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   20484篇
  免费   1113篇
  国内免费   110篇
耳鼻咽喉   240篇
儿科学   464篇
妇产科学   392篇
基础医学   2613篇
口腔科学   1117篇
临床医学   1464篇
内科学   5012篇
皮肤病学   379篇
神经病学   1795篇
特种医学   476篇
外科学   3214篇
综合类   212篇
一般理论   7篇
预防医学   1576篇
眼科学   459篇
药学   1196篇
中国医学   89篇
肿瘤学   1002篇
  2023年   134篇
  2022年   115篇
  2021年   679篇
  2020年   368篇
  2019年   572篇
  2018年   707篇
  2017年   448篇
  2016年   459篇
  2015年   598篇
  2014年   878篇
  2013年   1032篇
  2012年   1719篇
  2011年   1722篇
  2010年   960篇
  2009年   863篇
  2008年   1457篇
  2007年   1519篇
  2006年   1328篇
  2005年   1270篇
  2004年   1095篇
  2003年   915篇
  2002年   907篇
  2001年   150篇
  2000年   101篇
  1999年   135篇
  1998年   197篇
  1997年   153篇
  1996年   73篇
  1995年   92篇
  1994年   98篇
  1993年   73篇
  1992年   78篇
  1991年   58篇
  1990年   52篇
  1989年   67篇
  1988年   52篇
  1987年   43篇
  1986年   51篇
  1985年   40篇
  1984年   44篇
  1983年   40篇
  1982年   50篇
  1981年   39篇
  1980年   29篇
  1979年   17篇
  1978年   29篇
  1977年   29篇
  1976年   20篇
  1973年   18篇
  1972年   13篇
排序方式: 共有10000条查询结果,搜索用时 859 毫秒
61.
OBJECTIVE: The aim of this study was to measure leakage of 4 resin-based sealers. STUDY DESIGN: Four groups of premolars (n = 60) were prepared using GT Rotary files and the crown-down technique and filled by the single-cone technique with AH26, AHPlus, EndoREZ, and an experimental MBP as sealer. Leakage was measured using the fluid filtration method after 15, 30, and 60 days and determined as microL/min(-1) x 10 psi. RESULTS: Statistical analysis by ANOVA and Tukey HSD test indicated that root fillings with AH Plus and the MBP showed lower leakage values after 15 days (P < .05). At 30 days, AH26 presented higher leakage values when compared to other sealers (P < .05). At 60 days, MBP and AH Plus presented the lower leakage values, differing significantly from EndoREZ (P < .05). CONCLUSION: It was observed that AH Plus and the experimental MBP showed lower leakage after 60 days than AH 26 and EndoREZ.  相似文献   
62.
BACKGROUND: Previous research found an association between single nucleotide polymorphisms (SNPs) in the promoter region of DRD4 and statistically derived phenotypes generated from attention-deficit/hyperactivity disorder (ADHD) symptoms. We sought to replicate this finding by using the same methodology in an independent sample of ADHD individuals. METHODS: Four SNPs were genotyped in and around DRD4 in 2631 individuals in 642 families. We developed a quantitative phenotype at each SNP by weighting nine inattentive and nine hyperactive-impulsive symptoms. The weights were selected to maximize the heritability at each SNP. Once a quantitative phenotype was generated at each SNP, the screening procedure implemented in PBAT was used to select and test the five SNPs/genetic model combinations with the greatest power to detect an association for DRD4. RESULTS: One of the four SNPs was associated with the quantitative phenotypes generated from the ADHD symptoms (corrected p-values = .02). A rank ordering of the correlation between each of the ADHD symptoms and the quantitative phenotype suggested that hyperactive-impulsive symptoms were more strongly correlated with the phenotype; however, including inattentive symptoms was necessary to achieve a significant result. CONCLUSIONS: This study partially replicated a previous finding by identifying an association between rs7124601 and a quantitative trait generated from ADHD symptoms. The rs7124601 is in linkage disequilibrium (LD) with the SNPs identified previously. In contrast to the previous study, this finding suggests that both hyperactive-impulsive and inattentive symptoms are important in the association.  相似文献   
63.
This study was designed to study the effects of angiotensin converting enzyme inhibitors (ACEI) following treatment with trandolapril (0.3 mg kg(-1) day(-1)) on carotid arterial responsiveness in normotensive Wistar rats. Carotid arteries were obtained from control or trandolapril-treated animals and mounted in an isolated organ bath. Reactivity to angiotensin II (Ang II), phenylephrine (Phe) and KCl was studied. Agonist concentration-response curves were constructed in either the absence or presence of the endothelium or after incubation with L-NAME (10(-6) M), HOE140 (10(-7) M) or indomethacin (10(-5) M). Trandolapril treatment decreased the Ang II and Phe potencies in carotid arteries, but did not affect the maximal response. The KCl responses (potency and Emax) were similar in both control and trandolapril-treated arteries. The absence of endothelium increased the response to both agonists in control and trandolapril-treated arteries; however, the inhibitory component from the endothelial layer of the Phe response was greater in trandolapril-treated animals than in control animals. The presence of L-NAME or HOE140 abolished the changes in the potency values of trandolapril-treated animals. The presence of indomethacin did not change the effect of trandolapril on the potency values of both agonists. We conclude that trandolapril treatment decreased the carotid arterial reactivity in normotensive rats and that this effect is endothelium-dependent. Furthermore, the involvement of B(2)-receptors and NO production, but not of prostaglandins, is suggested in this mechanism.  相似文献   
64.
65.
Treatment stability is one of the most important objectives in orthodontics, but, despite decades of research, it is still agreed that the stability of aligned teeth is variable and largely unpredictable. This study aimed to evaluate the relapse of mandibular anterior crowding in patients treated without mandibular premolar extraction. The sample comprised 40 patients of both sexes with Class I or II malocclusions who received nonextraction treatment in the mandibular arch with edgewise mechanics. Lateral cephalograms and dental casts of each patient were obtained at pretreament, posttreatment, and 5 years postretention. Relapse of mandibular anterior crowding was assessed, and associations between this relapse and other clinical factors were also investigated. Mandibular anterior crowding was measured by the Little irregularity index, and the data were evaluated by the Mann-Whitney test. The mean relapse of mandibular anterior crowding was 1.95 mm (26.54%) over the long term. No clinical factor studied was predictive of crowding relapse in the long term.  相似文献   
66.
INTRODUCTION : In patients with common bile duct (CBD) stones, the diameter of the CBD is usually dilated. After surgery, the behavior of CBD diameter is not clearly known. OBJECTIVE : To determine at a late follow-up the width of CBD before and after choledochostomy for CBD stones. MATERIAL AND METHODS : In this prospective study, 39 patients with gallstones and CBD stones were included. They were 30 women and 9 men with a mean age of 52.6 years. In all ultrasound, determination of the CBD caliber before and 12 years after surgery was performed. RESULTS : The mean value of the inner diameter of the CBD before surgery was 11.6 and 12.3 mm in patients below or above 60 years, respectively. Measurement 12 years after surgery showed a mean decrease of nearly 50% of preoperative values, which was highly significant (p < 0.0001). However, either below or above 60 years, only 75% of the patients showed this decrease, whereas 25% remained unchanged. CONCLUSION : The dilated preoperative CBD returns to normal or near normal values in 3/4 of the patients after surgical exploration of the CBD and extraction of the stones.  相似文献   
67.
68.
K B Saunders  S S Fernando  H R Dalton    A Joseph 《Thorax》1994,49(7):725-727
A 37 year old patient with chronic active hepatitis progressing to cirrhosis presented with increasing breathlessness and was found to be hypoxic with finger clubbing. A progressive exercise study with measurement of oxygen saturation (SaO2) showed abnormally high ventilation and desaturation to 81% at 100 W. Serial studies over nearly two years showed, first, deterioration, then improvement with lower ventilation and higher saturation levels at all work loads. This could not be correlated with any change in treatment with azathioprine, prednisolone, or propranolol.  相似文献   
69.
The aim of this study was to evaluate the rate of alcohol recidivism after orthotopic liver transplantation (OLT) for alcoholic liver disease (ALD) and its influence on the allograft and patient survival, as well as the development of comorbidities and de novo cancers. The study was performed on 54 subjects previously analyzed and transplanted in our center for ALD, whose follow-up was prolonged to a mean of 99.2 (SD 31.7) months (range, 14-155). Medical records were reviewed, and data on alcohol consumption, therapeutic compliance, graft evolution, rejection, infections, comorbidities, rates of de novo malignancies and other clinical events, and survival were collected. Comparisons between groups were performed by the Fisher's exact test, and survival was assessed by the Kaplan-Meier method. Survival curves were compared using the Mantel-Cox statistic. The risk of death resulting from alcohol recidivism was analyzed with a Cox proportional hazards model. Fourteen patients who underwent transplantation for ALD (25.9%) returned to alcohol use between 5.0 and 86.9 months after OLT (median, 47.5). There was no significant association between the presence or absence of alcohol recidivism and the occurrence of graft rejection, infections, associated comorbidities after OLT, or compliance. The 5- and 10-year survival rates for patients with alcohol recidivism were 92.9% and 45.1%, respectively, compared with 92.4% and 85.5%, respectively, for patients without alcohol recidivism. These figures show significantly lower survival rates in recidivistic patients after 10 years (P < 0.01, Mantel-Cox). The fact that patients who resumed alcohol consumption have a worse 10-year survival rate might be attributed to a higher frequency of deaths, primarily from cancer and cardiovascular events.  相似文献   
70.
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