全文获取类型
收费全文 | 2062篇 |
免费 | 287篇 |
国内免费 | 1篇 |
出版年
2024年 | 5篇 |
2023年 | 20篇 |
2022年 | 58篇 |
2021年 | 107篇 |
2020年 | 71篇 |
2019年 | 84篇 |
2018年 | 115篇 |
2017年 | 91篇 |
2016年 | 139篇 |
2015年 | 167篇 |
2014年 | 158篇 |
2013年 | 191篇 |
2012年 | 162篇 |
2011年 | 145篇 |
2010年 | 126篇 |
2009年 | 71篇 |
2008年 | 76篇 |
2007年 | 74篇 |
2006年 | 61篇 |
2005年 | 62篇 |
2004年 | 45篇 |
2003年 | 35篇 |
2002年 | 38篇 |
2001年 | 21篇 |
2000年 | 17篇 |
1999年 | 20篇 |
1997年 | 11篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1973年 | 5篇 |
1971年 | 5篇 |
1857年 | 4篇 |
排序方式: 共有2350条查询结果,搜索用时 328 毫秒
951.
952.
953.
Ayesha Alvi Nuzhath Fatima Ahmed Ali Jerah Mohammed Rizwan Yahya Hasan Hobani Rashad Al Sunosi Manal Mohamed El Hassan Taha Eldaw Mohamed Habiballah Pradeep Kumar Agarwal Siddig Ibrahim Abdulwahab 《PloS one》2015,10(10)
Tuberculosis(TB) is a disease of global significance, which accounts for a death in every 15 seconds. Recent studies shows TB is rising in certain parts of the world, and Saudi Arabia is one of them. Several factor contribute in predisposing the subjects for infection including but not limited to addiction to various compounds which have immune modulation properties, such as amphetamines and Heroin etc. Khat a plant whose leaves are chewed for its euphoric effect in east Africa and Arabian Peninsula including Saudi Arabia, is considered as mildly addictive, and its principle compound, Cathinone shares structural and functional similarity with amphetamine a known immunomodulator. Tuberculosis being a disease of immune modulation has a varied spectrum of complex interplay of proinflammatory molecules, resistin is one of them. In the present study, we try to explore the trinity of khat addiction, serum resistin level and tuberculosis by correlating the serum resistin level in non khat addicted healthy subjects, khat addicted healthy subjects, and in patients, both khat addicted and non khat addicted, with active tuberculosis. We observed significantly higher resistin level among the apparently healthy khat addicted subjects as compared to non addicted healthy controls. Thereafter, when we compare the resistin levels between khat addicted and non khat addicted TB patients we did not found significant difference between the two groups. However bacillary load was observe to be significantly higher among the khat addicted TB patient as compare to non addicted one. Validation of above results in animal model revealed dose dependant increase in bacillary growth in the Wistar rats treated with khat. Taken together these results suggest the role of khat in immune modulation albeit in the limited frame of resistin level. 相似文献
954.
Summary Optimum flocculating conditions for the yeast Kluyveromyces bulgaricus, in a glucose-bactopeptone medium, are obtained with 1.8 mM calcium for a carbohydrate/(nitrogenx6.25) ratio of 16.A comparative study of the wall phosphopeptidomannans extracted by pronase from flocculating and non-flocculating cultures showed that flocculation was associated with the following characteristics: increase of the amount and molecular weight of mannans, and higher phosphate contents; decrease of the amino acid and glucosamine rates, with a relative increase in hydroxy amino acids and decrease of basic amino acids; absence of galactose in both polymers although the flocculation was reversed by d-galactose. Acetolysis of the phosphopeptidomannan showed that the phenotypic expression of flocculation is correlated, at the structural level, with a lower content of N-acetylhexosamine residues linked to disaccharides and a higher content of phosphodisaccharides. According to these results the calcium dependent synthesis of a phosphopeptidomannan (instead of a N-acetylglucosaminopeptidomannan) with a larger and more branched structure, is necessary to allow the aggregation of the cells, via a presumed d-galactose sensible flocculating factor. 相似文献
955.
956.
Assaad A. Eid Ali Koubeissi Ribal Bou-Mjahed Nadine Al Khalil Manal Farah Rita Maalouf Niveen Nasser Kamal H. Bouhadir 《Bioorganic & medicinal chemistry letters》2013,23(1):174-178
The synthesis of a series of novel 3,4-cis- and 3,4-trans-substituted carbocyclic nucleoside analogs from protected uracil and thymine is described. The key reaction in the followed synthetic protocols utilized the Mitsunobu reaction to couple 3,4-substituted cyclopentanols to 3N-benzoyl uracil or 3N-benzoyl thymine. These molecules were evaluated with regard to their ability to treat diabetic nephropathy. Our results show that two analogs significantly reduced high-glucose induced glomerular mesangial cells proliferation and matrix protein accumulation in vitro and, more interestingly, exhibited an anti-oxidative effect suggesting that the activity may be mediated through ROS-dependent mechanism. 相似文献
957.
Dr. Al. Skofitz 《Plant Systematics and Evolution》1857,7(46):365-366
Ohne Zusammenfassung 相似文献
958.
Hamster liver glutathione peroxidase was purified to homogeneity in three chromatographic steps and with 30% yield. The purified enzyme had a specific activity of approximately 500 μmol cumene hydroperoxide reduced/min/mg of protein at 37 °C, pH 7.6, and 0.25 mm GSH. The enzyme was shown to be a tetramer of indistinguishable subunits, the molecular weight of which was approximately 23,000 as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A single isoelectric point of 5.0 was attributed to the active enzyme. Amino acid analysis determined that selenocysteine, identified as its carboxymethyl derivative, was the only form of selenium. One residue of cysteine was found to be present in each glutathione peroxidase subunit. The presence of tryptophan was colorimetrically determined. Pseudo-first-order kinetics of inactivation of the enzyme by iodoacetate was observed at neutral pH with GSH as the only reducing agent. An optimal pH of 8.0 at 37 °C and an activation energy of 3 kcal/mol at pH 7.6 were found. A ter-uni-ping-pong mechanism was shown by the use of an integrated-rate equation. At pH 7.6, the apparent second-order rate constants for reaction of glutathione peroxidase with hydroperoxides were as follows: k1 (t-butyl hydroperoxide), 7.06 × 105 mm min?1; k1 (cumene hydroperoxide), 1.04 × 106 mm?1 min?1; k1 (p-menthane hydroperoxide), 1.2 × 106 mm?1 min?1; k1 (diisopropylbenzene hydroperoxide), 1.7 × 106 mm?1 min?1; k1 (linoleic acid hydroperoxide), 2.36 × 106 mm?1 min?1; k1 (ethyl hydroperoxide), 2.5 × 106 mm?1 min?1; and k1 (hydrogen peroxide), 2.98 × 106 mm?1 min?1. It is concluded that for bulky hydroperoxides, the more hydrophobic the substrate, the faster its reduction by glutathione peroxidase. 相似文献
959.
Miran A. Jaffa Firas Kobeissy Moustafa Al Hariri Hussein Chalhoub Assaad Eid Fuad N. Ziyadeh Ayad A. Jaffa 《PloS one》2012,7(9)
Diabetic nephropathy (DN), the leading cause of end-stage renal failure, is clinically manifested by albuminuria and a progressive decline in glomerular filtration rate. The risk factors and mechanisms that contribute to the development and progression of DN are still incompletely defined. To address the involvement of bradykinin B2-receptors (B2R) in DN, we used a genome wide approach to study the effects of diabetes on differential renal gene expression profile in wild type and B2R knockout (B2R−/−) mice. Diabetes was induced with streptozotocin and plasma glucose levels and albumin excretion rate (AER) were measured at predetermined times throughout the 23 week study period. Longitudinal analysis of AER indicated that diabetic B2R−/−D null mice had a significantly decreased AER levels compared to wild type B2R+/+D mice (P = 0.0005). Results from the global microarray study comparing gene expression profiles among four groups of mice respectively: (B2R+/+C, B2R+/+D, B2R−/−C and B2R−/−D) highlighted the role of several altered pathological pathways in response to disruption of B2R and to the diabetic state that included: endothelial injury, oxidative stress, insulin and lipid metabolism and inflammatory process with a marked alteration in the pro-apoptotic genes. The findings of the present study provide a global genomics view of biomarkers that highlight the mechanisms and putative pathways involved in DN. 相似文献
960.
Nnenna A. Finn Danny Eapen Pankaj Manocha Hatem Al Kassem Bernard Lassegue Nima Ghasemzadeh Arshed Quyyumi Charles D. Searles 《FEBS letters》2013
Coronary heart disease (CHD) is characterized by abnormal intercellular communication and circulating microRNAs (miRNAs) are likely involved in this process. Here, we show that CHD was associated with changes in the transport of circulating miRNA, particularly decreased miRNA enrichment in microparticles (MPs). Additionally, MPs from CHD patients were less efficient at transferring miRNA to cultured HUVECs, which correlated with their diminished capacity to bind developmental endothelial locus-1 (Del-1). In summary, CHD was associated with distinct changes in circulating miRNA transport and these changes may contribute to the abnormal intercellular communication that underlies CHD initiation and progression. 相似文献