全文获取类型
收费全文 | 6313篇 |
免费 | 766篇 |
国内免费 | 144篇 |
专业分类
耳鼻咽喉 | 42篇 |
儿科学 | 79篇 |
妇产科学 | 88篇 |
基础医学 | 876篇 |
口腔科学 | 103篇 |
临床医学 | 1094篇 |
内科学 | 437篇 |
皮肤病学 | 16篇 |
神经病学 | 434篇 |
特种医学 | 387篇 |
外科学 | 326篇 |
综合类 | 954篇 |
现状与发展 | 1篇 |
一般理论 | 4篇 |
预防医学 | 1200篇 |
眼科学 | 257篇 |
药学 | 377篇 |
9篇 | |
中国医学 | 446篇 |
肿瘤学 | 93篇 |
出版年
2024年 | 9篇 |
2023年 | 102篇 |
2022年 | 112篇 |
2021年 | 248篇 |
2020年 | 263篇 |
2019年 | 226篇 |
2018年 | 204篇 |
2017年 | 250篇 |
2016年 | 236篇 |
2015年 | 272篇 |
2014年 | 410篇 |
2013年 | 738篇 |
2012年 | 366篇 |
2011年 | 369篇 |
2010年 | 302篇 |
2009年 | 252篇 |
2008年 | 313篇 |
2007年 | 297篇 |
2006年 | 302篇 |
2005年 | 202篇 |
2004年 | 231篇 |
2003年 | 191篇 |
2002年 | 182篇 |
2001年 | 175篇 |
2000年 | 134篇 |
1999年 | 101篇 |
1998年 | 79篇 |
1997年 | 81篇 |
1996年 | 75篇 |
1995年 | 69篇 |
1994年 | 43篇 |
1993年 | 37篇 |
1992年 | 55篇 |
1991年 | 26篇 |
1990年 | 39篇 |
1989年 | 32篇 |
1988年 | 17篇 |
1987年 | 23篇 |
1986年 | 19篇 |
1985年 | 27篇 |
1984年 | 20篇 |
1983年 | 19篇 |
1982年 | 9篇 |
1981年 | 17篇 |
1980年 | 15篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1976年 | 8篇 |
1974年 | 2篇 |
排序方式: 共有7223条查询结果,搜索用时 15 毫秒
11.
12.
Mehdi Kordi Jonathan Folland Stuart Goodall Nicos Haralabidis Tom Maden-Wilkinson Tejal Sarika Patel Jonathan Leeder Paul Barratt Glyn Howatson 《Scandinavian journal of medicine & science in sports》2020,30(2):227-237
Mechanical peak power output (PPO) is a determinant of performance in sprint cycling. The purpose of this study was to examine the relationship between PPO and putative physiological determinants of PPO in elite cyclists, and to compare sprint performance between elite sprint and endurance cyclists. Thirty-five elite cyclists (18 endurance; 17 sprint) performed duplicate sprint cycling laboratory tests to establish PPO and its mechanical components. Quadriceps femoris (QVOL) and hamstring muscle volume (HAMVOL) were assessed with MRI, vastus lateralis pennation angle (PθVL) and fascicle length (FLVL) were determined with ultrasound imaging, and neuromuscular activation of three muscles was assessed using EMG at PPO during sprint cycling. For the whole cohort, there was a wide variability in PPO (range 775-2025 W) with very large, positive, bivariate relationships between PPO and QVOL (r = .87), HAMVOL (r = .71), and PθVL (r = .81). Step-wise multiple regression analysis revealed that 87% of the variability in PPO between cyclists was explained by two variables QVOL (76%) and PθVL (11%). The sprint cyclists had greater PPO (+61%; P < .001 vs endurance), larger QVOL (P < .001), and BFVOL (P < .001) as well as more pennate vastus lateralis muscles (P < .001). These findings emphasize the importance of quadriceps muscle morphology for sprint cycling events. 相似文献
13.
14.
15.
Shaoying Liu Qian Yu Md Mahbub Hossain Scott Doig Ran Bao Yaping Zhao Jin Yan Xun Luo Jiaxuan Yang Arthur F. Kramer Liye Zou 《International Journal of Mental Health Promotion, The》2022,24(1):13-24
This research is designed to investigate the relationship between the 24-h movement guidelines (24-HMG) and
self-reported academic achievement (AA) using nationally representative data derived from the 2019 U.S.
National Youth Risk Behaviour Survey. A multiple-stage cluster sampling procedure has been adopted to ensure
a representative sample (N = 9127 adolescents; mean age = 15.7 years old; male% = 49.8%). Logistic regression
has been adopted to obtain the odds ratio (OR) regarding the associations between adherence to 24-HMG and AA
while controlling for ethnicity, body mass index, sex and age. The prevalence of meeting the 24-h movement
guidelines in isolation and combination varied greatly (physical activity = 23.3%, screen time = 32.5%,
sleep = 22.3%, and 24-HMG = 2.8%), while the percentage of highest-class AA was 42.5%. Compared with the
situation when none of 24-HMG is met, the achievement of any of the combined guidelines (except for meeting
the physical activity guidelines) was significantly associated with higher odds of achieving first-class AA. Meeting
the sleep guideline had 1.42 times increased likelihood to achieve highest-class AA as compared with not meeting
the sleep guideline. Meeting screen time guidelines and physical activity guidelines, respectively, were 1.32 and
1.13 times more likely to report first-class AA; but meeting the guidelines of physical activity was not significantly
related to AA. Meeting the 24-HMG had the highest odds of achieving first-class AA (OR = 2.01, 95%CI: 1.47–
2.73). In both sexes, adolescents who met 24-HMG self-reported better AA (boys OR = 2.05, 95%CI: 1.34–3.15;
girls OR = 2.26, 95%CI: 1.36–3.76). Significant relationships were observed in adolescents from 9–10th grade, but
not higher grades. Our research findings suggest that optimal movement behaviours can be seen as an important
This work is licensed under a Creative Commons Attribution 4.0 International License, which
permits unrestricted use, distribution, and reproduction in any medium, provided the original
work is properly cited.
DOI: 10.32604/IJMHP.2021.017660
ARTICLE
Tech Science Press
Published Online: 26 October 2021
element to better academic achievement among U.S. adolescents. Future studies can adopt our discoveries to promote adolescents’ academic achievement through implementing optimal 24-h movement behaviour patterns. 相似文献
16.
Yongqiang Tang 《Statistics in medicine》2020,39(24):3427-3457
In a series of articles, Gart and Nam construct the efficient score tests and confidence intervals with or without skewness correction for stratified comparisons of binomial proportions on the risk difference, relative risk, and odds ratio effect metrics. However, the stratified score methods and their properties are not well understood. We rederive the efficient score tests, which reveals their theoretical relationship with the contrast-based score tests, and provides a basis for adapting the method by using other weighting schemes. The inverse variance weight is optimal for a common treatment effect in large samples. We explore the behavior of the score approach in the presence of extreme outcomes when either no or all subjects in some strata are responders, and provide guidance on the choice of weights in the analysis of rare events. The score method is recommended for studies with a small number of moderate or large sized strata. A general framework is proposed to calculate the asymptotic power and sample size for the score test in superiority, noninferiority and equivalence clinical trials, or case-control studies. We also describe a nearly exact procedure that underestimates the exact power, but the degree of underestimation can be controlled to a negligible level. The proposed methods are illustrated by numerical examples. 相似文献
17.
目的 总结脑血管疾病后Holmes震颤的临床、影像和电生理特点。
方法 回顾性分析2015年8月-2019年8月就诊于首都医科大学附属北京天坛医院的4例脑血管疾病
所致Holmes震颤患者,对其临床、影像及电生理资料进行分析总结。
结果 4例患者中2例由高血压性脑出血引起,另外2例分别由脑动静脉畸形和脑海绵状血管瘤破裂
出血引起。Holmes震颤出现于原发病后1~24个月,表现为病灶对侧肢体震颤,以上肢多见。头颅MRI
检查显示2例患者病灶仅累及丘脑,2例同时累及丘脑和中脑。震颤分析显示静止、姿势、意向及持物
1000 g几种状态下震颤的峰频率均在2.6~3.8 Hz,意向状态震颤半宽功率高于静止状态。主动肌与
拮抗肌在静息时以同步收缩为主,姿势、意向和持物时以交替收缩为主。3例接受普拉克索治疗均有
不同程度缓解。
结论 Holmes震颤多由累及中脑、丘脑部位脑血管疾病引起,表现为2~4 Hz低频震颤,意向状态震
颤明显,部分患者多巴胺受体激动剂治疗有效。 相似文献
18.
19.
When living organisms become sick as a result of a bacterial infection, a suite of brain-mediated responses occur, including fever, anorexia and sleepiness. Systemic administration of lipopolysaccharide (LPS), a common constituent of bacterial cell walls, increases body temperature and non-rapid eye movement (NREM) sleep in animals and induces the production of pro-inflammatory prostaglandins (PGs). PGE2 is the principal mediator of fever, and both PGE2 and PGD2 regulate sleep–wake behavior. The extent to which PGE2 and PGD2 are involved in the effect of LPS on NREM sleep remains to be clarified. Therefore, we examined LPS-induced changes in body temperature and NREM sleep in mice with nervous system-specific knockouts (KO) for the PGE2 receptors type EP3 or EP4, in mice with total body KO of microsomal PGE synthase-1 or the PGD2 receptor type DP, and in mice treated with the cyclooxygenase (COX) inhibitor meloxicam. We observed that LPS-induced NREM sleep was slightly attenuated in mice lacking EP4 receptors in the nervous system, but was not affected in any of the other KO mice or in mice pretreated with the COX inhibitor. These results suggest that the effect of LPS on NREM sleep is partially dependent on PGs and is likely mediated mainly by other pro-inflammatory substances. In addition, our data show that the main effect of LPS on body temperature is hypothermia in the absence of nervous system EP3 receptors or in the presence of a COX inhibitor. 相似文献
20.
研究生科学道德和学风建设是学位与研究生教育的重要组成部分。针对近年来科学研究和学术活动中各种违背科学道德和学术规范的行为时有发生,国家教育部对研究生科学道德和学风建设日益重视,因此构建研究生的科学道德和学风教育质量管理体系具有十分重要的意义。实现研究生科学道德和学风教育质量体系的方针和目标需具备三个要素,即教育实践的模式(集主题教育、方法学习、学术实践三位一体)、有效性评价机制和绩效考核机制。此外,尚需建立体系优化机制,以适应各种内外部因素的变化,保持体系的更新和优化。 相似文献