首页 | 官方网站   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   218851篇
  免费   5444篇
  国内免费   519篇
医药卫生   224814篇
  2021年   759篇
  2019年   721篇
  2018年   4316篇
  2017年   4495篇
  2016年   3810篇
  2015年   5415篇
  2014年   5030篇
  2013年   4569篇
  2012年   11493篇
  2011年   6482篇
  2010年   3098篇
  2009年   4597篇
  2008年   3539篇
  2007年   4345篇
  2006年   4555篇
  2005年   12652篇
  2004年   13998篇
  2003年   9643篇
  2002年   4801篇
  2001年   4804篇
  2000年   2224篇
  1999年   6205篇
  1992年   7011篇
  1991年   7212篇
  1990年   7443篇
  1989年   7043篇
  1988年   6555篇
  1987年   6319篇
  1986年   6033篇
  1985年   5333篇
  1984年   3644篇
  1983年   2966篇
  1982年   1053篇
  1981年   814篇
  1980年   878篇
  1979年   3887篇
  1978年   2396篇
  1977年   1836篇
  1976年   1599篇
  1975年   2508篇
  1974年   3149篇
  1973年   2778篇
  1972年   2791篇
  1971年   2764篇
  1970年   2578篇
  1969年   2493篇
  1968年   2257篇
  1967年   2193篇
  1966年   1916篇
  1965年   1144篇
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
1.
The aim of this safety study in mice was to determine in vivo toxicity and biodistribution potential of a single and multiple doses of L-glutamic acid-g-p(HEMA) polymeric nanoparticles as a drug delivery system. The single dose did not cause any lethal effect, and its acute oral LD50 was >2.000 mg/kg body weight (bw). Multiple doses (25, 50, or 100 mg/kg bw) given over 28 days resulted in no significant differences in body and relative organ weights compared to control. These results are supported by biochemical and histological findings. Moreover, nanoparticle exposure did not result in statistically significant differences in micronucleus counts in bone marrow cells compared to control. Nanoparticle distribution was time-dependent, and they reached the organs and even bone marrow by hour 6, as established by ex vivo imaging with the IVIS® spectrum imaging system. In conclusion, L-glutamic acid-g-p(HEMA) polymeric nanoparticles appear biocompatible and have a potential use as a drug delivery system.KEY WORDS: biocompatibility, blood biochemistry, genotoxicity, histology, in vivo toxicity, micronucleus test, polymers  相似文献   
2.
3.
4.
5.
6.
Journal of Public Health - Media as a source of information can shape public opinion regarding the COVID-19 response. Identifying how and where people seek information during the COVID-19 outbreak...  相似文献   
7.
Background and aimsDeterioration of anthropometric and lung function parameters was shown to precede the onset of cystic fibrosis-related diabetes (CFRD) in adults. In children, studies have been conducted in small cohorts with relatively short observation period. Study objectives were to document the longitudinal trends of anthropometric, pulmonary, nutritional and metabolic parameters from cystic fibrosis (CF) diagnosis to the ascertainment of abnormal glucose tolerance and identify parameters associated with the incidence of such abnormalities in a pediatric CF cohort.Methods and resultsRetrospective cohort study of 281 children with CF. Longitudinal trends of anthropometric, lung function, nutritional and metabolic data were generated from CF diagnosis to the ascertainment of abnormal glucose tolerance defined as the presence of either impaired glucose tolerance (IGT), unconfirmed CFRD or CFRD. Cox models and Kaplan–Meier curves were used to identify factors associated with developing abnormal glucose tolerance.Forty-five percent of cohort had normal glucose tolerance (NGT), 27% IGT, 10% unconfirmed CFRD and 18% CFRD. Children who developed CFRD displayed lower height z-scores from a very early age. Conversely, HbA1c levels began to rise closer to CFRD ascertainment. Height z-scores (HR: 0.45; CI 95% [0.29–0.69]) and HbA1c (HR: 2.43; CI 95% [1.86–3.18]) in years preceding ascertainment were associated with the risk of developing CFRD.ConclusionChildren who developed CFRD display distinctive trends for height z-scores from a very early age, whereas HbA1c appears as a marker of established glucose metabolism derangements.  相似文献   
8.
According to global neuronal workspace (GNW) theory, conscious access relies on long-distance cerebral connectivity to allow a global neuronal ignition coding for conscious content. In patients with schizophrenia and bipolar disorder, both alterations in cerebral connectivity and an increased threshold for conscious perception have been reported. The implications of abnormal structural connectivity for disrupted conscious access and the relationship between these two deficits and psychopathology remain unclear. The aim of this study was to determine the extent to which structural connectivity is correlated with consciousness threshold, particularly in psychosis. We used a visual masking paradigm to measure consciousness threshold, and diffusion MRI tractography to assess structural connectivity in 97 humans of either sex with varying degrees of psychosis: healthy control subjects (n = 46), schizophrenia patients (n = 25), and bipolar disorder patients with (n = 17) and without (n = 9) a history of psychosis. Patients with psychosis (schizophrenia and bipolar disorder with psychotic features) had an elevated masking threshold compared with control subjects and bipolar disorder patients without psychotic features. Masking threshold correlated negatively with the mean general fractional anisotropy of white matter tracts exclusively within the GNW network (inferior frontal-occipital fasciculus, cingulum, and corpus callosum). Mediation analysis demonstrated that alterations in long-distance connectivity were associated with an increased masking threshold, which in turn was linked to psychotic symptoms. Our findings support the hypothesis that long-distance structural connectivity within the GNW plays a crucial role in conscious access, and that conscious access may mediate the association between impaired structural connectivity and psychosis.  相似文献   
9.
There have been a number of investigations of the efficacy and safety of etanercept. This study was performed to obtain long-term drug survival data (ie, time to drug discontinuation) for etanercept, and the reasons for its discontinuation. The study population consisted of patients with psoriatic arthritis and psoriasis followed up by our clinic, registered in the Turkish Psoriasis Registry (PSR-TR) and treated with etanercept for at least 4 weeks between January 1, 2005, and January 31, 2020. The efficacy of etanercept was evaluated in terms of the Psoriasis Area and Severity Index (PASI) 75, PASI 90 and PASI 100 response rates at 12, 24, 36, and 48 weeks, and annually thereafter. The behaviors of the patients with respect to the use of etanercept, and the outcomes of those who continued to use it during the COVID-19 pandemic, were also investigated.  相似文献   
10.
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-23

京公网安备 11010802026262号