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   3368305篇
  免费   245540篇
  国内免费   8420篇
耳鼻咽喉   45372篇
儿科学   110931篇
妇产科学   94139篇
基础医学   479444篇
口腔科学   93892篇
临床医学   310903篇
内科学   658709篇
皮肤病学   78989篇
神经病学   276152篇
特种医学   128742篇
外国民族医学   964篇
外科学   496236篇
综合类   69062篇
现状与发展   7篇
一般理论   1447篇
预防医学   266046篇
眼科学   75976篇
药学   246160篇
  12篇
中国医学   6468篇
肿瘤学   182614篇
  2019年   26446篇
  2018年   36812篇
  2017年   28370篇
  2016年   32441篇
  2015年   36845篇
  2014年   50760篇
  2013年   76970篇
  2012年   102384篇
  2011年   108645篇
  2010年   65023篇
  2009年   62518篇
  2008年   101979篇
  2007年   108532篇
  2006年   109749篇
  2005年   105845篇
  2004年   101875篇
  2003年   98178篇
  2002年   94884篇
  2001年   156320篇
  2000年   159970篇
  1999年   135120篇
  1998年   39168篇
  1997年   34985篇
  1996年   35435篇
  1995年   34088篇
  1994年   31424篇
  1993年   29478篇
  1992年   106266篇
  1991年   103151篇
  1990年   99928篇
  1989年   96470篇
  1988年   88961篇
  1987年   87192篇
  1986年   82193篇
  1985年   78328篇
  1984年   58923篇
  1983年   50264篇
  1982年   29972篇
  1981年   26938篇
  1979年   53039篇
  1978年   37965篇
  1977年   32216篇
  1976年   29794篇
  1975年   31903篇
  1974年   38016篇
  1973年   36672篇
  1972年   34518篇
  1971年   32097篇
  1970年   29865篇
  1969年   28503篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
921.
目的:通过16例经内窥镜及病理证实为Barrett食管的钡餐检查表现,初步探讨Barrett食管及其并发症放射学检查的意义。方法:回顾性分析16例Barrett食管的内窥镜和气钡检查的记录及表现,着重探讨气钡检查的X线表现。结果:食管内窥镜和组织学检查全部病例均有炎症改变,其他可见胃食管反流、食管溃疡和食管腺癌。放射学钡餐检查结果:Barrett食管炎4例,Barrett食管溃疡7例,Barrett食管癌5例。结论:Barrett食管及其并发症至今无明确放射学征象,改进对“Z”线的检查技术和方法,有可能提高其发现率。钡餐发现胃食管反流、食管裂孔疝同时并发食管炎、食管溃疡及食管癌者均应考虑到本症的可能。  相似文献   
922.
923.
Although the magnetic field of an MR scanner is very stable under little or no load, it can become less stable under heavy‐duty cycle conditions, such as in diffusion tensor imaging (DTI). Uncorrected, such field drifts lead to an apparent image shift along the phase‐encoding direction and decreasing effectiveness of fat saturation pulses. A method is presented to adjust the center frequency of all RF pulses and the receiver in real time during the acquisition. No data postprocessing or changes to the sequence timing are necessary. In vivo acquisitions were performed to assess the prolonged effectiveness of fat saturation. Field drifts of approximately 2.5 Hz/min were measured and corrected during DTI acquisitions at b‐values of up to 3000 s/mm2. The effectiveness of fat saturation diminished over the duration of an 18‐min acquisition when the drift was left uncorrected. The proposed method corrects for apparent image shift and ensures continuously effective fat saturation over the duration of an acquisition. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.  相似文献   
924.
In chronic myeloid leukaemia, CD34(+) stem/progenitor cells appear resistant to imatinib mesylate (IM) in vitro and in vivo. To investigate the underlying mechanism(s) of IM resistance, it is essential to quantify Bcr-Abl kinase status at the stem cell level. We developed a flow cytometry method to measure CrkL phosphorylation (P-CrkL) in samples with <10(4) cells. The method was first validated in wild-type (K562) and mutant (BAF3) BCR-ABL(+) as well as BCR-ABL(-) (HL60) cell lines. In response to increasing IM concentration, there was a linear reduction in P-CrkL, which was Bcr-Abl specific and correlated with known resistance. The results were comparable to those from Western blotting. The method also proved to be reproducible with small samples of normal and Ph(+) CD34(+) cells and was able to discriminate between Ph(-), sensitive and resistant Ph(+) cells. This assay should now enable investigators to unravel the mechanism(s) of IM resistance in stem cells.  相似文献   
925.
Using complete denture treatment as an introduction to clinical patient care for dental students, the purposes of the Complete Denture Prosthodontics Transition Clinic at the University of Colorado School of Dentistry are to reduce the time lapse between the preclinical complete denture prosthodontics course and the first denture patient experience, and to encourage development of student self-confidence and skills. In the 2002 spring semester, faculty at the University of Colorado School of Dentistry initiated the Complete Denture Prosthodontics Transition Clinic for DS-II (second-year) dental students, as an introduction to clinical patient care. Each patient was assigned to a team of two dental students. Three Division of Prosthodontics faculty members staffed each clinic session, providing a student-to-faculty ratio of approximately 6.6:1 and a patient-to-faculty ratio of approximately 3.3:1. All DS-II students in the Class of 2004 delivered their first complete dentures no later than 8 months (average, 184 days) after the last day of the preclinical complete denture prosthodontics course. The time from the diagnostic appointment through the denture placement appointment averaged 39 days for patients treated in this program, compared with an average of 98 days or more for previous classes. The program was successful in achieving the goal of reducing the time lapse between the preclinical complete denture prosthodontics course and the first denture patient experience.  相似文献   
926.
Calcitonin therapy for central giant cell granuloma.   总被引:4,自引:0,他引:4  
PURPOSE: A number of alternative nonsurgical therapies have been advocated in recent years for the management of the central giant cell granuloma (CGCG). These include calcitonin injections, intralesional steroid injections and subcutaneous alpha-interferon injections. This report provides the results of calcitonin therapy. Materials and Methods: Ten patients received calcitonin therapy, 9 via subcutaneous injection and 1 via nasal spray, for the management of a CGCG. Patients were reviewed retrospectively RESULTS: In 8 cases, the lesions resolved completely after 19 to 21 months of subcutaneous calcitonin treatment. In the ninth case, the lesion resolved on calcitonin treatment only to reappear 26 months later. The recurrence was treated with both repeated calcitonin and local enucleation. The tenth case with calcitonin (intranasal) treatment was abandoned due to poor patient compliance, and the patient ultimately underwent surgical treatment. CONCLUSION: Calcitonin treatment appears to be a viable option for the treatment of CGCGs but, because of the length of treatment time, should probably be reserved for multiple lesions, recurrent lesions, or particularly aggressive lesions. The exact mechanism of action of both calcitonin and other treatment modalities remains to be fully elucidated. The reported success of all such treatments raises questions about the natural history of this lesion.  相似文献   
927.
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   
928.
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   
929.
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   
930.
An increase in chronic beryllium disease (CBD) has been suggested due to higher industrial use of beryllium alloys. Since occupational CBD is a perfect phenocopy of sarcoidosis, it might be misdiagnosed as sarcoidosis. In the current it was hypothesised that CBD exists in cohorts of sarcoidosis patients. In a prospective case study, sarcoidosis patients were evaluated for potential beryllium exposure. In those patients in whom beryllium exposure was confirmed and beryllium hypersensitivity demonstrated, the diagnosis of sarcoidosis was rejected and corrected to CBD. In 84 patients seen for re-evaluation or making a diagnosis of sarcoidosis, beryllium exposure was recognised and a diagnosis of CBD was made in 34 out of 84 patients. The time lag between clinical diagnosis of sarcoidosis and the final diagnosis of CBD ranged 0-18 yrs (median 3 yrs) and the mean (range) age at time of diagnosis of CBD was 43.9(25-80) yrs. Beryllium-contaminated workplaces causing disease encompassed a wide spectrum of industries and technical trades in which beryllium-exposure is generally not perceived as a health hazard. In conclusion, chronic beryllium disease still belongs to the spectrum of differential diagnoses of granulomatous disorders.  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