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   1631篇
  免费   100篇
  国内免费   61篇
耳鼻咽喉   11篇
儿科学   85篇
妇产科学   36篇
基础医学   204篇
口腔科学   29篇
临床医学   210篇
内科学   327篇
皮肤病学   49篇
神经病学   64篇
特种医学   285篇
外科学   180篇
综合类   42篇
预防医学   60篇
眼科学   12篇
药学   72篇
中国医学   2篇
肿瘤学   124篇
  2021年   15篇
  2019年   11篇
  2018年   22篇
  2017年   15篇
  2016年   14篇
  2015年   22篇
  2014年   27篇
  2013年   41篇
  2012年   50篇
  2011年   49篇
  2010年   32篇
  2009年   38篇
  2008年   42篇
  2007年   76篇
  2006年   32篇
  2005年   37篇
  2004年   34篇
  2003年   41篇
  2002年   30篇
  2001年   36篇
  2000年   36篇
  1999年   36篇
  1998年   59篇
  1997年   43篇
  1996年   67篇
  1995年   53篇
  1994年   52篇
  1993年   62篇
  1992年   39篇
  1991年   38篇
  1990年   47篇
  1989年   50篇
  1988年   63篇
  1987年   62篇
  1986年   42篇
  1985年   48篇
  1984年   33篇
  1983年   29篇
  1982年   22篇
  1981年   28篇
  1980年   24篇
  1979年   12篇
  1978年   20篇
  1977年   29篇
  1976年   14篇
  1975年   20篇
  1974年   11篇
  1973年   17篇
  1972年   16篇
  1970年   13篇
排序方式: 共有1792条查询结果,搜索用时 15 毫秒
1.
2.
3.
The Inter-Regional Epidemiological Study of Childhood Cancer (IRESCC) collected interview and medical information relating to the child's past medical experiences from parents of 555 children diagnosed with cancer and parents of 1110 unaffected matched controls. No significant associations emerged overall for ante-natal care, place and mode of delivery, length of gestation, birth weight, condition at birth, special care, neonatal procedures or breast-feeding. Few risk factors relating to previous illnesses and medication were found, although increasing numbers of illnesses appeared to be associated with an increased risk of childhood cancer, particularly acute lymphoblastic leukaemia. A highly significant excess of case children had not been immunised (p = 0.005). In general, these results indicate that past medical experiences have little influence on the development of cancer in children.  相似文献   
4.
5.
6.
The present study has been based on a detailed, computer-assisted, analysis of 112 astrocytomas from patients of all ages seen at The Radcliffe Infirmary between 1938 and 1984. There have been only six studies larger than the present one. From the results obtained in the present study, and the review of the literature, the following conclusions have been reached.Between 70 and 80010 of cerebellar astrocytomas are found in children. Few patients are less than 1 year of age or older than 40 at the time of diagnosis. There appear to be no age peaks. Prognosis is poorest at the extremes of life, children less than 5 years old tending to suffer an early recurrence and patients in the oldest age groups having not only a very rapid recurrence but also a very low overall survival rate.In the present study, there was a slight predominance of males although basically, when all studies are considered, the incidence appears to be equal amongst the sexes. Around puberty there appears to be an abrupt drop in the number of tumours in females and a concomitant rise in the number in males. There appears to be no relationship between sex and the length of survival.It would appear that cerebellar astrocytomas can begin either within the vermis or one hemisphere. There appears to be no laterality, the right and left sides of the cerebellum being affected equally. In the present study, the hemispheres were affected three times more frequently than the vermis (34.807o: 12.5010). The rate of recurrence is much faster with tumours of the vermis, whilst the length of survival to death is much longer with tumours of one hemisphere at least up to 10 years after surgery. The most rapid recurrences take place in tumours which involve both hemispheres and the vermis whilst the poorest survival is associated with tumours infiltrating the brain stem. The average length of history is 18.7 months, being under forty-eight months in approximately 60010 of patients, but only greater than 60 months in 6.201o of cases. The length of history was not related to either patient age or survival time.Most patients present with obstructive hydracephalus with or without localising symptoms. The presentation is usually chronic and intermittent but may also be acute. Symptoms generally appear only after much cerebellar tissue has been destroyed. Clinical features can be divided into four groups: those referrable to raised intracranial pressure; altered cerebellar function; visual disturbance; or cranial nerve dysfunction. Headache was found to be the most common symptom due to raised pressure and it was noted more commonly in the older patients. The rate of recurrence was slower in patients with headache, although their survival to death was not altered. Patients with raised pressure were also commonly noted to be drowsy. Drowsiness was more frequent in children than in adults but not associated with survival. Papillodoema was the most common sign referrable to raised pressure. Although it could not be related to survival, it is essential to relieve raised pressure rapidly in order to preserve vision. A substantial number of patients with large heads were noted in the present study. Ataxia was the most common sign referrable to altered cerebellar function, and found in up to 95°70 of all patients. It was more common in patients with tumours of the vermis than in those of the hemispheres, but was not related to survival. Visual disturbances, including nystagmus, diplopia, and reduced visual acuity, were more common in adults. They could not be related to survival. Cranial nerve palsies were not specifically assessed in the present study. Seventh nerve cranial palsies have been said, however, by others, to be the most reliable, localising sign in patients with cerebellar astrocytomas.  相似文献   
7.
Inversion recovery (IR), commonly considered a pulse sequence capable of producing T1-weighted images with excellent display of normal anatomy, is versatile: The null point and peak time provide a useful, succinct summary of the properties of IR and its capacity for producing both T1- and T2-weighted images. Shortening of the inversion time (TI) and creation of a short-TI inversion-recovery (STIR) pulse sequence increases sensitivity to malignancy and other abnormalities by making the effects of prolonged T1 and T2 on signal intensity additive and by nulling the signal from fat. The authors examined over 300 patients with various malignancies and compared STIR images with T1- and T2-weighted images obtained at 0.5 T. In 43 cases, signal-difference-to-noise ratios (SD/Ns) were calculated between tumor, fat, and muscle. In general, STIR images demonstrated tumor as a conspicuously high-intensity area in a background of muted, discernible anatomic detail. The good contrast achieved with STIR sequences between tumor and fat (SD/N = 18.1) and tumor and muscle (SD/N = 12.9) consolidated into a single image the information contained separately on T1- and T2-weighted images, which facilitates efficient detection and localization of malignancy.  相似文献   
8.
Goei  R; Baeten  C; Arends  JW 《Radiology》1988,168(2):303-306
Sixteen cases of histopathologically proved solitary rectal ulcer syndrome were encountered. Fifteen patients underwent barium enema study; in nine cases the findings--including rectal stricture, granularity of the mucosa, and thickened rectal folds-were nonspecific. In six cases the study was normal. All patients had a long history of defecation disorders, and defecography was performed in all. In seven cases, intussusception of the rectal wall was seen; in another case the intussusception was accompanied by a rectocele. One case showed rectal prolapse. In four cases, failed relaxation of the puborectalis occurred and prevented the passage of the bolus; in another case there was abnormal perineal descent. In two patients studies were normal. In patients with defecation disorders, the possibility of this syndrome should be considered. Defecography is the method of choice for establishing the diagnosis.  相似文献   
9.
The onset, duration, and offset of pemoline action to improve cognitive performance is examined intensively in 25 prepubescent males suffering from attention-deficit disorder with hyperactivity (ADDH). The purpose was to characterize the pharmacodynamics of pemoline in ADDH patients through correlation of plasma pemoline concentration with psychometric measures of memory search efficiency and paired-associates learning, with the physiological effect of pemoline on dopaminergic transmission concurrently measured by analysis of plasma prolactin response. The effect of pemoline on neuroprocessing is apparent within the first 2 hours after administration with an inverse relationship between plasma pemoline and prolactin concentration present at hour one only (r = 0.84; p = 0.005). Pemoline therapy for 3 weeks does not significantly affect area under the curve for pemoline or prolactin nor did the effect on memory search efficiency decrease, suggesting no apparent tolerance.  相似文献   
10.
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