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   19346篇
  免费   1576篇
  国内免费   550篇
耳鼻咽喉   70篇
儿科学   344篇
妇产科学   262篇
基础医学   1268篇
口腔科学   781篇
临床医学   2080篇
内科学   4663篇
皮肤病学   90篇
神经病学   1395篇
特种医学   1792篇
外国民族医学   3篇
外科学   2303篇
综合类   2524篇
现状与发展   1篇
预防医学   358篇
眼科学   1282篇
药学   1263篇
  7篇
中国医学   400篇
肿瘤学   586篇
  2024年   23篇
  2023年   349篇
  2022年   502篇
  2021年   899篇
  2020年   831篇
  2019年   847篇
  2018年   830篇
  2017年   735篇
  2016年   697篇
  2015年   766篇
  2014年   1228篇
  2013年   1431篇
  2012年   981篇
  2011年   1121篇
  2010年   920篇
  2009年   958篇
  2008年   882篇
  2007年   932篇
  2006年   801篇
  2005年   654篇
  2004年   541篇
  2003年   501篇
  2002年   408篇
  2001年   382篇
  2000年   293篇
  1999年   260篇
  1998年   274篇
  1997年   225篇
  1996年   219篇
  1995年   207篇
  1994年   223篇
  1993年   172篇
  1992年   141篇
  1991年   131篇
  1990年   108篇
  1989年   111篇
  1988年   82篇
  1987年   85篇
  1986年   83篇
  1985年   102篇
  1984年   97篇
  1983年   48篇
  1982年   72篇
  1981年   72篇
  1980年   60篇
  1979年   39篇
  1978年   47篇
  1977年   28篇
  1976年   24篇
  1974年   14篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
A symptomatic 1,400 g premature triplet underwent successful transcatheter coil embolization of patent arterial duct using the umbilical artery. One 3 mm x 3 cm Flipper coil was used with no angiographic residual shunt. To the best of our knowledge, this is one of the smallest preterm infants to undergo this transcatheter procedure.  相似文献   
72.
Before meaningful conclusions can be drawn from clinical measures of cerebral blood perfusion, the precision of the measurement must be determined and set in the context of inter- and intrasubject sources of variability. This work establishes the reproducibility of perfusion measurements using the noninvasive MRI technique of continuous arterial spin labeling (CASL). Perfusion was measured in 34 healthy normal subjects. Intersubject variability was assessed, and age and gender contributions were estimated. Intersubject variation was found to be large, with up to 100% perfusion difference for subjects of the same age and gender. Repeated measurements in one subject showed that perfusion remains remarkably stable in the short term when compared with intersubject variation and the large capacity for perfusion change in the brain. A significant decrease in the ratio of gray-matter to white-matter perfusion was found with increasing age (0.79% per year (P < 0.0005)). This appears to be due mainly to a reduction in gray-matter perfusion, which was found to decrease by 0.45% per year (P = 0.04). Regional analysis suggested that the gray-matter age-related changes were predominantly localized in the frontal cortex. Whole-brain perfusion was 13% higher (P = 0.02) in females compared to males.  相似文献   
73.
A new approach to modeling the signal observed in arterial spin labeling (ASL) experiments during changing perfusion conditions is presented in this article. The new model uses numerical methods to extend first-order kinetic principles to include the changes in arrival time of the arterial tag that occur during neuronal activation. Estimation of the perfusion function from the ASL signal using this model is also demonstrated. The estimation algorithm uses a roughness penalty as well as prior information. The approach is demonstrated in numerical simulations and human experiments. The approach presented here is particularly suitable for fast ASL acquisition schemes, such as turbo continuous ASL (Turbo-CASL), which allows subtraction pairs to be acquired in less than 3 s but is sensitive to arrival time changes. This modeling approach can also be extended to other acquisition schemes.  相似文献   
74.
目的探讨肾动脉狭窄介入治疗前后血清脑利钠肽BNP水平的变化及意义。方法采用回顾性调查方法,对肾动脉狭窄介入治疗前后血清脑利钠肽水平的变化进行分析。结果肾动脉狭窄介入治疗再通后,血清BNP水平出现下降(P〈0.01)。结论血清BNP水平的变化对肾动脉狭窄介入治疗后疗效的评价具有一定的临床指导意义。  相似文献   
75.
Summary Bronchus stump insufficiency following lung resection, with an average incidence of 4%, is a serious complication which carries a mortality of up to 90%. Operative transthoracic approaches have been largely unsatisfactory because of the high operative risk and rapidly spreading infection. In an experimental study on 18 pigs, endoscopic occlusion of infected bronchus stump fistulae was achieved with fibrin sealant (1 ml, 500 units/ml thrombin, 3500 units/ml aprotinin) applied via a flexible bronchoscope. During autopsy, all bronchus stump fistulae were found to have healed after the second postoperative week. Transitory local abscesses of the pleura could be prevented by high-dose systemic antibiotic therapy for 5 postoperative days but not by antibiotics added to the fibrin sealant. This endoscopic method has already been performed successfully in 3 clinical cases; additional sclerotherapy with (2–3 ml Ethoxysclerol applied around the fistula orifice was carried out before fibrin sealing to stimulate fibrosis. Endoscopic controls demonstrated fistula closure by granulation tissue after 2 weeks. This procedure could become the method of choice for infected postoperative fistulae of the bronchus stump and should be attempted in any case before operative approaches are considered.  相似文献   
76.
在53只乌拉坦麻醉家兔身上,观察到延髓孤束核(NTS)区注射γ-氨基丁酸(GABA)使血压显著下降,安定(DZ)有相似的降压效应,荷包牡丹碱(BIC)和印防己毒素(PIC)则使血压升高;促甲状腺素释放激素(TRH)和甲硫脑啡肽(MTP)对血压无明显影响;延髓的另一些区域应用GABA等药物后血压变化不明显;提示GABA能神经递质系统参与心血管活动的抑制性中枢调节,NTS区是其作用部位之一。  相似文献   
77.
目的探讨选择性/超选择性阻断出入肝血管后解剖性肝切除对肝脏疾病患者手术中失血量、术后肝功能、并发症、住院时间等相关因素的影响。方法选择/超选择出入肝血管阻断后解剖性肝切除66例,其中肝段切除22例、右半肝切除12例,左半肝切除6例,Ⅱ Ⅲ段肝切除19例,Ⅵ Ⅶ段肝切除5例,Ⅴ Ⅷ段肝切除2例。观察其对术中失血量、输血量、术后肝功能、术后并发症、术后住院时间等的影响。结果本组切除术中出血量(437±123)m l,所有病例手术中均未输血;术后患者肝功能损伤程度较轻,54例术后1周恢复至术前水平;无肝功能衰竭等相关并发症;术后平均住院时间13.1 d,无围手术期死亡。结论对于适应症明确的肝脏疾病,通过选择性或超选择性出入肝血流阻断后行肝脏解剖性切除可有效减少术中出血、降低术后相关并发症的发生。  相似文献   
78.
Purpose To develop an easy-to-use, dentition planning method which is based on three-dimensional (3D) computer planning technology to replace conventional plaster-cast occlusion planning techniques. Methods The optimal dental occlusion is defined according to the condition of centric occlusion, i.e. after bringing occlusal surfaces of mandibular and opposing maxillary arches into identical 3D position. This identical position of occlusal surfaces represents the common reference frame for the 3D manipulation of all graphical elements. The planning procedure involves the following steps: (1) the optimal occlusal surface is approximated as triangle and localized both on the maxilla and mandible; (2) the original volumetric model is resampled according to the occlusal orientations; (3) the program reads in the models of ideal upper and lower dental arches from files, reshapes those to the patient anatomy and visualizes the local alignment on separate panels for mesiodistal and faciolingual inclinations. The final goal of the proposed method is to combine the requirements of functional and aesthetic designs and create an input for orthodontics, implantology and maxillofacial surgery. Results In the present study the optimal dental occlusion is created by image resampling after bringing the occlusal surfaces of mandibular and opposing maxillary arches into identical 3D position. This identical position of occlusal surfaces represents the common reference frame for manipulation of all graphical elements. Conclusions The proposed graphical environment was able to fit the elements of the ideal dentition curve to patient computed tomography under predefined centric occlusion. Rotation and scaling transformations of teeth were possible in the reformatted volumetric views about any of the axes of the teeth’s own reference space.  相似文献   
79.
超早期大剂量高压氧治疗急性脑卒中的实验研究   总被引:3,自引:0,他引:3  
目的:探讨大剂量高压氧(HBO)治疗急性脑卒中的疗效及机制。方法:以大鼠大脑中动脉永久性阻塞模型为对象;以神经功能评分和梗死容积为指标,对9和18h两种HBO方案超早期治疗急性缺血性脑卒中的疗效进行评估。对不同时间缺血组织超微结构进行观察。结果:HBO后神经功能预后明显好于对照组(P<0.01),5d时梗死容积比对照组显著降低(P<0.01),缺血组织毛细血管周围水肿和神经元损伤明显减轻。结论:超早期大剂量HBO治疗急性脑卒中疗效显著,过大剂量HBO可能加重过氧化损伤。  相似文献   
80.
目的研究分子吸附再循环系统(MARS)对冠心病并发重度脓毒症患者心率和动脉压的影响.方法对2002年11月至2004年2月在ICU治疗的冠心病并发重度脓毒症患者所进行的12次床边MARS治疗有关资料进行回顾性分析和探讨.结果MARS治疗4 h后患者心率显著减慢,收缩压、舒张压和平均动脉压明显升高.结论MARS可改善MODS患者血流动力学指标.  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