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   2045篇
  免费   120篇
  国内免费   13篇
耳鼻咽喉   12篇
儿科学   51篇
妇产科学   43篇
基础医学   359篇
口腔科学   27篇
临床医学   178篇
内科学   495篇
皮肤病学   63篇
神经病学   217篇
特种医学   30篇
外科学   105篇
综合类   33篇
一般理论   1篇
预防医学   199篇
眼科学   64篇
药学   152篇
中国医学   6篇
肿瘤学   143篇
  2024年   6篇
  2023年   22篇
  2022年   65篇
  2021年   105篇
  2020年   58篇
  2019年   81篇
  2018年   81篇
  2017年   47篇
  2016年   67篇
  2015年   80篇
  2014年   112篇
  2013年   127篇
  2012年   173篇
  2011年   163篇
  2010年   94篇
  2009年   62篇
  2008年   136篇
  2007年   121篇
  2006年   122篇
  2005年   97篇
  2004年   74篇
  2003年   87篇
  2002年   80篇
  2001年   14篇
  2000年   9篇
  1999年   2篇
  1998年   5篇
  1997年   8篇
  1996年   8篇
  1995年   11篇
  1994年   5篇
  1993年   4篇
  1992年   5篇
  1991年   3篇
  1990年   5篇
  1988年   3篇
  1986年   5篇
  1985年   2篇
  1982年   4篇
  1981年   3篇
  1978年   3篇
  1977年   1篇
  1976年   3篇
  1974年   2篇
  1973年   2篇
  1972年   1篇
  1969年   1篇
  1968年   3篇
  1966年   1篇
  1962年   1篇
排序方式: 共有2178条查询结果,搜索用时 15 毫秒
31.
Pretreatment with clopidogrel before elective primary percutaneous coronary intervention (PCI) has been shown to reduce ischemic complications. There are limited data about the value of clopidogrel pretreatment in the setting of PCI for ST-elevation myocardial infarction (STEMI). We aimed to examine the effect of clopidogrel preloading on angiographic and clinical outcomes in patients with STEMI who were treated with PCI. We conducted a prospective registry of all patients treated with primary PCI for STEMI from March 2003 to June 2006. Excluded were patients with cardiogenic shock. For the current analysis, patients (n = 292) were allocated into 2 groups. One group received clopidogrel loading dose before PCI (in the emergency department or coronary care unit, n = 165); the other,immediately after PCI (n = 127). TIMI myocardial perfusion (TMP) grade at the end of PCI and 30-day and 6-month clinical outcomes were assessed. Clinical characteristics were similar among the groups. However, patients pretreated with clopidogrel were more likely to receive aspirin and beta blockers before the current admission. TMP grade 3 occurred in a higher proportion of patients in the clopidogrel pretreatment group than in the no-pretreatment group (85% vs 71%, p = 0.01). Multivariate logistic regression analysis showed that clopidogrel pretreatment was associated with an odds ratio of 2.2 for TMP grade 3 (1.2 to 3.9, p = 0.01). Furthermore, the incidence of reinfarction at 30 days was lower in the pretreatment group (0% vs 3.2%, respectively, p = 0.04). In conclusion, these findings support the early use of clopidogrel in patients with STEMI who are treated with primary PCI.  相似文献   
32.
33.
34.
35.
BACKGROUND: The upper normal limit (ULN) of serum alanine-aminotrasferase (ALT) normal range was recently challenged, because patients diagnosed with liver diseases may have 'normal' or near-'normal' ALT levels, and because possible modulators are often ignored in determining normal range. AIM: To estimate the ULN for serum ALT and to identify factors modulating it. SUBJECTS AND METHODS: We reviewed medical records of subjects aged 15-90, who underwent standard panels of laboratory tests, including serum ALT, over 6 months at a central laboratory. Three groups were defined: Group 1, comprised total study population (N=272 273). Group 2 (N=87 020) comprised total study population, excluding those receiving potentially hepatotoxic drugs, or diagnosed with liver disease, or had any abnormal laboratory test results other than for triglycerides, cholesterol, glucose, or HbA1c. Group 3 (N=17 496) the 'healthy' population, from whose ALT values we established the new ULN, comprised Group 2 subjects with normal triglycerides, cholesterol, glucose, and HbA1c levels. RESULTS: The 95th percentile ALT values, corresponding to the ULN, in groups 1, 2, and 3 were 50.1, 40, and 37.5 U/l, respectively. 6.2% (16 943/273 273) of subjects whose ALT was below ULN listed by the test manufacturer (52 U/l), had ALT level above our new ULN. Linear and logistic-regression analyses showed that ALT levels were significantly modified by gender, age, glucose, cholesterol, triglycerides, and overweight/obesity diagnosis. Significant interaction was found between gender, glucose and cholesterol levels. CONCLUSIONS: In this first large-scale study of 'healthy' population, serum ALT ULN was far lower than currently accepted value. Age and gender may be considered when determining the ULN for ALT.  相似文献   
36.
37.
The present study characterized changes in key parameters of reproduction in adult roach (Rutilus rutilus) from Lake Grosser Mueggelsee (Berlin, Germany) during natural gametogenesis. Fish of both sexes were sampled in monthly intervals between April and August in order to cover the onset of gametogenesis. Investigated parameters included gonad histology, plasma levels of 17β-oestradiol (E2), testosterone (T), 11-ketotestosterone (11-KT), and 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) as well as the expression of gonadotropin subunits in the pituitary. Furthermore, the mRNA-expression of brain-type aromatase (cyp19a1b), androgen receptor (ar), and estrogen receptor isoforms was studied at the pituitary level. The onset of gametogenesis - as indicated by follicles with cortical alveoli in females and first spermatogonia B in males - was observed in July, accompanied by a significant up-regulation of follicle-stimulating hormone β (fshβ) mRNA in the pituitary in both sexes. On the other hand, luteinizing hormone β (lhβ) mRNA increased later on in August. In males, the increase of fshβ mRNA in July coincided with a rise in plasma 11-KT concentrations. In females, E2 in plasma increased later, not until August, shortly before true vitellogenesis (late cortical alveoli stage). Expression of sex steroid receptors in the pituitary revealed only minor seasonal fluctuations. Most pronounced, ar mRNA displayed the highest level pre-spawning in both sexes. Interestingly, cyp19a1b mRNA-expression in the pituitary increased in parallel with fshβ already before any changes in plasma E2 or T occurred. These data suggest an important role of pituitary FSH and aromatase at the onset of gametogenesis in the roach.  相似文献   
38.
39.
The temporal scale of neuroplasticity following acute alterations in brain structure due to neurosurgical intervention is still under debate. We conducted a longitudinal study with the objective of investigating the postoperative changes in a patient who underwent cerebrovascular surgery and who subsequently lost proprioception in the fingers of her right hand. The results show increased activation in contralesional somatosensory areas, additional recruitment of premotor and posterior parietal areas, and changes in functional connectivity with left postcentral gyrus. These findings demonstrate long-term modifications of cortical organization and as such have important implications for treatment strategies for patients with brain injury.  相似文献   
40.
The aim of this study was to investigate the correlation between dental anxiety, salivary cortisol, and salivary alpha amylase (sAA) levels. Furthermore, the aim was to look into individual differences such as age, race, gender, any existing pain, or traumatic dental experience and their effect on dental anxiety. This study followed a cross-sectional design and included a convenience sample of 46. Every patient was asked to complete the Dental Anxiety Scale (DAS) and a basic demographic/dental history questionnaire. A saliva sample, utilizing the method of passive drooling, was then collected in 2-mL cryovials. Samples were analyzed for salivary cortisol and sAA levels by Salimetrics. Significant associations were observed between DAS scores and presence of pain and history of traumatic dental experience. However, no significant correlations were observed between DAS, cortisol, and sAA levels. Our study reconfirms that dental anxiety is associated with presence of pain and a history of traumatic dental experience. On the other hand, our study was the first to our knowledge to test the correlation between the DAS and sAA; nevertheless, our results failed to show any significant correlation between dental anxiety, cortisol, and sAA levels.Key Words: Stress, Dental anxiety, Salivary cortisol, Salivary alpha amylase, Dental Anxiety ScaleDental anxiety is a very common phenomenon and remains an obstacle for many patients to seeking proper dental care despite all the technological advances in dentistry. Multiple etiologies have been proposed in the past. Thomson et al1 suggested that even though endogenous factors (personality traits) play a role in its development, it develops mainly from exogenous (conditioning) factors. Van Wijk and Hoogstraten2 revealed that a single early traumatic experience can be the main cause of dental anxiety. Oosterink et al3 showed that a previous traumatic experience may involve pain, negative dentist remarks (NDR), and strong negative emotional responses. As a consequence, these variables act as predictors for cancelled/missed appointments, a decrease in pain threshold with increase in patient discomfort, poor compliance, increased number of emergency appointments, jeopardized patient/dentist relationship, high Decayed Missing and Filled Teeth (DMFT) index, poor oral health perception, decreased self-esteem, and decreased oral health–related quality of life.411 Women were found to be more affected than men, and there is a tendency for the younger age groups to have more anxiety.12Dental anxiety was found to have a direct relationship with pain perception.13 Rhudy and Meagher14 suggested that the pain reactivity is modulated by emotional stress. In addition, Loggia et al15 revealed changes in pain pathways on neuroimaging techniques with a negative emotional state. Furthermore, Klages et al16 revealed that anxiety increases expected or experienced pain where patients with higher anxiety levels predicted a higher pain experience.Anxiety is regarded as a form of stress and, thus, has a physiological impact on the body. Stressors can cause the activation of the autonomic nervous system (ANS), which prepares the body for the fight-or-flight reaction, and the hypothalamic-pituitary-adrenal (HPA) axis.When the autonomic nervous system (ANS) gets activated, it causes the release of epinephrine and norepinephrine from the adrenal medulla.17 Norepinephrine was shown to increase the secretion of salivary alpha amylase (sAA) from the acinar cells of the parotid and submandibular salivary glands.18 It was suggested that the level of alpha amylase in the saliva reflects the autonomic nervous system (ANS) activity and that measuring it presents an easy, noninvasive measure of ANS activity compared to measuring the actual catecholamines in serum.18 sAA levels were shown to increase in response to various stressors like exercise, cold exposure, and hypertension, in addition to psychological stress.18 Nator et al19 also demonstrated that sAA has a definite circadian rhythm wherein its levels fluctuate during the day in a definite pattern. Because the ANS is considered a rapid response, it was suggested that it may be a better measure of stress compared to measuring the hypothalamic-pituitary-adrenal axis response.1720Upon activation of the hypothalamic-pituitary-adrenal axis, cortisol gets secreted from the adrenal cortex to all body fluids, including saliva. It was demonstrated in the past that salivary cortisol increases in response to stress and anxiety, and that it also presents an easy, noninvasive way of measuring stress.20 Cortisol levels in the saliva have been shown to be higher in patients with oral lichen planus.21 In addition, they were higher in patients undergoing wisdom teeth extractions and prior to urgent dental care.22 Similar to alpha amylase, cortisol has a definite circadian rhythm.The Dental Anxiety Scale (DAS), devised by Norman Corah in 1969, is the most commonly used scale to measure dental anxiety.23 It was found to have high validity and is easy to administer; therefore, it was adopted as a measure of dental anxiety in this study.Stress and sAA associations have been well documented and studied in the literature2428; however, to our knowledge, no literature exists on the correlation between dental anxiety and sAA. Therefore, the aim of this study was to see if there is any correlation between dental anxiety, sAA, and salivary cortisol levels. In addition, the aim was to see if individual variations such as age, gender, race, presence of pain, or history of traumatic dental experience exhibit associations with dental anxiety. We hypothesized that dental anxiety is correlated with an increase in both alpha amylase and cortisol levels; furthermore, that presence of pain and a history of traumatic dental experience are associated with higher dental anxiety levels.  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