全文获取类型
收费全文 | 4613篇 |
免费 | 392篇 |
国内免费 | 203篇 |
专业分类
耳鼻咽喉 | 19篇 |
儿科学 | 36篇 |
妇产科学 | 66篇 |
基础医学 | 405篇 |
口腔科学 | 67篇 |
临床医学 | 249篇 |
内科学 | 496篇 |
皮肤病学 | 116篇 |
神经病学 | 165篇 |
特种医学 | 54篇 |
外科学 | 220篇 |
综合类 | 365篇 |
预防医学 | 652篇 |
眼科学 | 65篇 |
药学 | 1336篇 |
中国医学 | 814篇 |
肿瘤学 | 83篇 |
出版年
2024年 | 33篇 |
2023年 | 77篇 |
2022年 | 175篇 |
2021年 | 220篇 |
2020年 | 170篇 |
2019年 | 162篇 |
2018年 | 133篇 |
2017年 | 233篇 |
2016年 | 239篇 |
2015年 | 243篇 |
2014年 | 306篇 |
2013年 | 662篇 |
2012年 | 292篇 |
2011年 | 280篇 |
2010年 | 215篇 |
2009年 | 195篇 |
2008年 | 205篇 |
2007年 | 199篇 |
2006年 | 185篇 |
2005年 | 159篇 |
2004年 | 144篇 |
2003年 | 137篇 |
2002年 | 110篇 |
2001年 | 90篇 |
2000年 | 45篇 |
1999年 | 50篇 |
1998年 | 52篇 |
1997年 | 35篇 |
1996年 | 32篇 |
1995年 | 18篇 |
1994年 | 17篇 |
1993年 | 12篇 |
1992年 | 13篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 13篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 1篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有5208条查询结果,搜索用时 31 毫秒
31.
《International journal of food sciences and nutrition》2013,64(7):765-773
In present study, 10 preferred traditional vegetables from Andaman and Nicobar Islands, India, were analysed for nutritional profiles. Moisture content in their edible parts ranged from 83.43 to 94.78%. Maximum ash content was recorded in Portulaca oleracea, crude protein in Colocasia esculenta, crude fibre in Eryngium foetidum and fat in E. foetidum. Phosphorus was maximum in Ipomea aquatica, potassium in C. esculenta, zinc, calcium and manganese in Centella asiatica, copper in Sauropus androgynous, sodium and iron in P. oleracea, magnesium in Amaranthus viridi and cobalt in C. esculenta. Maximum polyphenol was recorded in Hibiscus sabdariffa, carotenoids in A. viridi, ascorbic acid in Saursops androgynus, anthocyanin in C. esculenta and chlorophyll in S. androgynus. Antioxidant activity was maximum in P. oleracea. Positive correlation was observed between polyphenol and tannin content and also between antioxidant activity and photochemicals. The developed nutritional profiles is being used in health and nutrition related schemes in Islands. 相似文献
32.
The effect of lycopene supplementation on the antioxidant system was investigated by analyzing lipid peroxide levels, glutathione contents, and antioxidant enzyme activities in Mongolian gerbils fed a high fat diet. Gerbils were fed on each experimental diet for 6 weeks; normal diet (NC), normal diet with 0.05% lycopene (NL), high fat diet (HF), and a high fat diet with 0.05% lycopene (HFL). Dietary supplementation of lycopene increased hepatic lycopene level in gerbils fed a normal or high fat diet (P < 0.05). Liver and erythrocyte concentrations of lipid peroxide increased in gerbils fed a high fat diet, whereas lycopene supplementation decreased liver and erythrocyte concentrations of lipid peroxide (P < 0.05). Hepatic total glutathione content was higher in the NL group than that in the NC group (P < 0.05). Total antioxidant status in plasma increased following lycopene supplementation compared with that of the non-lycopene supplemented groups (P < 0.05). Hepatic catalase activity increased following dietary lycopene supplementation (P < 0.05). Superoxide dismutase activity in liver remained unchanged with lycopene supplementation, but erythrocyte superoxide dismutase activity increased in NL group compared with NC group (P < 0.05). Glutathione-S-transferase activity increased in the NL group compared to NC group (P < 0.05). Liver and erythrocyte glutathione peroxidase activity increased significantly in the NL group compared to that in the HF group (P < 0.05). Liver glutathione reductase activity was higher in the NL group than that in the NC group (P < 0.05). These results suggest that lycopene supplementation may be efficient for preventing chronic diseases induced by oxidative stress related to high fat diet. 相似文献
33.
34.
Megumi Ueno Ikuo Nakanishi Ken-ichiro Matsumoto 《Journal of Clinical Biochemistry and Nutrition》2013,52(2):95-100
A method for correctly assessing hydroxyl radical scavenging activity of antioxidative chemicals and/or biological compounds/materials was proposed. This method can simultaneously assess two factors, i.e. hydroxyl radical-scavenging and 5,5-dimethyl-2-hydroxy-1-pyrrolidine-N-oxide (hydroxyl radical adduct of 5,5-dimethyl-1-pyrroline-N-oxide)-reducing ability, as antioxidative properties. In this paper, some biologically common hydrophilic molecules, cell culture media, and rat plasma were tested. X-ray-induced hydroxyl radical can be detected using the electron paramagnetic resonance spin trapping technique. Using X-ray irradiation of the reaction mixture as the hydroxyl radical source, the true hydroxyl radical-scavenging ability of the subjected antioxidant can be assessed. In addition, the method simultaneously measures the reduction of 5,5-dimethyl-2-hydroxy-1-pyrrolidine-N-oxide, to estimate the reducing ability of the antioxidant. Biological materials, such as sugars and proteins, could abolish hydroxyl radical at the biological concentration. Ascorbic acid showed reducing ability at the biological concentration. The simultaneous assessment of hydroxyl radical-scavenging and reducing ability of antioxidants can be an informative index for antioxidants. 相似文献
35.
目的 探讨辣木叶水提物(MOLAE)对脂肪堆积人HepG2细胞的调节作用。方法 制备MOLAE冻干粉;通过CCK-8法检测油酸钠-钠棕榈酸酯(O-P)对HepG2细胞活力的影响、油红O染色检测O-P对细胞脂质堆积的影响、试剂盒法检测O-P对细胞三酰甘油(TG)、总胆固醇(TC)水平的影响,筛选O-P诱导HepG2细胞脂质代谢异常模型的作用浓度及时间;CCK-8法检测辛伐他汀、MOLAE对HepG2细胞活力的影响,筛选安全作用浓度;设立对照组、模型组、辛伐他汀(阳性药,15 μmol·L-1)组和MOLAE(3.125、6.250、12.500、25.000、50.000 μg·mL-1)组,除对照组外,其他各组均给予0.4-0.2 mmol·L-1的O-P诱导细胞脂质沉积,诱导3 h后开始给药,干预24 h后,CCK-8法检测细胞活性,油红O染色观察细胞中脂滴形成情况,试剂盒法测定细胞中TG、TC、谷胱甘肽(GSH)、超氧化物歧化酶(SOD)及丙二醛(MDA)水平。结果 确定造模方式为:0.4-0.2 mmol·L-1的O-P作用HepG2细胞3 h后开始给药;10、15 μmol·L-1的辛伐他汀和3.125~100.000 μg·mL-1的MOLAE作用于HepG2细胞24、48 h后,不影响细胞活力。与模型组比较,不同浓度的MOLAE(3.125、6.250、12.500、25.000、50.000 μg·mL-1)均能降低TG、TC、MDA水平(P<0.05、0.01),显著升高GSH、SOD水平(P<0.05、0.01)。油红O染色结果表明,辛伐他汀组和MOLAE组(12.5、25.0 μg·mL-1)脂滴堆积现象均较模型组有明显改善。结论 MOLAE能够降低O-P诱导的HepG2细胞中TG、TC水平,提高GSH、SOD水平和降低MDA水平,减少细胞中脂质堆积的现象。 相似文献
36.
《Journal of Pharmaceutical Analysis》2019,9(3):193-200
Pinus densiflora needle extract (PDNE) is widely reported to have many pharmacological activities including antioxidant potential. However, the solvent system used for extraction greatly affects its antioxidant quality. Hence, in the present study, we investigated the effect of a different ratio (vol/vol) of ethanol to water (0–100%) in the extraction of PDNE with potent antioxidant capacity. The chemical assays, 2,2-diphenyl-1 picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), were conducted to assess the antioxidant potential of PDNE. Subsequently, the cytoprotective effect of PDNE was determined using tert-butyl hydroperoxide (TBHP)-challenged HepG2 cellular model. The needle extracts from 40% ethanol (PDNE-40) showed greater radical scavenging activity followed by 60%, 20%, 80%, 0% and 100% ethanol extracts. EC50 value of the most active extract, PDNE-40, was 8.56 ± 0.51 μg/mL, relative to 1.34 ± 0.28 μg/mL of the standard trolox (for ABTS radical), and 75.96 ± 11.60 μg/mL, relative to 4.83 ± 0.26 μg/mL of the standard trolox (for DPPH radical). Either PDNE-20 or PDNE-40 pretreatment remarkably decreased the levels of reactive oxygen species (ROS), lipid peroxides and protein carbonyls in TBHP-challenged HepG2 cells. In addition, both PDNE-20 and PDNE-40 significantly reversed the decreased ratio of reduced (GSH) to oxidized (GSSG) glutathione. Moreover, these two extracts showed a significant inhibitory effect on TBHP-induced nuclear damage and loss of cell viability. In summary, the inclusion of 40% ethanol in water for extraction of Pinus densiflora needle greatly increases the antioxidant quality of the extract. 相似文献
37.
[目的] 系统研究参麦注射液体外抗氧化性能。[方法] 采用铁还原抗氧化能力 (FRAP)法、1,1-二苯基-2-三硝基苯肼(DPPH)自由基清除法、一氧化氮(NO)自由基清除法、过氧化氢(H2O2)清除法、亚铁(Fe2+)离子螯合法分别测试不同稀释倍率参麦注射液的总抗氧化能力、DPPH·清除活性、NO·清除活性、H2O2清除活性和Fe2+离子螯合活性,并将结果与0.1mg/mL 2,6-二叔丁基对甲酚(BHT)、10 mmol/L水溶性维生素E(Trolox)和10%柠檬酸的结果进行比较。[结果] 参麦注射液具有一定的体外抗氧化能力,总抗氧化能力和对自由基清除活性均呈浓度正依赖性;10倍稀释参麦注射液总抗氧化能力显著低于BHT和Trolox (P<0.01),但高于柠檬酸(P<0.01);参麦注射液对不同自由基清除能力存在差异,其强弱顺序为:NO·[(54.4±6.6)%] > Fe2+离子螯[(42.6±3.2)%] > DPPH·[(36.2±2.8)%] > H2O2[(23.5±1.2)%]。[结论] 参麦注射液体外抗氧化活性研究将为其抗氧化药理学机制提供了实验依据。 相似文献
38.
39.
《International journal of radiation biology》2013,89(4):334-343
Purpose:?To investigate the effect of 2.45?GHz microwave radiation on rat brain of male wistar strain.Material and methods:?Male rats of wistar strain (35 days old with 130?±?10?g body weight) were selected for this study. Animals were divided into two groups: Sham exposed and experimental. Animals were exposed for 2?h a day for 35 days to 2.45?GHz frequency at 0.34?mW/cm2 power density. The whole body specific absorption rate (SAR) was estimated to be 0.11?W/Kg. Exposure took place in a ventilated Plexiglas cage and kept in anechoic chamber in a far field configuration from the horn antenna. After the completion of exposure period, rats were sacrificed and the whole brain tissue was dissected and used for study of double strand DNA (Deoxyribonucleic acid) breaks by micro gel electrophoresis and the statistical analysis was carried out using comet assay (IV-2 version software). Thereafter, antioxidant enzymes and histone kinase estimation was also performed.Results:?A significant increase was observed in comet head (P?<?0.002), tail length (P?<?0.0002) and in tail movement (P?<?0.0001) in exposed brain cells. An analysis of antioxidant enzymes glutathione peroxidase (P?<?0.005), and superoxide dismutase (P?<?0.006) showed a decrease while an increase in catalase (P?<?0.006) was observed. A significant decrease (P?<?0.023) in histone kinase was also recorded in the exposed group as compared to the control (sham-exposed) ones. One-way analysis of variance (ANOVA) method was adopted for statistical analysis.Conclusion:?The study concludes that the chronic exposure to these radiations may cause significant damage to brain, which may be an indication of possible tumour promotion (Behari and Paulraj ). 相似文献
40.
多指标综合评分法优选甘草抗氧化活性成分闪式提取工艺 总被引:1,自引:0,他引:1
目的 建立最佳的甘草抗氧化活性成分闪式提取工艺.方法 应用多指标综合评分法,结合正交试验设计,以甘草总黄酮含量、DPPH自由基清除率和浸膏得率的综合评分为指标,考察甘草抗氧化活性成分闪式提取工艺.结果 最佳闪式提取工艺为90%乙醇,固液比1∶20(g/mL),提取次数3次,每次2min.结论 该工艺提取时间短、提取效率高,是一种简单、快速、实用的甘草抗氧化活性成分提取方法. 相似文献