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   40712篇
  免费   2749篇
  国内免费   986篇
耳鼻咽喉   108篇
儿科学   600篇
妇产科学   326篇
基础医学   5285篇
口腔科学   660篇
临床医学   2808篇
内科学   4595篇
皮肤病学   242篇
神经病学   3855篇
特种医学   1026篇
外国民族医学   2篇
外科学   1517篇
综合类   3232篇
现状与发展   2篇
预防医学   3932篇
眼科学   166篇
药学   10651篇
  12篇
中国医学   3973篇
肿瘤学   1455篇
  2024年   100篇
  2023年   557篇
  2022年   1023篇
  2021年   1416篇
  2020年   1283篇
  2019年   1257篇
  2018年   1229篇
  2017年   1342篇
  2016年   1280篇
  2015年   1201篇
  2014年   2092篇
  2013年   3349篇
  2012年   1877篇
  2011年   2280篇
  2010年   1543篇
  2009年   1809篇
  2008年   1814篇
  2007年   1788篇
  2006年   1479篇
  2005年   1320篇
  2004年   1144篇
  2003年   1035篇
  2002年   902篇
  2001年   870篇
  2000年   652篇
  1999年   663篇
  1998年   673篇
  1997年   582篇
  1996年   567篇
  1995年   554篇
  1994年   466篇
  1993年   450篇
  1992年   453篇
  1991年   417篇
  1990年   389篇
  1989年   394篇
  1988年   353篇
  1987年   339篇
  1986年   328篇
  1985年   447篇
  1984年   406篇
  1983年   280篇
  1982年   355篇
  1981年   278篇
  1980年   284篇
  1979年   210篇
  1978年   222篇
  1977年   160篇
  1976年   197篇
  1975年   80篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
内生菌由细菌、真菌、古菌和原生生物组成,它们生活在植物的活体组织中,具有丰富的次级代谢产物多样性。人参内生菌在人参的生长发育、次级代谢产物的生成和环境适应等方面均有重要的促进作用,对人参的产量和品质有较大影响。随着人们在微生物领域研究的深入,高通量测序技术已经成为研究植物内生菌的重要方法。文章主要从人参内生菌分离与鉴定研究方法、人参内生菌的多样性、人参内生菌及其次级代谢产物的活性、人参内生菌对宿主的影响等4个方面对人参内生菌近年来的研究进展进行讨论,并对其发展方向提出展望,以期为药用植物内生菌研究和品质改良提供新思路、新方法。  相似文献   
2.
姚海艳  史珣瑜  施江 《全科护理》2021,19(4):566-569
目的:探讨经皮冠状动脉介入(PCI)术后病人的体力活动水平及其影响因素。方法:选择常州市三级甲等综合医院心内科接受PCI治疗的冠心病病人,收集资料,分析PCI术后冠心病病人体力活动动机、体力活动和自我效能现状;冠心病病人自我效能、体力活动动机与体力活动的相关性,并分析影响PCI术后病人体力活动水平的相关危险因素。结果:共发放调查问卷400份,回收400份,有效率为94.75%(379/400);379例冠心病病人术后每周体力活动为(3570.85±314.19)MET-min,以低、中强度为主;冠心病病人术后自我效能总分、体力活动动机总分与体力活动呈正相关(P<0.05);体质指数(BMI)、PCI次数≥2次、年龄、PCI支架数量≥3枚、自我效能、体力活动动机是影响PCI术后冠心病病人体力活动水平的高危因素(OR>1且P<0.05)。结论:PCI术后病人体力活动水平处于较低的水平,PCI次数、BMI、年龄、PCI支架数量、自我效能、体力活动动机是影响PCI术后冠心病病人体力活动水平的高危因素,临床需针对各高危因素制定相应的干预措施,提高病人体力活动水平。  相似文献   
3.
4.
Gold nanoparticles (Au NPs) hold great promise in food, industrial and biomedical applications due to their unique physicochemical properties. However, influences of the gastrointestinal tract (GIT), a likely route for Au NPs administration, on the physicochemical properties of Au NPs has been rarely evaluated. Here, we investigated the influence of GIT fluids on the physicochemical properties of Au NPs (5, 50, and 100?nm) and their implications on intestinal epithelial permeability in vitro. Au NPs aggregated in fasted gastric fluids and generated hydroxyl radicals in the presence of H2O2. Cell studies showed that GIT fluids incubation of Au NPs affected the cellular uptake of Au NPs but did not induce cytotoxicity or disturb the intestinal epithelial permeability.  相似文献   
5.
BackgroundA majority of youth with Autism Spectrum Disorder (ASD) have disrupted sleep patterns, but there has been limited research examining factors associated with sleep in this population. Objective: The objective of this study was to compare demographic and lifestyle behaviors with sleep quality in youth with ASD. Methods: A total of 49 children (12.44 years; 78% male) with ASD wore the Actigraph GT9X accelerometer over seven days and nights to assess moderate to vigorous physical activity (MVPA), sedentary behavior (SB), total sleep duration, and sleep efficiency. Parents reported their child’s weekly amount of screen time and demographic information. Participants were classified according to whether they met sleep criteria for duration and efficiency (8–9 h of sleep duration and ≥85% sleep efficiency). T-tests and ANOVA were used to compare demographic and lifestyle factors between the groups. Results: Participants who meet both sleep duration and efficiency criteria had greater minutes of MVPA per day (113.65 min/day) than participants who only met sleep efficiency criteria (40.27 min/day) and participants who did not meet either sleep criteria (67.5 min/day; p < 0.0001). Additionally, participants who met both sleep criteria had fewer minutes of SB compared to those who only met sleep efficiency criteria (384.79 vs 526.05 min/day; p = 0.02). Conclusions: Youth who had indicators of good sleep quality had greater amounts of MVPA and lower amounts of SB. Studies should further examine the relationship between sleep and health behaviors in youth with ASD to determine causal mechanisms, leading to more effective sleep interventions.  相似文献   
6.
良性前列腺增生(BPH)是老年男性常见的泌尿系统疾病,其发病与前列腺慢性炎症之间存在显著相关。感染因子、尿液返流、代谢综合征、衰老过程和自身免疫应答在内的几种刺激,通过相应分子途径引起前列腺免疫细胞的组织定位和组成成分发生广泛改变,从而导致免疫系统失调,之后引发的组织损伤和缓慢愈合,导致了BPH发生和进展。本文通过总结良性前列腺增生与前列腺慢性炎症的相关性的临床研究结果,前列腺免疫细胞在病理生理机制层面与前两者之间的内在联系,以及抗炎药物对BPH-LUTS的干预作用,以其为BPH-LUTS的药物研发提供参考。  相似文献   
7.
8.
9.
ObjectiveHospitalization-associated disability [HAD, ie, the loss of ability to perform ≥1 basic activities of daily living (ADLs) independently at discharge] is a frequent condition among older patients. The present study assessed whether a simple inpatient exercise program decreases HAD incidence in acutely hospitalized very old patients.DesignIn this randomized controlled trial (Activity in Geriatric Acute Care) participants were assigned to a control or intervention group and were assessed at baseline, admission, discharge, and 3 months thereafter.Setting and ParticipantsIn total, 268 patients (mean age 88 years, range 75–102) admitted to an acute care for older patients unit of a public hospital were randomized to a control (n = 125) or intervention (exercise) group (n = 143).MethodsBoth groups received usual care, and patients in the intervention group also performed simple supervised exercises (walking and rising from a chair, for a total duration of ∼20 minutes/day). We measured ADL function (Katz index) and incident HAD at discharge and after 3 months (primary outcome) and Short Physical Performance Battery, ambulatory capacity, number of falls, rehospitalization, and death during a 3-month follow-up (secondary outcomes).ResultsMedian duration of hospitalization was 7 days (interquartile range 4 days). The intervention group had a lower risk of HAD with reference to both baseline [odds ratio (OR) 0.36; 95% confidence interval (CI) 0.17–0.76, P = .007] and admission (OR 0.29; 95% CI 0.10–0.89, P = .030). A trend toward an improved ADL function at discharge vs admission was found in the intervention group compared with controls (OR 0.32; 95% CI ‒0.04 to 0.68; P = .083). No between-group differences were noted for the other endpoints (all P > .05).Conclusion and ImplicationsA simple inpatient exercise program decreases risk of HAD in acutely hospitalized, very old patients.  相似文献   
10.
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