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   827篇
  免费   52篇
  国内免费   14篇
耳鼻咽喉   5篇
儿科学   57篇
妇产科学   10篇
基础医学   114篇
口腔科学   18篇
临床医学   122篇
内科学   132篇
皮肤病学   10篇
神经病学   41篇
特种医学   191篇
外科学   40篇
综合类   35篇
预防医学   29篇
眼科学   4篇
药学   55篇
肿瘤学   30篇
  2021年   3篇
  2020年   5篇
  2019年   6篇
  2018年   8篇
  2017年   5篇
  2016年   8篇
  2015年   8篇
  2014年   22篇
  2013年   20篇
  2012年   12篇
  2011年   19篇
  2010年   18篇
  2009年   24篇
  2008年   13篇
  2007年   30篇
  2006年   22篇
  2005年   22篇
  2004年   14篇
  2003年   22篇
  2002年   10篇
  2001年   18篇
  2000年   13篇
  1999年   25篇
  1998年   44篇
  1997年   52篇
  1996年   40篇
  1995年   41篇
  1994年   24篇
  1993年   27篇
  1992年   18篇
  1991年   22篇
  1990年   21篇
  1989年   15篇
  1988年   28篇
  1987年   27篇
  1986年   22篇
  1985年   19篇
  1984年   8篇
  1983年   8篇
  1982年   19篇
  1981年   14篇
  1980年   22篇
  1979年   6篇
  1978年   12篇
  1977年   24篇
  1976年   12篇
  1975年   9篇
  1974年   4篇
  1969年   2篇
  1963年   2篇
排序方式: 共有893条查询结果,搜索用时 31 毫秒
71.
慢性失眠症患者的思维特点   总被引:1,自引:0,他引:1  
目的:观察慢性失眠症患者的认知行为特征和其症状的产生及发展的关系,分析慢性失眠症患者的思维特点。方法:随机抽取北京中医药大学国医堂睡眠障碍门诊2004-01/07失眠症患者90例和配对睡眠正常者90人进行问卷调查,包括匹兹堡睡眠质量指数问卷、关于睡眠的非功能性的信念和态度量表修订版问卷以及思维控制问卷。匹兹堡睡眠质量指数问卷包括7个因子,每个因子按0~3等级记分,得分越高表示睡眠质量越差。关于睡眠的非功能性的信念和态度量表修订版由10个条目组成,5级评分,得分越高表示关于睡眠的非功能性的信念和态度越多。思维控制问卷由30个条目组成,包括6个纬度:认知转移、行为转移、社会支持、担心、惩罚和再评价,每个纬度的得分越高表示使用此种思维控制的方式越多。结果:发放问卷180份,回收完整问卷158份,有效率87.8%。最终病例组和对照组各79人,进入结果分析。①慢性失眠症患者关于失眠的短期影响、长期影响和对于睡眠的控制的非功能性的态度和信念得分均高于对照组(19.48±2.90,14.14±5.87;11.06±1.79,8.11±2.74;7.82±1.44,5.01±2.07;t=9.86,7.25,8.01,P<0.01)。②慢性失眠症患者使用担心和惩罚的思维控制方式得分高于睡眠正常组(10.7±2.6,8.5±2.9;11.6±2.8,9.0±3.1;t=5.08,5.43,P<0.01)。③关于睡眠的非功能性的信念和态度与担心和惩罚的思维控制方式呈正相关(r=0.41,0.24,P<0.01)。结论:对于失眠症患者进行认知行为治疗时,要注意纠正失眠症患者关于睡眠的非功能性的信念和态度,并指导失眠症患者学习有效的思维控制方式。  相似文献   
72.
低氧暴露对运动性贫血大鼠抗氧化能力的影响   总被引:2,自引:0,他引:2  
目的:观察低氧暴露对运动性贫血大鼠某些抗氧化酶的影响,探讨低氧条件下抗氧化系统的反应是否有利于改善运动性贫血。方法:实验于2005-07/09在广东省高等学校运动生物化学教学重点实验室完成。选择6周龄健康雄性SD大鼠40只,均为运动性贫血动物模型,大鼠适应环境1周后采用6周递增负荷跑台运动方式建立。按随机数字表法分为1h低氧暴露组、2h低氧暴露组和间歇性低氧暴露组、常氧恢复组,每组10只。采用人工常压低氧环境,低氧浓度控制在14.5%左右,按分组每天在常压低氧舱进行1,2h和间歇性低氧暴露(低氧暴露1h,中间间歇3h,再低氧暴露1h),其余时间在舱外常氧中自由活动,每周6d,持续3周。常氧恢复组大鼠在常氧中自由活动。3周后测试运动性贫血大鼠血清丙二醛含量、超氧化物歧化酶活性和血浆过氧化氢酶、谷胱甘肽过氧化酶活性。结果:纳入动物40只,均进入结果分析。①低氧暴露3周后1h低氧暴露组、2h低氧暴露组、间歇性低氧暴露组血清丙二醛含量均显著低于常氧恢复组[分别为(2.62±0.16),(2.60±0.22),(2.55±0.06),(3.36±0.34)μmol/L,P<0.05]。②低氧暴露3周后血清超氧化物歧化酶和血浆谷胱甘肽过氧化酶、过氧化氢酶活性均高于常氧恢复组,2h低氧暴露组与常氧恢复组比较差异有显著性意义[分别为(4239.68±169.53),(3190.30±339.40)μkat/L;(20622.46±2002.07),(15556.44±607.79)μkat/L;(50.01±6.67),(35.17±4.50)μkat/L,P<0.05]。③各低氧暴露组间除2h低氧暴露组血清超氧化物歧化酶活性显著高于1h低氧暴露组外[分别为(4239.68±169.53),(2126.41±161.20)μkat/L,P<0.05],其他指标组间差异无显著性意义(P>0.05)。结论:低氧暴露可提高运动性贫血大鼠机体的抗氧化能力,有利于促进运动性贫血的恢复。  相似文献   
73.
Red cells preserved in extended-storage media are the standard product dispensed by many regional blood centers. When the red cells are intended for neonatal transfusion, concern exists about the safety of the relatively high quantities of additives present in these media. Definitive studies to address these concerns are not available. Therefore, to estimate the effects of additives and to delineate circumstances in which they might be harmful, the quantities transfused in defined clinical settings were calculated, and the following recommendations are offered for transfusing infants less than 4 months of age. First, red cells preserved in extended-storage media should present no substantive risks when used for small-volume (approximately 10 mL/kg) transfusions of premature infants and can be used without additional processing. Second, the risks of the most premature neonatal patients or those with severe renal and/or hepatic insufficiency cannot be defined clearly, and, because data are not available to ensure safety for these infants, removal of the additive medium and resuspension of the red cells in saline or albumin solution immediately before transfusion are recommended. Third, following a similar rationale, it seems prudent to avoid using entire units of red cells preserved in extended-storage media in massive transfusion settings (e.g., exchange transfusion, cardiac surgery, and extracorporeal membrane oxygenation). In these settings, the preservative medium should be removed and the red cells resuspended in the fluid that is most appropriate for the procedure that is planned. It must be emphasized that these recommendations are based on calculations and hypothetical settings, not actual data. Accordingly, they are tentative and should be altered as definitive information becomes available.  相似文献   
74.
Intraindividual Reproducibility of Heart Rate Variability   总被引:1,自引:0,他引:1  
Heart rate variability was determined from three consecutive Holter recordings performed on days 1, 7, and 28 in 17 normal subjects, in 13 patients with angiographically normal coronary arteries, and in 9 patients with remote myocardial infarctions. Group data of several time and frequency domain measures of heart rate variability were highly reproducible (correlation coefficients 0.629–0.894). However, some individuals exhibited considerably larger day-to-day variations in heart rate variability. Single heart rate indices differed by up to 50% between two Holter recordings. Such potential differences must be considered when repeated heart rate variability determinations are used to assess changes in neurocardiac reflex regulation or effects of therapeutic interventions.  相似文献   
75.
76.
Mycobacterial Infections After Renal Transplantation   总被引:5,自引:0,他引:5  
Mycobacterial infections occurred in 11 of 633 (1.7 per cent)recipients of successful renal transplants. There were no casesof tuberculosis in patients receiving chemoprophylaxis, butamongst those who did not receive prophylaxis disease occurredin six of the 27 (22 per cent) high-risk patients. The majorcause of morbidity during treatment was renal allograft rejection,largely due to reduction in immunosuppressive drug therapy.  相似文献   
77.
Caveolae are plasma membrane invaginations, which have been implicated in endothelial transcytosis, endocytosis, potocytosis, and signal transduction. In addition to their well-defined morphology, caveolae are characterized by the presence of an integral membrane protein termed VIP21-caveolin. We have recently observed that lymphocytes have no detectable VIP21-caveolin and lack plasma membrane invaginations resembling caveolae. Here we transiently express VIP21-caveolin in a lymphocyte cell line using the Semliki Forest virus expression system and show de novo formation of plasma membrane invaginations containing VIP21-caveolin. These invaginations appear homogeneous in size and morphologically indistinguishable from caveolae of nonlymphoid cells. Moreover, the glycosylphosphatidylinositol-anchored protein. Thy1, patched by antibodies, redistributes to the newly formed caveolae. Our results show that VIP21-caveolin is a key structural component required for caveolar biogenesis.  相似文献   
78.
79.
Mid-trimester loss--appraisal of a screening protocol   总被引:1,自引:0,他引:1  
The main causes for mid-trimester loss are known. There is likely to be overlap with those of first trimester loss, but the proportions may be different. We wished to perform an aetiological survey in a large population of patients with a history of recurrent miscarriage, for possible explanations for their second trimester miscarriages. Database analysis of 636 patients attending a UK University Teaching Hospital dedicated miscarriage clinic between 1991 and 1996 revealed a 25% prevalence (n = 158) for second trimester miscarriage. Results from an investigative screening protocol were positive in 50% of cases: 33% (n = 52) tested positive for antiphospholipid syndrome (APS); 8% (n = 13) fulfilled strict criteria for cervical incompetence; there was a 4% prevalence of uterine anomaly; 3% for infection (n = 5) and 2% of patients (n = 3) proved to be hypothyroid. Importantly, dual pathology was found in 5% of patients with a history of second trimester miscarriage. As idiopathic mid-trimester loss is a diagnosis by exclusion, a high index of suspicion is required, as are modern diagnostic techniques.   相似文献   
80.
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