全文获取类型
收费全文 | 513篇 |
免费 | 59篇 |
国内免费 | 5篇 |
专业分类
耳鼻咽喉 | 10篇 |
儿科学 | 48篇 |
妇产科学 | 6篇 |
基础医学 | 61篇 |
口腔科学 | 27篇 |
临床医学 | 61篇 |
内科学 | 103篇 |
皮肤病学 | 19篇 |
神经病学 | 57篇 |
特种医学 | 80篇 |
外科学 | 36篇 |
综合类 | 17篇 |
预防医学 | 8篇 |
眼科学 | 2篇 |
药学 | 29篇 |
肿瘤学 | 13篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 10篇 |
2018年 | 7篇 |
2017年 | 5篇 |
2016年 | 9篇 |
2015年 | 12篇 |
2014年 | 15篇 |
2013年 | 20篇 |
2012年 | 13篇 |
2011年 | 13篇 |
2010年 | 39篇 |
2009年 | 27篇 |
2008年 | 17篇 |
2007年 | 14篇 |
2006年 | 17篇 |
2005年 | 21篇 |
2004年 | 12篇 |
2003年 | 13篇 |
2002年 | 11篇 |
2001年 | 4篇 |
2000年 | 7篇 |
1999年 | 10篇 |
1998年 | 31篇 |
1997年 | 35篇 |
1996年 | 34篇 |
1995年 | 27篇 |
1994年 | 18篇 |
1993年 | 18篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 12篇 |
1988年 | 13篇 |
1987年 | 16篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 10篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1954年 | 1篇 |
排序方式: 共有577条查询结果,搜索用时 15 毫秒
31.
KP Morris JR Skinner C Wren S Hunter MG Coulthard 《Archives of disease in childhood》1993,68(5):637-643
Thirteen anaemic children on dialysis were assessed to determine the incidence of cardiac changes in end stage renal failure. Nine children had an increased cardiothoracic ratio on radiography. The electrocardiogram was abnormal in every case but no child had left ventricular hypertrophy as assessed by voltage criteria. However, left ventricular hypertrophy, often gross, was found on echocardiography in 12 children and affected the interventricular septum disproportionately. Cardiac index was increased in 10 patients as a result of an increased left ventricular stroke volume rather than heart rate. Left ventricular hypertrophy was significantly greater in those on treatment for hypertension and in those with the highest cardiac index. Abnormal diastolic ventricular function was found in 6/11 children. Children with end stage renal failure have significant cardiac abnormalities that are likely to contribute to the high cardiovascular mortality in this group. Anaemia and hypertension, or its treatment, probably contribute to these changes. Voltage criteria on electrocardiogram are of no value in detecting left ventricular hypertrophy. Echocardiography must be performed, with the results corrected for age and surface area, in order to detect and follow these abnormalities. 相似文献
32.
33.
Between June 1986 and April 1988, 86 sonographic examinations of the shoulder were performed on patients suspected of having rotator cuff tears. Major sonographic diagnostic criteria included (a) a well-defined discontinuity usually visible as a hypoechoic focus within the cuff, (b) nonvisualization of the cuff and (c) an echogenic focus within the cuff. Seventy-five patients underwent both sonography and arthrography. Compared with arthrography alone, ultrasound examinations enabled detection of 92% of rotator cuff tears (24 of 26 tears), with a specificity of 84% and a negative predictive value of 95%. Correlation was obtained in 30 of these patients who underwent surgery for rotator cuff tear or other soft-tissue abnormality. In this group, the sensitivity of sonography for detection of a tear was 93%, with a specificity of 73%, while for arthrography sensitivity was 87% and specificity was 100%. These data indicate that sonography is a useful, noninvasive screening procedure for patients suspected of having rotator cuff injury. 相似文献
34.
Computed tomography of the pancreas 总被引:2,自引:0,他引:2
35.
Background
Chronic lymphocytic leukemia (CLL) is a monoclonal disorder, characterized by a progressive proliferation of functionally incompetent B lymphocytes. There is increased evidence of association between CLL and skin cancers, including the uncommon Merkel cell carcinoma (MCC). 相似文献36.
Data from brain-damaged and neurologically intact populations indicate hemispheric asymmetries in the temporo-parietal cortex for discriminating an object's global form (e.g. the overall shape of a bicycle) versus its local parts (e.g. the spokes in a bicycle tire). However, it is not yet clear whether such asymmetries reflect processes that (i) bias attention toward upcoming global versus local stimuli and/or (ii) attend/identify global versus local stimuli after they are presented. To investigate these possibilities, we asked sixteen healthy participants to perform a cued global/local attention task while their brain activity was recorded using event-related functional magnetic resonance imaging (fMRI). The results indicated a novel double dissociation. Hemispheric asymmetries for deploying attention toward expected global versus local object features were specific to the intraparietal sulcus (iPs). However, hemispheric asymmetries for identifying global versus local features after they were presented were specific to the inferior parietal lobe/superior temporal gyrus (IPL/STG). This double dissociation provides the first direct evidence that hemispheric asymmetries associated with different components of global/local attention occur in distinct temporo-parietal loci. Furthermore, it parallels an analogous dissociation reported in a recent fMRI study of spatial orienting, suggesting that global/local attention and spatial attention might rely on similar cognitive/neural mechanisms. 相似文献
37.
Various models of selective attention propose that greater attention is allocated toward target stimuli when conflicting distracters make selection more difficult, but compelling evidence to support this view is scarce. In the present experiment, 15 participants performed a cued global/local selective attention task while brain activity was recorded with event-related functional magnetic resonance imaging. The presence of conflicting versus nonconflicting distracters during target processing activated regions of frontal, parietal, and visual cortices that were also activated when participants oriented attention in response to global- and local-task cues. These findings support models in which conflict between target and distracter stimuli is resolved by more selectively focusing attention upon target stimuli. 相似文献
38.
A major difficulty in fast-rate event-related fMRI experiments is the extensive overlap from adjacent trials in the stimulus sequence. One approach to address this problem is to include "no-stim" or "null" events as a trial type. These are randomized as if they were true stimulus events but no stimulus actually occurs. Assuming that no response is elicited by the null events, their time-locked average reflects only the averaged overlap. Thus, contrasting the averages for the other trial types versus the null-event average subtracts out the overlap, enabling the extraction of the response functions for these other trial types. ERP studies, however, have indicated that an endogenous brain response, the omitted stimulus response (OSR), can be evoked by a missing event in a stream of regularly occurring stimuli. To the extent that this response is elicited by null events in an event-related fMRI experiment, the null-event subtraction or contrast would falsely introduce the inverse of the OSR into the averaged responses to the other trial types. Using high-density ERP recordings, we investigated the effect of different percentages of omitted stimuli (11, 22, and 33%) on the auditory OSR at stimulus rates of one event per second or one event per 2 s. Significant OSRs were found for each percentage in the 1-s condition as well as in the 11% 2-s condition. The responses consisted of an early posterior negative wave (180-280 ms) followed by a larger anterior positive wave. These results have important implications for fast-rate fMRI designs, while also providing new data on the brain's response to omitted stimuli. 相似文献
39.
MG Magaji JA Anuka I Abdu-Aguye AH Yaro I M Hussaini 《African journal of traditional, complementary, and alternative medicines》2008,5(2):147-153
Securinega virosa is used traditionally as sedative in children and in mental illnesses. In this study, the behavioral effects of methanolic root bark extract of S. virosa were investigated in mice. The results revealed that the extract significantly (P<0.05) and dose-dependently reduced the onset and prolonged the duration of sleep. The extract significantly (P<0.05) decreased exploratory activity and reduced the rate of apomorphine-induced stereotyped climbing at the doses tested (6.25–25mg/kg). It also produced a significant and dose-dependent motor coordination deficit in mice at the doses tested (P<0.01). The intraperitoneal median lethal dose in mice was 774.6mg/kg while the preliminary phytochemical screening revealed the presence of alkaloids, tannins, saponins and flavonoids. These results suggest that methanolic root bark extract of S. virosa contains biologically active principles that are sedative in nature and lend pharmacological credence to the ethnomedical use of the plant. 相似文献
40.
Chest computed tomography (CT), including high-resolution CT with thin (1.5-mm) sections was used to evaluate proved (pathologically or clinically) lymphangitic spread (LS) of tumor in 12 patients. These appearances were compared with thin-section scans obtained in 11 healthy subjects. Thin-section CT demonstrated findings consistent with thickening of the normal lung interstitium. In all patients, thin sections showed an increase in the number of peripheral lines (1-2 cm in length) that were diffuse in generalized disease and localized in focal disease. Normal peripheral arcades were not increased in number, but the limbs forming the arcades were thickened in all patients. A diffuse increase in linear and curvilinear structures (reticular pattern) was seen toward the center of the lung. Polygonal structures 1-2 cm in diameter were seen in seven patients with LS but not in healthy subjects. Fissures were thickened in nine patients. Selected 1.5-mm-thick CT sections are recommended through abnormal areas (seen at CT or on chest radiographs) or if these are normal at three levels (midapex, hilus, and 3 cm above the diaphragm) when scanning patients with tumors known to cause LS. 相似文献