全文获取类型
收费全文 | 3419篇 |
免费 | 218篇 |
国内免费 | 81篇 |
专业分类
耳鼻咽喉 | 3篇 |
儿科学 | 85篇 |
妇产科学 | 30篇 |
基础医学 | 265篇 |
口腔科学 | 30篇 |
临床医学 | 183篇 |
内科学 | 598篇 |
皮肤病学 | 13篇 |
神经病学 | 70篇 |
特种医学 | 38篇 |
外科学 | 162篇 |
综合类 | 257篇 |
预防医学 | 1555篇 |
眼科学 | 5篇 |
药学 | 275篇 |
2篇 | |
中国医学 | 48篇 |
肿瘤学 | 99篇 |
出版年
2024年 | 5篇 |
2023年 | 91篇 |
2022年 | 184篇 |
2021年 | 199篇 |
2020年 | 191篇 |
2019年 | 161篇 |
2018年 | 153篇 |
2017年 | 100篇 |
2016年 | 128篇 |
2015年 | 91篇 |
2014年 | 239篇 |
2013年 | 282篇 |
2012年 | 171篇 |
2011年 | 203篇 |
2010年 | 149篇 |
2009年 | 159篇 |
2008年 | 201篇 |
2007年 | 132篇 |
2006年 | 115篇 |
2005年 | 85篇 |
2004年 | 69篇 |
2003年 | 53篇 |
2002年 | 54篇 |
2001年 | 48篇 |
2000年 | 34篇 |
1999年 | 36篇 |
1998年 | 29篇 |
1997年 | 25篇 |
1996年 | 14篇 |
1995年 | 23篇 |
1994年 | 21篇 |
1993年 | 17篇 |
1992年 | 20篇 |
1991年 | 23篇 |
1990年 | 21篇 |
1989年 | 15篇 |
1988年 | 12篇 |
1987年 | 16篇 |
1986年 | 11篇 |
1985年 | 26篇 |
1984年 | 18篇 |
1983年 | 24篇 |
1982年 | 18篇 |
1981年 | 15篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1972年 | 5篇 |
排序方式: 共有3718条查询结果,搜索用时 15 毫秒
1.
2.
《Nutrition reviews》1987,45(10):246-248
Increasing dietary 18:2 n-6/18:3 n-3 causes similar relative changes in fatty acid profiles of phosphatidylethanolamine and phosphatidylcholine from rat neural and erythrocyte membranes. 相似文献
3.
The effects of 10% dietary xylitol supplementation in ovariectomized rats were studied on the degradation of bone organic
and inorganic structures. The osseal concentrations of hydroxyproline, pyridinoline, and deoxypyridinoline were analyzed by
high-performance liquid chromatography. Bone resorption was measured in [3H]tetracycline-prelabeled rats by urinary excretion of 3H, and by the amount of 3H preserved in bone. Bone trabeculation was measured by a computer image analyzer from sections stained by the method of von
Kossa. The amount of collagen in bone organic fraction was lower in ovariectomized rats as compared with the sham-operated
controls. This most likely is partly a consequence of an increased resorption, and partly a consequence of a higher proportion
of immature periosteal bone in the ovariectomized animals, leading to a higher ratio of noncollagenous protein to collagen.
The number of pyridinium crosslinks was lower in proportion, indicating no selective changes in the structure of collagen.
Dietary xylitol significantly retarded the ovariectomy-associated decrease in the relative amount of collagen and the number
of its mature crosslinks. Ovariectomy doubled the excretion of 3H and caused a significant decrease in the amount of 3H preserved in bone; both these changes were significantly retarded by the 10% dietary xylitol supplementation. Ovariectomy
significantly decreased the volume of bone trabeculae, but this effect was also significantly inhibited by the xylitol supplementation
in the diet. In conclusion, these findings suggest a dietary xylitol-induced normalizing effect on the rate of bone turnover
in ovariectomized rats.
Received: 12 February 1996 / Accepted: 20 August 1996 相似文献
4.
Because of concern about psoralen-induced phototoxicity and photocarcinogenesis, we investigated the effects of dietary lipids in a mouse model in which 8-methoxypsoralen (8-MOP) and UVA (PUVA) therapy has been shown to be carcinogenic. SKH-Hr-1 hairless albino mice were fed diets containing either omega-3 or omega-6 fatty-acid sources (menhaden oil and corn oil, respectively). After 2 weeks on the diets, the mice were treated topically with 8-MOP and then exposed to UVA (5 J/cm2). Mice receiving the omega-3 fatty-acid source exhibited a marked decrease in inflammatory response and a more rapid repair, as expressed both grossly and microscopically. In support of the latter response, i.e. repair, ornithine decarboxylase activity was about 20% greater in animals receiving the omega-3 fatty-acid source. The effects of the dietary fatty acid sources on PUVA tumorigenesis were examined in long-term studies in which animals were treated topically with 0.01% 8-MOP thrice weekly after which they were exposed to UVA (1 J/cm2). These studies indicated that a dietary lipid rich in omega-3 fatty acid and known to exhibit anti-inflammatory properties can markedly ameliorate the course of PUVA toxicity but does not impede the course of PUVA tumorigenesis 相似文献
5.
This paper reviews the literature on the role of dietary fat in calorie intake and body weight gain in humans and laboratory animals. An overview of 40 animal studies which compared growth on high-fat (HF) and high-carbohydrate (HC) solid/powdered diets indicated that the HF diet elicited greater weight gain in 33 out of 40 studies. Enhanced growth on the HF diet was often, but not exclusively, attributable to greater caloric intake. Additional evidence for the growth-enhancing effect of HF diets emerges from "diet option" and "supermarket" feeding studies in rats, and experimental and epidemiological studies in humans. Three principal factors that contribute to the different responses to HF and HC diets are (a) caloric density, (b) sensory properties and palatability, and (c) postabsorptive processing. It is concluded that both calorie intake and metabolic energy expenditure are biased towards weight gain when a HF diet is consumed, and that the high caloric density of high-fat diets plays a primary role in weight gain. Humans may be biologically predisposed to gain weight when a HF diet is consumed. 相似文献
6.
Broiler chicks were provided choices of synthetic diets (a) adequate or low in lysine, and (b) adequate in or devoid of lysine. In each case, chicks consumed some of each diet offered, but preference was shown for the adequate lysine diet. Growth rates of chicks given choices ranged from 80% of that of chicks fed an adequate lysine diet with no choice for two weeks, then growth rates fell to about 60% of those fed adequate lysine. In another study, chicks were fed a diet devoid of lysine but were offered pure L-lysine HCl in a separate feeder. These chicks selected some of the supplementary lysine, but their body weights were only 68% of the body weight of chicks fed an adequate lysine diet after 21 days. Chicks given a choice of diets prepared with an adequate quantity of either L- or D-lysine preferred with L-lysine diet but did not select sufficient quantity to reach normal growth. These observations indicate that chicks can discern the presence of L-lysine in diets or separately, but will not select sufficient quantity for maximum growth potential. A diet prepared with D-lysine was more acceptable than one completely devoid of lysine, suggesting some sensory recognition for lysine. 相似文献
7.
PurposeSubstantial efforts have gone into reducing the physiological and psychological harm of obesity in youth, but few studies have reviewed the factors contributing to adherence to pediatric weight management programs. The attrition rates to programs offering multiple components to address BMI improvement and healthy lifestyle change among youth are quite high. The purpose of this study is to review the literature for factors contributing to adherence to these programs among children and youth with obesity and determine pooled effect of these factors.MethodsA systematic literature search and meta-analysis was conducted through the PubMed database on pediatric weight management interventions offering at least physical activity and dietary support for obese youth aged 10–17 years, where variables contributing to adherence were reported. Only those studies achieving a threshold of methodological rigour were included.ResultsAltogether, seven studies were included in the analysis. There was a pooled RR of lower socioeconomic status on non-adherence of 1.34 [95% confidence intervals 1.19–1.52] and poorer mental health on non-adherence of 1.12 [95% confidence intervals 1.08–1.17].ConclusionIt is important to address barriers related to lower socioeconomic status in pediatric weight management programs to increase adherence. Further, addressing supports for those with poorer mental health can reduce the risk of non-adherence in multi-disciplinary programs targeting youth with obesity. 相似文献
8.
9.
Gastric cancer etiology: a biochemical hypothesis. 总被引:1,自引:0,他引:1
We have proposed a two-stage biochemical model for the etiology of "intestinal" gastric cancer. The model postulates that the gastric mucosal barrier is biochemically pierced as a result of chemical interactions between the mucoproteins and mucopolysaccharides of the barrier and ingested polysaccharrides (starches). This would allow the growth of gastric flora which could produce carcinogenic nitrosamines and/or nitrosamides. Observational and experimental evidence in favor of the model is provided. The model suggests various research initiatives, the results of which might provide the basis for biochemical and physiological methods for the prevention and/or treatment of gastric cancer. Various ways in which the model may be tested are also noted. 相似文献
10.
Diarrhoea during enteral feeding in the critically ill: A comparison of feeds with and without fibre 总被引:4,自引:0,他引:4
This randomised double-blind study examined the frequency of diarrhoea in intensive care unit patients given a fibre-containing feed, Enrich, and a fibre-free feed, Ensure. A daily diarrhoea score was calculated from the frequency, volume and consistency of the stools. A score greater than 12 indicated diarrhoea, and greater than 50 severe diarrhoea. Ninety one patients met the criteria for participation: Enrich 45, Ensure 46. The groups were similar in age, sex ratio, feed volume, antibiotic usage, upper gastro-intestinal bleeding prophylaxis and plasma albumin concentrations. Diarrhoea occurred in 16 patients given Enrich and 13 given Ensure, severe diarrhoea affecting 5 and 9 respectively (NS). Forty seven of 343 (14%) Enrich feeding days and 51 of 342 (15%) Ensure feeding days were complicated by diarrhoea — severe diarrhoea: 8 and 12 feeding days (NS). We conclude soy polysaccharide (21 g/L) did not reduce diarrhoea in intensive care unit patients given enteral feeds. 相似文献