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   25437篇
  免费   1866篇
  国内免费   229篇
耳鼻咽喉   70篇
儿科学   649篇
妇产科学   513篇
基础医学   2669篇
口腔科学   214篇
临床医学   4783篇
内科学   2274篇
皮肤病学   109篇
神经病学   3446篇
特种医学   349篇
外科学   1895篇
综合类   2373篇
一般理论   4篇
预防医学   5644篇
眼科学   45篇
药学   1496篇
  15篇
中国医学   244篇
肿瘤学   740篇
  2024年   56篇
  2023年   559篇
  2022年   956篇
  2021年   1285篇
  2020年   1237篇
  2019年   1271篇
  2018年   1158篇
  2017年   1114篇
  2016年   1096篇
  2015年   1017篇
  2014年   1869篇
  2013年   2421篇
  2012年   1530篇
  2011年   1668篇
  2010年   1287篇
  2009年   1279篇
  2008年   1295篇
  2007年   1178篇
  2006年   907篇
  2005年   666篇
  2004年   555篇
  2003年   447篇
  2002年   354篇
  2001年   293篇
  2000年   255篇
  1999年   227篇
  1998年   165篇
  1997年   175篇
  1996年   113篇
  1995年   126篇
  1994年   108篇
  1993年   88篇
  1992年   69篇
  1991年   61篇
  1990年   41篇
  1989年   42篇
  1988年   43篇
  1987年   29篇
  1986年   34篇
  1985年   60篇
  1984年   58篇
  1983年   35篇
  1982年   36篇
  1981年   37篇
  1980年   39篇
  1979年   42篇
  1978年   28篇
  1977年   20篇
  1976年   21篇
  1974年   24篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
To investigate the possibility of a long-term applicable left ventricular assist device, a 23 mm outer diameter and 31 g weight implantable aortic valvo-pump was developed. It consists of a rotor and a stator; the rotor has a driven magnets assemble and an impeller, the stator has a motor coil with iron core and a outflow guide vane. The device locates the position of aortic valve, delivers the blood directly from left ventricle to aorta. Neither connecting conduits nor “bypass” circuits are necessary. Therefore, the device has promisingly better antithrombogenicity than other heart pumps. In hemodynamic testing, the pump can produce a blood flow of 7 l/min volume with 50 mmHg pressure increase at 15,000 rpm rotating speed, and at zero flow rate the pump can maintain a diastolic pressure over 80 mmHg at same rotating speed. For further studies the blood compatibility and the durability of the device are of most importance.  相似文献   
72.
不同营养支持方式对肠外瘘患者人体组成改善作用之比较   总被引:1,自引:1,他引:0  
目的观察不同营养支持方式对肠外瘘患者人体组成的改善作用。方法30例肠外瘘患者分成两组各15例,分别给予全肠外营养支持(TPN)或全肠内营养支持(TEN),观察10d前后患者人体组成及血清胰岛素样生长因子-1(IGF-1)的变化。结果10d后所有患者的体重指数(BMI)与体细胞群(BCM)显著改善,而TEN组患者10d前后BCM增加幅度更明显,分别为(27.5±0.8)kg和(29.0±0.6)kg,Day10与Day0相比,P<0.01。两组患者总体水(TBW)与细胞内水(ICW)均增加,尤其ICW,Day10与Day0相比,TEN组P<0.01;TPN组P<0.05。血清IGF-1在两组患者治疗后均有显著上升,TEN组增加幅度更明显,Day0为(175.0±32.9)ng/ml,Day10为(255.5±34.1)ng/ml,与Day0比较,P<0.01;与TPN组比较,P<0.05。IGF-1的变化与BCM的改善显著正相关(r2=0.16,P<0.05)。结论营养支持治疗能显著改善肠外瘘患者的体细胞群,纠正细胞内、外水的异常分布,而EN作用更明显。  相似文献   
73.
学龄前儿童社会生活能力的影响因素研究   总被引:2,自引:0,他引:2  
喻晖  张静 《医学与社会》2004,17(3):26-27,31
目的 了解学龄前儿童社会生活能力现状及影响因素。方法 采用自拟“儿童一般情况调查表”及“婴儿一初中生社会生活能力量表”进行问卷调查,采用x^2检验、logistic逐步回归分析对学龄前儿童社会生活能力影响因素进行分析。结果 多因素logistic逐渐回归分析显示:影响学龄前儿童社会生活能力发展的因素主要有儿童年龄大小、与小朋友相处好坏、母亲文化程度、父母对儿童的喜爱程度、父母听取孩子的意见情况、对孩子独立能力培养的态度等。结论 儿童年龄、母亲文化程度、教育方式对学龄前儿童社会生活能力的形成和发展起重要作用。  相似文献   
74.
The aim of the inquiry was to examine the social network–mortality association within a wider multivariate context that accounts for the effects of background framing forces and psychobiological pathways. The inquiry was based upon the Berkman et al. (2000) conceptual model of the determinants of health. Its main purpose was to identify the salient network correlates of 7-year all cause mortality among Jewish men and women, aged 70 and over, in Israel (n = 1,811). The investigation utilized baseline data from a national household survey of older adults from 1997 that was linked to records from the National Death Registry, updated through 2004. At the time of the study, 38% of the sample had died. Multivariate Cox hazard regressions identified two main network-related components as predictors of survival: contact with friends, a social network interaction variable, and attendance at a synagogue, a social engagement variable. Friendship ties are seen to uniquely reduce mortality risk because they are based on choice in nature, and reflect a sense of personal control. Synagogue attendance is seen to promote survival mainly through its function as a source of communal attachment and, perhaps, as a reflection of spirituality as well. Other possibly network-related correlates of mortality were also noted in the current analysis—the receipt of instrumental support and the state of childlessness. The study on which this article is based was made possible by grants from the Israel Ministry of Science and Technology to the Israel Gerontological Data Center.  相似文献   
75.
躯干运动和负重时对足底支撑面侧向横移的姿势控制   总被引:3,自引:0,他引:3  
目的:本研究假设自主运动命令和姿势控制信号间有冲突,因此设计在附加重物和不同自主任务的同时给予足底一个模拟受滑的干扰(横移)来观察姿势变化并分析其是否受冲突命令或者力学参数的影响.方法:受试者在执行各种不同的自主任务时,随机给予足底支撑面一个左侧或右侧的横移干扰.这些不同的自主任务包括不负重静止站立、静止站立单手负重5kg、负重5kg站立并躯干静止侧屈15°、负重5kg动态地提重物和放重物5项任务.测量和分析下列参数:中心压力的侧位移(COP)、躯干和股部在冠状面上的角位移和腹内压(IAP).结果:干扰离开质量(向右)、始反应超射的幅度、达到终平衡的时间和达到平衡前COP位移的次数都增加,这种情况可以看作是为了再获得平衡的姿势反应效率降低,因此,如果质量的重力效果能对抗干扰,则再获得平衡的反应效率甚至可以被增进.结论:提重和负重是危害姿势反应效率的因素,因为提重和负重改变了重力效果,加大了对躯干的干扰.在动态条件下躯干的运动不是被横移干扰增强就是被横移干扰抵消,并没有显著地影响改变最终平衡位置姿势校正的效应.因此附加任务的同时给一个支持面上的横移干扰,姿势控制的效应可以被抵消.这个减低的效应可以引起脊柱周围结构的负荷增加和增加受伤的危险性.但是,在恰当地放置负重的位置时,反而可以增进躯干控制和协助恢复姿势平衡.  相似文献   
76.
社会支持对考试应激的影响   总被引:2,自引:0,他引:2  
目的了解社会支持对考试应激的影响。方法采用焦虑自评量表和社会支持量表分别对727个学生考试前1个月、考试期间考试焦虑分数及社会支持情况进行调查,比较分析考试焦虑分数与社会支持因素的关系。结果考试焦虑分数与客观支持、来自同学和老师的主观支持以及社会支持的利用度成反比。结论家长和学校给予学生足够的社会支持,以及让学生参加适当的社会活动,培养他们利用社会支持的能力,有助于让学生减缓考试应激的水平  相似文献   
77.
目的 探讨失眠症患者心理防御特征和社会支持 ,并分析两者的关系。方法 采用心理防御方式问卷 (DSQ )、社会支持评定量表 (SSRS)对失眠症患者和正常健康者各 5 0例进行评定。结果 患者组心理防御方式 (不成熟型、中间型防御因子和掩饰因子的因子分高 ,成熟防御因子分低 )和社会支持 (社会支持总分、主观支持分、对支持利用度低 )与对照组相比差异有显著性 (P <0 .0 5或 0 .0 1) ;相关分析发现 ,患者组不成熟防御机制与SSRS的支持总分、主观支持分、对支持利用度呈负相关 (P均 <0 .0 5 ) ,中间型防御机制与SSRS的主观支持呈负相关 (P <0 .0 5 )。结论 失眠症患者心理防御机制的成熟程度较正常人低 ,社会支持差 ,两者存在一定的关系。  相似文献   
78.
Abstract: Recent studies have shown that liver support systems based on viable hepatocytes can prolong life in animal models of acute liver failure. Now the time has come to elucidate the design characteristics that are essential to construct an efficient bioreactor. The gold standard remains the intact liver. Despite the very high cell density in this organ, individual cell perfusion is guaranteed resulting in low diffusional gradients which are essential for optimal mass transfer. These conditions are not met in bioreactors based on hollow fiber membranes. Moreover, the semipermeable membranes can foul and act as a diffusional barrier between the hepatocytes and the blood or plasma of the recipient. We devised a novel bioreactor for use as a bioartificial liver that does not include hollow fiber membranes for blood or plasma perfusion. The device is based on an integral oxygenator and a nonwoven polyester matrix material for hepatocyte culture as small aggregates. The efficacy of this original design was tested in rats with liver ischemia. Preliminary results show statistically significantly improved survival; life was prolonged 100% compared to the control experiments.  相似文献   
79.
Abstract: Cardiopulmonary support (CPS) requires durability of the oxygenator. The life span of the oxygenator is affected by various clinical factors, including patient condition, perfusion condition, and equipment usage. Predictors for the durability of oxygenators were evaluated clinically in this study. Thirty-two patients, who had undergone CPS during the last 3 years in our institute were assigned to this study. Fifty oxygenators had been used (Capiox SX in 19, CB Maxima in 23, and AL-6000 in 8). Significant predictors for the durability of oxygenators were evaluated by nonparametric survival analysis and proportional hazards regression analysis. Univariate regression analysis revealed 6 significant predictors for the life span of oxygenators. These were the oxygenator type, type of centrifugal pump, acidosis with blood pH less than 7.35, base excess less than -5, blood glutamic-oxaloacetic transaminase (GOT) levels greater than 1,000 IU, and blood lactate dehydrogenase (LDH) levels greater than 3,000 IU. After multivariate analysis, there remained only 2 significant predictors. An oxygenator used with a noncoated CPS system (Capiox SX with Capiox EBS) proved to have a significantly shorter life span than one used with a heparin-coated system (CB Maxima or AL-6000 with CB BP-80) (hazards ratio, 3.588, p = 0.0065). Patient conditions, which revealed acidosis with less than -5 of base excess, significantly shortened the life of the oxygenator (hazards ratio, 3.595, p = 0.0188).  相似文献   
80.
Abstract: Different mechanical circulatory support systems (MCSS) have been in clinical use since 1987 to keep patients alive by assisting the heart during cardiac recovery after open heart surgery, myocardial infarction, acute graft failure after heart transplantation, or as a bridge to transplantation in heart transplant candidates. Four different hospitals in Germany used the Berlin Heart Assist Device. Up until 1993, there were 22 patients in the "recovery" group; 4 patients were weaned from the system, and only 1 patient was discharged from the hospital. In 112 patients the Berlin Heart Assist Device was implanted for the purpose of a bridge to transplantation, 68 were transplanted and 46 patients left the hospital. It was concluded that patients may be kept alive with this system for weeks and months after any kind of cardiogenic shock. Complete cardiac recovery may be achieved in patients with early posttransplant graft failure. Reliable prediction of outcome in bridge–to–transplantation patients requires further experience and improvement of system components.  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