganglion residue which contains its cell bodies. The production of phosphorylcholine and CDP-choline in the intact ganglion-nerve preparation during incubation with choline points to the occurrence of the net synthesis pathway for phosphatidylcholine in this material. Base-exchange activity was also observed in the axon and giant fibre lobe preparations in vitro, but no indication can yet be given whether it also takes place in intact preparations. Electrical stimulation and‘depolarizing’conditions enhance choline phosphorylation in the squid axon and lobe, but decrease phosphatidylcholine labelling. 相似文献
9.
The incorporation of cytidine-containing precursors (CDP-Cho and CDP-Etn) into the main phospholipid classes of cellular fractions enriched in neurons and glial cells from whole rat brains of different ages was examined. The rate of synthesis of choline phosphoglycerides in neuronal homogenates significantly decreased with age up to 18 months; after this time no additional decrease was found. The decrease of CDP-Etn incorporation in neurons was found to be less significantly affected by age up to 18 months, but the enzymic activity decreased after 18 months of age. No changes were found in the corresponding glial activity at any age. Biochemical phenomena that occur in 18-month-old rat brain (aged animals) were compared with phenomena occurring in 2-month-old rat brain (adult animals). No significant variations of lipid composition were found in neurons from either 18-month-old or 2-month-old rat brain. These results, together with some kinetic parameters, suggest that ethanolamine and choline phosphotransferases are affected differently by aging. 相似文献
10.
G Bolli M G Cartechini P Compagnucci S Malvicini P De Feo F Santeusanio G Angeletti P Brunetti 《Hormones et métabolisme》1979,11(9):493-497
Urinary excretion and plasma levels of catecholamines were determined in 20 normal and 39 diabetic subjects to evaluate the sympathetic activity. Diabetic patients were divided into 4 groups according to the metabolic control. Sympathetic activity showed no differences between normal and subjects with chemical diabetes (group I, n = 5). In insulin-treated diabetics in good metabolic control (group II, n = 11) only urinary excretion of free norepinephrine was significantly higher than normals (p less than .05). In insulin-treated diabetics in poor metabolic control (group III, n = 16) urinary excretion and plasma levels of norepinephrine showed a marked increase over groups I and II (p less than .001). In insulin-treated diabetics with ketosis (group IV, n = 7) urinary excretion and plasma levels of both norepinephrine and epinephrine showed the highest values (p less than .001 and less than .1). Finally, in groups III and IV, after achieving improved metabolic control, a significant decrease of urinary excretion and plasma levels of catecholamines was observed. The results confirm that there is an increased rate of catecholamine release in poorly controlled diabeties and suggest a close correlation between sympathetic activity and metabolic derangement in diabetes. 相似文献