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   1454353篇
  免费   112810篇
  国内免费   10706篇
耳鼻咽喉   17962篇
儿科学   45435篇
妇产科学   39024篇
基础医学   209999篇
口腔科学   38394篇
临床医学   144785篇
内科学   276736篇
皮肤病学   27847篇
神经病学   117770篇
特种医学   52159篇
外国民族医学   406篇
外科学   196378篇
综合类   47730篇
现状与发展   21篇
一般理论   477篇
预防医学   123409篇
眼科学   32253篇
药学   111588篇
  120篇
中国医学   9603篇
肿瘤学   85773篇
  2021年   16164篇
  2020年   10828篇
  2019年   15171篇
  2018年   20092篇
  2017年   15843篇
  2016年   16404篇
  2015年   20232篇
  2014年   27272篇
  2013年   38718篇
  2012年   53922篇
  2011年   57242篇
  2010年   34304篇
  2009年   30861篇
  2008年   50124篇
  2007年   52379篇
  2006年   52101篇
  2005年   49978篇
  2004年   46126篇
  2003年   43629篇
  2002年   41738篇
  2001年   63376篇
  2000年   64870篇
  1999年   54522篇
  1998年   15819篇
  1997年   14416篇
  1996年   14034篇
  1995年   13346篇
  1994年   12467篇
  1993年   11386篇
  1992年   42258篇
  1991年   41379篇
  1990年   39966篇
  1989年   37779篇
  1988年   34994篇
  1987年   34041篇
  1986年   32442篇
  1985年   30866篇
  1984年   23176篇
  1983年   19718篇
  1982年   11822篇
  1979年   20914篇
  1978年   14904篇
  1977年   12128篇
  1976年   11931篇
  1975年   12148篇
  1974年   14879篇
  1973年   14529篇
  1972年   13424篇
  1971年   12464篇
  1970年   11522篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Somatostatin (SRIF) in the central nervous system is mostly concentrated in the median eminence (ME). Immunocytochemical methods have revealed high densities of SRIF-positive perikarya between the preoptic area and the periventricular nucleus of the hypothalamus (NPE). The aim of the present study was to define more precisely the specific pathways of SRIF neurons from NPE to the ME. SRIF levels were measured by radioimmunoassay, following various hypothalamic transections. Frontal periventricular sections decreased SRIF-ME content by 70% (P less than 0.01), when located at the anterior end of the ME but no diminution was observed when the cuts were located anteriorly or posteriorly. Parasaggital transections decreased SRIF-ME levels by 50% (P less than 0.05) when located at the outer border of the ventromedial and premammillary nucleus, but the decrease was not significant when cuts were located anteriorly. Taken together, our data indicate that most SRIF-containing neurons, originating in the NPE, do not reach the ME directly along the border of the 3rd ventricle; instead they form a loop across the medial forebrain bundle before re-entering the mediobasal hypothalamus at the ME level.  相似文献   
992.
993.
This study evaluates the potential for endothelial seeding of a collagen-impregnated Dacron graft with or without surface modifiers (fibronectin, heparin) to attach and retain these cells during flow. Human umbilical endothelial cells were harvested, cultured, labeled with Indium111-oxine and seeded onto 30 mm X 4 mm diameter grafts. Six graft surfaces were studied: 1) a collagen-impregnated Dacron graft, HemashieldR (C); 2) C + fibronectin (C + F); 3) C + heparin (C + H); 4) C + F + H; 5) HytrelR + F (Hyt + F); and 6) Hyt + F + H. Radioactive loss determined the percentage attachment and then percentage retention of labeled inoculum after a one-hour in vitro perfusion. Scanning electron and light microscopy demonstrated the endothelium on the graft surface following perfusion. Fibronectin-coated grafts had a significantly higher percentage attachment than those without fibronectin (ANOVA, P less than 0.05). However, the percentage retention following perfusion was similar for all Dacron grafts and statistically inferior to the HytrelR grafts studied (ANOVA, P less than 0.05). SEM evaluation of the C + F + H graft surface was qualitatively the most impressive Dacron surface for seeding, yet was inferior to the HytrelR graft. We conclude that fibronectin benefits the initial attachment of endothelium to collagen-coated Dacron rivaling the HytrelR surface. Fibronectin does not improve percentage retention of the HemashieldR surface during perfusion, therefore, some of its initial benefit is lost.  相似文献   
994.
The authors report their experience of anterolateral bilateral approach of cervical spine. They underline the advantages and inconvenience of this route and discuss the indications.  相似文献   
995.
996.
Cancer risk after evaluation for infertility   总被引:3,自引:0,他引:3  
To evaluate cancer risk by various causes of infertility, the authors conducted a retrospective cohort study among 2,335 women evaluated for infertility at the Mayo Clinic between 1935 and 1964. Most cancers occurred at expected frequencies, with the exception of cancers of the thyroid (standardized incidence ratio (SIR) = 2.6) and other endocrine glands (SIR = 6.7), although analyses were based on small numbers. Patients with progesterone deficiencies (31 per cent of the study subjects) had a 20 per cent higher cancer risk than did those with other causes of infertility, with excesses deriving primarily from cancers of the lung, cervix, ovary, and thyroid and from melanoma. Breast cancer risk, however, was not elevated in either patients with progesterone deficiencies (SIR = 0.9) or patients with other causes of infertility (SIR = 1.0). Examination of other parameters of infertility, including age at evaluation, type of infertility (primary vs. secondary), and years of attempted conception, showed no elevated risks of breast cancer in any subgroup. These results fail to support previous studies that have linked progesterone deficiencies among infertile women to elevated breast cancer risk. However, the data suggest a possible involvement of a progesterone deficiency in the etiology of other cancers, particularly thyroid cancer and melanoma.  相似文献   
997.
998.
999.
A general overview of the literature concerning the development of diabetic neuropathic arthropathy is discussed. A case report is presented dealing with spontaneous fractures of the lesser metatarsal in a patient with an amputated hallux and peripheral neuropathy secondary to diabetes mellitus.  相似文献   
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