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排序方式: 共有244条查询结果,搜索用时 15 毫秒
1.
2.
Modulation of transcytotic and direct targeting pathways in a polarized thyroid cell line. 总被引:10,自引:0,他引:10
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Two biosynthetic pathways exist for delivery of membrane proteins to the apical surface of epithelial cells, direct transport from the trans-Golgi network (TGN) and transcytosis from the basolateral membrane. Different epithelial cells vary in the expression of these mechanisms. Two extremes are MDCK cells, that use predominantly the direct route and hepatocytes, which deliver all apical proteins via the basolateral membrane. To determine how epithelial cells establish a particular targeting phenotype, we studied the apical delivery of endogenous dipeptidyl peptidase IV (DPPIV) at early and late stages in the development of monolayers of a highly polarized epithelial cell line derived from Fischer rat thyroid (FRT). In 1 day old monolayers, surface delivery of DPPIV from the TGN was unpolarized (50%/50%) but a large basal to apical transcytotic component resulted in a polarized apical distribution. In contrast, after 7 days of culture, delivery of DPPIV was mainly direct (85%) with no transcytosis of the missorted component. A basolateral marker, Ag 35/40 kD, on the other hand, was directly targeted (90-98%) at all times. These results indicate that the sorting machinery for apical proteins develops independently from the sorting machinery for basolateral proteins and that the sorting site relocates progressively from the basal membrane to the TGN during development of the epithelium. The transient expression of the transcytotic pathway may serve as a salvage pathway for missorted apical proteins when the polarized phenotype is being established. 相似文献
3.
Zusammenfassung Es wird eine Übersicht über die verschiedenen Methoden zur DNS-Messung an Chromosomen gegeben. Die Methoden werden kurz beschrieben und die wichtigsten Ergebnisse der verschiedenen Autoren diskutiert.
Nach einem Referat anläßlich der 11. Tagung der Gesellschaft für Anthropologie und Humangenetik, Mainz, 7. 10. 1969.
Mit Unterstützung durch die Deutsche Forschungsgemeinschaft, AZ Mu 258/3. 相似文献
Problems of characterizing individual chromosomes by measuring the DNA content
Summary A review of the different methods of determining the DNA content of individual chromosomes is given. The methods are described briefly, and the results of the different authors are discussed.
Nach einem Referat anläßlich der 11. Tagung der Gesellschaft für Anthropologie und Humangenetik, Mainz, 7. 10. 1969.
Mit Unterstützung durch die Deutsche Forschungsgemeinschaft, AZ Mu 258/3. 相似文献
4.
Chlorogenic acid and its 2 isomers, believed to be the 4– and 5–0-caffeoylquinic acids, have been extracted from leaves of photoperiodic species of Nicotiana, separated by column chromatography (gradient elution) and measured quantitatively during the course of photoperiodic induction. In both N. tabacum cultivar ‘Maryland Mammoth’ (a short-day plant) and N. sylveslris (a long-day plant), the change of the meristem from the vegetative to the flowering shape is preceded by a rise in the chlorogenic acid content of the leaves. During the differentiation of the flower primordia in the shoot apex, there is a drop in the concentration of the chlorogenic acid in the leaves, which is especially marked in the short-day species. The levels of the 2 isomers decrease also at that time. There is no change in the ratios of the 3 caffeoylquinic acids during photoperiodic induction. In both the long- and the short-day species, the 3-isomer (chlorogenic acid) is present at the highest concentration. In the short-day species, there is more of the 4-isomer than of the 5-isomer, whereas in the long-day species, the level of the 5-isomer equals or surpasses that of the 4–0-caffeoylquinic acid. 相似文献
5.
Summary Perfusion-fixed tissue blocks were incubated in high molar sucrose solutions, shock frozen in melting isopentane, and sectioned on a conventional cryostat. Semithin sections (2–4 m) alternatingly stained for parvalbumin and glutamate decarboxylase enabled us to demonstrate the coexistence of both antigens in the same cell. Thick sections (40 m) of central and peripheral nervous system tissue were immunostained and processed for correlated light and electron microscopic studies. At the electron microscopic level, the preservation of ultrastructural features such as membranes and synaptic contacts was comparable to that normally seen in vibratome sectioned material. Hence, this technique can successfully be used for preembedding coexistence studies and electron microscopic preembedding immunocytochemistry when vibratome sectioning is problematic. 相似文献
6.
Transforming growth factor-beta induces cytoskeleton and extracellular matrix modifications in FRTL-5 thyroid epithelial cells 总被引:1,自引:0,他引:1
C Garbi G Colletta A M Cirafici P C Marchisio L Nitsch 《European journal of cell biology》1990,53(2):281-289
The action of transforming growth factor-beta (TGF-beta) on the morphology, cytoskeleton and extracellular matrix was investigated in FRTL-5 thyroid epithelial cells. After treatment with TGF-beta, FRTL-5 cells became flat and developed straight and thick bundles of actin microfilaments. This effect of TGF-beta was observed even in the presence of thyrotropin, which has a strong microfilament disrupting action. TGF-beta also influenced some aspects of the extracellular matrix organization. Immunofluorescence staining of FRTL-5 cells revealed both the appearance of a fibrillar array of fibronectin in association with the basal plasma membrane and a change in the morphology of basally located laminin patches. TGF-beta induced the formation of adhesion structures at the ventral portion of the cell membrane. Vinculin was focally concentrated at the end of stress fibers in areas corresponding to focal adhesions as revealed by interference reflection microscopy (IRM). The ability to modulate cytoskeleton organization and extracellular matrix protein distribution might mediate some of the reported TGF-beta effects on the expression of specific functional properties in thyroid cells. 相似文献
7.
Population genetics and phylogenetics of DNA sequence variation at multiple loci within the Drosophila melanogaster species complex 总被引:14,自引:1,他引:13
Two regions of the genome, a 1-kbp portion of the zeste locus and a 1.1-
kbp portion of the yolk protein 2 locus, were sequenced in six individuals
from each of four species: Drosophila melanogaster, D. simulans, D.
mauritiana, and D. sechellia. The species and strains were the same as
those of a previous study of a 1.9-kbp region of the period locus. No
evidence was found for recent balancing or directional selection or for the
accumulation of selected differences between species. Yolk protein 2 has a
high level of amino acid replacement variation and a low level of
synonymous variation, while zeste has the opposite pattern. This contrast
is consistent with information on gene function and patterns of codon bias.
Polymorphism levels are consistent with a ranking of effective population
sizes, from low to high, in the following order: D. sechellia, D.
melanogaster, D.mauritiana, and D. simulans. The apparent species
relationships are very similar to those suggested by the period locus
study. In particular, D. simulans appears to be a large population that is
still segregating variation that arose before the separation of D.
mauritiana and D. sechellia. It is estimated that the separation of
ancestral D. melanogaster from the other species occurred 2.5-3.4 Mya. The
separations of D. sechellia and D. mauritiana from ancestral D. simulans
appear to have occurred 0.58- 0.86 Mya, with D. mauritiana having diverged
from ancestral D. simulans 0.1 Myr more recently than D. sechellia.
相似文献
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