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   7380篇
  免费   476篇
  国内免费   65篇
耳鼻咽喉   47篇
儿科学   172篇
妇产科学   213篇
基础医学   1108篇
口腔科学   78篇
临床医学   590篇
内科学   1962篇
皮肤病学   278篇
神经病学   659篇
特种医学   259篇
外科学   577篇
综合类   16篇
预防医学   465篇
眼科学   78篇
药学   604篇
中国医学   14篇
肿瘤学   801篇
  2024年   7篇
  2023年   59篇
  2022年   156篇
  2021年   254篇
  2020年   144篇
  2019年   191篇
  2018年   186篇
  2017年   164篇
  2016年   216篇
  2015年   267篇
  2014年   286篇
  2013年   376篇
  2012年   596篇
  2011年   629篇
  2010年   306篇
  2009年   299篇
  2008年   501篇
  2007年   472篇
  2006年   489篇
  2005年   506篇
  2004年   440篇
  2003年   408篇
  2002年   328篇
  2001年   59篇
  2000年   45篇
  1999年   68篇
  1998年   74篇
  1997年   51篇
  1996年   49篇
  1995年   34篇
  1994年   29篇
  1993年   25篇
  1992年   20篇
  1991年   19篇
  1990年   20篇
  1989年   22篇
  1988年   15篇
  1987年   9篇
  1986年   12篇
  1985年   14篇
  1984年   4篇
  1983年   9篇
  1982年   4篇
  1980年   5篇
  1979年   9篇
  1978年   7篇
  1977年   4篇
  1975年   4篇
  1969年   5篇
  1966年   6篇
排序方式: 共有7921条查询结果,搜索用时 327 毫秒
61.
BACKGROUND: It is recognized that airway inflammation has a central role in the pathogenesis of asthma, but how it relates to exercise-induced bronchoconstriction (EIB) is not completely understood. OBJECTIVE: The aim of our study was to investigate the relationship between EIB and baseline concentrations of cysteinyl leukotrienes (Cys-LTs) and other inflammatory markers in exhaled breath condensate (EBC). METHODS: EBC was collected, and the fraction of exhaled nitric oxide (FE NO ) was measured in a group of 19 asthmatic children, after which they performed a treadmill exercise test. Fourteen healthy children were enrolled as control subjects. RESULTS: The asthmatic children were divided into the EIB group (decrease in FEV 1 , > or =12%) and the non-EIB group. The EBC was analyzed for the presence of Cys-LTs, leukotriene B 4 , and ammonia. Asthmatic patients with EIB (mean FEV 1 decrease, 23% +/- 3%) had higher Cys-LT concentrations than either asthmatic patients without EIB or control subjects (42.2 pg/mL [median] vs 11.7 pg/mL and 5.8 pg/mL; P < .05 and P < .001, respectively). Ammonia concentrations were lower in both the EIB and non-EIB groups than in control subjects (253.2 microM and 334.6 microM vs 798.4 microM; P < .01 and P < .05, respectively). No difference in EBC leukotriene B 4 levels was found among the 3 groups. Both asthmatic groups had higher FE NO levels than control subjects ( P < .001). EBC Cys-LT ( P < .01; r = 0.7) and FE NO ( P < .05; r = 0.5) values both correlated significantly with the postexercise FEV 1 decrease. CONCLUSION: this study shows that EBC Cys-LT values are higher in asthmatic children with EIB and correlate with the decrease in FEV 1 after exercise. These findings suggest that the pathways of both Cys-LT and nitric oxide are involved in the pathogenesis of EIB.  相似文献   
62.
The proposed strap-down integration method exploits the cyclical nature of human gait: during the gait swing phase, the quaternion-based attitude representation is integrated using a gyroscope from initial conditions that are determined during stance by an accelerometer. Positioning requires double time integration of the gravity-compensated accelerometer signals during swing. An interpolation technique applied to attitude quaternions was developed to improve the accuracy of orientation and positioning estimates by accounting for the effect of sensor bias and scale factor drifts. A simulation environment was developed for the analysis and testing of the proposed algorithm on a synthetic movement trajectory. The aim was to define the true attitude and positioning used in the computation of estimation errors. By thermal modelling, the changes of bias and scale factor of the inertial sensors, calibrated at a single reference temperature, were analysed over a range of ±10°C, for measurement noise standard deviations up to σg = 2.5° s−1 (gyroscope) and σa = 0.05 m s−1 (accelerometer). The compensation technique reduced the maximum root mean square errors (RMSEs) to: RMSEθ=14.6° (orientation) and RMSEd=17.7 cm (positioning) for an integration interval of one gait cycle (an improvement of 3° and 7 cm); RMSEθ=14.8° and RMSEd=30.0 cm for an integration interval of two gait cycles (an improvement of 11° and 262 cm).  相似文献   
63.
In this study we examined the ability of Salmonella enterica serovar Typhimurium porins to activate activating protein 1 (AP-1) and nuclear factor kappaB (NF-kappaB) through the mitogen-activated protein kinase (MAPK) cascade, and we identified the AP-1-induced protein subunits. Our results demonstrate that these enzymes may participate in cell signaling pathways leading to AP-1 and NF-kappaB activation following porin stimulation of cells. Raf-1 was phosphorylated in response to the treatment of U937 cells with porins; moreover, the porin-mediated increase in Raf-1 phosphorylation is accompanied by the phosphorylation of MAPK kinase 1/2 (MEK1/2), p38, extracellular-signal-regulated kinase 1/2, and c-Jun N-terminal kinase. We used three different inhibitors of phosphorylation pathways: 2'-amino-3'-methoxyflavone (PD-098059), a selective inhibitor of MEK1 activator and the MAPK cascade; 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole (SB203580), a specific inhibitor of the p38 pathway; and 7beta-acetoxy-1alpha,6beta,9alpha-trihydroxy-8,13-epoxy-labd-14-en-11-one (forskolin), an inhibitor at the level of Raf-1 kinase. PD-098059 pretreatment of cells decreases AP-1 and NF-kappaB activation by lipopolysaccharide (LPS) but not by porins, and SB203580 pretreatment of cells decreases mainly AP-1 and NF-kappaB activation by porins; in contrast, forskolin pretreatment of cells does not affect AP-1 and NF-kappaB activation following either porin or LPS stimulation. Our data suggest that the p38 signaling pathway mainly regulates AP-1 and NF-kappaB activation in cells treated with S. enterica serovar Typhimurium porins. Antibody electrophoretic mobility shift assays showed that JunD and c-Fos binding is found in cells treated with porins, in cells treated with LPS, and in unstimulated cells. However, by 30 to 60 min of stimulation, a different complex including c-Jun appears in cells treated with porins or LPS, while the Fra-2 subunit is present only after porin stimulation. These data suggest different molecular mechanisms of activation induced by porins or by LPS.  相似文献   
64.
Oncogene alterations have been clearly demonstrated to be related to the carcinogenesis and progression of oral squamous cell carcinoma (OSCC). However, the analysis of these alterations for screening and early diagnostic purposes generally requires invasive techniques for surgical removal of pathological epithelium. The aim of the present study was to assess the feasibility of fluorescence in situ hybridization (FISH) analysis of HER-2/neu amplification in oral mucosa brushings and to compare the HER-2/neu status with the history and smoking and drinking habits of healthy subjects. Cells obtained by centrifugation of oral brushings from 21 subjects (overall no. of cells: 5125) were suspended in physiological saline and fixed onto two slides for cytological evaluation and FISH analysis (dual-target, dual-color fluorescence assay) of the HER-2/neu gene and CEP17 centromere. A mean of 89.8% of the cells showed two HER-2/neu signals and a mean of 94% had two CEP17 signals at fluorescent microscopy. Finally, a mean of 96% of cells with HER-2/neu / CEP17 had a ratio equal to 1. No association between smoking and drinking habits, age and the HER-2/neu and CEP17 characteristics evaluated by FISH was found.  相似文献   
65.
Alport syndrome (AS) is caused by mutations in collagen IV, which is widespread in the basement membranes of many organs, including the kidneys, eyes, and ears. Whereas the effects of collagen IV changes in the cochlea are well known, no changes have been described in the posterior labyrinth. The aim of this study was to investigate both the auditory and the vestibular function of a group of individuals with AS. Seventeen patients, aged 9–52, underwent audiological tests including pure‐tone and speech audiometry, immittance test and otoacoustic emissions and vestibular tests including video head impulse test, rotatory test, and vestibular evoked myogenic potentials. Hearing loss affected 25% of the males and 27.3% of the females with X‐linked AS. It was sensorineural with a cochlear localization and a variable severity. 50% of the males and 45.4% of the females had a hearing impairment in the high‐frequency range. Otoacoustic emissions were absent in about one‐third of the individuals. A peripheral vestibular dysfunction was present in 75% of the males and 45.4% of the females, with no complaints of vertigo or dizziness. The vestibular impairment was compensated and the vestibulo‐ocular reflex asymmetry was more evident in rotatory tests carried out at lower than higher speeds; a vestibular hypofunction was present in all hearing impaired ears although it was also found in subjects with normal hearing. A posterior labyrinth injury should be hypothesized in AS even when the patient does not manifest hearing disorders or evident signs of renal failure.  相似文献   
66.
BACKGROUND: Growing evidence documents the frequent co-morbidity between Obsessive Compulsive Disorder (OCD) and Bipolar Disorder (BP) in adults. The aim of the present study is to explore some clinical aspects of this interface in children and adolescents, as it appears in a setting of routine clinical practice. METHOD: The sample comprised 102 consecutively referred children and adolescents, both inpatients and outpatients, with BP, OCD or co-morbid BP-OCD during a 3-year period. The mean age was 14.2 (SD=3.2); 65 (63.7%) were males. Diagnoses and clinical features were collected by means of structured interview according to DSM-IV (DICA-R) and a rating scale for OCD (CY-BOCS). Clinical outcome was evaluated prospectively by means of clinical global impression (CGI) as part of routine clinical care, throughout the follow-up. RESULTS: Thirty-seven (36.3%) patients (21 males and 16 females) were diagnosed as BP, 35 (34.3%) patients (26 males and 9 females) were diagnosed as OCD and 30 (29.4%) patients (18 males and 12 females) were diagnosed as BP-OCD. BP II, was more frequent in the BP-OCD than in BP. When OCD was co-morbid with BP, age of onset was significantly earlier than in the 'pure' OCD patients. On the contrary, age of onset of BP was not affected by co-morbid OCD. According to CGI baseline scores, OCD patients were significantly less impaired than BP-OCD and BP patients, while the severity of the symptomatology was similar in the last two groups. Severity scores at the end of the follow-up were significantly higher in BP-OCD patients than in OCD patients. Patients with pure BP showed lower rates of panic disorder-agoraphobia than BP-OCD patients and higher rates of ADHD-conduct disorder. Pure OCD patients showed lower rates of ADHD and higher rates of Generalized Anxiety Disorder. The number of obsessions did not differentiate the two groups, whereas pure OCD patients showed significantly more compulsions. 'Other' obsessions-e.g., existential, philosophical, odd and/or superstitious-were significantly more frequent in BP-OCD than in pure OCD patients. Ordering compulsions were significantly more frequent in pure OCD patients. LIMITATIONS: Possible low reliability of children's and their parents' recall of past episodes of mental disorder. CONCLUSIONS: In a tertiary care center, co-morbidity between OCD and BP is a significant clinical problem affecting a large number of patients. The correct identification of OCD-bipolar co-morbidity has relevant clinical implications as far as other concomitant disorders, symptomatological features, course, complications, and treatment management and outcome are concerned.  相似文献   
67.
Kava-Kava administration reduces anxiety in perimenopausal women   总被引:1,自引:0,他引:1  
OBJECTIVE: Disturbances of mood, such as anxiety and depression, increase in the perimenopausal period. Hormone replacement therapy or neuroactive drugs represent useful treatments for these disturbances but may be contraindicated or not accepted. Herein it was investigated the efficacy of Kava-Kava, an extract of Piper Methysticum, on mood of perimenopausal women. DESIGN: A 3-months randomized prospective open study investigating in perimenopausal women modifications induced by calcium supplementation (control; n=34), calcium plus Kava-Kava at the dose of 100 mg/day (n=15) or calcium plus Kava-Kava at the dose 200 mg/day (n=19). Anxiety was evaluated by the State Trait Anxiety Inventory (STAI); depression by the Zung's scale (SDS), and climacteric symptoms by the Greene's scale. Evaluations were performed at baseline and after 1 and 3 months. RESULTS: In the control group during the 3 months, anxiety, depression and climacteric symptoms tended to decline, but not significantly. During Kava-Kava anxiety declined (P<0.001) at 1 (-3.8+/-1.03) and 3 (-5.03+/-1.2) months, depression declined at 3 months (-5.03+/-1.4; P<0.002) and climacteric score declined (P<0.0006) at 1 (-2.87+/-1.5) and 3 (-5.38+/-1.3) months. Only the decline of anxiety induced by Kava-Kava was significantly greater than that spontaneously occurring in controls (P<0.009). CONCLUSIONS: The present data indicate that, in perimenopausal women, administration of Kava-Kava induces an improvement of mood, particularly of anxiety.  相似文献   
68.
Severe obesity is associated with an increased risk of admission to intensive care units and need for invasive mechanical ventilation in patients with COVID-19. The association of obesity and COVID-19 prognosis may be related to many different factors, such as chronic systemic inflammation, the predisposition to severe respiratory conditions and viral infections. The ketogenic diet is an approach that can be extremely effective in reducing body weight and visceral fat in the short term, preserving the lean mass and reducing systemic inflammation. Therefore, it is a precious preventive measure for severely obese people and may be considered as an adjuvant therapy for patients with respiratory compromise.  相似文献   
69.
Neurosurgical Review - Treatment options for hydrocephalus include endoscopic third ventriculostomy (ETV) and ventriculoperitoneal shunt (VPS). Some ambiguity remains regarding indications, safety,...  相似文献   
70.
The determinants of the susceptibility to severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection and severe coronavirus disease 2019 (COVID-19) manifestations are yet not fully understood. Amino-bisphosphonates (N-BPs) have anti-inflammatory properties and have been shown to reduce the incidence of lower respiratory infections, cardiovascular events, and cancer. We conducted a population-based retrospective observational cohort study with the primary objective of determining if oral N-BPs treatment can play a role in the susceptibility to development of severe COVID-19. Administrative International Classification of Diseases, Ninth Revision, Clinical ModificationI (ICD-9-CM) and anatomical-therapeutic chemical (ATC) code data, representative of Italian population (9% sample of the overall population), were analyzed. Oral N-BPs (mainly alendronate and risedronate) were included in the analysis, zoledronic acid was excluded because of the low number of patients at risk. Incidence of COVID-19 hospitalization was 12.32 (95% confidence interval [CI], 9.61–15.04) and 11.55 (95% CI, 8.91–14.20), of intensive care unit (ICU) utilization because of COVID-19 was 1.25 (95% CI, 0.38–2.11) and 1.42 (95% CI, 0.49–2.36), and of all-cause death was 4.06 (95% CI, 2.50–5.61) and 3.96 (95% CI, 2.41–5.51) for oral N-BPs users and nonusers, respectively. Sensitivity analyses that excluded patients with prevalent vertebral or hip fragility fractures and without concomitant glucocorticoid treatment yielded similar results. In conclusion, we found that the incidence of COVID-19 hospitalization, intensive care unit (ICU) utilization, and COVID-19 potentially related mortality were similar in N-BPs–treated and nontreated subjects. Similar results were found in N-BPs versus other anti-osteoporotic drugs. We provide real-life data on the safety of oral N-BPs in terms of severe COVID-19 risk on a population-based cohort. Our results do not support the hypothesis that oral N-BPs can prevent COVID-19 infection and/or severe COVID-19; however, they do not seem to increase the risk. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).  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