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   2288篇
  免费   122篇
  国内免费   77篇
耳鼻咽喉   26篇
儿科学   91篇
妇产科学   40篇
基础医学   252篇
口腔科学   44篇
临床医学   248篇
内科学   461篇
皮肤病学   48篇
神经病学   108篇
特种医学   346篇
外科学   253篇
综合类   42篇
一般理论   1篇
预防医学   234篇
眼科学   44篇
药学   109篇
中国医学   3篇
肿瘤学   137篇
  2021年   17篇
  2019年   21篇
  2018年   22篇
  2016年   19篇
  2015年   22篇
  2014年   37篇
  2013年   44篇
  2012年   74篇
  2011年   72篇
  2010年   56篇
  2009年   65篇
  2008年   52篇
  2007年   112篇
  2006年   58篇
  2005年   72篇
  2004年   65篇
  2003年   58篇
  2002年   58篇
  2001年   54篇
  2000年   62篇
  1999年   48篇
  1998年   102篇
  1997年   79篇
  1996年   70篇
  1995年   54篇
  1994年   50篇
  1993年   52篇
  1992年   56篇
  1991年   46篇
  1990年   67篇
  1989年   62篇
  1988年   62篇
  1987年   58篇
  1986年   53篇
  1985年   55篇
  1984年   35篇
  1983年   32篇
  1982年   29篇
  1981年   19篇
  1980年   20篇
  1979年   29篇
  1978年   19篇
  1977年   28篇
  1976年   21篇
  1975年   21篇
  1972年   19篇
  1971年   20篇
  1969年   14篇
  1968年   15篇
  1947年   14篇
排序方式: 共有2487条查询结果,搜索用时 15 毫秒
51.
Auricular infections caused by high ear piercing in adolescents   总被引:1,自引:0,他引:1  
  相似文献   
52.
Since the development of coronary heart disease (CAD) is affected by a specific pattern of plasma high density lipoprotein (HDL) effects it may be useful to know whether this occurs already in childhood. In this study we evaluated particle size distribution of HDL by gradient gel electrophoresis and the determination of cholesterol esterification rate (FERHDL) in plasma depleted of apo B lipoproteins in 221 children (108 boys and 113 girls) aged 4 months to 20 years. Total plasma- (TC), low-density lipoprotein- (LDL-C) and HDL- (HDL-C) cholesterol, HDL unesterified cholesterol (HDL-UC) and plasma triglycerides (TG) were also measured. There were no significant gender and age differences with respect to the plasma TC, LDL-TC and TG but concentration of HDL-TC increased with age. Post-pubertal girls had significantly higher relative concentrations of HDL2b compared to boys (30.4% vs 17.2%), while HDL3b,c was lower in post-pubertal girls (8.7% vs. 16.5 %). FERHDL correlated inversely with HDL2b and positively with HDL3b,c particles and was significantly higher in boys of the post-pubertal group compared to girls (16.9%/h vs 12.5%/h). While in girls there was a positive correlation between age and HDL-C, HDL-UC and the relative concentration of HDL2b no significant correlation were observed in boys. In girls the increase in TC showed a significant correlation with a simultaneous increase in HDL-C, HDL-UC and HDL2b. In boys TC correlated significantly with changes in TG only. When HDL2b and HDL3b,c cholesterol levels are calculated from HDL-C concentration and per cent distribution the differences between males and females are further emphasized. These data indicate that HDL particle size distribution is age- and gender-dependent.  相似文献   
53.
Persistent hyperinsulinemic hypoglycaemia of infancy (PHHI) is the most frequent cause of hypoglycaemia in infancy. Clinical presentation is heterogeneous, with variable onset of hypoglycaemia and response to diazoxide, and presence of sporadic or familial forms. Underlying histopathological lesions can be focal or diffuse. Focal lesions are characterised by focal hyperplasia of pancreatic islet-like cells, whereas diffuse lesions implicate the whole pancreas. The distinction between the two forms is important because surgical treatment and genetic counselling are radically different. Focal lesions correspond to somatic defects which are totally cured by limited pancreatic resection, whereas diffuse lesions require a subtotal pancreatectomy exposing to high risk of diabetes mellitus. Diffuse lesions are due to functional abnormalities involving several genes and different transmission forms. Recessively inherited PHHI have been attributed to homozygote mutations for the beta-cell sulfonylurea receptor (SUR1) or the inward-rectifying potassium-channel (Kir6.2) genes. Dominantly inherited PHHI can implicate the glucokinase gene, particularly when PHHI is associated with diabetes, the glutamate dehydrogenase gene when hyperammonaemia is associated, or another locus.  相似文献   
54.
55.
BACKGROUND: The National Acute Spinal Cord Injury Studies have been a series of trials assessing the role of pharmacologic agents in the prevention of secondary neuronal damage after acute spinal cord injury. METHODS: The trials were multicenter randomized, controlled studies. RESULTS: Two trials have demonstrated the efficacy of high-dose methylprednisolone in improving neurologic and functional recovery and have shown a reassuring safety profile. CONCLUSION: This study responds to a recent commentary on these trials and examines in particular the roles of clinical measurement, statistical analysis, and risk benefit in assembling evidence for or against innovative therapies.  相似文献   
56.
The aims were to determine the median survival and prognostic factors of patients with central nervous system (CNS) metastases managed with whole‐brain radiation therapy (WBRT), and to explore selection criteria in recently published clinical trials using aggressive interventions in CNS metastases. A retrospective audit was performed on patients managed with WBRT for CNS metastases. Potential prognostic factors were recorded and analysed for their association with survival duration. The proportion of patients with these factors was also compared with those of patients managed under three recently reported studies investigating aggressive interventions, such as radiosurgery and chemotherapy for CNS metastases. Seventy‐three patients were treated with WBRT for cerebral metastases over a 12‐month period. The median survival of the population was 3.4 months (95% confidence interval: 2.7–4.1), with 6‐ and 12‐month survival rates of 30 and 18%, respectively. Significant prognostic factors for prolonged median survival were Eastern Cooperative Oncology Group status 0–2 (P = 0.015), Medical Research Council neurological functional status 0–1 (P = 0.006), and Recursive Partitioning Analysis Class 2 versus Class 3 (P = 0.020). On multivariate analysis, younger patient age (P = 0.02) and better performance status (P < 0.01) were associated with improved outcome. When comparing these characteristics with selected published studies, our study cohort demonstrated a higher proportion of patients with poor performance status, a greater number of metastases per patient and a higher incidence of extracranial disease. This reflects the selected nature of patients in these published studies. Central nervous system metastases confer a poor prognosis and, for the majority of patients, aggressive interventions are unlikely to improve survival. The use of potentially toxic and expensive treatments should be reserved for those few in whom these studies have shown a potential benefit.  相似文献   
57.
Abstract: Melatonin is a synchronizer of many physiological processes. Abnormal melatonin signaling is associated with human disorders related to sleep, metabolism, and neurodevelopment. Here, we present the X‐ray crystal structure of human N‐acetyl serotonin methyltransferase (ASMT), the last enzyme of the melatonin biosynthesis pathway. The polypeptide chain of ASMT consists of a C‐terminal domain, which is typical of other SAM‐dependent O‐methyltransferases, and an N‐terminal domain, which intertwines several helices with another monomer to form the physiologically active dimer. Using radioenzymology, we analyzed 20 nonsynonymous variants identified through the 1000 genomes project and in patients with neuropsychiatric disorders. We found that the majority of these mutations reduced or abolished ASMT activity including one relatively frequent polymorphism in the Han Chinese population (N17K, rs17149149). Overall, we estimate that the allelic frequency of ASMT deleterious mutations ranges from 0.66% in Europe to 2.97% in Asia. Mapping of the variants on to the 3‐dimensional structure clarifies why some are harmful and provides a structural basis for understanding melatonin deficiency in humans.  相似文献   
58.
59.
The Tiredness Management Guide (TMG), developed by N. W. Troy and P. Dialgas-Pelish (1995), consists of 59 interventions that may be helpful in decreasing maternal fatigue in the postpartum period. The purpose of this pilot study was to evaluate which interventions mothers perceived as most helpful and thus reduce the length of the TMG and update its relevance. A convenience sample of 30 Women, Infants, and Children Program (WIC) participants between the ages of 18 and 35 years completed a demographic tool and the TMG. The 25 most helpful interventions can be placed into the following broad categories: rest and relaxation, time management, rearranging usual activities, relief/prevention of hemorrhoids/constipation, signs of infection, and emotional support.  相似文献   
60.
Background and Aim: Little is known about the causes of overt obscure gastrointestinal bleeding (OGIB) in patients using anti‐thrombotic therapy. We aimed to describe video capsule endoscopy (VCE) findings and to identify factors associated with positive findings in these patients. Methods: We carried out a retrospective study of 56 patients who underwent VCE for evaluation of previous overt OGIB during anti‐thrombotic therapy. VCE studies were re‐evaluated by a gastroenterologist blinded to clinical details. Clinical data included in the multivariate analysis were sex, age, indication for and type of anti‐thrombotic therapy, hemodynamic instability on admission, type of blood loss, hemoglobin on admission, use of a proton pump inhibitor, NSAID use, time between bleeding episodes and VCE, and whether or not anti‐thrombotic therapy was resumed before the VCE study. Results: A probable cause for gastrointestinal bleeding was identified in 28 (50%) of the 56 studies. Angiodysplasia was found in 19 patients. Twenty‐two studies showed a possible cause in the small bowel. Multivariate logistic regression analysis showed that reinstitution of anti‐thrombotic therapy before VCE was carried out was the only independent predictor of positive VCE findings (OR: 8.61, 95% CI: 1.20–60.42, P = 0.032). Conclusions: Small intestinal angiodysplasia was the most common cause for overt OGIB. Reinstitution of withdrawn anti‐thrombotic drugs before the VCE examination was carried out was associated with positive VCE findings in multivariate analysis.  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