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   2983542篇
  免费   259188篇
  国内免费   24312篇
耳鼻咽喉   41336篇
儿科学   88581篇
妇产科学   73684篇
基础医学   477669篇
口腔科学   78843篇
临床医学   264532篇
内科学   499701篇
皮肤病学   82999篇
神经病学   252599篇
特种医学   117546篇
外国民族医学   188篇
外科学   468481篇
综合类   125007篇
一般理论   2183篇
预防医学   240273篇
眼科学   69775篇
药学   214483篇
  176篇
中国医学   21748篇
肿瘤学   147238篇
  2021年   49118篇
  2020年   39520篇
  2019年   60454篇
  2018年   72330篇
  2017年   56918篇
  2016年   61335篇
  2015年   79086篇
  2014年   115653篇
  2013年   181514篇
  2012年   95501篇
  2011年   93875篇
  2010年   124140篇
  2009年   127823篇
  2008年   76878篇
  2007年   77894篇
  2006年   88260篇
  2005年   82461篇
  2004年   81645篇
  2003年   72399篇
  2002年   61167篇
  2001年   81157篇
  2000年   71773篇
  1999年   75034篇
  1998年   58082篇
  1997年   56287篇
  1996年   53088篇
  1995年   53843篇
  1994年   47928篇
  1993年   44723篇
  1992年   49367篇
  1991年   46130篇
  1990年   42826篇
  1989年   43221篇
  1988年   39861篇
  1987年   38762篇
  1986年   36545篇
  1985年   37322篇
  1984年   36807篇
  1983年   34418篇
  1982年   37289篇
  1981年   35393篇
  1980年   33341篇
  1979年   27805篇
  1978年   27148篇
  1977年   25795篇
  1976年   22879篇
  1975年   20958篇
  1974年   20008篇
  1973年   19083篇
  1972年   18002篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
ObjectiveTo determine prognostic factors and survival patterns for different treatment modalities for nasal cavity (NC) and paranasal sinus (PS) mucosal melanoma (MM).MethodsPatients from 1973 to 2013 were analyzed using the Surveillance, Epidemiology, and End Results (SEER) database. Kaplan-Meier method and multivariable cox proportional hazard modeling were used for survival analyses.ResultsOf 928 cases of mucosal melanoma (NC = 632, PS = 302), increasing age (Hazard Ratio [HR]:1.05/year, p < 0.001), T4 tumors (HR: 1.81, p = 0.02), N1 status (HR: 6.61, p < 0.001), and PS disease (HR: 1.50, p < 0.001) were associated with worse survival. Median survival length was lower for PS versus NC (16 versus 26 months, p < 0.001). Surgery and surgery + radiation therapy (RT) improved survival over non-treatment or RT alone (p < 0.001). Adding RT to surgery did not yield a survival difference compared with surgery alone (p = 0.43). Five-year survival rates for surgery and surgery + RT were similar, at 27.7% and 25.1% (p = 0.43).ConclusionSurgery increased survival significantly over RT alone. RT following surgical resection did not improve survival.  相似文献   
2.
目的探讨通过下食管括约肌(lower esophageal sphincter,LES)扩张建立咽喉反流性疾病(laryngophyngeal reflux disease,LPRD)模型的可行性。方法18只新西兰白兔随机分为实验组10只和对照组8只,对实验组动物进行LES测压定位后,使用球囊对LES进行注水扩张,对照组同法置入球囊,但不进行球囊注水。扩张前1周及扩张后2周行咽喉及食管下段pH监测,LES平均静息压检测;扩张前1周、扩张后2周及8周行喉镜检查,进行喉镜下反流体征评分;扩张后8周处死动物,对其喉部及食管下段黏膜取材,光镜下观察其病理变化。结果扩张后pH监测验证实验组造模成功8只(80.0%,8/10),实验组扩张前咽喉酸反流时间百分比(%)、反流事件数(次)、反流最长时间(s)分别为0(0,0)、0(0,0)、0(0,0),扩张后分别为17.5(8.2,29.4)、3(1,5.5)、17.2(10.2,30.8),较扩张前增加,差异有统计学意义(P<0.01)。实验组扩张前食管下段pH监测酸反流时间百分比、反流事件数、反流最长时间分别为0(0,0.7)、0(0,1)、0(0,1.2),扩张后分别为23.1(4.8,49.5)、3(1,6)、25.9(11.5,56.8),较扩张前增加,差异有统计学意义(P<0.01)。实验组扩张前LES压力28.0±5.6 mmHg,较扩张后(17.2±3.3 mmHg)升高,差异有统计学差异(P=0.001);实验组扩张前RFS评分3.1±1.2分,扩张后2周为3.6±1.4分,扩张后8周为8.6±2.5分,扩张前和扩张后2周差异无统计学意义(P=0.482),但扩张前与扩张后8周差异有统计学意义(P=0.005)。病理检查示实验组喉部及食管黏膜均可观察到不同程度慢性炎症。结论食管下括约肌球囊扩张可安全、有效地建立LPRD动物模型。  相似文献   
3.
Tympanic membranes (TM) that have healed spontaneously after perforation present abnormalities in their structural and mechanical properties; i.e., they are thickened and abnormally dense. These changes result in a deterioration of middle ear (ME) sound transmission, which is clinically presented as a conductive hearing loss (CHL). To fully understand the ME sound transmission under TM pathological conditions, we created a gerbil model with a controlled 50% pars tensa perforation, which was left to heal spontaneously for up to 4 weeks (TM perforations had fully sealed after 2 weeks). After the recovery period, the ME sound transmission, both in the forward and reverse directions, was directly measured with two-tone stimulation. Measurements were performed at the input, the ossicular chain, and output of the ME system, i.e., at the TM, umbo, and scala vestibuli (SV) next to the stapes. We found that variations in ME transmission in forward and reverse directions were not symmetric. In the forward direction, the ME pressure gain decreased in a frequency-dependent manner, with smaller loss (within 10 dB) at low frequencies and more dramatic loss at high frequency regions. The loss pattern was mainly from the less efficient acoustical to mechanical coupling between the TM and umbo, with little changes along the ossicular chain. In the reverse direction, the variations in these ears are relatively smaller. Our results provide detailed functional observations that explain CHL seen in clinical patients with abnormal TM, e.g., caused by otitis media, that have healed spontaneously after perforation or post-tympanoplasty, especially at high frequencies. In addition, our data demonstrate that changes in distortion product otoacoustic emissions (DPOAEs) result from altered ME transmission in both the forward and reverse direction by a reduction of the effective stimulus levels and less efficient transfer of DPs from the ME into the ear canal. This confirms that DPOAEs can be used to assess both the health of the cochlea and the middle ear.  相似文献   
4.
5.
6.
7.
Modified-release opioids are often prescribed for the management of moderate to severe acute pain following total hip and knee arthroplasty, despite recommendations against their use due to increasing concerns regarding harm. The primary objective of this multicentre study was to examine the impact of modified-release opioid use on the incidence of opioid-related adverse events compared with immediate-release opioid use, among adult inpatients following total hip or knee arthroplasty. Data for total hip and knee arthroplasty inpatients receiving an opioid analgesic for postoperative analgesia during hospitalisation were collected from electronic medical records of three tertiary metropolitan hospitals in Australia. The primary outcome was the incidence of opioid-related adverse events during hospital admission. Patients who received modified with or without immediate-release opioids were matched to those receiving immediate-release opioids only (1:1) using nearest neighbour propensity score matching with patient and clinical characteristics as covariates. This included total opioid dose received. In the matched cohorts, patients given modified-release opioids (n = 347) experienced a higher incidence of opioid-related adverse events overall, compared with those given immediate-release opioids only (20.5%, 71/347 vs. 12.7%, 44/347; difference in proportions 7.8% [95%CI 2.3–13.3%]). Modified-release opioid use was associated with an increased risk of harm when used for acute pain during hospitalisation after total hip or knee arthroplasty.  相似文献   
8.

Introduction

Left ventricular (LV) dysfunction is estimated to occur in 10%–25% of the general intensive care unit (ICU) population and is frequently seen as regional wall motion abnormalities (RWMAs). Although RWMA is mostly attributed to myocardial ischemia or infarction, some studies have suggested that nonischemic RWMA might also be prevalent. We sought to establish that RWMA can be seen in critically ill patients with normal coronary arteries and to explore reasons for RWMA in this population.

Methods

In this retrospective study, data from the hospital angiography register and the ICU register were collated between 2012 and 2019. Patients were identified who underwent angiography in conjunction with their ICU stay and had RWMA on echocardiography. Patients were divided into either those with non-obstructed or those with obstructed coronary arteries. Cardiac magnetic resonance imaging (cMRI) examinations were reviewed if they had been performed on patients with non-obstructed coronaries.

Results

We identified 53 patients with RWMA and non-obstructed coronary arteries and 204 patients with RWMA and obstructed coronary arteries. Patients with non-obstructed coronary arteries were more often female, younger, and had fewer cardiovascular risk factors. They less commonly had ST elevation, but more frequently had T-wave inversion or serious arrhythmias. Troponin levels were higher in patients with obstructed coronary arteries, but NT-proBNP was similar between the groups. There were no differences in risk-adjusted 90-day mortality between patients with non-obstructed versus obstructed coronary arteries (OR 1.21, [95% CI 0.56–2.64], p = .628). In those with non-obstructed coronary arteries, follow-up echocardiography was available for 38 patients, of whom 30 showed normalization of cardiac function. Of the 14 patients with non-obstructed coronary arteries on whom cMRI was performed, 7 had a tentative diagnosis of Takotsubo syndrome or myocardial stunning; 4 had a myocardial infarction (preexisting in 3 cases); 1 patient had acute myocarditis; 1 patient had post-myocarditis; and 1 patient was diagnosed with dilated cardiomyopathy.

Conclusion

RWMA can be seen to occur in critically ill patients in the absence of coronary artery obstruction. Several conditions can cause regional hypokinesia, and cMRI is useful to evaluate the underlying etiology.  相似文献   
9.
Post-induction hypotension is common and associated with postoperative complications. We hypothesised that pneumatic leg compression reduces post-induction hypotension in elderly patients undergoing robot-assisted laparoscopic prostatectomy. In this double-blind randomised study, patients were allocated randomly to the pneumatic leg compression group (n = 50) or control (n = 50). In the intervention group, pneumatic leg compression was initiated before induction of anaesthesia. In the control group, pneumatic leg compression was initiated 20 min after anaesthesia induction. The primary outcome was the incidence of post-induction hypotension in these groups. Post-induction hypotension was defined as systolic blood pressure < 90 mmHg during the first 20 min after induction. Haemodynamic variables and area under the curve of post-induction systolic blood pressure over time were assessed. Complications associated with pneumatic leg compression were recorded, including: peripheral neuropathy; compartment syndrome; extensive bullae beneath the leg sleeves; and pulmonary thromboembolism. The incidence of post-induction hypotension decreased in the pneumatic leg compression group compared with that in the control group; 5 (10%) vs. 29 (58%), respectively, p < 0.001. In the pneumatic leg compression group, the lowest systolic, diastolic and mean blood pressures 20 min after induction of anaesthesia were significantly greater than the control group. Pneumatic leg compression resulted in an increased area under the curve of systolic blood pressure in the first 20 min after induction, p = 0.001. There were no pneumatic leg compression-related complications. Pneumatic leg compression reduced post-induction hypotension in elderly patients undergoing robot-assisted laparoscopic prostatectomy, suggesting that it is an effective and safe intervention to prevent post-induction hypotension among elderly patients undergoing general anaesthesia.  相似文献   
10.
AIDS and Behavior - Transactional sex increases HIV risk among adolescent girls and young women (AGYW). Understanding the individual and dyadic nature of transactional sex may provide evidence for...  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