全文获取类型
收费全文 | 377697篇 |
免费 | 25059篇 |
国内免费 | 2903篇 |
专业分类
耳鼻咽喉 | 5201篇 |
儿科学 | 8196篇 |
妇产科学 | 10090篇 |
基础医学 | 52953篇 |
口腔科学 | 11787篇 |
临床医学 | 30052篇 |
内科学 | 78035篇 |
皮肤病学 | 8548篇 |
神经病学 | 27090篇 |
特种医学 | 13932篇 |
外国民族医学 | 83篇 |
外科学 | 60621篇 |
综合类 | 10109篇 |
现状与发展 | 1篇 |
一般理论 | 64篇 |
预防医学 | 17359篇 |
眼科学 | 9439篇 |
药学 | 31005篇 |
5篇 | |
中国医学 | 2239篇 |
肿瘤学 | 28850篇 |
出版年
2021年 | 2426篇 |
2019年 | 2772篇 |
2018年 | 4573篇 |
2017年 | 3463篇 |
2016年 | 3556篇 |
2015年 | 4063篇 |
2014年 | 5764篇 |
2013年 | 7448篇 |
2012年 | 10104篇 |
2011年 | 10294篇 |
2010年 | 6229篇 |
2009年 | 5881篇 |
2008年 | 9470篇 |
2007年 | 10318篇 |
2006年 | 10236篇 |
2005年 | 9316篇 |
2004年 | 8803篇 |
2003年 | 8523篇 |
2002年 | 8184篇 |
2001年 | 28272篇 |
2000年 | 28784篇 |
1999年 | 23634篇 |
1998年 | 5040篇 |
1997年 | 4115篇 |
1996年 | 3690篇 |
1995年 | 3487篇 |
1994年 | 3104篇 |
1993年 | 2841篇 |
1992年 | 16038篇 |
1991年 | 14811篇 |
1990年 | 14156篇 |
1989年 | 13955篇 |
1988年 | 12578篇 |
1987年 | 12057篇 |
1986年 | 11098篇 |
1985年 | 10322篇 |
1984年 | 6909篇 |
1983年 | 5600篇 |
1982年 | 2716篇 |
1979年 | 5476篇 |
1978年 | 3345篇 |
1977年 | 2963篇 |
1975年 | 2636篇 |
1974年 | 3064篇 |
1973年 | 2864篇 |
1972年 | 2828篇 |
1971年 | 2773篇 |
1970年 | 2509篇 |
1969年 | 2543篇 |
1968年 | 2251篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
31.
目的筛选并分析与早发性乳腺癌发生、发展相关的靶基因。 方法(1)在美国国立生物技术信息中心的公共基因芯片数据库(GEO)中检索早发性乳腺癌样本及非早发性乳腺癌样本相关基因芯片数据。对上述数据使用GEO2R、R4.1.2及Venn软件筛选出相关差异表达基因(DEGs),并运用在线分析工具(Web Gestalt)对DEGs,进行相关功能和信号通路富集分析。(2)同时,通过String在线数据库构建DEGs编码的蛋白质-蛋白质相互作用(PPI)网络,并利用Cytohubba插件对该网络中的基因进行评分,筛选出枢纽基因。将枢纽基因导入Kaplan-Meier生存分析工具(Kaplan-Meier Plotter),评估枢纽基因在早发性乳腺癌的预后价值。(3)将肿瘤基因组图谱(TCGA)数据库中的肿瘤组织以年龄为标准进行分组,分析枢纽基因在各年龄组中的表达,并与正常组织中的表达进行比较,对得到的枢纽基因进行验证。DEGs表达量的多组间比较使用Kruskal-Wallis H检验,使用Bonferroni法进行两两比较。 结果(1)筛选出编号为GSE89116、GSE109169、GSE36295的基因芯片数据集,共得到80个差异表达基因,其中上调差异表达基因17个,下调差异表达基因63个。富集分析显示:DEGs主要富集在脂质代谢和氧化还原过程以及PPAR信号通路、AMPK信号通路上。(2)在PPI中发现主要的关键基因为PPARG、ADIPOQ、LIPE、PCK1、PDK4、ACACB、PLIN1、CAV1、CD36、ANGPTL4。ACACB、ADIPOQ、CAV1、LIPE、PLIN1、PPARG基因的低表达与乳腺癌患者的不良OS相关(HR=0.69、0.84、0.76、0.88、0.78、0.82;95%CI:0.59~0.80、0.76~0.93、0.67~0.83、0.79~0.97、0.70~0.86、0.73~0.90;P均<0.050)。(3)ACACB、ADIPOQ、LIPE、PLIN1、CAV1及PPARG这6个与预后相关的基因在正常组织中的表达量均远高于各年龄组肿瘤组织中的表达量(χ2=104.03、179.57、161.85、189.87、118.56、103.62,P均<0.001),早发性乳腺癌组(21~40岁)的LIPE、PLIN1表达量低于41~60岁、61~80岁年龄组,差异具有统计学意义(LIPE: Z=21.07、23.12, P均<0.050; PLIN1:Z=16.89、18.76, P均<0.050)。 结论早发性乳腺癌与非早发性乳腺癌存在差异基因表达谱,LIPE、PLIN1可能是早发性乳腺癌发生、发展的关键基因。 相似文献
32.
33.
34.
Inna Y. Gong Nigel S. Tan Sammy H. Ali Gerald Lebovic Muhammad Mamdani Shaun G. Goodman Dennis T. Ko Andreas Laupacis Andrew T. Yan 《The Canadian journal of cardiology》2019,35(5):653-660
Background
Although it is known that women do not participate in trials as frequently as men, there are limited recent data examining how women recruitment has changed over time.Methods
We conducted MEDLINE search using a validated strategy for randomized trials published in New England Journal of Medicine, Lancet, and Journal of the American Medical Association between 1986 and 2015, and included trials evaluating pharmacologic or nonpharmacologic therapies. We abstracted data on demographics, intervention type, clinical indication, and trial design characteristics, and examined their relationships with women enrollment.Results
In total, 598 trials met inclusion criteria. Women enrollment increased significantly over time (21% between 1986 and 1990 to 33% between 2011 and 2015; Pfor trend < 0.001) and did not differ by journal or funding source. Women enrollment varied with clinical indication, comprising 37% for non–coronary artery disease vascular trials, 30% for coronary artery disease trials, 28% for heart failure trials, and 28% for arrhythmia trials (P < 0.001), which were all significantly lower than the expected proportion in disease populations (P < 0.001). Women enrollment varied with trial type (31%, 29%, and 26% for pharmacologic, device, and procedural trials, respectively; P = 0.001). These findings were corroborated using multivariable analysis. We found significant positive correlations between women enrolled, and mean age and total number of participants. Fewer women were enrolled in trials reporting statistically significant results than those who did not (P = 0.001).Conclusions
Although enrollment of women has increased over time, it remains lower than the relative proportion in the disease population. Future studies should elucidate the reasons for persistent under-representation of women in clinical trials. 相似文献35.
Hedy S. Wald Jordan White Shmuel P. Reis Angela Y. Esquibel David Anthony 《Medical teacher》2019,41(2):152-160
Aim: Clerkship-specific interactive reflective writing (IRW)-enhanced reflection may enhance professional identity formation (PIF), a fundamental goal of medical education. PIF process as revealed in students? reflective writing (RW) has been understudied.Methods: The authors developed an IRW curriculum within a Family Medicine Clerkship (FMC) and analyzed students? reflections about challenging/difficult patient encounters using immersion-crystallization qualitative analysis.Results: The qualitative analysis identified 26 unique emergent themes and five distinct thematic categories (1. Role of emotions, 2. Role of cognition, 3. Behaviorally responding to situational context, 4. Patient factors, and 5. External factors) as well as an emergent PIF model from a directed content analysis. The model describes students? backgrounds, emotions and previous experiences in medicine merging with external factors and processed during student?patient interactions. The RWs also revealed that processing often involves polarities (e.g. empathy/lack of empathy or encouragement/disillusionment) as well as dissonance between idealized visions and lived reality.Conclusions: IRW facilitates and ideally supports grappling with the lived reality of medicine; uncovering a “positive hidden curriculum” within medical education. The authors propose engaging learners in guided critical reflection about complex experiences for meaning-making within a safe learning climate as a valuable way to cultivate reflective, resilient professionals with “prepared” minds and hearts for inevitable challenges of healthcare practice. 相似文献
36.
Y. Ermias I.A. Morgan K.M. Curtis M.K. Whiteman L.G. Horton L.B. Zapata 《Contraception》2019,99(5):300-305
ObjectiveIdentify factors associated with healthcare providers' frequency of depot medroxyprogesterone acetate (DMPA) provision to adolescents.Study designWe analyzed data from surveys mailed to a nationally representative sample of public-sector providers and office-based physicians (n=1984). We estimated adjusted odds ratios (aORs) and 95% confidence intervals (CIs) of factors associated with frequent DMPA provision to adolescents in the past year.ResultsAlthough most providers (>95%) considered DMPA safe for adolescents, fewer reported frequent provision (89% of public-sector providers; 64% of office-based physicians). Among public-sector providers, factors associated with lower odds of frequent provision included working in settings without Title X funding (aOR 0.44, 95% CI 0.30–0.64), reporting primary care as their primary clinical focus versus reproductive or adolescent health (aOR 0.42, 95% CI 0.28–0.61), and providing fewer patients with family planning services. Among office-based physicians, factors associated with lower odds of frequent provision included specializing in obstetrics/gynecology (aOR 0.50, 95% CI 0.27–0.91) and family medicine (aOR 0.21, 95% CI 0.09–0.47) versus adolescent medicine, completing training ≥15 versus <5 years ago (aOR 0.27, 95% CI 0.09–0.83), and reporting that 0–24% of patients pay with Medicaid or other government healthcare assistance versus ≥50% (aOR 0.23, 95% CI 0.09–0.61). The reason most commonly reported by providers for infrequent DMPA provision was patient preference for another method.ConclusionsWhile most providers reported frequently providing DMPA to adolescents, training on evidence-based recommendations for contraception, focused on subgroups of providers with lower odds of frequent DMPA provision, may increase adolescents' access to contraception.ImplicationsAlthough >95% of providers considered depot medroxyprogesterone (DMPA) a safe contraceptive for adolescents, only 89% of public-sector providers and 64% of office-based physicians reported frequently providing DMPA to adolescents. Provider training on evidence-based recommendations for contraception counseling and provision may increase adolescents' access to DMPA and all methods of contraception. 相似文献
37.
38.
39.