全文获取类型
收费全文 | 91篇 |
免费 | 6篇 |
出版年
2023年 | 2篇 |
2020年 | 3篇 |
2019年 | 7篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 8篇 |
2014年 | 7篇 |
2013年 | 7篇 |
2012年 | 7篇 |
2011年 | 9篇 |
2010年 | 2篇 |
2009年 | 2篇 |
2008年 | 2篇 |
2007年 | 4篇 |
2006年 | 1篇 |
2005年 | 1篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1993年 | 2篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1966年 | 1篇 |
1960年 | 2篇 |
1927年 | 1篇 |
排序方式: 共有97条查询结果,搜索用时 15 毫秒
51.
Li Liu Nidia MM Oliveira Kelly M Cheney Corinna Pade Hanna Dreja Ann-Marie H Bergin Viola Borgdorff David H Beach Cleo L Bishop Matthias T Dittmar Áine McKnight 《Retrovirology》2011,8(1):1-15
Background
Human T-cell leukemia virus type 1 (HTLV-1) causes adult T-cell leukemia (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) in a small percentage of infected individuals. ATL is often associated with general immune suppression and an impaired HTLV-1-specific T-cell response, an important host defense system. We previously found that a small fraction of asymptomatic HTLV-1-carriers (AC) already showed impaired T-cell responses against the major target antigen, Tax. However, it is unclear whether the impaired HTLV-1 Tax-specific T-cell response in these individuals is an HTLV-1-specific phenomenon, or merely reflects general immune suppression. In this study, in order to characterize the impaired HTLV-1-specific T-cell response, we investigated the function of Tax-specific CD8+ T-cells in various clinical status of HTLV-1 infection.Results
By using tetramers consisting of HLA-A*0201, -A*2402, or -A*1101, and corresponding Tax epitope peptides, we detected Tax-specific CD8+ T-cells in the peripheral blood from 87.0% of ACs (n = 20/23) and 100% of HAM/TSP patients (n = 18/18) tested. We also detected Tax-specific CD8+ T-cells in 38.1% of chronic type ATL (cATL) patients (n = 8/21), although its frequencies in peripheral blood CD8+ T cells were significantly lower than those of ACs or HAM/TSP patients. Tax-specific CD8+ T-cells detected in HAM/TSP patients proliferated well in culture and produced IFN-γ when stimulated with Tax peptides. However, such functions were severely impaired in the Tax-specific CD8+ T-cells detected in cATL patients. In ACs, the responses of Tax-specific CD8+ T-cells were retained in most cases. However, we found one AC sample whose Tax-specific CD8+ T-cells hardly produced IFN-γ, and failed to proliferate and express activation (CD69) and degranulation (CD107a) markers in response to Tax peptide. Importantly, the same AC sample contained cytomegalovirus (CMV) pp65-specific CD8+ T-cells that possessed functions upon CMV pp65 peptide stimulation. We further examined additional samples of two smoldering type ATL patients and found that they also showed dysfunctions of Tax-specific but not CMV-specific CD8+ T-cells.Conclusions
These findings indicated that Tax-specific CD8+ T-cells were scarce and dysfunctional not only in ATL patients but also in a limited AC population, and that the dysfunction was selective for HTLV-1-specifc CD8+ T-cells in early stages. 相似文献52.
53.
MM Fierro L Cruz-López D Sánchez R Villanueva-Gutiérrez R Vandame 《Neotropical Entomology》2012,41(2):95-104
We recorded stingless bee colony abundance and nesting habits in three sites with different anthropogenic activities in the Soconusco region of Chiapas, Mexico: (1) agroforestry (7 hacacao crop), (2) grassland (12?ha), and (3) urban area (3?ha). A total of 67 nests were found, representing five stingless bee species, Tetragonisca angustula angustula (Lepeletier), Trigona fulviventris (Guérin), Scaptotrigona mexicana (Guérin), Scaptotrigona pectoralis (Dalla Torre), and Oxytrigona mediorufa (Cockerell). The most abundant stingless bee in each site was T. angustula angustula (>50%). The primary tree species used by the bees were Ficus spp. (Moraceae, 37.8%) and Cordia alliodora (Boraginaceae, 13.5%). The nest entrance height of T. angustula angustula (96?±?19?cm) was different than the other species, and this bee was the only one that used all different nesting sites. Volatiles analyzed by gas chromatography from pollen collected by the stingless bees differed between bee species, but were highly similar in respect to the fragrances of the pollen collected by the same species at any site. Our data indicate that T. angustula angustula experienced low heterospecific and high intraspecific foraging overlap especially in the urban site. We observed cluster spatial distribution in grassland and in agroforestry sites. In the urban site, T. angustula angustula presented random distribution tended to disperse. Trigona fulviventris was the only overdispersed and solitary species. 相似文献
54.
Yi Sui Hai-Lu Zhao Heung Man Lee Jing Guan Lan He Fernand MM Lai Peter CY Tong Juliana CN Chan 《Translational oncology》2009,2(4):258-263
Nephrectomized rats have widely been used to study chronic renal failure. Interestingly, renal cell carcinoma occurred in the remnant kidney after uninephrectomy (UNX). In this study, we probed insulin-like growth factor (IGF)-1 signaling pathway in UNX-induced renal cancer. Adult male Sprague-Dawley rats were randomized into two groups: UNX rats (n = 22) and sham-operated rats (n = 12). Rats were killed at 3, 7, and 10 months. After 7 months after nephrectomy, the UNX rats developed renal cell carcinoma with increased expression of proliferating cell nuclear antigen, and 68.2% (15/22) of the animals exhibited invasive carcinoma. Western blot demonstrated significant down-regulation of IGF binding protein 3 contrasting with the up-regulation of protein kinase Cζ and Akt/protein kinase B in the renal cancer tissues. These findings indicate a unique rat model of UNX-induced renal cancer associated with enhanced IGF-1 signaling pathway. 相似文献
55.
Sefika C Mizrak Bart M Gadella Hatice Erdost Aytekin Ozer Ana MM van Pelt Federica MF van Dissel-Emiliani 《Reproductive biology and endocrinology : RB&E》2008,6(1):1-9
Background
The placenta is an important site for iron metabolism in humans. It transfers iron from the mother to the fetus. One of the major iron transport proteins is transferrin, which is a blood plasma protein crucial for iron uptake. Its localization and expression may be one of the markers to distinguish placental dysfunction.Methods
In the experimental study we used antibody preparation, mass spectrometric analysis, biochemical and immunocytochemical methods for characterization of transferrin expression on the human choriocarcinoma cell line JAR (JAR cells), placental lysates, and cryostat sections. Newly designed monoclonal antibody TRO-tf-01 to human transferrin was applied on human placentae from normal (n = 3) and abnormal (n = 9) pregnancies.Results
Variations of transferrin expression were detected in villous syncytiotrophoblast, which is in direct contact with maternal blood. In placentae from normal pregnancies, the expression of transferrin in the syncytium was significantly lower (p < 0.001) when compared to placentae from abnormal ones (gestational diabetes, pregnancy induced hypertension, drug abuse).Conclusion
These observations suggest that in the case of abnormal pregnancies, the fetus may require higher levels of transferrin in order to prevent iron depletion due to the stress from the placental dysfunction. 相似文献56.
Andreas Krupke Wiebke Mohr Julie LaRoche Bernhard M Fuchs Rudolf I Amann Marcel MM Kuypers 《The ISME journal》2015,9(7):1635-1647
Symbiotic relationships between phytoplankton and N2-fixing microorganisms play a crucial role in marine ecosystems. The abundant and widespread unicellular cyanobacteria group A (UCYN-A) has recently been found to live symbiotically with a haptophyte. Here, we investigated the effect of nitrogen (N), phosphorus (P), iron (Fe) and Saharan dust additions on nitrogen (N2) fixation and primary production by the UCYN-A–haptophyte association in the subtropical eastern North Atlantic Ocean using nifH expression analysis and stable isotope incubations combined with single-cell measurements. N2 fixation by UCYN-A was stimulated by the addition of Fe and Saharan dust, although this was not reflected in the nifH expression. CO2 fixation by the haptophyte was stimulated by the addition of ammonium nitrate as well as Fe and Saharan dust. Intriguingly, the single-cell analysis using nanometer scale secondary ion mass spectrometry indicates that the increased CO2 fixation by the haptophyte in treatments without added fixed N is likely an indirect result of the positive effect of Fe and/or P on UCYN-A N2 fixation and the transfer of N2-derived N to the haptophyte. Our results reveal a direct linkage between the marine carbon and nitrogen cycles that is fuelled by the atmospheric deposition of dust. The comparison of single-cell rates suggests a tight coupling of nitrogen and carbon transfer that stays balanced even under changing nutrient regimes. However, it appears that the transfer of carbon from the haptophyte to UCYN-A requires a transfer of nitrogen from UCYN-A. This tight coupling indicates an obligate symbiosis of this globally important diazotrophic association. 相似文献
57.
Resumé Les auteurs ont étudié la composition chimique (N, substances humiques, lignine) de copeaux de bois blanc exposés à l'air libre depuis 2 à 10 ans, ainsi que leur type de peuplement fongique. En l'absence de lignivore, le pH, les taux de lignine et d'N s'élèvent et il se forme des quantités modérées d'humus à forte capacité d'échange. Dans le cas contraire, on voit apparaître, en abondance, des substances humiques peu condensées et la matière organique subit une évolution rappelant celle du mor.Avec la collaboration technique de Melle. M. Clet.Kononova, dans sa monographie5, signale de Troussov (1916) une étude que nous n'avons pas eu en mains. 相似文献
58.
Studies of esterase 6 in Drosophila melanogaster. XVIII. Biochemical differences between the slow and fast allozymes 总被引:1,自引:0,他引:1
Most natural populations of Drosophila melanogaster are polymorphic for two
major electrophoretic variants at the esterase-6 locus. The frequency of
the EST 6F allozyme is greatest in populations in warmer latitudes, whereas
the EST 6S allozyme is predominant in colder latitudes. Latitudinal clines
in electromorph frequencies are found on three continents. Purified
preparations of the allozymes have been characterized for their pH optimum,
substrate specificity, organophosphate inhibition, alcohol activation,
thermal stability, and kinetic parameters. These and previous analyses of
the EST 6 allozymes reveal that the two variants have differences in their
physical and kinetic properties that may provide a basis for the selective
maintenance of the polymorphisms and an explanation of the clinal variation
observed in natural populations.
相似文献
59.
60.