全文获取类型
收费全文 | 21601篇 |
免费 | 2162篇 |
国内免费 | 466篇 |
专业分类
耳鼻咽喉 | 195篇 |
儿科学 | 368篇 |
妇产科学 | 220篇 |
基础医学 | 2286篇 |
口腔科学 | 443篇 |
临床医学 | 2751篇 |
内科学 | 2867篇 |
皮肤病学 | 155篇 |
神经病学 | 1794篇 |
特种医学 | 1527篇 |
外国民族医学 | 4篇 |
外科学 | 1834篇 |
综合类 | 2496篇 |
现状与发展 | 1篇 |
一般理论 | 2篇 |
预防医学 | 2386篇 |
眼科学 | 437篇 |
药学 | 2436篇 |
38篇 | |
中国医学 | 1013篇 |
肿瘤学 | 976篇 |
出版年
2024年 | 81篇 |
2023年 | 386篇 |
2022年 | 672篇 |
2021年 | 1040篇 |
2020年 | 977篇 |
2019年 | 929篇 |
2018年 | 960篇 |
2017年 | 923篇 |
2016年 | 788篇 |
2015年 | 850篇 |
2014年 | 1519篇 |
2013年 | 1481篇 |
2012年 | 1259篇 |
2011年 | 1362篇 |
2010年 | 1160篇 |
2009年 | 979篇 |
2008年 | 948篇 |
2007年 | 955篇 |
2006年 | 903篇 |
2005年 | 684篇 |
2004年 | 622篇 |
2003年 | 541篇 |
2002年 | 487篇 |
2001年 | 323篇 |
2000年 | 296篇 |
1999年 | 295篇 |
1998年 | 225篇 |
1997年 | 203篇 |
1996年 | 190篇 |
1995年 | 177篇 |
1994年 | 184篇 |
1993年 | 134篇 |
1992年 | 140篇 |
1991年 | 140篇 |
1990年 | 144篇 |
1989年 | 133篇 |
1988年 | 122篇 |
1987年 | 99篇 |
1986年 | 95篇 |
1985年 | 120篇 |
1984年 | 113篇 |
1983年 | 99篇 |
1982年 | 84篇 |
1981年 | 95篇 |
1980年 | 77篇 |
1979年 | 48篇 |
1978年 | 34篇 |
1977年 | 31篇 |
1976年 | 34篇 |
1973年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The present study investigated the effects of lead stimulus modality on modification of the acoustic startle reflex during three reaction time tasks. In Experiment 1, participants (N = 48) were required to press a button at the offset of one stimulus (task relevant) and to ignore presentations of a second (task irrelevant). Two tones that differed in pitch or two lights served as signal stimuli. Blink startle was elicited during some of the stimuli and during interstimulus intervals. Skin conductance responses were larger during task-relevant stimuli in both groups. Larger blink facilitation during task-relevant stimuli was found only in the group presented with auditory stimuli, whereas larger blink latency shortening during task-relevant stimuli was found in both groups. Experiment 2 (N = 32) used only a task-relevant stimulus. Blink magnitude facilitation was significant only in the group presented with tones, whereas blink latency shortening was significant in both groups. Experiment 3 (N = 80) used a go/nogo task that required participants to press a button if one element of a compound stimulus ended before the second, but not if the asynchrony was reversed. The offset asynchrony was varied between groups as a manipulation of task difficulty. Startle magnitude facilitation was larger during acoustic than during visual stimuli and larger in the easy condition. The present data indicate that startle facilitation in a reaction time task is affected by stimulus modality and by task demands. The effects of the task demands seem to be independent of lead stimulus modality. 相似文献
992.
Evaluating the efficiency of specimen (sample) pooling for real-time PCR based diagnosis of COVID-19
《Indian journal of medical microbiology》2021,39(3):339-342
PurposeThis study is aims at evaluating the efficacy and sensitivity of specimen pooling for testing of SARS-CoV-2 virus to determine the accuracy, resource savings, and identification of borderline positive cases without impacting the accuracy of the testing.MethodThis study was conducted between August and October 2020, we performed COVID-19 testing by RT-PCR on the samples from varying prevalence of rural population (non-hot spot) referred to COVID laboratory, in the first step, the samples were collated into pools of 5 or 10. These pools were tested by RT-PCR. Negative pools were reported as negative whereas positive pools of 5 and 10 were then de-convoluted and each sample was tested individually.ResultsIn the present study, we tested 1580 samples in 158 pools of 10 and 17,515 samples in 3503 pools of 5. Among 10 samples pool, 11 (13%) pools flagged positive in the first step. In the second step, among 11 pools (110 samples) de-convoluted strategy was followed in which 10 individual samples came positive. Among 5 samples pool, 164 (13%) pools flagged positive in the first step. In the second step, among 164 pools (820 samples) de-convoluted strategy was followed in which 171 individual samples came positive. The pooled sample testing strategy saves substantial resources and time during surge testing and enhanced pandemic surveillance. This approach requires around 76%–93% fewer tests in low to moderate prevalence settings and group sizes up to 5–10 in a population, compared to individual testing.ConclusionPooled sample RT- PCR analysis strategies can save substantial resources and time for COVID-19 mass testing in comparison with individual testing without compromising the quality of outcome of the test. In particular, the pooled sample approach can facilitate mass screening in the early asymptomatic stages of COVID-19 infections. 相似文献
993.
Guillaume Millet Romuald Lepers Gregory Lattier Vincent Martin Nicolas Babault Nicola Maffiuletti 《European journal of applied physiology》2000,83(4-5):376-380
The aim of this study was to examine the effects of fatigue induced by a 65-km ultramarathon on the oxygen cost of running
(Cr) and cycling (Ccycl). The day before and immediately after the race, a group of nine well-trained male subjects performed two sub-maximal 4-min
exercise bouts: one cycling at a power corresponding to 1.5 W · kg−1 body mass on an electromagnetically braked ergometer, and one running at 11 km · h−1 on a flat asphalt roadway. Before oxygen cost determinations, the subjects performed 12 “ankle” jumps at a given frequency
that was fixed by an electronic metronome (2.5 Hz). From the non-fatigued to the fatigued condition, there was a significant
increase in minute ventilation for both running (P < 0.01) and cycling (P < 0.0001). Significant changes were also found in respiratory exchange ratio both for running (P=0.01) and cycling (P < 0.0001). However, running and cycling differed in that Ccycl increased significantly by [mean (SD)] 24.2 (11.5)% (P < 0.001), suggesting an alteration of muscle efficiency, while Cr did not change with fatigue [186.8 (14.1) mlO2 · kg−1 · km−1 vs 186.8 (18.7) mlO2 · kg−1 · km−1]. In addition, contact times during hopping increased significantly from 0.173 (0.019) ms to 0.194 (0.027) ms (P < 0.01). Analysis of the factors that determine Cr indicate that the subjects modified their movement pattern in order to decrease the mechanical cost of running in such long-term
fatigue conditions.
Accepted: 7 August 2000 相似文献
994.
Atrial automaticity and atrioventricular conduction in athletes: contribution of autonomic regulation 总被引:2,自引:0,他引:2
Stein R Moraes RS Cavalcanti AV Ferlin EL Zimerman LI Ribeiro JP 《European journal of applied physiology》2000,82(1-2):155-157
Little is known about the sinoatrial automatism and atrioventricular conduction of trained individuals who present a normal
resting electrocardiogram. We used transesophageal atrial stimulation, a minimally invasive technique, to evaluate aerobically
trained athletes (n=10) and sedentary individuals (n=10) with normal resting electrocardiograms, to test the hypothesis that parasympathetic tone, as detected by heart rate variability,
could be associated with changes in sinoatrial automatism and atrioventricular conduction. Corrected sinus node recovery time
tended to be longer in athletes than in sedentary individuals, but this difference did not reach statistical significance.
The Wenckebach point occurred at a lower rate in athletes than in the controls. Over a 24-h period of measurement, the mean
RR interval was longer in the athletes than in the sedentary individuals. The mean square root of successive differences (rMSSD)
tended to be higher in athletes than in controls, but this difference did not reach statistical significance. There was a
moderate correlation (r=0.48, P < 0.05) between the index of atrioventricular conduction, the rate at the Wenckebach point, and the logarithmically transformed
rMSSD. Thus, as a corollary to its effects on the sinus node, where increased parasympathetic tone, decreased sympathetic
tone, and non-autonomic components may contribute to sinus bradycardia, it is possible that athletic training may also induce
intrinsic adaptations in the conduction system, which could contribute to the higher prevalence of atrioventricular conduction
abnormalities observed in athletes.
Accepted: 2 January 2000 相似文献
995.
Night-time sleep and daytime sleepiness in narcolepsy 总被引:2,自引:0,他引:2
This report describes night-time sleep and daytime sleepiness in a large (N=530) sample of patients meeting the International Classification of Sleep Disorders criteria for diagnosis of narcolepsy. Sleep data were obtained from polysomnographic recordings on two consecutive nights. Sleepiness was assessed using the Multiple Sleep Latency Test, the Maintenance of Wakefulness Test and the Epworth Sleepiness Scale. Analysis revealed that sleep was mild to moderately disturbed on both recording nights. A first-night effect was suggested by decreased REM latency and increased percentage REM and slow-wave sleep on the second night. Sleepiness and sleep disturbance varied across patient subgroups created based on patient ethnicity and on the presence/absence of cataplexy, sleep apnoea, and periodic limb movements. Covariation of sleep and sleepiness measures across patients was significant but weak. Strong association was found between subgroup means of sleep and sleep disturbance measures. The findings reported here show that sleepiness and sleep disturbance vary across patient subgroups and that sleep disturbance is related to, although unable to account, for the pathological sleepiness of narcolepsy. 相似文献
996.
Hayat HaratiMonique Majchrzak Brigitte CosquerRodrigue Galani Christian KelcheJean-Christophe Cassel Alexandra Barbelivien 《Neurobiology of aging》2011,32(4):718-736
Aged rodents exhibit memory and attention dysfunctions. Environmental enrichment (EE) attenuates memory impairments. Whether it may reduce attention deficits is not known. At the age of 1 month, Long-Evans female rats were placed in standard or EE conditions and tested after 3 (young), 12 (middle-aged) or 24 (aged) months of differential housing. Spatial reference memory was assessed in a water-maze task. Attention performance was evaluated in the five-choice serial reaction time (5-CSRT) task. EE improved spatial memory at all ages, but did not ameliorate 5-CSRT performance in young and middle-aged rats; it prevented, however, the degradation of attention performances detected in aged rats. The number of ChAT (+30 to +64%)- and p75NTR-positive (+35 to +44%) neurons was higher in the basal forebrain of aged enriched vs. standard rats, suggesting their EE-mediated protection. The weaker deficit of attention found in aged EE rats might be linked to a better survival in the very long term of neurons in the basalo-cortical system. 相似文献
997.
Research has shown that during emotional imagery, valence and arousal each modulate the startle reflex. Here, two imagery-startle experiments required participants to attend to the startle probe as a simple reaction time cue. In Experiment 1, four emotional conditions differing in valence and arousal were examined. Experiment 2, to accentuate potential valence effects, included two negative high arousal, a positive high arousal and a negative low arousal condition. Imagery effectively manipulated emotional valence and arousal, as indicated by heart rate and subjective ratings. Compared to baseline, imagery facilitated startle responses. However, valence and arousal failed to significantly affect startle magnitude in both experiments and startle latency in Experiment 1. Results suggest that emotional startle modulation is eclipsed when the probe is significant for task completion and/or cues a motor response. Findings suggest that an active, rather than defensive, response set may interfere with affective startle modulation, warranting further investigation. 相似文献
998.
Kasztelewicz B Jankowska I Pawłowska J Teisseyre J Dzierżanowska-Fangrat K 《Journal of medical virology》2011,83(12):2182-2190
Immunosuppressed pediatric transplant recipients are at risk of developing Epstein–Barr virus (EBV)‐associated complications (such as post‐transplant lymphoproliferative disorders). Monitoring of the EBV DNA level in blood alone has a low predictive value for the post‐transplant course of EBV infection and its complications. Therefore, additional prognostic markers are widely sought. The study aim was to analyze EBV gene expression patterns and LMP1 polymorphism in relation to EBV DNA levels in pediatric liver transplant recipients. EBV load measurement, LMP1 variant, and gene expression analysis were performed in collected prospectively multiple blood samples from 30 patients. Several distinct patterns of EBV gene expression were identified: latency 2 (71%), latency 3 (13%), latency 0 (11%), and lytic infection (5%). In most children's multiple blood samples, both EBV gene expression patterns and expression levels of individual EBV genes varied significantly over time. EBV gene expression patterns were not associated with the EBV load. However, the viral load correlated with the LMP1 and LMP2 expression (r = 0.34; P = 0.006, and r = 0.45; P = 0.001, respectively). Two variants of the LMP1 gene were detected, and they were consistent over time in individual patients. A wild type of LMP1 was associated with higher EBV‐DNA loads (P = 0.03). This indicates that EBV infection in immunosuppressed patients is a very dynamic process, but changes in the state of EBV infection do not influence significantly the viral load. The latter, however, can be associated with the activity of LMP1 and LMP2 genes, as well as polymorphism of LMP1. J. Med. Virol. 83:2182–2190, 2011. © 2011 Wiley Periodicals, Inc. 相似文献
999.
外周血CD34+造血干细胞加适量T细胞输注进行HLA半相合的异体移植 总被引:3,自引:0,他引:3
对1例Ph+染色体的急淋患儿进行母子间HLA半相合的异体外周血造血干细胞移植 ,为避免由于HLA不相合所产生的由T细胞介导的严重移植物抗宿主病(GVHD) ,采用了CD34+细胞正性分离去除淋巴细胞 ;同时为避免由于T细胞过度去除而引起宿主抗移植物反应(HVG)导致植入失败 ,在移植次日又加入部分T细胞 ,使病儿接受CD34 +细胞6×106/kg 和CD3 +细胞1.05×107/kg。结果 :随访1年来 ,红系、粒系和巨核系均恢复正常 ,临床上仅出现一过性的IIOaGVHD以及轻微的局限于口唇粘膜的cGVHD。STR位点DNA检验以及染色体检查 :移植后 +180天受体已从供体型嵌合体转为完全供体型 ,病儿获得植入成功。结果表明 ,常规剂量的CD34 +细胞移植加以适量CD3 +T细胞 ,可克服HLA部分不相配的难点 ,减轻GVHD ,同时也可避免由于过度的T细胞去除而出现的HVG。 相似文献
1000.