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51.
Objectives
The aims of this paper are threefold: (1) to summarize the research examining the effects of caffeine on isokinetic strength, (2) pool the effects using a meta-analysis, and (3) to explore if there is a muscle group or a velocity specific response to caffeine ingestion.Design
Meta-analysis.Methods
PubMed/MEDLINE, Scopus, and SPORTDiscus were searched using relevant terms. The PEDro checklist was used for the assessment of study quality. A random-effects meta-analysis of standardized mean differences (SMDs) was done.Results
Ten studies of good and excellent methodological quality were included. The SMD for the effects of caffeine on strength was 0.16 (95% CI = 0.06, 0.26; p = 0.003; +5.3%). The subgroup analysis for knee extensor isokinetic strength showed a significant difference (p = 0.004) between the caffeine and placebo conditions with SMD value of 0.19 (95% CI = 0.06, 0.32; +6.1%). The subgroup analysis for the effects of caffeine on isokinetic strength of other, smaller muscle groups indicated no significant difference (p = 0.092) between the caffeine and placebo conditions. The subgroup analysis for knee extensor isokinetic strength at angular velocities of 60° s?1 and 180° s?1 showed a significant difference between the caffeine and placebo conditions; however, no significant effect (p = 0.193) was found at an angular velocity of 30° s?1.Conclusions
This meta-analysis demonstrates that acute caffeine ingestion caffeine may significantly increase isokinetic strength. Additionally, this meta-analysis reports that the effects of caffeine on isokinetic muscular strength are predominantly manifested in knee extensor muscles and at greater angular velocities. 相似文献52.
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54.
Vasiliy I Reshetnyak Igor V Maev Alexandr I Burmistrov Igor A Chekmazov Tatiana I Karlovich 《World journal of gastroenterology : WJG》2020,26(15):1691-1707
The review presents the data accumulated for more than 20 years of research of torque teno virus(TTV). Its molecular genetic structure, immunobiology,epidemiology, diagnostic methods, possible replication sites, and pathogenicity factors are described. TTV is a virus that is frequently detectable in patients with different viral hepatitides, in cases of hepatitis without an obvious viral agent, as well as in a healthy population. There is evidence suggesting that biochemical and histological changes occur in liver tissue and bile duct epithelium in TTV monoinfection. There are sufficient histological signs of liver damage, which confirm that the virus can undergo a replicative cycle in hepatocytes. Along with this, cytological hybridization in TTV-infected cells has shown no substantial cytopathic(cell-damaging) effects that are characteristic of pathogenic hepatotropic viruses. Studying TTV has led to the evolution of views on its role in the development of human pathology. The first ideas about the hepatotropism of the virus were gradually reformed as new data became available on the prevalence of the virus and its co-infection with other viruses, including the viruses of the known types of hepatitides. The high prevalence of TTV in the human population indicates its persistence in the body as a virome and a nonpathogenic virus. It has recently been proposed that the level of TTV DNA in the blood of patients undergoing organ transplantation should be used as an endogenous marker of the body's immune status. The available data show the polytropism of the virus and deny the fact that TTV can be assigned exclusively to hepatitis viruses. Fortunately, the rare detection of the damaging effect of TTV on hepatic and bile duct epithelial cells may be indirect evidence of its conditionally pathogenic properties. The ubiquity of the virus and the variability of its existence in humans cannot put an end to its study. 相似文献
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E. A. Charriere T. Beutler M. Caride P. Mordasini T. E. Orr P. K. Zysset 《European spine journal》2006,15(1):74-81
A comparison between an unconstrained and a partially constrained system for in vitro biomechanical testing of the L5-S1 spinal unit was conducted. The objective was to compare the compliance and the coupling of the L5-S1 unit measured with an unconstrained and a partially constrained test for the three major physiological motions of the human spine. Very few studies have compared unconstrained and partially constrained testing systems using the same cadaveric functional spinal units (FSUs). Seven human L5-S1 units were therefore tested on both a pneumatic, unconstrained, and a servohydraulic, partially constrained system. Each FSU was tested along three motions: flexion-extension (FE), lateral bending (LB) and axial rotation (AR). The obtained kinematics on both systems is not equivalent, except for the FE case, where both motions are similar. The directions of coupled motions were similar for both tests, but their magnitudes were smaller in the partially constrained configuration. The use of a partially constrained system to characterize LB and AR of the lumbosacral FSU decreased significantly the measured stiffness of the segment. The unconstrained system is todays gold standard for the characterization of FSUs. The selected partially constrained method seems also to be an appropriate way to characterize FSUs for specific applications. Care should be taken using the latter method when the coupled motions are important. 相似文献
58.
Drost MR Heemskerk AM Strijkers GJ Dekkers EC van Kranenburg G Nicolay K 《Pflügers Archiv : European journal of physiology》2003,447(3):371-375
The goal of the present study was to develop and evaluate an isometric dynamometer for measuring mouse ankle flexor torque after electric stimulation of the nerve. The dynamometer was to be used within an magnetic resonance (MR) apparatus and should require minimal surgical intervention. To quantify the effect of the magnetic field on contractile parameters, measurements were performed both outside and inside the MR apparatus. The effect of magnetic field gradient switching that accompanies rapid MR scanning was tested also. The set-up required no surgical intervention except for chronic implantation of an electrode. The dynamometer has a high mechanical frequency response (270 Hz). Measured muscle strengths were identical outside and inside the MR scanner. However, during fast magnetic field gradient switching, the variability increased and the measured strength decreased slightly (7%). The noise level of the dynamometer (0.02–0.03 N·mm) was low compared with the strength of the dorsal flexors (2 N·mm). Fast gradient switching increased the noise level (0.07 N·mm). The dynamometer had no observable adverse effects on the quality of the MR images of the mouse hind limb. We conclude that the dynamometer enables accurate measurements of mechanical muscle performance during exercise protocols within an MR apparatus under physiological conditions. 相似文献
59.
Summary Contraction work (CW) and peak torque (PT) of maximum isokinetic plantar flexions were measured in clinically healthy subjects randomly chosen from the official census list of Umeå, Sweden, in three groups: 40–44, 50–54 and 60–64 years of age, with similar proportions of men and women. Maximum isokinetic plantarflexions were performed at angular velocities of 30, 60, 120 and 180 · s–1. Body-weight, height and crural circumference were measured. Subjects rated their levels of leisure and occupational activities.To establish formulae to predict CW and PT, stepwise regression procedures were applied. The predictive powers (r
2) of the formulae which incorporated age, sex and crural circumference, were higher for PT (30 · s–1: 0.82, 60 · s–1: 0.79, 120 · s–1: 0.75, 180 · s–1: 0.56) than for CW (30 s–1: 0.63, 60 s–1: 0.63, 120 s–1: 0.60, 180 s–1: 0.52). Thus the part of the variance explained decreased with increasing angular velocity, but more than 50% was still explained at 180 s–1.The results indicate that the mechanical output of the plantar flexors is predictable. 相似文献
60.
H. E. J. Veeger E. M. C. Lute K. Roeleveld L. H. V. van der Woude 《European journal of applied physiology》1992,64(2):158-164
Summary To compare physiological responses and propulsion technique of able bodied subjects with no prior experience of wheelchairs (AB) and wheelchair dependent subjects (WD), ten AB and nine WD performed a 30-s sprint test in a wheelchair ergometer. The WD had spinal cord injuries with a lesion at T8 or lower. The WD and AB did not show significantly different physiological responses. The power values averaged for the right wheel over the 30 s of the test were 50.2 (SD 14.7) W and 48.0 (SD 4.4) W for WD and AB, respectively. No significant differences in torque application could be discerned, although WD subjects seemed to have a more flattened torque curve with a smaller negative deflection at the beginning of the push. The WD applied a significantly higher horizontal propulsive force to the handrims but did not apply force more effectively. The percentages of effective force to total propulsive force were 61 (SD 16)% for WD and 57 (SD 4)% for AB. With regard to the kinematic parameters, AB followed the handrims significantly longer than WD (end angle AB 65°, WD 44°), started the push phase with their arms more in retroflexion and flexed their trunks further forward. The AB did however show a movement pattern comparable to that of wheelchair athletes measured in a comparable experiment. It could not be decided conclusively that inexperience in wheelchair propulsion led to a less effective propulsion technique. Despite the selection of WD with respect to lesion level, interindividual differences in terms of level of training may have been responsible for the absence of significant results. 相似文献