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   2210篇
  免费   409篇
  国内免费   14篇
耳鼻咽喉   33篇
儿科学   50篇
妇产科学   51篇
基础医学   165篇
口腔科学   16篇
临床医学   607篇
内科学   444篇
皮肤病学   26篇
神经病学   345篇
特种医学   88篇
外科学   333篇
综合类   16篇
预防医学   194篇
眼科学   10篇
药学   94篇
中国医学   5篇
肿瘤学   156篇
  2024年   6篇
  2023年   67篇
  2022年   49篇
  2021年   108篇
  2020年   88篇
  2019年   96篇
  2018年   103篇
  2017年   127篇
  2016年   118篇
  2015年   135篇
  2014年   133篇
  2013年   172篇
  2012年   108篇
  2011年   124篇
  2010年   108篇
  2009年   151篇
  2008年   93篇
  2007年   101篇
  2006年   72篇
  2005年   64篇
  2004年   68篇
  2003年   62篇
  2002年   48篇
  2001年   44篇
  2000年   32篇
  1999年   20篇
  1998年   43篇
  1997年   26篇
  1996年   31篇
  1995年   18篇
  1994年   18篇
  1993年   7篇
  1992年   18篇
  1991年   23篇
  1990年   31篇
  1989年   17篇
  1988年   19篇
  1987年   11篇
  1986年   13篇
  1985年   8篇
  1984年   9篇
  1983年   6篇
  1982年   5篇
  1981年   7篇
  1980年   3篇
  1977年   3篇
  1976年   4篇
  1975年   4篇
  1968年   2篇
  1966年   2篇
排序方式: 共有2633条查询结果,搜索用时 15 毫秒
91.
92.
93.
94.
95.
Background: Decreased muscle strength impedes elders' functional performance in daily activities such as gait. The mechanisms whereby increased strength improves gait are unknown.Methods: A prospective, blinded, randomized trial of moderate intensity strength exercise was conducted and its impact was measured on functional mobility during gait in 132 functionally limited elders. Lower extremity strength was measured, including hip abductor, hip extensor, and knee extensor strength. Of the 132 subjects, 120 subjects (mean age, 75.lyrs) completed 6 months of elastic band resistance training at least 3 times a week or served as no-exercise controls.Results: Subjects increased their lower extremity strength in the exercise and control groups, by 17.6% and 7.3% (p < .01), respectively. Gait stability improved significantly more in the exercise group than in the control group (p < .05). Increases in forward gait velocity were not significantly different between groups. Peak mediolateral velocity and base of support improved in the exercise group, but not in the control group. Change in lower extremity strength correlated significantly but weakly with many of the gait variables.Conclusions: Gait stability, especially mediolateral steadiness, improved in the exercise group but not in the control group. These results show that even moderate strength gains benefit gait performance in elders and thus provide a sound basis for encouraging low-intensity strength training for elders with functional limitations.  相似文献   
96.
97.
In a double-blind, randomized, and placebo-controlled previous trial, the efficacy of Vi-rEPA for typhoid fever in 2- to 5-year-olds was 89.0% for 46 months. Vi-rEPA contained 25 microg of Vi and induced a greater-than-eightfold rise in immunoglobulin G (IgG) anti-Vi in all of the vaccinees tested. In this investigation, we conducted a dosage-immunogenicity study of 5, 12.5, and 25 microg of Vi-rEPA in this age group. Two doses of Vi-rEPA were injected 6 weeks apart. Blood samples were taken before and at 10 weeks (4 weeks after the second injection) and 1 year later. All postimmunization geometric mean (GM) levels were higher than the preimmune levels (P < 0.0001). At 10 weeks, the GM IgG anti-Vi level elicited by 25 microg (102 EU/ml) was higher than those elicited by 12.5 microg (74.7 EU/ml) and 5 microg (43 EU/ml) (P < 0.004): all of the children had > or = 3.52 EU/ml (estimated minimum protective level). One year later, the levels declined about sevenfold (13.3 and 11.3 versus 6.43 EU/ml, P < 0.0001) but remained significantly higher than the preimmune levels (P < 0.0001), and >96% of the children had a greater-than-eightfold rise. This study also confirmed the safety and consistent immunogenicity of the four lots of Vi-rEPA used in this and previous trials.  相似文献   
98.
BACKGROUND/OBJECTIVES: An ineffective cytokine response is thought to be one of the reasons for the failure to suppress hepatitis B virus (HBV) replication and to eliminate the virus. We investigated the serum levels of interleukin (IL)-6, IL-10, IL-12, and interferon (IFN)-gamma in HBV-infected Vietnamese patients to determine whether they were related to the outcome of HBV infection. STUDY DESIGN: Samples from a total of 154 HBV-infected patients with well-characterised clinical profiles and 56 healthy controls were assessed. RESULTS: Serum IL-6 levels, which were inversely correlated with transaminase levels, were highest in patients with liver cirrhosis (LC) and hepatocellular carcinoma (HCC) and lowest in those with either asymptomatic (ASYM), acute or chronic HBV, and thus, represented the best marker of HBV-related clinical progression. Compared with the healthy control group, serum IL-12 was uniformly elevated in all HBV-infected patients apart from those with ASYM infections, implying no impairment of production of this cytokine in HBV-infected individuals. Serum IL-10 and IFN-gamma levels, however, were uniformly low and showed no association with clinical presentation. Cytokine profiles were not influenced by the presence of hepatitis B e antigen (HbeAg). CONCLUSIONS: Serum IL-6 and IL-12 but not IL-10 and IFN-gamma are associated with the clinical presentation in HBV-infected Vietnamese patients.  相似文献   
99.
Data from 10 sites of the NICHD/NIDCD Collaborative Programs of Excellence in Autism were combined to study the distribution of head circumference and relationship to demographic and clinical variables. Three hundred thirty-eight probands with autism-spectrum disorder (ASD) including 208 probands with autism were studied along with 147 parents, 149 siblings, and typically developing controls. ASDs were diagnosed, and head circumference and clinical variables measured in a standardized manner across all sites. All subjects with autism met ADI-R, ADOS-G, DSM-IV, and ICD-10 criteria. The results show the distribution of standardized head circumference in autism is normal in shape, and the mean, variance, and rate of macrocephaly but not microcephaly are increased. Head circumference tends to be large relative to height in autism. No site, gender, age, SES, verbal, or non-verbal IQ effects were present in the autism sample. In addition to autism itself, standardized height and average parental head circumference were the most important factors predicting head circumference in individuals with autism. Mean standardized head circumference and rates of macrocephaly were similar in probands with autism and their parents. Increased head circumference was associated with a higher (more severe) ADI-R social algorithm score. Macrocephaly is associated with delayed onset of language. Although mean head circumference and rates of macrocephaly are increased in autism, a high degree of variability is present, underscoring the complex clinical heterogeneity of the disorder. The wide distribution of head circumference in autism has major implications for genetic, neuroimaging, and other neurobiological research.  相似文献   
100.
Magnetoencephalography (MEG) and electroencephalography provide a high temporal resolution, which allows estimation of the detailed time courses of neuronal activity. However, in real-time analysis of these data two major challenges must be handled: the low signal-to-noise ratio (SNR) and the limited time available for computations. In this work, we present real-time clustered multiple signal classification (RTC-MUSIC) a real-time source localization algorithm, which can handle low SNRs and can reduce the computational effort. It provides correlation information together with sparse source estimation results, which can, e.g., be used to identify evoked responses with high sensitivity. RTC-MUSIC clusters the forward solution based on an anatomical brain atlas and optimizes the scanning process inherent to MUSIC approaches. We evaluated RTC-MUSIC by analyzing MEG auditory and somatosensory data. The results demonstrate that the proposed method localizes sources reliably. For the auditory experiment the most dominant correlated source pair was located bilaterally in the superior temporal gyri. The highest activation in the somatosensory experiment was found in the contra-lateral primary somatosensory cortex.  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