全文获取类型
收费全文 | 259篇 |
免费 | 13篇 |
国内免费 | 4篇 |
专业分类
妇产科学 | 1篇 |
基础医学 | 8篇 |
口腔科学 | 3篇 |
临床医学 | 4篇 |
内科学 | 14篇 |
皮肤病学 | 16篇 |
神经病学 | 4篇 |
外科学 | 12篇 |
综合类 | 3篇 |
预防医学 | 124篇 |
眼科学 | 17篇 |
药学 | 18篇 |
中国医学 | 10篇 |
肿瘤学 | 42篇 |
出版年
2022年 | 17篇 |
2021年 | 24篇 |
2020年 | 8篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 11篇 |
2015年 | 10篇 |
2014年 | 12篇 |
2013年 | 33篇 |
2012年 | 12篇 |
2011年 | 8篇 |
2010年 | 8篇 |
2009年 | 6篇 |
2008年 | 5篇 |
2007年 | 6篇 |
2006年 | 14篇 |
2005年 | 15篇 |
2004年 | 14篇 |
2003年 | 12篇 |
2002年 | 13篇 |
2001年 | 11篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1984年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有276条查询结果,搜索用时 31 毫秒
101.
Rydén M Garvin P Kristenson M Leanderson P Ernerudh J Jonasson L 《Journal of internal medicine》2012,272(4):371-384
Abstract. Rydén M, Garvin P, Kristenson M, Leanderson P, Ernerudh J, Jonasson L (Linköping University, Linköping, Sweden; Örebro University Hospital, Örebro, Sweden; University of British Colombia, Vancouver, BC, Canada). Provitamin A carotenoids are independently associated with matrix metalloproteinase‐9 in plasma samples from a general population. J Intern Med 2012; 272: 371–384. Background and aim. Carotenoids in plasma are inversely associated with cardiovascular risk. Low levels can be explained by low dietary intake but also by a number of other factors including inflammatory activity. Given that matrix metalloproteinase (MMP)‐9 has an important role in inflammation and cardiovascular disease, we hypothesized that circulating MMP‐9 levels would be inversely related to total or single carotenoids in a general population cohort. Methods. A well‐characterized population‐based cohort of 285 Swedish men and women (45–69 years) was used for the present study. The intake of carotenoid‐rich fruits and vegetables was estimated from a food frequency questionnaire. Levels of MMP‐9, C‐reactive protein (CRP), interleukin (IL)‐6 and six major carotenoids [β‐cryptoxanthine, α‐carotene, β‐carotene, lutein (+zeaxanthin) and lycopene] were determined in plasma. Results. Lower plasma levels of total and single carotenoids were associated with lower dietary intake of carotenoids, older age, male sex, lower physical activity, higher alcohol consumption, higher body mass index (BMI), higher systolic and diastolic blood pressures, lower levels of total cholesterol and HDL cholesterol and higher levels of CRP, IL‐6 and MMP‐9. After multivariate adjustments, plasma levels of total carotenoids and provitamin A carotenoids (β‐cryptoxanthine, α‐carotene and β‐carotene) remained independently associated with sex, dietary intake of carotenoids, BMI, HDL cholesterol and MMP‐9, whilst associations with CRP and IL‐6 were not maintained. Neither dietary intake of carotenoid‐rich fruits and vegetables, nor vitamin supplement use was associated with MMP‐9, CRP or IL‐6 levels. Conclusion. Plasma carotenoids were associated with a variety of factors including age, sex, dietary intake and metabolic variables. A new finding was the independent relationship in plasma between low provitamin A carotenoids and high MMP‐9, suggesting a link between these carotenoids, matrix turnover and arterial remodelling. 相似文献
102.
Antioxidant activity of topically applied lycopene 总被引:1,自引:0,他引:1
M Andreassi† E Stanghellini‡ A Ettorre§ A Di Stefano§ L Andreassi‡ 《Journal of the European Academy of Dermatology and Venereology》2004,18(1):52-55
BACKGROUND: Ultraviolet (UV) rays cause depletion of the antioxidant substances contained in the epidermis. This is the rationale for the use of topical antioxidant substances. METHODS: We studied the protective activity against UV radiation of a product based on lycopene and a product containing a mixture of vitamins E and C. Photostimulation was applied with a solar simulator and the cutaneous response was evaluated instrumentally. RESULTS: The lycopene-based product had a much greater protective ability than the product containing the mixture of vitamins. CONCLUSIONS: Lycopene has suitable characteristics to be used successfully in the prevention of cutaneous damage by free radicals. Its antioxidant ability is probably due to its high reductive power. 相似文献
103.
《Experimental eye research》1996,62(6):713-720
The present study was designed to assess the relationship between iris color and macular pigment optical density. Both melanin and carotenoids (responsible for iris color and macular pigment composition, respectively) appear to protect the retina through similar mechanisms and higher concentrations may reduce the incidence of retimal degenerations. The evaluate this relationship, 95 subjects were examined and the following variables were measured: iris color; macular pigment optical density (MP); plasma concentrations of lutein and zeaxanthin and beta carotene; dietary intake of lutein and zeaxanthin and beta-carotene; and total fat intake. Iris color was determined by self assessment and classified as blue or gray (group I), green or hazel (group II) or brown or black (group III). MP density was measured psychophysically by measuring foveal and parafoveal sensitivities to lights of 460 and 550 nm, using the method of heterochromatic flicker photometry. Plasma carotenoid concentrations were measured using reverse-phase high-performance liquid chromatography. Dietary intake was determined by a detailed food-frequency questionnaire. Despite similarities in diet and in blood concentrations of carotenoids, significant differences in macular pigment density (P<0·02) were found for different colored irises (group I,n=38, MP=0·25; group II,n=26, MP=0·32; group III,n=31, MP=0·38). The covariation of iris color and MP indicates that past epidemiologic studies have not adequately determined the independent effects of either factor. The relationship of MP and iris color may be the result of one or two factors: the evolution of a shared tendency to accumulate melanin and carotenoids due to similar environmental pressures (e.g. light and oxygen); and/or MP might be depleted due to the tendency for eyes with light irises to transmit more light than eyes with dark irises, thus causing increased oxidative stress. 相似文献
104.
通过离子注入N+ 诱发基因突变 ,从而获得高产类胡萝卜素红酵母菌株RY 3 9,其出产率较出发菌株RY 3提高 76.2 % ;经复筛和传代实验表明 ,该高产菌株遗传性能较为稳定 ,3代平均类胡萝卜素产量提高了 74.0 %、质量浓度达 1 0 .9mg/L . 相似文献
105.
Low plasma alpha-tocopherol and beta-carotene concentrations have been associated with an increased risk of numerous degenerative diseases, including cancer. Several characteristics that accompany aging, including changes in dietary habits and physiologic capacity, may place elderly populations at a high risk of low plasma antioxidant concentrations. Thus, the present study was undertaken to characterize plasma concentrations of alpha-tocopherol, beta-carotene and several other carotenoids in elderly subjects, to describe the relationship between age and plasma antioxidant concentrations in this population and to compare the concentrations of plasma antioxidants in middle-aged and elderly individuals. The study recruited 94 participants from the Nun Study, a longitudinal study of aging and Alzheimer disease. Women in this population were unique for their advanced age, 77–99 years old, and their comparability across age groups due to the absence of several potential confounders of plasma antioxidant concentrations. The population mean and standard deviation of several plasma carotenoids and alpha-tocopherol concentrations (μg/dl) were as follows: lycopene, 15.0+/− 10.0; beta-carotene, 30.0+/− 19.7; alpha-carotene, 15.0 +/− 9.6; zeaxanthin plus lutein, 22.0+/− 7.4; beta-cryptoxanthin, 14.0 +/− 8.6 and alpha-tocopherol, 980 +/− 310. Concentrations of all analytes, except lycopene, were similar to or higher than those reported for several middle-aged American populations. Lycopene concentrations were significantly lower in the population of sisters as compared with the middle-aged populations and tended to decrease across age groups within the population of sisters. Age appeared to be a relatively minor determinant of plasma alpha-tocopherol and the concentrations of carotenoids, other than lycopene, in this population. Importantly, the plasma concentrations of most carotenoids and alpha-tocopherol in this population of independent elderly women were apparently adequate on the basis of population comparisons. Further studies of this population may define determinants essential for the maintenance of antioxidant status in elderly populations. 相似文献
106.
Panova IG Tatikolov AS Sukhikh GT 《Bulletin of experimental biology and medicine》2007,144(5):681-683
The dynamics of the content albumin and carotenoids in human fetal vitreous body during weeks 16–31 of gestation was studied.
The maximum values of total albumin (1.42 mg) and carotenoids (276 ng) during the studied period were recorded on weeks 20–22.
Albumin concentration peaked during week 17 (2.11×10−4 mol/liter) and carotenoids during weeks 16–17 (about 0.045×10−4 mol/liter) of prenatal development. By week 31, the concentrations and total content of albumin and carotenoids in the vitreous
body decreased. The physiological role of the studied components of the vitreous body for prenatal development of human eye
is discussed.
__________
Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 144, No. 11, pp. 522–525, November, 2007 相似文献
107.
Zora Djuric Jianwei Ren Olga Mekhovich Raghu Venkatranamoorthy Lance K. Heilbrun 《Journal of the American College of Nutrition》2013,32(3):178-187
Objectives: Higher plasma micronutrient levels have been associated with decreased cancer risks. The objective of this study was to determine the relative effects of reduced fat and/or increased fruit-vegetable (FV) intakes on plasma micronutrient levels.Methods: Healthy, premenopausal women with a family history of breast cancer (n = 122) were randomized across four diet arms for one year in a 2 × 2 factorial design study: control, low-fat, high fruit-vegetable and combination low-fat/high FV diets. Levels of plasma micronutrients were measured in plasma at 0, 3, 6 and 12 months.Results: The high FV intervention, regardless of fat intake, significantly increased α-carotene, β-carotene and vitamin C levels in plasma. Only the combination high FV, low-fat intervention significantly increased plasma β-cryptoxanthin and zeaxanthin levels over time. Although α-tocopherol was not affected, a potential concern is that the low-fat intervention resulted in significantly decreased both γ-tocopherol dietary intakes and plasma levels, regardless of whether or not FV intakes were concomitantly increased.Conclusions: Unlike α-tocopherol, γ-tocopherol plasma levels were decreased by a low fat diet, perhaps because γ-tocopherol is not generally added to foods nor widely used in vitamin E supplements. The decreased dietary intakes and plasma levels of γ-tocopherol with a low-fat diet may have implications for health risks since the biological functions of the different tocopherol isomers have been reported to be distinct. 相似文献
108.
Sergio A.R. Paiva Robert M. Russell 《Journal of the American College of Nutrition》2013,32(5):426-433
Carotenoids are natural pigments which are synthesized by plants and are responsible for the bright colors of various fruits and vegetables. There are several dozen carotenoids in the foods that we eat, and most of these carotenoids have antioxidant activity. β-carotene has been best studied since, in most countries it is the most common carotenoid in fruits and vegetables. However, in the U.S., lycopene from tomatoes now is consumed in approximately the same amount as β-carotene. Antioxidants (including carotenoids) have been studied for their ability to prevent chronic disease. β-carotene and others carotenoids have antioxidant properties in vitro and in animal models. Mixtures of carotenoids or associations with others antioxidants (e.g. vitamin E) can increase their activity against free radicals. The use of animals models for studying carotenoids is limited since most of the animals do not absorb or metabolize carotenoids similarly to humans.Epidemiologic studies have shown an inverse relationship between presence of various cancers and dietary carotenoids or blood carotenoid levels. However, three out of four intervention trials using high dose β-carotene supplements did not show protective effects against cancer or cardiovascular disease. Rather, the high risk population (smokers and asbestos workers) in these intervention trials showed an increase in cancer and angina cases. It appears that carotenoids (including β-carotene) can promote health when taken at dietary levels, but may have adverse effects when taken in high dose by subjects who smoke or who have been exposed to asbestos. It will be the task of ongoing and future studies to define the populations that can benefit from carotenoids and to define the proper doses, lengths of treatment, and whether mixtures, rather than single carotenoids (e.g. β-carotene) are more advantageous. 相似文献
109.
A. M. B. Priyadarshani Sanath P. Lamabadusuriya T. R. S. Seneviratne E. R. Jansz H. Peiris 《International journal of food sciences and nutrition》2013,64(4):352-357
Over-consumption of absorbable carotenoids causes hypercarotenemia. Although hypercarotenemia is detected in Sri Lanka, a detailed study on this condition has not been carried out previously. Two millilitres of venous blood was drawn from hypercarotenemic patients (n=8) and examined by high-performance liquid chromatography for carotenoids and vitamin A. A common high-performance liquid chromatographic pattern in serum was shown by six of the cases with β-carotene (9.9–35.7 µg/dl), β-cryptoxanthin and monohydroxy metabolites collectively (5.3–48.5 µg/dl), and six to eight metabolites of dihydroxy, trihydroxy and polyhydroxy metabolites (22.5–282.1 µg/dl). Vitamin A levels were within the normal range (32–61 µg/dl). However, two cases identified were abnormal. The first of these showed low β-carotene (3.5 µg/dl) and no β-cryptoxanthin and monohydroxy metabolites, but normal dihydroxy, trihydroxy and polyhydroxy metabolites (128.2 µg/dl). However, the vitamin A level was high (75.2 µg/dl). The other case showed high β-carotene (212.3 µg/dl) and β-cryptoxanthin (49.3 µg/dl) but no normal monohydroxy, dihydroxy, trihydroxy and polyhydroxy metabolites. Instead there was an atypical metabolite (343.9 µg/dl). According to the present study, excessive intake of boiled, homogenized carrot and ripe papaw is the main causative factor for hypercarotenemia. Over-consumption of carotenoids-rich plant foods may be complicated in the case of individuals having defects of either the control of the 15,15′-dioxygenase activity or metabolism of carotenoids. 相似文献
110.
《International journal of food sciences and nutrition》2013,64(4):381-394
AbstractThe present research aimed at evaluating the vitamin C, total phenolic content (TPC), phenolic compounds, carotenoids, and chlorophyll contents, as well as antioxidant activity (AAC) of six Actinidia species fruit. Vitamin C, phenolic compounds, carotenoids and chlorophylls were measured using high-performance liquid chromatography. TPC was determined using the Folin–Ciocalteau reagent, and AAC using 2,2-diphenyl-1-picryl hydrazyl (DPPH) assay. The highest concentrations of vitamin C and TPC were found for Actinidia kolomikta fruit (1008.3 and 634.1 mg/100 g fresh weight [FW], respectively). Among phenolic compounds, seven phenolic acids and three flavonoids were identified. The 2,5-dihydroxybenzoic acid prevailed in A. kolomikta (425.54 mg/100 g FW), while tannic acid dominated in other species (4.63–100.43 mg/100 g FW). The largest amounts of chlorophylls and carotenoids were identified as Actinidia macrosperma (4.02 and 2.09 mg/100 g FW, respectively). The AAC of fruit extracts decreased in the order of A. kolomikta >?Actinidia purpurea >?Actinidia melanandra >?A. macrosperma >?Actinidia arguta >?Actinidia deliciosa according to the DPPH assay. 相似文献