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   517684篇
  免费   34234篇
  国内免费   626篇
耳鼻咽喉   7030篇
儿科学   16868篇
妇产科学   13594篇
基础医学   85500篇
口腔科学   14575篇
临床医学   44531篇
内科学   94545篇
皮肤病学   12293篇
神经病学   36390篇
特种医学   18860篇
外国民族医学   63篇
外科学   77930篇
综合类   8469篇
一般理论   118篇
预防医学   39029篇
眼科学   12165篇
药学   40955篇
中国医学   1021篇
肿瘤学   28608篇
  2018年   5021篇
  2016年   4179篇
  2015年   4612篇
  2014年   6194篇
  2013年   9713篇
  2012年   13145篇
  2011年   14562篇
  2010年   8461篇
  2009年   7944篇
  2008年   13986篇
  2007年   14980篇
  2006年   15248篇
  2005年   14670篇
  2004年   14320篇
  2003年   13678篇
  2002年   13509篇
  2001年   24309篇
  2000年   25327篇
  1999年   20797篇
  1998年   5502篇
  1997年   4722篇
  1996年   4804篇
  1995年   4635篇
  1994年   4345篇
  1992年   15857篇
  1991年   16438篇
  1990年   16543篇
  1989年   15915篇
  1988年   14678篇
  1987年   14525篇
  1986年   13700篇
  1985年   13079篇
  1984年   9685篇
  1983年   8285篇
  1982年   4559篇
  1981年   4237篇
  1979年   9448篇
  1978年   6861篇
  1977年   5793篇
  1976年   5603篇
  1975年   6402篇
  1974年   7653篇
  1973年   7141篇
  1972年   6972篇
  1971年   6712篇
  1970年   6184篇
  1969年   5915篇
  1968年   5580篇
  1967年   5031篇
  1966年   4467篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
Monatsschrift Kinderheilkunde - Fusionen und Übernahmen in der Pharmaindustrie haben zu einer Konzentration geführt, von der auch die Impfstoffproduktion mit nur noch wenigen global...  相似文献   
93.
This evidence- and consensus-based guideline on the treatment of psoriasis vulgaris was developed following the EuroGuiDerm Guideline and Consensus Statement Development Manual. The first part of the guideline includes general information on the scope and purpose, health questions covered, target users and strength/limitations of the guideline. Suggestions for disease severity grading and treatment goals are provided. It presents the general treatment recommendations as well as detailed management and monitoring recommendations for the individual drugs. The treatment options discussed in this guideline are as follows: acitretin, ciclosporin, fumarates, methotrexate, adalimumab, apremilast, brodalumab, certolizumab pegol, etanercept, guselkumab, infliximab, ixekizumab, risankizumab, secukinumab, tildrakizumab and ustekinumab.  相似文献   
94.
Abstract

This study was undertaken to compare the concentrations of pro- and anti-angiogenic growth factors, nitric oxide (NO) stable metabolites in maternal serum and embryonic left ventricular (LV) isovolumic relaxation time (IRT, ms) during the first trimester in two groups of women: with pregnancy conceived by assisted reproductive technologies (ART, n?=?39) and normally conceived (control group, n?=?68) pregnancy. The concentration of vasoconstrictor endothelin 1 was 45.5 times more in ART than in control group. On the contrary, the concentrations of NO stable metabolites in ART were 1.9 times less than in control women. The assessment of angiogenic suppressors in ART women demonstrates the decrease in s-endoglin concentration was 1.6 times and in soluble receptor to vascular endothelial growth factor concentration was 2.0 times in comparison with control group. There was a significant increase in LV IRT in ART embryos in comparison to control ones. These data suggest significant changes in pro- anti-angiogenic factors balance and increase in vascular impedance in ART-conceived embryos.  相似文献   
95.
BACKGROUND AND PURPOSE:Cognitive challenges are prevalent in survivors of glioma, but their neurobiology is incompletely understood. The purpose of this study was to investigate the effect of glioma presence and tumor characteristics on resting-state functional connectivity and amplitude of low-frequency fluctuations of the salience network, a key neural network associated with cognition.MATERIALS AND METHODS:Sixty-nine patients with glioma (mean age, 48.74 [SD, 14.32] years) who underwent resting-state fMRI were compared with 31 healthy controls (mean age, 49.68 [SD, 15.54] years). We identified 4 salience network ROIs: left/right dorsal anterior cingulate cortex and left/right anterior insula. Average salience network resting-state functional connectivity and amplitude of low-frequency fluctuations within the 4 salience network ROIs were computed.RESULTS:Patients with gliomas showed decreased overall salience network resting-state functional connectivity (P = .001) and increased amplitude of low-frequency fluctuations in all salience network ROIs (P < .01) except in the left dorsal anterior cingulate cortex. Compared with controls, patients with left-sided gliomas showed increased amplitude of low-frequency fluctuations in the right dorsal anterior cingulate cortex (P = .002) and right anterior insula (P < .001), and patients with right-sided gliomas showed increased amplitude of low-frequency fluctuations in the left anterior insula (P = .002). Anterior tumors were associated with decreased salience network resting-state functional connectivity (P < .001) and increased amplitude of low-frequency fluctuations in the right anterior insula, left anterior insula, and right dorsal anterior cingulate cortex. Patients with high-grade gliomas had decreased salience network resting-state functional connectivity compared with healthy controls (P < .05). The right anterior insula showed increased amplitude of low-frequency fluctuations in patients with grade II and IV gliomas compared with controls (P < .01).CONCLUSIONS:By demonstrating decreased resting-state functional connectivity and an increased amplitude of low-frequency fluctuations related to the salience network in patients with glioma, this study adds to our understanding of the neurobiology underpinning observable cognitive deficits in these patients. In addition to more conventional functional connectivity, amplitude of low-frequency fluctuations is a promising functional-imaging biomarker of tumor-induced vascular and neural pathology.

Detrimental effects of cancer on cognitive function and, consequently, on the quality of life are emerging as a key focus of cancer survivorship both in research and clinical practice.1,2 Brain tumors have been shown to affect memory, processing, and attention in patients; however, their underlying neurobiology is incompletely understood.3 Using resting-state functional MR imaging (rsfMRI) to evaluate changes in cognitive resting-state networks may provide a better understanding of the pathology underlying the observable cognitive disruptions in gliomas, the most common primary brain tumor in adults.A “triple network model” of neurocognitive pathology has been proposed, which encompasses the default mode network, involved in mind wandering; the central executive network, involved in decision-making; and the salience network (SN), implicated in modulating activation of the default mode network and central executive network by detecting the presence of salient stimuli.4-8 While previous rsfMRI research has largely focused on tumor-induced changes in the default mode network,9,10 our study examined the less-studied SN, a network rooted in the anterior insula and the dorsal anterior cingulate cortex.6Prior studies evaluating gliomas and SN resting-state functional connectivity (RSFC) provided conflicting results in small patient samples: Maesawa et al10 found no significant differences in the SN in 12 patients, while Liu et al11 more recently found decreased SN connectivity in 13 patients. Gliomas impact the integrity of the neurovascular unit to varying degrees, resulting in neurovascular uncoupling that has been reported to confound fMRI interpretations in patients with brain tumors.12-14 Additionally, research has reported neuronal plasticity manifested by structural reorganization and functional remodeling of neural networks in patients with gliomas with possible alterations in clinically observable cognitive manifestations.15-17 An rsfMRI metric, the amplitude of low-frequency fluctuations (ALFF), has recently shown promise as a biomarker for brain plasticity and hemodynamic characterization, including neurovascular uncoupling in patients with gliomas.15-19The purpose of this study was to investigate the effect of glioma presence and tumor characteristics on overall RSFC and regional normalized ALFF within the SN in a large patient population. We hypothesized that there would be decreased average SN RSFC and altered ALFF in patients with gliomas compared with healthy controls. Recent studies have acknowledged that gliomas have variable effects on network integrity based on lesion location and proximity to network ROIs,20-22 and unilateral gliomas can be associated with plasticity in both the ipsilateral and contralateral hemispheres.11,17 Research also supports differences in resting-state network reorganization in aggressive high-grade gliomas compared with slower-growing low-grade gliomas.20,23 Therefore, we also hypothesized that there would be differences in average SN RSFC and regional ALFF in patients based on the anterior-versus-posterior location, hemispheric side, and grade of glioma.  相似文献   
96.
97.
98.
99.
100.
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