全文获取类型
收费全文 | 1413篇 |
免费 | 79篇 |
国内免费 | 2篇 |
专业分类
1494篇 |
出版年
2022年 | 21篇 |
2021年 | 29篇 |
2020年 | 19篇 |
2019年 | 14篇 |
2018年 | 35篇 |
2017年 | 29篇 |
2016年 | 47篇 |
2015年 | 65篇 |
2014年 | 70篇 |
2013年 | 86篇 |
2012年 | 109篇 |
2011年 | 94篇 |
2010年 | 68篇 |
2009年 | 46篇 |
2008年 | 65篇 |
2007年 | 43篇 |
2006年 | 49篇 |
2005年 | 53篇 |
2004年 | 36篇 |
2003年 | 51篇 |
2002年 | 33篇 |
2001年 | 36篇 |
2000年 | 34篇 |
1999年 | 29篇 |
1998年 | 21篇 |
1997年 | 12篇 |
1996年 | 8篇 |
1995年 | 14篇 |
1994年 | 7篇 |
1993年 | 7篇 |
1992年 | 27篇 |
1991年 | 22篇 |
1990年 | 19篇 |
1989年 | 20篇 |
1988年 | 17篇 |
1987年 | 23篇 |
1986年 | 17篇 |
1985年 | 14篇 |
1984年 | 8篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1979年 | 5篇 |
1978年 | 9篇 |
1976年 | 7篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1972年 | 7篇 |
1970年 | 5篇 |
1966年 | 4篇 |
排序方式: 共有1494条查询结果,搜索用时 13 毫秒
141.
Claser C Malleret B Gun SY Wong AY Chang ZW Teo P See PC Howland SW Ginhoux F Rénia L 《PloS one》2011,6(4):e18720
Background
Infection with Plasmodium berghei ANKA (PbA) in susceptible mice induces a syndrome called experimental cerebral malaria (ECM) with severe pathologies occurring in various mouse organs. Immune mediators such as T cells or cytokines have been implicated in the pathogenesis of ECM. Red blood cells infected with PbA parasites have been shown to accumulate in the brain and other tissues during infection. This accumulation is thought to be involved in PbA–induced pathologies, which mechanisms are poorly understood.Methods and Findings
Using transgenic PbA parasites expressing the luciferase protein, we have assessed by real-time in vivo imaging the dynamic and temporal contribution of different immune factors in infected red blood cell (IRBC) accumulation and distribution in different organs during PbA infection. Using deficient mice or depleting antibodies, we observed that CD8+ T cells and IFN-γ drive the rapid increase in total parasite biomass and accumulation of IRBC in the brain and in different organs 6–12 days post-infection, at a time when mice develop ECM. Other cells types like CD4+ T cells, monocytes or neutrophils or cytokines such as IL-12 and TNF-α did not influence the early increase of total parasite biomass and IRBC accumulation in different organs.Conclusions
CD8+ T cells and IFN-γ are the major immune mediators controlling the time-dependent accumulation of P. berghei-infected red blood cells in tissues. 相似文献142.
The transfer of foreign genes into mammalian cells has been essential for understanding the functions of genes and mechanisms of genetic diseases, for the production of coding proteins and for gene therapy applications. Currently, the identification and selection of cells that have received transferred genetic material can be accomplished by methods, including drug selection, reporter enzyme detection and GFP imaging. These methods may confer antibiotic resistance, or be disruptive, or require special equipment. In this study, we labeled genetically modified cells with a cell surface biotinylation tag by co-transfecting cells with BirA, a biotin ligase. The modified cells can be quickly isolated for downstream applications using a simple streptavidin bead method. This system can also be used to screen cells expressing two sets of genes from separate vectors. 相似文献
143.
Siew Mei Samantha Ng Hui Si Vivian Ching GuiFang Xu Fui Mee Ng Esther H. Q. Ong Qiu Ying Lau Roland Jureen Jeffrey Hill C. S. Brian Chia 《International journal of peptide research and therapeutics》2017,23(4):481-491
Mupirocin is the first-line topical antibacterial drug for treating skin infections caused primarily by meticillin-resistant Staphylococcus aureus (MRSA). Its widespread use since its introduction more than 30 years ago has resulted in the global emergence of mupirocin-resistant strains of MRSA. Antimicrobial peptides (AMPs) are a promising class of antibacterial compounds that can potentially be developed to replace mupirocin due to their rapid membrane-targeting bactericidal mode of action and predicted low propensity for resistance development. Herein, we conducted and compared the antibacterial activities of 61 AMPs between 3 and 11 residues in length reported in the literature over the past decade against mupirocin-resistant MRSA. The most potent AMP, 11-residue peptide 50, was selected and tested against a panel of clinical isolates followed by a time-kill and a human dermal keratinocyte cytotoxicity assay. Lastly, peptide 50 was formulated into a topical spray which showed strong in vitro bactericidal effects against mupirocin-resistant MRSA. Our results strongly suggest that peptide 50 has the potential to be further developed into a new class of topical antibacterial agent for treating drug-resistant MRSA skin infections. 相似文献
144.
Ting Hway Wong Hai V. Nguyen Ming Terk Chiu Khuan Yew Chow Marcus Eng Hock Ong Gek Hsiang Lim Nivedita Vikas Nadkarni Dianne Carrol Tan Bautista Jolene Yu Xuan Cheng Lynette Mee Ann Loo Dennis Chuen Chai Seow 《PloS one》2015,10(9)
Background
Frailty is associated with adverse outcomes including disability, mortality and risk of falls. Trauma registries capture a broad range of injuries. However, frail patients who fall comprise a large proportion of the injuries occurring in ageing populations and are likely to have different outcomes compared to non-frail injured patients. The effect of frail fallers on mortality is under-explored but potentially significant. Currently, many trauma registries define low falls as less than three metres, a height that is likely to include non-frailty falls. We hypothesized that the low fall from less than 0.5 metres, including same-level falls, is a surrogate marker of frailty and predicts long-term mortality in older trauma patients.Methods
Using data from the Singapore National Trauma Registry, 2011–2013, matched till September 2014 to the death registry, we analysed adults aged over 45 admitted via the emergency department in public hospitals sustaining blunt injuries with an injury severity score (ISS) of 9 or more, excluding isolated hip fractures from same-level falls in the over 65. Patients injured by a low fall were compared to patients injured by high fall and other blunt mechanisms. Logistic regression was used to analyze 12-month mortality, controlling for mechanism of injury, ISS, revised trauma score (RTS), co-morbidities, gender, age and age-gender interaction. Different low fall height definitions, adjusting for injury regions, and analyzing the entire adult cohort were used in sensitivity analyses and did not change our findings.Results
Of the 8111 adults in our cohort, patients who suffered low falls were more likely to die of causes unrelated to their injuries (p<0.001), compared to other blunt trauma and higher fall heights. They were at higher risk of 12-month mortality (OR 1.75, 95% CI 1.18–2.58, p = 0.005), independent of ISS, RTS, age, gender, age-gender interaction and co-morbidities. Falls that were higher than 0.5m did not show this pattern. Males were at higher risk of mortality after low falls. The effect of age on mortality started at age 55 for males, and age 70 for females, and the difference was attributable to the additional mortality in male low-fallers.Conclusions
The low fall mechanism can optimize prediction of long-term mortality after moderate and severe injury, and may be a surrogate marker of frailty, complementing broader-based studies on aging. 相似文献145.
Heparin/heparan sulfate (HS) plays a key role in cellular adhesion. In this study, we utilized a 12‐mer random Escherichia coli cell surface display library to identify the sequence, which binds to heparin. Isolated insert analysis revealed a novel heparin‐binding peptide sequence, VRRSKHGARKDR, designated as HBP12. Our analysis of the sequence alignment of heparin‐binding motifs known as the Cardin–Weintraub consensus (BBXB, where B is a basic residue) indicates that the HBP12 peptide sequence contains two consecutive heparin‐binding motifs (i.e. RRSK and RKDR). SPR‐based BIAcore technology demonstrated that the HBP12 peptide binds to heparin with high affinity (KD = 191 nM ). The HBP12 peptide is found to bind the cell surface HS expressed by osteoblastic MC3T3 cells and promote HS‐dependent cell adhesion. Moreover, the surface‐immobilized HBP12 peptide on titanium substrates shows significant increases in the osteoblastic MC3T3‐E1 cell adhesion and proliferation. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd. 相似文献
146.
Yu W Chan-On W Teo M Ong CK Cutcutache I Allen GE Wong B Myint SS Lim KH Voorhoeve PM Rozen S Soo KC Tan P Teh BT 《Genome biology》2011,12(9):R96-14
Background
Well differentiated papillary mesothelioma of the peritoneum (WDPMP) is a rare variant of epithelial mesothelioma of low malignancy potential, usually found in women with no history of asbestos exposure. In this study, we perform the first exome sequencing of WDPMP.Results
WDPMP exome sequencing reveals the first somatic mutation of E2F1, R166H, to be identified in human cancer. The location is in the evolutionarily conserved DNA binding domain and computationally predicted to be mutated in the critical contact point between E2F1 and its DNA target. We show that the R166H mutation abrogates E2F1's DNA binding ability and is associated with reduced activation of E2F1 downstream target genes. Mutant E2F1 proteins are also observed in higher quantities when compared with wild-type E2F1 protein levels and the mutant protein's resistance to degradation was found to be the cause of its accumulation within mutant over-expressing cells. Cells over-expressing wild-type E2F1 show decreased proliferation compared to mutant over-expressing cells, but cell proliferation rates of mutant over-expressing cells were comparable to cells over-expressing the empty vector.Conclusions
The R166H mutation in E2F1 is shown to have a deleterious effect on its DNA binding ability as well as increasing its stability and subsequent accumulation in R166H mutant cells. Based on the results, two compatible theories can be formed: R166H mutation appears to allow for protein over-expression while minimizing the apoptotic consequence and the R166H mutation may behave similarly to SV40 large T antigen, inhibiting tumor suppressive functions of retinoblastoma protein 1. 相似文献147.
This study aimed to express two major drug-metabolizing human hepatic cytochromes P450 (CYPs), CYP2D6 and CYP3A4, together
with NADPH-cytochrome P450 oxidoreductase (OxR) in Escherichia coli and to evaluate their catalytic activities. Full length cDNA clones of both isoforms in which the N-terminus was modified
to incorporate bovine CYP17α sequence were inserted into a pCWori+ vector. The modified CYP cDNAs were subsequently expressed individually, each together with OxR by means of separate, compatible
plasmids with different antibiotic selection markers. The expressed proteins were evaluated by immunoblotting and reduced
CO difference spectral scanning. Enzyme activities were examined using high performance liquid chromatography (HPLC) assays
with probe substrates dextromethorphan and testosterone for CYP2D6 and CYP3A4, respectively. Results from immunoblotting demonstrated
the presence of both CYP proteins in bacterial membranes and reduced CO difference spectra of the cell preparations exhibited
the characteristic absorbance peak at 450 nm. Co-expressed OxR also demonstrated an activity level comparable to literature
values. Kinetic parameters, Km and Vmax values determined from the HPLC assays also agreed well with literature values. As a conclusion, the procedures described
in this study provide a relatively convenient and reliable means of producing catalytically active CYP isoforms suitable for
drug metabolism and interaction studies. 相似文献
148.
Fatiha Tabet Luisa F. Cuesta Torres Kwok Leung Ong Sudichhya Shrestha Sébastien A. Choteau Philip J. Barter Peter Clifton Kerry-Anne Rye 《PloS one》2016,11(3)
Background and Aims
microRNAs (miRNAs) are small, endogenous non-coding RNAs that regulate metabolic processes, including obesity. The levels of circulating miRNAs are affected by metabolic changes in obesity, as well as in diet-induced weight loss. Circulating miRNAs are transported by high-density lipoproteins (HDL) but the regulation of HDL-associated miRNAs after diet-induced weight loss has not been studied. We aim to determine if HDL-associated miR-16, miR-17, miR-126, miR-222 and miR-223 levels are altered by diet-induced weight loss in overweight and obese males.Methods
HDL were isolated from 47 subjects following 12 weeks weight loss comparing a high protein diet (HP, 30% of energy) with a normal protein diet (NP, 20% of energy). HDL-associated miRNAs (miR-16, miR-17, miR-126, miR-222 and miR-223) at baseline and after 12 weeks of weight loss were quantified by TaqMan miRNA assays. HDL particle sizes were determined by non-denaturing polyacrylamide gradient gel electrophoresis. Serum concentrations of human HDL constituents were measured immunoturbidometrically or enzymatically.Results
miR-16, miR-17, miR-126, miR-222 and miR-223 were present on HDL from overweight and obese subjects at baseline and after 12 weeks of the HP and NP weight loss diets. The HP diet induced a significant decrease in HDL-associated miR-223 levels (p = 0.015), which positively correlated with changes in body weight (r = 0.488, p = 0.032). Changes in miR-223 levels were not associated to changes in HDL composition or size.Conclusion
HDL-associated miR-223 levels are significantly decreased after HP diet-induced weight loss in overweight and obese males. This is the first study reporting changes in HDL-associated miRNA levels with diet-induced weight loss. 相似文献149.
Pial arteriolar diameter changes inversely with changes in systemic arterial blood pressure. Such changes are consistent with autoregulatory functions. These responses are reduced by a brief period of hypoxia followed by reoxygenation. By using an open cranial window preparation we assessed the changes in pial arteriolar diameters during blood pressure changes in rats induced by hemorrhage and reinfusion of blood, before and after a brief period of hypoxia. The slopes of the changes in pial arteriolar diameter as a function of mean arterial blood pressure were -0.47 +/- 0.26 micron/mmHg (mean +/- SD; 1 mmHg = 133.3 Pa) before hypoxia and -0.11 +/- 0.23 micron/mmHg after hypoxia in the untreated rats. In ouabain-treated rats, corresponding slopes were -0.42 +/- 0.24 and -0.46 +/- 0.22 micron/mmHg. The observed protective effects of ouabain might be a blockade of the Na-K pump in the sarcolemma of the vascular smooth muscle. 相似文献
150.
Esther Shuyi Gan Wei Fun Cheong Kuan Rong Chan Eugenia Ziying Ong Xiaoran Chai Hwee Cheng Tan Sujoy Ghosh Markus R Wenk Eng Eong Ooi 《The EMBO journal》2017,36(10):1348-1363
Dengue virus (DENV) has been found to replicate in lymphoid organs such as the lymph nodes, spleen, and liver in post‐mortem analysis. These organs are known to have low oxygen levels (~0.5–4.5% O2) due to the vascular anatomy. However, how physiologically low levels of oxygen affect DENV infection via hypoxia‐induced changes in the immune response remains unknown. Here, we show that monocytes adapted to 3% O2 show greater susceptibility to antibody‐dependent enhancement of DENV infection. Low oxygen level induces HIF1α‐dependent upregulation of fragment crystallizable gamma receptor IIA (FcγRIIA) as well as HIF1α‐independent alterations in membrane ether lipid concentrations. The increased FcγRIIA expression operates synergistically with altered membrane composition, possibly through increase membrane fluidity, to increase uptake of DENV immune complexes for enhanced infection. Our findings thus indicate that the increased viral burden associated with secondary DENV infection is antibody‐dependent but hypoxia‐induced and suggest a role for targeting hypoxia‐induced factors for anti‐dengue therapy. 相似文献