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   1761370篇
  免费   160623篇
  国内免费   4779篇
耳鼻咽喉   26460篇
儿科学   58412篇
妇产科学   48922篇
基础医学   233830篇
口腔科学   49051篇
临床医学   168075篇
内科学   360908篇
皮肤病学   41379篇
神经病学   145696篇
特种医学   71365篇
外国民族医学   499篇
外科学   283289篇
综合类   40178篇
现状与发展   75篇
一般理论   561篇
预防医学   132549篇
眼科学   39943篇
药学   123949篇
  3篇
中国医学   3040篇
肿瘤学   98588篇
  2018年   21923篇
  2017年   18666篇
  2016年   20812篇
  2015年   23017篇
  2014年   35289篇
  2013年   46443篇
  2012年   48957篇
  2011年   51346篇
  2010年   36541篇
  2009年   38975篇
  2008年   49581篇
  2007年   50249篇
  2006年   53318篇
  2005年   49322篇
  2004年   47949篇
  2003年   45111篇
  2002年   44164篇
  2001年   79551篇
  2000年   81436篇
  1999年   69653篇
  1998年   21271篇
  1997年   19592篇
  1996年   19381篇
  1995年   19002篇
  1994年   16978篇
  1993年   15832篇
  1992年   57086篇
  1991年   55467篇
  1990年   53834篇
  1989年   52101篇
  1988年   48290篇
  1987年   47525篇
  1986年   45234篇
  1985年   43677篇
  1984年   32662篇
  1983年   28109篇
  1982年   16690篇
  1981年   14878篇
  1979年   30851篇
  1978年   21436篇
  1977年   18213篇
  1976年   16994篇
  1975年   17919篇
  1974年   21826篇
  1973年   20982篇
  1972年   19224篇
  1971年   18047篇
  1970年   16613篇
  1969年   15427篇
  1968年   14038篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
53.
Pre-eclamptic toxaemia (PET) may be associated with both endothelial dysfunction (ED) and sleep-disordered breathing (SDB). It was hypothesised that females with PET would demonstrate both SDB and ED, and that a correlation between these two would suggest a potential causative association. A total of 17 females with PET and 25 matched females with uncomplicated pregnancy were studied. They underwent a nocturnal ambulatory sleep study (using Watch_PAT100) and noninvasive evaluation of endothelial function utilising the reactive hyperaemia test (using Endo_PAT 2000). A higher ratio of post- to pre-occlusion pulse-wave amplitude (endothelial function index (EFI)) indicated better endothelial function. Females with PET had a significantly higher respiratory disturbance index (RDI) and lower EFI than controls (18.4+/-8.4 versus 8.3+/-1.3.h(-1), and 1.5+/-0.1 versus 1.8+/-0.1, respectively). Blood pressure significantly correlated with RDI and with EFI. EFI tended to correlate with RDI. In conclusion, these results suggest that both sleep-disordered breathing and endothelial dysfunction are more likely to occur in females with pre-eclamptic toxaemia than in females with uncomplicated pregnancies. The current authors speculate that respiratory disturbances contribute to the functional abnormality of the blood vessels seen in females with pre-eclamptic toxaemia, although causality cannot be determined based on this study.  相似文献   
54.
The aim of this study was to determine whether patients with sickle cell disease (SCD) in steady state had pulmonary abnormalities seen on high-resolution computed tomography (HRCT) and whether any abnormalities correlated with contemporaneously diagnosed lung function abnormalities. A subsidiary question was whether the results of a noninvasive measure of haemolysis (end-tidal carbon monoxide (ETCO) levels) correlated with pulmonary function abnormalities. Thirty three patients with SCD, median (range) age 36 yrs (17-67 yrs) were examined. The degree of lobar volume loss and ground-glass opacification and prominence of central vessels on HRCT were quantitatively assessed. Pulmonary function was assessed by measurements of lung volumes, spirometry, gas transfer and oxygen saturation. ETCO levels were measured using an end-tidal CO monitor. Forced expiratory volume in one second (FEV1), forced vital capacity and total lung capacity significantly correlated with HRCT findings, particularly lobar volume loss. ETCO levels significantly negatively correlated with FEV1, vital capacity measured using a plethysmograph, specific airway conductance and arterial oxygen saturation measured by pulse oxymetry. In conclusion, the present results suggest that high-resolution computed tomography noninvasive assessment of haemolysis might be useful to identify sickle cell disease patients with respiratory function impairment.  相似文献   
55.
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   
56.
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   
57.
58.
Summary:  The immune system is capable of recognizing and eliminating an enormous array of pathogens due to the extremely diverse antigen receptor repertoire of T and B lymphocytes. However, the development of lymphocytes bearing receptors with unique specificities requires the generation of programmed double strand breaks (DSBs) coupled with bursts of proliferation, rendering lymphocytes susceptible to mutations contributing to oncogenic transformation. Consequently, mechanisms responsible for monitoring global genomic integrity must be activated during lymphocyte development to limit the oncogenic potential of antigen receptor locus recombination. Mutations in ATM (ataxia-telangiectasia mutated), a kinase that coordinates DSB monitoring and the response to DNA damage, result in impaired T-cell development and predispose to T-cell leukemia. Here, we review recent evidence providing insight into the mechanisms by which ATM promotes normal lymphocyte development and protects from neoplastic transformation.  相似文献   
59.
60.
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