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   322篇
  免费   9篇
  国内免费   26篇
耳鼻咽喉   1篇
儿科学   11篇
基础医学   27篇
口腔科学   5篇
临床医学   40篇
内科学   100篇
皮肤病学   2篇
神经病学   5篇
特种医学   87篇
外科学   32篇
综合类   13篇
预防医学   4篇
眼科学   3篇
药学   20篇
肿瘤学   7篇
  2021年   3篇
  2016年   2篇
  2015年   6篇
  2014年   4篇
  2013年   6篇
  2012年   5篇
  2011年   5篇
  2010年   11篇
  2009年   11篇
  2008年   5篇
  2007年   8篇
  2006年   26篇
  2005年   11篇
  2004年   5篇
  2003年   4篇
  2002年   2篇
  2001年   5篇
  2000年   5篇
  1999年   2篇
  1998年   14篇
  1997年   5篇
  1996年   19篇
  1995年   15篇
  1994年   16篇
  1993年   7篇
  1992年   8篇
  1991年   9篇
  1990年   9篇
  1989年   16篇
  1988年   15篇
  1987年   14篇
  1986年   12篇
  1985年   16篇
  1984年   4篇
  1983年   6篇
  1982年   3篇
  1981年   8篇
  1980年   6篇
  1979年   2篇
  1978年   2篇
  1977年   4篇
  1976年   2篇
  1975年   3篇
  1955年   2篇
  1954年   2篇
  1950年   2篇
  1949年   1篇
  1948年   1篇
  1943年   2篇
  1935年   1篇
排序方式: 共有357条查询结果,搜索用时 216 毫秒
21.
目的探讨医源性脾脏损伤脾切除对结直肠癌切除患者术后长期生存的影响。方法对1990年1月1日至1999年12月31日10年间行结直肠癌手术切除并附带脾切除患者进行病例配对回顾研究。分析患者年龄、性别、依据美国麻醉学医师协会(ASA)标准评估的身体状况、疾病分期、手术类型及预后等资料。配对病例来自同一医疗中心,性别、年龄、疾病分期及手术类型完全相同。手术附带脾切除患者为试验组,未切脾者为对照组。结果55例患者行医源性脾切除术,对照组在年龄、性别、身体状况、疾病分期及手术类型上与之匹配。随访时间(从手术开始到患者死亡或者最后一次随访1为2~205个月(中位随访时间为43个月)。Cox比例危险度模型进行Kaplan-Meier法生存分析发现两组间差异有显著性意义,不切除脾脏对患者生存有利(危险度1.8,95%可信区间为1-3.3,P=0.0399),未切脾组与切脾组5年生存率分别为70%和47%,10年生存率分别为55%和38%。结论结直肠癌患者在行结肠或直肠切除时,因医源性脾脏损伤而切除脾脏者,预后较差。  相似文献   
22.
对人流感病毒A/Udorn/72(H_3N_2)株与禽类流感病毒A/Mallard/NY/78/(H_2N_2)重组后的重组株分析表明,仅含禽类病毒的核蛋白(NP)或膜蛋白(M)的RNA片段的重组株,在松鼠猴的呼吸道繁殖是受限制的。另外。仅有禽类的RNAl和NS基因的重组株(Clone 12)在松鼠猴的气管内的繁殖也明显受限制,而只具有其中一个基因的Clone 9, Clone 2, 则限制就不明显。由此表明,禽类流感病毒的NP和M基因在宿主范围的繁殖限制中起主要作用,而RNAI和SN基因的结合,同样起着繁殖受限制作用。  相似文献   
23.
Mode of regulation of natural killer cell activity by interferon   总被引:18,自引:5,他引:18       下载免费PDF全文
Whereas xenogeneic tumors such as baby hamster kidney or HeLa cells grow in nude mice, the same cells persistently infected with a variety of viruses are rejected. Spleen cells from normal nude mice were found to be induced to produce interferon and to exert natural killer (NK) activity on virus persistently infected (PI) tumor cells, and not on uninfected parental cells in vitro. The phenotype of the interferon-producing cells and the NK effector cells was found to be the same namely, Qa 5(+), Ly 5(+), ganglio-N- tetraosylceramide, with 35 percent of the NK cells also expressing Thy 1.2. NK activity against virus PI tumor cell lines could be nonspecifically augmented both in vivo and in vitro by prior contact with virus PI tumor cells. It was unambiguously demonstrated with chemically homogeneous mouse interferon that interferon, and not a contaminant, was responsible for the augmentation of NK activity in vitro. Studies on the mode of interferon action in augmenting NK activity revealed that the target cell for interferon action was serologically distinct from the NK effector cell. Anti-Ly 5 + complement (C)-treated spleen cells were depleted of NK activity and the ability to produce interferon, but, upon incubation with interferon for 1-3 h, regained both NK activity and susceptibility to anti-Ly 5 + C. Treatment with anti-Qa 5 + C eliminated NK activity, which could not be restored by the addition of interferon. We conclude that interferon produced by Ly 5(+) cells in response to virus PI tumor cells acts on Ly 5(-) precursor cells and induces their differentiation into functional Ly 5(+) NK effector cells.  相似文献   
24.
Objectives: To assess the influence of clinical status on the association between total plasma bilirubin and unbound bilirubin on death or adverse neurodevelopmental outcomes at 18–22 months corrected age in extremely low birth weight infants. Method: Total plasma bilirubin and unbound bilirubin were measured in 1101 extremely low birth weight infants at 5 ± 1 days of age. Clinical criteria were used to classify infants as clinically stable or unstable. Survivors were examined at 18–22 months corrected age by certified examiners. Outcome variables were death or neurodevelopmental impairment, death or cerebral palsy, death or hearing loss, and death prior to follow‐up. For all outcomes, the interaction between bilirubin variables and clinical status was assessed in logistic regression analyses adjusted for multiple risk factors. Results: Regardless of clinical status, an increasing level of unbound bilirubin was associated with higher rates of death or neurodevelopmental impairment, death or cerebral palsy, death or hearing loss and death before follow‐up. Total plasma bilirubin values were directly associated with death or neurodevelopmental impairment, death or cerebral palsy, death or hearing loss, and death before follow‐up in unstable infants, but not in stable infants. An inverse association between total plasma bilirubin and death or cerebral palsy was found in stable infants. Conclusions: In extremely low birth weight infants, clinical status at 5 days of age affects the association between total plasma bilirubin and death or adverse neurodevelopmental outcomes at 18–22 months of corrected age. An increasing level of UB is associated a higher risk of death or adverse neurodevelopmental outcomes regardless of clinical status. Increasing levels of total plasma bilirubin are directly associated with increasing risk of death or adverse neurodevelopmental outcomes in unstable, but not in stable infants.  相似文献   
25.
26.
27.
本文依据一组含有不同比例待测和干扰组分的标准混合液的吸收值,采用一元线性回归方法,在选择最佳测定波长对的同时建立标准工作曲线方程,使其更符合实际作品测定时的情况,提高了结果的精度和可靠性,并使计算量和实验工作量得以降低。应用于复方氨基比林注射液中三组分氨基比林、安替比林和巴比妥的同时测定,其平均回收率分别为99.8%,100.4%和99.8%,变异系数分别为0.59,1.48和1.05,结果优于卡尔曼滤波法、偏最小二乘法和目标因子分析法。  相似文献   
28.
29.
30.
A 19-year-old, untransfused Melanesian man from Papua New Guinea was admitted to the hospital for repair of an atrial septal defect. His serum contained an alloantibody that reacted strongly on the indirect antiglobulin test and was identified as anti-Ge. Gerbich-negative blood was transfused following urgent surgery. A 51Cr red cell survival study performed 2 weeks after surgery yielded zero survival of Gerbich-positive cells after 24 hours. A monocyte-driven, antibody-dependent, cell-mediated cytotoxicity assay performed on both pretransfusion and posttransfusion serum samples and on concentrated serum showed less than 1 percent specific lysis of Gerbich-positive cells. This did not correlate with the indication of clinical significance predicted by the 51Cr study. Red cell adherence and phagocytosis, not evident in a monocyte monolayer assay using native serum, were demonstrable in 16 percent of monocytes by the use of concentrated serum.  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