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   296635篇
  免费   17264篇
  国内免费   415篇
耳鼻咽喉   4207篇
儿科学   10292篇
妇产科学   10248篇
基础医学   45048篇
口腔科学   7498篇
临床医学   24243篇
内科学   55892篇
皮肤病学   6319篇
神经病学   21041篇
特种医学   11636篇
外国民族医学   43篇
外科学   46711篇
综合类   7768篇
现状与发展   1篇
一般理论   160篇
预防医学   19927篇
眼科学   6945篇
药学   20907篇
中国医学   787篇
肿瘤学   14641篇
  2018年   3623篇
  2017年   2656篇
  2016年   3074篇
  2015年   3494篇
  2014年   4583篇
  2013年   7216篇
  2012年   9071篇
  2011年   9461篇
  2010年   6137篇
  2009年   5562篇
  2008年   8685篇
  2007年   9536篇
  2006年   9381篇
  2005年   8977篇
  2004年   8675篇
  2003年   8178篇
  2002年   7772篇
  2001年   13344篇
  2000年   13662篇
  1999年   11426篇
  1998年   3025篇
  1997年   2789篇
  1996年   2637篇
  1995年   2544篇
  1994年   2345篇
  1992年   8322篇
  1991年   8453篇
  1990年   8267篇
  1989年   8088篇
  1988年   7320篇
  1987年   7077篇
  1986年   6728篇
  1985年   6524篇
  1984年   4766篇
  1983年   4125篇
  1982年   2471篇
  1979年   4437篇
  1978年   3237篇
  1977年   2736篇
  1976年   2513篇
  1975年   2841篇
  1974年   3362篇
  1973年   3366篇
  1972年   3122篇
  1971年   2948篇
  1970年   2841篇
  1969年   2585篇
  1968年   2541篇
  1967年   2376篇
  1966年   2264篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Previous studies indicated a role for ischemia in the metabolic changes induced by cholestasis. Liver pyruvate kinase is a key enzyme for the concurrent control of glycolysis and gluconeogenesis. In this experiment the control of pyruvate kinase activity was investigated in cholestatic rats. Pyruvate kinase kinetics changed from a sigmoidal type in sham-operated rats to a hyperbolic type in obstructed rats. The change in the enzymatic kinetics paralleled the reduction in the portal blood flow, which reached 50% of the control value 7 days after obstruction. Dibutyryl cyclic AMP (5 mumol/kg body wt) plus theophylline 0.1 mmol/L failed to inactivate the enzyme when injected into the portal veins of rats whose livers were obstructed 7 days before. Both the kinetics changes and the lack of phosphorylation control are compatible with ischemia.  相似文献   
992.
R Kino  R O Day  G A Pearce  G W Fulde 《Chest》1991,100(6):1572-1577
An experimental technique designed to predict theophylline doses needed to attain therapeutic theophylline concentrations in 43 emergency department (ED) patients was compared with a standard conventional regimen in 46 ED patients. The experimental protocol utilized a computer-assisted dosage prediction program that incorporated baseline theophylline concentration rapidly obtained using a bedside assay. The standard protocol used conventional loading and infusion rates, as well as an estimate of time of last theophylline dose based on patient history. Plasma theophylline concentrations, estimated 1 and 6 hours after commencement of aminophylline therapy in each regimen, were compared. The experimental protocol was equally rapid but much more accurate in achieving targeted theophylline concentrations. Experimental dosage prediction was associated with a higher proportion of theophylline concentrations in the therapeutic range at 1 (81 percent vs 26 percent; p less than 0.001) and 6 hours (91 percent vs 37 percent; p less than 0.001). There was a trend toward fewer toxic concentrations recorded at 1 (0 percent vs 7 percent; p = 0.27) and 6 hours (0 percent vs 10 percent; p = 0.08). This protocol, which was performed quickly and without difficulty by residents in a busy hospital ED, offers an opportunity to improve the efficacy and decrease the toxicity of theophylline use in asthma emergencies.  相似文献   
993.
994.
995.
996.
The number of white blood cells, the morphological changes of the peripheral lymphocytes and some immunological variables were examined in 118 centenarians and in 499 healthy subjects of 60-89 years of age. There was no change in the absolute number of leucocytes, lymphocytes, or T or B cells with age. The occurrence of a myelin-like structure in the mitochondria and the presence of lipofuscin in the cytoplasm of lymphocytes increased with age and showed a correlation with the absolute number of T cells. A correlation could be observed between the absolute number of B cells, serum IgG level and the presence of antinuclear factor.  相似文献   
997.
A group of clinics cooperating as the Lupus Plasmapheresis Study Group (LPSG) is starting an international multicenter study of the treatment of severe systemic lupus erythematosus. The primary goal of this randomized and prospective trial is to establish whether treatment with plasmapheresis and subsequent pulse cyclophosphamide improves the outcome compared to treatment with pulse cyclophosphamide alone. The underlying rationale assumes that plasmapheresis: a) eliminates pathogenic autoantibodies and immune complexes and b) induces a compensatory activation of pathogenic lymphocyte clones through a feed-back between circulating antibodies and their respective antibody-producing clones. Synchronization of plasmapheresis with subsequent pulse cyclophosphamide should enhance the deletion of pathogenic clones during the period of greatest vulnerability. This overview reviews the first results of treatment approaches based on this concept and summarizes the design of the LPSG trial.  相似文献   
998.
The significance of antiphospholipid antibodies in pre-eclamptic women has not been thoroughly elucidated. The purpose of this study was to determine the proportion of pre-eclamptic women who were antiphospholipid antibody positive, and to elucidate the significance of these antibodies regarding growth retardation and neonatal outcome. Positive levels of anticephalin antibodies, which are antiphospholipid antibodies, were detected in 7 (19%) out of 37 pre-eclamptic women, as compared with none of 40 in a control group of normotensive women at similar stage of pregnancy (p = 0.004). The birthweight percentiles of the neonates of anticephalin antibody positive women were significantly lower than those of the neonates of anticephalin antibody negative women (p = 0.018). Four of 7 infants of anticephalin antibody positive women were growth retarded (less than 2.5th percentile). This was a significantly larger proportion than that for anticephalin antibody negative women (3/30) (p = 0.004). The 95% confidence interval for the difference between the two proportions was 0.10 to 0.85. Two of the 7 neonates of anticephalin antibody positive women died during the neonatal period, compared with none of the 30 neonates of anticephalin antibody negative women (p = 0.003). Thus, our study suggests that positive levels of anticephalin antibodies in pre-eclamptic women increase the risk for growth retardation and neonatal death.  相似文献   
999.
O Schwetschke  W Heppt  J A Born 《HNO》1992,40(7):277-279
Leiomyosarcomas arise rarely in the head and neck. We report a 41-year-old woman with an extremely rare leiomyosarcoma of the floor of the mouth extending to the oropharynx. This article stresses the value of imaging methods such as CT, MRI and ultrasound for preoperative diagnosis, and emphasises histopathological findings. The therapeutic principles and prognostic factors of leiomyosarcomas are illustrated on the basis of this case.  相似文献   
1000.
We studied hypertrophic patterns in the electrocardiograms of 60 Nigerian hypertensives. Thirty were in heart failure and 30 without failure (matched for age and sex). Combined left ventricular and left atrial hypertrophy was the commonest finding occurring in 58.3%, followed by left ventricular hypertrophy alone in 30%. 76.7% and 40% had combined left ventricular and left atrial hypertrophy in the heart failure and the non-heart failure groups, respectively (P less than 0.02). Though these changes increased with increased blood pressure, the latter is similarly severe in both groups. 100% of patients in Class IV failure had combined left ventricular and left atrial hypertrophy. The 3 patients who had additional right atrial hypertrophy were in Class IV failure, 2 of whom died during follow-up. These changes are much more marked at presentation than reprots in caucasians and even in previous reports in Africans. The changes reflect the long-standing nature and severity of the hypertensive process, and point to the fact that the majority of hypertensives in this environment present rather late.  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