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   22178篇
  免费   1906篇
  国内免费   1741篇
耳鼻咽喉   161篇
儿科学   187篇
妇产科学   205篇
基础医学   2612篇
口腔科学   320篇
临床医学   3031篇
内科学   3308篇
皮肤病学   250篇
神经病学   1069篇
特种医学   755篇
外国民族医学   16篇
外科学   2256篇
综合类   3998篇
现状与发展   3篇
一般理论   1篇
预防医学   1266篇
眼科学   714篇
药学   2490篇
  24篇
中国医学   1168篇
肿瘤学   1991篇
  2024年   82篇
  2023年   381篇
  2022年   1046篇
  2021年   1187篇
  2020年   890篇
  2019年   698篇
  2018年   753篇
  2017年   761篇
  2016年   685篇
  2015年   1077篇
  2014年   1306篇
  2013年   1124篇
  2012年   1700篇
  2011年   1789篇
  2010年   1100篇
  2009年   819篇
  2008年   1138篇
  2007年   1096篇
  2006年   1152篇
  2005年   986篇
  2004年   740篇
  2003年   702篇
  2002年   621篇
  2001年   497篇
  2000年   572篇
  1999年   554篇
  1998年   373篇
  1997年   316篇
  1996年   229篇
  1995年   226篇
  1994年   219篇
  1993年   121篇
  1992年   147篇
  1991年   148篇
  1990年   93篇
  1989年   100篇
  1988年   83篇
  1987年   88篇
  1986年   66篇
  1985年   42篇
  1984年   42篇
  1983年   28篇
  1982年   19篇
  1981年   10篇
  1980年   7篇
  1979年   12篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
BackgroundCough is one of the most common symptoms of coronavirus disease 2019 (COVID-19). However, the prevalence of persistent cough in recovered patients with COVID-19 during a longer follow-up remained unknown. This study aims to investigate the prevalence, and risk factors for postinfectious cough in COVID-19 patients after discharge.MethodsWe conducted a follow-up study for 129 discharged patients with laboratory-confirmed COVID-19 in two large hospitals located in Hubei Province, China from January 2020 to December 2020. Baseline demographics, comorbidities and smoking history were extracted from the medical record. Current symptoms and severity were recorded by a uniform questionnaire. Spirometry, diffuse function and chest computed tomography (CT) were performed on part of patients who were able to return to the outpatient department at follow-up.ResultsThe median (interquartile range) follow-up time was 8.1 (7.9–8.5) months after discharge. The mean (standard deviation) age was 51.5 (14.9) years and 57 (44.2%) were male. A total of 27 (20.9%) patients had postinfectious cough (>3 weeks), 6 patients (4.7%) had persistent cough by the end of follow-up, including 3 patients with previous chronic respiratory diseases or current smoking. Other symptoms included dyspnea (6, 4.7%), sputum (4, 3.1%), fatigue (4, 3.1%), and anorexia (4, 3.1%) by the end of follow-up. Thirty-six of 41 (87.8%) patients showed impaired lung function or diffuse function, and 39 of 50 (78.0%) patients showed abnormal CT imaging. Patients with postinfectious cough demonstrated more severe and more frequent cough during hospitalization (P<0.001), and more chronic respiratory diseases (P=0.01). In multivariate logistic regression analysis, digestive symptoms during hospitalization [odds ratio (OR) 2.95, 95% confidence interval (CI): 1.10–7.92] and current smoking (OR 6.95, 95% CI: 1.46–33.14) were significantly associated with postinfectious cough of COVID-19.ConclusionsA small part of patients developed postinfectious cough after recovery from COVID-19, few patients developed chronic cough in spite of a higher proportion of impaired lung function and abnormal lung CT image. Current smoking and digestive symptoms during hospitalization were risk factors for postinfectious cough in COVID-19.  相似文献   
92.
背景 酒精使用障碍(AUD)是常见的慢性复发性精神疾病,对于重度AUD,需早期快速识别并及时妥善处理,以避免不可逆的伤害发生。目前,对AUD严重程度的评估主要基于临床医师对患者的精神检查,关于AUD严重程度影响因素及预测模型的研究有限。目的 分析AUD患者疾病严重程度的影响因素,构建风险预测模型,为评估AUD患者的疾病严重程度提供参考。方法 回顾性选取2017年1月1日—2022年12月31日南宁市第五人民医院收治的、符合《精神障碍诊断与统计手册(第5版)》(DSM-5)AUD诊断标准的1 358例首次住院患者为研究对象,收集其基本资料,根据疾病严重程度分为轻中度组(n=330)和重度组(n=1 028)。按7∶3将患者分为训练集和测试集,在训练集样本中构建Logistic回归模型,在测试集样本中采用受试者工作特征(ROC)曲线分析该模型对AUD严重程度的预测价值。结果 与轻中度组相比,重度组居住地在城市(χ2=7.804)、农民(χ2=17.991)、饮酒频率高于1~2次/天(χ2=35.267)的比例更高,初次饮酒年龄更大(t=-3.858),合并躯体疾病数量更多(Z=-22.782),γ-谷氨酰胺转移酶(χ2=259.940)和总胆红素异常(χ2=148.552)的比例更高(P均<0.01)。在训练集中进行的Logistic分析结果表明,农民(OR=2.024,95% CI:1.352~3.029)、初次饮酒年龄较大(OR=1.075,95% CI:1.025~1.129)、用餐时间外也饮酒(OR=3.988,95% CI:2.408~6.606)、总胆红素水平异常(OR=1.034,95% CI:1.000~1.069)、合并更多的躯体疾病(OR=4.386,95% CI:2.636~7.298)是AUD更严重的危险因素。该模型在测试集中的ROC曲线下面积(AUC)为0.906。结论 在精神专科医院中,农民、初次饮酒年龄较大、用餐时间外也饮酒、总胆红素水平异常、合并更多的躯体疾病可能是重度AUD的危险因素。  相似文献   
93.
Fracturing pumpheads are typical pressure vessels that experience frequent fatigue failure under the effect of notches in their cross-bore. To enhance the fatigue life of fracturing pumpheads, the study of the notch effect is indispensable and important to establish a reliable mathematical model to predict their fatigue life. In the present paper, two novel fatigue life prediction models are proposed for notched specimens. In these models, two new geometric fatigue failure regions are defined to improve the weight function. Finally, the elaborated novel stress-field intensity approach was applied to three different types of notched specimens. Experiment results indicate that the new SFI approach achieves 47.82%, 39.48%, and 31.85% higher prediction accuracy than the traditional SFI approach, respectively. It was found that the modified SFI approach provided better predictions than the traditional SFI approach and the TCD method. The II-th novel SFI approach had the highest accuracy, and the I-th novel SFI approach was more suitable for sharply notched specimens.  相似文献   
94.
Objective: Osteoporosis (OP) is the most common bone disease. The genetic and metabolic factors play important roles in OP development. However, the genetic basis of OP is still elusive. The study aimed to explore the relationships between OP and dietary habits. Methods: This study used large-scale genome-wide association study (GWAS) summary statistics from the UK Biobank to explore potential associations between OP and 143 dietary habits. The GWAS summary data of OP included 9434 self-reported OP cases and 444,941 controls, and the GWAS summary data of the dietary habits included 455,146 participants of European ancestry. Linkage disequilibrium score regression (LDSC) was used to detect the genetic correlations between OP and each of the 143 dietary habits, followed by Mendelian randomization (MR) analysis to further assess the causal relationship between OP and candidate dietary habits identified by LDSC. Results: The LDSC analysis identified seven candidate dietary habits that showed genetic associations with OP including cereal type such as biscuit cereal (coefficient = −0.1693, p value = 0.0183), servings of raw vegetables per day (coefficient = 0.0837, p value = 0.0379), and spirits measured per month (coefficient = 0.115, p value = 0.0353). MR analysis found that OP and PC17 (butter) (odds ratio [OR] = 0.974, 95% confidence interval [CI] = (0.973, 0.976), p value = 0.000970), PC35 (decaffeinated coffee) (OR = 0.985, 95% CI = (0.983, 0.987), p value = 0.00126), PC36 (overall processed meat intake) (OR = 1.035, 95% CI = (1.033, 1.037), p value = 0.000976), PC39 (spirits measured per month) (OR = 1.014, 95% CI = (1.011, 1.015), p value = 0.00153), and servings of raw vegetables per day (OR = 0.978, 95% CI = (0.977, 0.979), p value = 0.000563) were clearly causal. Conclusions: Our findings provide new clues for understanding the genetic mechanisms of OP, which focus on the possible role of dietary habits in OP pathogenesis.  相似文献   
95.
为了探讨突触素(SYN)在不同周龄阶段胎儿端脑额叶中的表达与胎儿额叶皮质突触发育的关系,本研究采用免疫组织化学方法观察突触素在不同周龄阶段胎儿额叶的表达水平,利用计算机图像分析技术测量不同周龄阶段胎儿额叶突触素表达的平均光密度;同时取材、常规电镜技术处理、透射电镜观察额叶突触发育的超微结构变化。结果显示:(1)光镜下各组均可见SYN免疫阳性产物主要表达于胎儿的额叶皮层,其表达量随周龄的增加而增强,各组间呈现显著性差异(P<0.05),其中16~24周胎儿额叶的阳性产物位于神经元的胞浆内,呈均匀的浅黄色,神经元突起内未见阳性产物;25~29周额叶的阳性产物呈黄色,在胞浆和突起内均可见,但阳性产物的量却下降;而30~39周额叶的SYN阳性产物呈棕黄色的点状或颗粒状,主要位于神经元的突起内,神经元胞浆内未见阳性产物,阳性产物的量显著增加;(2)透射电镜下19~36周胎儿大脑额叶均可见到突触样结构,随着周龄的增加,突触的数量逐渐增多,结构逐渐清晰和完整。上述结果提示SYN的表达可以反映胎儿神经系统发育的程度,SYN的表达与突触的发育是一致的;SYN在胎儿大脑额叶的表达部位经历由神经元胞浆内表达为主到神经元终末表达为主的这一过程,可能是由于SYN先是在神经元胞浆内合成,再随着神经元的发育而逐步转移到神经元突起的末梢部位。  相似文献   
96.
植物化感作用及其在中药材栽培中的应用   总被引:1,自引:0,他引:1  
本文介绍了目前植物化感作用的研究领域及其进展,包括化感物质的收集、分离和鉴定,化感物质作用机理以及影响化感作用的因素等方面,分析了药用植物化感作用较为严重的原因以及在栽培过程中追求药材质量的同时很可能会加剧其化感作用的特点,并且从栽培措施、化感育种以及改善土壤微生态环境等几个方面提出了有效利用和克服药用植物化感作用的措施,旨在为中药材规范化种植提供理论和方法依据。  相似文献   
97.
98.
Rationale:Femtosecond laser-assisted cataract surgery (FLACS) has grown in popularity among ophthalmologists as a novel surgical technique. However, malignant glaucoma (MG) is a complication of FLACS. Herein, we report a case of MG following FLACS.Patient concerns:A 66-year-old woman presented with complaints of blurred vision in the right eye and a foreign body sensation in both eyes. Ophthalmological examinations showed that the corrected distance visual acuity was 20/50 and 20/25 in the right and left eyes, respectively. Without any topical anti-glaucoma medication, the intraocular pressure (IOP) was 20 mmHg in the right eye and 17 mmHg in the left eye. Slit-lamp examination of the right eye revealed a transparent cornea with a defect in the punctate overlying epithelium; the central anterior chamber depth was shallow the peripheral iris laser shot was visible, the pupil was normal, and the lens was mainly cortical opacified.Diagnoses:Based on the patient''s symptoms, examination results, and preliminary diagnoses, age-related cataract in the right eye, binocular post-antiglaucoma surgery, pseudophakicin in the left eye, and Sjogren syndrome were included.Interventions:FLACS was performed to facilitate anterior capsulotomy and segmentation of the nucleus in the right eye. MG occurred after the femtosecond procedure, and with the treatment of medicines combined with phacoemulsification, IOP was eventually normal without further antiglaucoma therapy.Outcomes:IOP was 16 mmHg on postoperative day 1. Ocular ultrasonography revealed no choroid detachment or hemorrhage in the right eye. Two weeks postoperatively, uncorrected visual acuity was 20/25, and IOP remained normal with no further antiglaucoma treatment on 1 month postoperatively.Conclusions:We describe the occurrence of MG after FLACS and illustrate that miosis and bubble formation after FLACS may be risk factors for MG during FLACS.  相似文献   
99.
BackgroundAlthough early diagnosis and management are critical for prognosis of pediatric sepsis, there are no specific diagnostic biomarkers for the hyperinflammatory state and organ dysfunction, important stages of sepsis.MethodsWe enrolled 129 children with infection into three groups: non‐sepsis infection (33), Sepsis 1.0 (hyperinflammatory state, 67), and Sepsis 3.0 (organ dysfunction, 29). Another 32 children with no infections were included as controls. Serum C‐reactive protein (CRP), procalcitonin (PCT), interleukin (IL)‐1β, IL‐2, IL‐4, IL‐5, IL‐6, IL‐8, IL‐10, IL‐12p70, IL‐17, tumor necrosis factor (TNF)‐α, interferon (IFN)‐α, and IFN‐γ were assessed to diagnose the two stages, and their diagnostic capacities were evaluated using receiver operating characteristic (ROC) curves. We also examined whether combining biomarkers improved diagnostic efficiency.ResultsSignificantly higher CRP, PCT, and IL‐6 levels were detected in the Sepsis 1.0 than the non‐sepsis infection group (p < 0.001). The areas under the curve (AUCs) for diagnosing Sepsis 1.0 were 0.974 (CRP), 0.913 (PCT) and 0.919 (IL‐6). A combination of any two biomarkers increased diagnostic sensitivity to ≥92.54% and specificity to 100.00%. Significantly higher PCT, IL‐8, and IL‐10 levels were found in the Sepsis 3.0 than the Sepsis 1.0 group (p ≤ 0.01), with AUCs for diagnosing Sepsis 3.0 0.807 (PCT), 0.711 (IL‐8), and 0.860 (IL‐10). Combining these three biomarkers increased diagnostic sensitivity to 96.55% and specificity to 94.03%.ConclusionIn pediatric sepsis, combining any two of CRP, PCT, and IL‐6 can accurately diagnose the hyperinflammatory state and increase diagnostic specificity. Early diagnosis of organ dysfunction requires a combination of PCT, IL‐8, and IL‐10.  相似文献   
100.
By using glycidol as a catalyst, high porosity, low-density resorcinol (R) and formaldehyde (F) aerogels and carbon aerogels (CAs) were synthesized via a sol-gel method. The effect of glycidol and water on the color, density, morphology, textual characteristics and adsorption properties of the resultant RF aerogels and CAs were investigated in detail. The results revealed that the properties of RF aerogels and CAs can be controlled by adjusting the amount of glycidol and water. The resultant RF aerogels and CAs were porous materials, the minimum densities of RF aerogels and CAs were 96 and 110 mg cm−3 respectively while the maximum specific surface areas of RF aerogels and CAs were 290 and 597 m2 g−1. The maximum adsorption capacity of CAs was about 125 mg g−1 on Rhodamine B, which was higher than that of some reported CAs catalyzed by base and acid catalysts. The sol-gel mechanisms of RF aerogels and CAs can be attributed to the opening of the epoxy group of glycidol in the mixture of R and F.

The sol-gel mechanism of glycidol-catalyzed RF aerogels is the opening of the epoxy ring rather than the preservation the of epoxy ring.  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