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   1402925篇
  免费   109138篇
  国内免费   10185篇
耳鼻咽喉   17445篇
儿科学   44294篇
妇产科学   37310篇
基础医学   205142篇
口腔科学   37372篇
临床医学   139508篇
内科学   266180篇
皮肤病学   27040篇
神经病学   115252篇
特种医学   51125篇
外国民族医学   427篇
外科学   191010篇
综合类   43132篇
一般理论   463篇
预防医学   117906篇
眼科学   31307篇
药学   106970篇
  57篇
中国医学   7811篇
肿瘤学   82497篇
  2021年   13058篇
  2019年   14381篇
  2018年   18934篇
  2017年   14987篇
  2016年   15302篇
  2015年   18903篇
  2014年   25443篇
  2013年   35931篇
  2012年   50040篇
  2011年   53479篇
  2010年   31195篇
  2009年   27991篇
  2008年   46634篇
  2007年   49244篇
  2006年   49283篇
  2005年   47855篇
  2004年   44165篇
  2003年   41834篇
  2002年   40327篇
  2001年   62382篇
  2000年   64252篇
  1999年   54214篇
  1998年   15223篇
  1997年   13760篇
  1996年   13307篇
  1995年   13384篇
  1994年   12431篇
  1993年   11409篇
  1992年   42114篇
  1991年   41265篇
  1990年   39914篇
  1989年   37713篇
  1988年   34870篇
  1987年   33943篇
  1986年   32316篇
  1985年   30769篇
  1984年   23053篇
  1983年   19574篇
  1982年   11722篇
  1979年   20781篇
  1978年   14769篇
  1977年   12014篇
  1976年   11833篇
  1975年   12081篇
  1974年   14774篇
  1973年   14452篇
  1972年   13349篇
  1971年   12408篇
  1970年   11472篇
  1969年   10402篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Tamoxifen prevents recurrence of breast cancer and is suggested for preventive risk-reducing therapy. Tamoxifen reduces mammographic density, a proxy for therapy response, but little is known about its effects in remodelling normal breast tissue. Our study, a substudy within the double-blinded dose-determination trial KARISMA, investigated tamoxifen-specific changes in breast tissue composition and histological markers in healthy women. We included 83 healthy women randomised to 6 months daily intake of 20, 10, 5, 2.5, 1 mg of tamoxifen or placebo. The groups were combined to “no dose” (0-1 mg), “low-dose” (2.5-5 mg) or “high-dose” (10-20 mg) of tamoxifen. Ultrasound-guided biopsies were collected before and after tamoxifen exposure. In each biopsy, epithelial, stromal and adipose tissues was quantified, and expression of epithelial and stromal Ki67, oestrogen receptor (ER) and progesterone receptor (PR) analysed. Mammographic density using STRATUS was measured at baseline and end-of-tamoxifen-exposure. We found that different doses of tamoxifen reduced mammographic density and glandular-epithelial area in premenopausal women and associated with reduced epithelium and increased adipose tissue. High-dose tamoxifen also decreased epithelial ER and PR expressions in premenopausal women. Premenopausal women with the greatest reduction in proliferation also had the greatest epithelial reduction. In postmenopausal women, high-dose tamoxifen decreased the epithelial area with no measurable density decrease. Tamoxifen at both low and high doses influences breast tissue composition and expression of histological markers in the normal breast. Our findings connect epithelial proliferation with tissue remodelling in premenopausal women and provide novel insights to understanding biological mechanisms of primary prevention with tamoxifen.  相似文献   
3.
4.

Introduction

Left ventricular (LV) dysfunction is estimated to occur in 10%–25% of the general intensive care unit (ICU) population and is frequently seen as regional wall motion abnormalities (RWMAs). Although RWMA is mostly attributed to myocardial ischemia or infarction, some studies have suggested that nonischemic RWMA might also be prevalent. We sought to establish that RWMA can be seen in critically ill patients with normal coronary arteries and to explore reasons for RWMA in this population.

Methods

In this retrospective study, data from the hospital angiography register and the ICU register were collated between 2012 and 2019. Patients were identified who underwent angiography in conjunction with their ICU stay and had RWMA on echocardiography. Patients were divided into either those with non-obstructed or those with obstructed coronary arteries. Cardiac magnetic resonance imaging (cMRI) examinations were reviewed if they had been performed on patients with non-obstructed coronaries.

Results

We identified 53 patients with RWMA and non-obstructed coronary arteries and 204 patients with RWMA and obstructed coronary arteries. Patients with non-obstructed coronary arteries were more often female, younger, and had fewer cardiovascular risk factors. They less commonly had ST elevation, but more frequently had T-wave inversion or serious arrhythmias. Troponin levels were higher in patients with obstructed coronary arteries, but NT-proBNP was similar between the groups. There were no differences in risk-adjusted 90-day mortality between patients with non-obstructed versus obstructed coronary arteries (OR 1.21, [95% CI 0.56–2.64], p = .628). In those with non-obstructed coronary arteries, follow-up echocardiography was available for 38 patients, of whom 30 showed normalization of cardiac function. Of the 14 patients with non-obstructed coronary arteries on whom cMRI was performed, 7 had a tentative diagnosis of Takotsubo syndrome or myocardial stunning; 4 had a myocardial infarction (preexisting in 3 cases); 1 patient had acute myocarditis; 1 patient had post-myocarditis; and 1 patient was diagnosed with dilated cardiomyopathy.

Conclusion

RWMA can be seen to occur in critically ill patients in the absence of coronary artery obstruction. Several conditions can cause regional hypokinesia, and cMRI is useful to evaluate the underlying etiology.  相似文献   
5.
6.
目的 运用网络药理学方法及分子对接技术探讨黄芪干预腹膜纤维化的可能机制。方法 利用中药系统药理学数据库及分析平台(TCMSP)检索黄芪的主要化学成分及靶点,并补充文献报道相关药理作用的成分作为潜在活性成分。以"peritoneal fibrosis"为关键词分别在OMIM、Genecards获取目前已知的与腹膜纤维化相关的疾病靶点,后取两者的交集靶点;对交集基因通过STRING数据库与Cytoscape 3.7.2软件构建"药物-成分-靶点-疾病"网络及蛋白互作(PPI)网络并筛选核心网络。基于R软件使用Bioconductor生物信息软件对核心靶点进行GO及KEGG富集分析,最终采用AutoDock软件将主要有效成分与核心靶点进行分子对接,得出其结合能力。结果 筛选出20个黄芪活性成分及文献报道有相关药理作用4个, 457药物作用靶点,与674个腹膜纤维化病靶点取交集,得到86个共同靶点。GO功能富集分析提示黄芪拮抗腹膜纤维化主要参与了蛋白激酶B信号转导的调节、细胞对化学的应激反应、炎症反应的调节等通路; KEGG通路富集分析主要涉及调控肿瘤、磷脂酰肌醇-3-羟激酶-蛋白激酶B(PI3K-Akt)、晚期糖基化终末产物/晚期糖基化终末产物受体(AGE-RAGE)、人类巨细胞病毒感染、HIF-1信号通路等;分子对接结果显示关键靶点与活性成分具有较好的结合能力。结论 黄芪治疗腹膜纤维化的分子机制,可能与抑制炎症及氧化应激反应、调节多种信号通路等相关。  相似文献   
7.
目的 了解江苏省省级专科护士工作投入现状及影响因素,为针对性管理提供参考。方法 采用一般资料调查问卷与专科护士工作投入量表对2 472名省级专科护士进行调查分析。结果 专科护士工作投入总均分为4.06±0.46;多元线性回归分析显示,性别、聘任方式、专科类别、工作类型、出任专科护理门诊、论文发表是专科护士工作投入的影响因素(P<0.05,P<0.01)。结论 专科护士工作投入水平较高,其影响因素较多,护理管理者应关注专科护士专业开展现况,采取针对性措施支持专科护理的有效开展,从而进一步提高专科护士的工作投入水平。  相似文献   
8.
Cognitive Therapy and Research - Despite interest in psychological inflexibility as a marker of suicide risk, no measure of psychological inflexibility specific to SI exists. The present study...  相似文献   
9.
目的 分析重症患者营养支持期间发生再喂养综合征的危险因素,为早期识别及预防再喂养综合征提供参考。方法 检索中国知网、万方数据库、中华医学期刊全文数据库、中国生物医学文献数据库、维普网、PubMed、Embase、Cochrane Library、Elsevier关于重症患者再喂养综合征危险因素的文献,检索时间为各数据库建库至2021年12月,采用RevMan5.3进行Meta分析。结果 纳入13篇文献,包括2 519例患者,其中病例组793例,对照组1 726例;Meta分析合并效应值显示年龄(WMD=4.69)、APACHEⅡ评分(WMD=2.50)、BMI(WMD=-0.94)、白蛋白水平(OR=4.61)、前白蛋白水平(WMD=-53.46)、基线血镁水平(WMD=-0.05)、基线血钾水平(WMD=0.18)、基线血磷水平(WMD=-0.07)是重症患者发生再喂养综合征的危险因素(P<0.05,P<0.01)。结论 基于现有证据,重症患者再喂养综合征的危险因素包括年龄、APACHEⅡ评分、营养状况及电解质水平,医护人员需密切关注重症患者营养支持期间能量、蛋白质及电解...  相似文献   
10.
Maternal and Child Health Journal - Early life exposures can have an impact on a child’s developmental trajectory and children born late preterm (34–36&nbsp;weeks gestational age)...  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