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   1609篇
  免费   100篇
  国内免费   7篇
耳鼻咽喉   25篇
儿科学   41篇
妇产科学   66篇
基础医学   249篇
口腔科学   47篇
临床医学   136篇
内科学   381篇
皮肤病学   76篇
神经病学   119篇
特种医学   22篇
外科学   127篇
综合类   4篇
一般理论   1篇
预防医学   188篇
眼科学   16篇
药学   133篇
中国医学   13篇
肿瘤学   72篇
  2024年   1篇
  2023年   21篇
  2022年   15篇
  2021年   88篇
  2020年   45篇
  2019年   61篇
  2018年   76篇
  2017年   48篇
  2016年   42篇
  2015年   50篇
  2014年   71篇
  2013年   89篇
  2012年   132篇
  2011年   128篇
  2010年   68篇
  2009年   63篇
  2008年   86篇
  2007年   116篇
  2006年   92篇
  2005年   98篇
  2004年   105篇
  2003年   82篇
  2002年   60篇
  2001年   6篇
  2000年   12篇
  1999年   9篇
  1998年   8篇
  1997年   6篇
  1996年   7篇
  1995年   11篇
  1994年   3篇
  1993年   4篇
  1992年   4篇
  1991年   2篇
  1990年   1篇
  1989年   3篇
  1988年   1篇
  1985年   1篇
  1978年   1篇
排序方式: 共有1716条查询结果,搜索用时 16 毫秒
71.
BackgroundInformation on the characteristics of patients with nosocomial influenza and associated complications is scarce. This study compared epidemiological and clinical characteristics of patients admitted with hospital‐acquired influenza (HAI) to those with community‐acquired influenza (CAI) and analyzed risk factors associated with complications.MethodsThis retrospective, observational study included all adult patients with confirmed influenza virus infection admitted to Son Espases University Hospital during the influenza season in Spain (October to May) from 2012‐2013 to 2015‐2016. Symptom onset before admission was included as CAI, and 2 days after admission or within 48 hours after previous discharge were considered as HAI.ResultsOverall, 666 patients with laboratory‐confirmed influenza were included; 590 (88.6%) and 76 (11.4%) had CAI and HAI, respectively. Baseline characteristics and vaccination rates were similar in both groups. Patients with HAI had significantly fewer symptoms, less radiological alterations, and earlier microbiological diagnosis than those with CAI. Eighty‐five (14.4%) and 20 (27.6%) CAI and HAI patients, respectively, experienced at least one complication, including septic shock, admission to the intensive care unit, mechanical ventilation or evolution to death (any one, P = .003). Univariate and multivariate binary logistic regression was performed to assess independent risk factors associated with the occurrence of complications: nosocomial infection, diabetes, oseltamivir treatment, having received no vaccination, microbiological delay, dyspnea, and the state of confusion were the most important significant factors.ConclusionsOur study shows the need to implement microbiological diagnostic measures in the first 48 hours to reduce HAI frequency and associated complications.  相似文献   
72.
73.
Clinical Oral Investigations - Periodontitis is a chronic inflammatory disease characterized by tooth-supporting tissue destruction, which is elicited by the host’s immune response triggered...  相似文献   
74.
The aim of the study was threefold: (a) to test a before-school physical activity intervention (Active-Start) on academic performance, selective attention, and concentration capacity; (b) to test the effect of the Active-Start intervention on anthropometry, body composition, and physical fitness parameters; and (c) whether the physical fitness components are moderators of the effect of the Active-Start program on academic performance, selective attention, and concentration capacity in Chilean children. The Active-Start intervention was a RCT which comprised 170 children (8-10 years old) from three public schools with low socioeconomic status from the city of Santiago (Chile). The exercise intervention was delivered daily, before starting the first school-class (8:00-8:30 am ) for 8 weeks. Changes in academic performance, selective attention and concentration capacity, anthropometric, body composition, and physical fitness parameters were measured. The analyses used were mixed regression models for repeated measures over time. No statistically significant changes in attention and concentration capacity were found. However, significant changes were seen in language (0.63; 95% CI 0.49-0.77) and mathematics (0.49; 95% CI 0.32-0.66) performance (P < .001). Also, improvements were seen in fat mass, fat-free mass, muscular, and cardiorespiratory fitness (all P < .05). The Johnson-Neyman technique revealed a significant relationship between the effect of intervention and attention and concentration when change in cardiorespiratory fitness was above, but not below, 3.05 and 0.70 mL/kg/min, respectively. Implementing before-school physical activity programs such as the Active-Start to enhance the cardiorespiratory fitness may benefit attention capacity and academic success among schoolchildren.  相似文献   
75.
76.
Glucagon like peptide-1 (GLP-1) is an incretin hormone that is in the pipeline for type 2 diabetes mellitus (T2DM) therapy. However, oral administration of GLP-1 is hindered by the harsh conditions of the gastrointestinal tract and poor bioavailability. In this study, three nanosystems composed by three different biomaterials (poly(lactide-co-glycolide) polymer (PLGA), Witepsol E85 lipid (solid lipid nanoparticles, SLN) and porous silicon (PSi) were developed and loaded with GLP-1 to study their permeability in vitro. All the nanoparticles presented a size of approximately 200 nm. The nanoparticles' interaction with the mucus and the intestinal cells were enhanced after coating with chitosan (CS). PSi nanosystems presented the best association efficiency (AE) and loading degree (LD), even though a high AE was also observed for PLGA nanoparticles and SLN. Among all the nanosystems, PLGA and PSi were the only nanoparticles able to sustain the release of GLP-1 in biological fluids when coated with CS. This characteristic was also maintained when the nanosystems were in contact with the intestinal Caco-2 and HT29-MTX cell monolayers. The CS-coated PSi nanoparticles showed the highest GLP-1 permeation across the intestinal in vitro models. In conclusion, PLGA + CS and PSi + CS are promising nanocarriers for the oral delivery of GLP-1.  相似文献   
77.
<正>Drug delivery to the posterior segment of the eye,especially the retina,faces the unique challenges of various anatomical and physiological barriers.Invasive intravitreal injection is currently the mainstream clinical approach to posterior eye diseases such as age-related macular degeneration,diabetic retinopathy,uveitis,and cytomegalovirus retinitis.Repeated  相似文献   
78.
79.
Patients with sickle cell disease (SCD) have been shown to have impaired visual-motor speed and coordination. Sensorimotor deficits in mice can be investigated by motor coordination tests that require whole body movements such as the rotorod. A sickle transgenic mouse model (S+S-Antilles) that expresses human α, human β S and human β S-Antilles , is homozygous for the mouse β major deletion, and has low plasma arginine was compared to control C57BL/6J mice and S+S-Antilles mice supplemented with 5% arginine on the rotorod. The rotorod consists of a 2.5 cm diameter, grooved rod turning at constant acceleration, requiring postural adjustments on the part of the mice to maintain equilibrium. C57BL mice on Purina ® mouse chow had an average latency to fall of 169±61 s, S+S-Antilles mice on Purina ® mouse chow had an average of 127±56 s ( P <0.005 ). S+S-Antilles mice after 5% arginine supplementation had a mean latency of 180±32 s ( P <0.003 ). Arginine may improve rotorod performance in sickle transgenic mice by increasing NO synthesis thereby improving vasodilatation and blood flow with reversal of ischemia in brain and/or muscle. In conclusion, impaired rotorod performance in sickle transgenic mice presents an opportunity to apply this simple task to provide an efficient method to screen some types of therapeutic regimens for efficacy in SCD.  相似文献   
80.
Widespread in the coastal zones of (sub)tropical regions, mangroves are an essential habitat for many animal species and provide subsistence resources for many human coastal communities. Among remote sensing techniques, synthetic aperture radar is a particularly advantageous method to monitor mangroves: images are not dependent on cloud cover and can provide information from forest understory. This article mapped mangrove forests in the southern coast of São Paulo State (Brazil) using frequency-based contextual classification of incoherent attributes derived from a multi-polarized Phased Array L-Band Synthetic Aperture Radar (PALSAR) image. The use of 10 incoherent attributes and only 3 Synthetic Aperture Radar (SAR) vegetation indices as input for digital classification showed the best accuracies with kappa index values of 0.739 and 0.734, respectively. HH polarization and SAR vegetation indices were the attributes that contributed most to the mangrove mapping procedure. The use of L-Band SAR data was effective for mapping mangrove areas, and therefore it is recommended as a tool for coastal management.  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