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   9728篇
  免费   571篇
  国内免费   63篇
耳鼻咽喉   61篇
儿科学   287篇
妇产科学   227篇
基础医学   1417篇
口腔科学   288篇
临床医学   979篇
内科学   2226篇
皮肤病学   173篇
神经病学   1052篇
特种医学   209篇
外科学   790篇
综合类   42篇
一般理论   3篇
预防医学   827篇
眼科学   151篇
药学   741篇
中国医学   13篇
肿瘤学   876篇
  2024年   13篇
  2023年   93篇
  2022年   218篇
  2021年   328篇
  2020年   211篇
  2019年   230篇
  2018年   277篇
  2017年   210篇
  2016年   268篇
  2015年   300篇
  2014年   420篇
  2013年   544篇
  2012年   735篇
  2011年   752篇
  2010年   386篇
  2009年   350篇
  2008年   629篇
  2007年   679篇
  2006年   628篇
  2005年   548篇
  2004年   522篇
  2003年   484篇
  2002年   474篇
  2001年   59篇
  2000年   50篇
  1999年   78篇
  1998年   81篇
  1997年   81篇
  1996年   48篇
  1995年   56篇
  1994年   40篇
  1993年   34篇
  1992年   37篇
  1991年   42篇
  1990年   34篇
  1989年   49篇
  1988年   21篇
  1987年   21篇
  1986年   29篇
  1985年   33篇
  1984年   38篇
  1983年   41篇
  1982年   26篇
  1981年   24篇
  1980年   22篇
  1979年   29篇
  1978年   19篇
  1977年   10篇
  1976年   12篇
  1975年   8篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
This study was aimed at identifying predictive variables for recurrence of mitral regurgitation (MR) in patients with dilated cardiomyopathy (DCM) undergoing mitral valve (MV) repair. From January 1997 to December 2005, 142 patients with DCM, 105 (73.9%) ischemic and 37 (26.1%) non-ischemic, underwent MV repair. Mean age was 66+/-10 years and mean MR grade was 3.2+/-0.7 (scale 1+ to 4+). Ninety-seven (71% ischemic, 29% non-ischemic), out of 98 still alive at follow-up, were included in this retrospective analysis. In all cases MV posterior annuloplasty was performed; all patients were followed-up by echocardiography (mean time interval of 44+/-28 months) to evaluate MR recurrence (>or=2+/4+). Thirty-day mortality was 9.2% (13 patients). Mean MR grade at follow-up was 0.9+/-0.9. Four-year freedom from MR recurrence was 65.5%+/-8.3. Cox analysis showed left ventricular end-diastolic volume index (LVEDVi, OR=1.03, P=0.016, AUC=0.72), left ventricular end-systolic volume index (LVESVi, OR=1.03, P=0.033, AUC=0.71), left ventricular ejection fraction (LVEF, OR=0.82, P=0.001, AUC=0.72), mitral valve coaptation depth (MVCD, OR=1.6, P=0.017, AUC=0.72) to be predictive variables for MR recurrence. Preoperative left ventricular dilatation and function along with degree of papillary muscle displacement can be helpful in identifying patients with higher probability to undergo a durable MV repair.  相似文献   
72.
Risk factors for renal scarring in children with lower urinary tract dysfunction (LUTD) were evaluated. The medical records of 120 patients were assessed concerning gender, presence of vesicoureteric reflux (VUR), bladder capacity, detrusor overactivity, residual urine, febrile urinary tract infection (UTI), bacteriuria, constipation, detrusor sphincter incoordination (DSI), high detrusor pressure at maximal cystometric capacity (PMCC), low compliance, and thickness and trabeculation of the bladder wall. Renal scarring was diagnosed by 99mtechnetium-dimercaptosuccinic acid renal scan (DMSA). Renal scarring was detected in 38 patients (31%). VUR, UTI, decreased bladder capacity, urinary residue, and trabeculated and thick bladder wall were associated with scarring at univariate analysis. Multivariate analysis showed VUR (P < 0.0001) as the independent risk factor for renal scarring. Thickness of the bladder wall was a marginal risk factor (P= 0.07). Although UTI was not a risk factor, it was associated with VUR (P= 0.03). In our analysis, VUR was the main risk factor; however, renal scarring was probably due to multifactorial causes, as VUR was associated with UTI.  相似文献   
73.
BACKGROUND: The inflammatory cascade has been hypothesized to be an important mechanism of post-ischaemic myocardial reperfusion injury and several studies demonstrated that C1 esterase inhibitor (C1-INH) is effective in post-ischaemia myocardial protection. Therefore, we aimed to investigate prospectively in a randomised double-blind study the cardioprotective effects of C1-INH in ST segment elevation myocardial infarction (STEMI) in patients who underwent emergent reperfusion with coronary artery bypass grafting (CABG). METHODS: In this study, we enrolled 80 patients affected with STEMI who underwent emergent CABG. Patients were assigned in two groups (C1-INH group: receive 1000 UI of C1-INH; and placebo group: receive a saline solution). The effects of C1-INH on complement inhibition, myocardial cell injury extension and clinical outcome were studied. Haemodynamic data and myocardial function were monitored. C1-INH, C3a, C4a complement activation fragments and cardiac troponin I (cTnI) serum levels were measured before, during and after surgery. RESULTS: Patient characteristics were not different between the two groups. The overall in-hospital mortality rate was 6.2%. No statistical significant difference was observed between the two groups with regard to early mortality (p=0.36). Statistical significant difference between the two groups was showed for cardiopulmonary bypass support (p=0.04), administration of high dose of inotropes drugs (p=0.001), time of intubation (p=0.03), intensive care unit (ICU) stay (p=0.04) and in-hospital stay (p=0.03). A significant improvement in mean arterial pressure (p=0.03), cardiac index (p=0.02) and stroke volume (p=0.03) was showed in C1-INH group versus placebo group. The serum cTnI levels were significantly low in the C1-INH group versus placebo group after reperfusion, during the observation period. Plasma levels of C3a and C4a complement fragments were reduced significantly in C1-INH group. No drugs-related adverse effects were observed. CONCLUSIONS: The inhibition of the classic complement pathway by C1-INH appears to be an effective mean of preserving ischaemic myocardium from reperfusion injury as demonstrated by low serum cTnI levels in C1-INH group. Therefore, the use of C1-INH during CABG as a rescue therapy in STEMI patients is probably an effective treatment to inhibit complement activity and to improve cardiac function and haemodynamic performance without impacting early mortality. Large randomised study should be performed to support our results.  相似文献   
74.
BACKGROUND: Oral premedication is widely used in pediatric anesthesia to reduce preoperative anxiety and ensure smooth induction. Midazolam is currently the most commonly used premedicant, but good results have also been reported with clonidine. The aim of the present study was to compare clinical effects of oral midazolam and oral clonidine. METHODS: We performed a prospective open study in 64 children who were randomly assigned to receive either oral midazolam 0.5 mg.kg (-1) (group M) or oral clonidine 4 microg.kg (-1) (group C) prior to mask induction. Drug acceptance, preoperative sedation and anxiolysis, quality of mask acceptance, recovery profile and parental satisfaction were evaluated. RESULTS: The taste of oral clonidine was judged as significantly better; 14% of children rejected oral midazolam. Onset of sedation was significantly faster after premedication with midazolam (30+/-13.1 min) than with clonidine (38.5+/-14.6 min), but level of sedation was significantly better after premedication with clonidine. Quality of mask induction was equally successful in both groups. A steal-induction was performed in 66% of patients of group C, but none in group M. We observed a trend towards an increased incidence of emergence agitation after premedication with midazolam. Parental satisfaction was significantly higher in group C. CONCLUSIONS: In this study, premedication with oral clonidine appeared to be superior to oral midazolam. Quality of mask acceptance was comparable between groups, but oral clonidine was better accepted by the child, produced more effective preoperative sedation, showed a trend towards better recovery from anesthesia and had a higher degree of parental satisfaction.  相似文献   
75.
Obesity is linked to the development of cancer. Previous studies have suggested that there is a relationship between bariatric surgery and reduced cancer risk. Data sources were from Medline, Embase, and Cochrane Library. From 951 references, 13 studies met the inclusion criteria (54,257 participants). In controlled studies, bariatric surgery was associated with a reduction in the risk of cancer. The cancer incidence density rate was 1.06 cases per 1000 person-years within the surgery groups. In the meta-regression, we found an inverse relationship between the presurgical body mass index and cancer incidence after surgery (beta coefficient ?0.2, P?相似文献   
76.
Ejaculated mammalian spermatozoa acquire competence to fertilize oocytes by a two-step process: capacitation followed by acrosome reaction. The biochemical and biophysical modifications occurring in vivo in the female reproductive tract can be reproduced in vitro, and previous studies have suggested a capacitative role for adenosine A(1) receptor (A(1)R). Mice with a targeted disruption of the Adora 1 gene (A(1)R-/- mice) provide a useful model for better understanding the role of the A(1)R in fertility. Murine spermatozoa express A(1)R in the head, neck, midpiece region, and tail. The number of capacitated spermatozoa incubated in human tubal fluid was significantly reduced in A(1)R-/- compared with A(1)R+/+ and A(1)R+/- spermatozoa. The difference between A(1) R+/+ and A(1)R-/- mouse spermatozoa was mainly in the time necessary to reach the maximum percentage of capacitation. A(1)R+/+ murine sperm obtained the full state of capacitation within 90 minutes whereas A(1)R-/- sperm required 240 minutes. Caffeine, a known antagonist of A(1) and A(2A) adenosine receptors, lowered the number of capacitated sperm and affected the time of capacitation in a dose-dependent manner, mimicking the effects of the lack of A(1) receptors. Although number, motility, and viability of A(1)R-/- murine sperm was not significantly different from A(1)R+/+ mouse spermatozoa, a significant reduction of the number of pups produced by A(1)R-/- male mice suggests that A(1) receptors must be fully operative to accomplish the optimal degree of capacitation and thereby fertilization.  相似文献   
77.

Background

The request to lose weight is expanding not only in obese and morbidly obese patients but also in overweight patients affected by co-morbidities as diabetes and hypertension and who do not tolerate diet regimen or lifestyle changes. The aim of this study is a multicenter evaluation of outcomes of intragastric balloon in overweight patients.

Methods

Patients (BMI 27–30 kg/m2) treated with a BioEnterics Intragastric Balloon (BIB) between 1996 and 2010 were extracted from the database of the participating centres in Rome (Italy), Liège (Belgium) and Madrid (Spain). Primary endpoints were the efficacy and safety at 6 and 42 months from balloon positioning. Secondary endpoints included resolution of co-morbidities.

Results

A total of 261 patients were included in this study. The most common indication for balloon placement was a psychological disorder (54 %). Mean body mass index (BMI) fell from 28.6?±?0.4 at baseline to 25.4?±?2.6 kg/m2 at 6 months and to 27.0?±?3.1 kg/m2 at 3 years from BIB removal. The mean %EWL was 55.6 % at 6 months and 29.1 % at 3 years. Forty-seven patients (18 %) had complications associated with placement of the intragastric balloon (leak?=?28, intolerance?=?14, duodenal ulcer?=?2, gastritis?=?1, oesophagitis?=?1, duodenal polyps?=?1). The rate of patients with hypertension decreased from 29 % at baseline to 16 % at 3 years. Diabetes decreased from 15 to 10 %, dyslipidaemia decreased from 20 to 18 %, hypercholesterolaemia decreased from 32 to 21 % and osteoarthropathy decreased from 25 to 13 %.

Conclusions

The intragastric balloon is safe and effective in overweight patients, helping to reduce progression to obesity and decreasing the prevalence of a number of important co-morbidities.  相似文献   
78.
Measurement of gastric emptying time by real-time ultrasonography   总被引:23,自引:0,他引:23  
This paper describes an ultrasound method of assessing gastric emptying time based on measurements of the gastric antrum, which is visible in almost all subjects before and after meals. A total of 54 subjects were examined including 18 normal subjects and 36 subjects with idiopathic functional dyspepsia. The emptying time was determined in all subjects by measuring the changes in the cross-sectional area of the gastric antrum. In a subgroup of 34 subjects the volume of the whole antropyloric region was also considered. Measurements were taken by the same observer after fasting and at regular 30-min intervals after a standard 800-cal meal. Final emptying time (calculated in relation to the start of the meal) was considered to be the time at which the antral area or volume returned to basal value. Final emptying time (mean +/- SD) was 248 +/- 39 min in normal subjects and 359 +/- 64 min in patients with functional dyspepsia (p less than 0.001). A significantly higher degree of dilatation of the gastric antrum was found in dyspeptic patients than in control subjects. Barium x-ray of the stomach in 19 subjects always confirmed the ultrasound finding on the presence or absence of contents within the stomach. We conclude that this kind of ultrasound study of the antropyloric region allows accurate determination of total gastric emptying time.  相似文献   
79.
Bone homeostasis requires stringent regulation of osteoclasts, which secrete proteolytic enzymes to degrade the bone matrix. Despite recent progress in understanding how bone resorption occurs, the mechanisms regulating osteoclast secretion, and in particular the trafficking route of cathepsin K vesicles, remain elusive. Using a genetic approach, we describe the requirement for protein kinase C–delta (PKCδ) in regulating bone resorption by affecting cathepsin K exocytosis. Importantly, PKCδ deficiency does not perturb formation of the ruffled border or trafficking of lysosomal vesicles containing the vacuolar‐ATPase (v‐ATPase). Mechanistically, we find that cathepsin K exocytosis is controlled by PKCδ through modulation of the actin bundling protein myristoylated alanine‐rich C‐kinase substrate (MARCKS). The relevance of our finding is emphasized in vivo because PKCδ?/? mice exhibit increased bone mass and are protected from pathological bone loss in a model of experimental postmenopausal osteoporosis. Collectively, our data provide novel mechanistic insights into the pathways that selectively promote secretion of cathepsin K lysosomes independently of ruffled border formation, providing evidence of the presence of multiple mechanisms that regulate lysosomal exocytosis in osteoclasts. © 2012 American Society for Bone and Mineral Research.  相似文献   
80.
Video-EEG monitoring with intracranial subdural electrodes is a useful assessment tool for the localization of the epileptogenic zone in patients with drug-resistant focal epilepsy. We aimed at assessing the morbidity related to electrode implantation and the surgical outcome in patients who underwent epilepsy surgery after intracranial EEG monitoring. All patients (N?=?58) admitted to our Epilepsy Surgery Centre for drug-resistant focal epilepsy who underwent resective surgery after intracranial monitoring with subdural electrodes and were followed up for at least 2?years were included in the study. Their mean age was 30.4?years (range 8-60?years), 25 (43?%) were female, and 44 (76?%) had a preoperatively detected structural lesion. The mean duration of invasive recording was 2.3?days (range 1-14?days). Extraoperative ECoG allowed the identification of the epileptogenic focus in all cases. The temporal lobe was involved in 21 (36?%) patients, whereas extratemporal foci were identified in 24 (41?%) patients. Thirteen patients (23?%) had multilobar involvement. Functional brain mapping was performed in 15 (26?%) patients. Transient complications related to electrode implantation occurred in three patients. Among patients with evidence of lesion on preoperative MRI, lesionectomy alone was performed in 12 cases (27?%), while it was combined with tailored cortical resection in the remaining cases. Tailored cortical resection was also performed in patients without evidence of lesion on MRI. After resective surgery, transient neurological deficits occurred in five cases, while another patient experienced permanent lateral homonymous hemianopia. At the last follow-up observation, 34 (57?%) patients were seizure-free (Engel class I). This study suggests that invasive EEG recording with subdural electrodes may be useful and fairly safe for many candidates for epilepsy surgery.  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