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   925篇
  免费   73篇
  国内免费   28篇
耳鼻咽喉   2篇
儿科学   62篇
妇产科学   12篇
基础医学   88篇
口腔科学   48篇
临床医学   117篇
内科学   195篇
皮肤病学   13篇
神经病学   18篇
特种医学   253篇
外科学   54篇
综合类   18篇
预防医学   61篇
眼科学   4篇
药学   44篇
肿瘤学   37篇
  2021年   6篇
  2020年   2篇
  2019年   7篇
  2018年   18篇
  2017年   8篇
  2016年   8篇
  2015年   16篇
  2014年   19篇
  2013年   12篇
  2012年   7篇
  2011年   22篇
  2010年   36篇
  2009年   23篇
  2008年   12篇
  2007年   31篇
  2006年   24篇
  2005年   14篇
  2004年   14篇
  2003年   20篇
  2002年   16篇
  2001年   14篇
  2000年   12篇
  1999年   19篇
  1998年   62篇
  1997年   71篇
  1996年   78篇
  1995年   50篇
  1994年   38篇
  1993年   45篇
  1992年   21篇
  1991年   13篇
  1990年   21篇
  1989年   41篇
  1988年   41篇
  1987年   31篇
  1986年   30篇
  1985年   31篇
  1984年   8篇
  1983年   10篇
  1982年   12篇
  1981年   10篇
  1980年   12篇
  1979年   3篇
  1978年   4篇
  1977年   13篇
  1976年   10篇
  1975年   6篇
  1969年   1篇
  1966年   1篇
  1950年   1篇
排序方式: 共有1026条查询结果,搜索用时 15 毫秒
101.
So then, another year, but the same old desires revived indeed.Rather than take a Latin text as a point of departure for thiseditorial, as has been my past habit [1], I have chosen to considerthe Rubaiyat of Omar Khayyam, here in its most famous Englishtranslation, that of Edward Fitzgerald. The 11th century Persian scholar, Omar Khayyam, who we todayremember mostly as the poet author of the quatrains, was during  相似文献   
102.
103.
The dynamic signal intensity changes at magnetic resonance (MR) imaging in active and chronic wallerian degeneration in the corticospinal tract were evaluated. Forty-three patients with wallerian degeneration seen on MR images after cerebral infarction were studied. When possible, patients with acute stroke were examined with MR imaging prospectively at the onset of symptoms and then at weekly intervals for several months. Focal infarction without distal axonal degeneration is demonstrated for the 1st month following onset of clinical symptoms. At 4 weeks, a well-defined band of hypointense signal appears on T2-weighted images in the topographic distribution of the corticospinal tract. After 10-14 weeks, the signal becomes permanently hyperintense. Over several years, accompanying ipsilateral brain stem shrinkage occurs. The dark signal intensity observed on T2-weighted images between 4 and 14 weeks is believed to result primarily from transitory increased lipid-protein ratio.  相似文献   
104.
In a prospective study of 65 patients with bile duct obstruction, various radiologic modalities were compared for their capability to demonstrate the level and cause of obstruction and to indicate accurately tumor resectability. Ultrasound (US) was performed in 65 patients, computed tomography (CT) in 51, direct cholangiography (DC) in 57, and angiography in 35. The level of obstruction was correctly indicated by US in 95% of patients and by CT in 90%, and the cause was correctly indicated by US in 88%, by CT in 63%, and by DC in 89%. In predicting tumor resectability, US was correct in 71% of patients, compared with 42% for CT, 58% for DC, and 25% for angiography. US therefore appears to be the single most useful modality in the evaluation bile duct obstruction.  相似文献   
105.
A volumetric approach to quantitative single-energy computed tomography (CT) of the spine for trabecular bone evaluation was compared with the accepted single-section method in 32 thoracic and lumbar vertebral bodies from six cadaveric specimens. Both 5-mm and 10-mm contiguous section sequences afforded greater sample volumes, mean mineral equivalent values, and precision than did the single midplane section technique. These findings can be explained by inhomogeneous trabecular distribution, differential bone resorption rates for various cancellous regions, and nonuniform deposition of marrow fat. Scoliosis may modify the net influence of these factors owing to altered biomechanical forces. Although the single-section method affords optimal sensitivity to early or subtle alterations in vertebral trabecular bone density, it may misrepresent the status of the total cancellous volume. Because three-dimensional histographic analysis includes structurally important peripheral trabeculae in determinations of mean mineral equivalent values, it may more accurately reflect vertebral body strength and risk of compression fracture.  相似文献   
106.
In patient with a chronic post-tuberculous bronchopleural cutaneous fistula (BPCF), minute ventilation, dead space, flow rates, arterial blood gas tensions, and oxygen consumption were measured during mouth breathing and after 30 min of steady-state breathing solely through the BPCF. Despite a 390-ml (18%) decrease in dead space when breathing took place through the BPCF, there were no significant changes in minute ventilation or respiratory rate. BPCF breathing was also associated with an increase in airways resistance as reflected by a 300-ml (35%) decrease in the FEV1 and a 16% decrease in the FEV1/FVC ratio. The increased resistance resulted in a 20 ml/min (18%) increase in oxygen consumption. Arterial blood gas tensions remained constant. We conclude that although ventilatory efficiency was not improved, this patient was able to satisfy his total minute ventilatory requirements, for the 30-min period, solely through BPCF breathing.  相似文献   
107.
Ho  CP; Kim  RW; Schaffler  MB; Sartoris  DJ 《Radiology》1990,176(1):171-173
Dual-energy radiographic absorptiometry (DRA) was used to measure the bone mineral content and area density of lumbar vertebrae (L2-L3) in 11 cadavers. These data were subsequently compared with measured ash content and density. Excellent correlation was obtained between bone mineral content measured with DRA and ash weight (r = .963, P less than .0001). The accuracy error in determining mineral content in lumbar vertebrae with DRA was about 9%. In addition, strong correlation was observed between bone mineral density measured with DRA and ash density (r = .881, P less than .0001).  相似文献   
108.
目的:观察蜂胶乔松素对脂多糖诱导人脐静脉内皮细胞的影响,探讨其对人脐静脉内皮细胞可能的保护作用。方法:实验于2006-03/10在泰山医学院生命科学研究所(省重点实验室)完成。①实验材料:取出生1h内新生儿脐带,患者知情同意。②实验分组及方法:培养人脐静脉内皮细胞,建立脂多糖损伤模型(以10mg/L的脂多糖培养液培养细胞12h),实验分为空白对照组(加等量D-Hank’s液)、脂多糖组(10mg/L)、乔松素组(加10mg/L脂多糖预孵育12h后,按50,100,200mg/L分别加入乔松素),各组设8个复孔,共同孵育24h。③实验评估:光镜下观察细胞形态,MTT法观察乔松素对人脐静脉内皮细胞活性的影响,ELISA方法检测培养上清中血管假血友病因子的含量,TUNEL检测细胞凋亡率。结果:①细胞形态:空白对照组细胞紧密贴壁,呈铺路石状生长。脂多糖组可见多数细胞呈圆形;乔松素组见上述细胞较脂多糖组明显减少。②乔松素对人脐静脉内皮细胞活性、凋亡及血管假血友病因子含量的影响:与对照组比较,脂多糖组能明显诱导人脐静脉内皮细胞的凋亡(P<0.01),不同浓度乔松素组可改善内皮细胞形态,组织活性明显升高(P<0.05),同时抑制内皮细胞血管假血友病因子的释放(P<0.05),使脂多糖诱导的人脐静脉内皮细胞凋亡细胞数明显减少(P<0.05)。结论:乔松素能增强人脐静脉内皮细胞活性,抑制脂多糖诱导人脐静脉内皮细胞的凋亡,从而发挥可能的内皮细胞保护功能。  相似文献   
109.
Non-invasive trigeminal evoked potentials: normative aging data   总被引:1,自引:0,他引:1  
A mild electric shock applied to the lower lip was used to elicit reliable evoked potentials from the trigeminal nerve in 50 normal adults who ranged in age from 20 to 69 years. The waveforms were morphologically similar to those observed with invasive procedures. No substantial effects for subject age, side of stimulation, or recording electrode were obtained for any of the individual trigeminal evoked potential amplitudes or latencies. Female subjects tended to have somewhat larger amplitudes and shorter latencies than male subjects. The results suggest that non-invasive procedures produce reliable evoked potential measures of trigeminal nerve function for patients of all ages.  相似文献   
110.
自体造血干细胞的体外净化   总被引:1,自引:0,他引:1  
目的:综合分析自体造血干细胞体外净化的方法。资料来源:应用计算机检索Medline 1991-01/2003-12有关自体造血干细胞体外净化方法的文章,检索词“purging,HSCT”,并限定文章语言种类为English。同时计算机检索CNKI数据库1991-01/2003-12有关自体造血干细胞体外净化方法的文章,检索词“体外净化,PUVA”,并限定文章语言种类为中文。资料选择:对相关资料进行整理,选取同一领域、不同方面的文献,以近期发表或权威杂志的文章优先。资料提炼:共检索到42篇有关自体造血干细胞体外净化方法的文献,其中24篇文章符合要求。排除18篇,其中15篇系重复同一研究,3篇为Meta分析。资料综合:自体造血干细胞的体外净化方法很多,如物理方法、生物学方法、药物方法、免疫净化、基因净化等。每种净化方法都有其各自的优势和不足,如淋巴系统疾病可以采用免疫净化;慢性粒细胞白血病患者可考虑反义技术;大多数患者则均可以考虑药物净化的方法。结论:针对不同的疾病,可以选择不同的净化方法,还可以将几种净化方法联合起来,其效果和方法的改进也在不断的研究探索中。  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