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   122297篇
  免费   6772篇
  国内免费   140篇
耳鼻咽喉   1867篇
儿科学   5380篇
妇产科学   4110篇
基础医学   16956篇
口腔科学   3043篇
临床医学   9091篇
内科学   22981篇
皮肤病学   3496篇
神经病学   9502篇
特种医学   5286篇
外国民族医学   32篇
外科学   19821篇
综合类   1823篇
一般理论   37篇
预防医学   6539篇
眼科学   3458篇
药学   8615篇
中国医学   355篇
肿瘤学   6817篇
  2018年   1053篇
  2017年   878篇
  2016年   1221篇
  2015年   1339篇
  2014年   1763篇
  2013年   2618篇
  2012年   3423篇
  2011年   3519篇
  2010年   2170篇
  2009年   2097篇
  2008年   3527篇
  2007年   3791篇
  2006年   3912篇
  2005年   4004篇
  2004年   3954篇
  2003年   3789篇
  2002年   3719篇
  2001年   7201篇
  2000年   7140篇
  1999年   6009篇
  1998年   1693篇
  1997年   1605篇
  1996年   1393篇
  1995年   1261篇
  1994年   1140篇
  1993年   1169篇
  1992年   3883篇
  1991年   3700篇
  1990年   3690篇
  1989年   3476篇
  1988年   3111篇
  1987年   3027篇
  1986年   2926篇
  1985年   2730篇
  1984年   2036篇
  1983年   1673篇
  1982年   987篇
  1981年   942篇
  1980年   799篇
  1979年   1893篇
  1978年   1397篇
  1977年   1141篇
  1976年   968篇
  1975年   1222篇
  1974年   1275篇
  1973年   1263篇
  1972年   1089篇
  1971年   1026篇
  1970年   922篇
  1969年   837篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
The UK has low breastfeeding rates, with socioeconomic disparities. The Assets‐based feeding help Before and After birth (ABA) intervention was designed to be inclusive and improve infant feeding behaviours. ABA is underpinned by the behaviour change wheel and offers an assets‐based approach focusing on positive capabilities of individuals and communities, including use of a Genogram. This study aimed to investigate feasibility of intervention delivery within a randomised controlled trial (RCT). Nulliparous women ≥16 years, (n = 103) from two English sites were recruited and randomised to either intervention or usual care. The intervention – delivered through face‐to‐face, telephone and text message by trained Infant Feeding Helpers (IFHs) – ran from 30‐weeks' gestation until 5‐months postnatal. Outcomes included recruitment rates and follow‐up at 3‐days, 8‐weeks and 6‐months postnatal, with collection of future full trial outcomes via questionnaires. A mixed‐methods process evaluation included qualitative interviews with 30 women, 13 IFHs and 17 maternity providers; IFH contact logs; and fidelity checking of antenatal contact recordings. This study successfully recruited women, including teenagers, from socioeconomically disadvantaged areas; postnatal follow‐up rates were 68.0%, 85.4% and 80.6% at 3‐days, 8‐weeks and 6‐months respectively. Breastfeeding at 8‐weeks was obtained for 95.1% using routine data for non‐responders. It was possible to recruit and train peer supporters to deliver the intervention with adequate fidelity. The ABA intervention was acceptable to women, IFHs and maternity services. There was minimal contamination and no evidence of intervention‐related harm. In conclusion, the intervention is feasible to deliver within an RCT, and a definitive trial required.  相似文献   
3.
4.
With easy chemical synthesis from its precursor, methamphetamine (MA) is now widespread in many countries. The abuse of methamphetamine is associated with several negative effects on health, because MA is a neurotoxin and a dangerous central nervous system stimulant. It changes levels of neurotransmitters in the brain, releasing dopamine and inhibiting nor epinephrine uptake which increases sympathetic nervous system activity and can lead to cardiac arrhythmia, hypertension and tachypnea. The consequences of MA abuse are clearly manifested in oral diseases (like “meth mouth”) which is characterised by extensive caries, teeth grinding with ensuing dental wear and trismus. The present review was designed to fill the gap in knowledge about methamphetamine abuse in the European Union (EU) and to illustrate the main clinical effects of prolonged use. After describing the pharmacology and systemic effects of methamphetamine and concentrating on its effects on the mouth, the present review compares the epidemiology and incidence of abuse in the world, particularly the USA and the EU. Key words:Methamphetamine, “Meth mouth”, drug abuse, oral health.  相似文献   
5.
Prevalence of osteoporosis is more than 50% in older adults, yet current clinical methods for diagnosis that rely on areal bone mineral density (aBMD) fail to detect most individuals who have a fragility fracture. Bone fragility can manifest in different forms, and a “one-size-fits-all” approach to diagnosis and management of osteoporosis may not be suitable. High-resolution peripheral quantitative computed tomography (HR-pQCT) provides additive information by capturing information about volumetric density and microarchitecture, but interpretation is challenging because of the complex interactions between the numerous properties measured. In this study, we propose that there are common combinations of bone properties, referred to as phenotypes, that are predisposed to different levels of fracture risk. Using HR-pQCT data from a multinational cohort (n = 5873, 71% female) between 40 and 96 years of age, we employed fuzzy c-means clustering, an unsupervised machine-learning method, to identify phenotypes of bone microarchitecture. Three clusters were identified, and using partial correlation analysis of HR-pQCT parameters, we characterized the clusters as low density, low volume, and healthy bone phenotypes. Most males were associated with the healthy bone phenotype, whereas females were more often associated with the low volume or low density bone phenotypes. Each phenotype had a significantly different cumulative hazard of major osteoporotic fracture (MOF) and of any incident osteoporotic fracture (p < 0.05). After adjustment for covariates (cohort, sex, and age), the low density followed by the low volume phenotype had the highest association with MOF (hazard ratio = 2.96 and 2.35, respectively), and significant associations were maintained when additionally adjusted for femoral neck aBMD (hazard ratio = 1.69 and 1.90, respectively). Further, within each phenotype, different imaging biomarkers of fracture were identified. These findings suggest that osteoporotic fracture risk is associated with bone phenotypes that capture key features of bone deterioration that are not distinguishable by aBMD. © 2021 American Society for Bone and Mineral Research (ASBMR).  相似文献   
6.
7.
8.
9.
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