全文获取类型
收费全文 | 5810篇 |
免费 | 374篇 |
国内免费 | 1篇 |
专业分类
6185篇 |
出版年
2024年 | 8篇 |
2023年 | 54篇 |
2022年 | 120篇 |
2021年 | 228篇 |
2020年 | 150篇 |
2019年 | 180篇 |
2018年 | 214篇 |
2017年 | 212篇 |
2016年 | 287篇 |
2015年 | 366篇 |
2014年 | 418篇 |
2013年 | 484篇 |
2012年 | 513篇 |
2011年 | 448篇 |
2010年 | 275篇 |
2009年 | 220篇 |
2008年 | 307篇 |
2007年 | 258篇 |
2006年 | 234篇 |
2005年 | 197篇 |
2004年 | 198篇 |
2003年 | 159篇 |
2002年 | 155篇 |
2001年 | 78篇 |
2000年 | 54篇 |
1999年 | 55篇 |
1998年 | 31篇 |
1997年 | 21篇 |
1996年 | 17篇 |
1995年 | 12篇 |
1994年 | 14篇 |
1993年 | 10篇 |
1992年 | 21篇 |
1991年 | 18篇 |
1990年 | 14篇 |
1989年 | 16篇 |
1988年 | 15篇 |
1987年 | 14篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1984年 | 8篇 |
1983年 | 12篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1975年 | 5篇 |
1973年 | 4篇 |
1970年 | 4篇 |
1969年 | 9篇 |
1968年 | 5篇 |
1965年 | 5篇 |
排序方式: 共有6185条查询结果,搜索用时 9 毫秒
81.
Vanessa A. Belo Marcelo R. Luizon Patrícia C. Carneiro Valéria A. Gomes Riccardo Lacchini Carla M. M. Lanna Debora C. Souza-Costa Jose E. Tanus-Santos 《Molecular biology reports》2013,40(3):2697-2704
Matrix metalloproteinase-2 is involved in the development of the adipose tissue, and associated with cardiovascular diseases. Metabolic risk factors (MRFs) and functional polymorphisms in the MMP-2 gene may affect its expression and activity. We investigated whether traditional MRFs and two MMP-2 gene polymorphisms (C?1306T; rs243865, and C?735T; rs2285053) affect circulating MMP-2 levels in children and adolescents, and whether MMP-2 polymorphisms and/or haplotype are associated with susceptibility to childhood obesity. We studied 114 healthy controls, 43 obese, and 83 obese with ≥3 MRFs children and adolescents. Genotypes were determined by Taqman allele discrimination assay and real-time PCR. Plasma MMP-2 was measured using zymography. We found positive correlations between MMP-2 concentrations and mean blood pressure in all children and adolescents group (r = 0.132; P < 0.05) and in obese children and adolescents (r = 0.247; P < 0.01). We found that the CC genotype for the C?1306T polymorphism was more common in subjects with higher MMP-2 concentrations in controls (P = 0.003) and in the obese group (P = 0.013). The CT genotype (OR = 0.40; P < 0.01) and the T allele (OR = 0.48; P < 0.01) for the C?735T polymorphism were less common in obese children and adolescents than in controls. The haplotypes distribution did not show significant differences between control and obese (P > 0.05). Ours findings show that blood pressure is associated with circulating MMP-2 concentrations, and that the CC genotype for the C?1306T polymorphism was more common subjects (controls and obese) with higher MMP-2 concentrations, whereas the CT genotype and the T allele for the C?735T polymorphism are less common in obesity. 相似文献
82.
Kelly C. M. C. Pedroza Sócrates B. de Matos Daniel L. de Moura Mônica B. B. Oliveira Marco A. S. Araújo Roberto J. M. Nascimento Fernanda W. M. Lima 《Mycopathologia》2013,176(3-4):295-297
Galactomannan (GM) was recently included in consensus guidelines as an indirect mycological criterion for the diagnosis of invasive aspergillosis. Currently, there is an enzyme immunoassay available to detect GM in biological samples, the Platelia? Aspergillus EIA. In this study, the reproducibility of positive results obtained using this assay was evaluated using serum samples from neutropenic patients. A trend toward lower values was observed, and 55 %(27/49) of positive results were negative after retesting. A low reproducibility of positive results for the detection of GM in serum was observed. 相似文献
83.
Jovana Karoline Lima Neiva Leite Luciane Viater Turek Ricardo Lehtonen Rodrigues Souza Luciana da Silva Timossi Ana Claudia Vecchi Osiecki Raul Osiecki Lupe Furtado-Alle 《Gene》2013
Polymorphisms of butyrylcholinesterase (BChE) have been reported to be associated to weight, BMI variance and hypertriglyceridemia in adults and adolescents. The aim of the present study was to investigate the association of −116A (SNP: G/A; rs1126680) and 1914G (SNP: A/G; rs3495) variants of BCHE gene with anthropometric and biochemical variables associated with obesity in population sample of 115 individuals, from Southern Brazil. Participants were grouped in two categories: obese (BMI ≥ 30) and non-obese (BMI < 30). The 1914G allele showed significantly higher frequency in the obese group, and carriers of 1914G allele showed lower mean BChE activity when compared to 1914A carriers (p = 0.006). Higher means of BMI (p = 0.02) and triglyceride (TG; p = 0.01) were found in 1914G carriers (BMI = 27.57kg/m2; TG = 150.8 mg/dL) when compared to 1914A homozygotes (BMI = 25.55 kg/m2; TG = 107.9 mg/dL). Carriers of the −116A allele showed lower mean BChE activity than usual homozygotes, and the −116A variant was found in cis with 1914G (p < 0.0001; D′ = 1). The region of BCHE gene that contains the 1914G mutation site is target of microRNAs (miRs) and the response of BChE to glucocorticoids is especially influenced by these miRs. Therefore, it is possible that the 1914G allele can be interfering in gluconeogenesis, hyperglycemia, lipolysis and body fat distribution. This lower activity may cause an imbalance in lipid metabolism, which may lead to an increased predisposition to obesity and to a lower ability to maintain metabolic homeostasis. 相似文献
84.
Ana Nobre Nuno Empadinhas Maria Fernanda Nobre Eva Correia Lourenço Christopher Maycock Maria Rita Ventura Ana Mingote Milton S. da Costa 《Planta》2013,237(3):891-901
A mannosylglycerate synthase (MgS) gene detected in the genome of Selaginella moellendorffii was expressed in E. coli and the recombinant enzyme was purified and characterized. A remarkable and unprecedented feature of this enzyme was the ability to efficiently synthesize mannosylglycerate (MG) and glucosylglycerate (GG) alike, with maximal activity at 50 °C, pH 8.0 and with Mg2+ as reaction enhancer. We have also identified a novel glycoside hydrolase gene in this plant’s genome, which was functionally confirmed to be highly specific for the hydrolysis of MG and GG and named MG hydrolase (MgH), due to its homology with bacterial MgHs. The recombinant enzyme was maximally active at 40 °C and at pH 6.0–6.5. The activity was independent of cations, but Mn2+ was a strong stimulator. Regardless of these efficient enzymatic resources we could not detect MG or GG in S. moellendorffii or in the extracts of five additional Selaginella species. Herein, we describe the properties of the first eukaryotic enzymes for the synthesis and hydrolysis of the compatible solutes, MG and GG. 相似文献
85.
Adriana Fernanda Vizuete Daniela Fraga de Souza Maria Cristina Guerra Cristiane Batassini Márcio Ferreira Dutra Caren Bernardi Ana Paula Costa Carlos-Alberto Gonçalves 《Life sciences》2013,92(17-19):923-928
AimsWe investigated the effects of ketogenic diet (KD) on levels of tumor necrosis factor alpha (TNF-α, a classical pro-inflammatory cytokine), BDNF (brain-derived neurotrophic factor, commonly associated with synaptic plasticity), and S100B, an astrocyte neurotrophic cytokine involved in metabolism regulation.Main methodsYoung Wistar rats were fed during 8 weeks with control diet or two KD, containing different proportions of omega 6 and omega 3 polyunsaturated fatty acids. Contents of TNF-α, BDNF and S100B were measured by ELISA in two brain regions (hippocampus and striatum) as well as blood serum and cerebrospinal fluid.Key findingsOur data suggest that KD was able to reduce the levels of BDNF in the striatum (but not in hippocampus) and S100B in the cerebrospinal fluid of rats. These alterations were not affected by the proportion of polyunsaturated fatty acids offered. No changes in S100B content were observed in serum or analyzed brain regions. Basal TNF-α content was not affected by KD.SignificanceThese findings reinforce the importance of this diet as an inductor of alterations in the brain, and such changes might contribute to the understanding of the effects (and side effects) of KD in brain disorders. 相似文献
86.
Marina Azevêdo Souza Susana Johann Luciana Alves Rodrigues dos Santos Lima Fernanda Fraga Campos Isolda Castro Mendes Heloisa Beraldo Elaine Maria de Souza-Fagundes Patrícia Silva Cisalpino Carlos Augusto Rosa Tania Maria de Almeida Alves Nívea Pereira de Sá Carlos Leomar Zani 《Memórias do Instituto Oswaldo Cruz》2013,108(3):342-351
Lapachol was chemically modified to obtain its thiosemicarbazone and semicarbazone derivatives. These compounds were tested for antimicrobial activity against several bacteria and fungi by the broth microdilution method. The thiosemicarbazone and semicarbazone derivatives of lapachol exhibited antimicrobial activity against the bacteria Enterococcus faecalis and Staphylococcus aureus with minimal inhibitory concentrations (MICs) of 0.05 and 0.10 µmol/mL, respectively. The thiosemicarbazone and semicarbazone derivatives were also active against the pathogenic yeast Cryptococcus gattii (MICs of 0.10 and 0.20 µmol/mL, respectively). In addition, the lapachol thiosemicarbazone derivative was active against 11 clinical isolates of Paracoccidioides brasiliensis, with MICs ranging from 0.01-0.10 µmol/mL. The lapachol-derived thiosemicarbazone was not cytotoxic to normal cells at the concentrations that were active against fungi and bacteria. We synthesised, for the first time, thiosemicarbazone and semicarbazone derivatives of lapachol. The MICs for the lapachol-derived thiosemicarbazone against S. aureus, E. faecalis, C. gattii and several isolates of P. brasiliensis indicated that this compound has the potential to be developed into novel drugs to treat infections caused these microbes. 相似文献
87.
88.
Ana Filipa Palmeirim Melina de Souza Leite Margarida Santos-Reis Fernando A. S. Fernandez 《Studies on Neotropical Fauna and Environment》2013,48(3):231-238
We evaluated the selection of resting sites occupied by the water opossum Chironectes minimus, between 2004 and 2010, in streams of the Brazilian Atlantic Forest. Fourteen radio-tracked adult (males and females) opossums used natural cavities as resting sites. Opossums selected narrow river stretches and selected their resting sites mainly according to characteristics favoring protection against adverse weather conditions. Likewise, opossums avoided disturbed habitats and established their resting sites in well-preserved riparian forest sites, selecting river sections containing a high density of trees and a high proportion of forest cover between the river banks and 50 m from the river. Besides increasing our knowledge on this species habitat selection, such findings further highlight this species’ sensitivity to human disturbance. 相似文献
89.
George Amaro Elisangela Gomes Fidelis de Morais 《Experimental & applied acarology》2013,60(3):343-355
Among pests that have recently been introduced into the Americas, the red palm mite, Raoiella indica Hirst (Prostigmata: Tenuipalpidae), is the most invasive. This mite has spread rapidly to several Caribbean countries, United States of America, Mexico, Venezuela, Colombia and Brazil. The potential dispersion of R. indica to other regions of South America could seriously impact the cultivation of coconuts, bananas, exotic and native palms and tropical flowers such as the Heliconiaceae. To facilitate the development of efficacious R. indica management techniques such as the adoption of phytosanitary measures to prevent or delay the dispersion of this pest, the objective of this paper was to estimate the potential geographical distribution of R. indica in South America using a maximum entropy model. The R. indica occurrence data used in this model were obtained from extant literature, online databases and field sampling data. The model predicted potential suitable areas for R. indica in northern Colombia, central and northern Venezuela, Guyana, Suriname, east French Guiana and many parts of Brazil, including Roraima, the eastern Amazonas, northern Pará, Amapá and the coastal zones, from Pará to north of Rio de Janeiro. These results indicate the potential for significant R. indica related economic and social impacts in all of these countries, particularly in Brazil, because the suitable habitat regions overlap with agricultural areas for R. indica host plants such as coconuts and bananas. 相似文献
90.
Occurrence of alternariol and alternariol monomethyl ether in beverages from the Entre Rios Province market, Argentina 总被引:1,自引:0,他引:1
Leticia Broggi Cora Reynoso Silvia Resnik Fernanda Martinez Vanesa Drunday Ángela Romero Bernal 《Mycotoxin Research》2013,29(1):17-22
One hundred and eighty five samples of red, white and rosé wines and different juices purchased in Entre Rios, Argentina, were analyzed for the Alternaria mycotoxins alternariol (AOH) and alternariol methyl ether (AME). White wines were analyzed after removal of alcohol by a nitrogen stream and concentrated. AOH in red wines was cleaned up by solid-phase extraction columns in series (octadecyl and amino propyl modified silica) and AME quantified directly on the sample. The juices were filtered and concentrated, and then all sample extracts were quantified by high performance liquid chromatography with photodiode array detector that allows confirmation through UV spectra. Method validation revealed a good sensitivity with adequate LOD and LOQ for AME and less sensitivity for AOH (i.e. white wine: AME 0.8 and 1.4 ng/mL, AOH 2 and 3.3 ng/mL; red wine: AME 0.1 and 0.2 ng/mL, AOH 4.5 and 7.5 ng/mL; apple juice: AME 1.7 and 2.8 ng/mL, AOH 5 and 9 ng/mL; other juices: AME 2.0 and 3.1 ng/mL, AOH 6 and 10 ng/mL). Recoveries in all cases were greater than 80 %. Four of 53 white wine samples were contaminated with AOH with a maximum level of 18 ng/mL, 6 of 56 samples of red wine had a maximum of 13 ng/mL, and 3 of 68 samples of juices had traces of AOH. AME was less frequently detected than AOH, and the LOD and LOQ for AME are smaller than for AOH. Only three samples of white wine and one of red wine were contaminated, but in only one white wine sample (AME 225 ng/mL) did the toxin level exceed the LOQ. 相似文献