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   664篇
  免费   24篇
  国内免费   27篇
耳鼻咽喉   8篇
儿科学   19篇
妇产科学   23篇
基础医学   34篇
口腔科学   15篇
临床医学   55篇
内科学   137篇
皮肤病学   11篇
神经病学   36篇
特种医学   17篇
外科学   84篇
综合类   76篇
预防医学   62篇
眼科学   14篇
药学   47篇
中国医学   26篇
肿瘤学   51篇
  2023年   11篇
  2022年   27篇
  2021年   22篇
  2020年   22篇
  2019年   78篇
  2018年   64篇
  2017年   21篇
  2016年   18篇
  2015年   14篇
  2014年   36篇
  2013年   27篇
  2012年   28篇
  2011年   20篇
  2010年   19篇
  2009年   23篇
  2008年   12篇
  2007年   10篇
  2006年   15篇
  2005年   42篇
  2004年   43篇
  2003年   43篇
  2002年   23篇
  2001年   12篇
  2000年   7篇
  1999年   6篇
  1998年   2篇
  1997年   4篇
  1996年   2篇
  1994年   1篇
  1993年   2篇
  1992年   1篇
  1988年   1篇
  1987年   1篇
  1986年   2篇
  1985年   9篇
  1984年   6篇
  1983年   4篇
  1982年   2篇
  1981年   5篇
  1980年   7篇
  1979年   4篇
  1978年   3篇
  1977年   5篇
  1976年   5篇
  1975年   4篇
  1974年   1篇
  1973年   1篇
排序方式: 共有715条查询结果,搜索用时 15 毫秒
101.
Sinus rhythm tracings, including sinus tachycardia and bradycardia, are characterized quantitatively by means of an ECG measurement program which has been subjected to rigorous evaluation. The analysis is performed on tracings of short duration (10 sec). The features of regularity and stability are considered for the R wavetrain. Regularity is evaluated from the normalized differences between sucessive RR intervals. Stability is determined by the ratio of maximum and minimum RR interval durations. Due to the difficulities of automatic beat-to-beat detection and measurement of P waves, an estimate of the PR interval is obtained from a pseudo-PR interval determined from certain features of the P and R wavetrains. The constancy of this pseudo-PR interval is evaluated, and its absolute value is uded as a characteristic of the type of sinus rhythm.  相似文献   
102.

Background

Multiple quantitative trait loci for blood pressure (BP) have been localized throughout human and rodent genomes. Few of them have been functionally identified especially in humans, and little is known about their pathogenic directionality when identified. We focused on Chrm3 encoding the muscarinic cholinergic receptor 3 (M3R) as the causal gene for C17QTL1 in the Dahl salt-sensitive rat model.

Methods and Results

Congenic knock-ins, gene-specific knockout, and ex vivo and in vivo function studies were applied in the Dahl salt-sensitive rat model of polygenic hypertension. A Chrm3 missense T1667C mutation in the last intracellular domain functionally correlated with a rise in BP increased the M3R signalling and resensitization, and adrenal epinephrogenesis. Gene targeting that abolished the M3R function without affecting any of noncoding Chrm3 variants caused a decrease in BP, indicating that the M3R-mediated signalling promotes hypertension. In contrast, removing 8 amino acids from the M3R first extracellular loop had no effect on BP.

Conclusions

The M3R-specialized signalling constitutes a new pathway of hypertension pathogenesis within the context of a polygenic and quantitative trait. Increased epinephrine in the circulation and secreted from the adrenal glands are suggestive of a molecular mechanism partially mediating M3R to promote hypertension. The structure-function relationships for various M3R domains in their effects on BP pave the way for identifying missense mutations that impact functions on BP as potential diagnostic targets.  相似文献   
103.

Introduction

The contrast sensitivity test determines the quality of visual function in patients with multiple sclerosis (MS). The purpose of this study is to analyse changes in visual function in patients with relapsing-remitting MS with and without a history of optic neuritis (ON).

Methods

We conducted a longitudinal study including 61 patients classified into 3 groups as follows: a) disease-free patients (control group); b) patients with MS and no history of ON; and c) patients with MS and a history of unilateral ON. All patients underwent baseline and 6-year follow-up ophthalmologic examinations, which included visual acuity and monocular and binocular Pelli-Robson contrast sensitivity tests.

Results

Monocular contrast sensitivity was significantly lower in MS patients with and without a history of ON than in controls both at baseline (P=.00 and P=.01, respectively) and at 6 years (P=.01 and P=.02). Patients with MS and no history of ON remained stable throughout follow-up whereas those with a history of ON displayed a significant loss of contrast sensitivity (P=.01). Visual acuity and binocular contrast sensitivity at baseline and at 6 years was significantly lower in the group of patients with a history of ON than in the control group (P=.003 and P=.002 vs P=.006 and P=.005) and the group with no history of ON (P=.04 and P=.038 vs P=.008 and P=.01). However, no significant differences were found in follow-up results (P=.1 and P=.5).

Conclusions

Monocular Pelli-Robson contrast sensitivity test may be used to detect changes in visual function in patients with ON.  相似文献   
104.

Objectives

The role of neovascularisation in tendinopathy is still poorly understood, potentially due to technical limitations of conventional power Doppler ultrasound. This study aimed to investigate the association between contrast-enhanced ultrasound (CEUS) microvascular volume (MV), Victorian Institute of Sports Assessment-Achilles (VISA-A) scores and intrinsic Achilles tendon tenderness, as well as two different Power Doppler modes.

Design

Cross-sectional study.

Methods

20 individuals with uni- or bilateral Achilles tendinopathy completed a VISA-A questionnaire, and underwent microvascular volume measurements of the Achilles tendon mid-portion using both conventional, ultrasensitive (SMI?) power Doppler ultrasound and CEUS. Intrinsic tendon tenderness was assessed with sensation detection threshold to extracorporeal shock waves (ESW). Linear Mixed Model analysis was used to determine the association between microvascular volume (MV), VISA-A, and ESW-detection threshold for both symptomatic and asymptomatic Achilles tendons.

Results

There was a significant association between VISA-A and MV (B = ?5.3, 95%CI = [?8.5; ?2.0], P = 0.0004), and between MV and symptom duration (B = ?1.7, 95%CI = [?3.2; ?5.0], P = 0.023). No significant associations were found between power Doppler ultrasound and CEUS-based MV or between CEUS-based MV and ESW-detection threshold. In comparison with conventional power Doppler ultrasound, SMI? showed on average similar detection capacity for neovessels in the mid-portion of the Achilles tendon, whilst being superior for detecting neovessels within Kager’s fat pad (t = 3.46, 95%CI = [0.27; 1.03], P < 0.005).

Conclusions

Our results indicate that CEUS-based MV of the Achilles tendon is moderately associated with Achilles tendon symptoms. In accordance, CEUS-detected MV could be a novel target for treatment as it seems to be more sensitive than PDU and is correlated with symptoms.  相似文献   
105.
ObjectiveGather epidemiological data pertaining to the prevalence of suspected glaucoma in rural and urban areas of Haiti.DesignCross-sectional pilot study.ParticipantsHaitians of African ancestry.MethodsWe conducted a cross-sectional study on 211 Haitians of African ancestry (76 males and 135 females) aged 40 years and over. The mean age was 54.6 ± 10.9 years. The data were collected in glaucoma screening clinics at health fairs held in urban Port-au-Prince (57 people) and three rural regions (154 people) during a two-week medical mission to Haiti in November 2014. An ophthalmic exam with intraocular pressure measurement (with Tonopen) and dilated fundus exam were conducted.ResultsThe average C/D was 0.41 ± 0.18. The prevalence of suspected glaucoma, defined as C/D ≥ 0.7, asymmetry of ≥0.2 or significant rim notching, was 14.2%. The average IOP was 18.4 ± 5.4. Ocular hypertension (IOP ≥ 24mmHg) was found in 19.0% of participants.ConclusionsThe prevalence of ocular hypertension and glaucoma based on suspect optic nerves in our sample population was high, indicating a strong need for access to ophthalmologic care in the Haitian population.  相似文献   
106.
PTEN、p27在口腔粘膜白斑和口腔癌组织中的表达及意义   总被引:1,自引:0,他引:1  
目的 探讨抑癌基因PTEN、p2 7在口腔粘膜白斑 (oralleukoplakia ,OLK)和口腔癌 (oralsquamouscellcancer,OSCC)组织中的蛋白表达及意义。方法 应用免疫组化S -P法检测 10例正常口腔粘膜、2 5例口腔粘膜白斑 (其中白斑伴上皮异常增生 15例 ,白斑不伴上皮异常增生 10例 )及 32例口腔癌组织中抑癌基因PTEN和p2 7的蛋白表达情况。结果 正常口腔粘膜和白斑不伴上皮异常增生组织中PTEN和 p2 7蛋白全部阳性表达 ;白斑伴上皮异常增生组织中PTEN和 p2 7蛋白阳性表达率分别为93.3%、73.3%。OSCC组织中PTEN蛋白阳性表达率为71.9% ,其中高、中、低分化OSCC组织中PTEN蛋白阳性表达率分别为 85 .7%、75 %和 33.3% ,统计学分析表明PTEN在OSCC组织中的蛋白表达与组织分化程度明显相关 (P <0 .0 5 )。OSCC组织中 p2 7蛋白的阳性表达率为4 0 .6 % ,其中高、中、低分化OSCC组织中p2 7蛋白的阳性表达率分别为 4 2 .9%、4 1.7%和 33.3% ,统计学分析表明p2 7在OSCC组织中的蛋白表达与组织分化程度无明显相关 (P >0 .0 5 )。结论 OSCC组织中PTEN和 p2 7蛋白的阴性表达率较高 ,说明PTEN和 p2 7基因突变或缺失在OSCC的发生发展过程中起重要作用。  相似文献   
107.
Objectives To evaluate the impact of Oportunidades, a large‐scale, conditional cash transfer programme in Mexico, on birthweight. The programme provides cash transfers to low‐income, rural households in Mexico, conditional on accepting nutritional supplements health education, and health care. Methods The primary analyses used retrospective reports from 840 women in poor rural communities participating in an effectiveness study and randomly assigned to incorporation into the programme in 1998 or 1999 across seven Mexican states. Pregnant women in participating households received nutrition supplements and health care, and accepted cash transfers. Using multivariate and instrumental variable analyses, we estimated the impact of the programme on birthweight in grams and low birthweight (<2500 g), receipt of any pre‐natal care, and number of pre‐natal visits. Results Oportunidades beneficiary status was associated with 127.3 g higher birthweight among participating women and a 4.6 percentage point reduction in low birthweight. Conclusion The Oportunidades conditional cash transfer programme improved birthweight outcomes. This finding is relevant to countries implementing conditional cash transfer programmes.  相似文献   
108.
Previous reports on the inverse association between ‘mate’ intake (infusion of Ilex Paraguariensis herb) and breastcancer (BC) risk led us to consider two main roles for the infusion: as a substantial antioxidant contributor and asa hormone regulator, particularly through anti-aromatase capacities. Since menstrual-reproductive risk factors forBC reflect women’s estrogenic exposure during the reproductive lifespan, and considering that ‘mate’ intake exertsputative stronger protection among high antioxidant contributors, we attempted to analyze interactions among theinfusion, hormon-linked reproductive factors and BC risk, which have hitherto remained unexplored. We analyzed adatabase of 572 BC incident cases and 889 controls. Women were interviewed with a specific questionnaire featuringsocio-demographic, lifestyle and reproductive variables (age at menarche, 1st live birth and menopause; number of livebirths; breastfeeding months), and a food frequency questionnaire, focusing on ‘mate’ intake (consumer status, dailyintake, age at start, age at quit, duration of habit). Odds ratios (OR) and their 95% confidence Intervals were calculatedthrough unconditional logistic regression, adjusting for relevant potential confounders. ‘Mate’ intake showed stronginverse associations with some high-risk hormone-related factors: early menarche, nulliparity, low breastfeeding, longreproductive years and high number of ovulatory cycles. Moreover, all subsets of high dietary energy demonstratedeven stronger associations. In conclusion, regarding exposure to known hormone risk factors, we found strong inverseassociations between high ‘mate’ intake and BC, which were greater among those consuming higher calorific diets.Our analyses support possible combined antioxidant and antiestrogenic effects for ‘mate’ infusions.  相似文献   
109.
We propose a Deep learning-based weak label learning method for analyzing whole slide images (WSIs) of Hematoxylin and Eosin (H&E) stained tumor tissue not requiring pixel-level or tile-level annotations using Self-supervised pre-training and heterogeneity-aware deep Multiple Instance LEarning (DeepSMILE). We apply DeepSMILE to the task of Homologous recombination deficiency (HRD) and microsatellite instability (MSI) prediction. We utilize contrastive self-supervised learning to pre-train a feature extractor on histopathology tiles of cancer tissue. Additionally, we use variability-aware deep multiple instance learning to learn the tile feature aggregation function while modeling tumor heterogeneity. For MSI prediction in a tumor-annotated and color normalized subset of TCGA-CRC (n=360 patients), contrastive self-supervised learning improves the tile supervision baseline from 0.77 to 0.87 AUROC, on par with our proposed DeepSMILE method. On TCGA-BC (n=1041 patients) without any manual annotations, DeepSMILE improves HRD classification performance from 0.77 to 0.81 AUROC compared to tile supervision with either a self-supervised or ImageNet pre-trained feature extractor. Our proposed methods reach the baseline performance using only 40% of the labeled data on both datasets. These improvements suggest we can use standard self-supervised learning techniques combined with multiple instance learning in the histopathology domain to improve genomic label classification performance with fewer labeled data.  相似文献   
110.
目的 了解格林-巴利综合征(GBS)患者蛋白质及血脂代谢指标分布特征,探讨蛋白质及血脂代谢与GBS之间的关系.方法 共收集首都医科大学附属北京天坛医院2018-2020年90例确诊GBS患者作为GBS组,从不同年龄、性别、严重程度、分型、治疗前后等方面对蛋白质及血脂代谢指标进行分析;同时选取性别、年龄匹配的60例体检健...  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