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   9482篇
  免费   600篇
  国内免费   48篇
耳鼻咽喉   62篇
儿科学   313篇
妇产科学   322篇
基础医学   1410篇
口腔科学   121篇
临床医学   931篇
内科学   2167篇
皮肤病学   204篇
神经病学   895篇
特种医学   127篇
外科学   822篇
综合类   69篇
一般理论   8篇
预防医学   1119篇
眼科学   274篇
药学   670篇
中国医学   39篇
肿瘤学   577篇
  2024年   7篇
  2023年   70篇
  2022年   200篇
  2021年   356篇
  2020年   206篇
  2019年   286篇
  2018年   305篇
  2017年   229篇
  2016年   243篇
  2015年   322篇
  2014年   418篇
  2013年   507篇
  2012年   817篇
  2011年   855篇
  2010年   488篇
  2009年   401篇
  2008年   685篇
  2007年   696篇
  2006年   634篇
  2005年   565篇
  2004年   466篇
  2003年   429篇
  2002年   430篇
  2001年   60篇
  2000年   27篇
  1999年   50篇
  1998年   55篇
  1997年   34篇
  1996年   26篇
  1995年   31篇
  1994年   19篇
  1993年   26篇
  1992年   19篇
  1991年   18篇
  1990年   16篇
  1989年   13篇
  1988年   8篇
  1987年   13篇
  1986年   7篇
  1985年   5篇
  1984年   7篇
  1983年   7篇
  1982年   9篇
  1981年   12篇
  1980年   5篇
  1978年   5篇
  1977年   7篇
  1973年   7篇
  1972年   6篇
  1960年   3篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
A good night's sleep is often more elusive as we age, because the prevalence of insomnia in older people is high. Insufficient sleep can have important effects on daytime function by increasing the need to nap, reducing cognitive ability including attention and memory, slowing response time, adversely affecting relationships with friends and family, and contributing to a general sense of being unwell. However, rather than aging per se, circadian rhythm shifts, primary sleep disorders, comorbid medical/psychiatric illnesses, and medication use cause sleep difficulties in older people, which psychosocial factors may also affect. Clinicians should ask elderly patients about satisfaction with sleep. Any sleep complaints warrant careful evaluation of contributing factors and appropriate treatment.  相似文献   
102.
STUDY QUESTION: What is the prevalence of respiratory symptoms and obstructive pulmonary disease by age, sex, and smoking history in a population aged 70 years and older? What is the association between selected comorbidities and obstructive pulmonary disease? PATIENTS AND METHODS: A questionnaire on respiratory symptoms and disease, selected comorbidities, and smoking history was mailed to a cross-sectional, sex- and age-stratified, random sample of the population 70 years and older of Bergen, Norway. RESULTS: About 11% of these elderly persons reported having at least one current obstructive pulmonary disease, 8% reported daily wheezing, and 12% reported significant dyspnea. The only respiratory symptom or disorder to show any clear age-related pattern was dyspnea, which increased through age 89 before declining. Dyspnea, current asthma, and current chronic bronchitis were about half as likely in males as females, after adjusting for smoking pack-years. Persons with obstructive pulmonary disease reported problems with walking, heart disease, and muscle/joint disease more frequently than those without. CONCLUSIONS: The prevalence of respiratory symptoms and obstructive pulmonary disease has been estimated. Only dyspnea was associated with age in this elderly population. Female sex was a predictor of dyspnea, current asthma, and current chronic bronchitis.  相似文献   
103.
BACKGROUND: This study evaluated the efficacy of bupropion for relapse prevention in smokers with and without a past history of major depressive disorder. Changes in depressive symptoms were also examined. DESIGN: Data were gathered prospectively from a randomized, double-blind relapse prevention trial of bupropion conducted at five study sites. A total of 784 smokers (54% female, 97% white) were enrolled. Using the Structured Clinical Interview for Depression, 17% of the subjects reported a past history of major depressive disorder at baseline. All subjects received open-label bupropion SR (300 mg/d) for 7 weeks. Subjects abstinent from smoking at the end of 7 weeks (N = 429) were randomized to bupropion SR (300 mg/d) or placebo for the remainder of the year and followed for 1 year off medication. The primary outcome measures were median time to relapse to smoking and the 7-day point-prevalence smoking abstinence rate. Self-reported abstinence from smoking was verified by expired air carbon monoxide. The Beck Depression Inventory was used to assess depressive symptoms at baseline and at weeks 8 and 12. RESULTS: Median time to relapse did not differ by past history of major depressive disorder. Bupropion was associated with higher point-prevalence smoking abstinence at the end of medication compared to placebo (P = .007), independent of a past history of major depressive disorder. Moreover, change in depressive symptoms during the double-blind phase did not differ for those with and without a past history of major depressive disorder. CONCLUSIONS: Extended use of bupropion for relapse prevention is effective for smokers with and without a history of major depression.  相似文献   
104.
Limited information is available on the efficacy of cryoablation in the coronary venous system in humans. A patient with a lateral accessory pathway was referred to our center after several unsuccessful endocardial and epicardial (within the coronary sinus) attempts using standard radiofrequency energy. Ablation was subsequently performed successfully by applying cryoenergy distally into the coronary sinus, using a temperature of -50 degrees C and a freezing application time of 45 s. There were no complications. Angiography of the left coronary circumflex artery and coronary venous system was performed at 12 months follow-up using cardiac multislice computed tomography, and no coronary stenosis or anatomic anomaly was found. Neither pre-excitation or any arrhythmia recurred during follow-up. This experience suggests that ablating in the distal coronary sinus can be safely performed using cryoenergy.  相似文献   
105.
Streptococcus agalactiae (S agalactiae) is a germ habitually associated with infections in neonates and women during the pregnancy and the immediate puerperiumum. S. agalactiae has also been related with bacteriemias, endocarditis and bone, joint, skin and soft tissues infections in adults with concomitant diseases and even in immunocompetent patients. In the last years more than 70 cases of septic arthritis in adults due to this germ have been communicated. We present two cases of axial and peripheral joint infection due to S. agalactiae, comparing finds, treatment and evolution with the cases published until April, 2008.  相似文献   
106.
Body fat content and 25-hydroxyvitamin D levels in healthy women   总被引:15,自引:0,他引:15  
Obesity is associated with alterations in the vitamin D endocrine system. Lower levels of serum 25-hydroxyvitamin D (25-OHD) in morbidly obese individuals may be secondary to an alteration in tissue distribution resulting from an increase in adipose mass. Therefore, morbidly obese individuals are expected to need higher doses of vitamin D supplementation than the general population. However, it is still unknown whether adiposity (or percentage body fat) should be taken into consideration while assessing vitamin D requirements in the general population. To study the relationship between 25-OHD levels and percentage body fat content in healthy women, we studied 410 healthy women between 20 and 80 yr of age with body mass index ranging from 17 to 30 kg/m2. We analyzed the correlation between serum 25-OHD level and percentage body fat measured by dual energy x-ray absorptiometry. We also analyzed the influence of season, dietary vitamin D intake, age, and race on this relationship. The levels of serum 25-OHD inversely correlated with percentage body fat. The correlation was -0.13 (P = 0.013) after adjusting for race, age, season, and dietary vitamin D intake. In a multiple stepwise regression, race and season were found to have a major influence on serum 25-OHD (cumulative R2 = 0.34), and percentage body fat, although modest (additional R2 = 0.02), also had an independent statistically significant influence on serum 25-OHD levels. We conclude, percentage body fat content is inversely related to the serum 25-OHD levels in healthy women.  相似文献   
107.
108.
Recent studies have suggested that sleep is associated with IQ measures in children, but the underlying mechanism remains unknown. An association between sleep spindles and IQ has been found in adults, but only two previous studies have explored this topic in children. The goal of this study was to examine whether sleep spindle frequency, amplitude, duration and/or density were associated with performance on the perceptual reasoning, verbal comprehension, working memory, and processing speed subscales of the Wechsler Intelligence Scale for Children-IV (WISC-IV). We recruited 29 typically developing children 7–11 years of age. We used portable polysomnography to document sleep architecture in the natural home environment and evaluated IQ. We found that lower sleep spindle frequency was associated with better performance on the perceptual reasoning and working memory WISC-IV scales, but that sleep spindle amplitude, duration and density were not associated with performance on the IQ test.  相似文献   
109.
ObjectivesOur review aims to present existing data on the safety of Intravenous thrombolysis (IVT) use in acute ischemic stroke (AIS) patients with concomitant central nervous system or systemic malignancies, with attention to special circumstances pertaining to specific cancer subtypes to help in acute decision making, especially for neurologists and emergency medicine physicians.MethodsA literature search was conducted on electronic databases inclusive of Medline, EMBASE and CINAHL for articles published or available in English between January 1, 2000 to June 1, 2020 using the following search terms: “acute ischemic stroke,” “cerebrovascular disease,” “Intravenous thrombolysis,” “tissue plasminogen activator,” “cancer patients,” and “neoplasm”.ConclusionRecognition of stroke symptoms in patients with active cancer, in particularly those involving the brain, requires astute clinical judgement. Decision-making can be improved by understanding baseline functional status, cancer prognosis and expected disability from stroke, as well as utilizing diagnostic modalities such acute MRI where needed. While this article does not encourage use of IVT in patients with all malignancies, it lays the groundwork for decision making should thrombolysis be a consideration in a patient with AIS in a cancer patient.  相似文献   
110.
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