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   287245篇
  免费   10390篇
  国内免费   939篇
耳鼻咽喉   3944篇
儿科学   9629篇
妇产科学   7192篇
基础医学   37001篇
口腔科学   8000篇
临床医学   24312篇
内科学   55370篇
皮肤病学   5970篇
神经病学   20533篇
特种医学   14376篇
外国民族医学   98篇
外科学   44632篇
综合类   1863篇
一般理论   195篇
预防医学   22582篇
眼科学   6076篇
药学   19114篇
  2篇
中国医学   278篇
肿瘤学   17407篇
  2022年   1559篇
  2021年   3356篇
  2020年   1933篇
  2019年   2869篇
  2018年   6673篇
  2017年   6079篇
  2016年   5574篇
  2015年   7488篇
  2014年   7998篇
  2013年   8211篇
  2012年   17071篇
  2011年   12155篇
  2010年   6284篇
  2009年   7367篇
  2008年   8205篇
  2007年   8705篇
  2006年   8753篇
  2005年   16673篇
  2004年   17601篇
  2003年   12822篇
  2002年   7633篇
  2001年   4906篇
  2000年   2145篇
  1999年   6480篇
  1998年   1387篇
  1992年   7212篇
  1991年   7410篇
  1990年   7628篇
  1989年   7221篇
  1988年   6750篇
  1987年   6491篇
  1986年   6234篇
  1985年   5521篇
  1984年   3939篇
  1983年   3216篇
  1982年   1338篇
  1979年   3978篇
  1978年   2554篇
  1977年   1962篇
  1976年   1689篇
  1975年   2607篇
  1974年   3233篇
  1973年   2847篇
  1972年   2857篇
  1971年   2834篇
  1970年   2624篇
  1969年   2519篇
  1968年   2286篇
  1967年   2194篇
  1966年   1946篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Previous studies indicate that HPV type 16 and 18 (HPV) are associated with squamous cell carcinoma of the head and neck. In this investigation we evaluate in our hospital 253 patients with oral squamous cell carcinoma of the tongue not related to tobacco or alcohol with a tumor index of T2 NO MO between 1981 and 1991. From 12 patients we were able to obtain tissue. For detection of human papilloma virus, DNA sequences 6, 11, 16, 18, 31 and 33 in paraffin-embedded human tissue biopsies a non-radioactive in situ hybridization procedure was utilized. Approximately 60% of the carcinoma of the tongue are positive for episomal viral DNA 6, 11, 16 and 18. These results confirms that HPV infection may play a possible role in the multifactorial etiology of carcinogenesis of squamous cell carcinoma of the tongue and probably acting synergistically with other carcinogenesis.  相似文献   
982.
The concentration of alpha-tocopherol was measured in liver biopsy specimens obtained from 83 patients with alcoholic and non-alcoholic liver diseases. The mean hepatic vitamin E content (as alpha-tocopherol) was significantly lower in 23 patients with alcoholic cirrhosis (17.6 +/- 12.1 nmol/mg wet weight liver), compared with 12 patients with normal liver histology (39.2 +/- 29.7 nmol/mg, P less than 0.01). The mean serum concentration of alpha-tocopherol was lower in patients with alcoholic cirrhosis (13.9 +/- 7.0 mumol/l) than in individuals with alcoholic fatty liver (21.3 +/- 9.3 mumol/l, P less than 0.01) and patients with normal liver histology (23.4 +/- 11.6 mumol/l, P less than 0.01). A decreased ratio of serum alpha-tocopherol/total serum lipids was also observed in patients with alcoholic cirrhosis, compared with patients with normal liver histology (P less than 0.05). There was a significant correlation between concentrations of alpha-tocopherol in liver and serum (r = 0.43, P less than 0.001). Furthermore, serum alpha-tocopherol correlated with retinol (r = 0.53, P less than 0.001), selenium (r = 0.45, P less than 0.001), and albumin (r = 0.37, P less than 0.001) in serum. We suggest that the reduced content of hepatic alpha-tocopherol observed in some patients may play a role in ethanol-induced lipid peroxidation.  相似文献   
983.
In a retrospective study of 28 women and eight men with squamous cell metaplasia in different parts of the bladder, including the trigone, no histopathological differences were observed among the regions. All the five (female) patients with parakeratosis had a concomitant invasive bladder tumour. Thirty-eight% of all the patients had a simultaneous neoplastic tumour. The metaplastic lesions were investigated for keratin in 13 patients, and all were positive. In seven out of eight patients, the urothelium adjacent to the squamous cell metaplasia was also positive for keratin, indicating a direct transformation of the urothelium to squamous cell epithelium. The metaplastic cells were investigated for oestrogen receptors in five men and five women, and all were negative, suggesting no relationship between estrogens and squamous cell metaplasia of the bladder. Squamous cell metaplasia in the bladder is not considered a premalignant condition. However, metaplasia and neoplastic tumours are often associated with chronic tissue damage, and the presence of metaplasia may give a warning of conditions that can also cause cancer.  相似文献   
984.
Fifty renal biopsies were studied by immunoelectron microscopy after embedding in a partly hydrophilic polyacrylic resin (LR White). Immunofluorescence studies were carried out on frozen sections of parallel tissue samples. Polyacrylic embedding gave good preservation of the renal ultrastructure and precise localization of immunoglobulin and C3c antibodies within glomerular electron-dense deposits. Non-specific staining of plasma proteins within vascular lumina could easily be detected. There was good correlation between immunoelectron and immunofluorescence microscopy. Immunoelectron microscopy is a very sensitive method, which can detect small amounts of antigen. More cases were, however, positive by immunofluorescence than by immunoelectron microscopy. This discrepancy may be explained by difference in sample size, and by difference in resolution of morphological details (electron microscopy versus fluorescence microscopy).  相似文献   
985.
This prospective study examined the influence of long-term amiodarone therapy on the parameters of the signal-averaged ECG and their relation to simultaneously derived Holter monitoring data. For this purpose, 23 patients with angiographically confirmed dilated cardiomyopathy or coronary heart disease and high-grade ventricular arrhythmias, in whom an average of four class I antiarrhythmic drugs had proven ineffective, were stabilized on amiodarone. Before the beginning of therapy, as well as after 2 months and, subsequently, every 3 months, a resting ECG, a signal-averaged ECG by Simson's method, and Holter monitoring were performed. Compared to the initial measurement, we found a significant increase in the duration of the total filtered QRS complex from an average of 114 +/- 24 ms to 127 +/- 35 ms, while the change in voltage did not reach the significance level. The incidence of late potentials remained largely constant under amiodarone; 10 patients showed a constant late potential, 12 patients had no late potential, and one patient with coronary heart disease developed a new late potential. In the long-term follow-up, we ascertained a relatively high responder rate under amiodarone between 41% and 81%. No relation could be detected between the results of the signal-averaged ECG and those of 24-h Holter monitoring.  相似文献   
986.
In Hungary valve replacement is still a major indication for heart surgery in adults. In the Cardiovascular Surgical Clinic of Semmelweis Medical University of Budapest from 1976 to 1990 2435 patients were operated for valve disease. Majority of the cases had single (aortic n = 856, mitral n = 912) or double (aortic + mitral n = 513) valve replacement. Over this 15 years period there have been many alterations in patients characteristics and surgical technique as well. In spite of the increasing mean age of patients the operative mortality has decreased (in the last 5 years period it was 2.7%, 5.5% and 7.9% in the three groups respectively). At the same time the number of patients requiring valve re-replacement or combined valve + coronary procedure has increased. The use of bioprosthetic valves has fallen below 10 percent from the 60--80 percent observed between 1976--1980. The analysis showes excellent surgical results in the field of valve replacement in Hungary.  相似文献   
987.
The neutron capture reaction 10B(1n,4He)7Li produces two energetic particles, 4He2+ and 7Li3+ that are strongly cell toxic. Due to the short range of these nuclear fragments (5-9 microns) mainly those cells that have bound or internalized a 10B-containing substance are growth-inactivated. The most critical and difficult step in an efficient boron neutron capture therapy (BNCT) is the tumour targeting. It is today possible to synthesize a large number of boron compounds and conjugate them to tumour-seeking macromolecules, such as monoclonal antibodies or different polypeptides. The boron-containing substances presently considered for therapy are sulfhydryl boron hydride (BSH) and boron-phenylalanine, (BPA) for the treatment of gliomas and malignant melanomas respectively. Other boronated compounds considered are ligands for receptor-amplified tumour cells, antibodies for tumour cells with specific antigens and thioureas for treatment of melanotic melanomas. The required boron concentration is given by the relative dose due to neutron capture in 10B and that of the competing capture reactions in nitrogen and hydrogen. Capture in nitrogen produces protons with a range of about 10-11 microns and this gives a radiation dose to all cells in the neutron activated area. Calculations show that the local concentration of 10B near the critical radiation target, DNA, must be higher than 10 ppm (10 micrograms/g). Increased emphasis will be put on the development of combinations of treatments that fulfil the requirements for attacking the microscopic spread of the tumour.  相似文献   
988.
989.
During a period of 20 weeks 18 female patients with fibromyalgia participated in a 60-minute exercise program twice a week. A control group, comprising 17 patients, was told not to change their physical activity level. Eleven patients in the training group and fourteen in the control group completed the study. The results at entry were compared to those after 20 weeks, as well as being compared to the results of the control group. No statistically significant changes or differences in general pain, pain coping and fatigue were seen after 20 weeks. Improved dynamic endurance work performance for the upper extremity was found, however, in the training group, measured as the strength of the first (p = 0.01) and the last repetition (p = 0.003). These results differed from the results of the control group (p = 0.02 and p = 0.003). It is concluded that fibromyalgia patients may undergo low-intensity dynamic endurance training without experiencing exacerbation of their general pain and fatigue symptoms.  相似文献   
990.
Changes in whole blood viscosity associated with hematocrit could be one of the pathways along which the cardiovascular disease (CVD) risk factors affect these diseases. Therefore, we studied in a nationwide survey comprising 514 apparently healthy Dutch elderly men and women aged 65-79 the possibility of any association between hematocrit and CVD risk factors (tobacco smoking, serum cholesterol, body mass index and blood pressure). Among men, diastolic blood pressure and total serum cholesterol were positively associated with hematocrit in both bivariate and multivariate regression analysis, whereas positive associations of hematocrit with body mass index and smoking were only significant (p < 0.05) in bivariate analysis. Among women, hematocrit was positively associated with body mass index and smoking. Except for smoking, which was associated with the mean corpuscular volume of the erythrocytes, hematocrit was positively correlated with hemoglobin and the number of erythrocytes. It is concluded that hemorrheological aspects should be considered when studying CVD among elderly people.  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