首页 | 官方网站   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   6071篇
  免费   402篇
  国内免费   37篇
医药卫生   6510篇
  2024年   10篇
  2023年   61篇
  2022年   103篇
  2021年   234篇
  2020年   163篇
  2019年   221篇
  2018年   261篇
  2017年   169篇
  2016年   180篇
  2015年   160篇
  2014年   251篇
  2013年   327篇
  2012年   489篇
  2011年   401篇
  2010年   246篇
  2009年   236篇
  2008年   364篇
  2007年   365篇
  2006年   359篇
  2005年   337篇
  2004年   278篇
  2003年   256篇
  2002年   259篇
  2001年   71篇
  2000年   57篇
  1999年   54篇
  1998年   58篇
  1997年   48篇
  1996年   47篇
  1995年   40篇
  1994年   27篇
  1993年   15篇
  1992年   29篇
  1991年   30篇
  1990年   28篇
  1989年   31篇
  1988年   23篇
  1987年   21篇
  1986年   21篇
  1985年   16篇
  1984年   11篇
  1983年   9篇
  1982年   7篇
  1981年   10篇
  1976年   10篇
  1974年   7篇
  1973年   7篇
  1972年   12篇
  1970年   11篇
  1969年   9篇
排序方式: 共有6510条查询结果,搜索用时 0 毫秒
61.
Commercial α-cellulose was compression-molded to produce 1A dog-bone specimens under various operating conditions without any additive. The resulting agromaterials exhibited a smooth, plastic-like surface, and constituted a suitable target as replacement for plastic materials. Tensile and three-points bending tests were conducted according to ISO standards related to the evaluation of plastic materials. The specimens had strengths comparable to classical petroleum-based thermoplastics. They also exhibited high moduli, which is characteristic of brittle materials. A higher temperature and higher pressure rate produced specimens with higher mechanical properties while low moisture content produced weaker specimens. Generally, the strong specimen had higher specific gravity and lower moisture content. However, some parameters did not follow the general trend e.g., thinner specimen showed much higher Young’s Modulus, although their specific gravity and moisture content remained similar to control, revealing a marked skin-effect which was confirmed by SEM observations.  相似文献   
62.
63.
64.

Background

Information on young patients with Brugada syndrome (BrS) and arrhythmic events (AEs) is limited.

Objectives

The purpose of this study was to describe their characteristics and management as well as risk factors for AE recurrence.

Methods

A total of 57 patients (age ≤20 years), all with BrS and AEs, were divided into pediatric (age ≤12 years; n = 26) and adolescents (age 13 to 20 years; n = 31).

Results

Patients’ median age at time of first AE was 14 years, with a majority of males (74%), Caucasians (70%), and probands (79%) who presented as aborted cardiac arrest (84%). A significant proportion of patients (28%) exhibited fever-related AE. Family history of sudden cardiac death (SCD), prior syncope, spontaneous type 1 Brugada electrocardiogram (ECG), inducible ventricular fibrillation at electrophysiological study, and SCN5A mutations were present in 26%, 49%, 65%, 28%, and 58% of patients, respectively. The pediatric group differed from the adolescents, with a greater proportion of females, Caucasians, fever-related AEs, and spontaneous type-1 ECG. During follow-up, 68% of pediatric and 64% of adolescents had recurrent AE, with median time of 9.9 and 27.0 months, respectively. Approximately one-third of recurrent AEs occurred on quinidine therapy, and among the pediatric group, 60% of recurrent AEs were fever-related. Risk factors for recurrent AE included sinus node dysfunction, atrial arrhythmias, intraventricular conduction delay, or large S-wave on ECG lead I in the pediatric group and the presence of SCN5A mutation among adolescents.

Conclusions

Young BrS patients with AE represent a very arrhythmogenic group. Current management after first arrhythmia episode is associated with high recurrence rate. Alternative therapies, besides defibrillator implantation, should be considered.  相似文献   
65.
Within the framework of training offered by the University of Teacher Education of the State of Vaud leading to a Masters of Arts in Special Education and the Diploma in Special Education, four teachers in special education and a trainer-researcher undertook research work using the ICF-CY (WHO, 2007) for educational purposes. Focusing on the indicators of participation and environment, and operating on the hypothesis that these two types of variables are closely linked, they observed teaching situations in their respective workplaces. This study highlights the influence of environmental factors – one of which is the teacher – on pupil participation, and offers proposals for adjusting the terminology used by teachers in special education. The work is of particular relevance in that it opens up new observational perspectives that can, on the one hand, help to avoid the pitfall of focusing on a pupil's difficulties, delayed development, disabilities and/or limitations and, on the other hand, favor the work of identification of the educational actions to be undertaken.  相似文献   
66.
PurposeTo demonstrate the marginal corneal vascular remodelling using optical coherence tomography angiography (OCTA) after pterygium surgery.MethodsTwenty-two eyes of 19 patients (8 males, 11 females; age, 58.68 ± 0.34 years) with primary grade-T3 nasal pterygium were enroled in this study. The eyes underwent excision of the pterygium followed by a free limbal-conjunctival autograft. OCTA was performed in the nasal limbal area before surgery and at 10 days, 1 month, and 3 months after surgery. The scans were analyzed in terms of postoperative vascular remodelling of the autograft and marginal corneal vascular arcades (MCAs).ResultsPreoperatively, the pterygium presented as abnormal centripetal vascular growth in OCTA scans. The conjunctival vessel density in the nasal quadrant was 29.26% ± 1.00%, 15.80% ± 0.83%, 19.80% ± 0.88%, and 20.26% ± 0.89% before and 10 days, 1 month, and 3 months, respectively, after surgery (F = 1.55, P < 0.01). The vessel density of MCAs was 28.33% ± 0.88%, 42.09% ± 0.41%, and 42.46% ± 0.31% 10 days, 1 month, and 3 months, respectively, after surgery (F = 188.2, P < 0.01).ConclusionsWe describe a new application of OCTA for MCA vasculature imaging. Vascular remodelling of the graft and MCAs appeared at 1 month and continued for 3 months after surgery.Subject terms: Conjunctival diseases, Corneal diseases  相似文献   
67.
AIMS: Inappropriate therapy delivered by implantable cardioverter defibrillators (ICDs) remains a challenge. The OPERA registry measured the times to, and studied the determinants of, first appropriate (FAT) and inappropriate (FIT) therapies delivered by single-, dual- and triple-chamber [cardiac resynchronization therapy defibrillator (CRT-D)] ICD. METHODS AND RESULTS: We entered 636 patients (mean age = 62.0 ± 13.5 years; 88% men) in the registry, of whom 251 received single-, 238 dual-, and 147 triple-chamber ICD, for primary (30.5%) or secondary (69.5%) indications. We measured times to FAT and FIT as a function of multiple clinical characteristics, examined the effects of various algorithm components on the likelihood of FAT and FIT delivery, and searched for predictors of FAT and FIT. Over 22.8 ± 8.8 months of observation, 184 patients (28.9%) received FAT and 70 (11.0%) received FIT. Ventricular tachycardia (VT) was the trigger of 88% of FAT, and supraventricular tachycardia was the trigger of 91% of FIT. The median times to FIT (90 days; range 49-258) and FAT (171 days; 50-363) were similar. The rate of FAT was higher (P <0.001) in patients treated for secondary than primary indications, while that of FIT were similar in both groups. Out of 57 analysable FIT, 27 (47.4%) could have been prevented by fine tuning the device programming like the sustained rate duration or the VT discrimination algorithm. CONCLUSIONS: First inappropriate therapy occurred in 11% of 636 ICD recipients followed for ~2 years. Nearly 50% of FIT could have been prevented by improving device programming.  相似文献   
68.
69.
The neonatal gut is rapidly colonized by a newly dominant group of commensal Escherichia coli strains among which a large proportion produces a genotoxin called colibactin. In order to analyze the short- and long-term effects resulting from such evolution, we developed a rat model mimicking the natural transmission of E. coli from mothers to neonates. Genotoxic and non-genotoxic E. coli strains were equally transmitted to the offspring and stably colonized the gut across generations. DNA damage was only detected in neonates colonized with genotoxic E. coli strains. Signs of genotoxic stress such as anaphase bridges, higher occurrence of crypt fission and accelerated renewal of the mature epithelium were detected at adulthood. In addition, we observed alterations of secretory cell populations and gut epithelial barrier. Our findings illustrate how critical is the genotype of E. coli strains acquired at birth for gut homeostasis at adulthood.  相似文献   
70.
IntroductionPhosphodiesterase 5 inhibitors (PDE5) such as sildenafil are first-line treatment for erectile dysfunction (ED). Alpha1 (α1)-adrenoceptor antagonists such as doxazosin are indicated for the treatment of patients with lower urinary tract symptoms (LUTS)/benign prostatic hyperplasia (BPH). ED and LUTS/BPH are conditions that are often associated. Accordingly, α1-adrenoceptor antagonists and PDE5 inhibitors will be often prescribed in real life setting together.AimTo evaluate the effects of the combination of sildenafil and doxazosin on human cavernosal and prostatic tissue.MethodsProstatic and erectile tissues were obtained from nine to 12 patients, respectively. Patients underwent cystoprostatectomy for infiltrating bladder cancer or penile surgery for penile implant, congenital curvature or Peyronie's disease.Main Outcome MeasuresIn organ baths, prostatic and cavernosal strips were submitted to either concentration-response curves (CRC) to phenylephrine (Phe) or norepinephrine (NE), respectively, in presence of vehicle, sildenafil (10?6 M, 10?5 M), doxazosin (10?8 M, 3.10?8 M, or 10?7 M), or a combination of both. Continuous electrical field stimulation (EFS; 32 Hz, 5 ms, 5 seconds, 300 mA) was performed on prostatic strips which were incubated with sildenafil 10?6 M or vehicle before the successive addition of doxazosin (10?7 M, 10?6 M) or vehicle. Cavernosal strips were pre-incubated with doxazosin (10?9 M, 10?8 M) or vehicle, then CRC to sildenafil were constructed on NE (3.10?6 M) precontracted cavernosal strips.ResultsCombination of sildenafil and doxazosin exerted a greater relaxing effect on CRC to Phe or NE compared with each compound alone in both tissues. Sildenafil significantly enhanced the relaxing effect of doxazosin on EFS-induced contractions in prostatic strips. Doxazosin significantly increased the ability of sildenafil to inhibit NE-induced contractions in cavernosal strips.ConclusionsSildenafil and doxazosin reduced adrenergic tone of prostatic and cavernosal smooth muscle and their combination provided a significant benefit when targeting relaxation of both tissues. These experiments provide support for further clinical evaluation of the sildenafil and doxazosin combination in ED patients with LUTS/BPH. Oger S, Behr-Roussel D, Gorny D, Lecoz O, Lebret T, Denoux Y, Faix A, Leriche A, Wayman C, Alexandre L, and Giuliano F. Combination of doxazosin and sildenafil exerts an additive relaxing effect compared with each compound alone on human cavernosal and prostatic tissue. J Sex Med 2009;6:836–847.  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-23

京公网安备 11010802026262号