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   15200篇
  免费   956篇
  国内免费   229篇
耳鼻咽喉   223篇
儿科学   126篇
妇产科学   151篇
基础医学   2545篇
口腔科学   286篇
临床医学   1428篇
内科学   2841篇
皮肤病学   492篇
神经病学   1101篇
特种医学   1268篇
外科学   1788篇
综合类   48篇
一般理论   3篇
预防医学   502篇
眼科学   264篇
药学   1849篇
中国医学   270篇
肿瘤学   1200篇
  2024年   8篇
  2023年   126篇
  2022年   477篇
  2021年   664篇
  2020年   317篇
  2019年   467篇
  2018年   560篇
  2017年   466篇
  2016年   648篇
  2015年   880篇
  2014年   1027篇
  2013年   1106篇
  2012年   1499篇
  2011年   1522篇
  2010年   901篇
  2009年   681篇
  2008年   902篇
  2007年   867篇
  2006年   722篇
  2005年   650篇
  2004年   567篇
  2003年   409篇
  2002年   317篇
  2001年   168篇
  2000年   136篇
  1999年   80篇
  1998年   45篇
  1997年   29篇
  1996年   24篇
  1995年   11篇
  1994年   12篇
  1993年   7篇
  1992年   22篇
  1991年   14篇
  1990年   13篇
  1989年   11篇
  1988年   6篇
  1987年   3篇
  1986年   8篇
  1985年   6篇
  1983年   3篇
  1977年   1篇
  1976年   2篇
  1974年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
Interleukin-1 (IL-1), a cytokine produced predominantly by cells from the macrophage lineage, can affect multiple neuroendocrine and metabolic functions. IL-1alpha production by cultured peripheral blood mononuclear cells from an obese group was significantly elevated in comparison to a control group. The aim of this study was to investigate whether the IL-1alpha polymorphism and Sasang constitution, a major branch in Korean traditional medicine, were related to obesity. Genotyping was done in 182 healthy females with a marked variation in body mass index (BMI) by a PCR-restriction fragment length polymorphism assay. The T allele was associated with decreased BMI (p = 0.020). In a subgroup with BMI values ranging from 27 approximately 29 kg/m(2), the frequency of the T allele was significantly decreased (p = 0.004, odds ratio, OR = 0.141 compared to a subgroup with a BMI values less than 25 Kg/m(2)). In addition, in Taeumin female subjects, the frequency of the IL-1alpha T allele was markedly decreased in a subgroup with BMI values in the range of 27 approximately 29 kg/m(2) compared to a lean group with BMI values less than 25 kg/m(2) (p = 0.004, OR = 0.139). In Korean women, an association was found between -889C/T polymorphism in the regulatory region of the IL-1alpha gene and BMI values. In addition, an association was found among IL-1alpha polymorphism, obesity, and the Sasang constitution.  相似文献   
45.
46.
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   
47.
PurposeTo evaluate the effect of classroom illuminance on the development and progression of myopia in elementary school children.MethodsThe daylight factor, a ratio of inside and outside illuminance, was obtained in 50 elementary schools. The first-grade students in the school with the lowest daylight (LD) factor (LD school, 145 subjects; 0.51%) and with the highest daylight (HD) factor (HD school, 147 subjects; 13.35%) were selected. A survey was conducted to evaluate parental myopia, the amount of near-work and outdoor activities. The refractive error and axial length (AL) were measured at initial and after 6 months. The spherical equivalent, AL, and the survey results were compared between the two schools. The mean AL of the emmetropic children was obtained, and all subjects were divided into two groups, more and less than mean AL. Changes in refractive errors and AL were also compared according to AL.ResultsThe amount of change in spherical equivalent and AL after 6 months were not different between the two schools. Initial prevalence of myopia was high in the HD school. However, it became similar between the two schools after 6 months. The mean AL of 155 emmetropic children was 22.7 ± 0.63 mm. In the 185 children with AL ≥22.7 mm, there was no difference in the AL change between the two schools. However, the change in AL in 107 children with AL <22.7 mm was significantly larger in the LD school (0.19 mm) than that in the HD school (0.15 mm, p = 0.049). Parental myopia, near-work and outdoor activities were not different between the two schools.ConclusionsHigh classroom illuminance during the day reduced axial elongation in eyes of children with a shorter AL. Increase in classroom light level by permitting more sunlight can be a protective measure against the development of myopia.  相似文献   
48.
BackgroundThe objective of this study was to evaluate the immunogenicity of coronavirus disease 2019 (COVID-19) vaccination in patients with end-stage renal disease (ESRD) on hemodialysis.MethodsESRD patients at the hemodialysis center of a tertiary-care university-affiliated hospital and healthy employees at the clinical laboratory center were prospectively recruited between March and June 2021. For severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody analysis, blood samples were collected serially on days 0, 14, 28, and 56 after the first vaccine dose, and on days 7 and 50 after the second dose. Antibodies against the SARS-CoV-2 spike protein were quantified, and SARS-CoV-2 neutralizing antibodies were measured in the serum and plasma.ResultsThirty-one ESRD patients and 55 healthy employees were regularly monitored. Twenty-five (80.6%) ESRD patients on hemodialysis received a mix-and-match strategy with ChAdOx1-BNT162b2 (AZ–Pf group) and six (19.4%) received two doses of ChAdOx1 (AZ–AZ group). ESRD patients on hemodialysis showed lower binding antibody titers and neutralizing antibody activities compared to healthy participants following the first vaccination with ChAdOx1. After the second dose, AZ-Pf group had higher immunogenicity than healthy people on days 7 and 50. The binding antibody titer and neutralizing antibody activities on days 7 and 50 were significantly higher in the AZ–Pf group than in the AZ–AZ group.ConclusionESRD patients on hemodialysis receiving the mix-and-match strategy (ChAdOx1–BNT162b2) have COVID-19 vaccine immunogenicity comparable to healthy individuals receiving two doses of ChAdOx1.Trial RegistrationClinicalTrials.gov Identifier: NCT04871945  相似文献   
49.
The aim of this study is to prepare pH- and redox-sensitive nanoparticles for doxorubicin (DOX) delivery against DOX-resistant HuCC-T1 human cholangiocarcinoma (CCA) cells. For this purpose, L-histidine methyl ester (HIS) was attached to chitosan oligosaccharide (COS) via dithiodipropionic acid (abbreviated as ChitoHISss). DOX-incorporated nanoparticles of ChitoHISss conjugates were fabricated by a dialysis procedure. DOX-resistant HuCC-T1 cells were prepared by repetitive exposure of HuCC-T1 cells to DOX. ChitoHISss nanoparticles showed spherical morphology with a small diameter of less than 200 nm. The acid pH and glutathione (GSH) addition induced changes in the size distribution pattern of ChitoHISss nanoparticles from a narrow/monomodal distribution pattern to a wide/multimodal pattern and increased the fluorescence intensity of the nanoparticle solution. These results indicate that a physicochemical transition of nanoparticles can occur in an acidic pH or redox state. The more acidic the pH or the higher the GSH concentration the higher the drug release rate was, indicating that an acidic environment or higher redox states accelerated drug release from ChitoHISss nanoparticles. Whereas free DOX showed decreased anticancer activity at DOX-resistant HuCC-T1 cells, DOX-incorporated ChitoHISss nanoparticles showed dose-dependent anticancer activity. Intracellular delivery of DOX-incorporated ChitoHISss nanoparticles was relatively increased at an acidic pH and in the presence of GSH, indicating that DOX-incorporated ChitoHISss nanoparticles have superior acidic pH- and redox-sensitive behavior. In an in vivo tumor xenograft model, DOX-incorporated ChitoHISss nanoparticles were specifically delivered to tumor tissues and then efficiently inhibited tumor growth. We suggest that ChitoHISss nanoparticles are a promising candidate for treatment of CCA.  相似文献   
50.
PurposeThe aims of the study were to develop and evaluate a machine learning model with which to predict postnatal growth failure (PGF) among very low birth weight (VLBW) infants.Materials and MethodsOf 10425 VLBW infants registered in the Korean Neonatal Network between 2013 and 2017, 7954 infants were included. PGF was defined as a decrease in Z score >1.28 at discharge, compared to that at birth. Six metrics [area under the receiver operating characteristic curve (AUROC), accuracy, precision, sensitivity, specificity, and F1 score] were obtained at five time points (at birth, 7 days, 14 days, 28 days after birth, and at discharge). Machine learning models were built using four different techniques [extreme gradient boosting (XGB), random forest, support vector machine, and convolutional neural network] to compare against the conventional multiple logistic regression (MLR) model.ResultsThe XGB algorithm showed the best performance with all six metrics across the board. When compared with MLR, XGB showed a significantly higher AUROC (p=0.03) for Day 7, which was the primary performance metric. Using optimal cut-off points, for Day 7, XGB still showed better performances in terms of AUROC (0.74), accuracy (0.68), and F1 score (0.67). AUROC values seemed to increase slightly from birth to 7 days after birth with significance, almost reaching a plateau after 7 days after birth.ConclusionWe have shown the possibility of predicting PGF through machine learning algorithms, especially XGB. Such models may help neonatologists in the early diagnosis of high-risk infants for PGF for early intervention.  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