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   29978篇
  免费   2960篇
  国内免费   2210篇
耳鼻咽喉   335篇
儿科学   357篇
妇产科学   356篇
基础医学   3632篇
口腔科学   550篇
临床医学   4020篇
内科学   4354篇
皮肤病学   366篇
神经病学   1569篇
特种医学   1114篇
外国民族医学   16篇
外科学   2749篇
综合类   5089篇
现状与发展   8篇
一般理论   6篇
预防医学   2184篇
眼科学   877篇
药学   3283篇
  19篇
中国医学   1801篇
肿瘤学   2463篇
  2024年   67篇
  2023年   433篇
  2022年   1062篇
  2021年   1561篇
  2020年   1202篇
  2019年   1061篇
  2018年   1103篇
  2017年   1115篇
  2016年   1008篇
  2015年   1386篇
  2014年   1801篇
  2013年   1661篇
  2012年   2386篇
  2011年   2523篇
  2010年   1565篇
  2009年   1247篇
  2008年   1649篇
  2007年   1602篇
  2006年   1489篇
  2005年   1476篇
  2004年   1034篇
  2003年   984篇
  2002年   839篇
  2001年   680篇
  2000年   602篇
  1999年   614篇
  1998年   413篇
  1997年   364篇
  1996年   273篇
  1995年   286篇
  1994年   252篇
  1993年   178篇
  1992年   203篇
  1991年   189篇
  1990年   138篇
  1989年   141篇
  1988年   131篇
  1987年   99篇
  1986年   80篇
  1985年   61篇
  1984年   28篇
  1983年   42篇
  1981年   17篇
  1980年   13篇
  1979年   16篇
  1978年   7篇
  1977年   8篇
  1976年   7篇
  1974年   7篇
  1973年   9篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
972.

Background

Streptococcus pneumoniae is a leading cause of invasive infection in young children causing morbidity and mortality. Active surveillance systems of invasive pneumococcal disease (IPD) are recommended worldwide. The aim of this study was to estimate the current incidence of IPD and to describe the serotype distribution and the antimocrobial susceptibility of S. pneumoniae isolates in children aged less than 5?years residing in North-West Lombardy, Italy.

Methods

A twelve-month prospective active surveillance system recruited all children aged less than 5?years admitted for suspicion of IPD at emergency room of ten hospitals located in the monitored area. Blood samples were taken in all participants for confirmation of IPD based on isolation of S. pneumoniae from blood. Pneumococcal meningitis and sepsis were additionally confirmed by cerebrospinal fluid analysis. Serotyping and antimicrobial susceptibility testing were performed on isolates from blood.

Results

A total of 15 confirmed cases of IPD were detected among 135 recruited children, including pneumonia (n?=?8), bacteremia (n?=?4), sepsis (n?=?2) and meningitis (n?=?1). The annual IPD incidence rate was 50.0/100,000 (95%CI, 30.5-82.5/100,000). Incidence was 58.3/100,000 (28.8-120.1/100,000) among children aged less than 2?years and 44.4/100,000 (22.9-87.5/100,000) among children aged 2?C4?years. Thirteen isolates were typified. The most common serotype was 19A (23.1%) that together with serotypes 1, 7F and 19F accounted for 69.2% of typified isolates. Serotypes 14, 23F, 12B and 15C were also identified. The 7- and 13-valent pneumococcal conjugate vaccines covered respectively 30.8% and 84.6% of typified IPD cases. One isolate (serotype 15C) was penicillin-resistant and caused meningitis.

Conclusions

The inclusion of the 13-valent pneumococcal conjugate vaccine in immunization programs of young children might be considered to reduce incidence and morbidity of invasive pneumococcal disease in this surveilled population.  相似文献   
973.
Chen XS  Yin YP 《The Lancet infectious diseases》2012,12(4):269; author reply 270-269; author reply 271
  相似文献   
974.
975.
目的 探讨糖尿病性黄斑水肿(diabetic macular edema,DME)与肾功能受损及其严重程度的相关性。设计 回顾性病例系列。研究对象 2016年1月至2020年12月北京老年医院内分泌科住院患者中在眼科会诊的2型糖尿病患者1023例。方法 通过调阅病历获得研究对象的年龄、收缩压、舒张压、血肌酐、空腹静脉血血糖、糖化血红蛋白以及尿微量白蛋白。应用CKD-EPI scr(2009)公式计算估算肾小球滤过率(estimated glomerular filtration rate,eGFR))。eGFR≥90 ml/min/1.73m2为肾功能正常,60~90 ml/min/1.73m2为肾功能受损,﹤60 ml/min/1.73m2为肾功能不全。调取患者立体彩色眼底像、相干光断层扫描图像。根据美国“糖尿病视网膜病变早期治疗小组”标准诊断DME。比较不同eGFR分级组患者DME的发生率,并采用Logistics回归分析黄斑水肿与肾功能受损程度的相关性。主要指标 DME的发生率。结果 120例患者被诊断为DME。DME的发生与eGFR分级相关,肾功能正常、肾功能受损和肾功能不全患者中,DME患者的比例分别为8.30%、20.51%和24.63%,显示随肾功能异常者DME患者比例显著增加(χ2=34.252,P=0.000)。Logistic回归显示肾功能受损、肾功能不全者发生DME的风险分别是肾功能正常者的1.604倍及2.573倍。结论 DME的发生与肾功能受损及其严重程度相关。(眼科,2021, 30: 232-235)  相似文献   
976.
977.
978.
目的:比较强脉冲光(IPL)联合睑板腺按摩和单纯睑板腺按摩对睑板腺功能障碍(MGD)的短期疗效差异。方法:选取2019-10/2020-01在四川大学华西医院眼科就诊的MGD患者共40例80眼,随机分为试验组和对照组,两组均接受3次治疗,每次治疗中试验组双眼接受IPL联合睑板腺按摩,对照组双眼接受单纯睑板腺按摩,治疗时间间隔为2wk,整个试验期间两组均双眼应用玻璃酸钠每天4次,在每次治疗之前及最后一次治疗2wk后进行指标评估,从而评估IPL联合睑板腺按摩的短期疗效。结果:治疗后两组OSDI、SPEED评分均降低(P<0.05),两组间无差异(P>0.05)。两组睑板腺功能评估(MGE)、泪膜脂质层厚度(LLT)均升高,对照组升高较试验组慢,且第二、三次治疗后试验组MGE高于对照组(P<0.05)。两组泪膜破裂时间(BUT)均升高。两组角膜染色均下降,对照组下降较试验组慢,但两组间无差异(P>0.05)。两组视觉质量持续改善,但对照组改善较试验组慢,两组间无差异(P>0.05)。两组泪液分泌、不完全眨眼比例、睑板腺缺失率无明显变化(P>0.05)。所有受试者未出现皮肤、视力损害、眼压改变、眼前节炎症等并发症。结论:IPL联合睑板腺按摩与单纯睑板腺按摩对MGD均安全有效。IPL见效更快,效果可能有累积效应,在达到一定治疗次数后疗效更好。  相似文献   
979.
Understanding the effects of natural solid particles on the phototransformation of pharmaceuticals in aqueous environments is very important, but studies on this are still limited. In this study, natural sands were selected as a solid particle model due to their wide distribution in surface waters during the rainy season, and the phototransformation of diphenhydramine (DP) in the presence of the sands was investigated. The kinetic studies showed that the natural sands exhibited significant photocatalytic activity for the DP photodegradation, and the activity varied depending on their sources. Scavenging experiments and electron paramagnetic resonance analysis demonstrated that O2˙ and ˙OH were produced in the irradiated natural sand systems, and O2˙ played a more important role than ˙OH in the photodegradation of DP. The results obtained from H2O2 treatment and deoxygenation experiments verified that the generation of radicals was mainly attributed to the low content of natural organic matter (NOM) in the sands. The possible reaction mechanism was that the NOM in the sands was excited and became triplet-state NOM after irradiation, and then induced the generation of free radicals through an electron transfer mechanism, resulting in DP oxidation. This work indicated that natural sand particles were a key factor affecting the phototransformation of drugs, and should be considered in evaluating their fate in natural waters.

Natural sand particles induced the generation of free radicals under simulated solar irradiation, resulting in the enhanced photodegradation of diphenhydramine.  相似文献   
980.
Complex space environments, including microgravity and radiation, affect the body''s central nervous system, endocrine system, circulatory system, and reproductive system. Radiation-induced aberration in the neuronal integrity and cognitive functions are particularly well known. Moreover, ionizing radiation is a likely contributor to alterations in the microbiome. However, there is a lacuna between radiation-induced memory impairment and gut microbiota. The present study was aimed at investigating the effects of simulated space-type radiation on learning and memory ability and gut microbiota in mice. Adult mice were irradiated by 60Co-γ rays at 4 Gy to simulate spatial radiation; behavioral experiments, pathological experiments, and transmission electron microscopy all showed that radiation impaired learning and memory ability and hippocampal neurons in mice, which was similar to the cognitive impairment in neurodegenerative diseases. In addition, we observed that radiation destroyed the colonic structure of mice, decreased the expression of tight junction proteins, and increased inflammation levels, which might lead to dysregulation of the intestinal microbiota. We found a correlation between the brain and colon in the changes in neurotransmitters associated with learning and memory. The 16S rRNA results showed that the bacteria associated with these neurotransmitters were also changed at the genus level and were significantly correlated. These results indicate that radiation-induced memory and cognitive impairment can be linked to gut microbiota through neurotransmitters.

Exposure to 60Co-γ ray impacts learning and memory ability as well as the cell morphology and neurotransmitters in hippocampus, even disrupts the bacterial community in colon.  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