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   6560篇
  免费   284篇
  国内免费   173篇
耳鼻咽喉   149篇
儿科学   113篇
妇产科学   25篇
基础医学   483篇
口腔科学   179篇
临床医学   855篇
内科学   488篇
皮肤病学   10篇
神经病学   226篇
特种医学   326篇
外科学   1543篇
综合类   1222篇
预防医学   338篇
眼科学   18篇
药学   524篇
  4篇
中国医学   372篇
肿瘤学   142篇
  2024年   23篇
  2023年   106篇
  2022年   197篇
  2021年   243篇
  2020年   243篇
  2019年   221篇
  2018年   234篇
  2017年   194篇
  2016年   210篇
  2015年   228篇
  2014年   556篇
  2013年   465篇
  2012年   432篇
  2011年   526篇
  2010年   464篇
  2009年   344篇
  2008年   351篇
  2007年   312篇
  2006年   275篇
  2005年   217篇
  2004年   192篇
  2003年   135篇
  2002年   121篇
  2001年   108篇
  2000年   83篇
  1999年   83篇
  1998年   62篇
  1997年   49篇
  1996年   40篇
  1995年   42篇
  1994年   41篇
  1993年   31篇
  1992年   25篇
  1991年   20篇
  1990年   14篇
  1989年   14篇
  1988年   11篇
  1987年   14篇
  1986年   13篇
  1985年   10篇
  1984年   11篇
  1983年   4篇
  1982年   15篇
  1981年   9篇
  1980年   6篇
  1979年   6篇
  1978年   5篇
  1977年   4篇
  1976年   4篇
  1975年   2篇
排序方式: 共有7017条查询结果,搜索用时 31 毫秒
71.
目的 简化人体上肢结构,建立两刚体系统动力学模型,并对其进行数值求解。方法 以卡尔登角为广义坐标,运用多刚体动力学理论,建立上肢的动力学方程;运用MATHEMATICA计算软件对方程进行正、反数值求解并进行了比较。结果 得到了上肢的两刚体动力学方程和数值解,对比计算结果表明,将已知运动带入方程求得的主动力作为已知力反求得的卡尔登角与已知运动的卡尔登角基本一致,而且在反解时会出现奇点。结论 运用MATHEMATICA计算软件求解复杂的上肢两刚体系统方程,相当方便,为免奇点出现,应在适当范围内进行求解,在误差允许的范围内,求得的解是可以接受的。  相似文献   
72.
It is yet unknown how upper body exercise combined with high ambient temperatures affects plasma testosterone and cortisol concentrations and furthermore, how these hormones respond to exercise in people suffering spinal cord injuries. The purpose of this study was to characterize plasma testosterone and cortisol responses to upper body exercise in wheelchair athletes (WA) compared to able-bodied individuals (AB) at two ambient temperatures. Four WA [mean age 36 (SEM 13) years, mean body mass 66.9 (SEM 11.8) kg, injury level T7–T11], matched with five AB [mean age 33.4 (SEM 8.9) years, mean body mass 72.5 (SEM 13.1) kg] exercised (cross-over design) for 20 min on a wheelchair ergometer (0.03 kg resistance · kg−1 body mass) at 25 °C and 32 °C. Blood samples were obtained before (PRE), at min 10 (MID), and min 20 (END) of exercise. No differences were found between results obtained at 25 °C and 32 °C for any physiological variable studied and therefore these data were combined. Pre-exercise testosterone concentration was lower (P < 0.05) in WA [18.3 (SEM 0.9) nmol · l−1] compared to AB [21.9 (SEM 3.6) nmol · l−1], and increased PRE to END only in WA. Cortisol concentrations were similar between groups before and during exercise, despite higher rectal temperatures in WA compared to AB, at MID [37.21 (SEM  0.14) and 37.02 (SEM  0.08)°C, respectively] and END [37.36 (SEM 0.16) and 37.19 (SEM 0.10)°C, respectively]. Plasma norepinephrine responses were similar between groups. In conclusion, there were no differences in plasma cortisol concentrations, which may have been due to the low relative exercise intensities employed. The greater exercise response in WA for plasma testosterone should be confirmed on a larger population. It could have been the result of the lower plasma testosterone concentrations at rest in our group. Accepted: 4 September 2000  相似文献   
73.
目的探讨前路、后路、前后路联合手术治疗胸腰椎爆裂骨折的特点。方法依据对患者所选择的前路、后路、前后路联合手术术式分为三组,进行影像学评价和神经功能评价。结果各组末次随访脊髓功能评价分级提高情况采用R×C表x2检查方法进行统计学分析,各组差异无显著意义。各组术后cobb氏角改善率应用秩和检验方法进行统计学分析,各组差异无显著意义。结论我们综合应用Denis和McAfee的分型,结合了骨折形态、损伤机制和稳定性评价,对胸腰椎爆裂骨折的治疗有较好的指导意义。手术方式的选择更多基于脊柱机械性稳定性、神经性稳定性评价。综合考虑骨折部位、骨折后时间、患者年龄、工种以及术者对入路的熟悉程度等。  相似文献   
74.
目的 探讨后路经皮内窥镜下颈椎椎间盘切除术的安全范围。 方法 选取20具成人颈椎标本,分别测量C3/C4至C6/C7各节段左右两侧V点与硬脊膜外侧距离、V点与椎动脉水平及垂直距离、小关节面宽度,并进行统计学比较。 结果 V点与硬脊膜外侧距离为:左(1.31±0.32)~(2.46±0.60) mm,右(1.29±0.35)~(2.75±0.45) mm,各节段间差别有统计学意义,同一水平左右差别无统计学意义;V点与椎动脉水平距离为:左(2.17±0.42)~(5.10±0.93) mm,右(1.99±0.39)~(5.00±0.71) mm,各节段间差别有统计学意义,同一水平左右差别无统计学意义;V点与椎动脉垂直距离为:左(11.05±1.06)~(13.47±1.12)mm,右(11.33±1.20)~(13.61±1.01)mm,同一水平左右侧差别有统计学意义,节段间比较C3/C4与C4 /C5无明显差异,其余节段间差别均有统计学意义;小关节面宽度为:左(10.79±0.93)~(12.66±0.88) mm,右(10.86±0.68)~(12.54±0.70)mm。 结论 后路经皮内窥镜下颈椎椎间盘切除术的安全范围宜控制在距V点内侧C3/C4至C6/C7各水平1.20~2.00 mm;磨除范围距V点外侧C3/C4至C6/C7各水平超过2.00~5.00 mm时可能到达椎动脉体表投影处,因此需注意此时的手术进入深度宜控制在:C3/C4~C6/C7各节段距V点11.00~14.00 mm。  相似文献   
75.
Summary The main purpose of this study was to evaluate the reproducibility of electromyographic (EMG) measurements and specifically to test a calibration procedure with submaximal test contractions. Bipolar surface electrodes (20 mm fixed distance) were repositioned by a tracing sheet on both trapezius muscles, halfway between acromion and processus prominens. Submaximal test contractions were performed by keeping both arms straight abducted 90° and forward flexed 10° for 15-s periods. The arm position could be precisely reproduced in the frontal plane, but deviated forwards by 4° in the horizontal plane, where the sensitivity of the EMG response to arm position was lowest. The electrodes were repositioned within a radius of 3 mm with a probability of 90%. Large deviations in the EMG response were found within this radius and a significant depression of the EMG response was recorded over the middle part of the muscle (the innervation zone?). This change in sensitivity of the EMG response with electrode position occurred in parallel for the test and maximal contractions. The total coefficient of variation was estimated to be 23% for recurrent EMG measurements using the calibration procedure described.  相似文献   
76.
The aim of the present study was to compare electromyographic responses during arm exercises with a crank rate chosen spontaneously (TS) or set at 20% below or above (T–20, T+20) the spontaneously chosen crank rate (SCCR). Ten male physical education students performed arm exercises with intensities ranging from 20% to 80% of maximal power. Muscular activity levels were analysed for the biceps brachii and the triceps brachii muscles using integrated rectified surface electromyography (iEMG). All values were presented as the mean and standard deviation. During TS, the sum of iEMG for the two muscles studied was significantly (P<0.05) lower than during T+20 for each power output. No significant differences were observed in iEMG values between TS and T–20. The hypothesis that SCCR relates to a minimisation of muscle activation during an upper body exercise was not confirmed. Variations superior or inferior to a 20% increase of the iEMG responses do not influence it. Moreover, the selection of crank rates depends on the power output and the SCCR increased significantly (P<0.05) with increasing power output.  相似文献   
77.
The effects of upper airway (UA) cool air and CO2 on breathing and on laryngeal and supraglottic resistances were studied in anaesthetised rats breathing spontaneously through a tracheostomy. Warm, humidified air containing 0, 5 and 9–10% CO2 and cool, room-humidity air were delivered at constant flow to either the isolated larynx to exit through a pharyngotomy or to the supraglottic UA to exit through the mouth and/or nose (nose open or sealed). Spontaneous tracheal airflow and UA airflows, temperatures and pressures were recorded. CO2 had no effect on breathing but caused a slight increase in laryngeal resistance which was abolished by cutting the superior laryngeal nerves (SLN). Cool air caused a decrease in respiratory frequency and/or peak inspiratory flow when applied to the isolated larynx or to the supraglottic airway with the nose closed. These effects were abolished by SLN section. With the nose open, the ventilatory inhibition was not abolished by SLN section. Cool air also caused substantial decreases in laryngeal and supraglottic resistances which were attenuated by SLN section and which persisted following recurrent laryngeal nerve section. In conclusion, whilst UA cooling inhibits breathing and decreases UA resistances, UA CO2 has minimal effects.  相似文献   
78.
目的:探索脑卒中患者促进上肢运动功能恢复中头针与镜像疗法联合应用的临床价值。方法:选取株洲市中心医院2021年8月至2022年11月期间收治的60例脑卒中后上肢功能障碍患者,以随机分组的方式分为两组,每组30例。其中常规康复训练联合镜像治疗纳入对照组,在对照组基础上增加头针治疗纳入观察组。在治疗4周后,比较两组患者临床治疗有效性、Fugl–meyer运动功能评定量表(FMA)上肢部分评分以及Brunnstrom分期。结果:两组患者治疗后FMA评分均高于治疗前,且观察组患者治疗后FMA评分高于对照组,差异具有统计学意义(P<0.05)。观察组患者治疗后上肢Brunnstrom运动功能分期结果优于对照组,差异具有统计学意义(Z=–2.101,P <0.05)。观察组患者治疗后手Brunnstrom运动功能分期结果优于对照组,差异具有统计学意义(Z=–2.152,P <0.05)。结论:在恢复早期,头针、镜像疗法与常规康复训练有效结合,对脑卒中患者软瘫期上肢运动功能恢复具有积极作用。  相似文献   
79.
摘 要目的:观察血府逐瘀汤预防上肢皮瓣术后血管危象的临床疗效。 方法:选取 2022 年 1 月至 2023 年 1 月就诊于 赣州市南康区第一人民医院的 60 例行上肢皮瓣转移术的患者,采用简单数字随机法分为观察组和对照组,各 30 例。术后 对照组患者常规应用 “ 三抗 ” 治疗,观察组患者在 “ 三抗 ” 的基础上加服血府逐瘀汤剂,比较两组患者术后皮瓣的血运情 况、总体疗效。 结果:术后 3 d、7 d,观察组患者皮瓣肿胀程度优于对照组,差异具有统计学意义(Z 分别为 –2.28、–3.46, P < 0.05);术后 1 d、3 d、7 d,观察组患者毛细血管反应优于对照组,差异具有统计学意义(Z 分别为 –6.89、–6.29、–7.35, P < 0.05);观察组患者疗效优于对照组,差异具有统计学意义(Z = –3.44,P < 0.05)。 结论:上肢皮瓣术后的患者在常 规 “ 三抗 ” 的基础上,加用血府逐瘀汤可有效减少血管危象的发生,提高皮瓣成活率。  相似文献   
80.
目的探讨超声内镜与胃镜对上消化道黏膜下肿瘤的诊断效果。方法选择2015年3月至2018年2月确诊的60例上消化道黏膜下肿瘤患者,均行胃镜检查和超声内镜检查,分析其与病理检查的符合率以及超声内镜检查的回声特点,并记录超声内镜检查的敏感性和特异性。结果以病理检查结果为标准,超声内镜检查的符合率为90.00%,明显高于胃镜检查的73.33%(P <0.05)。超声内镜检查对黏膜肌层肿瘤诊断的敏感性为90.32%,特异性为93.55%;对黏膜下层肿瘤诊断的敏感性为93.33%,特异性为93.75%;对固有肌层肿瘤诊断的敏感性为85.71%,特异性为97.87%。结论与胃镜检查相比,超声内镜在上消化道黏膜下肿瘤中的诊断价值更高,能够对病变的性质、部位及来源作出准确的诊断。  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