全文获取类型
收费全文 | 10299篇 |
免费 | 528篇 |
国内免费 | 229篇 |
专业分类
耳鼻咽喉 | 134篇 |
儿科学 | 219篇 |
妇产科学 | 240篇 |
基础医学 | 1694篇 |
口腔科学 | 936篇 |
临床医学 | 1100篇 |
内科学 | 855篇 |
皮肤病学 | 40篇 |
神经病学 | 2050篇 |
特种医学 | 339篇 |
外科学 | 707篇 |
综合类 | 1031篇 |
预防医学 | 445篇 |
眼科学 | 197篇 |
药学 | 596篇 |
4篇 | |
中国医学 | 301篇 |
肿瘤学 | 168篇 |
出版年
2024年 | 21篇 |
2023年 | 137篇 |
2022年 | 314篇 |
2021年 | 469篇 |
2020年 | 347篇 |
2019年 | 325篇 |
2018年 | 338篇 |
2017年 | 305篇 |
2016年 | 325篇 |
2015年 | 332篇 |
2014年 | 588篇 |
2013年 | 682篇 |
2012年 | 511篇 |
2011年 | 578篇 |
2010年 | 458篇 |
2009年 | 496篇 |
2008年 | 523篇 |
2007年 | 465篇 |
2006年 | 437篇 |
2005年 | 347篇 |
2004年 | 322篇 |
2003年 | 263篇 |
2002年 | 226篇 |
2001年 | 183篇 |
2000年 | 177篇 |
1999年 | 157篇 |
1998年 | 156篇 |
1997年 | 122篇 |
1996年 | 107篇 |
1995年 | 96篇 |
1994年 | 82篇 |
1993年 | 60篇 |
1992年 | 66篇 |
1991年 | 75篇 |
1990年 | 73篇 |
1989年 | 63篇 |
1988年 | 58篇 |
1987年 | 64篇 |
1986年 | 57篇 |
1985年 | 88篇 |
1984年 | 85篇 |
1983年 | 64篇 |
1982年 | 62篇 |
1981年 | 51篇 |
1980年 | 66篇 |
1979年 | 37篇 |
1978年 | 32篇 |
1977年 | 23篇 |
1976年 | 29篇 |
1974年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
The changes of spatial EEG synchronisation during brisk and slow voluntary self-paced movements of the right and left index finger were analysed in 12 right-handed and 11 left-handed subjects. EEG was recorded from the left and right sensorimotor area using 24 closely spaced electrodes. A novel measure of spatial EEG synchronisation, -complexity, was computed separately for the left and right sensorimotor area in 64 overlapping one-second epochs representing 4.5 s of the pre-movement and 3.5 s of the post-movement period. -complexity was higher, hence spatial synchronisation was lower, in slow than in brisk movements, especially in the right-handed. A sustained increase of -complexity was observed during execution of a slow movement. A decrease of -complexity which was often associated with a brief burst of spatially synchronised 10-Hz oscillations occurred at the onset of extensor muscle contraction. We suggest that increased spatial EEG synchronisation at movement onset may prevent spillover of excitation from the sensorimotor hand area to other cortical regions. During movement, the cortical neuronal assemblies subserve distinct, specialised functions manifesting in increased -complexity. 相似文献
52.
Alessandro Daniotti Gaetano Povolo Agata Barchitta Aierken Abudureheman Paolo Cardaioli Cristina Basso 《Cardiovascular pathology》2004,13(6):330-333
A 51-year-old woman suffered rapidly irreversible cardiogenic shock with left hemiparesis. Transesophageal echocardiography, which represents an essential imaging tool in the emergency room, ruled out aortic dissection involving branch vessels but did not allow an in vivo diagnosis of spontaneous coronary dissection. The in vivo diagnosis of spontaneous coronary dissection is rather difficult because of the dramatic clinical presentation and selective coronary angiography requirement. 相似文献
53.
Bexander CS Mellor R Hodges PW 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2005,167(3):422-432
Control of the neck muscles is coordinated with the sensory organs of vision, hearing and balance. For instance, activity
of splenius capitis (SC) is modified with gaze shift. This interaction between eye movement and neck muscle activity is likely
to influence the control of neck movement. The aim of this study was to investigate the effect of eye position on neck muscle
activity during cervical rotation. In eleven subjects we recorded electromyographic activity (EMG) of muscles that rotate
the neck to the right [right obliquus capitis inferior (OI), multifides (MF), and SC, and left sternocleidomastoid (SCM)]
with intramuscular or surface electrodes. In sitting, subjects rotated the neck in each direction to specific points in range
that were held statically with gaze either fixed to a guide (at three different positions) that moved with the head to maintain
a constant intra-orbit eye position or to a panel in front of the subject. Although right SC and left SCM EMG increased with
rotation to the right, contrary to anatomical texts, OI EMG increased with both directions and MF EMG did not change from
the activity recorded at rest. During neck rotation SCM and MF EMG was less when the eyes were maintained with a constant
intra-orbit position that was opposite to the direction of rotation compared to trials in which the eyes were maintained in
the same direction as the head movement. The inter-relationship between eye position and neck muscle activity may affect the
control of neck posture and movement. 相似文献
54.
A wireless recording system was developed to study the electroencephalogram (EEG) in unrestrained, male Landrace piglets. Under general anesthesia, ball-tipped silver/silver chloride electrodes for EEG recording were implanted onto the dura matter of the parietal and frontal cortex of the piglets. A pair of miniature preamplifiers and transmitters was then mounted on the surface of the skull. To examine whether other bioelectrical activities interfere with the EEG measurements, an electrocardiogram (ECG) or electromyogram (EMG) of the neck was simultaneously recorded with the EEG. Next, wire electrodes for recording movement of the eyelid were implanted with EEG electrodes, and EEG and eyelid movements were simultaneously measured. Power spectral analysis using a Fast Fourier Transformation (FFT) algorithm indicates that EEG was successfully recorded in unrestrained piglets, at rest, during the daytime in the absence of interference from ECG, EMG or eyelid movements. These data indicate the feasibility of using our radiotelemetry system for measurement of EEG under these conditions. 相似文献
55.
The third derivative of motion or the change in the rate of acceleration (also known as jerk) is examined in terms of its applicability to the study of psychophysiological function. An algorithm of this third derivative is presented to show that jerk can be derived from the arithmetic difference of two slopes which constitute the portion of motion being differentiated. By modifying the algorithm, a new parameter termed “proportional jerk’ or PJ is formulated whereby one slope is measured relative to the other slope; this PJ provides information about the smoothness of movement without being influenced by the velocity as is the traditional jerk measure. A practical application of the PJ to waking saccades and REMs in 11 human subjects revealed that REMs are significantly “jerkier’ or less smooth than waking calibration eye movements. Whereas the waking eye movements had a well-defined negative phase of the PJ, the REMs did not show such stereotypical behavior. This is in accord with previous work which showed that waking saccade velocity increases to a maximum and then decreases whereas REMs maintain their peak or near peak velocities for varying periods. It was suggested that PJ can be useful in detecting subtle temporal changes in the course of movements and may be used as a parameter of motion even when the absolute amplitude is unknown. 相似文献
56.
The effects of environmental constraints upon licking patterns 总被引:1,自引:0,他引:1
Rats licked water under three degrees of environmental constraint. As restriction decreased, lick duration increased. Interlick interval changed independently of duration. Lickometer-measured drinking tube contact was longer than fluid contact unless access was highly restricted. The use of controlled access to measure minimal necessary taste input is discussed. 相似文献
57.
Kun?Guo Robert?G.?RobertsonEmail author Sasan?Mahmoodi Yoav?Tadmor Malcolm?P.?Young 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2003,150(3):363-374
Face perception plays a crucial role in primate social communication. We have investigated the pattern of eye movements produced
by rhesus monkeys (Macaca mulatta) as they viewed images of faces. Eye positions were recorded accurately using implanted eye coils, while neutral upright,
inverted and scrambled images of monkey and human faces were presented on a computer screen. The monkeys exhibited a similar
eye scan pattern while viewing familiar and unfamiliar monkey face images, or while viewing monkey and human face images.
No differences were observed in the distribution of viewing times, number of fixations, time into the trial of first saccade
to local facial features, and the temporal and spatial characteristics of viewing patterns across the facial images. However,
there was a greater probability of re-fixation of the eye region of unfamiliar faces during the first few seconds of the trial
suggesting that the eyes are important for the initial encoding of identity. Indeed, the highest fixation density was found
in the eye region of all the face images. The viewing duration and the number of fixations per image decreased when inverted
or scrambled faces were presented. The eye region in these modified images remained the primary area of fixation. However,
the number of fixations directed to the eyes decreased monotonically from the upright images through the inverted versions
to the scrambled face images. Nonetheless, the eyes remain the most salient facial substructure regardless of the arrangement
of other features, although the extent of salience which they attain may depend both on the low level properties of the eyes
and on the global arrangement of facial features.
Electronic Publication 相似文献
58.
目的探讨不孕不育及自发流产与染色体核型异常的关系,指导临床对这些疾病的诊断。方法采集922例生殖异常患者外周静脉血,进行淋巴细胞培养,常规方法收获细胞,低渗、固定、制片、经G显带处理、镜检,进行观察研究。结果922例患者共检出异常核型66例,总检出率7.16%。其中,易位21例,倒位21例,克氏综合征18例,X-三体综合征2例,Turner综合征伴X染色体缺失1例,Y染色体缺失1例,环状21号染色体1例,额外标记染色体1例,及常见染色体多态性大Y染色体63例,发生率13.35%。结论染色体异常是导致不孕不育及自发流产的重要原因之一,对生殖异常患者进行染色体检查可为临床诊断和优生优育提供依据。 相似文献
59.
D P Kimble 《Physiology & behavior》1978,21(2):177-187
Male Sprague-Dawley rats with combined lesions to the dorsal and lateral aspects of the entorhinal cortex in one hemisphere and of the contralateral dorsolateral hippocampal formation were compared with both operated and unoperated controls on three different behaviors, monitored across a 53 day postoperative period. The rats with the combined entorhinal cortex-hippocampal lesions (EH) showed transient hyperactivity in the open field, transient reduction in spontaneous alternation levels in an unbaited T-maze and persistent deficits in learning spatial maze problems. The results of the present experiment are discussed in comparison with those from experiments on rats with bilateral hippocampal lesions and those from experiments on rats with bilateral entorhinal cortex lesions. Although some similarities among these findings suggest that these two brain regions probably function in a coordinated fashion with respect to these behaviors, differences in the various syndromes are also discussed. 相似文献
60.
204对自然流产夫妇染色体核型分析 总被引:1,自引:1,他引:1
目的 分析自然流产与染色体异常核型之间的关系.方法 采用人外周血淋巴细胞培养,常规G显带技术行染色体核型检查,后结合临床资料对其进行分析.结果 204对自然流产夫妇中,检出染色体异常16例(平衡易位15例,罗伯逊易位1例),检出率3.82%,较一般人群的染色体异常率为高,差异有显著性(P<0.01);检出染色体多态性39例,检出率9.56%;流产例次染色体异常组(2.94±0.85)及多态性组(2.76±1.45)均较正常染色体组(1.05±1.39)为高,差异皆有显著性(P<0.01).结论 人体夫妇染色体异常是流产的重要原因之一,但染色体多态性方面的因素也不可忽视.对自然流产夫妇进行常规的染色体检查及遗传咨询具有一定的临床意义. 相似文献