全文获取类型
收费全文 | 3150104篇 |
免费 | 270714篇 |
国内免费 | 13748篇 |
专业分类
耳鼻咽喉 | 43667篇 |
儿科学 | 99831篇 |
妇产科学 | 81396篇 |
基础医学 | 507293篇 |
口腔科学 | 84177篇 |
临床医学 | 278298篇 |
内科学 | 555944篇 |
皮肤病学 | 85740篇 |
神经病学 | 272350篇 |
特种医学 | 125313篇 |
外国民族医学 | 361篇 |
外科学 | 496731篇 |
综合类 | 96708篇 |
现状与发展 | 23篇 |
一般理论 | 2167篇 |
预防医学 | 263770篇 |
眼科学 | 71111篇 |
药学 | 214247篇 |
22篇 | |
中国医学 | 9195篇 |
肿瘤学 | 146222篇 |
出版年
2021年 | 54579篇 |
2020年 | 34835篇 |
2019年 | 57780篇 |
2018年 | 70183篇 |
2017年 | 53527篇 |
2016年 | 59051篇 |
2015年 | 73398篇 |
2014年 | 107391篇 |
2013年 | 172419篇 |
2012年 | 83926篇 |
2011年 | 82924篇 |
2010年 | 114145篇 |
2009年 | 119440篇 |
2008年 | 70819篇 |
2007年 | 72818篇 |
2006年 | 83902篇 |
2005年 | 79900篇 |
2004年 | 81843篇 |
2003年 | 73239篇 |
2002年 | 63332篇 |
2001年 | 89200篇 |
2000年 | 81793篇 |
1999年 | 84934篇 |
1998年 | 63415篇 |
1997年 | 61769篇 |
1996年 | 59481篇 |
1995年 | 54927篇 |
1994年 | 49123篇 |
1993年 | 45914篇 |
1992年 | 58544篇 |
1991年 | 55234篇 |
1990年 | 52402篇 |
1989年 | 51796篇 |
1988年 | 48340篇 |
1987年 | 47257篇 |
1986年 | 45304篇 |
1985年 | 45495篇 |
1984年 | 43089篇 |
1983年 | 39921篇 |
1982年 | 39843篇 |
1981年 | 37589篇 |
1980年 | 35551篇 |
1979年 | 35092篇 |
1978年 | 32154篇 |
1977年 | 29701篇 |
1976年 | 27279篇 |
1975年 | 25791篇 |
1974年 | 26285篇 |
1973年 | 25130篇 |
1972年 | 23659篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Samo Lasi
Filip Szczepankiewicz Erica Dall'Armellina Arka Das Christopher Kelly Sven Plein Jürgen E. Schneider Markus Nilsson Irvin Teh 《NMR in biomedicine》2020,33(2)
Motion is a major confound in diffusion‐weighted imaging (DWI) in the body, and it is a common cause of image artefacts. The effects are particularly severe in cardiac applications, due to the nonrigid cyclical deformation of the myocardium. Spin echo‐based DWI commonly employs gradient moment‐nulling techniques to desensitise the acquisition to velocity and acceleration, ie, nulling gradient moments up to the 2nd order (M2‐nulled). However, current M2‐nulled DWI scans are limited to encode diffusion along a single direction at a time. We propose a method for designing b‐tensors of arbitrary shapes, including planar, spherical, prolate and oblate tensors, while nulling gradient moments up to the 2nd order and beyond. The design strategy comprises initialising the diffusion encoding gradients in two encoding blocks about the refocusing pulse, followed by appropriate scaling and rotation, which further enables nulling undesired effects of concomitant gradients. Proof‐of‐concept assessment of in vivo mean diffusivity (MD) was performed using linear and spherical tensor encoding (LTE and STE, respectively) in the hearts of five healthy volunteers. The results of the M2‐nulled STE showed that (a) the sequence was robust to cardiac motion, and (b) MD was higher than that acquired using standard M2‐nulled LTE, where diffusion‐weighting was applied in three orthogonal directions, which may be attributed to the presence of restricted diffusion and microscopic diffusion anisotropy. Provided adequate signal‐to‐noise ratio, STE could significantly shorten estimation of MD compared with the conventional LTE approach. Importantly, our theoretical analysis and the proposed gradient waveform design may be useful in microstructure imaging beyond diffusion tensor imaging where the effects of motion must be suppressed. 相似文献
992.
R. Asero A. V. Marzano S. Ferrucci M. Lorini V. Carbonelli M. Cugno 《Clinical and experimental immunology》2020,200(3):242-249
Chronic spontaneous urticaria (CSU) pathogenesis shows a complex and still unclear interplay between immunoglobulin (Ig)G- and IgE-mediated autoimmunity, leading to mast cell and basophil degranulation and wheal formation. The objective of this study was to evaluate at the same time IgE- and IgG-reactivity to well recognized and recently reported autoantigens in CSU patients, and to assess the effects of such reactivity on response to the anti-IgE monoclonal antibody omalizumab. Twenty CSU patients underwent omalizumab treatment. Urticaria activity score 7 (UAS7) was recorded at baseline and at different drug administration time-points for categorizing early-, late- or non-responders. At baseline, sera from the 20 patients and from 20 controls were tested for IgE and IgG autoantibodies to high- and low-affinity IgE receptors (FcεRI and FcεRII), tissue factor (TF) and thyroglobulin (TG) by immunoenzymatic methods. Antibody levels were compared with those of controls and analysed according to response. Eighteen patients were omalizumab responders (11 early and seven late), while two were non-responders. More than 50% of patients had contemporary IgE and IgG to at least to one of the four different autoantigens. Late responders showed higher levels of both anti-TF IgE and IgG than early responders (P = 0·011 and P = 0·035, respectively). Twenty-five per cent of patients had levels of anti-FcεRI IgE, exceeding the upper normal limit, suggesting that it could be a novel auto-allergen in CSU. In CSU, there is an autoimmune milieu characterized by the co-existence of IgE and IgG autoantibodies to the same antigen/allergen, particularly in late responders to omalizumab, possibly explaining the slower response. 相似文献
993.
994.
995.
996.
997.
998.
Characterization of Left Atrial Mechanics in Hypertrophic Cardiomyopathy and Essential Hypertension Using Vector Velocity Imaging 下载免费PDF全文
999.
1000.