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   1216篇
  免费   87篇
  国内免费   16篇
耳鼻咽喉   15篇
儿科学   57篇
妇产科学   38篇
基础医学   138篇
口腔科学   35篇
临床医学   126篇
内科学   237篇
皮肤病学   40篇
神经病学   65篇
特种医学   204篇
外科学   80篇
综合类   41篇
预防医学   59篇
眼科学   46篇
药学   66篇
中国医学   2篇
肿瘤学   70篇
  2022年   7篇
  2021年   24篇
  2020年   23篇
  2019年   24篇
  2018年   20篇
  2017年   23篇
  2016年   21篇
  2015年   30篇
  2014年   33篇
  2013年   52篇
  2012年   41篇
  2011年   33篇
  2010年   61篇
  2009年   53篇
  2008年   32篇
  2007年   49篇
  2006年   38篇
  2005年   35篇
  2004年   28篇
  2003年   34篇
  2002年   23篇
  2001年   19篇
  2000年   32篇
  1999年   19篇
  1998年   48篇
  1997年   42篇
  1996年   38篇
  1995年   25篇
  1994年   36篇
  1993年   32篇
  1992年   15篇
  1991年   22篇
  1990年   16篇
  1989年   38篇
  1988年   24篇
  1987年   17篇
  1986年   11篇
  1985年   16篇
  1984年   9篇
  1983年   12篇
  1982年   13篇
  1981年   13篇
  1980年   16篇
  1978年   12篇
  1977年   13篇
  1976年   9篇
  1975年   6篇
  1966年   5篇
  1947年   4篇
  1943年   4篇
排序方式: 共有1319条查询结果,搜索用时 15 毫秒
51.
Percutaneous balloon aortic valvotomy was attempted in six consecutiveadolescents and young adults, (meanage 18 ± 5 years),with severe congenital aortic valvular stenosis. Peak systolicaortic valve gradient measurement and aortography was performedbefore and immediately after valvotomy, and a 1–6 monthsfollow-up. The single-balloon technique was used in two patientsand the double-balloon technique in four patients. After balloonvalvotomy the mean peak systolic aortic valve gradient (PSG)decreased from 122 ± 53 to 43 ± 20 mmHg (P >001). The haemodynamic improvement persisted at follow-up (PSG= 47 ±31 mmHg), except in one patient who had previouslyundergone aortic surgical valvotomy. One balloon valvotomy wasunsuccessful, presumably because of the selection of an inappropriatelysmall balloon. Two patients with critical aortic stenosis (PSG>165mmHg), who exhibited a thick aortic valve on echocardiographywith a relatively small aortic root and annulus, had a dramaticreduction in PSG. However, the degree of aortic regurgitationincreased significantly in both cases. The theoretical haemodynamicadvantage of the double versus the single balloon techniqueswas confirmed in one patient. We have demonstrated that percutaneousballoon aortic valvotomy using either the single- or double-balloontechnique is feasible in young adults with severe congenitalaortic stenosis. Further studies are required both to defineappropriate patients and the selection of balloon diameter andlength.  相似文献   
52.
Polycystic kidney disease (PKD) is the most common genetic cause of renal failure in humans. Several proteins that are encoded by genes associated with PKD have recently been identified in primary cilia in renal tubular epithelia. These findings have suggested that abnormalities in cilia formation and function may play a role in the pathogenesis of PKD. To directly determine whether cilia are essential to maintain tubular integrity, we conditionally inactivated KIF3A, a subunit of kinesin-II that is essential for cilia formation, in renal epithelia. Constitutive inactivation of KIF3A produces abnormalities of left-right axis determination and embryonic lethality. Here we show that tissue-specific inactivation of KIF3A in renal tubular epithelial cells results in viable offspring with normal-appearing kidneys at birth. Cysts begin to develop in the kidney at postnatal day 5 and cause renal failure by postnatal day 21. The cyst epithelial cells lack primary cilia and exhibit increased proliferation and apoptosis, apical mislocalization of the epidermal growth factor receptor, increased expression of beta-catenin and c-Myc, and inhibition of p21(CIP1). These results demonstrate that the absence of renal cilia produces both the clinical and cell biological findings associated with PKD. Most generally, the phenotype of Kif3a mutant mice suggests a role for primary cilia in the maintenance of lumen-forming epithelial differentiation.  相似文献   
53.
54.
55.
A disparity exists in the educational qualifications of dental assistants working in various public and private institutions in Riyadh, Saudi Arabia. The aim of this study was to assess the influence of professional and personal characteristics on job satisfaction among dental assistants. A cross-sectional survey was performed among dental assistants using a 24-item self-administered questionnaire. Multinomial logistic regression was used to assess the relationship between overall job satisfaction and other variables. The overall response rate was 72.1%. Factor analysis suggested that five underlying factors were related to job satisfaction. The mean score for overall job satisfaction was 3.86 (satisfied) out of 5. Among the work environment factors, the highest mean score, 4.26 (satisfied), was obtained for quality of service, and the lowest mean score, 2.78 (neutral), was obtained for the perception of income. The income and general prospects of the profession was significantly associated with overall job satisfaction. This study suggests that for dental assistants, professional and personal life, quality of service, perception of income and prestige and self-respect are important factors for job satisfaction. Despite differences in professional formation standards, in general, the study participants were considerably satisfied with their jobs.  相似文献   
56.
This study examined fathers' perceptions regarding their home-based activities (HBA) and the influence of fathers' demographic characteristics on their perceptions and practices at home. A total of 396 fathers completed a survey questionnaire describing their demographic information, perceptions and their practices regarding their involvement in HBA. Results indicated that fathers have moderate level of practice concerning their HBA, yet they have low perception of their actual practice at HBA. In addition, there was a statistical significance in HBA due to fathers' age, educational level and specialisation which had an influence on their perceptions as well. Recommendations and implications of future research were discussed.  相似文献   
57.

Background

22q11.2 deletion syndrome (22q11.2DS) is a common microdeletion syndrome, which occurs in approximately 1:4000 births. Familial autosomal dominant recurrence of the syndrome is detected in about 8-28% of the cases. Aim of this study is to evaluate the intergenerational and intrafamilial phenotypic variability in a cohort of familial cases carrying a 22q11.2 deletion.

Methods

Thirty-two 22q11.2DS subjects among 26 families were enrolled.

Results

Second generation subjects showed a significantly higher number of features than their transmitting parents (212 vs 129, P?=?0.0015). Congenital heart defect, calcium-phosphorus metabolism abnormalities, developmental and speech delay were more represented in the second generation (P?<?0.05). Ocular disorders were more frequent in the parent group. No significant difference was observed for the other clinical variables. Intrafamilial phenotypic heterogeneity was identified in the pedigrees. In 23/32 families, a higher number of features were found in individuals from the second generation and a more severe phenotype was observed in almost all of them, indicating the worsening of the phenotype over generations. Both genetic and epigenetic mechanisms may be involved in the phenotypic variability.

Conclusions

Second generation subjects showed a more complex phenotype in comparison to those from the first generation. Both ascertainment bias related to patient selection or to the low rate of reproductive fitness of adults with a more severe phenotype, and several not well defined molecular mechanism, could explain intergenerational and intrafamilial phenotypic variability in this syndrome.  相似文献   
58.
59.
60.
Behçet’s disease is a rare disease characterised by recurrent oral ulcers, with systemic manifestations including genital ulcers, ocular disease, skin lesions, gastrointestinal disease, neurologic disease, vascular disease and arthritis. Most clinical manifestations of Behçet’s disease are believed to be due to vasculitis. The heterogeneous clinical spectrum is influenced by sex, ethnicity and country of residence. Vascular manifestation in the form of isolated large brachial artery aneurysm is rare in children. Treatment involves aneurysmorrhaphy to avoid rupture or ischaemic sequelae in addition to lifelong medical management to control vasculitis.  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