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Purified hematopoietic stem cells can differentiate into hepatocytes in vivo   总被引:193,自引:0,他引:193  
The characterization of hepatic progenitor cells is of great scientific and clinical interest. Here we report that intravenous injection of adult bone marrow cells in the FAH(-/-) mouse, an animal model of tyrosinemia type I, rescued the mouse and restored the biochemical function of its liver. Moreover, within bone marrow, only rigorously purified hematopoietic stem cells gave rise to donor-derived hematopoietic and hepatic regeneration. This result seems to contradict the conventional assumptions of the germ layer origins of tissues such as the liver, and raises the question of whether the cells of the hematopoietic stem cell phenotype are pluripotent hematopoietic cells that retain the ability to transdifferentiate, or whether they are more primitive multipotent cells.  相似文献
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Simian virus 40 gene A function and maintenance of transformation.   总被引:107,自引:70,他引:37       下载免费PDF全文
Transformants have been isolated after infection of rat embryo cells at 33 C with either wild-type simian virus 40 or with the temperature-sensitive gene A mutants, tsA7 and tsA28. Examination of properties usually associated with transformation such as growth in 1% serum, growth rate, saturation density, and morphology show that these properties are temperature dependent in the tsA transformants characterized, but are not temperature dependent in the wild-type transformants that have been examined. In the most thoroughly characterized tsA transformants the expression of T antigen also appears to be temperature dependent. These data suggest that an active A function is required for the maintenance of transformation in these cells. In the lytic cycle, the A function is involved in the initiation of DNA synthesis. Thus transformation by simian virus 40 may be the direct consequence of the introduction of the simian virus 40 replicon and the presence of its DNA initiator function, which causes the cell to express a transformed phenotype.  相似文献
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The display of microtubules in transformed cells.   总被引:48,自引:0,他引:48  
M Osborn  K Weber 《Cell》1977,12(3):561-571
Monospecific tubulin antibodies have been used in indirect immunofluorescence microscopy on a variety of well characterized, transformed cell lines grown in tissue culture. Networks of colcemid-sensitive fibers are seen in SV40-transformed 3T3 cells, SV40-transformed rat embryo cells, HeLa cells and other transformed cell lines. In each case, greater than 90% of the cells contain visible microtubular networks, and where individual microtubules can be distinguished, they run for long distances. Documentation of these metworks is more difficult in transformed than in normal cells, because transformed cells are in general more rounded and have less well spread cytoplasm. In addition, the microtubular networks can be readily visualized in "cytoskeletons" of both normal and transformed cells, obtained by treatment of cells with nonionic detergents in a buffer which stabilizes microtubules in vitro. Addition of calcium to this buffer results in in situ fragmentation and destruction of the microtubular network. In view of these results, we conclude that transformed cells contain significant numbers of microtubules, and that in transformed cells, as in normal cells, microtubules are arranged in networks.  相似文献
7.
Intermediate-sized filaments of the prekeratin type in myoepithelial cells   总被引:38,自引:14,他引:24  
Myoepithelial cells from mammary glands, the modified sweat glands of bovine muzzle, and salivary glands have been studied by electron microscopy and by immunofluorescence microscopy in frozen sections in an attempt to further characterize the type of intermediate-sized filaments present in these cells. Electron microscopy has shown that all myoepithelial cells contain extensive meshworks of intermediate-sized (7--11-nm) filaments, many of which are anchored at typical desmosomes or hemidesmosomes. The intermediate-sized filaments are also intimately associated with masses of contractile elements, identified as bundles of typical 5--6-nm microfilaments and with characteristically spaced dense bodies. This organization resembles that described for various smooth muscle cells. In immunofluorescence microscopy, using antibodies specific for the various classes of intermediate-sized filaments, the myoepithelial cells are strongly decorated by antibodies to prekeratin. They are not specifically stained by antibodies to vimentin, which stain mesenchymal cells, nor by antibodies to chick gizzard desmin, which decorate fibrils in smooth muscle Z bands and intercalated disks in skeletal and cardiac muscle of mammals. Myoepithelial cells are also strongly stained by antibodies to actin. The observations show (a) that the epithelial character, as indicated by the presence of intermediate-sized filaments of the prekeratin type, is maintained in the differentiated contractile myoepithelial cell, and (b) that desmin and desmin-containing filaments are not generally associated with musclelike cell specialization for contraction but are specific to myogenic differentiation. The data also suggest that in myoepithelial cells prekeratin filaments are arranged--and might function--in a manner similar to the desmin filaments in smooth muscle cells.  相似文献
8.
mAbs specific for titin or nebulin were characterized by immunoblotting and fluorescence microscopy. Immunoelectron microscopy on relaxed chicken breast muscle revealed unique transverse striping patterns. Each of the 10 distinct titin antibodies provided a pair of delicate decoration lines per sarcomere. The position of these pairs was centrally symmetric to the M line and was antibody dependent. The results provided a linear epitope map, which starts at the Z line (antibody T20), covers five distinct positions along the I band (T21, T12, T4, T1, T11), the A-I junction (T3), and three distinct positions within the A band (T10, T22, T23). The epitope of T23 locates 0.2 micron before the M line. In immunoblots, the two antibodies decorating at or just before the Z line (T20, T21) specifically recognized the insoluble titin TI component but did not recognize TII, a proteolytic derivative. All other titin antibodies recognized TI and TII. Thus titin molecules appear as polar structures lacking over large regions repetitive epitopes. One physical end seems related to Z line anchorage, while the other may bind close to the M line. Titin epitopes influenced by the contractional state of the sarcomere locate between the N1 line and the A-I junction (T4, T1, T11). We discuss the results in relation to titin molecules having half-sarcomere lengths. The three nebulin antibodies so far characterized again give rise to distinct pairs of stripes. These locate close to the N2 line.  相似文献
9.
E Debus  K Weber  M Osborn 《Differentiation》1983,25(2):193-203
A panel of 10 mouse monoclonal antibodies specific for glial fibrillary acidic protein (GFA) has been isolated using porcine GFA as antigen. Although all antibodies recognize GFA purified from porcine spinal cord in the western blot technique, they can be subdivided into at least three groups on the basis of their reactivity against defined fragments of the molecule. Immunofluorescence staining patterns with the monoclonal antibodies performed on tissues and cell lines resemble those reported with conventional polyclonal antibodies directed against GFA. In particular astrocytes and Bergmann glia are strongly stained. In addition mouse monoclonal antibodies specific for either the 200 kd, or the 160 kd, or the 68 kd neurofilament triplet protein have been isolated and characterized. These antibodies are specific for neuronal cells and support conclusions made with similar antigen affinity-purified polyclonal antibodies. The combined set of monoclonal antibodies seems a valuable tool to characterize the different cell types of the nervous system.  相似文献
10.
In mouse embryos, acquisition of the nuclear lamin polypeptides A/C varies according to developmental stage and tissue type. In order to determine the precise time points and cell types in which lamin A/C are first observed, we have used two monoclonal antibodies in immunofluorescence studies of different tissues of developing mouse embryos and of young mice. One antibody (mAB346) is specific for lamins A and C, while the other (PKB8) detects lamins A, B and C. Dividing uterine development into three phases--germ layer formation, organogenesis and tissue differentiation--our results show that lamin A/C expression in the embryo proper is not observed until the third phase of development. Lamin A/C first appears at embryonic day 12 in muscle cells of the trunk, head and the appendages. Three days later it is also seen in cells of the epidermis where its appearance coincides with the time of stratification. In the simple epithelial of lung, liver, kidney and intestine, as well as in heart and brain, lamins A/C do not appear until well after birth. Embryonal carcinoma (EC) cells express lamin B but not lamin A/C. Lamin A/C expression is noted in some EC cells after they are induced to differentiate and in several differentiated teratocarcinoma cell lines. Our results suggest that commitment of a cell to a particular pathway of differentiation (assayed by cell-type-specific expression of intermediate filament proteins) usually occurs prior to the time that lamin A/C can be detected. Thus lamin A/C expression may serve as a limit on the plasticity of cells for further developmental events.  相似文献
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