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   18042篇
  免费   1267篇
  国内免费   221篇
耳鼻咽喉   341篇
儿科学   301篇
妇产科学   265篇
基础医学   3136篇
口腔科学   262篇
临床医学   1583篇
内科学   3550篇
皮肤病学   770篇
神经病学   1123篇
特种医学   1303篇
外科学   1802篇
综合类   52篇
现状与发展   1篇
一般理论   2篇
预防医学   672篇
眼科学   623篇
药学   1989篇
中国医学   310篇
肿瘤学   1445篇
  2024年   13篇
  2023年   137篇
  2022年   518篇
  2021年   692篇
  2020年   374篇
  2019年   523篇
  2018年   606篇
  2017年   511篇
  2016年   818篇
  2015年   1056篇
  2014年   1242篇
  2013年   1351篇
  2012年   1879篇
  2011年   1706篇
  2010年   1169篇
  2009年   897篇
  2008年   1126篇
  2007年   1018篇
  2006年   857篇
  2005年   769篇
  2004年   601篇
  2003年   494篇
  2002年   417篇
  2001年   116篇
  2000年   109篇
  1999年   74篇
  1998年   61篇
  1997年   51篇
  1996年   39篇
  1995年   28篇
  1994年   30篇
  1993年   22篇
  1992年   25篇
  1991年   22篇
  1990年   17篇
  1989年   24篇
  1988年   19篇
  1987年   18篇
  1986年   18篇
  1985年   17篇
  1984年   9篇
  1983年   8篇
  1981年   6篇
  1979年   6篇
  1978年   4篇
  1975年   4篇
  1974年   3篇
  1971年   4篇
  1962年   5篇
  1961年   4篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
53.
OBJECTIVES: To estimate the combined screening performance of first and early second trimester prenatal serum markers for Down syndrome, in screening for the development of preeclampsia, and analyze the correlation among marker levels, week of onset, and severity of the disease. METHODS: A retrospective cohort study was carried out on 32 women with preeclampsia and 3044 controls. Serum samples from these pregnancies were assayed for pregnancy-associated plasma protein-A (PAPP-A), alpha-fetoprotein (AFP), unconjugated estriol (uE3), human chorionic gonadotrophin (hCG), and inhibin-A. A likelihood ratio and the odds of being affected given a positive result (OAPR) of various combinations of markers were calculated and receiver operating characteristic (ROC) curves analysis was performed. RESULTS: In the pregnancies that subsequently developed preeclampsia, first trimester PAPP-A concentration was significantly lower and concentrations of early second trimester inhibin-A and hCG significantly elevated. Levels of early second trimester uE3 and AFP were not significantly altered. We also found that inhibin-A correlates with both onset of the disease and the severity. CONCLUSION: Down syndrome biochemical markers levels are altered in those patients who subsequently developed preeclampsia and may be a useful screening test for preeclampsia. Inhibin-A is the most predictive marker and correlates with the severity of subsequent preeclampsia and inversely with the week of occurrence of preeclampsia.  相似文献   
54.
55.
56.
OBJECTIVES: The purpose of our study is to provide reference values for the great vessels obtained from images of the three-vessel view of the fetal heart, with an emphasis on the size discrepancy of the great vessels. METHODS: From February 2003 to May 2003, the main pulmonary artery (MPA), ascending aorta (AA), and SVC were measured in well-dated, nonanomalous fetuses scanned at 14-38 weeks of gestation. RESULTS: The size of each great vessel had a significant positive relationship with advance in gestation (P < 0.001); MPA (mm) = -2.76 + 0.34 x GA, ascending aorta (AA) (mm) = -1.73 + 0.26 x GA - 1.18E - 05 x GA(3), and SVC (mm) = 0.33 + 0.01 x GA(2) - 4.12E - 05 x GA(3). The AA/MPA ratio was significantly decreased with advance in gestation, while the SVC/AA ratio was significantly increased; AA/MPA ratio = -1.24 - 0.03 x GA + 3.88E - 04 x GA(2); P < 0.001, SVC/AA ratio = 0.63 - 5.43E - 03 x GA + 1.96E - 04 x GA(2); P < 0.001. CONCLUSION: On the three-vessel view of the fetal heart, the interpretation of the size discrepancy of the great vessels needs to be adjusted according to fetal growth.  相似文献   
57.
BackgroundParticulate matter (PM) is an air pollutant that can impair the human skin. Antioxidants have been tested to improve PM-induced skin inflammation.ObjectiveIn this study, we investigated the effects of dieckol on PM-induced inflammation on cultured human sebocytes, outer root sheath (ORS) cells, and mice pretreated with Cutibacterium acnes.MethodsWe cultured and treated the sebocytes and ORS cells with 5 µM of dieckol and 100 µg/ml of PM10 for 24 h. The C. acnes-pretreated mice received 5 µM of dieckol and 100 µg/ml of PM10. We measured cell viability using MTT assay. Real-time PCR and measurement of reactive oxygen species (ROS) and sebum production analyzed the effects.ResultsDieckol inhibited the upregulation of the gene expression of the inflammatory cytokines, matrix metalloproteinase (MMP), aryl hydrocarbon receptor, and nuclear factor kappa-light-chain-enhancer of activated B cells by PM10 in the cultured sebocytes and ORS cells and inhibited an increase in ROS production by PM10 in the cultured sebocytes. In addition, dieckol decreased the inflammatory cytokines, MMP, and sebum production in C. acnes-pretreated mice.ConclusionDieckol effectively reduced the expression of inflammatory biomarkers and the production of sebum in cultured sebocytes, ORS cells, and C. acnes-pretreated mice.  相似文献   
58.
59.
BackgroundHospital visitation has become challenging during the coronavirus disease 2019 pandemic because of quarantine measures and fear of infection. Consequently, newly diagnosed patients may present with more severe diseases during the pandemic. The present study analyzed the differences in the initial clinical presentations of newly diagnosed patients with type 1 diabetes (T1D) and type 2 diabetes (T2D), comparing pre-pandemic and pandemic periods.MethodsNewly diagnosed patients with T1D or T2D and aged < 18 years during 2018–2020 were included in the study. Data were collected retrospectively from four academic centers in Gyeonggi-do, South Korea. Initial clinical data were compared between the pre-pandemic (2018–2019) and pandemic (2020) periods.ResultsIn the pre-pandemic and pandemic periods, 99 patients (41 T1D and 58 T2D patients) and 84 patients (51 T1D and 33 T2D patients) were identified, respectively. During the pandemic, the proportion of diabetic ketoacidosis (DKA) cases increased compared to the pre-pandemic period (21.2% during 2018–2019 vs. 38.1% in 2020; P = 0.012). In the pre-pandemic and pandemic periods, initial pH was 7.32 ± 0.14 and 7.27 ± 0.15, respectively (P = 0.040), and HbA1c values were 11.18 ± 2.46% and 12.42 ± 2.87%, respectively (P = 0.002). During the pandemic, there was an increased risk of DKA in patients with T1D (odds ratio, 2.42; 95% confidence interval, 1.04–5.62; P = 0.040).ConclusionDuring the pandemic, the proportion of DKA in newly diagnosed patients with T1D increased and clinical parameters showed a deteriorating pattern. Increased awareness of pediatric diabetes, especially DKA, could facilitate visit to the hospital for an early diagnosis; thus, reducing the number of DKA cases during the pandemic era.  相似文献   
60.
BackgroundNumerous patients around the globe are dying from coronavirus disease 2019 (COVID-19). While age is a known risk factor, risk analysis in the young generation is lacking. The present study aimed to evaluate the clinical features and mortality risk factors in younger patients (≤ 50 years) with a critical case of COVID-19 in comparison with those among older patients (> 50 years) in Korea.MethodsWe analyzed the data of adult patients only in critical condition (requiring high flow nasal cannula oxygen therapy or higher respiratory support) hospitalized with PCR-confirmed COVID-19 at 11 hospitals in Korea from July 1, 2021 to November 30, 2021 when the delta variant was a dominant strain. Patients’ electronic medical records were reviewed to identify clinical characteristics.ResultsDuring the study period, 448 patients were enrolled. One hundred and forty-two were aged 50 years or younger (the younger group), while 306 were above 50 years of age (the older group). The most common pre-existing conditions in the younger group were diabetes mellitus and hypertension, and 69.7% of the patients had a body mass index (BMI) > 25 kg/m2. Of 142 younger patients, 31 of 142 patients (21.8%, 19 women) did not have these pre-existing conditions. The overall case fatality rate among severity cases was 21.0%, and it differed according to age: 5.6% (n = 8/142) in the younger group, 28.1% in the older group, and 38% in the ≥ 65 years group. Age (odds ratio [OR], 7.902; 95% confidence interval [CI], 2.754–18.181), mechanical ventilation therapy (OR, 17.233; 95% CI, 8.439–35.192), highest creatinine > 1.5 mg/dL (OR, 17.631; 95% CI, 8.321–37.357), and combined blood stream infection (OR, 7.092; 95% CI, 1.061–18.181) were identified as independent predictors of mortality in total patients. Similar patterns were observed in age-specific analyses, but most results were statistically insignificant in multivariate analysis due to the low number of deaths in the younger group. The full vaccination rate was very low among study population (13.6%), and only three patients were fully vaccinated, with none of the patients who died having been fully vaccinated in the younger group. Seven of eight patients who died had a pre-existing condition or were obese (BMI > 25 kg/m2), and the one remaining patient died from a secondary infection.ConclusionAbout 22% of the patients in the young critical group did not have an underlying disease or obesity, but the rate of obesity (BMI > 25 kg/m2) was high, with a fatality rate of 5.6%. The full vaccination rate was extremely low compared to the general population of the same age group, showing that non-vaccination has a grave impact on the progression of COVID-19 to a critical condition. The findings of this study highlight the need for measures to prevent critical progression of COVID-19, such as vaccinations and targeting young adults especially having risk factors.  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