全文获取类型
收费全文 | 3052篇 |
免费 | 221篇 |
国内免费 | 4篇 |
专业分类
3277篇 |
出版年
2024年 | 1篇 |
2023年 | 18篇 |
2022年 | 27篇 |
2021年 | 44篇 |
2020年 | 38篇 |
2019年 | 69篇 |
2018年 | 78篇 |
2017年 | 82篇 |
2016年 | 117篇 |
2015年 | 208篇 |
2014年 | 191篇 |
2013年 | 237篇 |
2012年 | 296篇 |
2011年 | 291篇 |
2010年 | 181篇 |
2009年 | 129篇 |
2008年 | 192篇 |
2007年 | 174篇 |
2006年 | 150篇 |
2005年 | 118篇 |
2004年 | 159篇 |
2003年 | 140篇 |
2002年 | 107篇 |
2001年 | 37篇 |
2000年 | 27篇 |
1999年 | 29篇 |
1998年 | 22篇 |
1997年 | 15篇 |
1996年 | 16篇 |
1995年 | 11篇 |
1994年 | 9篇 |
1993年 | 3篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1990年 | 2篇 |
1989年 | 6篇 |
1988年 | 1篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1956年 | 1篇 |
排序方式: 共有3277条查询结果,搜索用时 15 毫秒
171.
Koldo Garcia-Etxebarria María Alma Bracho Juan Carlos Galán Tomàs Pumarola Jesús Castilla Raúl Ortiz de Lejarazu Mario Rodríguez-Dominguez Inés Quintela Núria Bonet Marc Garcia-Garcerà Angela Domínguez Fernando González-Candelas Francesc Calafell CIBERESP Cases Controls in Pandemic Influenza Working Group 《PloS one》2015,10(10)
172.
Sergei Grigoryan Michael B Yee Yair Glick Doron Gerber Eldad Kepten Yuval Garini In Hong Yang Paul R. Kinchington Ronald S. Goldstein 《PloS one》2015,10(5)
Varicella Zoster Virus (VZV), the alphaherpesvirus that causes varicella upon primary infection and Herpes zoster (shingles) following reactivation in latently infected neurons, is known to be fusogenic. It forms polynuclear syncytia in culture, in varicella skin lesions and in infected fetal human ganglia xenografted to mice. After axonal infection using VZV expressing green fluorescent protein (GFP) in compartmentalized microfluidic cultures there is diffuse filling of axons with GFP as well as punctate fluorescence corresponding to capsids. Use of viruses with fluorescent fusions to VZV proteins reveals that both proteins encoded by VZV genes and those of the infecting cell are transferred in bulk from infecting non-neuronal cells to axons. Similar transfer of protein to axons was observed following cell associated HSV1 infection. Fluorescence recovery after photobleaching (FRAP) experiments provide evidence that this transfer is by diffusion of proteins from the infecting cells into axons. Time-lapse movies and immunocytochemical experiments in co-cultures demonstrate that non-neuronal cells fuse with neuronal somata and proteins from both cell types are present in the syncytia formed. The fusogenic nature of VZV therefore may enable not only conventional entry of virions and capsids into axonal endings in the skin by classical entry mechanisms, but also by cytoplasmic fusion that permits viral protein transfer to neurons in bulk. 相似文献
173.
Rita Casc?o Bruno Vidal Inês P. Lopes Eunice Paisana José Rino Luis F. Moita Jo?o E. Fonseca 《PloS one》2015,10(12)
Background
Rheumatoid arthritis (RA) is a chronic immune-mediated inflammatory disease characterized by cellular infiltration into the joints, hyperproliferation of synovial cells and bone damage. Available treatments for RA only induce remission in around 30% of the patients, have important adverse effects and its use is limited by their high cost. Therefore, compounds that can control arthritis, with an acceptable safety profile and low production costs are still an unmet need. We have shown, in vitro, that celastrol inhibits both IL-1β and TNF, which play an important role in RA, and, in vivo, that celastrol has significant anti-inflammatory properties. Our main goal in this work was to test the effect of celastrol in the number of sublining CD68 macrophages (a biomarker of therapeutic response for novel RA treatments) and on the overall synovial tissue cellularity and joint structure in the adjuvant-induced rat model of arthritis (AIA).Methods
Celastrol was administered to AIA rats both in the early (4 days after disease induction) and late (11 days after disease induction) phases of arthritis development. The inflammatory score, ankle perimeter and body weight were evaluated during treatment period. Rats were sacrificed after 22 days of disease progression and blood, internal organs and paw samples were collected for toxicological blood parameters and serum proinflammatory cytokine quantification, as well as histopathological and immunohistochemical evaluation, respectively.Results
Here we report that celastrol significantly decreases the number of sublining CD68 macrophages and the overall synovial inflammatory cellularity, and halted joint destruction without side effects.Conclusions
Our results validate celastrol as a promising compound for the treatment of arthritis. 相似文献174.
Ribose 5-Phosphate Isomerase B Knockdown Compromises Trypanosoma brucei Bloodstream Form Infectivity
Inês Loureiro Joana Faria Christine Clayton Sandra Macedo-Ribeiro Nuno Santarém Nilanjan Roy Anabela Cordeiro-da-Siva Joana Tavares 《PLoS neglected tropical diseases》2015,9(1)
Ribose 5-phosphate isomerase is an enzyme involved in the non-oxidative branch of the pentose phosphate pathway, and catalyzes the inter-conversion of D-ribose 5-phosphate and D-ribulose 5-phosphate. Trypanosomatids, including the agent of African sleeping sickness namely Trypanosoma brucei, have a type B ribose-5-phosphate isomerase. This enzyme is absent from humans, which have a structurally unrelated ribose 5-phosphate isomerase type A, and therefore has been proposed as an attractive drug target waiting further characterization. In this study, Trypanosoma brucei ribose 5-phosphate isomerase B showed in vitro isomerase activity. RNAi against this enzyme reduced parasites'' in vitro growth, and more importantly, bloodstream forms infectivity. Mice infected with induced RNAi clones exhibited lower parasitaemia and a prolonged survival compared to control mice. Phenotypic reversion was achieved by complementing induced RNAi clones with an ectopic copy of Trypanosoma cruzi gene. Our results present the first functional characterization of Trypanosoma brucei ribose 5-phosphate isomerase B, and show the relevance of an enzyme belonging to the non-oxidative branch of the pentose phosphate pathway in the context of Trypanosoma brucei infection. 相似文献
175.
Hyun Sook Hwang In Young Park Dae Won Kim Soo Young Choi Young Ok Jung Hyun Ah Kim 《BMB reports》2015,48(7):407-412
The 12 kDa FK506-binding protein (FK506BP12), an immunosuppressor, modulates T cell activation via calcineurin inhibition. In this study, we investigated the ability of PEP-1-FK506BP12, consisting of FK506BP12 fused to the protein transduction domain PEP-1 peptide, to suppress catabolic responses in primary human chondrocytes and in a mouse carrageenan-induced paw arthritis model. Western blotting and immunofluorescence analysis showed that PEP-1-FK506BP12 efficiently penetrated chondrocytes and cartilage explants. In interleukin-1β (IL-1β)-treated chondrocytes, PEP-1-FK506BP12 significantly suppressed the expression of catabolic enzymes, including matrix metalloproteinases (MMPs)-1, -3, and -13 in addition to cyclooxygenase-2, at both the mRNA and protein levels, whereas FK506BP12 alone did not. In addition, PEP-1-FK506BP12 decreased IL-1β-induced phosphorylation of the mitogen-activated protein kinase (MAPK) complex (p38, JNK, and ERK) and the inhibitor kappa B alpha. In the mouse model of carrageenan-induced paw arthritis, PEP-1-FK506BP12 suppressed both carrageenan-induced MMP-13 production and paw inflammation. PEP-1-FK506BP12 may have therapeutic potential in the alleviation of OA progression. [BMB Reports 2015; 48(7): 407-412] 相似文献
176.
Modeling and optimization of phospholipase A1‐catalyzed hydrolysis of phosphatidylcholine using response surface methodology for lysophosphatidylcholine production 下载免费PDF全文
Modeling the phospholipase A1 (PLA1)‐catalyzed partial hydrolysis of soy phosphatidylcholine (PC) in hexane for the production of lysophosphatidylcholine (LPC) and optimizing the reaction conditions using response surface methodology were described. The reaction was performed with 4 g of PC in a stirred batch reactor using a commercial PLA1 (Lecitase Ultra) as the biocatalyst. The effects of temperature, reaction time, water content, and enzyme loading on LPC and glycerylphosphorylcholine (GPC) content in the reaction products were elucidated using the models established. Optimal reaction conditions for maximizing the LPC content while suppressing acyl migration, which causes GPC formation, were as follows: temperature, 60°C; reaction time, 3 h; water content, 10% of PC; and enzyme loading, 1% of PC. When the reaction was conducted with 40 g of PC under these conditions, the reaction products contained 83.7 mol % LPC and were free of GPC. LPC had a higher total unsaturated fatty acid content than original PC had and was mainly composed of linoleic acid (78.0 mol % of the total fatty acids). © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 31:35–41, 2015 相似文献
177.
Roberto C. Molina-Quiroz Cecilia A. Silva Cristian F. Molina Lorenzo E. Leiva Sebastián Reyes-Cerpa Inés Contreras Carlos A. Santiviago 《Open biology》2015,5(10)
It has been proposed that sub-inhibitory concentrations of antibiotics play a role in virulence modulation. In this study, we evaluated the ability of Salmonella enterica serovar Typhimurium (hereafter S. Typhimurium) to colonize systemically BALB/c mice after exposure to a sub-inhibitory concentration of cefotaxime (CTX). In vivo competition assays showed a fivefold increase in systemic colonization of CTX-exposed bacteria when compared to untreated bacteria. To identify the molecular mechanisms involved in this phenomenon, we carried out a high-throughput genetic screen. A transposon library of S. Typhimurium mutants was subjected to negative selection in the presence of a sub-inhibitory concentration of CTX and genes related to anaerobic metabolism, biosynthesis of purines, pyrimidines, amino acids and other metabolites were identified as needed to survive in this condition. In addition, an impaired ability for oxygen consumption was observed when bacteria were cultured in the presence of a sub-inhibitory concentration of CTX. Altogether, our data indicate that exposure to sub-lethal concentrations of CTX increases the systemic colonization of S. Typhimurium in BALB/c mice in part by the establishment of a fitness alteration conducive to anaerobic metabolism. 相似文献
178.
179.
Pedro Del Bianco Benedeti Lorrayny Galoro da Silva Eduardo Marostegan de Paula Teshome Shenkoru Marcos Inácio Marcondes Hugo Fernando Monteiro Brad Amorati Yenling Yeh Simon Roger Poulson Antonio Pinheiro Faciola 《PloS one》2015,10(11)
The objective of this study was to evaluate the effects of partially replacing dry ground corn with glycerin on ruminal fermentation using a dual-flow continuous culture system. Six fermenters (1,223 ± 21 ml) were used in a replicated 3x3 Latin square arrangement with three periods of 10 d each, with 7 d for diet adaptation and 3 d for sample collections. All diets contained 75% concentrate and three dietary glycerin levels (0, 15, and 30% on dry matter basis), totaling six replicates per treatment. Fermenters were fed 72 g of dry matter/d equally divided in two meals/d, at 0800 and 2000 h. Solid and liquid dilution rates were adjusted daily to 5.5 and 11%/h, respectively. On d 8, 9, and 10, samples of 500 ml of solid and liquid digesta effluent were mixed, homogenized, and stored at -20°C. Subsamples of 10 ml were collected and preserved with 0.2 mL of a 50% H2SO4 solution for later determination of NH3-N and volatile fatty acids. Microbial biomass was isolated from fermenters for chemical analysis at the end of each experimental period. Data were analyzed using the MIXED procedure in SAS with α = 0.05. Glycerin levels did not affect apparent digestibility of DM (P
Lin. = 0.13; P
Quad. = 0.40), OM (P
Lin. = 0.72; P
Quad. = 0.15), NDF (P
Lin. = 0.38; P
Quad. = 0.50) and ADF (P
Lin. = 0.91; P
Quad. = 0.18). Also, glycerin inclusion did not affect true digestibility of DM (P
Lin. = 0.35; P
Quad. = 0.48), and OM (P
Lin. = 0.08; P
Quad. = 0.19). Concentrations of propionate (P < 0.01) and total volatile fatty acids (P < 0.01) increased linearly and concentrations of acetate (P < 0.01), butyrate (P = 0.01), iso-valerate (P < 0.01), and total branched-chain volatile fatty acids, as well as the acetate: propionate ratio (P < 0.01) decreased with glycerin inclusion. Linear increases on NH3-N concentration in digesta effluent (P < 0.01) and on NH3-N flow (P < 0.01) were observed due to glycerin inclusion in the diets. Crude protein digestibility (P = 0.04) and microbial N flow (P = 0.04) were greater in the control treatment compared with the other treatments and responded quadratically with glycerin inclusion. Furthermore, the inclusion of glycerin linearly decreased (P = 0.02) non-ammonia N flow. Glycerin levels did not affect the flows of total N (P
Lin. = 0.79; P
Quad. = 0.35), and dietary N (P
Lin. = 0.99; P
Quad. = 0.07), as well as microbial efficiency (P
Lin. = 0.09; P
Quad. = 0.07). These results suggest that partially replacing dry ground corn with glycerin may change ruminal fermentation, by increasing total volatile fatty acids, and propionate concentration without affecting microbial efficiency, which may improve glucogenic potential of beef cattle diets. 相似文献
180.
Kinetics of Anti-Phlebotomus perniciosus Saliva Antibodies in Experimentally Bitten Mice and Rabbits