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   21252篇
  免费   1407篇
  国内免费   88篇
耳鼻咽喉   144篇
儿科学   668篇
妇产科学   500篇
基础医学   3379篇
口腔科学   404篇
临床医学   2097篇
内科学   4201篇
皮肤病学   460篇
神经病学   2240篇
特种医学   514篇
外科学   1951篇
综合类   118篇
一般理论   27篇
预防医学   2247篇
眼科学   369篇
药学   1242篇
中国医学   38篇
肿瘤学   2148篇
  2023年   187篇
  2022年   344篇
  2021年   640篇
  2020年   424篇
  2019年   606篇
  2018年   686篇
  2017年   530篇
  2016年   609篇
  2015年   692篇
  2014年   841篇
  2013年   1186篇
  2012年   1682篇
  2011年   1668篇
  2010年   947篇
  2009年   840篇
  2008年   1471篇
  2007年   1409篇
  2006年   1284篇
  2005年   1237篇
  2004年   1085篇
  2003年   1113篇
  2002年   968篇
  2001年   132篇
  2000年   93篇
  1999年   126篇
  1998年   184篇
  1997年   152篇
  1996年   123篇
  1995年   123篇
  1994年   104篇
  1993年   102篇
  1992年   60篇
  1991年   70篇
  1990年   50篇
  1989年   47篇
  1988年   30篇
  1987年   45篇
  1986年   48篇
  1985年   56篇
  1984年   55篇
  1983年   46篇
  1982年   70篇
  1981年   53篇
  1980年   45篇
  1979年   42篇
  1978年   34篇
  1976年   30篇
  1975年   28篇
  1974年   33篇
  1973年   28篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Our aim was to study the effects of mildly flavoured sodium lauryl sulphate (SLS)-containing and detergent-free toothpastes with and without betaine (BET) on subjective symptoms of dry mouth in a randomised clinical trial. BET is an osmoprotectant that reacts with molecules to supply the surface with a water coating that protects cells from surfactants. Twenty-seven xerostomic patients and 18 healthy controls took part in the randomised, double-blind clinical trial with a crossover design. Three mildly flavoured toothpastes: (1) 4% BET, (2) 1% SLS and 4% BET, and (3) 1% SLS were used for six weeks each. The reference or washout paste contained neither SLS nor BET. The subjects' dental appointments were at the beginning of the trial and before and after the use of each toothpaste. At each appointment, the subjects were interviewed about subjective sensations of dry mouth (Visual Assessment Scoring (VAS) Index). The subjects did not report any adverse effects in connection with the use of the toothpastes. The VAS scores for lip dryness and eating difficulties were significantly lower for the BET paste (lip dryness: BET相似文献   
992.
The purpose of this study was to evaluate the age-related differences in the incidence, length and topographic location of ossification in the stylohyoid chain. Panoramic radiographs of 420 patients (795 reviewed stylohyoid-chains), subdivided into 4 age groups (20 years and under, 21 to 40 years, 41 to 60 years, older than 60 years) were reviewed and examined for the incidence, length and topographic location of stylohyoidal ossification. 245 (30.8%) out of 795 reviewed stylohyoidal chains showed radiological variabilities (elongation of the styloid process and/or ossification of the stylohyoid ligament). With increasing age, there was an increase in the incidence and length of stylohyoidal ossifications (p<0.01). A significant linear correlation between the length of the stylohyoidal ossifications and age was only found in the young age group (under 20 yrs.; p<0.01). In the young age group (under 20 yrs), there was also a higher prevalence of isolated locations in the superior stylohyoidal segment. With increasing age, there was a pronounced presence of ossifications in the middle and inferior stylohyoid segments and combinations of ossified variabilities. Stylohyoidal ossifications show age-related differences in incidence, length and topographical location. Stylohyoid ossifications gain a different importance in adult patients than in juvenile patients.  相似文献   
993.
Lung cancer screening: a different paradigm   总被引:2,自引:0,他引:2  
Thoracic computed tomography (CT) is a sensitive method for detecting early lung cancer but has a high false-positive rate and is not sensitive for detecting central preinvasive and microinvasive cancer. Our hypothesis was that automated quantitative image cytometry (AQC) of sputum cells as the first screening method may improve detection rate by identifying individuals at highest risk for lung cancer. A total of 561 volunteer current or former smokers 50 years of age or older, with a smoking history of more than or equal to 30 pack/years, were studied. Among these, 423 were found to have sputum atypia defined as five cells or more with abnormal DNA content using AQC. Noncalcified pulmonary nodules were found in 46% (259/561). Of the 14 detected cancers, 13 were detected in subjects with sputum atypia-nine by CT and four carcinoma in situ/microinvasive cancers by autofluorescence bronchoscopy. One cancer was detected by CT alone. AQC of sputum cells improved the detection rate of lung cancer from 1.8 to 3.1%. CT scan alone would have missed 29% of the cancers. This screening paradigm shift has the additional potential of reducing the number of initial CT scans by at least 25% with further savings in follow-up investigations and treatment.  相似文献   
994.
Pregnancy rhinitis is defined as nasal congestion in the last 6 or more weeks of pregnancy, without other signs of respiratory tract infection and with no known allergic cause, with complete resolution of symptoms within 2 weeks after delivery. Pregnancy rhinitis occurs in approximately one-fifth of pregnancies, can appear at almost any gestational week, and affects the woman and possibly also the fetus. The pathogenesis of pregnancy rhinitis is not clear, but placental growth hormone is suggested to be involved. Smoking and sensitization to house dust mites are probable risk factors. It is often difficult to make a differential diagnosis from sinusitis: nasendoscopy of a decongested nose is the diagnostic method of choice. In some cases ultrasound or x-ray may be necessary. Sinusitis should be treated aggressively with increased doses of beta-lactam antibiotics and antral irrigation. Nasal decongestants give good temporary relief from pregnancy rhinitis, but they tend to be overused, leading to the development of rhinitis medicamentosa. Corticosteroids have not been shown to be effective in pregnancy rhinitis, and their systemic administration should be avoided during pregnancy. Nasal corticosteroids may be administered to pregnant women when indicated for other sorts of rhinitis. Nasal alar dilators and saline washings are safe means to relieve nasal congestion, but the ultimate treatment for pregnancy rhinitis remains to be found.  相似文献   
995.
Cold agglutinin immunohaemolytic anaemia (CAIA) responds poorly to standard treatment. We report a case of marginal zone lymphoma complicated by CAIA that responded to rituximab after failing to respond to corticosteroids and chlorambucil.  相似文献   
996.
BACKGROUND: Although CD34 progenitors play a crucial role during bone marrow transplantation (BMT), there is only scant knowledge concerning their lineage-restricted mixed chimerism (MCh). METHODS: An immunohistochemical and fluorescence in situ hybridization study was performed on bone marrow biopsies derived from 11 patients with chronic myelogenous leukemia after sex-mismatched BMT to quantify the CD34 cell population and their expression. After proper identification by a lineage-specific monoclonal antibody, X chromosome- and Y chromosome-specific probes were used for sex typing and for labeling of the locus commercially available detection systems were applied. RESULTS: After successful engraftment, 241 progenitor cells were identified at days 9 to 586 of the posttransplant period. Overall incidence of MCh was 24% with a tendency to decline after day 100 to 15%. The gene was detectable in only 10% of these precursors and decreased to less than 4% after more than 6 months. Approximately 0.5 to 5.5 years after BMT in six patients, a manifest leukemic relapse occurred, which was accompanied by a conversion of donor-to-host-type progenitors. This phenomenon involved up to 94% of the 303 evaluable CD34 cells and also included a retrieval of the translocation gene in approximately 50% of this population. CONCLUSION: The lineage-restricted MCh of progenitors after BMT is in keeping with the assumption that leukemic (bcr/abl ) precursors represent only a fraction of the total host-derived (chimeric) CD34 cells. These residual clonally transformed progenitors survive myeloablative treatment and thus may be the source for a later relapse.  相似文献   
997.
Data from the US population-based Third National Health and Nutrition Examination Survey, conducted from 1988 to 1994, were used to estimate the population prevalence, prevalence odds ratios, and attributable fractions for the association of chronic obstructive pulmonary disease (COPD) with employment by industry and occupation. The aim was to identify industries and occupations at increased risk of COPD. COPD was defined as forced expiratory volume in 1 second (FEV(1))/forced vital capacity <70% and FEV(1 )<80% predicted. The authors used SUDAAN software (Research Triangle Institute, Research Triangle Park, North Carolina) to estimate the weighted population prevalence and odds ratios using 9,823 subjects aged 30-75 years who underwent lung function tests. Odds ratios for COPD, adjusted for age, smoking status, pack-years of smoking, body mass index, education, and socioeconomic status, were increased for the following industries: rubber, plastics, and leather manufacturing; utilities; office building services; textile mill products manufacturing; the armed forces; food products manufacturing; repair services and gas stations; agriculture; sales; construction; transportation and trucking; personal services; and health care. Occupations associated with increased odds ratios for COPD were freight, stock, and material handlers; records processing and distribution clerks; sales; transportation-related occupations; machine operators; construction trades; and waitresses. The fraction of COPD attributable to work was estimated as 19.2% overall and 31.1% among never smokers.  相似文献   
998.
The authors investigated the association between changes in smoking habits and mortality by pooling data from three large cohort studies conducted in Copenhagen, Denmark. The study included a total of 19,732 persons who had been examined between 1967 and 1988, with reexaminations at 5- to 10-year intervals and a mean follow-up of 15.5 years. Date of death and cause of death were obtained by record linkage with nationwide registers. By means of Cox proportional hazards models, heavy smokers (>or=15 cigarettes/day) who reduced their daily tobacco intake by at least 50% without quitting between the first two examinations and participants who quit smoking were compared with persons who continued to smoke heavily. After exclusion of deaths occurring in the first 2 years of follow-up, the authors found the following adjusted hazard ratios for subjects who reduced their smoking: for cardiovascular diseases, hazard ratio (HR) = 1.01 (95% confidence interval (CI): 0.76, 1.35); for respiratory diseases, HR = 1.20 (95% CI: 0.70, 2.07); for tobacco-related cancers, HR = 0.91 (95% CI: 0.63, 1.31); and for all-cause mortality, HR = 1.02 (95% CI: 0.89, 1.17). In subjects who stopped smoking, most estimates were significantly lower than the heavy smokers'. These results suggest that smoking reduction is not associated with a decrease in mortality from tobacco-related diseases. The data confirm that smoking cessation reduces mortality risk.  相似文献   
999.
INTRODUCTION: A clinical diagnosis of I-cell disease was established in an infant with coarse face, hyperplastic gums, severe growth deficiency, skeletal deformities and retarded psychomotor development. PATIENT/METHOD: Albeit, enzyme measurements in our patient leukocytes and serum including arylsulfatase, hexosaminidase, alpha-fucosidase, iduronate-sulphatase and beta-galactosidase showed no significant alteration, in serum an increased activity of beta-glucuronidase was detected. Enzyme studies in fibroblasts showed an abnormal intracellular/extracellular distribution of enzyme activities, and significantly decreased activity of UDP-N-acetylglucosamine-1-phosphotransferase confirming the diagnosis of I-cell disease. RESULTS/DISCUSSION: In the mother's next pregnancy at 15th week of gestation lysosomal enzyme activities were determined in amniotic fluid and cultured amniotic cells, and the diagnosis of an unaffected fetus was established. Based on our experience we suggest the use of cell cultures for the diagnostics of this rare disease.  相似文献   
1000.
Azithromycin (Zithromax, Pfizer Inc., New York, NY, USA) is effective in the control of blinding trachoma. Community-based azithromycin treatment is recommended by the World Health Organization as part of a multipronged strategy aimed at the global elimination of binding trachoma by the year 2020. Paediatric trachoma is treated with azithromycin according to weight at a target dosage of 20 mg/kg. However, conventional weight-based treatment may be problematic in the field due to the logistical difficulties associated with weight scales. We assessed the accuracy of using height as a proxy for weight to determine azithromycin treatment in 4 countries--Viet Nam, Tanzania, Ghana, and Mali--where mass treatment programmes are underway. Population-based data collected from 1988 to 2000 were analysed using least squares regression. Height treatment schedules were developed for each data set. The accuracy of each schedule was evaluated according to the percentage of children receiving treatment within a dosage range of 20-30 mg/kg, a conservative estimate of the safe and effective treatment range for paediatric trachoma. Using height to determine dose, 89-95% of children would receive a dosage of 20-30 mg/kg. In these populations, height-based treatment is a reliable alternative to conventional weight-based treatment. Methods for developing height schedules presented in this analysis could be applied to other regions and therapeutics.  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