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   517548篇
  免费   47565篇
  国内免费   34547篇
耳鼻咽喉   4206篇
儿科学   6378篇
妇产科学   6185篇
基础医学   57834篇
口腔科学   8793篇
临床医学   71125篇
内科学   70673篇
皮肤病学   5893篇
神经病学   25383篇
特种医学   18844篇
外国民族医学   291篇
外科学   47797篇
综合类   93597篇
现状与发展   111篇
一般理论   51篇
预防医学   37372篇
眼科学   14310篇
药学   56305篇
  576篇
中国医学   33280篇
肿瘤学   40656篇
  2024年   1818篇
  2023年   7404篇
  2022年   19671篇
  2021年   25139篇
  2020年   19509篇
  2019年   16141篇
  2018年   16868篇
  2017年   16208篇
  2016年   14909篇
  2015年   23117篇
  2014年   28803篇
  2013年   26609篇
  2012年   39334篇
  2011年   43711篇
  2010年   29350篇
  2009年   23683篇
  2008年   29414篇
  2007年   28913篇
  2006年   27670篇
  2005年   26436篇
  2004年   17377篇
  2003年   16554篇
  2002年   13605篇
  2001年   11682篇
  2000年   11558篇
  1999年   11674篇
  1998年   7212篇
  1997年   7049篇
  1996年   5425篇
  1995年   5163篇
  1994年   4406篇
  1993年   2780篇
  1992年   3555篇
  1991年   3088篇
  1990年   2593篇
  1989年   2301篇
  1988年   1978篇
  1987年   1732篇
  1986年   1362篇
  1985年   1035篇
  1984年   540篇
  1983年   425篇
  1982年   224篇
  1981年   279篇
  1980年   190篇
  1979年   254篇
  1978年   125篇
  1977年   103篇
  1976年   76篇
  1974年   85篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
133.
BACKGROUND AND PURPOSE: There are limited data on the pattern of cancer distribution among adolescents in Taiwan. This study evaluated the characteristics of these rare cancers in a medical center. METHODS: Analyses of the characteristics of malignant neoplasms for patients aged 14 to 17 years at diagnosis were performed for all cases recorded in the tumor registry of Chang Gung Memorial Hospital (CGMH) at Linkou for the period 1995 to 2001. All eligible tumors were categorized in 1 of 12 diagnostic groups according to the scheme of the International Classification of Childhood Cancer (ICCC). Relative frequencies, age, and gender variations and the characteristics of tumor types were analyzed. RESULTS: Cancer was diagnosed in 320 adolescents during the study period. The male/female ratio was 1.17. Leukemia was the leading diagnostic group. The frequency of carcinomas increased with age and was highest among 17-year-olds. In this age group, non-rhabdomyosarcoma soft tissue sarcoma/primitive neuroectodermal tumor (non-RMS STS/PNET), thyroid carcinoma (CA) and ovarian germ cell tumor (GCT) were the 3 most common solid tumors; the embryonal malignancies were rare. Tumors with the greatest male predominance were intracranial GCT (91%), nasopharyngeal CA (87.5%), osteosarcoma (84.6%), and colorectal CA (75%). Tumors with the greatest female predominance were thyroid CA (78.3%), gonadal GCT (75%), and non-RMS/PNET (56.5%). Hepatocellular CA comprised 9.4% of all carcinomas. CONCLUSIONS: The relative frequency and the distribution of histology subtypes among adolescents were between those of childhood and adult cancers. There were marked variations in tumor occurrence between genders and among different ages.  相似文献   
134.
BACKGROUND: Deposition of proteins on surfaces of medical devices has been recognized to putatively relate to the process of regulation of biomaterial-associated complications by attachment of fibrin clots, eukaryotic cells, and microbes. The molecules adsorb to a varying extent, depending not only on the physicochemical properties of the biomaterial, but also on the composition of the host fluid. OBJECTIVE: Adsorption of proteins on catheters exposed both ex vivo and in vitro to dialysate of patients on peritoneal dialysis (PD) was studied. METHODS: Peritoneal dialysis effluent was collected from 5 patients with end-stage renal disease on continuous ambulatory PD. Tenckhoff catheters were obtained from 16 patients. Deposition of proteins on excised Tenckhoff catheters and tubing of different materials exposed to PD effluent in vitro was studied using 125iodine-labeled antibodies. Adhesion of Staphylococcus aureus and Staphylococcus epidermidis strains was quantified on tubing exposed to PD effluent in vitro. RESULTS: The presence of albumin, transferrin, immunoglobulin G, fibrinogen, fibronectin, von Willebrand factor, vitronectin, and thrombospondin was determined at various concentrations in PD effluent. All proteins analyzed were detected on PD catheters removed from patients. The extent of protein deposition on Tenckhoff catheters exposed to PD effluent, in vitro, rapidly reached a plateau and remained constant, as it did on polyvinyl chloride and polyethylene tubing. Adhesion of staphylococci was enhanced on Tenckhoff catheters exposed to PD effluent compared to unused PD solution. CONCLUSIONS: The data identify surface exposed proteins that may serve as adhesion sites for microbes on peritoneal catheters indwelled in patients undergoing PD.  相似文献   
135.
136.
Preparation and characterization of porous hollow silica nanoparticles (PHSN) for controlled release applications were investigated. Through orthogonally designed experiments, the optimal synthesis conditions for the preparation of PHSN were obtained and the produced PHSN were characterized by BET, SEM, TEM and IR. Scanning and transmission electron microscopy images revealed their hollow shell-core structure and also demonstrated that the size and shape of PHSN are determined by the templating CaCO3 nanoparticles. The produced PHSN were applied as a carrier to study the controlled release behaviors of Brilliant Blue F (BB), which was used as a model drug. Being loaded into the inner core and on the surfaces of the nanoparticles, BB was released slowly into a bulk solution for about 1140 min as compared to only 10 min for the normal SiO2 nanoparticles, thus exhibited a typical sustained release pattern without any burst effect. In addition, higher BET of the carriers, lower pH value and lower temperature prolonged BB release from PHSN, while stirring speed showed little influence on the release behavior. It showed that PHSN have a promising future in controlled drug delivery applications.  相似文献   
137.
李红  强大平 《基层医学论坛》2006,10(21):975-977
本文采用实验研究方法,通过对大鼠运动后红细胞数量,Hb浓度及体重等一般情况的检测,拟对其施加不同负荷的训练,观察训练后大鼠红细胞膜流动性及红细胞膜脂质成分的变化,进一步讨论运动后红细胞功能及机体机能所发生的变化。实验结果表明,小负荷的运动训练通过改善RBCM脂质组成,增加p/c比值、增强其抗氧化能力等增加RBCM流动性,使红细胞的变形能力增加,有利于其运氧功能的发挥。大负荷训练后RBCM流动性下降,提示不同负荷的运动训练会引起机体产生不同的变化,进而导致机体运动水平上的差异,整体携氧能力下降。  相似文献   
138.
OBJECTIVES: To examine the effect of individual patient factors (age, parity, body mass index, menstrual cycle, menopause, hormone replacement therapy, bladder neck position and urethral mobility) on the appearance of Doppler flow in urethral vessels, to investigate the association between the Doppler flow parameters and intrinsic urethral function, storage and voiding, and to explore differences in the urethral vasculature between subjects with and without urodynamic stress incontinence (USI). METHODS: Over a 4-year period we prospectively performed imaging studies in 355 women, including 244 who denied any lower urinary tract symptoms within the previous 3 months (Group A) and 111 who had had lower urinary tract symptoms (Group B). Studies included morphologic assessment and Doppler flow investigation of the lower urinary tract. Vascular flow velocity and vessel density in the urethral vasculature were measured. For women in Group B, multichannel urodynamic studies were also performed. RESULTS: The urethral vasculature has five main branches of vessels. Their appearance was not affected by the menstrual cycle or menopause except for those of the anterior vaginal vessel and anterior branch of the middle urethral vessel. Other than that of the posterior urethral vessel, in which there was a correlation with parity, the resistance index (RI) was not affected by individual patient factors. However, there was a correlation between the vascular index (VI) and individual factors such as age (r = -0.336, P = 0.002), body mass index (r = -0.287, P = 0.028), menopause (r = -0.402, P < 0.001), and hormone replacement therapy (r = 0.392, P = 0.027). Only the VI and RI of the posterior urethral vessel correlated significantly with the urethral pressure profile. In subjects with lower urinary tract symptoms, the appearance of the urethral vasculature on power Doppler imaging and the corresponding RI and VI values were not correlated with objective evidence of USI. CONCLUSION: Patient factors may affect specific Doppler flow parameters of the urethral vasculature, which are related to intrinsic resting urethral closure. There is no difference in the appearance of the urethral vasculature in subjects with or without USI.  相似文献   
139.
140.
王涛  李秋军 《护理研究》2006,20(28):2567-2568
早期下床活动的必要性已得到大家认可,但术后早期病人常常较虚弱,且下床活动时会引发一些不适,病人也会有一些担心和顾虑,这在一定程度上会影响病人下床活动的积极性。颈椎手术本身有其特殊性,术后对颈部的稳定要求较高,因此此类病人活动有其特点。本研究以颈椎术后已下床活动的病人为研究对象,通过问卷调查,了解颈椎手术后病人首次下床的感受和相关需求,为进一步提高颈椎术后护理质量提供依据。1资料和方法1.1对象采用方便取样,选取2005年4月—2005年6月在某三甲医院因颈椎病入院、术后已下床活动的病人75例。其中男54例,女21例;年龄28岁~7…  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