全文获取类型
收费全文 | 246篇 |
免费 | 19篇 |
专业分类
265篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 6篇 |
2018年 | 3篇 |
2017年 | 7篇 |
2016年 | 4篇 |
2015年 | 16篇 |
2014年 | 17篇 |
2013年 | 22篇 |
2012年 | 13篇 |
2011年 | 24篇 |
2010年 | 19篇 |
2009年 | 12篇 |
2008年 | 15篇 |
2007年 | 16篇 |
2006年 | 8篇 |
2005年 | 14篇 |
2004年 | 15篇 |
2003年 | 4篇 |
2002年 | 2篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 9篇 |
1997年 | 1篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有265条查询结果,搜索用时 15 毫秒
51.
Karen CM Moraes Lívia F Diniz Maria Terezinha Bahia 《Memórias do Instituto Oswaldo Cruz》2015,110(2):181-191
Chagas disease, caused by the intracellular protozoan Trypanosoma
cruzi, is a serious health problem in Latin America. During this
parasitic infection, the heart is one of the major organs affected. The pathogenesis
of tissue remodelling, particularly regarding cardiomyocyte behaviour after parasite
infection and the molecular mechanisms that occur immediately following parasite
entry into host cells are not yet completely understood. When cells are infected with
T. cruzi, they develop an inflammatory response, in which
cyclooxygenase-2 (COX-2) catalyses rate-limiting steps in the arachidonic acid
pathway. However, how the parasite interaction modulates COX-2 activity is poorly
understood. In this study, the H9c2 cell line was used as our model and we
investigated cellular and biochemical aspects during the initial 48 h of parasitic
infection. Oscillatory activity of COX-2 was observed, which correlated with the
control of the pro-inflammatory environment in infected cells. Interestingly,
subcellular trafficking was also verified, correlated with the control of Cox-2 mRNA
or the activated COX-2 protein in cells, which is directly connected with the
assemble of stress granules structures. Our collective findings suggest that in the
very early stage of the T. cruzi-host cell interaction, the parasite
is able to modulate the cellular metabolism in order to survives. 相似文献
52.
53.
Background
Influenza pandemic remains a serious threat to human health. Viruses of avian origin, H5N1, H7N7 and H9N2, have repeatedly crossed the species barrier to infect humans. Recently, a novel strain originated from swine has evolved to a pandemic. This study aims at improving our understanding on the pathogenic mechanism of influenza viruses, in particular the role of non-structural (NS1) protein in inducing pro-inflammatory and apoptotic responses.Methods
Human lung epithelial cells (NCI-H292) was used as an in-vitro model to study cytokine/chemokine production and apoptosis induced by transfection of NS1 mRNA encoded by seven infleunza subtypes (seasonal and pandemic H1, H2, H3, H5, H7, and H9), respectively.Results
The results showed that CXCL-10/IP10 was most prominently induced (> 1000 folds) and IL-6 was slightly induced (< 10 folds) by all subtypes. A subtype-dependent pattern was observed for CCL-2/MCP-1, CCL3/MIP-1α, CCL-5/RANTES and CXCL-9/MIG; where induction by H5N1 was much higher than all other subtypes examined. All subtypes induced a similar temporal profile of apoptosis following transfection. The level of apoptosis induced by H5N1 was remarkably higher than all others. The cytokine/chemokine and apoptosis inducing ability of the 2009 pandemic H1N1 was similar to previous seasonal strains.Conclusions
In conclusion, the NS1 protein encoded by H5N1 carries a remarkably different property as compared to other avian and human subtypes, and is one of the keys to its high pathogenicity. NCI-H292 cells system proves to be a good in-vitro model to delineate the property of NS1 proteins.54.
Lectins were extracted from the surface of nitrogen-fixing soil bacteria Azospirillum brasilense Sp7 and from its mutant A. brasilense Sp7.2.3 defective in lectin activity. The ability of lectins to stimulate the rapid formation of hydrogen peroxide related
to increase of oxalate oxidase and peroxidase activity in the roots of wheat seedlings has been demonstrated. The most rapid
induced pathway of hydrogen peroxide formation in the roots of wheat seedlings was the oxalic acid oxidation by oxalate oxidase
which is the effect of lectin in under 10 min in a concentration of 10 μg/ml. The obtained results show that lectins from
Azospirillum are capable of inducing the adaptation processes in the roots of wheat seedlings. 相似文献
55.
56.
Mitochondrial DNA (mtDNA) control region (CR) of numerous species is known to include up to five different repetitive sequences (RS1-RS5) that are found at various locations, involving motifs of different length and extensive length heteroplasmy. Two repetitive sequences (RS2 and RS3) on opposite sides of mtDNA central conserved region have been described in domestic cat (Felis catus) and some other felid species. However, the presence of repetitive sequence RS3 has not been detected in Eurasian lynx (Lynx lynx) yet. We analyzed mtDNA CR of 35 Eurasian lynx (L. lynx L.) samples to characterize repetitive sequences and to compare them with those found in other felid species. We confirmed the presence of 80 base pairs (bp) repetitive sequence (RS2) at the 5' end of the Eurasian lynx mtDNA CR L strand and for the first time we described RS3 repetitive sequence at its 3' end, consisting of an array of tandem repeats five to ten bp long. We found that felid species share similar RS3 repetitive pattern and fundamental repeat motif TACAC. 相似文献
57.
Changes in agonist-antagonist EMG, muscle CSA, and force during strength training in middle-aged and older people 总被引:8,自引:0,他引:8
Hakkinen K.; Kallinen M.; Izquierdo M.; Jokelainen K.; Lassila H.; Malkia E.; Kraemer W. J.; Newton R. U.; Alen M. 《Journal of applied physiology》1998,84(4):1341-1349
Effects of 6 mo of heavy-resistance trainingcombined with explosive exercises on neural activation of the agonistand antagonist leg extensors, muscle cross-sectional area (CSA) of thequadriceps femoris, as well as maximal and explosive strength wereexamined in 10 middle-aged men (M40; 42 ± 2 yr), 11 middle-agedwomen (W40; 39 ± 3 yr), 11 elderly men (M70; 72 ± 3 yr) and 10 elderly women (W70; 67 ± 3 yr). Maximal andexplosive strength remained unaltered during a 1-mo control period withno strength training. After the 6 mo of training, maximal isometric anddynamic leg-extension strength increased by 36 ± 4 and 22 ± 2%(P < 0.001) in M40, by 36 ± 3 and 21 ± 3% (P < 0.001) in M70,by 66 ± 9 and 34 ± 4% (P < 0.001) in W40, and by 57 ± 10 and 30 ± 3%(P < 0.001) in W70, respectively.All groups showed large increases (P < 0.05-0.001) in the maximum integrated EMGs (iEMGs) of theagonist vastus lateralis and medialis. Significant(P < 0.05-0.001) increasesoccurred in the maximal rate of isometric force productionand in a squat jump that were accompanied with increased(P < 0.05-0.01) iEMGs of theleg extensors. The iEMG of the antagonist biceps femoris muscle duringthe maximal isometric leg extension decreased in both M70 (from 24 ± 6 to 21 ± 6%; P < 0.05)and in W70 (from 31 ± 9 to 24 ± 4%;P < 0.05) to the same level asrecorded for M40 and W40. The CSA of the quadriceps femoris increasedin M40 by 5% (P < 0.05), in W40 by9% (P < 0.01), in W70 by 6%(P < 0.05), and in M70 by 2% (notsignificant). Great training-induced gains in maximal and explosivestrength in both middle-aged and elderly subjects were accompanied bylarge increases in the voluntary activation of the agonists, withsignificant reductions in the antagonist coactivation in the elderlysubjects. Because the enlargements in the muscle CSAs in bothmiddle-aged and elderly subjects were much smaller in magnitude, neuraladaptations seem to play a greater role in explaining strength andpower gains during the present strength-training protocol. 相似文献
58.
Two novel 4‐substituted camphidine derivatives 10a , b have been prepared from (+)‐camphor ( 1 ) in five steps, the Beckmann rearrangement being the bottleneck of the synthesis. Isoborneol derivative 5b , formed as a side product during the hydrogenation of arylidene ketone 3b , under Beckmann rearrangement conditions yielded interesting novel rearrangement products 11 and 12 . (1S)‐(+)‐Camphorquinone ( 13 ) was transformed into diamines 15 and 16 in two steps, the former being cyclized into an imidazoline salt 17 , an N‐heterocyclic carbene precursor. The structures of all novel compounds have been meticulously characterized using NMR techniques and/or single crystal X‐ray analysis. Chirality 24:778–788, 2012. © 2012 Wiley Periodicals, Inc. 相似文献
59.
BAC libraries construction from the ancestral diploid genomes of the allotetraploid cultivated peanut 总被引:1,自引:0,他引:1
Patricia M Guimarães Olivier Garsmeur Karina Proite Soraya CM Leal-Bertioli Guilhermo Seijo Christian Chaine David J Bertioli Angelique D'Hont 《BMC plant biology》2008,8(1):14
Background
Cultivated peanut, Arachis hypogaea is an allotetraploid of recent origin, with an AABB genome. In common with many other polyploids, it seems that a severe genetic bottle-neck was imposed at the species origin, via hybridisation of two wild species and spontaneous chromosome duplication. Therefore, the study of the genome of peanut is hampered both by the crop's low genetic diversity and its polyploidy. In contrast to cultivated peanut, most wild Arachis species are diploid with high genetic diversity. The study of diploid Arachis genomes is therefore attractive, both to simplify the construction of genetic and physical maps, and for the isolation and characterization of wild alleles. The most probable wild ancestors of cultivated peanut are A. duranensis and A. ipaënsis with genome types AA and BB respectively.Results
We constructed and characterized two large-insert libraries in Bacterial Artificial Chromosome (BAC) vector, one for each of the diploid ancestral species. The libraries (AA and BB) are respectively c. 7.4 and c. 5.3 genome equivalents with low organelle contamination and average insert sizes of 110 and 100 kb. Both libraries were used for the isolation of clones containing genetically mapped legume anchor markers (single copy genes), and resistance gene analogues.Conclusion
These diploid BAC libraries are important tools for the isolation of wild alleles conferring resistances to biotic stresses, comparisons of orthologous regions of the AA and BB genomes with each other and with other legume species, and will facilitate the construction of a physical map.60.
Gert Jan Boender Gonnie Nodelijk Thomas J Hagenaars Armin RW Elbers Mart CM de Jong 《BMC veterinary research》2008,4(1):9