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   1582112篇
  免费   323796篇
  国内免费   39945篇
耳鼻咽喉   22038篇
儿科学   44229篇
妇产科学   40759篇
基础医学   261716篇
口腔科学   42516篇
临床医学   164425篇
内科学   344066篇
皮肤病学   34709篇
神经病学   127556篇
特种医学   62555篇
外国民族医学   435篇
外科学   247139篇
综合类   80556篇
现状与发展   6篇
一般理论   439篇
预防医学   128964篇
眼科学   48874篇
药学   155149篇
  7篇
中国医学   49694篇
肿瘤学   90021篇
  2019年   21422篇
  2018年   25800篇
  2017年   24243篇
  2016年   23883篇
  2015年   24993篇
  2014年   29672篇
  2013年   38224篇
  2012年   46086篇
  2011年   49624篇
  2010年   37438篇
  2009年   43701篇
  2008年   46029篇
  2007年   45885篇
  2006年   45946篇
  2005年   44593篇
  2004年   45698篇
  2003年   43925篇
  2002年   43505篇
  2001年   74275篇
  2000年   72068篇
  1999年   66495篇
  1998年   26694篇
  1997年   24901篇
  1996年   24774篇
  1995年   24315篇
  1994年   23424篇
  1993年   21511篇
  1992年   53354篇
  1991年   51354篇
  1990年   49679篇
  1989年   48626篇
  1988年   45709篇
  1987年   44590篇
  1986年   42640篇
  1985年   40110篇
  1984年   30163篇
  1983年   26396篇
  1982年   18832篇
  1981年   17344篇
  1979年   29349篇
  1978年   21766篇
  1977年   19781篇
  1976年   17939篇
  1975年   19670篇
  1974年   22273篇
  1973年   21566篇
  1972年   20768篇
  1971年   19121篇
  1970年   18179篇
  1969年   17158篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
In order to examine time trends of the prevalences of HBeAg positives among HBV carriers in Japan, we analysed data on HBeAg of HBsAg positive voluntary blood donors (23,560 males, and 8659 females) at the Osaka Red Cross Blood Centre between January 1977 and March 1984. Age-specific prevalences of HBeAg positives decreased year by year for both sexes, especially for those in their teens and twenties. The prevalences of HBeAg positives decreased with age, but at any given age it was lower for the later than for the earlier birth cohorts. Although reasons for the secular declines are unknown, the findings suggest that the prevalence of HBeAg positives among HBV carriers will continue to decrease in Japan. This, together with the immunization programme implemented this year, may lead to a future reduction in the risk of HBV related liver diseases in Japan.  相似文献   
992.
Blood histamine levels were measured by the bioassay of histamine (on an isolated strip of guinea pig ileum) in workers exposed to cotton dust in a textile mill in Ahmedabad. Byssinotic subjects showed very high levels of blood histamine as compared to nonbyssinotic and control subjects. The blood histamine levels were not well correlated to the dust concentrations or duration of exposure but rather to the day of the week (ie, first, second, third, etc., after weekend break) on which the samples were collected. The blood histamine levels were high on the first day of the work week, when byssinotics complained most of their symptoms.  相似文献   
993.
994.
A boy with rhizomelic chondrodysplasia punctata, diagnosed on the laboratory evidence of a high plasma concentration of phytanic acid and a low erythrocyte concentration of plasmalogens, has been followed from birth to the age of 16 years. The clinical pattern (somatic, skeletal and neurological) tallies with published findings in this disease. Unusual findings are the associated epilepsy, confirmed by EEG, and the long survival. CT brain scan and MRI showed cortical and subcortical atrophy but not gyral abnormalities or demyelination.
Sommario Viene descritto il caso di un bambino affetto da condrodisplasia punctata rizomelica seguito dalla nascita fino ai 16 anni. La diagnosi clinica, efettuata in base alle caratteristiche somatiche, scheletriche e neurologiche del paziente è stata confermata dai reperti di laboratorio (alta concentrazione plasmatica di acido fitanico, bassa concentrazione di plasmalogeni eritrocitari). Come correlati inusuali del quadro clinico vanno segnalati l'associazione con epilessia e a la lunga sopravvivenza. La TAC e la RNM cerebrale hannovaltresì documentato atrofia corticale e sottocorticale ma non anomalie della girazione o demielinizzazione.
  相似文献   
995.
H Yamamoto  S Tsuji  Y Nagai 《Brain research》1991,558(1):117-119
We established a MAb N-25 reacted with a minor unknown antigen (AgX) in a commercially available GQ1b sample. It also recognized minor antigens in bovine brain (X-1, 2, 3, 4 and 5) and cultured neural cell lines (X-1). AgX is identical to X-5. X-5 is sialidase sensitive and has the common structure as X-1, which is resorcinol positive. These results suggested that novel gangliosides exist in bovine brain and neural cell lines.  相似文献   
996.
Lymphoscintigraphy in lymphedema: an aid to microsurgery   总被引:3,自引:0,他引:3  
The role of lymphoscintigraphy, performed with 99mTc-labeled antimony sulfur colloid, in the diagnosis of lymphedema and as a test for selection of patients for microvascular operation was evaluated in 32 patients with primary and secondary lymphedema and four patients with other causes of leg edema. Lymphoscintigraphy clearly demonstrated if edema was of lymphatic origin. Five different image patterns were identified; abnormal image patterns could not be predicted from clinical history or physical findings. Quantitative evaluation of removal of the radioactive colloid from the injection site and appearance in lymph node sites and liver was of limited usefulness. Nine patients underwent various surgical procedures before or after lymphoscintigraphy. Lympho-venous anastomoses were possible only in patients who had patent lymph channels visible on lymphoscintigrams. Based on initial experience, lymphoscintigraphy seems to be useful to select patients for microvascular operation.  相似文献   
997.
Angiogenesis and patency of blood vessels were analyzed qualitatively in solid CNS and peripheral tissue syngeneic, allogeneic, and xenogeneic grafts and in individual cell suspension grafts of astrocytes, fibroblasts, PC12, and three additional tumor cell lines placed intracerebrally in adult host mice. Postgrafting survival times were 1 day through 4 weeks. The patency of graft vessels was determined in sections from immersion-fixed tissues incubated to reveal the endogenous peroxidase activity of host red cells trapped within the lumen of blood vessels. Additionally, horseradish peroxidase (HRP) was administered intravenously to live hosts; HRP labels host brain and graft vessels on the luminal surface and reveals the presence or absence of a blood-brain barrier (BBB) within the grafts. The origins of blood vessels supplying solid tissue xenografts were identified immunohistochemically with primary antibodies against host (athymic AKR mice) and donor (fetal Lewis rats) major histocompatibility complex (MHC) class I. Blood vessels supplying solid CNS grafts at 1-7 days post-transplantation were identified ultrastructurally and possessed interendothelial tight junctional complexes; however, they were not perfused with either host blood or blood-borne HRP prior to 8 days. Graft vessels at 10 days were outlined consistently by peroxidase-positive red cells in immersion-fixed material and labeled with blood-borne HRP. These vessels provided a BBB to the circulating HRP and exhibited interendothelial tight junctions. Evidence of angiogenesis within solid anterior pituitary grafts and the variety of cell suspension grafts was obtained prior to 3 days post-transplantation in immersion-fixed preparations; the vessels, with the notable exception of those supplying astrocyte cell suspensions, failed to present a BBB to blood-borne peroxidase. Endothelia in the solid pituitary allografts and the PC12 cell grafts were highly fenestrated and exhibited open interendothelial junctions; those in the tumor and fibroblast cell grafts, for the most part, appeared nonfenestrated, and many possessed open interendothelial junctional complexes. Immunostaining for host and donor MHC class I revealed that donor blood vessels predominate over host vessels in CNS xenografts and supply pituitary xenografts exclusively; in both preparations, donor vessels were not identified within the host CNS. Because cell suspension grafts were derived from endothelia-free preparations grown in culture, blood vessels supplying these grafts were necessarily of host CNS origin and manifested a morphological transformation from a BBB to a non-BBB endothelium. The data suggest that angiogenesis in solid CNS grafts placed into the adult host CNS, compared to similarly placed solid peripheral tissue/cell suspension grafts, is not rapid.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   
998.
999.
1000.
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