全文获取类型
收费全文 | 8293篇 |
免费 | 466篇 |
国内免费 | 41篇 |
专业分类
耳鼻咽喉 | 90篇 |
儿科学 | 305篇 |
妇产科学 | 270篇 |
基础医学 | 779篇 |
口腔科学 | 285篇 |
临床医学 | 794篇 |
内科学 | 1914篇 |
皮肤病学 | 244篇 |
神经病学 | 627篇 |
特种医学 | 306篇 |
外科学 | 1460篇 |
综合类 | 107篇 |
一般理论 | 7篇 |
预防医学 | 462篇 |
眼科学 | 199篇 |
药学 | 463篇 |
中国医学 | 36篇 |
肿瘤学 | 452篇 |
出版年
2024年 | 12篇 |
2023年 | 107篇 |
2022年 | 183篇 |
2021年 | 395篇 |
2020年 | 257篇 |
2019年 | 353篇 |
2018年 | 340篇 |
2017年 | 252篇 |
2016年 | 266篇 |
2015年 | 270篇 |
2014年 | 386篇 |
2013年 | 409篇 |
2012年 | 718篇 |
2011年 | 701篇 |
2010年 | 406篇 |
2009年 | 349篇 |
2008年 | 503篇 |
2007年 | 518篇 |
2006年 | 420篇 |
2005年 | 382篇 |
2004年 | 325篇 |
2003年 | 300篇 |
2002年 | 253篇 |
2001年 | 81篇 |
2000年 | 67篇 |
1999年 | 65篇 |
1998年 | 37篇 |
1997年 | 41篇 |
1996年 | 35篇 |
1995年 | 24篇 |
1994年 | 18篇 |
1993年 | 27篇 |
1992年 | 21篇 |
1991年 | 28篇 |
1990年 | 28篇 |
1989年 | 14篇 |
1988年 | 23篇 |
1987年 | 19篇 |
1986年 | 16篇 |
1985年 | 26篇 |
1984年 | 24篇 |
1983年 | 15篇 |
1982年 | 10篇 |
1981年 | 11篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1974年 | 7篇 |
1973年 | 5篇 |
排序方式: 共有8800条查询结果,搜索用时 15 毫秒
71.
Rodriguez-Porcel M Lerman A Herrmann J Schwartz RS Sawamura T Condorelli M Napoli C Lerman LO 《Cardiovascular research》2003,58(1):213-221
OBJECTIVE: Hypercholesterolemia (HC) and hypertension (HT) are both major risk factors for the development and progression of atherosclerotic heart disease, and their co-existence has been associated with an increased incidence of cardiac events in clinical studies. HC and HT are individually associated with abnormal myocardial vascular function, but whether HT exacerbates the HC-induced myocardial vascular dysfunction remains unclear. METHODS: We studied in pigs the effect of renovascular HT superimposed on diet-induced HC (HC+HT) on myocardial perfusion and microvascular permeability in vivo (using electron-beam computed tomography) in response to cardiac challenge (i.v. adenosine and dobutamine). The involvement of systemic and myocardial tissue oxidative stress in vitro was assessed by oxidizability of LDL, levels of endogenous antioxidants, and tissue activities of radical-scavenger systems. RESULTS: While in normal animals myocardial perfusion increased in response to i.v. adenosine (+36+/-13%, P<0.05), in HC and HT alone the increase was blunted. In HC+HT myocardial perfusion response was further attenuated and significantly lower than normal, and myocardial vascular resistance failed to decrease (+7.6+/-8.8 vs. -21.0+/-5.8%, P=0.02 versus normal). HC+HT also showed blunted response to dobutamine, and augmented increases in microvascular permeability in vivo. These functional abnormalities were associated with increased systemic and myocardial tissue oxidative stress compared to HC or HT alone, and a synergistic decrease in endogenous antioxidant defenses in myocardial tissue. Furthermore, chronic antioxidant vitamin supplementation in combined HC and HT improved myocardial vascular responses. CONCLUSION: HT amplifies the HC-induced myocardial microvascular dysfunction in vivo and increased oxidative stress in vitro. These alterations may potentially play a role in the increased incidence of cardiac events observed when HC and HT co-exist. 相似文献
72.
Treatment of neuroblastoma in congenital central hypoventilation syndrome with a PHOX2B polyalanine repeat expansion mutation: New twist on a neurocristopathy syndrome 下载免费PDF全文
73.
Radiologic resolution of malignant infantile osteopetrosis skeletal changes following hematopoietic stem cell transplantation 下载免费PDF全文
74.
Amir H. Abdi Alan G. Hannam Sidney Fels 《International journal of computer assisted radiology and surgery》2018,13(7):1109-1115
Purpose
Magnetic resonance imaging (MRI) is widely used in study of maxillofacial structures. While MRI is the modality of choice for soft tissues, it fails to capture hard tissues such as bone and teeth. Virtual dental models, acquired by optical 3D scanners, are becoming more accessible for dental practice and are starting to replace the conventional dental impressions. The goal of this research is to fuse the high-resolution 3D dental models with MRI to enhance the value of imaging for applications where detailed analysis of maxillofacial structures are needed such as patient examination, surgical planning, and modeling.Methods
A subject-specific dental attachment was digitally designed and 3D printed based on the subject’s face width and dental anatomy. The attachment contained 19 semi-ellipsoidal concavities in predetermined positions where oil-based ellipsoidal fiducial markers were later placed. The MRI was acquired while the subject bit on the dental attachment. The spatial position of the center of mass of each fiducial in the resultant MR Image was calculated by averaging its voxels’ spatial coordinates. The rigid transformation to fuse dental models to MRI was calculated based on the least squares mapping of corresponding fiducials and solved via singular-value decomposition.Results
The target registration error (TRE) of the proposed fusion process, calculated in a leave-one-fiducial-out fashion, was estimated at 0.49 mm. The results suggest that 6–9 fiducials suffice to achieve a TRE of equal to half the MRI voxel size.Conclusion
Ellipsoidal oil-based fiducials produce distinguishable intensities in MRI and can be used as registration fiducials. The achieved accuracy of the proposed approach is sufficient to leverage the merged 3D dental models with the MRI data for a finer analysis of the maxillofacial structures where complete geometry models are needed.75.
Biomaterial characterization of off‐the‐shelf decellularized porcine pericardial tissue for use in prosthetic valvular applications 下载免费PDF全文
Joshua A. Choe Soumen Jana Brandon J. Tefft Ryan S. Hennessy Jason Go David Morse Amir Lerman Melissa D. Young 《Journal of tissue engineering and regenerative medicine》2018,12(7):1608-1620
Fixed pericardial tissue is commonly used for commercially available xenograft valve implants, and has proven durability, but lacks the capability to remodel and grow. Decellularized porcine pericardial tissue has the promise to outperform fixed tissue and remodel, but the decellularization process has been shown to damage the collagen structure and reduce mechanical integrity of the tissue. Therefore, a comparison of uniaxial tensile properties was performed on decellularized, decellularized‐sterilized, fixed, and native porcine pericardial tissue versus native valve leaflet cusps. The results of non‐parametric analysis showed statistically significant differences (p < .05) between the stiffness of decellularized versus native pericardium and native cusps as well as fixed tissue, respectively; however, decellularized tissue showed large increases in elastic properties. Porosity testing of the tissues showed no statistical difference between decellularized and decell‐sterilized tissue compared with native cusps (p > .05). Scanning electron microscopy confirmed that valvular endothelial and interstitial cells colonized the decellularized pericardial surface when seeded and grown for 30 days in static culture. Collagen assays and transmission electron microscopy analysis showed limited reductions in collagen with processing; yet glycosaminoglycan assays showed great reductions in the processed pericardium relative to native cusps. Decellularized pericardium had comparatively low mechanical properties among the groups studied; yet the stiffness was comparatively similar to the native cusps and demonstrated a lack of cytotoxicity. Suture retention, accelerated wear, and hydrodynamic testing of prototype decellularized and decell‐sterilized valves showed positive functionality. Sterilized tissue could mimic valvular mechanical environment in vitro, therefore making it a viable potential candidate for off‐the‐shelf tissue‐engineered valvular applications. 相似文献
76.
Mojtaba Babaei-Mobarakeh Amir Letafatkar Amir Hosein Barati Zohre Khosrokiani 《Journal of bodywork and movement therapies》2018,22(4):1013-1021
Background
Rehabilitation of injuries in the upper extremity and reestablishment of muscle strength throughout the range of motion in overhead movements, are the major concerns of athletes and coaches in the sports field.Purpose
To determine the effect of eight-week “gyroscopic device” mediated resistance training exercise on grip strength, wrist and shoulder strength and proprioception, and upper extremity performance, in participants with impingement syndrome or tennis elbow.Design and methods
For this study, in a university rehabilitation clinic 45 volleyball players (aged 22–28) purposefully were selected and divided into 3 groups: shoulder impingement (group I), tennis elbow (group II), and control (group III). The experimental groups performed the “gyroscopic device” mediated resistance training, three sessions a week over 8 wks. Grip strength, wrist and shoulder strength and proprioception, and upper extremity performance were measured before and after implementation of the intervention (eight-week resistance training using a “gyroscopic device”) using a hand hold dynamometer, isokinetic dynamometer, and Y balance test respectively.Results
After 8 weeks of “gyroscopic device” exercise, improvement in the shoulder, wrist and grip strength, shoulder and wrist proprioception and performance scores of both experimental groups was significant. There were no significant differences between study groups I and II, both groups, however, demonstrated significant differences when compared to the control group, but between group I and the control group, and between group II and the control group, the difference was significant. However, no significant change was seen in the control group.Conclusions
Due to the significant effects of the “gyroscopic device” mediated exercise on grip strength, wrist and shoulder strength and proprioception, and performance of the upper extremity, use of the exercise can be recommended for subjects with impingement syndrome or tennis elbow impairment in measured variables. More research is needed to confirm the result of this study. 相似文献77.
78.
Heather Olson Tiffany Rudloe Tobias Loddenkemper Marvin B. Harper Amir A. Kimia 《The American journal of emergency medicine》2018,36(8):1386-1390
Background and aims
Children with first complex febrile seizure (CFS) are often admitted for observation. The goals of this study were 1) to assess the risk of seizure recurrence during admission, 2) to determine whether early EEG affects acute management.Design/methods
We retrospectively reviewed a cohort of children 6–60 months of age admitted from a Pediatric Emergency Department for first CFS over a 15 year period. We excluded children admitted for supportive care of their febrile illness. Data extraction included age, gender, seizure features, laboratory and imaging studies, EEG, further seizures during admission, and antiepileptic drugs (AEDs) given.Results
One hundred eighty three children met inclusion criteria. Seven patients had seizures during the admission (7/183 or 3.8%) Since 38 children were loaded with anti-epileptic medication during their visit, the adjusted rate is 7/145 or 4.8.Increased risk of seizure recurrence during admission was observed in children presenting with multiple seizures (P = 0.005).EEG was performed in 104/183 children (57%) and led to change in management in one patient (1%, 95% C.I. 0.05–6%). Six of the 7 children with seizure had an EEG. The study was normal in 3 and findings in the other 2 did not suggest/predict further seizures during the admission.Conclusions
Children with first CFSs are at low risk for seizure recurrence during admission. Multiple seizures at presentation are associated with risk of early recurrence and may warrant an admission. EEG had limited effect on acute management and should not be an indication for admission. 相似文献79.
Leila Ghamkhar Amir H. Kahlaee Mohammad R. Nourbakhsh Amena Ahmadi Amir M. Arab 《Journal of manipulative and physiological therapeutics》2018,41(2):129-136
Objective
The purpose of this study was to compare the relationship between flexion endurance capacity and joint position error in participants with or without chronic neck pain (CNP).Methods
Sixty-one CNP and 60 asymptomatic volunteers participated in this cross-sectional, case-control, and correlational analysis study. The measured variables included absolute and constant joint repositioning errors in the sagittal and horizontal directions, clinical flexor endurance test score, pain intensity, and neck disability index.Results
The groups did not statistically differ in flexion endurance (P > .05). The CNP group had a smaller absolute error on the right (P < .01) and left (P = .01) rotation and an overshooting error pattern in the flexion direction (P < .05). But the asymptomatic group did not exhibit any over-/undershooting pattern tendency (P > .05). Although flexion endurance was not correlated with any of the joint repositioning error components in either group, pain and disability scores were significantly correlated with left rotation absolute error (r = –0.34 and ρ = –0.37, respectively).Conclusion
The clinical cervical flexor endurance test, ignoring the relative contribution of the deep and superficial groups of muscles, may not efficiently characterize CNP patients. 相似文献80.
Amir A. Kimia Scotty Williams Peter N. Hadar Assaf Landschaft John Porter Richard G. Bachur 《The American journal of emergency medicine》2018,36(6):931-934