全文获取类型
收费全文 | 121篇 |
免费 | 0篇 |
出版年
2021年 | 1篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2017年 | 5篇 |
2016年 | 12篇 |
2015年 | 2篇 |
2014年 | 1篇 |
2013年 | 5篇 |
2012年 | 5篇 |
2011年 | 6篇 |
2010年 | 2篇 |
2009年 | 4篇 |
2008年 | 1篇 |
2007年 | 7篇 |
2006年 | 4篇 |
2005年 | 2篇 |
2004年 | 7篇 |
2003年 | 4篇 |
2002年 | 2篇 |
2001年 | 8篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 1篇 |
1967年 | 1篇 |
1965年 | 2篇 |
排序方式: 共有121条查询结果,搜索用时 15 毫秒
21.
A comparative study of amitotic division activity of trophoblast cells by constriction or extrusion in the blastocysts of American mink during the period of obligatory implantation delay was performed. The frequency of occurrence of amitotic figures was found to be approximately 10% upon the resumption of blastocyst growth (the blastocyst size was 0.4 mm in diameter) and nearly 20% at the stage of active growth (0.9 mm) and at the stage of expansion before blastocyst attachment to the uterine wall (1.7 mm). The ratios between the frequencies of division by extrusion and constriction at these three stages were 2 : 1, 5 : 1, and 4 : 1, respectively. We suggest that the cells produced via different forms of amitosis ways play different roles in trophoblast differentiation. 相似文献
22.
Isakova NP 《Parazitologiia》2011,45(5):358-366
Dynamic of the reproduction of the trematodes Notocotylus imbricatus (Notocotylidae), Echinostoma caproni (Echinostomatidae), Sphaeridiotrema globulus and Psilotrema tuberculata (Psilostomatidae) parthenites was observed. The formation of generative cells takes place only as a result of undifferentiated cells proliferation and following differentiation. These processes and early stages of embryogenesis are taking place only in the special reproductive organ--germinal mass. The germinal mass is always formed at the posterior part of the body. The process of reproduction had been finishing to the beginning of the generating of cercariaea of new age by parthenites. Rediae of different generations in fact stop producing new generative cells with the beginning of the appearance of a new generation. 相似文献
23.
Iryna A. Isakova Calvin Lanclos Julie Bruhn Marcelo J. Kuroda Kate C. Baker Veena Krishnappa Donald G. Phinney 《PloS one》2014,9(1)
The emerging paradigm that MSCs are immune privileged has fostered the use of “off-the-shelf” allogeneic MSC-based therapies in human clinical trials. However, this approach ignores studies in experimental animals wherein transplantation of MSCs across MHC boundaries elicits measurable allo-immune responses. To determine if MSCs are hypo-immunogeneic, we characterized the immune response in rhesus macaques following intracranial administration of allogeneic vs. autologous MSCs. This analysis revealed unambiguous evidence of productive allo-recognition based on expansion of NK, B and T cell subsets in peripheral blood and detection of allo-specific antibodies in animals administered allogeneic but not autologous MSCs. Moreover, the degree of MHC class I and II mismatch between the MSC donor and recipient significantly influenced the magnitude and nature of the allo-immune response. Consistent with these findings, real-time PCR analysis of brain tissue from female recipients administered varying doses of male, allogeneic MSCs revealed a significant inverse correlation between MSC engraftment levels and cell dose. Changes in post-transplant neutrophil and lymphocyte counts also correlated with dose and were predictive of overall MSC engraftment levels. However, secondary antigen challenge failed to elicit a measurable immune response in allogeneic recipients. Finally, extensive behavior testing of animals revealed no main effect of cell dose on motor skills, social development, or temperament. Collectively, these data indicate that allogeneic MSCs are weakly immunogenic when transplanted across MHC boundaries in rhesus macaques and this negatively impacts durable engraftment levels. Therefore the use of unrelated donor MSCs should be carefully evaluated in human patients. 相似文献
24.
25.
According to cytophotometry, trophoblast cells in the mink placenta are both diploid and polyploid, the ploidy level ranging from 2c to 64c. A great number of mink trophoblast cells were seen to divide mitotically. In addition to the ordinary mitotic figures, polyploid mitoses as well as abnormal mitotic figures were observed. Non-classic polytene chromosomes, peculiar to the mammalian trophoblast, appeared in the mink trophoblast cells to have the highest ploidy. A relatively low ploidy degree is due, probably, to a lesser invasive activity of the mink trophoblast cells as compared to the rodent giant trophoblast cells. 相似文献
26.
The evolutionary origin of the pinnipeds (seals, sea lions, and walruses)
is still uncertain. Most authors support a hypothesis of a monophyletic
origin of the pinnipeds from a caniform carnivore. A minority view suggests
a diphyletic origin with true seals being related to the mustelids (otters
and ferrets). The phylogenetic relationships of the walrus to other
pinniped and carnivore families are also still particularly problematic.
Here we examined the relative support for mono- and diphyletic hypotheses
using DNA sequence data from the mitochondrial small subunit (12S) rRNA and
cytochrome b genes. We first analyzed a small group of taxa representing
the three pinniped families (Phocidae, Otariidae, and Odobenidae) and
caniform carnivore families thought to be related to them. We inferred
phylogenetic reconstructions from DNA sequence data using standard
parsimony and neighbor-joining algorithms for phylogenetic inference as
well as a new method called spectral analysis (Hendy and Penny) in which
phylogenetic information is displayed independently of any selected tree.
We identified and compensated for potential sources of error known to lead
to selection of incorrect phylogenetic trees. These include sampling error,
unequal evolutionary rates on lineages, unequal nucleotide composition
among lineages, unequal rates of change at different sites, and
inappropriate tree selection criteria. To correct for these errors, we
performed additional transformations of the observed substitution patterns
in the sequence data, applied more stringent structural constraints to the
analyses, and included several additional taxa to help resolve long,
unbranched lineages in the tree. We find that there is strong support for a
monophyletic origin of the pinnipeds from within the caniform carnivores,
close to the bear/raccoon/panda radiation. Evidence for a diphyletic origin
was very weak and can be partially attributed to unequal nucleotide
compositions among the taxa analyzed. Subsequently, there is slightly more
evidence for grouping the walrus with the eared seals versus the true
seals. A more conservative interpretation, however, is that the walrus is
an early, but not the first, independent divergence from the common
pinniped ancestor.
相似文献
27.
28.
29.
Anna N. Tevyashova Elena N. Bychkova Alexander M. Korolev Elena B. Isakova Elena P. Mirchink Ilya A. Osterman Réka Erdei Zsolt Szücs Gyula Batta 《Bioorganic & medicinal chemistry letters》2019,29(2):276-280
One of the promising directions of the combined approach is the design of dual-acting antibiotics – heterodimeric structures on the basis of antimicrobial agents of different classes. In this study a novel series of azithromycin-glycopeptide conjugates were designed and synthesized. The structures of the obtained compounds were confirmed using NMR spectroscopy and mass spectrometry data including MS/MS analysis. All novel hybrid antibiotics were found to be either as active as azithromycin and vancomycin against Gram-positive bacterial strains or have superior activity in comparison with their parent antibiotics. One compound, eremomycin-azithromycin conjugate 16, demonstrated moderate activity against Enterococcus faecium and Enterococcus faecalis strains resistant to vancomycin, and equal to vancomycin’s activity for the treatment of mice with Staphylococcus aureus sepsis. 相似文献
30.
Currently available information on properties and regulation of mitochondrial Ca2+ transporting systems in eukaryotic cells is summarized. We describe in detail kinetic properties and effects of inhibitors and modulators on the energy-dependent Ca2+ uptake through the Ca2+ uniporter, as well as on Na+-dependent and Na+-independent pathways for Ca2+ release in mammalian mitochondria. Special emphasis is placed on Ca2+ transport systems (for ion uptake and release) in mitochondria of higher plants, algae, and yeasts. Potential physiological implications of mitochondrial Ca2+ fluxes (influx and efflux), e.g., regulation of activity of Ca2+-dependent enzymes of the Krebs cycle, maintaining of cellular Ca2+ homeostasis, and engagement in pathophysiological processes, are discussed. 相似文献