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   2083324篇
  免费   158101篇
  国内免费   4732篇
耳鼻咽喉   28413篇
儿科学   68088篇
妇产科学   59451篇
基础医学   295609篇
口腔科学   56884篇
临床医学   183736篇
内科学   414048篇
皮肤病学   47053篇
神经病学   170270篇
特种医学   80668篇
外国民族医学   772篇
外科学   317014篇
综合类   47849篇
现状与发展   3篇
一般理论   706篇
预防医学   160968篇
眼科学   47521篇
药学   147548篇
  1篇
中国医学   4562篇
肿瘤学   114993篇
  2019年   16300篇
  2018年   22949篇
  2017年   17722篇
  2016年   19570篇
  2015年   22068篇
  2014年   31412篇
  2013年   47345篇
  2012年   63994篇
  2011年   68009篇
  2010年   40352篇
  2009年   38453篇
  2008年   63505篇
  2007年   67289篇
  2006年   67886篇
  2005年   66185篇
  2004年   63410篇
  2003年   60734篇
  2002年   59004篇
  2001年   100489篇
  2000年   102999篇
  1999年   86271篇
  1998年   24232篇
  1997年   22032篇
  1996年   22059篇
  1995年   20689篇
  1994年   19049篇
  1993年   17953篇
  1992年   65772篇
  1991年   62855篇
  1990年   60827篇
  1989年   58163篇
  1988年   53667篇
  1987年   52537篇
  1986年   49597篇
  1985年   47348篇
  1984年   35853篇
  1983年   30441篇
  1982年   18415篇
  1981年   16242篇
  1979年   32220篇
  1978年   22658篇
  1977年   18929篇
  1976年   17920篇
  1975年   18996篇
  1974年   22853篇
  1973年   21992篇
  1972年   20652篇
  1971年   18909篇
  1970年   18100篇
  1969年   16876篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Accurate assessment of the amount and intensity of physical activity in daily life is considered very important due to the close relationship between physical activity level, health, disability and mortality. For this reason, assessment of physical activity in daily life has gained interest in recent years, especially in sedentary populations, such as patients with chronic obstructive pulmonary disease (COPD). The present article aims to compare and discuss the two kinds of instruments more commonly used to quantify the amount of physical activity performed by COPD patients in daily life: subjective methods (questionnaires, diaries) and motion sensors (electronic or mechanical methods). Their characteristics are summarised and evidence of their validity, reliability and sensitivity is discussed, when available. Subjective methods have practical value mainly in providing the patients' view on their performance in activities of daily living and functional status. However, care must be taken when using subjective methods to accurately quantify the amount of daily physical activity performed. More accurate information is likely to be available with motion sensors rather than questionnaires. The selection of which motion sensor to use for quantification of physical activity in daily life should depend mainly on the purpose of its use.  相似文献   
73.
There is increasing evidence that the assessment of eosinophilic airway inflammation using induced sputum and measurement of airway hyperresponsiveness provides additional, clinically important information concerning asthma control. The aim of this study was to directly compare the effects of different treatments on these markers in patients with asthma and persistent symptoms, despite the use of low-dose inhaled corticosteroids. A double-blind four-way crossover study was performed, which compared a 1-month treatment with budesonide 400 mug b.i.d., additional formoterol, additional montelukast and placebo in 49 patients with uncontrolled asthma despite budesonide 100 mug b.i.d., with each treatment separated by a 4-week washout period. The change in sputum eosinophil count with formoterol (2.4 to 3.8% change, 0.6-fold reduction, 95% confidence interval (CI) 0.5-0.9) differed significantly from placebo (2.8 to 2.5% change, 1.1-fold reduction, 95% CI 0.7-1.6) and high-dose budesonide (2.7 to 1.6% change, 1.6-fold reduction, 95% CI 1.2-2.2). The effects of montelukast did not differ from placebo. The changes in methacholine airway responsiveness were small and did not differ between treatments. High-dose budesonide had the broadest range of beneficial effects on other outcomes, including symptom scores, morning peak expiratory flow and forced expiratory volume in one second. In conclusion, treatment given in addition to low-dose inhaled corticosteroids results in modest benefits. Formoterol and high-dose budesonide have contrasting effects on eosinophilic airway inflammation.  相似文献   
74.
The aim of the current study was to investigate whether alterations in N-terminal pro brain natriuretic peptide (NT-proBNP) reflect changes in right ventricular structure and function in pulmonary hypertension patients during treatment. The study consisted of 30 pulmonary hypertension patients; 15 newly diagnosed and 15 on long-term treatment. NT-proBNP, right heart catheterisation and cardiac magnetic resonance imaging measurements were performed, at baseline and follow-up. There were no significant differences between newly diagnosed patients and those on treatment at baseline or follow-up with respect to NT-proBNP, haemodynamics and right ventricular parameters. Relative changes in NT-proBNP during treatment were correlated to the relative changes in right ventricular end-diastolic volume index (r = 0.59), right ventricular mass index (r = 0.62) and right ventricular ejection fraction (r = -0.81). N-terminal pro brain natriuretic peptide measurements reflect changes in magnetic resonance imaging-measured right ventricular structure and function in pulmonary hypertension patients. An increase in N-terminal pro brain natriuretic peptide over time reflects right ventricular dilatation concomitant to hypertrophy and deterioration of systolic function.  相似文献   
75.
76.
Comment     
  相似文献   
77.
The pharmacokinetics (PK) of moxifloxacin in healthy white New Zealand rabbits was studied following intravenous (IV) and subcutaneous (SC) administration routes as well as a SC long‐acting poloxamer 407 gel formulation (SC‐P407). Moxifloxacin concentrations were determined by high‐performance liquid chromatography assay with fluorescence detection. Mean half‐life for IV, SC and SC‐P407 routes was 2.15, 5.41 and 11.09 h. Clearance value after IV dosing was 0.78 l/kg/h. After SC administration, the mean absolute bioavailability was 117% and the Cmax was 1.61 ± 0.49 mg/l. After SC‐P407 administration, the bioavailability was 44% and the Cmax 1.83 was ±0.62 mg/l. No adverse effects were observed in any of the rabbits following IV, SC and SC‐P407 administration of moxifloxacin. Minimal inhibitory concentrations of moxifloxacin against different strains of Staphylococcus aureus from different european countries were used to compute the main pharmacodynamic (PD) surrogate markers of efficacy. The high tolerability of this SC‐P407 formulation and the favourable PK behaviour such as the long half‐life, acceptable bioavailability and excellent PK–PD ratios achieved indicate that it is likely to be effective in rabbits.  相似文献   
78.
79.
Abstract The pain of cluster headache attacks is severe, excruciating and selectively responsive to subcutaneous sumatriptan. Serious cardiovascular events attributed to sumatriptan are extremely rare and have most often been reported in patients at significant cardiovascular risk, or in overt cardiovascular disease. They also have occurred, however, in patients without evidence of cardiovascular disease. We describe a 42-year-old man with episodic cluster headache without history of coronary artery disease who was admitted to our coronary care unit for acute myocardial infarction after 3 h of subcutaneous injection of sumatriptan. During hospitalisation cluster headache attacks were successfully treated with e.v. indomethacin.  相似文献   
80.
OBJECTIVE: To evaluate the prenatal distribution, associated conditions and outcome of the different types of right aortic arch (RAA) detected in fetal life. METHODS: This was a retrospective review of all cases of RAA detected prenatally between 1998 and 2005 in two tertiary referral centers. RESULTS: In the study period 71 cases of RAA were detected; 26 (37%) had RAA with aberrant left subclavian artery, 23 (32%) had RAA with mirror-image branching, 20 (28%) had RAA of unknown type and two (3%) had double aortic arch. While 20/26 cases with RAA and aberrant left subclavian artery were isolated findings, all 23 cases with RAA and mirror-image branching were associated with cardiac defects, namely tetralogy of Fallot (43%) or pulmonary atresia with ventricular septal defect (22%). Of the 20 cases with RAA, 19 of unknown type were associated with heterotaxy syndromes and had additional cardiac malformations and ambiguities of the situs. The two cases with DAA were isolated findings. Seven cases in our series (10%) had a microdeletion 22q11 and these were significantly associated with extracardiac malformations. The outcome in our series depended solely on the associated cardiac and extracardiac malformations, with the exception of one infant with isolated DAA, in whom a surgical correction was warranted. CONCLUSIONS: RAA detected in fetal life is associated frequently with other cardiac/non-cardiac malformations, heterotaxy syndromes and microdeletions 22q11. The associated conditions vary depending on the branching type of the brachiocephalic vessels and the presence of extracardiac malformations.  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