全文获取类型
收费全文 | 73778篇 |
免费 | 4556篇 |
国内免费 | 135篇 |
学科分类
医药卫生 | 78469篇 |
出版年
2023年 | 314篇 |
2022年 | 557篇 |
2021年 | 1015篇 |
2020年 | 743篇 |
2019年 | 1069篇 |
2018年 | 1299篇 |
2017年 | 1112篇 |
2016年 | 1393篇 |
2015年 | 1470篇 |
2014年 | 1955篇 |
2013年 | 2561篇 |
2012年 | 3837篇 |
2011年 | 3922篇 |
2010年 | 2123篇 |
2009年 | 2232篇 |
2008年 | 3510篇 |
2007年 | 3701篇 |
2006年 | 3574篇 |
2005年 | 3469篇 |
2004年 | 2978篇 |
2003年 | 2885篇 |
2002年 | 2536篇 |
2001年 | 2496篇 |
2000年 | 2455篇 |
1999年 | 2231篇 |
1998年 | 935篇 |
1997年 | 817篇 |
1996年 | 772篇 |
1995年 | 633篇 |
1994年 | 590篇 |
1993年 | 572篇 |
1992年 | 1489篇 |
1991年 | 1460篇 |
1990年 | 1416篇 |
1989年 | 1279篇 |
1988年 | 1208篇 |
1987年 | 1097篇 |
1986年 | 1076篇 |
1985年 | 1010篇 |
1984年 | 701篇 |
1983年 | 566篇 |
1982年 | 329篇 |
1981年 | 338篇 |
1979年 | 578篇 |
1978年 | 350篇 |
1977年 | 326篇 |
1975年 | 346篇 |
1974年 | 377篇 |
1973年 | 356篇 |
1972年 | 368篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
P. Jakobsson L. Jorfeldtt H. von Schenck 《Clinical physiology and functional imaging》1995,15(4):319-329
Summary. In order to investigate fat metabolism and the regulation of lipolysis and blood fuel metabolites by insulin, nine patients with chronic obstructive pulmonary disease (COPD) with chronic hypoxaemia and seven healthy control subjects of similar age were investigated by determination of the turnover rate of free fatty acids (TOR), using 1-14C-oleic acid as a tracer, and arterial concentrations of FFA, glycerol and 3-hydroxybutyrate. The measurements were performed in the basal state and during insulin and glucose infusion, aiming at euglycaemia at insulin levels of 50 and 100 mU l-1. The subjects' ages were 64±2.7 and 66±1.1 (mean±SEM) years in the COPD and control groups, respectively. TOR was 0.73±0.06 and 0.52±0.02 mmol min-1 (P<0.05) in the basal state, 0.33±0.04 and 0.30±0.02 at an insulin level of 50 mU I-1 and 0.32±0.08 and 0.24±0.02 at an insulin level of 100 mU I-1, in the COPD and control groups, respectively. Arterial FFA concentration was 0.98±0.08 and 0.75±0.06 mmol 1-1 (P<0.05) in the basal state in the COPD and control groups, respectively. During the clamp, the decrease in FFA mirrored that in TOR. The results show that the state of lipolysis is increased in severe COPD patients with chronic hypoxaemia. Furthermore, the results suggest a reduced effect of insulin in lipolysis. 相似文献
82.
83.
A Mertens W G Friebe B Müller-Beckmann W Kampe L Kling W von der Saal 《Journal of medicinal chemistry》1990,33(10):2870-2875
A series of substituted indolyldihydropyridazinones and related compounds 1-18 were synthesized and evaluated for positive inotropic activity. In rats, most of these indole derivatives produced a dose-related increase in myocardial contractility with little effect on heart rate and blood pressure. Compound 13, 4,5-dihydro-5-methyl-6-(2-pyridin-4-yl-1H-indol-5-yl)pyrazin-3(2H) -one (BM 50.0430), was further investigated in cats. The increase in contractility in this animal model was not mediated via stimulation of beta-adrenergic receptors. After oral administration of 1 mg/kg to conscious dogs, compound 13 and pimobendan were still active after 6.5 h. However, the cardiotonic effect of 13 was at least 2-fold that of pimobendan after this period of time. The structural requirements necessary for optimal cardiotonic activity within this novel class of indole derivatives are a heterocyclic aromatic ring in position 2, a hydrogen or a methyl group in position 3, and a dihydropyridazinone ring system in position 5 of the indole. 相似文献
84.
Andrea von Berg Renate Engelstätter Predrag Minic Miodrag Sréckovic Maria Luz Garcia Garcia Tadeusz Lato Jan H. Vermeulen Stefan Leichtl Stefan Hellbardt Thomas D. Bethke 《Pediatric allergy and immunology》2007,18(5):391-400
Ciclesonide is an onsite-activated inhaled corticosteroid (ICS) for the treatment of asthma. This study compared the efficacy, safety and effect on quality of life (QOL) of ciclesonide 160 microg (ex-actuator; nominal dose 200 microg) vs. budesonide 400 microg (nominal dose) in children with asthma. Six hundred and twenty-one children (aged 6-11 yr) with asthma were randomized to receive ciclesonide 160 microg (ex-actuator) once daily (via hydrofluoroalkane metered-dose inhaler and AeroChamber Plus spacer) or budesonide 400 microg once daily (via Turbohaler) both given in the evening for 12 wk. The primary efficacy end-point was change in forced expiratory volume in 1 s (FEV1). Additional measurements included change in daily peak expiratory flow (PEF), change in asthma symptom score sum, change in use of rescue medication, paediatric and caregiver asthma QOL questionnaire [PAQLQ(S) and PACQLQ, respectively] scores, change in body height assessed by stadiometry, change in 24-h urinary cortisol adjusted for creatinine and adverse events. Both ciclesonide and budesonide increased FEV1, morning PEF and PAQLQ(S) and PACQLQ scores, and improved asthma symptom score sums and the need for rescue medication after 12 wk vs. baseline. The non-inferiority of ciclesonide vs. budesonide was demonstrated for the change in FEV1 (95% confidence interval: -75, 10 ml, p = 0.0009, one-sided non-inferiority, per-protocol). In addition, ciclesonide and budesonide showed similar efficacy in improving asthma symptoms, morning PEF, use of rescue medication and QOL. Ciclesonide was superior to budesonide with regard to increases in body height (p = 0.003, two-sided). The effect on the hypothalamic-pituitary-adrenal axis was significantly different in favor of ciclesonide treatment (p < 0.001, one-sided). Both ciclesonide and budesonide were well tolerated. Ciclesonide 160 microg once daily and budesonide 400 microg once daily were effective in children with asthma. In addition, in children treated with ciclesonide there was significantly less reduction in body height and suppression of 24-h urinary cortisol excretion compared with children treated with budesonide after 12 wk. 相似文献
85.
86.
87.
88.
Floriana S Luppino Edward Grooters Francisca T de Bru?ne Aeilko H Zwinderman Andel G L van der Mey 《Otology & neurotology》2006,27(7):962-968
OBJECTIVE: Conservative treatment in vestibular schwannomas is mainly dependent on optimal tumor size determination. The first objective of this study was to establish interobserver and intraobserver variability and the accuracy and reproducibility of three different measurement methods: one bidimensional and two volumetrical. The second objective was to evaluate the influence of the use of different magnetic resonance imaging (MRI) slice thickness and the influence of patient's repositioning on the measurements' outcome. STUDY DESIGN: Two consecutive studies have been prospectively performed, both mainly concerning volumetrical measurements. SETTING: Both studies were performed in a tertiary academic, multidisciplinary center. PATIENTS: In the first study, 19 patients were included between March 1996 and May 2002, with a total of 52 scans. The second study comprised 14 patients. All patients in the first study had at least two MRI examinations performed according to a standard protocol (T1-weighted gadolinium-enhanced, slice thickness of 3 mm, and interslice gap of 0.3 mm). The population in the second study underwent a conservative wait and scan (W&S) treatment. METHODS: Both studies are discussed separately. In the first study, all scans were measured by four investigators, two of whom performed the measurements twice using three different methods. The first method concerns a manually performed bidimensional surface measurement along the petrous pyramid. The second method concerns a semiautomatic volumetrical measurement on a computer, relying on contour detection, and the last method concerns a fully automatic volume reconstruction also performed on a computer using different gray shade scales.All 14 patients included in the second study underwent three magnetic examinations. Three different T1-weighted gadolinium-enhanced sequences were used: the first using a slice thickness of 1 mm, the second again with 1-mm slice thickness but after having repositioned the patient. In the third sequence, a slice thickness of 3 mm was used. All scans were measured by two investigators using the three different methods, as described previously. RESULTS: The manual surface method shows large intraobserver variability, and its reproducibility is significantly lower compared with volume measurements. Because of a relatively large systematic error in small tumors, sensitivity of growth detection is low. Both volumetrical methods are hardly interobserver- and intraobserver-dependent, and the gray shade method turned out to be the most accurate. Radiologic progression is only significant at a volume increase of at least 50%. The influence of patient repositioning is negligible, whereas the use of 1-mm slice thickness seems to be superior to a 3-mm slice thickness. CONCLUSION: The volumetrical gray shade method is the most accurate method to detect early tumor progression. As tumor increase of at least 50% is needed to be able to speak of statistically significant tumor growth, the absence of radiologic progression does not mean that there is no tumor growth. Repositioning of the patient has no influence on the measurements' outcome, whereas for optimal magnetic resonance imaging examinations, a 1-mm slice thickness protocol seems to be superior. 相似文献
89.
90.
J L Vincent P Van der Linden M Domb S Blecic G Azimi A Bernard 《Anesthesia and analgesia》1987,66(6):565-571
The hemodynamic effects of dopamine and dobutamine (at doses of 6 micrograms X kg-1 X min-1) were compared during fluid resuscitation from septic shock induced by endotoxin (3 mg/kg) in the dog. In the first part of the study, when a standard amount of saline solution was infused (in 24 dogs), dopamine infusion resulted in higher cardiac filling pressures than did dobutamine infusion, whereas dobutamine infusion resulted in higher cardiac output. In the second part of the study, when fluid infusion was titrated to maintain pulmonary artery balloon-occluded pressure at constant level (in 24 dogs), the total amount of fluids was significantly greater with dobutamine than when dopamine was used (109 +/- 13 vs 71 +/- 10 ml/kg). The combination of dobutamine with fluids resulted in significantly greater stroke volume (39.6 +/- 3.8 vs 21.0 +/- 4.0 ml, P less than 0.05) and oxygen consumption (194 +/- 18 vs 144 +/- 8 ml/min, P less than 0.05). The different effects of dopamine and dobutamine on cardiac filling pressures can be due to differences in effects on myocardial contractility, ventricular afterload, and cardiac compliance. This experimental study indicates that when fluid therapy is combined with adrenergic agents in resuscitation from septic shock, dobutamine can be associated with higher cardiac output and oxygen transport and can result in higher tissue oxygen consumption than dopamine. 相似文献