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   3659篇
  免费   191篇
  国内免费   62篇
耳鼻咽喉   10篇
儿科学   154篇
妇产科学   115篇
基础医学   378篇
口腔科学   33篇
临床医学   387篇
内科学   702篇
皮肤病学   146篇
神经病学   391篇
特种医学   448篇
外国民族医学   22篇
外科学   366篇
综合类   52篇
一般理论   3篇
预防医学   244篇
眼科学   20篇
药学   211篇
中国医学   5篇
肿瘤学   225篇
  2021年   36篇
  2020年   31篇
  2019年   53篇
  2018年   61篇
  2017年   37篇
  2016年   47篇
  2015年   49篇
  2014年   75篇
  2013年   111篇
  2012年   139篇
  2011年   132篇
  2010年   94篇
  2009年   116篇
  2008年   108篇
  2007年   141篇
  2006年   128篇
  2005年   114篇
  2004年   104篇
  2003年   97篇
  2002年   98篇
  2001年   91篇
  2000年   99篇
  1999年   98篇
  1998年   104篇
  1997年   101篇
  1996年   119篇
  1995年   77篇
  1994年   67篇
  1993年   67篇
  1992年   86篇
  1991年   74篇
  1990年   79篇
  1989年   95篇
  1988年   82篇
  1987年   73篇
  1986年   101篇
  1985年   84篇
  1984年   45篇
  1983年   35篇
  1982年   24篇
  1981年   30篇
  1979年   33篇
  1978年   41篇
  1977年   25篇
  1976年   39篇
  1975年   36篇
  1971年   26篇
  1970年   37篇
  1969年   26篇
  1968年   24篇
排序方式: 共有3912条查询结果,搜索用时 15 毫秒
61.
This study was designed to look at the differences in visuospatial abilities between boys and girls before they can speak fluently. At the mandatory two year follow up visit, children were given the opportunity to build a tower and a bridge. In children whose birth weight was > or = 2500 g, the capacity for erecting a tower was the same in both sexes, but for building a bridge striking differences were noted according to their sex. Among the 376 children of this category, 41 out of 199 boys (21%) were able to build a bridge in comparison with 15 out of 177 girls (8%). This difference is highly significant. In children whose birth weight was < or = 2500 g, no differences were noted either for building a tower or a bridge. By showing that boys outnumber girls among the most skilled toddlers in spatial abilities, this work confirmed the action of a male related factor on cerebral lateralisation.  相似文献   
62.
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   
63.
64.
OBJECTIVE: The ketogenic diet is a high-fat, low-protein, low-carbohydrate diet developed in the 1920s for the treatment of children with difficult to control seizures. Despite advances in both the pharmacotherapy and the surgery of epilepsy, many children continue to have difficult-to-control seizures. This prospective study sought to determine the ketogenic diet's effectiveness and tolerability in children refractory to today's medications. METHODS: One hundred fifty consecutive children, ages 1 to 16 years, virtually all of whom continued to have more than two seizures per week despite adequate therapy with at least two anticonvulsant medications, were prospectively enrolled in this study, treated with the ketogenic diet, and followed for a minimum of 1 year. Seizure frequency was tabulated from patients' daily seizure calendars and seizure reduction calculated as percentage of baseline frequency. Adverse events and reasons for diet discontinuation were recorded. RESULTS: The children (mean age, 5.3 years), averaged 410 seizures per month before the diet, despite an exposure to a mean of 6.2 antiepileptic medications. Three months after diet initiation, 83% of those starting remained on the diet and 34% had >90% decrease in seizures. At 6 months, 71% still remained on the diet and 32% had a >90% decrease in seizures. At 1 year, 55% remained on the diet and 27% had a >90% decrease in seizure frequency. Most of those discontinuing the diet did so because it was either insufficiently effective or too restrictive. Seven percent stopped because of intercurrent illness. CONCLUSIONS: The ketogenic diet should be considered as alternative therapy for children with difficult-to-control seizures. It is more effective than many of the new anticonvulsant medications and is well tolerated by children and families when it is effective.  相似文献   
65.
Scott HD  Bell J  Geller S  Thomas M 《JAMA》2000,283(1):99-104
In the current health care environment of competition and market forces, concern has arisen that the classic principle of serving disadvantaged persons may not be fulfilled due to pressures from managed care. Reach Out, a $12 million national program of the Robert Wood Johnson Foundation, was developed to recruit leaders from among practicing physicians to organize projects to care for the uninsured and underserved. Physician volunteerism was a key component of all projects. Thirty-nine Reach Out projects were implemented and carried out across the United States, with average funding per project of $300,000 distributed over a period of 4 years. Seven model types emerged, the most common of which, the free clinic and the referral network, accounted for two thirds of the total. At the program's conclusion, 199,584 patients were enrolled and 11,252 physicians recruited. Project execution was more complex than initially supposed, and major progress commonly was not evident until the third or fourth year, but at least two thirds of the projects are likely to continue with local support. With strong physician leadership and a funded administrative core, organized community efforts can develop and sustain an effective program. Programs such as Reach Out cannot solve the national problem of access to health care, but they can make a small but important impact on the number of uninsured and underserved persons without access to health care.   相似文献   
66.
Disentangling the Overlap between Tourette's Disorder and ADHD   总被引:11,自引:0,他引:11  
Objective : To identify similarities and differences in neuropsychiatric correlates in children with Tourette's syndrome (TS) and those with ADHD. Method : The sample consisted of children with Tourette's syndrome with ADHD( N = 79), children with Tourette's syndrome without ADHD ( N = 18), children with ADHD ( N = 563), psychiatrically referred children ( N = 212), and healthy controls ( N = 140). Results: Disorders specifically associated with Tourette's syndrome were obsessive compulsive disorder (OCD) and simple phobias. Rates of other disorders, including other disruptive behavioral, mood, and anxiety disorders, neuropsychologic correlates, and social and school functioning were indistinguishable in children with Tourette's and ADHD. However, children with Tourette's syndrome plus ADHD had more additional comorbid disorders overall and lower psychosocial function than children with ADHD. Conclusions: These findings confirm previously noted associations between Tourette's syndrome and OCD but suggest that disruptive behavioral, mood, and anxiety disorders as well as cognitive dysfunctions may be accounted for by comorbidity with ADHD. However, Tourette's syndrome plus ADHD appears to be a more severe condition than ADHD alone.  相似文献   
67.
Glycolysis is increased in cancer cells compared with normal cells. It has been shown that glucose enters cells via a family of five functional glucose transporters (GLUT). However, GLUT expression appears to be altered in human breast cancer, which may serve as a selective advantage and facilitate the metastatic potential of these cells. The relationship of GLUT isoform expression and breast cancer cell invasiveness has not been adequately addressed. Thus, the purpose of this study was to investigate whether an association exists between GLUT expression and human breast cancer cell invasiveness. Invasiveness of the human breast cancer lines MCF-7, MDA-MB-435 and MDA-MB-231 was measured using anin vitro assay and compared with cellular GLUT isoform expression, assessed by Western blot analysis and verified by immunohistochemistry in a poorly differentiated human ductal breast cancer. Cell surface GLUT-1 expression was associated with the invasive ability of MCF-7 (2.0 ± 0.02%), MDA-MB-435 (6.4 ±0.4%), and MDA-MB-231 (19.3 ± 2.0%). However, GLUT-2 and GLUT-5 were inversely associated with invasiveness; GLUT-3 expression was variable; and GLUT-4 was undetected. In a poorly differentiated human ductal breast cancer,in situ GLUT-1 staining was intense. GLUT-1 expression was associated with the in vitro invasive ability of human breast cancer cells which was validatedin situ. If this relationship is found to exist in a larger number of human breast cancer tissues, it may be possible to develop diagnostic and therapeutic strategies based on targeted GLUT isoform expression.  相似文献   
68.
69.
In this study we have analyzed the vascular response induced in the two- stage carcinogenesis model in SENCAR mice. The role of angiogenesis has not been explored in this model, which is the paradigm of multistage carcinogenesis and a model for neoplastic lesions derived from exophytic premalignant lesions (e.g. colon carcinoma, bladder papilloma). We investigated if angiogenesis is involved in the formation of papillomas and in the progression from papilloma to carcinoma. To this end we analyzed the vasculature of normal and hyperplastic skin, focal epidermal hyperplasias that are precursors of papillomas, papillomas at different stages and squamous cell carcinomas. We also analyzed the vascularization of papillomas induced in two strains of mice that differ in their susceptibility to malignant progression. We show here that angiogenesis is turned on in the earliest stages of papilloma formation. In late stages, regardless of state of progression, the predominant response is an increase in the size of blood vessels. Thus, in the SENCAR mouse model, representative of exophytic tumors, the angiogenesis switch is a very early event, probably mechanistically related to the development of the primarily exophytic lesions. Therefore, the density of blood vessels cannot be used as a predictor of malignant progression in this model.   相似文献   
70.
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