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   28875篇
  免费   1559篇
  国内免费   395篇
耳鼻咽喉   99篇
儿科学   625篇
妇产科学   229篇
基础医学   2893篇
口腔科学   215篇
临床医学   4127篇
内科学   8823篇
皮肤病学   509篇
神经病学   2127篇
特种医学   1150篇
外科学   3039篇
综合类   2888篇
现状与发展   1篇
一般理论   3篇
预防医学   1257篇
眼科学   165篇
药学   1623篇
  7篇
中国医学   586篇
肿瘤学   463篇
  2023年   488篇
  2022年   942篇
  2021年   1217篇
  2020年   1043篇
  2019年   1139篇
  2018年   1063篇
  2017年   947篇
  2016年   811篇
  2015年   1046篇
  2014年   1952篇
  2013年   1991篇
  2012年   1351篇
  2011年   1549篇
  2010年   1315篇
  2009年   1364篇
  2008年   1412篇
  2007年   1308篇
  2006年   1190篇
  2005年   972篇
  2004年   838篇
  2003年   697篇
  2002年   611篇
  2001年   467篇
  2000年   430篇
  1999年   355篇
  1998年   310篇
  1997年   320篇
  1996年   291篇
  1995年   279篇
  1994年   242篇
  1993年   229篇
  1992年   211篇
  1991年   189篇
  1990年   164篇
  1989年   137篇
  1988年   158篇
  1987年   122篇
  1986年   123篇
  1985年   178篇
  1984年   220篇
  1983年   119篇
  1982年   155篇
  1981年   127篇
  1980年   129篇
  1979年   90篇
  1978年   69篇
  1977年   76篇
  1976年   84篇
  1975年   72篇
  1974年   58篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
Introduction Failure to enter the coronary sinus (CS) with a guiding catheter and entering its tributaries remains challenging in left ventricle (LV) pacing lead implants for cardiac resynchronization therapy (CRT). A dual telescoping catheter system (8F outer/6F inner) is designed to provide the ability to adjust the catheter curve size, shape and/or reach to the patients’ anatomy avoiding the need for catheter change. Methods Five different designs for CS cannulation were randomly tested in 64 patients scheduled for CRT device implant. Results In 33 consecutive patients three adaptable telescoping guiding catheter systems were tested per patient, the adaptable catheters had higher overall cannulation success rates (68, 63 and 62%) compared to the fixed shape catheter (46%) and an greater cannulation success rate when the CS location was not known (70, 53 and 72% vs 33% for the fixed shape). In a second group of 31 CRT patients the two telescoping catheters had similar high levels of success (71–80%), with or without using the inner catheter. Conclusions The telescopic system is adaptable to a wide range of anatomical variations in patients and can result in a higher CS cannulation success rate due to its adjustability in the RA in search for the CS ostium. On top of this the inner catheter allows for sub-selecting the CS tributaries.  相似文献   
52.
Objective: To mechanically test the intact cardiac structure to determine the sequence of contraction within the myocardial mass to try to explain ejection and suction. Methods: In 24 pigs (30–85 kg), segment shortening at the site of sonomicrometer crystals was continuously recorded. The ECG evaluated rhythm, and Millar pressure transducers measured intraventricular pressure and dP/dt. Results: Study of segment shortening defined a sequence of contraction within the myocardial mass, starting at the free wall of the right ventricle and on the endocardial side of the antero-septal wall of the left. Crystal location defined underlying contractile trajectory; transverse in right ventricle followed by basal posterior left ventricle, and from the endocardial anterior wall to the posterior apical segment and finally to the epicardial side of the anterior wall. Mean shortening fraction averaged 18±3%, with endocardial exceeding epicardial shortening by 5±1%. Epicardial segment crystal displacement followed endocardial shortening by 82±23 ms in the anterior wall, and finished 92±33 ms after endocardial shortening stopped, time frame that matches the interval of fast drop of ventricular pressure and the start of suction. Conclusions: Crystal shortening fraction sequence followed the rope-like myocardial band model to contradict traditional thinking, with two starting points of excitation–contraction, the right anterior free wall of the right ventricle, and the endocardial side of the anterior wall. Active suction may be due to active shortening of the epicardial fibers of the anterior wall, because relaxation was not detected when both mitral and aortic valves were closed during the interval previously termed ‘isovolumetric relaxation’.  相似文献   
53.
54.
目的总结改良Norwood手术的临床应用经验。方法2004年7月和2005年3月分别为1例7月龄单心室伴左心室流出道梗阻女婴,采用主肺动脉和主动脉弓下缘直接吻合、主动脉肺动脉人工血管分流完成改良Norwood手术;1例出生13 d左心发育不良综合征新生儿,采用主肺动脉和主动脉弓下缘直接吻合、右心室肺动脉人工血管分流完成改良Norwood手术。结果例1术后平稳,动脉压为85~100/25~40mmHg(1 mm Hg=0.133kPa),动脉血氧饱和度为0.75~0.85,术后第3d撤离辅助呼吸,第11 d出院。例2术后平稳,动脉压为65~80/40~60mmHg,动脉血氧饱和度为0.67~0.89,术后第12 d撤离辅助呼吸,第28 d出院。结论改良Norwood手术的先进方法和技术,值得在我国推广应用。  相似文献   
55.
Cardiac allograft vasculopathy (CAV) is a major source of late posttransplant mortality. Although numerous cell types are implicated in the pathogenesis of CAV, it is unclear which cells actually induce the vascular damage that results in intimal proliferation. Because macrophages are abundant in CAV lesions and are capable of producing growth factors implicated in neointimal proliferation, they are leading end-effector candidates. Macrophages were depleted in a murine heterotopic cardiac transplant system known to develop fulminant CAV lesions. C57BL/6 hearts were transplanted into (C57BL/6 x BALB/c)F(1) recipients, which then received anti-macrophage therapy with intraperitoneal carrageenan or i.v. gadolinium. Intraperitoneal carrageenan treatment depleted macrophages by 30-80% with minimal effects upon T, B or NK cells as confirmed by flow cytometry and NK cytotoxicity assays. Carrageenan treatment led to a 70% reduction in the development of CAV, as compared to mock-treated controls (p = 0.01), which correlated with the degree of macrophage depletion. Inhibition of macrophage phagocytosis alone with gadolinium failed to prevent CAV. Macrophages may represent the end-effector cells in a final common pathway towards CAV independent of T-cell or B-cell alloreactivity and exert their injurious effects through mechanisms related to cytokine/growth factor production rather than phagocytosis.  相似文献   
56.
Video-assisted minimally invasive cardiac surgery (VAMICS) is currently performed with various indications. However, despite the increasing evidence of its effectiveness, new approaches have to be defined to simplify this procedure, minimize its potential complications and limit its costs, for a wider use in the surgical community. The limited access to the aorta is a key point in VAMICS and mandates specific clamping modalities with their own limitations, costs and drawbacks. The Portaclamp (Cardio Life Research SA, Louvain la Neuve, Belgium), a new autoguided extravascular aortic cross-clamping system, has been recently proposed to facilitate VAMICS. Herein, we describe the Portaclamp approach and report our indications and preliminary clinical experience so to define its role in VAMICS.  相似文献   
57.
目的 探讨老年排尿功能障碍的神经机制。方法 利用水浴条件下离体逼尿肌条张力测定技术,观察老龄Wistar大鼠膀胱逼尿肌条对不同浓度卡巴可、去甲肾上腺素、ATP的收缩反应改变;阿托品对卡巴可诱导逼尿肌收缩的舒张反应改变;异丙肾上腺素对电刺激诱导逼尿肌收缩的舒张反应改变。结果 与青龄组相比,老龄大鼠膀胱逼尿肌对ATP的收缩反应显著增强,对异丙肾上腺素的舒张反应在高浓度时增强;对卡巴可、阿托品、去甲肾上腺素的反应没有差异。结论 老龄大鼠排尿功能障碍可能与β-肾上腺素能、嘌呤能神经改变有关。  相似文献   
58.
成年人智力发育与年龄和教育的关系   总被引:2,自引:0,他引:2  
本文对韦氏成人智力量表中国修订本25岁及其以上成年人城乡样本共1976人在校正各年龄组的文化程度以后,比较了年龄和教育因素对成年人智力发展的影响。结果发现:与晶体智力有关的测验成绩并不随年龄增大而下降,某些测验(如知识;领悟等)甚至呈上升趋势;与流体智力有关的测验成绩随年龄的增大而下降;而测量精神运动速度(数字符号测验)的成绩受年龄影响最为明显。看来流体-晶体智力理论能较好地解释成年人的典型智力发  相似文献   
59.
本文通过对3月龄、18月龄、24月龄雄性大鼠下丘脑去甲肾上腺素(NE)、多巴胺(DA)、5-羟色胺(5-HT)、5-羟吲哚乙酸(5-HIAA),和下丘脑垂体促甲状腺释放激素(TRH)、垂体、血甲状腺释放激素(TSH)、血甲状腺激素(T_3、T_4)的测定,研究了大鼠下丘脑神经递质与甲状腺轴机能的增龄性变化,并在此基础上探讨了补益中药对老龄大鼠下丘脑—垂体—甲状腺机能的作用。结果提示:老龄大鼠下丘脑机能的减退是甲状腺轴机能减退的重要原因;补益中药可能改善了老龄大鼠下丘脑的调控机能,进而延缓了甲状腺轴机能的老年性变化。  相似文献   
60.
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