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Ross BD; Jacobson S; Villamil F; Korula J; Kreis R; Ernst T; Shonk T; Moats RA 《Radiology》1994,193(2):457
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C. E. Kim G. K. Thaker D. E. Ross D. Medoff 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1997,113(2):371-377
The overall goals of the studies presented here were to compare (1) the accuracies of saccades to moving targets with either
a novel or a known target motion, and (2) the relationships between the measures of target motion and saccadic amplitude during
pursuit initiation and maintenance. Since resampling of position error just prior to saccade initiation can confound the interpretation
of results, the target ramp was masked during the planning and execution of the saccade. The results suggest that saccades
to moving targets were significantly more accurate if the target motion was known from the early part of the trial (e.g.,
during pursuit maintenance) than in the case of novel target motion (e.g., during pursuit initiation); both these types of
saccades were more accuate than those when target motion information was not available. Using target velocity in space as
a rough estimate of the magnitude of the extra-retinal signal during pursuit maintenance, the saccadic amplitude was significantly
associated with the extra-retinal target motion information after accounting for the position error. In most subjects, this
association was stronger than the one between retinal slip velocity and saccadic amplitude during pursuit initiation. The
results were similar even when the smooth eye motion prior to the saccade was controlled. These results suggest that different
sources of target motion information (retinal image velocity vs internal representation of previous target motion in space)
are used in planning saccades during different stages of pursuit. The association between retinal slip velocity and saccadic
amplitude is weak during initiation, thus explaining poor saccadic accuracy during this stage of pursuit. 相似文献
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Holcomb HH Lahti AC Medoff DR Weiler M Dannals RF Tamminga CA 《The American journal of psychiatry》2000,157(10):1634-1645
OBJECTIVE: The biological characteristics of schizophrenia are often studied by using functional imaging techniques. However, since volunteers with schizophrenia routinely fail to perform as accurately or as quickly as healthy volunteers, it is difficult to ascertain whether a particular deficit in blood flow to a brain region is due to behavior or to the underlying illness. In this report, investigators used an auditory recognition task to assess brain blood flow patterns and behavioral correlates of schizophrenic patient volunteers trained on the task. METHOD: Twelve healthy volunteers and 18 volunteers with schizophrenia were trained to make tone frequency recognitions. Accuracy and stimuli were matched between groups. Participants were required to press a button to indicate whether a briefly presented tone was the high-frequency (1500 Hz) reference tone or one of a lower frequency level (level chosen to elicit an 80% accuracy score). Subjects underwent bolus [(15)O]H(2)O blood flow positron emission tomography during inactive rest, a sensory motor control condition, and the decision task. Blood flow patterns were assessed between conditions and between groups. RESULTS: As a group, the patients with schizophrenia (who performed as quickly and accurately as the comparison subjects) exhibited significantly less change in regional cerebral blood flow (rCBF) to the anterior cingulate and supplementary motor cortices when switching from the sensory motor control to the decision condition. There were also marked between-group differences in correlations between rCBF and response time. Whereas the comparison subjects exhibited progressively greater blood flow to the frontal cortex in association with longer response times, the schizophrenic patients exhibited progressively lower blood flow in conjunction with extended response times. CONCLUSIONS: The failure to appropriately enhance cingulate activity when engaged in a demanding task and the progressive, time-dependent decline in frontal blood flow suggest that patients with schizophrenia are unable to make optimal use of frontocingulate systems when maximally engaged in high-error tasks. 相似文献
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BD White A Kong E Khoo AM Southcott 《Journal of Medical Imaging and Radiation Oncology》2005,49(4):319-321
Tracheobronchopathia osteochondroplastica (TO) is a rare benign disease characterized by the presence of osseous and cartilaginous submucosal nodules projecting into the tracheobronchial tree. Most cases are asymptomatic and discovered incidentally at post‐mortem. We identified a case of TO on thoracic spiral CT and confirmed the diagnosis on bronchoscopy. This article reviews the imaging characteristics of TO, and shows the 3‐D virtual bronchoscopic and multiplanar reconstruction appearances of TO. 相似文献
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WBG Macdonald AP Patrikeos RI Thompson BD Adler AA Van Der Schaaf 《Journal of Medical Imaging and Radiation Oncology》2005,49(1):32-38
The present study compared the accuracy of ventilation perfusion scintigraphy (VQS) and CT pulmonary angiography (CTPA) for the diagnosis of pulmonary embolism. This was a prospective observational study of 112 patients with suspected pulmonary embolism (PE) who could be studied with both investigations within 24 h. Results were compared to final diagnosis at completion of 6-month follow up, using receiver operating characteristic (ROC) analysis. Pulmonary embolism was diagnosed in 27 referred patients (24%). The sensitivity and specificity of VQS and CTPA were similar to that reported from the literature. A normal VQ scan had the highest negative predictive value (100%), while a high-probability VQ scan had the highest positive predictive value (92%). There was no overall difference (area under the ROC curve (AUC)) between VQS (AUC (95% CI) = 0.82 (0.75,0.89)) and CTPA (AUC = 0.88 (0.81,0.94)) for the diagnosis of PE. Among patients with abnormal chest X-rays, CTPA (AUC 0.90 (0.83,0.97)) appeared somewhat better than VQS (AUC 0.78 (0.68,0.88)) but this difference did not reach statistical significance. In this instance, CTPA is at least as accurate as VQS and may provide an opportunity to make alternative diagnoses. 相似文献
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