全文获取类型
收费全文 | 137834篇 |
免费 | 12371篇 |
国内免费 | 3631篇 |
专业分类
耳鼻咽喉 | 1064篇 |
儿科学 | 1938篇 |
妇产科学 | 1378篇 |
基础医学 | 12237篇 |
口腔科学 | 4561篇 |
临床医学 | 22093篇 |
内科学 | 15234篇 |
皮肤病学 | 1457篇 |
神经病学 | 12073篇 |
特种医学 | 24894篇 |
外国民族医学 | 304篇 |
外科学 | 12379篇 |
综合类 | 18102篇 |
现状与发展 | 11篇 |
预防医学 | 5171篇 |
眼科学 | 1947篇 |
药学 | 8122篇 |
72篇 | |
中国医学 | 3972篇 |
肿瘤学 | 6827篇 |
出版年
2024年 | 132篇 |
2023年 | 1988篇 |
2022年 | 2810篇 |
2021年 | 4812篇 |
2020年 | 4931篇 |
2019年 | 4720篇 |
2018年 | 4741篇 |
2017年 | 4865篇 |
2016年 | 5152篇 |
2015年 | 5109篇 |
2014年 | 12325篇 |
2013年 | 11270篇 |
2012年 | 9332篇 |
2011年 | 9727篇 |
2010年 | 9583篇 |
2009年 | 9356篇 |
2008年 | 7627篇 |
2007年 | 6447篇 |
2006年 | 5622篇 |
2005年 | 4922篇 |
2004年 | 4196篇 |
2003年 | 3399篇 |
2002年 | 2688篇 |
2001年 | 2526篇 |
2000年 | 2022篇 |
1999年 | 1631篇 |
1998年 | 1458篇 |
1997年 | 1363篇 |
1996年 | 1146篇 |
1995年 | 1146篇 |
1994年 | 956篇 |
1993年 | 790篇 |
1992年 | 685篇 |
1991年 | 598篇 |
1990年 | 493篇 |
1989年 | 373篇 |
1988年 | 370篇 |
1987年 | 318篇 |
1986年 | 254篇 |
1985年 | 301篇 |
1984年 | 263篇 |
1983年 | 189篇 |
1982年 | 203篇 |
1981年 | 214篇 |
1980年 | 175篇 |
1979年 | 128篇 |
1978年 | 107篇 |
1977年 | 77篇 |
1976年 | 103篇 |
1975年 | 39篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
101.
102.
Abdol-Mohammad Kajbafzadeh Reza Khorramirouz Seyedeh Maryam Kameli Kiarad Fendereski Seyedeh Sima Daryabari Seyed Mohammad Tavangar Bahram Azizi Garajegayeh 《The Journal of thoracic and cardiovascular surgery》2019,157(4):1494-1502
Background
Various investigations have reported that the internal mammary artery (IMA) is an efficient and functional choice of conduit for vascular graft surgeries, especially for coronary artery bypass grafts; however, the quest to find an ideal vascular substitute remains. We hypothesized that acellular IMA could be an appropriate graft for small-diameter vascular bypasses that could be used in various surgeries including coronary artery bypass grafting.Methods
We decellularized human IMAs and performed histologic evaluations and scanning electron microscopy to confirm the decellularization process and the preservation of the extracellular matrix. Subsequently, we grafted the scaffolds into the superficial femoral arteries of 8 New Zealand rabbits with an end-to-end anastomosis. Computed tomography angiograms were provided at 3, 12, and 36 months postoperatively. Subsequently, the animals were killed, and biopsies were taken for histologic and immunohistochemical assessments.Results
Evaluation of the acellular tissue confirmed the efficacy of the decellularization protocol and the preservation of the extracellular matrix. All 8 animals survived the entire follow-up period. Doppler ultrasonography and computed tomography angiographies verified the conduit's patency. Histologic assessments depicted the recellularization of all 3 layers of the scaffold. Smooth muscle cells were detected in tunica media. Immunohistochemical assessments confirmed these findings.Conclusions
In conclusion, we demonstrated that acellular human IMA could be used as an efficient small-diameter vascular substitute with high patency. These findings could pave the path for future investigations on the clinical application of acellular IMA as a novel vascular graft for small-diameter bypass surgeries. 相似文献103.
Intravenous leiomyomatosis (IVL) with intracardiac extension is a rare condition, which the benign tumor invades into the right heart through inferior vena cava. We described the findings of ultrasonography in eight patients with this disease. Transthoracic echocardiography (TTE) can reveal the intracardiac lesion burden and associated compromise. Contrast‐enhanced ultrasonography (CEUS) can trace the origin of the lesion and extension. Therefore, combining TTE with CEUS is used to better characterize this complex lesion and plays a crucial role in guidance of surgical decision. 相似文献
104.
105.
106.
107.
Martin V. Andersen Cooper Moore Peter Søgaard Daniel Friedman Brett D. Atwater Kristine Arges Melissa LeFevre Johannes J. Struijk Joseph Kisslo Samuel E. Schmidt Olaf T. von Ramm 《Ultrasound in medicine & biology》2019,45(5):1197-1207
Recently, we developed a high-frame-rate echocardiographic imaging system capable of acquiring images at rates up to 2500 per second. High imaging rates were used to quantify longitudinal strain parameters in patients with echocardiographically normal function. These data can serve as a baseline for comparing strain parameters in disease states. The derived timing data also reveal the propagation of mechanical events in the left ventricle throughout the cardiac cycle. High-frame-rate echocardiographic images were acquired from 17 patients in the apical four-chamber view using Duke University's phased array ultrasound system, T5. B-Mode images were acquired at 500–1000 images per second by employing 16:1 or 32:1 parallel processing in receive, a scan depth ≤14 cm and an 80° field of view with a 3.5-MegaHertZ (MHz), 96-element linear array. The images were analyzed using a speckle tracking algorithm tailored for high-frame-rate echocardiographic images developed at Aalborg and Duke University. Four specific mechanical events were defined using strain curves from six regions along the myocardial contour of the left ventricle. The strain curves measure the local deformation events of the myocardium and are independent of the overall cardiac motion. We observed statistically significant differences in the temporal sequence among different myocardial segments for the first mechanical event described, myocardial tissue shortening onset (p < 0.01). We found that the spatial origin of tissue shortening was located near the middle of the interventricular septum in patients with echocardiographically normal function. The quantitative parameters defined here, based on high-speed strain measurements in patients with echocardiographically normal function, can serve as a means of assessing degree of contractile abnormality in the myocardium and enable the identification of contraction propagation. The relative timing pattern among specific events with respect to the Q wave may become an important new metric in assessing cardiac function and may, in turn, improve diagnosis and prognosis. 相似文献
108.
Shih-Chuan Chou Justine M. Nagurney Scott G. Weiner Arthur S. Hong J. Frank Wharam 《The American journal of emergency medicine》2019,37(6):1037-1043
ObjectivesTo describe recent trends in advanced imaging and hospitalization of emergency department (ED) syncope patients, both considered “low-value”, and examine trend changes before and after the publication of American College Emergency Physician (ACEP) syncope guidelines in 2007, compared to conditions that had no changes in guideline recommendations.MethodsWe analyzed 2002–2015 National Hospital Ambulatory Medical Care Survey data using an interrupted-time series with comparison series design. The primary outcomes were advanced imaging among ED visits with principal diagnosis of syncope and headache and hospitalization for ED visits with principal diagnosis of syncope, chest pain, dysrhythmia, and pneumonia. We adjusted annual imaging and hospitalization rates using survey-weighted multivariable logistic regression, controlling for demographic and visit characteristics. Using adjusted outcomes as datapoints, we compared linear trends and trend changes of annual imaging and hospitalization rates before and after 2007 with aggregate-level multivariable linear regression.ResultsFrom 2002 to 2007, advanced imaging rates for syncope increased from 27.2% to 42.1% but had no significant trend after 2007 (trend change: ?3.1%; 95%CI ?4.7, ?1.6). Hospitalization rates remained at approximately 37% from 2002 to 2007 but declined to 25.7% by 2015 (trend change: ?2.2%; 95%CI ?3.0, ?1.4). Similar trend changes occurred among control conditions versus syncope, including advanced imaging for headache (difference in trend change: ?0.6%; 95%CI ?2.8, 1.6) and hospitalizations for chest pain, dysrhythmia, and pneumonia (differences in trend changes: 0.1% [95%CI ?1.9, 2.0]; ?0.9% [95%CI ?3.1, 1.3]; and ?1.2% [95%CI ?5.3, 2.9], respectively).ConclusionsBefore and after the release of 2007 ACEP syncope guidelines, trends in advanced imaging and hospitalization for ED syncope visits had similar changes compared to control conditions. Changes in syncope care may, therefore, reflect broader practice shifts rather than a direct association with the 2007 ACEP guideline. Moreover, utilization of advanced imaging remains prevalent. To reduce low-value care, policymakers should augment society guidelines with additional policy changes such as reportable quality measures. 相似文献
109.
Yueh-Ling Hsieh Ming-Ta Lin Chang-Zern Hong Hsin-Shui Chen 《Foot and Ankle Surgery》2019,25(2):186-192
Background
This study investigated the effects of percutaneous soft tissue release (PSTR) performed using a blunt cannula on (1) the inflammatory cells-count, (2) expressions of calcitonin gene-related peptide (CGRP) and (3) substance P (SP) in rabbits with chronic phase of collagenase-induced Achilles tendinopathy.Methods
Thirty-two adult male New Zealand rabbits were randomly divided into four groups: (1) collagenase and PSTR treatment; (2) collagenase and sham-operated PSTR treatment; (3) vehicle-only injection and PSTR treatment; and (4) vehicle-only injection and sham-operated PSTR treatment. Achilles tendon of adult male rabbits was injected with 10 μl of collagenase under ultrasonography localization. After 30 days, PSTR was performed using an 18G beauty cosmetic blunt tip micro cannula needle to release the soft tissue and paratenon above the inflamed Achilles tendon. The treated tendons and spinal cords of L5-S2 were harvested 5 days after treatment for histological assessment and immunohistochemical analysis.Results
Histopathological examination revealed that PSTR achieved significant reduction in hypercellularity with pronounced infiltration of immune cells at the site of paratenon in tendons injected with collagenase compared with sham operation (p < 0.05). Immunohistochemical analysis also showed marked decrease in expression of CGRP in tendon and SP in dorsal horns after PSTR (p < 0.05).Conclusions
This study showed positive effects in an animal model of chronic tendinopathy, and can be considered a treatment option, but that further research is necessary to determine its role in clinical practice. 相似文献110.
Xianxiu Ji Huikang Xie Ren Zhu Bin Chen Sen Jiang Jie Luo 《The Journal of international medical research》2021,49(2)
ObjectiveTo compare the baseline clinical characteristics between patients with ROS1-positive and ALK-positive advanced non-small cell lung cancer (NSCLC), and the correlations of these subtypes with the distribution of metastases.MethodsWe compared the clinical characteristics and imaging features of patients with ROS1-positive and ALK-positive NSCLC using statistical methods.ResultsData for 232 patients were analyzed. Compared with ALK-positive NSCLC, ROS1-positive NSCLC was more likely to occur in women (71% vs 53%), and primary lesions ≤3 cm were more common in patients with ROS1-positive compared with ALK-positive NSCLC (58% vs 37%). There was no significant difference in the distribution of metastases between the two groups. Subgroup analysis within the ROS1-positive group showed that, compared with primary lesions >3 cm, primary lesions ≤3 cm were more likely to present as peripheral tumors (72% vs 43%) and more likely to exhibit non-solid density (44% vs 4%).ConclusionsAlthough ROS1-positive and ALK-positive NSCLCs show similar clinical features, the differences may help clinicians to identify patients requiring further genotyping at initial diagnosis. 相似文献