全文获取类型
收费全文 | 40992篇 |
免费 | 3467篇 |
国内免费 | 1231篇 |
专业分类
耳鼻咽喉 | 51篇 |
儿科学 | 1344篇 |
妇产科学 | 201篇 |
基础医学 | 2552篇 |
口腔科学 | 62篇 |
临床医学 | 5647篇 |
内科学 | 13072篇 |
皮肤病学 | 77篇 |
神经病学 | 480篇 |
特种医学 | 1850篇 |
外国民族医学 | 7篇 |
外科学 | 2859篇 |
综合类 | 8430篇 |
现状与发展 | 2篇 |
预防医学 | 2149篇 |
眼科学 | 26篇 |
药学 | 4101篇 |
46篇 | |
中国医学 | 1831篇 |
肿瘤学 | 903篇 |
出版年
2024年 | 157篇 |
2023年 | 695篇 |
2022年 | 1325篇 |
2021年 | 1891篇 |
2020年 | 1901篇 |
2019年 | 1615篇 |
2018年 | 1585篇 |
2017年 | 1689篇 |
2016年 | 1754篇 |
2015年 | 1687篇 |
2014年 | 3024篇 |
2013年 | 3247篇 |
2012年 | 2598篇 |
2011年 | 2652篇 |
2010年 | 2141篇 |
2009年 | 1926篇 |
2008年 | 1796篇 |
2007年 | 1794篇 |
2006年 | 1621篇 |
2005年 | 1418篇 |
2004年 | 1172篇 |
2003年 | 1021篇 |
2002年 | 834篇 |
2001年 | 743篇 |
2000年 | 641篇 |
1999年 | 553篇 |
1998年 | 455篇 |
1997年 | 451篇 |
1996年 | 455篇 |
1995年 | 365篇 |
1994年 | 335篇 |
1993年 | 258篇 |
1992年 | 254篇 |
1991年 | 202篇 |
1990年 | 195篇 |
1989年 | 157篇 |
1988年 | 142篇 |
1987年 | 129篇 |
1986年 | 112篇 |
1985年 | 150篇 |
1984年 | 133篇 |
1983年 | 69篇 |
1982年 | 71篇 |
1981年 | 58篇 |
1980年 | 55篇 |
1979年 | 40篇 |
1978年 | 29篇 |
1977年 | 27篇 |
1976年 | 23篇 |
1975年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Peter MA Calverley Romain A Pauwels Paul W Jones Julie A Anderson J?rgen Vestbo 《INT J CHRONIC OBSTR》2006,1(3):209-218
Guidelines recommend that patients with COPD are stratified arbitrarily by baseline severity (FEV1) to decide when to initiate combination treatment with a long-acting β2-agonist and an inhaled corticosteroid. Assessment of baseline FEV1 as a continuous variable may provide a more reliable prediction of treatment effects. Patients from a 1-year, parallel-group, randomized controlled trial comparing 50 μg salmeterol (Sal), 500 μg fluticasone propionate (FP), the combination (Sal/FP) and placebo, (bid), were categorized post hoc into FEV1 <50% and FEV1 ≥50% predicted subgroups (n=949/513 respectively). Treatment effects on clinical outcomes – lung function, exacerbations, health status, diary card symptoms, and adverse events – were investigated. Treatment responses based on a pre-specified analysis explored treatment differences by severity as a continuous variable. Lung function improved with active treatment irrespective of FEV1; Sal/FP had greatest effect. This improvement appeared additive in milder disease; synergistic in severe disease. Active therapy significantly reduced exacerbation rate in patients with FEV1 <50% predicted, not in milder disease. Health status and breathlessness improved with Sal/FP irrespective of baseline FEV1; adverse events were similar across subgroups. The spirometric response to Sal/FP varied with baseline FEV1, and clinical benefits were not restricted to patients with severe disease. These data have implications for COPD management decisions, suggesting that arbitrary stratifications of baseline severity are not necessarily indicative of treatment efficacy and that the benefits of assessing baseline severity as a continuous variable should be assessed in future trials. 相似文献
82.
Summary. During the last decade it has been customary to estimate pulmonary epithelial permeability (P-P) as the pulmonary clearance of inhaled nebulized 99mTc-DTPA from a time-activity (t-a) curve registered externally by monitoring over the chest. The t-a curve, however, is not defined by the degree of P-P alone but also by factors such as the deposition of the 99mTc-DTPA in the lungs. To avoid these problems a plasma sample method was derived. It describes P-P by the mean transit time (t?) for the transport of 99mTc-DTPA across the pulmonary epithelial membrane, t? (L). The calculation of t? (L) involves two steps. Following the inhalation of Tc-DTPA the plasma t-a curve is defined and used to calculate t? for the transport for 99mTc-DTPA across the pulmonary epithelial membrane, through the E?V and until elimination by the kidneys, t? (L+ECV). Subsequently, 99mTc-DTPA is injected as a bolus i.v. and the new t-a curve is used to calculate t? for the transport of 99mTc-DTPA through ECV to the kidneys, t? (ECV). Finally t? (L) is calculated as t? (L) = -t? (L+ECV) t? (ECV). We applied the method in nine non-smoking individuals (median age 25–5 years, range 20–28) and compared the results to t? as calculated from the initial slope of an externally derived t-a curve. The individual t? (L) values were systematically greater than those of the external detection method (P<0·05). It is concluded that the initial slope method overestimates total PCI as measured by the plasma sample method. When choosing between the two methods, special interest should be paid to the inherent problems of the methods. 相似文献
83.
84.
Josh W. McDonald Victor L. Roggli William D. Bradford 《Fetal and pediatric pathology》1994,14(3):505-511
We report a unique case of coexistingexogenous lipoid pneumonia, endogenous lipoid pneumonia (EU), and pulmonary alveolar proteinosis (PAP) in a 5-year-old patient with severe neurodevelop mental disease. The patient presented with gastroesophageal reflux and presumed chronic lung disease resulting from recurrent aspiration pneumonias and succumbed to respiratory failure. The autopsy showed lipid-laden macrophages and periodic acid-SchiJf9ositive granular matm'al i n alveolar spaces and multilamellated structures within both alveolar macrophages and extracellular debris.
These findings were similar to those in previous reports of coexisting E I P and PAP in the setting of gastroesophageal refux [I] . However, the present case diJfered by the presence of scattered large osmiophilic extracellular lipid vacuob. Besides strengthening the association between EIP and PAP and their relationship to gastroesophageal refux, this case suggests that t h q may arise together with exogenous lipoid pneumonia, through related mechanisms, in the setting of neurodevelopmental disease. 相似文献
These findings were similar to those in previous reports of coexisting E I P and PAP in the setting of gastroesophageal refux [I] . However, the present case diJfered by the presence of scattered large osmiophilic extracellular lipid vacuob. Besides strengthening the association between EIP and PAP and their relationship to gastroesophageal refux, this case suggests that t h q may arise together with exogenous lipoid pneumonia, through related mechanisms, in the setting of neurodevelopmental disease. 相似文献
85.
大鼠肺微血管和肺泡铸型的扫描电镜观察 总被引:2,自引:0,他引:2
用扫描电镜观察以甲基丙烯酸甲酯灌注鼠的肺微血管和肺泡。胸膜下毛细血管较稀疏,网孔粗大。毛细血管部分成锐角折返,亦可见毛细血管盲端。肺泡隔毛细血管均成扁平状膨大,且相互吻合成单层密集网。肺泡铸型为大小不等、不规则的多面体,表面可见肺泡Ⅱ型细胞核之压迹。两肺泡之间可见呈桥式连接的肺泡孔,亦可见部分呈三通管样相连。 相似文献
86.
Summary A case is described of symmetrical cavitating brain stem necrosis produced by cardiac arrest in a premature infant. Two months after birth this 25-week gestational age infant suffered a prolonged episode of bradycardia. She was resuscitated and then died 3 weeks later. The autopsy revealed striking bilateral cavitation of the brain stem tegmentum extending in a columnar fashion from the upper portion of the spinal cord to the hypothalamus. The findings in this case are identical to the brain stem injury experimentally produced by complete cardiac arrest in the rhesus monkey. 相似文献
87.
类风湿性关节炎的肺部表现 总被引:1,自引:0,他引:1
本文对30例类风湿性关节炎患者中合并肺部损害的6例患者进行报道。其肺部的主要临床表现为胸痛、咳嗽、气短、长期低热及呼吸困难。体征主要为肺部干湿性罗音及胸膜摩擦音。胸部X线检查可见胸腔积液、胸膜肥厚粘连,弥漫性间质性肺纤维化、间质性肺炎。实验室检查可有嗜酸性粒细胞增高、类风湿因子阳性、血沉增快、免疫球蛋白增高等。本文并对类风湿性关节炎合并肺部病变的发生机理进行了初步探讨。 相似文献
88.
Pulmonary cryptococcosis (PC) is a subacute or chronic pulmonary fungitis caused hy Cryptococcus neoformans.Because of no specific clinical symptoms or manifestaions in chest radiographs, misdiagnosis is common. Between January 1980 and january 2004, 23 eases of PC were diagnosed by pathological examinations in our hospital and the clinical data were retospectively analyzed to inprove the diagnosis of PC. 相似文献
89.
90.
Demosthenes Katritsis Kenneth A Ellenbogen A John Camm 《Europace : European pacing, arrhythmias, and cardiac electrophysiology》2004,6(5):425-432
BACKGROUND: The clinical significance of conduction recurrences in isolated pulmonary veins of patients with atrial fibrillation is not established. METHODS: Twenty-two patients with paoxysmal atrial fibrillation underwent successful pulmonary vein isolation. Six months after the procedure, 14 patients were free of atrial fibrillation. Two of these patients were subjected to repeat mapping of the left superior pulmonary vein. RESULTS: There was recurrence of pulmonary vein to left atrium conduction despite complete lack of symptoms or evidence of recurrent atrial fibrillation. CONCLUSION: Successful pulmonary vein isolation with abolition of paroxysmal atrial fibrillation does not confer permanent disconnection of the pulmonary vein musculature from the left atrium. 相似文献