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   4095篇
  免费   337篇
  国内免费   16篇
耳鼻咽喉   37篇
儿科学   168篇
妇产科学   129篇
基础医学   545篇
口腔科学   64篇
临床医学   504篇
内科学   777篇
皮肤病学   58篇
神经病学   407篇
特种医学   90篇
外科学   489篇
综合类   71篇
一般理论   1篇
预防医学   456篇
眼科学   100篇
药学   202篇
中国医学   2篇
肿瘤学   348篇
  2023年   29篇
  2022年   26篇
  2021年   104篇
  2020年   94篇
  2019年   138篇
  2018年   156篇
  2017年   85篇
  2016年   119篇
  2015年   129篇
  2014年   163篇
  2013年   190篇
  2012年   331篇
  2011年   341篇
  2010年   178篇
  2009年   168篇
  2008年   264篇
  2007年   283篇
  2006年   254篇
  2005年   276篇
  2004年   232篇
  2003年   204篇
  2002年   190篇
  2001年   45篇
  2000年   35篇
  1999年   37篇
  1998年   37篇
  1997年   11篇
  1996年   21篇
  1995年   11篇
  1994年   17篇
  1993年   20篇
  1992年   13篇
  1991年   17篇
  1990年   18篇
  1989年   17篇
  1988年   10篇
  1987年   22篇
  1986年   9篇
  1985年   15篇
  1984年   8篇
  1983年   9篇
  1982年   8篇
  1981年   8篇
  1980年   9篇
  1978年   11篇
  1976年   7篇
  1975年   11篇
  1974年   8篇
  1971年   7篇
  1970年   8篇
排序方式: 共有4448条查询结果,搜索用时 296 毫秒
1.

Objective

Arch obstruction after the Norwood procedure is common and contributes to mortality. We determined the prevalence, associated factors, and practice variability of arch reintervention and assessed whether arch reintervention is associated with mortality.

Methods

From 2005 to 2017, 593 neonates in the Congenital Heart Surgeons' Society Critical Left Heart Obstruction cohort underwent a Norwood procedure. Median follow-up was 3.7 years. Multivariable parametric models, including a modulated renewal analysis, were performed.

Results

Of the 593 neonates, 146 (25%) underwent 218 reinterventions for arch obstruction after the Norwood procedure: catheter-based (n = 168) or surgical (n = 50) at a median age of 4.3 months (quartile 1-quartile 3, 2.6-5.7). Interdigitation of the distal aortic anastomosis was protective against arch reintervention. Development of ≥ moderate tricuspid valve regurgitation and right ventricular dysfunction at any point was associated with arch reintervention. Nonsignificant variables for arch reintervention included shunt type and preoperative aortic measurements. Surgical arch reintervention was protective against arch reintervention, but transcatheter reintervention was associated with increased reintervention. Arch reintervention was not associated with increased mortality. There was wide institutional variation in incidence of arch reintervention (range, 0-40 reinterventions per 100 years patient follow-up) and in preintervention gradient (range, 0-64 mm Hg).

Conclusions

Interdigitation of the distal aortic anastomosis during the Norwood procedure decreased the risk of arch reintervention. Surgical arch reintervention is more definitive than transcatheter. Arch reintervention after the Norwood procedure is not associated with increased mortality. Serial surveillance for arch obstruction, integrated with changes in right ventricular function and tricuspid valve regurgitation, is recommended after the Norwood procedure to improve outcomes.  相似文献   
2.

Background

A history of childhood maltreatment and psychopathology are common in adults with obesity.

Objectives

To report childhood maltreatment and to evaluate associations between severity and type of childhood maltreatment and lifetime history of psychopathology among adults with severe obesity awaiting bariatric surgery.

Setting

Four clinical centers of the Longitudinal Assessment of Bariatric Surgery Research Consortium.

Methods

The Childhood Trauma Questionnaire, which assesses presence/severity (i.e., none, mild, moderate, severe) of physical abuse, mental abuse, physical neglect, mental neglect, and sexual abuse, was completed by 302 female and 66 male bariatric surgery patients. Presurgery lifetime history of psychopathology and suicidal ideation/behavior were assessed with the Structured Clinical Interview for DSM-IV and the Suicidal Behavioral Questionnaire-Revised, respectively. Presurgery lifetime history of antidepressant use was self-reported.

Results

Two thirds (66.6%) of females and 47.0% of males reported at least 1 form of childhood trauma; 42.4% and 24.2%, respectively, at greater than or equal to moderate severity. Among women, presence/greater severity of childhood mental or physical abuse or neglect was associated with a higher risk of history of psychopathology (i.e., major depressive disorder, posttraumatic stress disorder, other anxiety disorder, alcohol use disorder, binge eating disorder), suicidal ideation/behavior and antidepressant use (P for all ≤ .02). These associations were independent of age, race, education, body mass index, and childhood sexual abuse. Childhood sexual abuse was independently associated with a history of suicidal ideation/behavior and antidepressant use only (P for both ≤ .05). Statistical power was limited to evaluate these associations among men.

Conclusion

Among women with obesity, presence/severity of childhood trauma was positively associated with relatively common psychiatric disorders.  相似文献   
3.
4.
5.
We examined determinants of nonvertebral fracture in elderly men from six U.S. communities followed an average of 4.1 years. Six clinical risk factors predicted fracture risk independent of hip BMD: tricyclic antidepressant use, previous fracture, inability to complete a narrow walk trial, falls in previous year, age > or =80 years, and depressed mood. INTRODUCTION: There are few prospective studies of fracture determinants in men. We examined the associations between a comprehensive set of clinical risk factors and risk of nonspine fracture in older men and whether determinants of fracture risk were independent of total hip BMD. MATERIALS AND METHODS: A total of 5995 men > or =65 years of age were recruited from six communities in the Unites States and followed prospectively for an average of 4.1 years. Baseline assessments of demographic, lifestyle, medical history, functional status, anthropometry, and cognitive, visual, and neuromuscular function were assessed by questionnaire or examination. Triannual mailed questionnaires ascertained incident fracture; reported fractures were adjudicated by physicians using medical records and X-ray reports. Proportional hazards models were used to develop multivariable models, selecting variables and controlling for BMD. RESULTS: Of 5876 men, 4.7% (N = 275) reported an incident nonspine fracture during follow-up (11.46/1000 person-years). Tricyclic antidepressant use (hazard ratio [HR], 2.36; 95% CI, 1.25-4.46), history of fracture at or after age 50 (HR, 2.07; 95% CI, 1.62-2.65), inability to complete a narrow walk trial (HR, 1.70; 95% CI, 1.23-2.34), falls in previous year (HR, 1.59; 95% CI, 1.23-2.05), age > or =80 years (HR, 1.33; 95% CI, 1.01-1.76), depressed mood (HR, 1.72; 95% CI, 1.00-2.95), and decreased total hip BMD (HR, 1.53; 95% CI, 1.34-1.74) were independently related to increased risk. Compared with having none (48.0% of men), having three or more of the clinical risk factors (4.9% of men) increased fracture risk 5-fold, independent of BMD. Having three or more risk factors and being in the lowest tertile of BMD was associated with a 15-fold greater risk than having no risk factors and being in the highest BMD tertile. CONCLUSIONS: Several clinical risk factors were independently associated with nonspine fractures in elderly men. The combination of multiple risk factors and low BMD was a very powerful indicator of fracture risk.  相似文献   
6.
Age and gender interactions on verbal memory performance.   总被引:1,自引:0,他引:1  
Age and gender effects on verbal episodic memory are well established. However, the possibility of interactions between age and gender has been raised by studies linking estrogen and verbal memory performance, and by research suggesting gender differences in age-related cortical atrophy. We evaluated whether age by gender interactions in verbal memory were present. Subjects within three years of the median age of menopause were excluded from a large cohort of normal subjects, resulting in a younger sample (16-47 years) of 288 men and 285 women, and an older sample (55-89 years) of 201 men and 245 women. All subjects were administered the CVLT-2, a multiple-trial list-learning task. Verbal memory was negatively correlated with age for younger men, older men, and older women, but not for younger women. Multivariate analyses indicated age by gender interactions on memory for the younger group but not the older group. Results indicate that verbal memory declines with age for younger men but not younger women, whereas both older men and older women show age-related declines. These findings are consistent with hypotheses linking estrogen and verbal memory performance, and with imaging data suggesting that age-related hippocampal atrophy is found in younger men but not younger women. The role of estrogen on cognition in normal aging warrants further study.  相似文献   
7.

Background  

Genes involved in dopaminergic neurotransmission have been suggested as candidates for involvement in smoking behavior. We hypothesized that alleles associated with reduced dopaminergic neurotransmission would be more common in continuing smokers than among women who quit smoking.  相似文献   
8.
The Critical Time Intervention Project is a three-year clinical trial which tests a time-limited, supportive intervention to reduce recurrent homelessness among mentally ill men moving from a shelter to the community. Along with a comparison of nights spent homeless and other outcomes, the evaluation of the Critical Time Intervention includes a comparison of the relative costs of the intervention, compared to usual treatment. Such cost effectiveness analyses are difficult to perform and are rarely applied to mental health treatments. This paper presents the general scheme of this analysis and discusses critical issues in the construction and measurement of cost variables. Preliminary results which have implications for the cost analysis are presented.  相似文献   
9.
10.
PURPOSE: This investigation examined the effects of nebulized hypertonic saline, isotonic saline (IS), and sterile (hypotonic) water on phonation threshold pressure (PTP) and self-perceived phonatory effort (PPE) following a surface laryngeal dehydration challenge. METHOD: In a double-blind, randomized experimental trial, 60 vocally healthy women (n = 15 per group) underwent a laryngeal desiccation challenge involving oral breathing for 15 min using medical-grade dry air (RH<1%). Three of the four groups then received nebulized isotonic saline (0.9% NaCl), hypertonic saline (7% NaCl), or sterile (hypotonic) water, respectively; the 4th group served as a nontreatment control. PTP and PPE were estimated for high-pitched productions at baseline, immediately postdesiccation, and at 5, 20, 35, and 50 min postnebulization. RESULTS: PTP increased significantly for all groups following the desiccation challenge. PTP values were, on average, 0.5 cm H(2)O greater immediately postdesiccation versus baseline. In contrast, PTP values did not change significantly following the administration of nebulized treatments, although a temporary trend toward a reduction in PTP was observed for the IS group. Unexpectedly, PPE ratings decreased significantly after the desiccation challenge. In general, PPE ratings were poorly correlated with PTP measures. CONCLUSION: A laryngeal desiccation challenge (i.e., temporary exposure to extremely low relative humidity while breathing transorally) significantly increased PTP. Although interesting trends emerged, none of the nebulized treatments significantly enhanced recovery from the negative effects of desiccation on PTP. In light of very low correlations between PTP and PPE, serious questions are raised regarding presumed associations between these measures.  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