首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   170篇
  免费   7篇
  177篇
  2023年   1篇
  2021年   3篇
  2020年   1篇
  2019年   1篇
  2018年   1篇
  2017年   3篇
  2016年   4篇
  2015年   4篇
  2014年   3篇
  2013年   8篇
  2012年   9篇
  2011年   9篇
  2010年   7篇
  2009年   2篇
  2008年   9篇
  2007年   14篇
  2006年   12篇
  2005年   5篇
  2004年   10篇
  2003年   9篇
  2002年   9篇
  2001年   1篇
  2000年   3篇
  1999年   2篇
  1998年   2篇
  1997年   3篇
  1996年   5篇
  1995年   1篇
  1994年   6篇
  1993年   6篇
  1992年   3篇
  1991年   2篇
  1989年   1篇
  1988年   2篇
  1987年   1篇
  1986年   2篇
  1985年   3篇
  1984年   1篇
  1983年   3篇
  1982年   2篇
  1976年   1篇
  1975年   2篇
  1974年   1篇
排序方式: 共有177条查询结果,搜索用时 15 毫秒
131.
To determine whether alteration in serum antioxidant status is related to the increased oxidative stress as a cause of diabetic angiopathy, we measured both the antioxidant activity (AOA) and total peroxyl radical-trapping antioxidant parameter (TRAP), and their component individual antioxidants in serum of children with insulin-dependent diabetes mellitus (IDDM). The AOA was measured as the ability to inhibit lipid autoxidation in brain homogenates. TRAP was assayed as the ability to delay lipid peroxidation induced by an azo initiator. Antioxidants measured were ceruloplasmin, transferrin, and albumin components of AOA; and ascorbic acid, uric acid, protein sulfhydryl, and alpha-tocopherol as components of TRAP. Serum AOA appeared to be decreased in the diabetics in relation to poor glycemic control, corresponding to the decrease in transferrin and albumin. Serum haptoglobin level was also decreased in the diabetics. Similarly, the directly measured TRAP value was decreased in the diabetic serum mainly due to the decreased contribution of unidentified chain-breaking antioxidants, despite the increase in ascorbic acid and alpha-tocopherol. The decrease in both types of antioxidant activity in the diabetic serum, as new findings, suggests that a defective serum antioxidant status contributes to the increased oxidative stress in IDDM.  相似文献   
132.
Clostridium perfringens KZ1340 isolated from Antarctic soil was first classified as Clostridium plagarum and later as a lecithinase-negative variant of C. perfringens. Although the strain produced no detectable lecithinase (phospholipase C, PLC) activity in the culture supernatant, it was shown by Southern blot hybridization to possess a PLC-encoding gene (plc). To determine the cause of the PLC deficiency, we cloned and sequenced the plc gene from KZ1340. The deduced amino acid sequence consists of 398 amino acid residues, coinciding with those of the plc genes previously determined. Tyrosine was substituted for histidine at amino acid position 148, which is thought to bind a zinc ion essential for PLC activity. Northern blot analysis revealed that KZ1340 expressed the plc gene at an extremely low level. Furthermore, the plc gene cloned from C. perfringens strain 13 into a plasmid was expressed weakly in KZ1340, compared to that in strain 13. This indicates that the former strain represses plc gene expression in trans. When a phylogenetic tree of plc genes was constructed, the KZ1340 plc gene formed a monophyletic branch along with those of various other C. perfringens strains, supporting the classification of the strain as a variant of C. perfringens.  相似文献   
133.
Summary Ruthenium red combines with isolated synaptosomes, resulting in strong inhibition of their Ca2+-binding. In isotonic saline media, however, the dye-induced inhibition of Ca2+-binding is significantly greater than that expected for the amount of bound dye and Hill's exponent of the Ca2+-binding decreases to 1 with an increase in the amount of the dye bound. On the other hand in isotonic mannitol-sucrose solution, inhibition of synaptosomal Ca2+-binding brought about by the dye is proportional to the amount of dye bound. Based on these results, the effects of the dye on the co-operative nature of synaptosomal Ca2+-binding is discussed.  相似文献   
134.
135.
The susceptibility to transformation with Epstein-Barr virus (EBV) and the prevalence of antibodies reactive to EBV were examined in 43 primate species. In vitro EBV infection was revealed in lymphocytes from Old World monkeys, including patas monkeys and the colobines, as well as in lymphocytes from the apes. Antibodies reactive to EBV-early antigen/viral capsid antigen (EA/VCA) were detected in all the species of Old World monkeys and apes examined and in two out of seven species of New World monkeys.  相似文献   
136.
To develop safe vaccines for inducing mucosal immunity to major pulmonary bacterial infections, appropriate vaccine antigens (Ags), delivery systems and nontoxic molecular adjuvants must be considered. Such vaccine constructs can induce Ag‐specific immune responses that protect against mucosal infections. In particular, it has been shown that simply mixing the adjuvant with the bacterial Ag is a relatively easy means of constructing adjuvant‐based mucosal vaccine preparations; the resulting vaccines can elicit protective immunity. DNA‐based nasal adjuvants targeting mucosal DCs have been studied in order to induce Ag‐specific mucosal and systemic immune responses that provide essential protection against microbial pathogens that invade mucosal surfaces. In this review, initially a plasmid encoding the cDNA of Flt3 ligand (pFL), a molecule that is a growth factor for DCs, as an effective adjuvant for mucosal immunity to pneumococcal infections, is introduced. Next, the potential of adding unmethylated CpG oligodeoxynucleotide and pFL together with a pneumococcal Ag to induce protection from pneumococcal infections is discussed. Pneumococcal surface protein A has been used as vaccine for restoring mucosal immunity in older persons. Further, our nasal pFL adjuvant system with phosphorylcholine‐keyhole limpet hemocyanin (PC‐KLH) has also been used in pneumococcal vaccine development to induce complete protection from nasal carriage by Streptococcus pneumoniae . Finally, the possibility that anti‐PC antibodies induced by nasal delivery of pFL plus PC‐KLH may play a protective role in prevention of atherogenesis and thus block subsequent development of cardiovascular disease is discussed.
  相似文献   
137.
Levulinic acid (LA) is produced by the catalytic conversion of a variety of woody biomass. To investigate the potential use of desalting electrodialysis (ED) for LA purification, electrodialytic separation of levulinate from both reagent and cedar‐derived LA solution (40–160 g L?1) was demonstrated. When using reagent LA solution with pH5.0–6.0, the recovery rates of levulinate ranged from 68 to 99%, and the energy consumption for recovery of 1 kg of levulinate ranged from 0.18 to 0.27 kWh kg?1. With cedar‐derived LA solution (pH6.0), good agreement in levulinate recovery (88–99%), and energy consumption (0.18–0.22 kWh kg?1) were observed in comparison to the reagent LA solutions, although a longer operation time was required due to some impurities. The application of desalting ED was favorable for promoting microbial utilization of cedar‐derived LA. From 0.5 mol L?1 of the ED‐concentrated sodium levulinate solution, 95.6% of levulinate was recovered as LA calcium salt dihydrate by crystallization. This is the first report on ED application for LA recovery using more than 20 g L?1 LA solutions (40–160 g L?1). © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:448–453, 2017  相似文献   
138.
Objective: To determine whether serum adiponectin is decreased in obesity and is restored toward normal level after treatment in children. Research Methods and Procedures: Subjects were 53 Japanese obese children, 33 boys and 20 girls (6 to 14 years old), and 30 age‐matched nonobese controls for measuring adiponectin (16 boys and 14 girls). Blood was drawn after an overnight fast, and the obese children were subjected to anthropometric measurements including waist and hip circumferences and skinfold thicknesses. Paired samples were obtained from 21 obese children who underwent psychoeducational therapy. Visceral adipose tissue area was measured by computed tomography. Adiponectin was assayed by an enzyme‐linked immunosorbent assay. Results: The serum levels of alanine aminotransferase, uric acid, triglyceride, total cholesterol, low‐density lipoprotein‐cholesterol, total cholesterol/high‐density lipoprotein‐cholesterol, apo B, apo B/apo A1, and insulin in obese children were higher than the reference values. Serum adiponectin level was lower in the obese children than in the controls (6.4 ± 0.6 vs. 10.2 ± 0.8 mg/L, means ± SEM, p < 0.001). In 21 obese children whose percent overweight declined during therapy, the adiponectin level increased (p = 0.002). The adiponectin level was correlated inversely with visceral adipose tissue area in obese children (r = ?0.531, p < 0.001). The inverse correlations of adiponectin with alanine aminotransferase, uric acid, and insulin were significant after being adjusted for percentage overweight, percentage body fat, or sex. Discussion: Serum adiponectin level is decreased in obese children depending on the accumulation of visceral fat and is restored toward normal level by slimming.  相似文献   
139.
Naphtho[2,1-b]thiophene (NTH) is an asymmetric structural isomer of dibenzothiophene (DBT), and in addition to DBT derivatives, NTH derivatives can also be detected in diesel oil following hydrodesulfurization treatment. Rhodococcus sp. strain WU-K2R was newly isolated from soil for its ability to grow in a medium with NTH as the sole source of sulfur, and growing cells of WU-K2R degraded 0.27 mM NTH within 7 days. WU-K2R could also grow in the medium with NTH sulfone, benzothiophene (BTH), 3-methyl-BTH, or 5-methyl-BTH as the sole source of sulfur but could not utilize DBT, DBT sulfone, or 4,6-dimethyl-DBT. On the other hand, WU-K2R did not utilize NTH or BTH as the sole source of carbon. By gas chromatography-mass spectrometry analysis, desulfurized NTH metabolites were identified as NTH sulfone, 2′-hydroxynaphthylethene, and naphtho[2,1-b]furan. Moreover, since desulfurized BTH metabolites were identified as BTH sulfone, benzo[c][1,2]oxathiin S-oxide, benzo[c][1,2]oxathiin S,S-dioxide, o-hydroxystyrene, 2-(2′-hydroxyphenyl)ethan-1-al, and benzofuran, it was concluded that WU-K2R desulfurized NTH and BTH through the sulfur-specific degradation pathways with the selective cleavage of carbon-sulfur bonds. Therefore, Rhodococcus sp. strain WU-K2R, which could preferentially desulfurize asymmetric heterocyclic sulfur compounds such as NTH and BTH through the sulfur-specific degradation pathways, is a unique desulfurizing biocatalyst showing properties different from those of DBT-desulfurizing bacteria.  相似文献   
140.
Objective: To determine whether serum cholesteryl ester transfer protein (CETP), which is one of the physiologically active gene products secreted from adipose tissue, is increased and associated with atherogenic lipoprotein profile in obese children. Research Methods and Procedures: Subjects were 42 consecutive outpatient Japanese obese children, 29 boys and 13 girls, ranging in age from 5 to 14 years, and 25 age‐matched non‐obese children, 13 boys and 12 girls, as the control group for measuring CETP mass. Blood was drawn after an overnight fast and, at the same time, and anthropometric measurements including height, body weight, waist girth, hip girth, and triceps and subscapular skinfold thicknesses were taken. Paired samples were obtained from 15 obese children who underwent psychoeducational therapy. Serum CETP mass was assayed by an enzyme‐linked immunosorbent assay. Results: The serum levels of triglyceride, total cholesterol (TC), low‐density lipoprotein cholesterol, TC/high‐density lipoprotein cholesterol (HDLC), apolipoproteins (apo) B, apo B/apo A1, and insulin in obese children were significantly higher than the respective reference values. Serum CETP level was ~2‐fold higher (98.7 ± 3.6 vs. 50.9 ± 4.0 nM, means ± SEM, p < 0.001) in the obese children than in the controls. In 15 obese children, whose percentage of overweight declined during therapy, CETP levels decreased significantly. CETP level was correlated with HDLC, TC/HDLC, and insulin, and with percentage of overweight when the data of the obese and non‐obese children were combined. Discussion: CETP is increased and associated with the atherogenic lipoprotein profile in obese children.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号