全文获取类型
收费全文 | 408篇 |
免费 | 20篇 |
专业分类
428篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2021年 | 4篇 |
2020年 | 5篇 |
2019年 | 5篇 |
2018年 | 19篇 |
2017年 | 15篇 |
2016年 | 21篇 |
2015年 | 34篇 |
2014年 | 36篇 |
2013年 | 37篇 |
2012年 | 40篇 |
2011年 | 24篇 |
2010年 | 29篇 |
2009年 | 12篇 |
2008年 | 19篇 |
2007年 | 18篇 |
2006年 | 24篇 |
2005年 | 15篇 |
2004年 | 23篇 |
2003年 | 12篇 |
2002年 | 12篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1979年 | 1篇 |
1969年 | 2篇 |
1962年 | 1篇 |
1961年 | 2篇 |
排序方式: 共有428条查询结果,搜索用时 15 毫秒
21.
Isabela Resende Pereira Glaucia Vilar-Pereira Virgínia Marques Andrea Alice da Silva Bráulia Caetano Otacilio Cruz Moreira Alexandre Vieira Machado Oscar Bruna-Romero Maurício Martins Rodrigues Ricardo Tostes Gazzinelli Joseli Lannes-Vieira 《PLoS pathogens》2015,11(1)
Chagas disease (CD), caused by the protozoan Trypanosoma cruzi, is a prototypical neglected tropical disease. Specific immunity promotes acute phase survival. Nevertheless, one-third of CD patients develop chronic chagasic cardiomyopathy (CCC) associated with parasite persistence and immunological unbalance. Currently, the therapeutic management of patients only mitigates CCC symptoms. Therefore, a vaccine arises as an alternative to stimulate protective immunity and thereby prevent, delay progression and even reverse CCC. We examined this hypothesis by vaccinating mice with replication-defective human Type 5 recombinant adenoviruses (rAd) carrying sequences of amastigote surface protein-2 (rAdASP2) and trans-sialidase (rAdTS) T. cruzi antigens. For prophylactic vaccination, naïve C57BL/6 mice were immunized with rAdASP2+rAdTS (rAdVax) using a homologous prime/boost protocol before challenge with the Colombian strain. For therapeutic vaccination, rAdVax administration was initiated at 120 days post-infection (dpi), when mice were afflicted by CCC. Mice were analyzed for electrical abnormalities, immune response and cardiac parasitism and tissue damage. Prophylactic immunization with rAdVax induced antibodies and H-2Kb-restricted cytotoxic and interferon (IFN)γ-producing CD8+ T-cells, reduced acute heart parasitism and electrical abnormalities in the chronic phase. Therapeutic vaccination increased survival and reduced electrical abnormalities after the prime (analysis at 160 dpi) and the boost (analysis at 180 and 230 dpi). Post-therapy mice exhibited less heart injury and electrical abnormalities compared with pre-therapy mice. rAdVax therapeutic vaccination preserved specific IFNγ-mediated immunity but reduced the response to polyclonal stimuli (anti-CD3 plus anti-CD28), CD107a+ CD8+ T-cell frequency and plasma nitric oxide (NO) levels. Moreover, therapeutic rAdVax reshaped immunity in the heart tissue as reduced the number of perforin+ cells, preserved the number of IFNγ+ cells, increased the expression of IFNγ mRNA but reduced inducible NO synthase mRNA. Vaccine-based immunostimulation with rAd might offer a rational alternative for re-programming the immune response to preserve and, moreover, recover tissue injury in Chagas’ heart disease. 相似文献
22.
Ana L. Teixeira Francisca Dias Marta Ferreira Mónica Gomes Juliana I. Santos Francisco Lobo Joaquina Maurício José Carlos Machado Rui Medeiros 《PloS one》2015,10(4)
The epidermal growth factor (EGF) is responsible for the activation of intracellular signal transducers that act on cell-cycle progression, cell motility, angiogenesis and inhibition of apoptosis. However, cells can block these effects activating opposite signaling pathways, such as the transforming growth factor beta 1 (TGFβ1) pathway. Thus changes in expression levels of EGF and TGFB1 in renal cells might modulate the renal cell carcinoma (RCC) development, in consequence of changes in regulatory elements of signaling networks such as the microRNAs (miRNAs). Our purpose was to investigate the synergic role of EGF+61G>A and TGFB1+869T>C polymorphisms in RCC development. Genetic polymorphisms were studied by allelic discrimination using real-time PCR in 133 RCC patients vs. 443 healthy individuals. The circulating EGF/EGFR-MAPK-related miR-7, miR-221 and miR-222 expression was analyzed by a quantitative real-time PCR in plasma from 22 RCC patients vs. 27 healthy individuals. The intermediate/high genetic proliferation profile patients carriers present a significantly reduced time-to-progression and a higher risk of an early relapse compared with the low genetic proliferation profile carriers (HR = 8.8, P = 0.038) with impact in a lower overall survival (Log rank test, P = 0.047). The RCC patients presented higher circulating expression levels of miR-7 than healthy individuals (6.1-fold increase, P<0.001). Moreover, the intermediate/high genetic proliferation profile carriers present an increase in expression levels of miR-7, miR-221 and miR-222 during the RCC development and this increase is not observed in low genetic proliferation profile (P<0.001, P = 0.004, P<0.001, respectively). The stimulus to angiogenesis, cell-cycle progression and tumoral cells invasion, through activation of EGFR/MAPK signaling pathway in intermediate/high proliferation profile carriers is associated with an early disease progression, resulting in a poor overall survival. We also demonstrated that the intermediate/high proliferation profile is an unfavorable prognostic factor of RCC and miR-7, miR-221 and miR-222 expressions may be useful phenotype biomarkers of EGFR/MAPK activation. 相似文献
23.
Maurício dos Santos Pereira Matheus Figueiredo Sathler Thais da Rosa Valli Richard Souza Marques Ana Lucia Marques Ventura Ney Ronner Peccinalli Mabel Carneiro Fraga Alex C. Manh?es Regina Kubrusly 《PloS one》2015,10(10)
Methylphenidate (MPD) is one of the most prescribed drugs for alleviating the symptoms of Attention Deficit/Hyperactivity Disorder (ADHD). However, changes in the molecular mechanisms related to MPD withdrawal and susceptibility to consumption of other psychostimulants in normal individuals or individuals with ADHD phenotype are not completely understood. The aims of the present study were: (i) to characterize the molecular differences in the prefrontal dopaminergic system of SHR and Wistar strains, (ii) to establish the neurochemical consequences of short- (24 hours) and long-term (10 days) MPD withdrawal after a subchronic treatment (30 days) with Ritalin® (Methylphenidate Hydrochloride; 2.5 mg/kg orally), (iii) to investigate the dopaminergic synaptic functionality after a cocaine challenge in adult MPD-withdrawn SHR and Wistar rats. Our results indicate that SHR rats present reduced [3H]-Dopamine uptake and cAMP accumulation in the prefrontal cortex (PFC) and are not responsive to dopaminergic stimuli in when compared to Wistar rats. After a 24-hour withdrawal of MPD, SHR did not present any alterations in [3H]-Dopamine Uptake, [3H]-SCH 23390 binding and cAMP production; nonetheless, after a 10-day MPD withdrawal, the results showed a significant increase of [3H]-Dopamine uptake, of the quantity of [3H]-SCH 23390 binding sites and of cAMP levels in these animals. Finally, SHR that underwent a 10-day MPD withdrawal and were challenged with cocaine (10 mg/kg i.p.) presented reduced [3H]-Dopamine uptake and increased cAMP production. Wistar rats were affected by the 10-day withdrawal of MPD in [3H]-dopamine uptake but not in cAMP accumulation; in addition, cocaine was unable to induce significant modifications in [3H]-dopamine uptake and in cAMP levels after the 10-day withdrawal of MPD. These results indicate a mechanism that could explain the high comorbidity between ADHD adolescent patients under methylphenidate treatment and substance abuse in adult life. 相似文献
24.
Omar Mertins Isabel?O.L. Bacellar Fabrice Thalmann Carlos?M. Marques Maurício?S. Baptista Rosangela Itri 《Biophysical journal》2014,106(1):162-171
In this study we pursue a closer analysis of the photodamage promoted on giant unilamellar vesicles membranes made of dioleoyl-sn-glycero-3-phosphocholine (DOPC) or 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), by irradiating methylene blue present in the giant unilamellar vesicles solution. By means of optical microscopy and electro-deformation experiments, the physical damage on the vesicle membrane was followed and the phospholipids oxidation was evaluated in terms of changes in the membrane surface area and permeability. As expected, oxidation modifies structural characteristics of the phospholipids that lead to remarkable membrane alterations. By comparing DOPC- with POPC-made membranes, we observed that the rate of pore formation and vesicle degradation as a function of methylene blue concentration follows a diffusion law in the case of DOPC and a linear variation in the case of POPC. We attributed this scenario to the nucleation process of oxidized species following a diffusion-limited growth regime for DOPC and in the case of POPC a homogeneous nucleation process. On the basis of these premises, we constructed models based on reaction-diffusion equations that fit well with the experimental data. This information shows that the outcome of the photosensitization reactions is critically dependent on the type of lipid present in the membrane. 相似文献
25.
Maurício Papa de Arruda Evonnildo Costa Gonçalves Maria Paula Cruz Schneider Artur Luiz da Costa da Silva Eliana Morielle-Versute 《Molecular biology reports》2010,37(4):2031-2036
We proposed a modification the procedure of genotyping based in labeled universal primer and tailed primer. In the standard
protocol, three primers are used in the same PCR reaction, a forward primer with tail added at the 5′ end of the identical
sequence to labeled universal primer with dye-fluorescent and a reverse primer. Unfortunately, the choice of a labeled primer
characterized by a large number of complementary sequences in target genomes (which is more probable in larger genomes) result
in unspecific amplifications (false positive) can cause absence or decrease amplification of the locus of interest and also
false interpretation of the analysis. However, identification of possible homologies between the primer chosen for labelling
and the genome is rarely possible from the available DNA data bases. In our approach, cycling is interrupted for the addition
of the labeled primer only during the final cycles, thus minimizing unspecific amplification and competition between primers,
resulting in the more fidelity amplification of the target regions. 相似文献
26.
Ana Flávia Azevedo Carvalho Maurício Boscolo Roberto da Silva Henrique Ferreira Eleni Gomes 《Journal of microbiology (Seoul, Korea)》2010,48(4):452-459
An α-glucosidase enzyme produced by the fungus Thermoascus aurantiacus CBMAI 756 was purified by ultra filtration, ammonium sulphate precipitation, and chromatography using Q Sepharose, Sephacryl
S-200, and Superose 12 columns. The apparent molecular mass of the enzyme was 83 kDa as determined in gel electrophoresis.
Maximum activity was observed at pH 4.5 at 70°C. Enzyme showed stability stable in the pH range of 3.0–9.0 and lost 40% of
its initial activity at the temperatures of 40, 50, and 60°C. In the presence of ions Na+, Ba2+, Co2+, Ni2+, Mg2+, Mn2+, Al3+, Zn2+, Ca2+ this enzyme maintained 90–105% of its maximum activity and was inhibited by Cr3+, Ag+, and Hg2+. The enzyme showed a transglycosylation property, by the release of oligosaccharides after 3 h of incubation with maltose,
and specificity for short maltooligosaccharides and α-PNPG. The Km measured for the α-glucosidase was 0.07 μM, with a Vmax of 318.0 μmol/min/mg. 相似文献
27.
28.
A. Z. Miller M. A. Rogerio-Candelera L. Laiz J. Wierzchos C. Ascaso M. A. Sequeira Braga M. Hernández-Mariné A. Maurício A. Dionísio M. F. Macedo C. Saiz-Jimenez 《Microbial ecology》2010,60(1):55-68
This study is aimed to assess the formation of photosynthetic biofilms on and within different natural stone materials, and to analyse their biogeophysical and biogeochemical deterioration potential. This was performed by means of artificial colonisation under laboratory conditions during 3 months. Monitoring of microbial development was performed by image analysis and biofilm biomass estimation by chlorophyll extraction technique. Microscopy investigations were carried out to study relationships between microorganisms and the mineral substrata. The model applied in this work corroborated a successful survival strategy inside endolithic microhabitat, using natural phototrophic biofilm cultivation, composed by cyanobacteria and algae, which increased intrinsic porosity by active mineral dissolution. We observed the presence of mineral-like iron derivatives (e.g. maghemite) around the cells and intracellularly and the precipitation of hausmannite, suggesting manganese transformations related to the biomineralisation. 相似文献
29.
Ana-Carolina Oliveira Bruna C. de Alencar Fanny Tzelepis Weberton Klezewsky Raquel N. da Silva Fabieni S. Neves Gisele S. Cavalcanti Silvia Boscardin Marise P. Nunes Marcelo F. Santiago Alberto Nóbrega Maurício M. Rodrigues Maria Bellio 《PLoS pathogens》2010,6(4)
The murine model of T. cruzi infection has provided compelling evidence that development of host resistance against intracellular protozoans critically depends on the activation of members of the Toll-like receptor (TLR) family via the MyD88 adaptor molecule. However, the possibility that TLR/MyD88 signaling pathways also control the induction of immunoprotective CD8+ T cell-mediated effector functions has not been investigated to date. We addressed this question by measuring the frequencies of IFN-γ secreting CD8+ T cells specific for H-2Kb-restricted immunodominant peptides as well as the in vivo Ag-specific cytotoxic response in infected animals that are deficient either in TLR2, TLR4, TLR9 or MyD88 signaling pathways. Strikingly, we found that T. cruzi-infected Tlr2−/−, Tlr4−/−, Tlr9−/
− or Myd88−/− mice generated both specific cytotoxic responses and IFN-γ secreting CD8+ T cells at levels comparable to WT mice, although the frequency of IFN-γ+CD4+ cells was diminished in infected Myd88−/− mice. We also analyzed the efficiency of TLR4-driven immune responses against T. cruzi using TLR4-deficient mice on the C57BL genetic background (B6 and B10). Our studies demonstrated that TLR4 signaling is required for optimal production of IFN-γ, TNF-α and nitric oxide (NO) in the spleen of infected animals and, as a consequence, Tlr4−/− mice display higher parasitemia levels. Collectively, our results indicate that TLR4, as well as previously shown for TLR2, TLR9 and MyD88, contributes to the innate immune response and, consequently, resistance in the acute phase of infection, although each of these pathways is not individually essential for the generation of class I-restricted responses against T. cruzi. 相似文献
30.
Juliane Ventura-Lima Micheli Rosa de Castro Daiane Acosta Daniele Fattorini Francesco Regoli Leandro Machado de Carvalho Denise Bohrer Laura A. Geracitano Daniela Martí Barros Luis F.F. Marins Rosane Souza da Silva Carla Denise Bonan Maurício Reis Bogo José M. Monserrat 《Comparative biochemistry and physiology. Toxicology & pharmacology : CBP》2009,149(4):538-543
In fishes, arsenic (As) is absorbed via the gills and is capable of causing disturbance to the antioxidant system. The objective of present study was to evaluate antioxidant responses after As exposure in gills of zebrafish (Danio rerio, Cyprinidae). Fish were exposed for 48 h to three concentration of As, including the highest As concentration allowed by current Brazilian legislation (10 μg As/L). A control group was exposed to tap water (pH 8.0; 26 °C; 7.20 mg O2/L). As exposure resulted in (1) an increase (p < 0.05) of glutathione (GSH) levels after exposure to 10 and 100 μg As/L, (2) an increase of the glutamate cysteine ligase (GCL) activity in the same concentrations (p < 0.05), (3) no significant differences in terms of glutathione reductase, glutathione-S-transferase and catalase activities; (4) a significantly lower (p < 0.05) oxygen consumption after exposure to 100 μg As/L; (4) no differences in terms of oxygen reactive species generation and lipid peroxidation content (p > 0,05). In the gills, only inorganic As was detected. Overall, it can be concluded that As affected the antioxidant responses increasing GCL activity and GSH levels, even at concentration considered safe by Brazilian legislation. 相似文献