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   2096篇
  免费   146篇
  国内免费   1篇
  2023年   39篇
  2022年   23篇
  2021年   39篇
  2020年   40篇
  2019年   44篇
  2018年   72篇
  2017年   65篇
  2016年   112篇
  2015年   92篇
  2014年   127篇
  2013年   271篇
  2012年   145篇
  2011年   174篇
  2010年   173篇
  2009年   107篇
  2008年   82篇
  2007年   55篇
  2006年   78篇
  2005年   45篇
  2004年   58篇
  2003年   30篇
  2002年   29篇
  2001年   22篇
  2000年   13篇
  1999年   12篇
  1998年   14篇
  1997年   7篇
  1996年   18篇
  1995年   17篇
  1994年   15篇
  1993年   24篇
  1992年   20篇
  1991年   12篇
  1990年   9篇
  1989年   5篇
  1988年   13篇
  1985年   12篇
  1984年   9篇
  1983年   9篇
  1982年   9篇
  1981年   6篇
  1980年   4篇
  1978年   7篇
  1977年   9篇
  1976年   4篇
  1975年   8篇
  1974年   6篇
  1972年   11篇
  1971年   8篇
  1962年   4篇
排序方式: 共有2243条查询结果,搜索用时 31 毫秒
61.
Traumatic brain injury (TBI) was induced by a weight-drop device using 300 g–1 m weight-height impact. The study groups were: control, alpha-lipoic acid (LA) (100 mg/kg, po), TBI, and TBI + LA (100 mg/kg, po). Forty-eight hours after the injury, neurological scores were measured and brain samples were taken for histological examination or determination of thiobarbituric acid reactive substances (TBARS) and glutathione (GSH) levels, myeloperoxidase (MPO) and Na+-K+ ATPase activities, whereas cytokines (TNF-α, IL-1β) were determined in blood. Brain oedema was evaluated by wet–dry weight method and blood–brain barrier (BBB) permeability was evaluated by Evans Blue (EB) extravasation. As a result, neurological scores mildly increased in trauma groups. Moreover, TBI caused a significant decrease in brain GSH and Na+-K+ ATPase activity, which was accompanied with significant increases in TBARS level, MPO activity and plasma proinflammatory cytokines. LA treatment reversed all these biochemical indices as well as histopathological alterations. TBI also caused a significant increase in brain water content and EB extravasation which were partially reversed by LA treatment. These findings suggest that LA exerts neuroprotection by preserving BBB permeability and by reducing brain oedema probably by its anti-inflammatory and antioxidant properties in the TBI model.  相似文献   
62.
Manganese superoxide dismutase (MnSOD) is the most effective antioxidant enzyme in mitochondria and protects cells from reactive oxygen species‐induced oxidative damage. The aim of this study was to investigate the association between MnSOD Ala‐9Val gene polymorphism and prostate cancer (PCa) risk in Turkish men with prostate cancer. 33 patients with PCa and 81 control individuals were included in the study. We observed an association between MnSOD Ala/Ala frequency and a higher PCa risk. In addition, we found that the increased risk of early‐onset PCa (under age of 65) in the men homozygous for Ala allele was higher than the men homozygous for Val allele. However, we determined that MnSOD Ala‐9Val genotype was not associated with the aggressiveness of the disease. The results of our study suggest that MnSOD Ala/Ala genotype may influence on early‐onset of PCa patients, but no effect on subsequent development of the disease in Turkish men. However, our study has a limitation that is small numbers of individuals for cases and controls. Therefore, the presented study limited our statistical power to fully investigate the gene polymorphism on cancer risk. © 2013 Wiley Periodicals, Inc. J BiochemMol Toxicol 27:213‐218, 2013; View this article online at wileyonlinelibrary.com . DOI 10.1002/jbt.21472  相似文献   
63.
Free radicals are implicated in many diseases including atherosclerosis, cancer and also in rheumatoid arthritis. Reaction of uric acid with free radicals, such as hydroxyl radical and hypochlorous acid (HOCl) results in allantoin production. In this study, we measured the serum allantoin levels, oxidation products of uric acid, as a marker of free radical generation in rheumatoid arthritis. Fasting blood samples were obtained from 21 rheumatoid patients and 15 healthy controls. In this study, the serum allantoin and uric acid levels were measured by a gas chromatography–mass spectrometry method and the ratios were calculated. The mean allantoin and uric acid levels and ratios in the patient group were 22.1±11.3, 280.5±65.0 and 8.0±3.7?μM, while in the control group they were 13.6±6.3, 278.3±53.6 and 4.9±2.1?μM, respectively. The effects of gender, age, menopausal status, duration of disease and medications on serum allantoin and uric acid levels of the patient and control groups were studied. Our results suggest that uric acid acts as a free radical scavenger and thus is converted to allantoin. Increased allantoin levels suggest the possible involvement of free radicals in rheumatoid arthritis.  相似文献   
64.
The in vitro antioxidant effects of novel N-substituted indole-3-carboxamides (I3CDs) 1-10 on rat liver microsomal NADPH-dependent lipid peroxidation (LP) levels and their free radicals scavenging properties were determined by the inhibition of superoxide anion formation (SOD). Among the synthesized compounds, 4, 5, 8 and 9 significantly inhibited SOD with an inhibition range at 84–100% at 10? 3 M concentration. The presence of halo substituents both ortho- and para- positions of these compounds resulted 100% inhibition of SOD. Comparison the activity results of halogenated and non-halogenated derivatives suggested that the halogenated compounds are more active than the non-halogenated compounds. On the other hand, the introduction of a para fluoro benzyl in the 1-position of indole (compounds 7, 8) has more impact on the SOD inhibition when the benzamide ring was mono halogenated. However, none of other compounds had a significant inhibitory effects on the level of lipid peroxidation.  相似文献   
65.
The antioxidant role of novel N-substituted indole-2-carboxamides (I2CDs) was investigated for their inhibitory effects on superoxide anion (O2? ) and lipid peroxidation (LP). Among the synthesized I2CDs, 3, 4, 6, 8 and 9 significantly inhibited O2· ? with an inhibition range at 70–98%. Examination of substituent effects on activity showed that both the ortho- and para-positions of the benzamide residue needs to be dichlorinated in order to get a maximum inhibitory effect on superoxide anion. In general, halogenated derivatives were found more active then the non-halogenated ones. However, none of the I2CDs had a significant inhibitory effects on the level of lipid peroxidation; only compounds 7 and 10 moderately decreased LP levels by over 50% at 10? 3 M concentrations.  相似文献   
66.
The increasing clinical importance of drug-resistant mycobacterial pathogens has lent additional urgency to microbiological research and new antimycobacterial compound development. For this purpose, new triazoles were synthesized and evaluated for antituberculosis activity. A series of 4-arylidenamino-4H-1,2,4-triazole-3-thiol derivatives (2a–n) were synthesized from the treatment of 4-amino-4H-1,2,4-triazoles-3-thiol (1) with the respective aldehydes and were evaluated for antituberculosis activity against Mycobacterium tuberculosis H37Rv (ATCC 27294), using the BACTEC 460 radiometric system and BACTEC 12B medium. Compound 2k showed an intereting activity at 6.25 μg/mL with a 87 percentage inhibition.  相似文献   
67.
The antioxidant activity of some amido-carbonyl oximes containing a C=O and –NH–R adjacent to the oxime group, [Phenyl-C(=O)-C(=N-OH)-N(-H)-Phenyl(-R)] where R= H, 4-chloro, 4-methyl, 4-methoxy, 3,4-dichloro, 3,4-dimethyl, 3-chloro-4-dimethyl, 3-chloro-4-methoxy, naphthyl and an amido-carbonyl dioxime were investigated in vitro by ferric thiocyanate, total reducing power by potassium ferricyanide reduction, 1,1-diphenyl-2- picryl-hydrazyl (DPPH·) free radical scavenging, ferrous ions chelating, superoxide anion radical scavenging and hydrogen peroxide scavenging activity assays. The results indicated that the amido-carbonyl oximes have powerful antioxidant capacity.  相似文献   
68.
The present study was undertaken to determine in vivo and in vitro effects of some plant growth regulators on rat erythrocyte carbonic anhydrase (CA) and glucose-6-phosphate dehydrogenase (G6PD) activities. Both in vivo and in vitro, spermidine and kinetin did not affect enzymatic activities of CA and G6PD, whereas putrescine decreased these activities, and abscisic acid increased them. Since plants use such growth regulators, their effects should be considered on mammals consuming them since they may possess important biological effects.  相似文献   
69.
Fetuin-A is synthesized in the liver and is secreted into the bloodstream. Clinical studies suggest involvement of fetuin-A in metabolic disorders such as visceral obesity, insulin resistance, diabetes, and fatty liver. Curcumin is extracted from the rhizome Curcuma longa and has been shown to possess potent antioxidant, anticarcinogenic, anti-inflammatory, and hypoglycemic properties. In this study, we investigated the effect of curcumin treatment on serum fetuin-A levels as well as hepatic lipids and prooxidant–antioxidant status in rats fed a high-fat diet (HFD). Male Sprague–Dawley rats were divided into six groups. Group 1 was fed control diet (10 % of total calories from fat). Groups 2 and 3 were given curcumin (100 and 400 mg/kg bw/day, respectively ) by gavage for 8 weeks and were fed control diet. Group 4 was fed with HFD (60 % of total calories from fat). Groups 5 and 6 received HFD together with the two doses of curcumin, respectively. Curcumin treatment appeared to be effective in reducing liver triglycerides and serum fetuin-A levels. These findings suggest that the reduction of fetuin-A may contribute to the beneficial effects of curcumin in the pathogenesis of obesity.  相似文献   
70.
Stable coronary artery disease (CAD) can cause repetitive reversible myocardial ischaemia, and it seems to be possible that reversibly injured myocardium releases small amounts of soluble cytoplasmic proteins. Hence, the aim was to evaluate the effect of stable CAD on baseline serum levels of cardiac biomarkers. We studied 68 consecutive outpatients referred for gated myocardial perfusion imaging. Before a treadmill exercise test, blood samples for measurement of creatine kinase (CK), CK-myocardial band (CK-MB) mass, myoglobin, aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) were collected. Normal perfusion patterns were detected in 29 (43%) patients (group 1) and perfusion defects were detected in 39 (57%) patients (group 2). Baseline serum levels of biomarkers except CK were significantly higher in group 2 (p=0.001). Stable CAD increases baseline levels of CK-MB mass, myoglobin, AST and LDH in the serum and this increase is related to the extent and severity of the perfusion defect and to some extent the ejection fraction of the left ventricle.  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