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   4833457篇
  免费   393871篇
  国内免费   15935篇
耳鼻咽喉   69468篇
儿科学   154094篇
妇产科学   128633篇
基础医学   726467篇
口腔科学   135096篇
临床医学   440897篇
内科学   883352篇
皮肤病学   113775篇
神经病学   407196篇
特种医学   192543篇
外国民族医学   1327篇
外科学   732840篇
综合类   140026篇
现状与发展   23篇
一般理论   2757篇
预防医学   408779篇
眼科学   115156篇
药学   344457篇
  25篇
中国医学   12577篇
肿瘤学   233775篇
  2021年   56365篇
  2019年   59154篇
  2018年   75089篇
  2017年   57381篇
  2016年   63873篇
  2015年   76643篇
  2014年   111516篇
  2013年   177019篇
  2012年   134006篇
  2011年   140332篇
  2010年   128272篇
  2009年   129598篇
  2008年   127167篇
  2007年   136429篇
  2006年   144436篇
  2005年   139379篇
  2004年   140056篇
  2003年   130466篇
  2002年   120735篇
  2001年   183863篇
  2000年   181607篇
  1999年   164859篇
  1998年   75262篇
  1997年   70371篇
  1996年   68249篇
  1995年   64028篇
  1994年   58130篇
  1993年   53890篇
  1992年   123578篇
  1991年   119345篇
  1990年   114088篇
  1989年   110849篇
  1988年   102861篇
  1987年   101176篇
  1986年   95690篇
  1985年   93425篇
  1984年   76824篇
  1983年   67840篇
  1982年   51685篇
  1981年   47969篇
  1980年   45009篇
  1979年   68476篇
  1978年   53726篇
  1977年   47091篇
  1976年   44041篇
  1975年   44317篇
  1974年   50320篇
  1973年   48315篇
  1972年   45235篇
  1971年   41481篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Intratumor heterogeneity is a main cause of the dismal prognosis of glioblastoma (GBM). Yet, there remains a lack of a uniform assessment of the degree of heterogeneity. With a multiscale approach, we addressed the hypothesis that intratumor heterogeneity exists on different levels comprising traditional regional analyses, but also innovative methods including computer-assisted analysis of tumor morphology combined with epigenomic data. With this aim, 157 biopsies of 37 patients with therapy-naive IDH-wildtype GBM were analyzed regarding the intratumor variance of protein expression of glial marker GFAP, microglia marker Iba1 and proliferation marker Mib1. Hematoxylin and eosin stained slides were evaluated for tumor vascularization. For the estimation of pixel intensity and nuclear profiling, automated analysis was used. Additionally, DNA methylation profiling was conducted separately for the single biopsies. Scoring systems were established to integrate several parameters into one score for the four examined modalities of heterogeneity (regional, cellular, pixel-level and epigenomic). As a result, we could show that heterogeneity was detected in all four modalities. Furthermore, for the regional, cellular and epigenomic level, we confirmed the results of earlier studies stating that a higher degree of heterogeneity is associated with poorer overall survival. To integrate all modalities into one score, we designed a predictor of longer survival, which showed a highly significant separation regarding the OS. In conclusion, multiscale intratumor heterogeneity exists in glioblastoma and its degree has an impact on overall survival. In future studies, the implementation of a broadly feasible heterogeneity index should be considered.  相似文献   
12.
Journal of Medical Ultrasonics - Chronic liver disease is still a major problem because disease progression will ultimately lead to liver cirrhosis. Portal hypertension is the hallmark in advanced...  相似文献   
13.
14.
15.
16.
17.
18.
PurposeUnderstanding the value of genetic screening and testing for monogenic disorders requires high-quality, methodologically robust economic evaluations. This systematic review sought to assess the methodological quality among such studies and examined opportunities for improvement.MethodsWe searched PubMed, Cochrane, Embase, and Web of Science for economic evaluations of genetic screening/testing (2013-2019). Methodological rigor and adherence to best practices were systematically assessed using the British Medical Journal checklist.ResultsAcross the 47 identified studies, there were substantial variations in modeling approaches, reporting detail, and sophistication. Models ranged from simple decision trees to individual-level microsimulations that compared between 2 and >20 alternative interventions. Many studies failed to report sufficient detail to enable replication or did not justify modeling assumptions, especially for costing methods and utility values. Meta-analyses, systematic reviews, or calibration were rarely used to derive parameter estimates. Nearly all studies conducted some sensitivity analysis, and more sophisticated studies implemented probabilistic sensitivity/uncertainty analysis, threshold analysis, and value of information analysis.ConclusionWe describe a heterogeneous body of work and present recommendations and exemplar studies across the methodological domains of (1) perspective, scope, and parameter selection; (2) use of uncertainty/sensitivity analyses; and (3) reporting transparency for improvement in the economic evaluation of genetic screening/testing.  相似文献   
19.

The exercise pressor reflex is a feedback mechanism engaged upon stimulation of mechano- and metabosensitive skeletal muscle afferents. Activation of these afferents elicits a reflex increase in heart rate, blood pressure, and ventilation in an intensity-dependent manner. Consequently, the exercise pressor reflex has been postulated to be one of the principal mediators of the cardiorespiratory responses to exercise. In this updated review, we will discuss classical and recent advancements in our understating of the exercise pressor reflex function in both human and animal models. Particular attention will be paid to the afferent mechanisms and pathways involved during its activation, its effects on different target organs, its potential role in the abnormal cardiovascular response to exercise in diseased states, and the impact of age and biological sex on these responses. Finally, we will highlight some unanswered questions in the literature that may inspire future investigations in the field.

  相似文献   
20.
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