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   18514篇
  免费   1198篇
  国内免费   102篇
耳鼻咽喉   154篇
儿科学   577篇
妇产科学   416篇
基础医学   2682篇
口腔科学   650篇
临床医学   1574篇
内科学   4415篇
皮肤病学   589篇
神经病学   1823篇
特种医学   440篇
外科学   1706篇
综合类   48篇
一般理论   7篇
预防医学   1625篇
眼科学   312篇
药学   1427篇
中国医学   72篇
肿瘤学   1297篇
  2024年   25篇
  2023年   238篇
  2022年   593篇
  2021年   999篇
  2020年   507篇
  2019年   746篇
  2018年   829篇
  2017年   502篇
  2016年   606篇
  2015年   676篇
  2014年   892篇
  2013年   1103篇
  2012年   1622篇
  2011年   1581篇
  2010年   920篇
  2009年   721篇
  2008年   1126篇
  2007年   1125篇
  2006年   953篇
  2005年   873篇
  2004年   722篇
  2003年   662篇
  2002年   601篇
  2001年   127篇
  2000年   119篇
  1999年   124篇
  1998年   96篇
  1997年   96篇
  1996年   58篇
  1995年   39篇
  1994年   40篇
  1993年   36篇
  1992年   50篇
  1991年   37篇
  1990年   33篇
  1989年   15篇
  1988年   27篇
  1987年   22篇
  1986年   26篇
  1985年   24篇
  1984年   23篇
  1983年   22篇
  1982年   11篇
  1981年   13篇
  1980年   11篇
  1977年   16篇
  1975年   9篇
  1974年   13篇
  1972年   9篇
  1971年   10篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Noroviruses are associated with one fifth of diarrheal illnesses globally and are not yet preventable with vaccines. Little is known about the effects of norovirus infection on infant gut microbiome health, which has a demonstrated role in protecting hosts from pathogens and a possible role in oral vaccine performance. In this study, we characterized infant gut microbiome changes occurring with norovirus-associated acute gastroenteritis (AGE) and the extent of recovery. Metagenomic sequencing was performed on the stools of five infants participating in a longitudinal birth cohort study conducted in León, Nicaragua. Taxonomic and functional diversities of gut microbiomes were profiled at time points before, during, and after norovirus infection. Initially, the gut microbiomes resembled those of breastfeeding infants, rich in probiotic species. When disturbed by AGE, Gammaproteobacteria dominated, particularly Pseudomonas species. Alpha diversity increased but the genes involved in carbohydrate metabolism and glycan biosynthesis decreased. After the symptoms subsided, the gut microbiomes rebounded with their taxonomic and functional communities resembling those of the pre-infection microbiomes. In this study, during disruptive norovirus-associated AGE, the gut microbiome was temporarily altered, returning to a pre-infection composition a median of 58 days later. Our study provides new insights for developing probiotic treatments and furthering our understanding of the role that episodes of AGE have in shaping the infant gut microbiome, their long-term outcomes, and implications for oral vaccine effectiveness.  相似文献   
102.
BackgroundAdequate treatment of arterial hypertension and achieving arterial hypertension goals in are important in reducing cardiovascular outcomes.ObjectivesTo describe angiotensin receptor blockers in monotherapy or double combination therapy and the rate of arterial hypertension control.MethodsThis cross-sectional study evaluated patients who were using angiotensin receptor blockers between 2017 and 2020. Those using three or more antihypertensive drugs were excluded. The analyzed variables included sex, age, body mass index, valid home blood pressure monitoring (HBPM) measurements, casual and HBPM systolic and diastolic blood pressure measurements, blood pressure variability, and antihypertensive and angiotensin receptor blocker class. Paired t, chi-square, and Fisher’s exact tests were used, as well as overlapping 95% confidence intervals and a significance level of 5% (p < 0.05).ResultsOf 17,013 patients, 12,813 met the inclusion criteria, 62.1% of whom were female. The mean number of valid measurements was 23.3 (SD, 2.0). The mean HBPM and casual measurements for systolic blood pressure were 126.8 (SD, 15.8) mmHg and 133.5 (SD, 20.1) mmHg (p <0.001), respectively, while those for diastolic blood pressure were 79.1 (SD, 9.7 mmHg) and 83.6 (SD, 11.9) mmHg (p <0.001), respectively. Losartan was the most common angiotensin receptor blocker and resulted in the highest blood pressure values. Combinations of angiotensin receptor blockers with diuretics or calcium channel antagonists resulted in lower blood pressure values.ConclusionsMore than half of the patients used losartan, although it was the least efficient drug for reducing and controlling blood pressure.  相似文献   
103.
Patients with liver cirrhosis may present hepatic encephalopathy with a wide range of neurological disturbances and alterations in sleep quality and in the sleep‐wake circadian rhythm. Hyperammonemia is a main contributor to the neurological alterations in hepatic encephalopathy. We have assessed, in an animal model of chronic hyperammonemia without liver failure, the effects of hyperammonemia per se on the circadian rhythms of motor activity, temperature, and plasma levels of adrenal corticosteroid hormones. Chronic hyperammonemia alters the circadian rhythms of locomotor activity and of cortisol and corticosterone levels in blood. Different types of motor activity are affected differentially. Hyperammonemia significantly alters the rhythm of spontaneous ambulatory activity, reducing strongly ambulatory counts and slightly average velocity during the night (the active phase) but not during the day, resulting in altered circadian rhythms. In contrast, hyperammonemia did not affect wheel running at all, indicating that it affects spontaneous but not voluntary activity. Vertical activity was affected only very slightly, indicating that hyperammonemia does not induce anxiety. Hyperammonemia abolished completely the circadian rhythm of corticosteroid hormones in plasma, completely eliminating the peaks of cortisol and corticosterone present in control rats at the start of the dark period. The data reported show that chronic hyperammonemia, similar to that present in patients with liver cirrhosis, alters the circadian rhythms of corticosteroid hormones and of motor activity. This suggests that hyperammonemia would be a relevant contributor to the alterations in corticosteroid hormones and in circadian rhythms in patients with liver cirrhosis. © 2009 Wiley‐Liss, Inc.  相似文献   
104.
Guarana (Paullinia cupana) is a widely consumed nutraceutical with various health benefits supported by scientific evidence. However, its indirect health impacts through the gut microbiota have not been studied. Caenorhabditis elegans is a useful model to study both the direct and indirect effects of nutraceuticals, as the intimate association of the worm with the metabolites produced by Escherichia coli is a prototypic simplified model of our gut microbiota. We prepared an ethanoic extract of guarana seeds and assessed its antioxidant capacity in vitro, with a 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, and in vivo, utilizing C. elegans. Additionally, we studied the impact of this extract on C. elegans lifespan, utilizing both viable and non-viable E. coli, and assessed the impact of guarana on E. coli folate production. The extract showed high antioxidant capacity, and it extended worm lifespan. However, the antioxidant and life-extending effects did not correlate in terms of the extract concentration. The extract-induced life extension was also less significant when utilizing dead E. coli, which may indicate that the effects of guarana on the worms work partly through modifications on E. coli metabolism. Following this observation, guarana was found to decrease E. coli folate production, revealing one possible route for its beneficial effects.  相似文献   
105.
106.
107.
108.
109.
110.
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