全文获取类型
收费全文 | 2350398篇 |
免费 | 171243篇 |
国内免费 | 3331篇 |
专业分类
耳鼻咽喉 | 32053篇 |
儿科学 | 75894篇 |
妇产科学 | 62685篇 |
基础医学 | 348182篇 |
口腔科学 | 63636篇 |
临床医学 | 211353篇 |
内科学 | 457291篇 |
皮肤病学 | 51727篇 |
神经病学 | 185393篇 |
特种医学 | 88039篇 |
外国民族医学 | 489篇 |
外科学 | 353874篇 |
综合类 | 47510篇 |
现状与发展 | 12篇 |
一般理论 | 848篇 |
预防医学 | 182742篇 |
眼科学 | 54325篇 |
药学 | 175107篇 |
11篇 | |
中国医学 | 4575篇 |
肿瘤学 | 129226篇 |
出版年
2021年 | 18982篇 |
2019年 | 19539篇 |
2018年 | 27066篇 |
2017年 | 20364篇 |
2016年 | 22757篇 |
2015年 | 25645篇 |
2014年 | 36108篇 |
2013年 | 53968篇 |
2012年 | 74692篇 |
2011年 | 79426篇 |
2010年 | 47068篇 |
2009年 | 44573篇 |
2008年 | 74620篇 |
2007年 | 79485篇 |
2006年 | 80310篇 |
2005年 | 77792篇 |
2004年 | 74379篇 |
2003年 | 71700篇 |
2002年 | 69373篇 |
2001年 | 108744篇 |
2000年 | 111457篇 |
1999年 | 93499篇 |
1998年 | 26992篇 |
1997年 | 23661篇 |
1996年 | 24056篇 |
1995年 | 22719篇 |
1994年 | 20895篇 |
1993年 | 19713篇 |
1992年 | 72004篇 |
1991年 | 70069篇 |
1990年 | 68391篇 |
1989年 | 65665篇 |
1988年 | 60302篇 |
1987年 | 59125篇 |
1986年 | 55218篇 |
1985年 | 53004篇 |
1984年 | 39311篇 |
1983年 | 33396篇 |
1982年 | 19858篇 |
1979年 | 35866篇 |
1978年 | 25651篇 |
1977年 | 21230篇 |
1976年 | 20332篇 |
1975年 | 21816篇 |
1974年 | 26148篇 |
1973年 | 24802篇 |
1972年 | 23201篇 |
1971年 | 22037篇 |
1970年 | 20247篇 |
1969年 | 19315篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Ingmar Fleps Pierre Guy Stephen J Ferguson Peter A Cripton Benedikt Helgason 《Journal of bone and mineral research》2019,34(10):1837-1850
The majority of hip fractures in the elderly are the result of a fall from standing or from a lower height. Current injury models focus mostly on femur strength while neglecting subject-specific loading. This article presents an injury modeling strategy for hip fractures related to sideways falls that takes subject-specific impact loading into account. Finite element models (FEMs) of the human body were used to predict the experienced load and the femoral strength in a single model. We validated these models for their predicted peak force, effective pelvic stiffness, and fracture status against matching ex vivo sideways fall impacts (n = 11) with a trochanter velocity of 3.1 m/s. Furthermore, they were compared to sideways impacts of volunteers with lower impact velocities that were previously conducted by other groups. Good agreement was found between the ex vivo experiments and the FEMs with respect to peak force (root mean square error [RMSE] = 10.7%, R2 = 0.85) and effective pelvic stiffness (R2 = 0.92, RMSE = 12.9%). The FEMs were predictive of the fracture status for 10 out of 11 specimens. Compared to the volunteer experiments from low height, the FEMs overestimated the peak force by 25% for low BMI subjects and 8% for high BMI subjects. The effective pelvic stiffness values that were derived from the FEMs were comparable to those derived from impacts with volunteers. The force attenuation from the impact surface to the femur ranged between 27% and 54% and was highly dependent on soft tissue thickness (R2 = 0.86). The energy balance in the FEMS showed that at the time of peak force 79% to 93% of the total energy is either kinetic or was transformed to soft tissue deformation. The presented FEMs allow for direct discrimination between fracture and nonfracture outcome for sideways falls and bridge the gap between impact testing with volunteers and impact conditions representative of real life falls. © 2019 American Society for Bone and Mineral Research. 相似文献
22.
23.
Elizabeth D. Krebs Robert B. Hawkins J. Hunter Mehaffey Clifford E. Fonner Alan M. Speir Mohammed A. Quader Jeffrey B. Rich Leora T. Yarboro Nicholas R. Teman Gorav Ailawadi 《The Journal of thoracic and cardiovascular surgery》2019,157(4):1533-1542.e2
Objectives
Expedient extubation after cardiac surgery has been associated with improved outcomes, leading to postoperative extubation frequently during overnight hours. However, recent evidence in a mixed medical-surgical intensive care unit population demonstrated worse outcomes with overnight extubation. This study investigated the impact of overnight extubation in a statewide, multicenter Society of Thoracic Surgeons database.Methods
Records from 39,812 patients undergoing coronary artery bypass grafting or valve operations (2008-2016) and extubated within 24 hours were stratified according to extubation time between 06:00 and 18:00 (day) or between 18:00 and 6:00 (overnight). Outcomes including reintubation, mortality, and composite morbidity-mortality were evaluated using hierarchical regression models adjusted for Society of Thoracic Surgeons predictive risk scores. To further analyze extubation during the night, a subanalysis stratified patients into 3 groups: 06:00 to 18:00, 18:00 to 24:00, and 24:00 to 06:00.Results
A total of 20,758 patients were extubated overnight (52.1%) and were slightly older (median age 66 vs 65 years, P < .001) with a longer duration of ventilation (4 vs 7 hours, P < .001). Day and overnight extubation were associated with equivalent operative mortality (1.7% vs 1.7%, P = .880), reintubation (3.7% vs 3.4%, P = .141), and composite morbidity-mortality (8.2% vs 8.0%, P = .314). After risk adjustment, overnight extubation was not associated with any difference in reintubation, mortality, or composite morbidity-mortality. On subanalysis, those extubated between 24:00 and 06:00 exhibited increased composite morbidity-mortality (odds ratio, 1.18; P = .001) but no difference in reintubation or mortality.Conclusions
Extubation overnight was not associated with increased mortality or reintubation. These results suggest that in the appropriate clinical setting, it is safe to routinely extubate cardiac surgery patients overnight. 相似文献24.
B Maybury A Powell-Chandler N Kumar 《Annals of the Royal College of Surgeons of England》2015,97(3):e37-e38
We report two British cases of liver abscess, due to Klebsiella pneumoniae and associated with synchronous infection elsewhere, which required liver resection for definitive treatment. They illustrate the geographic spread of aggressive K pneumoniae liver infection and demonstrate the importance of early aggressive treatment. 相似文献
25.
P. A. Hannan J. A. Khan A. Khan S. Safiullah 《Indian journal of pharmaceutical sciences》2016,78(1):2-7
Dosage form is a mean used for the delivery of drug to a living body. In order to get the desired effect the drug should be delivered to its site of action at such rate and concentration to achieve the maximum therapeutic effect and minimum adverse effect. Since oral route is still widely accepted route but having a common drawback of difficulty in swallowing of tablets and capsules. Therefore a lot of research has been done on novel drug delivery systems. This review is about oral dispersible tablets a novel approach in drug delivery systems that are now a day''s more focused in formulation world, and laid a new path that, helped the patients to build their compliance level with the therapy, also reduced the cost and ease the administration especially in case of pediatrics and geriatrics. Quick absorption, rapid onset of action and reduction in drug loss properties are the basic advantages of this dosage form. 相似文献
26.
27.
James A. Akingbasote Alison J. Foster Ian Wilson Sunil Sarda Huw B. Jones J. Gerry Kenna 《Archives of toxicology》2016,90(4):853-862
Hepatic NADPH-cytochrome P450 oxidoreductase null (HRN?) mice exhibit normal hepatic and extrahepatic biotransformation enzyme activities when compared to wild-type (WT) mice, but express no functional hepatic cytochrome P450 activities. When incubated in vitro with [14C]-diclofenac, liver microsomes from WT mice exhibited extensive biotransformation to oxidative and glucuronide metabolites and covalent binding to proteins was also observed. In contrast, whereas glucuronide conjugates and a quinone-imine metabolite were formed when [14C]-diclofenac was incubated with HRN? mouse liver, only small quantities of P450-derived oxidative metabolites were produced in these samples and covalent binding to proteins was not observed. Livers from vehicle-treated HRN? mice exhibited enhanced lipid accumulation, bile duct proliferation, hepatocellular degeneration and necrosis and inflammatory cell infiltration, which were not present in livers from WT mice. Elevated liver-derived alanine aminotransferase, glutamate dehydrogenase and alkaline phosphatase activities were also observed in plasma from HRN? mice. When treated orally with diclofenac for 7 days, at 30 mg/kg/day, the severities of the abnormal liver histopathology and plasma liver enzyme findings in HRN? mice were reduced markedly. Oral diclofenac administration did not alter the liver histopathology or elevate plasma enzyme activities of WT mice. These findings indicate that HRN? mice are valuable for exploration of the role played by hepatic P450s in drug biotransformation, but poorly suited to investigations of drug-induced liver toxicity. Nevertheless, studies in HRN? mice could provide novel insights into the role played by inflammation in liver injury and may aid the evaluation of new strategies for its treatment. 相似文献
28.
29.
30.