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   50414篇
  免费   2456篇
  国内免费   407篇
耳鼻咽喉   541篇
儿科学   1075篇
妇产科学   531篇
基础医学   6739篇
口腔科学   896篇
临床医学   3208篇
内科学   12727篇
皮肤病学   1164篇
神经病学   3644篇
特种医学   2148篇
外国民族医学   1篇
外科学   8686篇
综合类   216篇
一般理论   6篇
预防医学   1281篇
眼科学   1304篇
药学   3234篇
中国医学   193篇
肿瘤学   5683篇
  2023年   268篇
  2022年   565篇
  2021年   1003篇
  2020年   547篇
  2019年   753篇
  2018年   1057篇
  2017年   798篇
  2016年   1005篇
  2015年   1097篇
  2014年   1415篇
  2013年   1767篇
  2012年   2829篇
  2011年   3154篇
  2010年   1796篇
  2009年   1645篇
  2008年   2967篇
  2007年   3173篇
  2006年   3231篇
  2005年   3186篇
  2004年   3335篇
  2003年   3358篇
  2002年   3342篇
  2001年   747篇
  2000年   645篇
  1999年   769篇
  1998年   844篇
  1997年   705篇
  1996年   658篇
  1995年   557篇
  1994年   509篇
  1993年   535篇
  1992年   465篇
  1991年   443篇
  1990年   404篇
  1989年   374篇
  1988年   382篇
  1987年   282篇
  1986年   241篇
  1985年   279篇
  1984年   244篇
  1983年   188篇
  1982年   160篇
  1981年   186篇
  1980年   165篇
  1979年   148篇
  1978年   147篇
  1977年   100篇
  1976年   80篇
  1975年   84篇
  1969年   68篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Background: Electrical abnormalities in the RVOT may be involved in Brugada syndrome.
Objectives: We investigated the relationship between the signal-averaged ECG (SAECG) and electrophysiologic study (EPS), especially focusing on conduction delay in the outflow tract of the right ventricle (RVOT) and its contribution to clinical characteristics.
Methods: Twenty-four patients with Brugada syndrome (23 men and 1 woman; 61 ± 16 years old) were studied. We assessed the presence of late potential (LP) in SAECG and the filtered QRS duration in the right precordial leads (V1 or V2; RfQRS) and in the left precordial leads (V5 or V6; LfQRS) and the difference between them. In 18 patients, SAECG was evaluated for an LP on three separate occasions.
Results: SAECG was positive for LP in 15 patients at least once; and in 7 patients, SAECG was positive for an LP on multiple occasions, and 6 of 7 patients (86%) had a history of cardiac arrest. The difference between RfQRS and LfQRS was significantly greater in patients with cardiac arrest than in patients with syncope or in asymptomatic patients; 29 ± 10, 14 ± 11 (P < 0.01), and 7 ± 5 msec (P < 0.001), respectively. All patients were alive and one patient with cardiac arrest had an appropriate VF therapy delivered by the ICD.
Conclusions: The dominant prolongation of the filtered QRS duration in the right precordial leads may be related to the risk of arrhythmic event in Brugada syndrome.  相似文献   
992.
The use of bile acid dissolution therapy in extracorporeal shockwave lithotripsy of gallstones, remains controversial. Our study examined whether chemolitholysis after sufficient disintegration enhanced stone clearance within 6 months of the first lithotripsy. A total of 143 patients who developed one to three radiolucent stones measuring⪯30 mm in diameter were randomly separated into two treatment groups: 47% were given lithotripsy alone, and 53% lithotripsy plus ursodeoxycholic acid (UDCA). Repeated piezoelectric lithotripsy was given, with no limit on the total number of treatment sessions, to pulverize or disintegrate stones into fragments<3 mm. Stones were disintegrated in 97% of all patients, and the fragments were ⪯2 mm in 50% of these patients. According to an intention-to-treat analysis, 52% in the lithotripsy alone group and 58% in the UDCA group were free of stones 6 months after the first lithotripsy (P=0.61). Of the patients with fragments⪯2 mm, 71% in the former and 86% in the latter group were free of stones 6 months after the first lithotripsy, with no significant difference between the groups. Biliary pain occurred in 25% of all patients, including 3 with acute cholecystitis. We concluded that the sufficient disintegration of gallstones achieved with repeated lithotripsy enhanced the early clearance of fragments, regardless of whether chemolitholysis was employed.  相似文献   
993.
Ultrasonography should be used for screening of hepatocellular carcinoma, but there are few reports on the relationship between liver ultrasonographic findings and the development of hepatocellular carcinoma (HCC). Using prospective follow-up studies, we examined the role of liver with a hypoechoic nodular pattern as a high-risk factor in HCC. The study was performed by follow-up on 593 patients with chronic liver disease recorded at our hospital. The ultrasonographic pattern of the liver parenchyma was classified either as a small or large hypoechoic nodular pattern or as a nonnodular pattern. Patients were followed up from the time of initial ultrasonographic examination (1985–1987) until January 1, 1991. During the follow-up period (average, 4.2 years, range, 0.3–6.0 years), 62 patients were found to have HCC (12%). Patients whose livers showed small or large hypoechoic nodular pattern had a significantly higher risk of HCC than did patients whose livers showed a nonnodular pattern (rate ratios were 14.0 and 20.0, respectively, adjusted for age, sex, hepatitis virus markers, ICG R15, α-fetoprotein concentration, and ultrasonographic pattern of the liver). Liver showing a hypoechoic nodular pattern is a major risk factor in HCC.  相似文献   
994.
Changes in insulin, somatostatin, and glucagon secretion during the development of obesity in rats after ventromedial hypothalamic (VMH) lesions were evaluated by measuring fasting hormone levels and their secretion from the isolated perfused pancreas. Fasting peripheral insulin levels were not altered 1 week after the VMH lesions but became progressively elevated at 3-4, 8-9, and 11-12 weeks compared to the values in sham-operated and age-matched control rats. In the portal vein, insulin levels also progressively increased in VMH-lesioned rats, but the portal-peripheral gradient of insulin in the later phase of VMH obesity was significantly lower than in the early phase after VMH lesions. On the contrary, the arginine-induced insulin release from the perfused pancreas was highest at 1 week and gradually decreased thereafter, although it continued to remain higher than that of controls. The perfusate somatostatin response to arginine also was exaggerated in the VMH-lesioned rats. However, both the peripheral glucagon level and the glucagon secretion from the perfused pancreas of the VMH-lesioned rats were not significantly different from the controls. These results show that VMH lesions result in an increased insulin and somatostatin secretion. Using the cyclically perfused liver in situ, we have found that the hepatic extraction rate of insulin is indeed reduced in rats 8-9 weeks after VMH lesioning, and so have at least partly accounted for the decreased portal-peripheral gradient of insulin in the later VMH postoperative phase.  相似文献   
995.
RATIONALE: Adrenomedullin, a potent vasodilator peptide, regulates cell growth and survival. However, whether adrenomedullin contributes to lung regeneration remains unknown. OBJECTIVES: To investigate whether adrenomedullin influences the kinetics of bone marrow cells, and whether adrenomedullin promotes regeneration of alveoli and vasculature and thereby improves lung structure and function in elastase-induced emphysema in mice. METHODS: Adrenomedullin or vehicle was randomly administered to C57BL/6 mice for 5 days. We counted the numbers of mononuclear cells and stem cell antigen-1-positive cells in circulating blood. After intratracheal injection of elastase or saline, mice were randomized to receive continuous infusion of adrenomedullin or vehicle for 14 days. Functional and histologic analyses were performed 28 days after treatment. RESULTS: Twenty-eight days after elastase injection, destruction of the alveolar walls was observed. However, adrenomedullin infusion significantly inhibited the increase in lung volume, static lung compliance, and mean linear intercept in mice given elastase. Adrenomedullin increased the numbers of mononuclear cells and stem cell antigen-1-positive cells in circulating blood. Adrenomedullin significantly increased the number of bone marrow-derived cells incorporated into the elastase-treated lung. Some of these cells were positive for cytokeratin or von Willebrand factor. Infusion of adrenomedullin after the establishment of emphysema also had beneficial effects on lung structure and function. In vitro, addition of adrenomedullin attenuates elastase-induced cell death in alveolar epithelial cells and endothelial cells. CONCLUSIONS: Adrenomedullin improved elastase-induced emphysema at least in part through mobilization of bone marrow cells and the direct protective effects on alveolar epithelial cells and endothelial cells.  相似文献   
996.
Reticulated platelets (RP) and large platelets (LP) were measured by an automated hematology analyzer (modified R-2000) in 287 healthy volunteers and 131 patients with thrombocytopenia or thrombocytosis. RP was significantly higher in patients with idiopathic thrombocytopenic purpura (ITP), especially in active phase, while RP was markedly lower in patients with essential thrombocytosis (ET) or chronic myelocytic leukemia (CML). LP was significantly higher in patients with ITP, especially in active phase, while LP was markedly lower in patients with aplastic anemia (AA), ET, or CML. In ITP, RP and LP were significantly higher in patients positive for anti-glycoprotein (Gp) IIb/IIIa antibody. RP and LP were poorly correlated with platelet-associated IgG (PAIgG). RP and LP were poorly correlated with plasma thrombopoietin levels, and negatively correlated with platelet count. These results show that RP reflects the pathology of thrombocytopenic disorders, and that measurement of RP is useful for the differential diagnosis and analysis of platelet kinetics.  相似文献   
997.

Background

Diabetes has been reported as a comorbidity of chronic obstructive pulmonary disease (COPD) in Western countries, but it has not been demonstrated in epidemiological reports in Japan. The purpose of this study was to clarify whether the relationship between airflow obstruction and diabetes can be confirmed in a Japanese general population.

Methods

From 2004 to 2006, blood sampling and pulmonary function tests were performed on 3045 people over the age of 40 years in annual health check-ups held in Takahata, Yamagata Prefecture, Japan. Pulmonary function was re-evaluated in 2009 and 2011.

Results

The prevalence of diabetes did not differ between subjects with and without airflow obstruction. Furthermore, although body mass index decreased, no increase in the prevalence of diabetes was observed with the progression of airflow obstruction. The annual changes in forced expiration volume in 1 s (FEV1) did not differ depending on the presence or absence of diabetes in the study population.

Conclusion

There was no difference in the prevalence of diabetes between subjects with airflow obstruction and those without. As patients with COPD in Japan are thinner than in the West, diabetes may not be a common comorbidity in Japanese patients with COPD.  相似文献   
998.
It is widely accepted that laryngopharyngeal reflux requires more aggressive and prolonged therapy than gastro-esophageal reflux disease. Otolaryngologists often observe that laryngopharyngeal symptoms, such as throat clearing, hoarseness, cough, and globus pharyngeus, are slower to resolve than esophageal symptoms, such as heartburn and regurgitation. The aim of this was to provide empirical evidence to support this observation and to carry out a detailed investigation of the differences between these symptoms. Forty-five patients with laryngopharyngeal and esophageal symptoms received acid-suppression therapy that involved the continuous administration of a proton-pump inhibitor for up to 6 months. We investigated the differences in response to acid-suppression therapy between patients suffering from laryngopharyngeal and esophageal symptoms, respectively, who received upper gastrointestinal endoscopy and were assayed for serum Helicobacter pylori antibodies. The significance of the rate of symptom improvement was estimated by Kaplan-Meier analysis and the logrank test. Laryngopharyngeal symptoms improved significantly more slowly than esophageal symptoms following acid-suppression therapy (49.8 vs. 78.3%, 60 days after the start of acid suppression; P = 0.003). These differences were observed both in patients with erosive esophagitis (P = 0.008) and in H. pylori-seronegative patients (P = 0.001).  相似文献   
999.
AIM: To identify the precise location of putative tumor suppressor genes (TSGs) on the short arm of chromo- some 8 in patients with hepatocellular carcinoma (HCC). METHODS: We used 16 microsatellite markers informative in Japanese patients, which were selected from 61 pub- lished markers, on 8p, to analyze the frequency of loss of heterozygosity (LOH) in each region in 33 cases (56 lesions) of HCC. RESULTS: The frequency of LOH at 8p23.2-21 with at least one marker was 63% (20/32) in the informative cases. More specifically, the frequency of LOH at 8p23.2, 8p23.1, 8p22, and 8p21 was 6%, 52%, 47%, and 13% in HCC cases. The LOH was significantly more frequent at 8p23.1 and 8p22 than the average (52% vs 22%, P = 0.0008; and 47% vs 22%, P = 0.004, respectively) or others sites, such as 8p23.2 (52% vs 6%, P = 0.003; 47% vs 22%, P = 0.004) and 8p21 (52% vs 13%, P = 0.001; 47% vs 13%, P = 0.005) in liver cancer on the basis of cases. Notably, LOH frequency was significantly higher at D8S277, D8S503, D8S1130, D8S552, D8S254 and D8S258 than at the other sites. However, no allelic loss was detected at any marker on 8p in the lesions of nontumor liver tissues. CONCLUSION: Deletion of 8p, especially the loss of 8p23.1-22, is an important event in the initiation or promotion of HCC. Our results should be useful in identi- fying critical genes that might lie at 8p23.1-22.  相似文献   
1000.
A patient underwent radiofrequency (RF) catheter ablation for a drug-refractory ventricular tachycardia, but RF energy application at an endocardial site of the left ventricular outflow tract and at the left sinus of Valsalva could not eliminate the tachycardia. The earliest ventricular activation during the arrhythmia, which preceded the onset of the QRS complex by 32 ms, was found within the great cardiac vein and complete elimination of the tachycardia was finally achieved with RF application at that site.  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