全文获取类型
收费全文 | 1181篇 |
免费 | 124篇 |
国内免费 | 37篇 |
专业分类
耳鼻咽喉 | 44篇 |
儿科学 | 21篇 |
妇产科学 | 4篇 |
基础医学 | 167篇 |
口腔科学 | 5篇 |
临床医学 | 160篇 |
内科学 | 222篇 |
皮肤病学 | 2篇 |
神经病学 | 256篇 |
特种医学 | 43篇 |
外科学 | 38篇 |
综合类 | 128篇 |
预防医学 | 53篇 |
眼科学 | 138篇 |
药学 | 40篇 |
中国医学 | 13篇 |
肿瘤学 | 8篇 |
出版年
2024年 | 2篇 |
2023年 | 22篇 |
2022年 | 32篇 |
2021年 | 69篇 |
2020年 | 62篇 |
2019年 | 50篇 |
2018年 | 45篇 |
2017年 | 43篇 |
2016年 | 48篇 |
2015年 | 41篇 |
2014年 | 70篇 |
2013年 | 75篇 |
2012年 | 48篇 |
2011年 | 64篇 |
2010年 | 47篇 |
2009年 | 57篇 |
2008年 | 67篇 |
2007年 | 44篇 |
2006年 | 47篇 |
2005年 | 40篇 |
2004年 | 27篇 |
2003年 | 29篇 |
2002年 | 19篇 |
2001年 | 17篇 |
2000年 | 19篇 |
1999年 | 18篇 |
1998年 | 13篇 |
1997年 | 15篇 |
1996年 | 15篇 |
1995年 | 9篇 |
1994年 | 16篇 |
1993年 | 8篇 |
1992年 | 16篇 |
1991年 | 14篇 |
1990年 | 13篇 |
1989年 | 10篇 |
1988年 | 16篇 |
1987年 | 5篇 |
1986年 | 9篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1972年 | 3篇 |
排序方式: 共有1342条查询结果,搜索用时 31 毫秒
1.
《Clinical neurophysiology》2021,132(9):2003-2011
ObjectiveA large N20 and P25 of the median nerve somatosensory evoked potential (SEP) predicts short survival in amyotrophic lateral sclerosis (ALS). We investigated whether high frequency oscillations (HFOs) over N20 are enlarged and associated with survival in ALS.MethodsA total of 145 patients with ALS and 57 healthy subjects were studied. We recorded the median nerve SEP and measured the onset-to-peak amplitude of N20 (N20o-p), and peak-to-peak amplitude between N20 and P25 (N20p-P25p). We obtained early and late HFO potentials by filtering SEP between 500 and 1 kHz, and measured the peak-to-peak amplitude. We followed up patients until endpoints (death or tracheostomy) and analyzed the relationship between SEP or HFO amplitudes and survival using a Cox analysis.ResultsPatients showed larger N20o-p, N20p-P25p, and early and late HFO amplitudes than the control values. N20p-P25p was associated with survival periods (p = 0.0004), while early and late HFO amplitudes showed no significant association with survival (p = 0.4307, and p = 0.6858, respectively).ConclusionsThe HFO amplitude in ALS is increased, but does not predict survival.SignificanceThe enlarged HFOs in ALS might be a compensatory phenomenon to the hyperexcitability of the sensory cortex pyramidal neurons. 相似文献
2.
《Ophthalmology》2020,127(11):1498-1506
3.
《Sleep medicine》2021
BackgroundIdentifying electroencephalogram (EEG) cortical arousals are crucial in scoring hypopneas and respiratory efforts related arousals (RERAs) during a polysomnogram. As children have high arousal threshold, many of the flow limited breaths or hypopneas may not be associated with visual EEG arousals, hence this may lead to potential underestimation of the degree of sleep disordered breathing. Pulse wave amplitude (PWA) is a signal obtained from finger photoplethysmography which correlates directly to finger blood flow. The drop in PWA has been shown to be a sensitive marker for subcortical/autonomic and cortical arousals. Our aim was to use the drop in PWA as a surrogate for arousals to guide scoring of respiratory events in pediatric patients.MethodsTen polysomnograms for patients between the ages of 5–15 years who had obstructive apnea-hypopnea indices between 1 and 5 events/hour were identified. Patients with syndromes were excluded. A drop in PWA signal of at least 30% that lasted for 3 s was needed to identify subcortical/autonomic arousals. Arousals were rescored based on this criteria and subsequently respiratory events were rescored. Paired t-tests were employed to compare PSG indices scored with or without PWA incorporation.ResultsThe sample of 10 children included 2 females, and the average age was 9.8 ± 3.1 years. Overall, polysomnography revealed an average total sleep time of 464.1 ± 25 min, sleep efficiency of 92% +/−4.2, sleep latency of 19.6 ± 17.0 min, rapid eye movement (REM) latency 143 ± 66 min, N1 3.9% +/−2.0, N2 50.3% +/−12.0, N3 28.2% +/−9.1, REM 16.7% +/−4.0, and wakefulness after sleep onset (WASO) 18.1 ± 7.5 min. Including arousals from PWA changes, respiratory indices significantly increased including total AHI (2.3 ± 0.7 vs 5.7 ± 2.1, p < 0.001), obstructive AHI (1.45 ± 0.7 vs 4.8 ± 1.8, p < 0.001), and RDI (2.36 ± 0.7 vs 7.6 ± 2.0, p < 0.001). Likewise, total arousal index was significantly higher (8.7 ± 2.3 vs 29.4 ± 6.5, p < 0.001).ConclusionsThe drop in pulse wave amplitude signal is a useful marker to guide scoring arousals that are not otherwise easily identified in pediatric polysomnography and subsequently helped in scoring respiratory events that otherwise would not be scored. Further studies are needed to delineate if such methodology would affect clinical outcome. 相似文献
4.
根据微动滑移振幅具有小位移的特点,设计制作了一种弓形传感装置,该装置能把小幅位移信号转换为电信号,并通过示波器实时显示出来,用这种测试装置来测量滑移式微动振幅具有测试方法简单而测试精度较高的优点。 相似文献
5.
Kim C. Donaghue M.M. Pena A.T.W. Fung M. Bonney N.J. Howard M. Silink J. Schwingshandl 《Diabetic medicine》1995,12(10):868-873
The study aimed to compare the longitudinal assessment of autonomic nerve function by computerized infrared pupillometry and standard cardiovascular tests in adolescents with diabetes. Adolescents (n = 150) were assessed at two time points (T1 and T2). The median time interval between assessments was 1.5 (range 0.9–3) years. At T1 the median age was 14.5 (range 8.3–19.5) years and the median duration was 6.5 (range 1.1–16) years. The pupillary variables assessed included the resting pupil diameter, the maximum constriction velocity, and the reflex amplitude of constriction. Heart rate reflexes were assessed in response to deep breathing, the Valsalva manoeuvre, and on standing from a lying position (30/15 ratio). Between visits there was a significant decrease in maximum constriction velocity (6.0 mm s?1 vs 6.3 mm s?1, p = 0.0001) and resting pupil diameter (6.2 mm vs 6.3 mm, p = 0.001). At reassessment pupillary abnormalities increased from 32 (21 %) to 45 (30%), with 17 (54 %) of the initial abnormalities persisting. Adolescents with abnormally slow maximum constriction velocity compared to those with normal maximum constriction velocity had a higher glycated haemoglobin (HbA1c%) at T2 (p = 0.02) and between assessments (p = 0.01). Cardiovascular test abnormalities did not increase between visits and the persistence of initial abnormalities was low (21 %). In summary, pupillometry appears a more sensitive test of autonomic nerve dysfunction in adolescents with diabetes than assessment of cardiovascular reflexes. 相似文献
6.
Karen Holopigian Jeremy Snow William Seiple Irwin Siegel 《Documenta ophthalmologica. Advances in ophthalmology》1988,70(1):103-115
Conflicting results have been obtained concerning the parametric properties of the pattern electroretinogram. These discrepancies may be due to the large amount of variability inherent in recording amplitudes. We have found the variability within a single stimulus condition to be so large (ranging from 30% to 67% of the mean value) that it could mask any underlying spatial frequency tuning. Changing the stimulus conditions failed to significantly reduce the observed variability, although changing recording conditions produced some reduction. The use of a narrower rejection band, a greater number of sweeps, and placement of the reference electrode on the ipsilateral ear (as opposed to the ipsilateral temple) combined to decrease variability of the pattern electroretinogram within a single recording session; however, intersession variability remained high. Therefore one must be careful in evaluating data from this technique, and caution is advised in its clinical use. 相似文献
7.
目的:探讨糖尿病周围神经病(DPN)患者的临床特征与神经电生理变化。方法:分析97例DPN患者的临床特征,比较DPN组和对照组的神经传导速度(NCV)、远端潜伏期、远端波幅3个参数。结果:①临床特征以肢体麻木(59%)最多见、其次为疼痛(42%)。②患者组NCV、远端波幅值低于对照组,远端潜伏期比对照组延长;两组3个参数比较,除腓总神经远端波幅、尺神经感觉传导速度和正中、尺、腓肠神经远端潜伏期外,差异均有统计学意义(P<0.05)。结论:①DPN患者临床特征以肢体麻木和疼痛最多见;②检测NCV、远端潜伏期、远端波幅,能较早发现临床患者。 相似文献
8.
Twenty-one subjects look the Autonomic Perception Questionnaire (APQ) and later were given another test of ability to perceive heart activity. The second test involved subjects' tracking of their own heart rates (HR). They were then tested for ability to increase and decrease HR from their resting baseline levels. No significant relationships were found between HR control and APQ score. HR decrease success seemed to depend mainly on respiration differences between rest and decrease periods. The subjects who achieved high scores on the heart tracking test increased HR significantly better than did low scorers. This heart perception vs HR increase relationship did not depend upon respiration rate, respiration amplitude, or baseline HR differences between high and low scorers on the tracking test. A low correlation between APQ and tracking score seemed to indicate that the two perception tests measured different attributes of the subjects. 相似文献
9.
Fallgatter AJ Esienack SS Neuhauser B Aranda D Scheuerpflug P Herrmann MJ 《Brain topography》2000,12(4):255-261
The P300-amplitude evoked with an acoustic oddball-paradigm is considered the most stable late event-related potential (ERP). This amplitude-index has become a standard parameter in electrophysiology. Recently, a robust ERP-parameter (NoGo-anteriorization, NGA) has been introduced, which reflects spatial brain electrical changes in relation to execution and inhibition of a motor response elicited with a Continuous Performance Test (CPT). The current study refers to the stability of this new topographical ERP-parameter compared to the stability of the classical P300-amplitude. For that purpose, 12 healthy subjects were investigated with both paradigms during recording of a 21-channel EEG. Analysis of the resulting ERPs revealed a very high stability for both, topographical and amplitude index: In every single subject, the brain electrical fields were characterized by a more anterior location in the NoGo- compared to the Go-condition (=NGA) and by higher amplitudes after target compared to distractor condition. T-tests, analyses of the effect size and of the power revealed equivalent differences between the two contrasting conditions for the topographical compared to the amplitude index. These results indicate that the stability of the topographical ERP-parameters elicited with the CPT is sufficient for an electrophysiological standard-index. The possibility to elicit a robust and specific spatial brain activation with the CPT is an ideal completion to the classical P300 amplitude effect and, therefore, hopefully will be a useful expansion of the standard paradigms in electrophysiological laboratories. 相似文献
10.
Ujiie T 《Computers in biology and medicine》2003,33(3):227-237
Partial left ventriculectomy (PLV) was originally introduced as a new surgical approach by patients with an end stage of cardiac disease. Coronary artery bypass grafting (CABG) is a standard procedures used in cardiac surgery. Multichannel ECG (MECG) measurements and body surface mapping (BSM) were used to analyse the normalised beat amplitude power maps (BAM) that reflect an overall cardiac activity. The resulting BAMs show that the amplitude of cardiac signals decrease for approximately 30% after the PLV and stay in the same level during the postoperative monitoring interval while after CABG no significant changes in BAM have been observed. In addition the electrodes from the body surface area above the left ventricle, where surgery was performed, show significant changes in beat amplitudes. 相似文献