全文获取类型
收费全文 | 1292篇 |
免费 | 136篇 |
国内免费 | 2篇 |
专业分类
耳鼻咽喉 | 12篇 |
儿科学 | 97篇 |
妇产科学 | 29篇 |
基础医学 | 166篇 |
口腔科学 | 17篇 |
临床医学 | 148篇 |
内科学 | 229篇 |
皮肤病学 | 13篇 |
神经病学 | 59篇 |
特种医学 | 174篇 |
外科学 | 91篇 |
综合类 | 26篇 |
预防医学 | 171篇 |
眼科学 | 12篇 |
药学 | 140篇 |
中国医学 | 1篇 |
肿瘤学 | 45篇 |
出版年
2021年 | 7篇 |
2019年 | 7篇 |
2018年 | 19篇 |
2017年 | 10篇 |
2016年 | 9篇 |
2015年 | 16篇 |
2014年 | 18篇 |
2013年 | 43篇 |
2012年 | 32篇 |
2011年 | 46篇 |
2010年 | 37篇 |
2009年 | 31篇 |
2008年 | 41篇 |
2007年 | 36篇 |
2006年 | 35篇 |
2005年 | 42篇 |
2004年 | 37篇 |
2003年 | 32篇 |
2002年 | 26篇 |
2001年 | 30篇 |
2000年 | 37篇 |
1999年 | 39篇 |
1998年 | 41篇 |
1997年 | 36篇 |
1996年 | 39篇 |
1995年 | 38篇 |
1994年 | 31篇 |
1993年 | 32篇 |
1992年 | 33篇 |
1991年 | 30篇 |
1990年 | 40篇 |
1989年 | 45篇 |
1988年 | 43篇 |
1987年 | 28篇 |
1986年 | 22篇 |
1985年 | 26篇 |
1984年 | 24篇 |
1983年 | 30篇 |
1982年 | 33篇 |
1981年 | 16篇 |
1980年 | 20篇 |
1979年 | 26篇 |
1978年 | 18篇 |
1977年 | 18篇 |
1976年 | 20篇 |
1975年 | 15篇 |
1974年 | 8篇 |
1973年 | 7篇 |
1972年 | 9篇 |
1969年 | 8篇 |
排序方式: 共有1430条查询结果,搜索用时 46 毫秒
81.
1 Valproic acid or phenytoin were added to fresh human serum in varying concentrations and their binding characteristics determined by the method of Scatchard (1949). 2 Changes in serum albumin binding were investigated for phenytoin in the presence of 280, 560, 1050 and 2100 mumol l-1 valproic acid, and for valproic acid in the presence of 40, 120, 280 and 480 mumol l-1 phenytoin. 3 Phenytoin appeared to bind to a single site on the albumin molecule and could be competitively displaced from this site by concentrations of valproic acid above 280 mumol l-1. 4 At high concentrations of valproic acid, the affinity of phenytoin for albumin was greatly decreased but the number of available binding sites was increased from one to four. 5 Valproic acid was bound to two high affinity and five low affinity binding sites but the latter were not detectable at valproic acid concentrations below 2100 mumol l-1. 6 Phenytoin displaced valproic acid from its high affinity binding sites, although this was statistically significant only at a concentration of 480 mumol l-1 phenytoin. 相似文献
82.
83.
84.
Regional myocardial dysfunction: evaluation of patients with prior myocardial infarction with fast CT 总被引:1,自引:0,他引:1
Lipton MJ; Farmer DW; Killebrew EJ; Bouchard A; Dean PB; Ringertz HG; Higgins CB 《Radiology》1985,157(3):735-740
A prototype ultrafast cine computed tomographic (CT) scanner, designed specifically for cardiac imaging, was used to evaluate a preliminary series of patients with prior myocardial infarction (n = 21) and a control group without coronary artery disease (n = 5). Multilevel 50-msec CT scan exposures were obtained during peripheral intravenous bolus injections of contrast medium. A comparison was made between cine-CT scans and standard left ventriculographic images in assessing segmental left ventricular motion. Results indicate that cine CT, performed at sufficiently rapid speeds (20 scans per second) to allow useful analysis of regional ventricular wall motion, can provide adequate image quality. Analysis of 110 segments revealed a good correlation (90.9%) between the two techniques in characterizing normal from abnormal regional wall motion. Cine CT, based on this initial study, demonstrates considerable potential for evaluating not only cardiac chamber dimensions but also segmental wall dynamics. 相似文献
85.
The effect of “selective” β-adrenoceptor blocking drugs on the myocardial circulation 总被引:2,自引:2,他引:0 下载免费PDF全文
1. A comparison has been made of the effects of a relatively specific beta(1)-adrenoceptor blocking drug (practolol) and a relatively specific beta(2)-adrenoceptor blocking drug (butoxamine) on myocardial and general haemodynamics in anaesthetized cats.2. Practolol, in a dose (10 mg/kg, intravenously) which had little effect on arterial pressure, heart rate, myocardial blood flow or myocardial vascular resistance, markedly reduced the effects of isoprenaline infusions on heart rate, aortic dp/dt, myocardial blood flow, vascular resistance and metabolic heat production, and the cardiac effort index. Isoprenaline induced vasodepression was unaffected.3. Butoxamine (5 mg/kg, intravenously) decreased heart rate, aortic dp/dt, the cardiac effort index and myocardial blood flow and increased myocardial vascular resistance. This is taken as further evidence for the existence of beta(2)-adrenoceptors in the myocardial microcirculation.4. After butoxamine, the effects of isoprenaline on myocardial blood flow, myocardial vascular resistance and heart rate were unaffected but the peripheral vasodilator effect was abolished. The effects on aortic dp/dt and the cardiac effort index were potentiated.5. It is concluded that the effect of isoprenaline in increasing myocardial blood flow is due predominantly to increased cardiac work and oxygen consumption and that practolol, since it has little direct effect on myocardial blood flow yet abolishes the cardiac stimulant and oxygen wasting effects of released catecholamines, has properties which indicate that it should be an effective and safe anti-anginal drug. 相似文献
86.
87.
88.
89.
McNaughton SA Mishra GD Bramwell G Paul AA Wadsworth ME 《European journal of clinical nutrition》2005,59(3):341-352
OBJECTIVE: The aim of this study is to evaluate the consistency of dietary patterns assessed through the use of a dietary recall and a 5-day food diary. DESIGN: Participants (n = 2265) of a longitudinal study of health and development completed 48-h dietary recall at interview, followed by a 5-day food diary and with the 24 h immediately preceding the interview analysed separately as a 24-h recall. Mean intakes of foods and nutrients were calculated and dietary patterns were assessed using exploratory factor analysis, using the method of principal components. Paired t-tests and correlation coefficients were used to compare the three dietary assessment methods. RESULTS: Five distinct dietary patterns were identified using the food diary and the 48-h recall but were less consistent on the 24-h recall. Correlations between factor scores on the 48-h recall and the food diary (r = 0.13-0.67) were higher than those between the 24-h recall and food diary (r = -0.01-0.59). The recall methods were effective at ranking subjects according to food and nutrient intakes, with the 48-h recall and food diary showing higher correlations in both males and females. CONCLUSIONS: This study indicates that a 48-h recall effectively characterises dietary patterns in British adults when compared to a food diary and ranks participants appropriately with respect to most nutrients and foods and is superior to a single 24-h recall. These results have implications for longitudinal studies where maximising response rates to repeat dietary assessment tools is essential. 相似文献
90.