首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   40825篇
  免费   2644篇
  国内免费   866篇
耳鼻咽喉   362篇
儿科学   944篇
妇产科学   339篇
基础医学   3190篇
口腔科学   411篇
临床医学   5994篇
内科学   7880篇
皮肤病学   188篇
神经病学   2497篇
特种医学   1152篇
外国民族医学   2篇
外科学   4832篇
综合类   5851篇
现状与发展   3篇
预防医学   2407篇
眼科学   2511篇
药学   4381篇
  25篇
中国医学   1229篇
肿瘤学   137篇
  2023年   648篇
  2022年   810篇
  2021年   1536篇
  2020年   1553篇
  2019年   1349篇
  2018年   1397篇
  2017年   1282篇
  2016年   1283篇
  2015年   1225篇
  2014年   2638篇
  2013年   3049篇
  2012年   2120篇
  2011年   2412篇
  2010年   1808篇
  2009年   1793篇
  2008年   1913篇
  2007年   1911篇
  2006年   1706篇
  2005年   1421篇
  2004年   1241篇
  2003年   995篇
  2002年   891篇
  2001年   858篇
  2000年   669篇
  1999年   625篇
  1998年   530篇
  1997年   550篇
  1996年   459篇
  1995年   524篇
  1994年   470篇
  1993年   407篇
  1992年   422篇
  1991年   373篇
  1990年   348篇
  1989年   306篇
  1988年   318篇
  1987年   286篇
  1986年   262篇
  1985年   294篇
  1984年   298篇
  1983年   176篇
  1982年   240篇
  1981年   193篇
  1980年   171篇
  1979年   149篇
  1978年   131篇
  1977年   76篇
  1976年   64篇
  1975年   45篇
  1974年   31篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
21.
BackgroundTraditional running shoes with heel-to-toe drops is thought to be a contributor to increased patellofemoral joint stress, which is proposed as a mechanism of patellofemoral pain.Research questionIs there an increase in patellofemoral joint stress when running in shoes with drops compared to running in shoes without a drop?MethodsLower limbs kinematics and ground reaction force were collected from eighteen healthy runners during over-ground running in shoes with 15 mm, 10 mm, 5 mm drops, and without a drop. Patellofemoral joint force and stress were calculated from the kinematic and kinetic data using a biomechanical model of the patellofemoral joint.ResultsThe peak patellofemoral joint stress was increased by more than 15% when running in shoes with 15 mm and 10 mm drops compared to running in shoes without a drop (p = 0.003, p = 0.001). The knee flexion angle was significantly increased when running in shoes with 15 mm, 10 mm and 5 mm drops (p = 0.014, p = 0.003, p = 0.002), the knee extension moment (p = 0.009, p = 0.002) and patellofemoral joint force (p = 0.003, p = 0.001) were increased when running in shoes with 15 mm and 10 mm drops, compared to running in shoes without a drop.SignificanceCompared to running in shoes without a drop, running in shoes with drops > 5 mm increase the peak patellofemoral joint stress significantly, which is mainly due to the increased knee extension moment.  相似文献   
22.
目的分析重症肺炎并呼吸衰竭患儿接受早期持续气道正压通气(CPAP)治疗对血气指标及预后的影响。方法选取2019年2月至2020年6月本院收治的110例重症肺炎并呼吸衰竭患儿,按照组间基本资料具有可比性的原则分为对照组与实验组,各55例。对照组接受常规方案治疗,实验组接受早期持续CPAP治疗,比较两组血气指标改善情况以及患儿预后。结果治疗后,两组PaO2、PaCO2、SaO2均显著改善,且实验组改善程度明显优于对照组(P<0.05)。实验组临床病死率明显低于对照组(P<0.05)。两组并发症发生率比较差异无统计学意义。结论采用早期持续CPAP治疗重症肺炎并呼吸衰竭患儿效果显著,能明显改善血气指标和预后,具有临床推广价值。  相似文献   
23.
24.
25.
Magnetic resonance elastography aims to non-invasively and remotely characterize the mechanical properties of living tissues. To quantitatively and regionally map the shear viscoelastic moduli in vivo, the technique must achieve proper mechanical excitation throughout the targeted tissues. Although it is straightforward, ante manibus, in close organs such as the liver or the breast, which practitioners clinically palpate already, it is somewhat fortunately highly challenging to trick the natural protective barriers of remote organs such as the brain. So far, mechanical waves have been induced in the latter by shaking the surrounding cranial bones. Here, the skull was circumvented by guiding pressure waves inside the subject's buccal cavity so mechanical waves could propagate from within through the brainstem up to the brain. Repeatable, reproducible and robust displacement fields were recorded in phantoms and in vivo by magnetic resonance elastography with guided pressure waves such that quantitative mechanical outcomes were extracted in the human brain.  相似文献   
26.
ObjectiveTo investigate the feasibility of transnasal heated humidified high flow nasal cannula oxygen therapy (HFNC) in the treatment of acute exacerbation of chronic obstructive pulmonary disease (AECOPD) with respiratory failure in elderly patients. MethodsA total of 176 elderly patients with AECOPD complicated with respiratory failure who were hospitalized at Peking University Shougang Hospital from December 2016 to January 2022 were enrolled, including 82 patients in an HFNC group and 94 patients in an NPPV group. After treatment, pulse oxygen saturation (SPO2), arterial partial pressure of carbon dioxide (PaCO2), oxygenation index (OI), respiratory rate (RR), heart rate (HR), mean arterial pressure (MAP), comfort score, discharge rate, rate of endotracheal intubation, rate of transfer to intensive care unit (ICU), and mortality were compared between the two groups. The independent sample t-test was used for comparison between the two groups. Statistical data are expressed in percentage or number of cases and the χ2 test was used for their comparisons. ResultsThe SPO2 values at 30 min, 1 h, and 6 h were significantly higher in the HFNC group than in the NPPV group (t=-2.049,-2.618, and -3.314, P=0.043, 0.010, and 0.001, respectively). SPO2 before discharge was significantly lower than that of the NPPV group (t=2.162, P=0.033), but OI at each time point and before discharge had no statistical significance (P>0.05). MAP at 6 h was significantly higher in the HFNC group than in the NPPV group (t=-2.209, P=0.029), but within the normal range. HRs at 2 h and 3 h in the HFNC group were significantly higher than those of the NPPV group (t=-2.199 and -2.336, P=0.030 and 0.021, respectively). There were no significant differences in RR, HR, or MAP between the two groups at other time points and before discharge (P>0.05). There was no significant difference in PaCO2 between the two groups (P>0.05). Comfort score in the HFNC group was significantly higher than that of the NPPV group (t=-46.807, P<0.001). There were no significant differences in discharge rate, ICU transfer rate, endotracheal intubation rate, and mortality between the two groups (P>0.05). ConclusionHFNC is as effective as NPPV in treating elderly patients with AECOPD complicated with type Ⅰ or mild type Ⅱ respiratory failure, and HFNC is more comfortable than NPPV.  相似文献   
27.
目的探讨肝细胞生长因子(HGF)过表达对慢性阻塞性肺疾病小鼠肺功能、肺动脉压力的影响及相关机制。方法取30只小鼠建立慢阻肺模型,随机分为模型组、HGF组、HGF+PI3K抑制剂LY294002组,各10只,另取10只小鼠设为对照组。各组小鼠给予相应处理后,采用实验仪器检测肺功能和肺动脉压力指标,ELISA法检测肺组织爱帕琳肽(Apelin)水平,RT-PCR检测肺组织HGF mRNA表达量,Western blot检测肺组织相关蛋白表达量,TUNEL法检测肺组织细胞凋亡。结果与对照组比较,模型组小鼠mPAP水平升高,TV、PEF、PIF、FEV0.3、FEV0.3/FVC、Apelin水平降低,肺组织HGF mRNA和蛋白表达量降低,Caspase-3表达量和细胞凋亡率升高,Bcl-2表达量、p-PI3K/PI3K和p-Akt/Akt比值降低,差异均有统计学意义(P<0.05)。HGF过表达可显著逆转模型组上述指标水平,LY294002显著抑制HGF过表达对慢阻肺小鼠的作用效果。结论HGF可通过增加Apelin水平、抑制细胞凋亡改善慢阻肺小鼠肺功能和肺动脉压力,其作用机制可能与PI3K/Akt信号通路的激活相关。  相似文献   
28.
ObjectiveTo report the clinical evolution and the urodynamic behaviour of several lower tract urinary symptoms in patients with obstructive sleep apnea syndrome before and after the treatment with continuous positive airway pressure (CPAP) devices.MethodsA prospective study was performed; patients with recent diagnosis of sleep apnea confirmed by nocturnal sleep polygraphy and absence of medical urological past history. In order to discard important lower urinary tract conditions, urological examinations were previously performed. Urinary symptoms were evaluated using the IPSS and OAB-V8 validated questionnaires, three-day Bladder Diary and invasive urodynamic examinations with a gap of one year before and one year after using the CPAP.Results84 urodynamic studies were carried out in 43 patients. The IPSS score decreased by 3.58 points. The OAB-V8 score decreased by 2.87 points. Nocturia episodes decreased to one per night. The percentage of patients with nocturnal polyuria went down to 26%. The bladder compliance significantly increased (97.39 vs 200.40 ml/cm H2O). The presence of detrusor overactivity decreased from 11 (before CPAP) to 5 patients (after CPAP).ConclusionThe proper treatment with CPAP showed a statistical and clinical improvement of several LUTS with limited urodynamic modifications.  相似文献   
29.
Pressure ulcers (PUs) are a serious health care problem for nursing home residents and a key quality metric for regulators. Three initiatives were introduced at a 128‐bed facility to improve PU prevention. First, a Quality Assurance and Performance Improvement project and a Root Cause Analysis were conducted to improve the facility's wound care programme. Second, a digital wound care management solution was adopted to track wound management. Third, the role of skin integrity coordinator was created as a central point of accountability for wound care‐related activities and related performance metrics. Improvements in PU prevention were tracked using Centers of Medicare and Medicaid data, specifically (a) the percentage of long‐stay high‐risk residents with PUs and (b) the percentage of short‐stay residents with PUs that are new or have worsened. PU prevalence for long‐stay high‐risk residents was 12.99% (Q4 2016), and upon implementation of these initiatives, the facility saw continued reductions in PU prevalence to 2.9% (Q4 2017), while PUs for short‐stay residents were maintained at zero throughout this period. This study highlights the power of effective management combined with real‐time data analytics, as enabled by digital wound care management, to make significant improvements in health care delivery.  相似文献   
30.
PurposeTo evaluate the safety and efficacy of balloon pulmonary angioplasty (BPA) for nonoperable chronic thromboembolic pulmonary hypertension (CTEPH) patients during the initial experience of a single center.MethodsA total of 18 CTEPH patients (5 with residual pulmonary hypertension after pulmonary endarterectomy) were treated with BPA during the period 2014–2018 and were retrospectively reviewed. Mean age was 61 ± 19 years; 55% were female; mean pulmonary artery pressure was 44 ± 12 mmHg; cardiac output was 4.3 ± 1.0 l/min; and pulmonary vascular resistance was 8.4 ± 3.6 WU. Patients were evaluated by New York Heart Association functional class, 6-minute walk distance, N-terminal pro b-type natriuretic peptide, echocardiography, right heart catheterization, and before and after completions of BPA.ResultsA total of 91 procedures were performed, with a median number of 4 BPA sessions per patient (range, 2–8). There were no deaths or major complications requiring extracorporeal support or (non)invasive ventilation. The most common complication was self-limiting hemoptysis (3%). According to Society of Interventional Radiology classification, 4 mild, 4 moderate, and 1 severe adverse events were noted. Invasive hemodynamics significantly improved, with a cardiac index increase of 15% (P = .0333), decrease of mean pulmonary artery pressure of 30% (P = .0013), and decrease of pulmonary vascular resistance of 45% (P = .0048). Stroke volume index (P = .0171) and pulmonary arterial compliance (P = .0004) were also significantly enhanced.ConclusionsBPA significantly improves cardiopulmonary hemodynamics with an acceptable safety profile. Further studies assessing the long-term efficacy of BPA are required.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号