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   2489篇
  免费   154篇
  国内免费   25篇
耳鼻咽喉   12篇
儿科学   56篇
妇产科学   13篇
基础医学   274篇
口腔科学   137篇
临床医学   164篇
内科学   861篇
皮肤病学   21篇
神经病学   89篇
特种医学   107篇
外科学   418篇
综合类   33篇
预防医学   77篇
眼科学   18篇
药学   161篇
中国医学   5篇
肿瘤学   222篇
  2023年   16篇
  2022年   45篇
  2021年   73篇
  2020年   36篇
  2019年   54篇
  2018年   55篇
  2017年   40篇
  2016年   64篇
  2015年   72篇
  2014年   89篇
  2013年   96篇
  2012年   137篇
  2011年   194篇
  2010年   89篇
  2009年   70篇
  2008年   138篇
  2007年   124篇
  2006年   171篇
  2005年   141篇
  2004年   134篇
  2003年   147篇
  2002年   129篇
  2001年   54篇
  2000年   69篇
  1999年   53篇
  1998年   45篇
  1997年   31篇
  1996年   46篇
  1995年   32篇
  1994年   16篇
  1993年   18篇
  1992年   22篇
  1991年   21篇
  1990年   16篇
  1989年   12篇
  1988年   16篇
  1987年   16篇
  1986年   3篇
  1985年   13篇
  1984年   7篇
  1983年   11篇
  1982年   5篇
  1981年   7篇
  1979年   5篇
  1978年   5篇
  1977年   6篇
  1972年   3篇
  1971年   5篇
  1970年   5篇
  1968年   3篇
排序方式: 共有2668条查询结果,搜索用时 15 毫秒
41.
The purpose of this study was to confirm that the arytenoid regions dynamically adduct and extend upward toward the epiglottis during laryngeal elevation. While 14 healthy volunteers aged 19?C32?years old swallowed 5?ml of white soft yogurt in one gulp without chewing, the movement of the arytenoid regions was observed for videoendoscopic evaluation of swallowing (VE). Each moving image was stored simultaneously on videotape. A cross-sectional area surrounded by the epiglottis and the bilateral arytenoid regions (S) and the length of a straight line passing through the anterior borders of the left and right arytenoid regions (L) were measured. The relative area of the entrance in the laryngeal vestibule was calculated as [S/L 2] before the swallowing reflex (resting condition), just before laryngeal closure, and just after laryngeal closure. [S/L 2] was smaller just before epiglottal descent than at the resting condition, and became smallest just after the epiglottis started to ascend. The mean area narrowed to 37.9% of the resting area just after laryngeal closure and in the most extreme case to 8.7% of the resting area. It was demonstrated that the arytenoid regions adducted and extended up toward the epiglottis during laryngeal elevation. The technique used to measure the cross-sectional area of the entrance in the laryngeal vestibule employing VE was an effective analytical procedure.  相似文献   
42.
A 68-year-old male presented with blurred vision in both eyes. Ophthalmoscopy revealed bilateral prominent disc swelling and vitritis. No systematic neurological symptoms were observed. Magnetic resonance imaging revealed bilateral meningeal enhancement of the optic nerve. Small cell carcinoma was found, and antibodies against collapsing response-mediating protein-5 (CRMP-5) were detected in the serum. Ophthalmological manifestations disappeared during a decrease in tumour size with treatment for the malignancy. This case report describes this rare case of anti-CRMP-5 antibody–positive paraneoplastic perioptic neuritis without neurological symptoms, showing that prompt diagnosis and timely treatment of the underlying tumour are crucial to prevent increased levels of autoantibodies and irreversible damage to the nervous system.  相似文献   
43.
44.
To evaluate the usefulness of differentiation of atypical pneumonia and bacterial pneumonia in the community-acquired pneumonia guidelines of the Japanese Respiratory Society, we investigated 124 cases of three atypical pneumonias (Mycoplasma pneumonia, 62 cases; Chlamydia pneumoniae pneumonia, 46 cases; Chlamydia psittaci pneumonia, 13 cases) and 403 cases of bacterial pneumonia at our hospital over seven years. Overall, the sensitivity and specificity of the criteria in the guideline were 70.4% and 91.8%, respectively. High accordance was recognized in patients under 60 years old with atypical pneumonia. Items in the criteria that included subjective factors were considered inassessable. We found that the differentiation of pneumonias in the guideline is useful for the diagnosis of atypical pneumonia among younger patients, but it should be concise and objective. We therefore propose that the criteria would be more effective if they consisted of only 4 items: age under 60 years, no underlying disorders, presence of stubborn dry cough, and normal peripheral white blood cell count.  相似文献   
45.
46.
Introduction: Although successful ablation of ventricular tachycardia (VT) is feasible in arrhythmogenic right ventricular cardiomyopathy (ARVC), long-term recurrence is common. The aim of this study was to assess the usefulness of a change in the isolated delayed component (IDC) as an endpoint of the catheter ablation in ARVC.
Methods and Results: Eighteen patients (48 ± 11 years) with ARVC were studied. Detailed endocardial mapping of the right ventricle (RV) was performed during sinus rhythm. IDCs were recorded in 16 patients and the latest IDCs were related to the VT circuit. Catheter ablation was carried out in the areas with the IDCs. At the end of the session, the IDC was electrically dissociated in one, disappeared in five, exhibited second-degree block in one, was significantly delayed (≥50 ms) in three, and remained unchanged in six. The change in the IDC was correlated with the change in the type II/III late potentials in the signal-averaged electrocardiography (ECG) and the inducibility of the clinical VT after the ablation. During a follow-up of 61 ± 38 months, VT recurred in six. The patients with a changed IDC had a significantly lower VT recurrence than those with no IDC or an unchanged IDC (P < 0.02).
Conclusion: In patients with ARVC, (1) the IDCs during sinus rhythm are related to the clinical VT and can be a target for the ablation, (2) a change in the IDC can be used as an endpoint, and (3) qualitative analyses of the serial signal-averaged ECGs may be useful for the long-term follow-up.  相似文献   
47.
Polynucleotides are anionic macromolecules which are expected to transfer into the targeted cells through specific uptake mechanisms. So, we developed polynucleotides coating complexes of plasmid DNA (pDNA) and polyethylenimine (PEI) for a secure and efficient gene delivery system and evaluated their usefulness. Polyadenylic acid (polyA), polyuridylic acid (polyU), polycytidylic acid (polyC), and polyguanylic acid (polyG) were examined as the coating materials. pDNA/PEI/polyA, pDNA/PEI/polyU, and pDNA/PEI/polyC complexes formed nanoparticles with a negative surface charge although pDNA/PEI/polyG was aggregated. The pDNA/PEI/polyC complex showed high transgene efficiency in B16-F10 cells although there was little efficiency in pDNA/PEI/polyA and pDNA/PEI/polyU complexes. An inhibition study strongly indicated the specific uptake mechanism of pDNA/PEI/polyC complex. Polynucleotide coating complexes had lower cytotoxicity than pDNA/PEI complex. The pDNA/PEI/polyC complex showed high gene expression selectively in the spleen after intravenous injection into mice. The pDNA/PEI/polyC complex showed no agglutination with erythrocytes and no acute toxicity although these were observed in pDNA/PEI complex. Thus, we developed polynucleotide coating complexes as novel vectors for clinical gene therapy, and the pDNA/PEI/polyC complex as a useful candidate for a gene delivery system.  相似文献   
48.
Objective: To investigate the potential beneficial effects of guideline-based pharmacological therapy on pulmonary function and quality of life (QOL) in Japanese chronic obstructive pulmonary disease (COPD) patients without prior treatment.

Research design and methods: Multicenter survey, open-label study of 49 Japanese COPD patients aged ≥ 40 years; outpatients with >10 pack years of smoking history; ratio of forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) < 70%; predicted FEV1 < 80%; treated with bronchodilators and/or inhaled corticosteroids as maintenance therapy until week 48.

Main outcome measures: The primary endpoint was change in pulmonary function (trough FEV1, trough FVC); secondary endpoints were QOL and physical activity at 48 weeks after initiation of therapy.

Results: Airway reversibility was confirmed in untreated patients. Significant changes over time were not observed for FEV1 and FVC, indicating lung function at initiation of treatment was maintained during the observation period. COPD assessment test scores showed statistical and clinical improvements. Cough, sputum, breathlessness, and shortness of breath were significantly improved.

Conclusions: Lung function and QOL of untreated Japanese COPD patients improved and improvements were maintained by performing a therapeutic intervention that conformed to published guidelines.  相似文献   

49.
BACKGROUND AND AIMS: The acute administration of low-dose ethanol was demonstrated to attenuate liver injury elicited by gut ischemia/reperfusion (I/R). Nitric oxide (NO) has been found to be a modulator of adhesive interactions between leukocytes, platelets, and endothelial cells, but there has been much controversy about the effects of ethanol on NO regulation. The objective of this study was to investigate the role of NO in ethanol-reduced hepatic microvascular dysfunction elicited by gut I/R. METHODS: Male Wistar rats were exposed to 30 min of gut ischemia followed by 60 min of reperfusion. Intravital microscopy was used to monitor leukocyte recruitment and non-perfused sinusoids (NPS). Plasma alanine aminotransferase (ALT) activities were measured 6 h after the onset of reperfusion. In another set of experiments, ethanol (10%, 1 g/kg) was administered before ischemia. RESULTS: Gut I/R elicited increases in the number of stationary leukocytes, NPS, and plasma ALT activities; all of which were attenuated by pretreatment with ethanol or an NO donor. Gut I/R caused the apoptosis of hepatocytes, which was prevented by pretreatment with ethanol. Pretreatment with an NO synthase inhibitor diminished the protective effects of ethanol. The administration of ethanol increased plasma nitrite/nitrate levels. CONCLUSION: These results suggest that low-dose ethanol attenuates the gut I/R-induced hepatic microvascular dysfunction and sequential liver injury by increasing sinusoidal NO levels.  相似文献   
50.
Polythiophenes bearing a bornyl group as a side chain are synthesized. The polymers, which consist of multiple thiophenes and a substituted aromatic ring in the repeat unit, demonstrate right‐handed helicity in the film state. Results of energy level measurements show good agreement with the density functional theory calculation results for the model compounds. In situ electron spin resonance (ESR) studies indicate that increasing the number of unsubstituted thiophene units in the repeat unit increases susceptibility for the dopants. The chiral charge carriers are confirmed with ESR and circular dichroism spectroscopy measurements.

  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