收费全文 | 562285篇 |
免费 | 30144篇 |
国内免费 | 616篇 |
耳鼻咽喉 | 7139篇 |
儿科学 | 19142篇 |
妇产科学 | 13176篇 |
基础医学 | 96594篇 |
口腔科学 | 13256篇 |
临床医学 | 50639篇 |
内科学 | 100924篇 |
皮肤病学 | 12819篇 |
神经病学 | 36029篇 |
特种医学 | 20809篇 |
外国民族医学 | 53篇 |
外科学 | 83294篇 |
综合类 | 8734篇 |
现状与发展 | 2篇 |
一般理论 | 122篇 |
预防医学 | 40129篇 |
眼科学 | 13072篇 |
药学 | 44888篇 |
1篇 | |
中国医学 | 1395篇 |
肿瘤学 | 30828篇 |
2021年 | 5113篇 |
2019年 | 4800篇 |
2018年 | 7011篇 |
2017年 | 5058篇 |
2016年 | 6103篇 |
2015年 | 6577篇 |
2014年 | 8923篇 |
2013年 | 12540篇 |
2012年 | 18437篇 |
2011年 | 20205篇 |
2010年 | 11640篇 |
2009年 | 10128篇 |
2008年 | 17535篇 |
2007年 | 19276篇 |
2006年 | 18635篇 |
2005年 | 17770篇 |
2004年 | 17286篇 |
2003年 | 16442篇 |
2002年 | 15764篇 |
2001年 | 23055篇 |
2000年 | 23526篇 |
1999年 | 19395篇 |
1998年 | 5456篇 |
1997年 | 4531篇 |
1996年 | 4288篇 |
1995年 | 4263篇 |
1992年 | 14669篇 |
1991年 | 16077篇 |
1990年 | 16229篇 |
1989年 | 15848篇 |
1988年 | 14522篇 |
1987年 | 14370篇 |
1986年 | 13338篇 |
1985年 | 12859篇 |
1984年 | 9520篇 |
1983年 | 8083篇 |
1982年 | 4225篇 |
1979年 | 9014篇 |
1978年 | 6423篇 |
1977年 | 5200篇 |
1976年 | 5539篇 |
1975年 | 6647篇 |
1974年 | 7456篇 |
1973年 | 7200篇 |
1972年 | 6625篇 |
1971年 | 6358篇 |
1970年 | 5932篇 |
1969年 | 5476篇 |
1968年 | 5198篇 |
1967年 | 4633篇 |
2. The CGA is administered intravenously (IV) and intranasally (IN) at the dose of 10?mg/kg. Further, its concentration in the plasma, cerebrospinal fluid (CSF) and the whole brain is analyzed by HPLC-UV method.
3. The study observes that CGA is rapidly absorbed in plasma with tmax of 1?min similar to IV route after IN administration. The peak plasma concentration and AUC0–24 are higher by 3.5 and 4.0 times respectively in IV administration, compared to IN delivery that represents the significant less systemic exposure of CGA in IN route.
4. However, the concentration of CGA in the brain is 4, 6.5, 5.3, 5.2 and 4.5 times higher at 30, 60, 120, 240 and 360?min, respectively in IN administration compared to IV administration. The exposure of CGA in the brain after IN administration (AUCbrain, IN) was significantly greater (4 times) as compared to the exposure of CGA in the brain (AUCbrain, IV) after IV administration reflecting significant brain uptake of CGA through nasal route. Therefore, IN delivery of CGA can be a promising approach for the treatment of stroke and neurodegenerative disorders. 相似文献
Hyperpolarized helium 3 magnetic resonance imaging (3He MRI) is useful for investigating pulmonary physiology of pediatric asthma, but a detailed assessment of the safety profile of this agent has not been performed in children.
ObjectiveTo evaluate the safety of 3He MRI in children and adolescents with asthma.
Materials and methodsThis was a retrospective observational study. 3He MRI was performed in 66 pediatric patients (mean age 12.9 years, range 8–18 years, 38 male, 28 female) between 2007 and 2017. Fifty-five patients received a single repeated examination and five received two repeated examinations. We assessed a total of 127 3He MRI exams. Heart rate, respiratory rate and pulse oximetry measured oxygen saturation (SpO2) were recorded before, during (2 min and 5 min after gas inhalation) and 1 h after MRI. Blood pressure was obtained before and after MRI. Any subjective symptoms were also noted. Changes in vital signs were tested for significance during the exam and divided into three subject age groups (8–12 years, 13–15 years, 16–18 years) using linear mixed-effects models.
ResultsThere were no serious adverse events, but three minor adverse events (2.3%; headache, dizziness and mild hypoxia) were reported. We found statistically significant increases in heart rate and SpO2 after 3He MRI. The youngest age group (8–12 years) had an increased heart rate and a decreased respiratory rate at 2 min and 5 min after 3H inhalation, and an increased SpO2 post MRI.
ConclusionThe use of 3He MRI is safe in children and adolescents with asthma.
相似文献Methods: [11C]WAY100635, [18F]altanserin and positron emission tomography were used to compare 5-HT1A and 5-HT2A binding in MDD patients divided into eight past suicide attempters (>4yrs prior to scanning) and eight lifetime non-attempters, and both groups were compared to eight healthy volunteers.
Results: The two receptor types differed in binding pattern across brain regions from each other, but there were no differences in binding between healthy volunteers and the two depressed groups or between depressed suicide attempters and non-attempters. No effects of depression severity or lifetime aggression were observed for either receptor.
Conclusion: Limitations of this study include small sample size and absence of high lethality suicide attempts in the depressed attempter group. No trait-like binding correlations with past suicide attempt or current depression were observed. Given the heterogeneity of nonfatal suicidal behavior, a larger sample study emphasizing higher lethality suicide attempts may find the serotonin biological phenotype seen in suicide decedents. 相似文献