首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   83348篇
  免费   7039篇
  国内免费   2770篇
耳鼻咽喉   436篇
儿科学   1115篇
妇产科学   2068篇
基础医学   6808篇
口腔科学   897篇
临床医学   7374篇
内科学   10175篇
皮肤病学   1185篇
神经病学   3139篇
特种医学   1229篇
外国民族医学   7篇
外科学   4624篇
综合类   10889篇
现状与发展   6篇
一般理论   3篇
预防医学   5608篇
眼科学   875篇
药学   27995篇
  127篇
中国医学   3023篇
肿瘤学   5574篇
  2024年   785篇
  2023年   1340篇
  2022年   2100篇
  2021年   2736篇
  2020年   2818篇
  2019年   2766篇
  2018年   2883篇
  2017年   2889篇
  2016年   2854篇
  2015年   2924篇
  2014年   4900篇
  2013年   7869篇
  2012年   5020篇
  2011年   5437篇
  2010年   4330篇
  2009年   4285篇
  2008年   4194篇
  2007年   4333篇
  2006年   3992篇
  2005年   3718篇
  2004年   3039篇
  2003年   2811篇
  2002年   2190篇
  2001年   1946篇
  2000年   1647篇
  1999年   1337篇
  1998年   1080篇
  1997年   1043篇
  1996年   745篇
  1995年   722篇
  1994年   577篇
  1993年   486篇
  1992年   480篇
  1991年   383篇
  1990年   344篇
  1989年   281篇
  1988年   258篇
  1987年   226篇
  1986年   186篇
  1985年   209篇
  1984年   180篇
  1983年   144篇
  1982年   124篇
  1981年   92篇
  1980年   78篇
  1979年   61篇
  1978年   64篇
  1977年   51篇
  1976年   53篇
  1975年   51篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Transmission is a potential property of live viral vaccines that remains largely unexploited but may lie within the realm of many engineering designs. While likely unacceptable for vaccines of humans, transmission may be highly desirable for vaccines of wildlife, both to protect natural populations and also to limit zoonotic transmissions into humans. Defying intuition, transmission alone does not guarantee that a vaccine will perform well: the benefit of transmission over no transmission depends on and increases with the basic reproductive number of the vaccine, R0. The R0 of an infectious agent in a homogeneous population is typically considered to be a fixed number, but some evidence suggests that dissemination of transmissible vaccines may change through time. One obvious possibility is that transmission will be greater from hosts directly vaccinated than from hosts who acquire the vaccine passively, but other types of change might also accrue. Whenever transmission changes over time, the R0 estimated from directly vaccinated hosts will not reflect the vaccine’s long term impact. As there is no theory on the consequences of changing transmission rates for a vaccine, we derive conditions for a transmissible vaccine with varying transmission rates to protect a population from pathogen invasion. Being the first in the transmission chain, the R0 from directly vaccinated hosts has a larger effect than those from later steps in the chain. This mathematical property reveals that a transmissible vaccine with low long term transmission may nonetheless realize a big impact if early transmission is high. Furthermore, there may be ways to artificially elevate early transmission, thereby achieving high herd immunity from transmission while ensuring that the vaccine will ultimately die out.  相似文献   
3.
Soft tissue sarcomas (STS) are rare tumours presenting as soft tissue lumps. Ultrasound is often the primary modality for the initial assessment, with MRI the mainstay for lesion characterisation. PET/CT along with other emerging MRI sequences are used in certain situations as an adjunct and problem solving tool in STS staging and assessment of disease recurrence. Recent advances include the promise of whole body MRI, hybrid PET/MRI, diffusion weighted imaging, dynamic contrast enhanced MRI and advances in artificial intelligence. This article discusses current concepts in extremity STS imaging and highlights recent advances.  相似文献   
4.
《Clinical neurophysiology》2021,132(10):2639-2653
ObjectiveThis study brought together over 60 transcranial magnetic stimulation (TMS) researchers to create the largest known sample of individual participant single and paired-pulse TMS data to date, enabling a more comprehensive evaluation of factors driving response variability.MethodsAuthors of previously published studies were contacted and asked to share deidentified individual TMS data. Mixed-effects regression investigated a range of individual and study level variables for their contribution to variability in response to single and paired-pulse TMS data.Results687 healthy participant’s data were pooled across 35 studies. Target muscle, pulse waveform, neuronavigation use, and TMS machine significantly predicted an individual’s single-pulse TMS amplitude. Baseline motor evoked potential amplitude, motor cortex hemisphere, and motor threshold (MT) significantly predicted short-interval intracortical inhibition response. Baseline motor evoked potential amplitude, test stimulus intensity, interstimulus interval, and MT significantly predicted intracortical facilitation response. Age, hemisphere, and TMS machine significantly predicted MT.ConclusionsThis large-scale analysis has identified a number of factors influencing participants’ responses to single and paired-pulse TMS. We provide specific recommendations to minimise interindividual variability in single and paired-pulse TMS data.SignificanceThis study has used large-scale analyses to give clarity to factors driving variance in TMS data. We hope that this ongoing collaborative approach will increase standardisation of methods and thus the utility of single and paired-pulse TMS.  相似文献   
5.
6.
7.
目的对肝内胆汁淤积症孕妇的胎儿不良结局进行分析研究。方法随机选择在本院接受治疗的肝内胆汁淤积症孕妇作为观察组,与同期在本院正常分娩的对照组孕妇相比胎儿的不良结局。结果观察组的分娩结果 :12例早产、5例流产、5例死胎、4例新生儿窒息、40例正常分娩。对照组的分娩结果 :1例早产、1例新生儿窒息,64例正常分娩。观察组中胎儿不良结局发生率显著高于对照组,P <0.05;观察组中重度患者的胎儿不良结局发生率高于轻度患者,P <0.05。结论肝内胆汁淤积症导致胎儿不良结局发生率升高,应对加强对肝内胆汁淤积症的预防从而改善胎儿结局。  相似文献   
8.
9.
目的 总结貌似多发性硬化的皮层下梗死和白质脑病的常染色体显性遗传性脑动脉病(CADASIL)的临床特点.方法 报告1例经基因检查和周围神经活检确诊为CADASIL的临床资料.结果 患者腓肠神经活检可见有髓神经纤维密度轻度减少,电镜下可见神经束膜小动脉中层平滑肌细胞外大量颗粒性电子致密嗜锇颗粒物质(GOM)沉积.基因检测显示Notch3基因4号外显子Cys117Arg突变.结论 为避免CADASIL的漏诊及误诊,凡遇青年反复脑卒中发作,又无高血压、糖尿病等常见的血管病危险因素,虽无偏头痛病史,亦应注意追问家族史并做基因检测和周围神经活检.  相似文献   
10.
The transdermal delivery of 2 fluorescent probes with similar molecular weight but different lipophilicity, into and through the skin from 2 commercially available transdermal bases, pluronic lecithin organogel, and Lipoderm® has been evaluated. First, in vitro penetration of fluorescein sodium and fluorescein (free acid) through porcine skin was evaluated. Retention and depth distribution profiles in skin were obtained by tape stripping and then followed by optical sectioning using multiphoton microscopy. The results showed that Lipoderm® led to an enhanced penetration of the hydrophilic compound, fluorescein sodium. For the lipophilic compound fluorescein (free acid), Lipoderm® performed similar to pluronic lecithin organogel base, where minimal drug was detected in either receptor phase. The skin retention and depth distribution results also showed that the hydrophilic fluorescein sodium had high skin retention with Lipoderm®, whereas fluorescein (free acid) had very low penetration and retention with increasing skin depth. Moreover, optical sectioning by multiphoton microscopy revealed an uneven distribution of probes across the skin in the x-y plane for both transdermal bases. This work showed that a hydrophilic compound has significantly increased skin penetration and retention when formulated with Lipoderm®, and the skin retention of the probe was the main determinant of its skin flux.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号