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111.
A molecular and evolutionary study of the beta-globin gene family of the Australian marsupial Sminthopsis crassicaudata 总被引:1,自引:0,他引:1
Cooper SJ; Murphy R; Dolman G; Hussey D; Hope RM 《Molecular biology and evolution》1996,13(7):1012-1022
Beta-globin gene families in eutherians (placental mammals) consist of a
set of four or more developmentally regulated genes which are closely
linked and, in general, arranged in the order 5'-embryonic/fetal genes-
adult genes-3'. This cluster of genes is proposed to have arisen by tandem
duplication of ancestral beta-globin genes, with the first duplication
occurring 200 to 155 MYBP just prior to a period in mammalian evolution
when eutherians and marsupials diverged from a common ancestor. In this
paper we trace the evolutionary history of the beta-globin gene family back
to the origins of these mammals by molecular characterization of the
beta-globin gene family of the Australian marsupial Sminthopsis
crassicaudata. Using Southern and restriction analysis of total genomic DNA
and bacteriophage clones of beta-like globin genes, we provide evidence
that just two functional beta-like globin genes exist in this marsupial,
including one embryonic- expressed gene (S.c-epsilon) and one
adult-expressed gene (S.c-beta), linked in the order 5'-epsilon-beta-3'.
The entire DNA sequence of the adult beta-globin gene is reported and shown
to be orthologous to the adult beta-globin genes of the North American
marsupial Didelphis virginiana and eutherian mammals. These results,
together with results from a phylogenetic analysis of mammalian beta-like
globin genes, confirm the hypothesis that a two-gene cluster, containing an
embryonic- and an adult-expressed beta-like globin gene, existed in the
most recent common ancester of marsupials and eutherians. Northern analysis
of total RNA isolated from embryos and neonatals indicates that a switch
from embryonic to adult gene expression occurs at the time of birth,
coinciding with the transfer of the marsupial from a uterus to a pouch
environment.
相似文献
112.
Domains of receptor mobility and endocytosis in the membranes of neonatal human erythrocytes in the membranes of neonatal human erythrocytes and reticulocytes are deficient in spectrin
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It has previously shown (Schekman, R., and S.J. Singer, Proc. Natl. Acad. Sci. U.S.A. 73:4075-4079) that receptors in the membranes of neonatal human erythrocytes show a restricted degree of lateral mobility, whereas in adult human erythrocytes the receptors are essentially immobile. This restricted mobility is exhibited, for example, when concanavalin A (Con A) induces a limited clustering of its receptors in the neonatal erythrocyte membrane, resulting in the formation of invaginations and endocytic vesicles. This does not happen with adult cells. By the use of indirect immunoferritin labeling of ultrathin frozen sections of Con A-treated neonatal blood cells, we now show that the invaginations and endocytotic vesicles do not stain for spectrin, whereas the adjacent unperturbed membrane is heavily stained. The reticulocytes in the neonatal cell population undergo substantially more Con A-induced invagination and endocytosis than do the erythrocytes. These results lend strong support to the hypothesis that specialized discrete domains exist, or are induced, in the membranes of these neonatal cells, in which receptors are laterally mobile, whereas in the remaining (and predominant) part of the membrane the receptors are immobile. Such mobile domains are characterized by an absence of spectrin. During the maturation of the neonatal reticulocyte to erythrocyte, it is proposed that these domains are in large part, but not completely, eliminated. 相似文献
113.
Polyploid giant cells provide a survival mechanism for p53 mutant cells after DNA damage 总被引:4,自引:0,他引:4
The relationships between delayed apoptosis, polyploid 'giant' cells and reproductive survivors were studied in p53-mutated lymphoma cells after DNA damage. Following severe genotoxic insult with irradiation or chemotherapy, cells arrest at the G(2)-M cell cycle check-point for up to 5 days before undergoing a few rounds of aberrant mitoses. The cells then enter endoreduplication cycles resulting in the formation of polyploid giant cells. Subsequently the majority of the giant cells die, providing the main source of delayed apoptosis; however, a small proportion survives. Kinetic analyses show a reciprocal relationship between the polyploid cells and the diploid stem line, with the stem line suppressed during polyploid cell formation and restituted after giant cell disintegration. The restituted cell-line behaves with identical kinetics to the parent line, once re-irradiated. When giant cells are isolated and followed in labelling experiments, the clonogenic survivors appear to arise from these cells. These findings imply that an exchange exists between the endocyclic (polyploid) and mitotic (diploid or tetraploid) populations during the restitution period and that giant cells are not always reproductively dead as previously supposed. We propose that the formation of giant cells and their subsequent complex breakdown and subnuclear reorganization may represent an important response of p53-mutated tumours to DNA damaging agents and provide tumours with a mechanism of repair and resistance to such treatments. 相似文献
114.
115.
Greg J Poet Ojore BV Oka Marcel van Lith Zhenbo Cao Philip J Robinson Marie Anne Pringle Elias SJ Arnér Neil J Bulleid 《The EMBO journal》2017,36(5):693-702
Folding of proteins entering the secretory pathway in mammalian cells frequently requires the insertion of disulfide bonds. Disulfide insertion can result in covalent linkages found in the native structure as well as those that are not, so‐called non‐native disulfides. The pathways for disulfide formation are well characterized, but our understanding of how non‐native disulfides are reduced so that the correct or native disulfides can form is poor. Here, we use a novel assay to demonstrate that the reduction in non‐native disulfides requires NADPH as the ultimate electron donor, and a robust cytosolic thioredoxin system, driven by thioredoxin reductase 1 (TrxR1 or TXNRD1). Inhibition of this reductive pathway prevents the correct folding and secretion of proteins that are known to form non‐native disulfides during their folding. Hence, we have shown for the first time that mammalian cells have a pathway for transferring reducing equivalents from the cytosol to the ER, which is required to ensure correct disulfide formation in proteins entering the secretory pathway. 相似文献
116.
Genes essential for the production of a linear, bacterial (1-->3)-beta-
glucan, curdlan, have been cloned for the first time from Agrobacterium sp.
ATCC31749. The genes occurred in two, nonoverlapping, genomic fragments
that complemented different sets of curdlan( crd )-deficient
transposon-insertion mutations. These were detected as colonies that failed
to stain with aniline blue, a (1-->3)-beta-glucan specific dye. One
fragment carried a biosynthetic gene cluster (locus I) containing the
putative curdlan synthase gene, crdS, and at least two other crd genes. The
second fragment may contain only a single crd gene (locus II).
Determination of the DNA sequence adjacent to several locus I mutations
revealed homology to known sequences only in the cases of crdS mutations.
Complete sequencing of the 1623 bp crdS gene revealed highest similarities
between the predicted CrdS protein (540 amino acids) and glycosyl
transferases with repetitive action patterns. These include bacterial
cellulose synthases (and their homologs), which form
(1-->4)-beta-glucans. No similarity was detected with putative
(1-->3)- beta-glucan synthases from yeasts and filamentous fungi.
Whatever the determinants of the linkage specificity of these beta-glucan
synthases might be, these results raise the possibility that
(1-->3)-beta-glucans and (1-->4)-beta-glucans are formed by related
catalytic polypeptides.
相似文献
117.
G R Pettit G M Cragg C W Holzapfel A A Tuinman D P Gieschen 《Analytical biochemistry》1987,162(1):236-241
Although sulfolane proved unexpectedly to be a poor solvent for solution-phase secondary-ion mass spectrometry of underivatized amino acids in the presence of thallium(I) salts, glycerol was somewhat more effective. Also, the addition of trifluoromethanesulfonic acid proved more effective than addition of the metal in generating molecular ion complexes. A convenient and reliable method for rapidly determining amino acid molecular ions is based on these observations. 相似文献
118.
Prokaryotic community composition and biogeochemical processes in deep subseafloor sediments from the Peru Margin 总被引:5,自引:0,他引:5
Webster G Parkes RJ Cragg BA Newberry CJ Weightman AJ Fry JC 《FEMS microbiology ecology》2006,58(1):65-85
The community compositions of Bacteria and Archaea were investigated in deep, sub-seafloor sediments from the highly productive Peru Margin (ODP Leg 201, sites 1228 and 1229, c. 25 km apart) down to nearly 200 m below the seafloor using taxonomic (16S rRNA) and functional (mcrA and dsrA) gene markers. Bacterial and archaeal groups identified from clone libraries of 16S rRNA gene sequences at site 1229 agreed well with sequences amplified from bands excised from denaturing gradient gel electrophoresis (DGGE) depth profiles, with the exception of the Miscellaneous Crenarchaeotic Group (MCG). This suggested that the prokaryotic community at site 1228, obtained from DGGE profiling alone, was reliable. Sites were dominated by Bacteria in the Gammaproteobacteria, Chloroflexi (green non-sulphur bacteria) and Archaea in the MCG and South African Gold Mine Euryarchaeotic Group, although community composition changed with depth. The candidate division JS1 was present throughout both sites but was not dominant. The populations identified in the Peru Margin sediments consisted mainly of prokaryotes found in other deep subsurface sediments, and were more similar to communities from the Sea of Okhotsk (pelagic clays) than to those from the low organic carbon Nankai Trough sediments. Despite broad similarities in the prokaryotic community at the two sites, there were some differences, as well as differences in activity and geochemistry. Methanogens (mcrA) within the Methanosarcinales and Methanobacteriales were only found at site 1229 (4 depths analysed), whereas sulphate-reducing prokaryotes (dsrA) were only found at site 1228 (one depth), and these terminal-oxidizing prokaryotes may represent an active community component present at low abundance. This study clearly demonstrates that the deep subsurface sediments of the Peru Margin have a large diverse and metabolically active prokaryotic population. 相似文献
119.
Differential inhibition of beta-hexosaminidase A and beta-hexosaminidase B by suramin 总被引:1,自引:0,他引:1
G Constantopoulos S Rees B G Cragg J A Barranger R O Brady 《Biochemical and biophysical research communications》1981,101(4):1345-1349
The trypanocidal drug suramin is a potent inhibitor of β-hexosaminidase A with a Ki of about 4.5 μM, and to a lesser extent of β-hexosaminidase B (Ki 31.5 μM). β-Hexosaminidase B remained active in the presence of 1.0 mM suramin whereas the activity of β-hexosaminidase A was completely inhibited at 0.1 mM. 相似文献
120.