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   2518篇
  免费   153篇
  国内免费   11篇
耳鼻咽喉   71篇
儿科学   58篇
妇产科学   48篇
基础医学   355篇
口腔科学   280篇
临床医学   183篇
内科学   550篇
皮肤病学   70篇
神经病学   132篇
特种医学   61篇
外科学   251篇
综合类   4篇
一般理论   1篇
预防医学   285篇
眼科学   38篇
药学   196篇
中国医学   25篇
肿瘤学   74篇
  2023年   26篇
  2022年   55篇
  2021年   122篇
  2020年   73篇
  2019年   96篇
  2018年   139篇
  2017年   71篇
  2016年   69篇
  2015年   93篇
  2014年   119篇
  2013年   157篇
  2012年   247篇
  2011年   228篇
  2010年   118篇
  2009年   77篇
  2008年   137篇
  2007年   127篇
  2006年   106篇
  2005年   100篇
  2004年   102篇
  2003年   62篇
  2002年   75篇
  2001年   36篇
  2000年   56篇
  1999年   31篇
  1998年   6篇
  1997年   9篇
  1996年   6篇
  1995年   5篇
  1994年   5篇
  1992年   13篇
  1991年   9篇
  1990年   11篇
  1989年   9篇
  1988年   11篇
  1987年   16篇
  1986年   10篇
  1985年   12篇
  1984年   3篇
  1983年   2篇
  1982年   2篇
  1981年   2篇
  1980年   2篇
  1979年   4篇
  1974年   2篇
  1971年   2篇
  1970年   2篇
  1969年   6篇
  1968年   2篇
  1967年   2篇
排序方式: 共有2682条查询结果,搜索用时 343 毫秒
971.
Malaria and severe pneumonia in hospitalized young children may show striking clinical similarities, making differential diagnosis challenging. We investigated ways to increase diagnostic accuracy in patients hospitalized with clinical symptoms compatible with malaria and severe pneumonia, in an area with high a prevalence of infection with human immunodeficiency virus. A total of 646 children admitted at the Manhiça District Hospital in Manhiça, Mozambique who met the World Health Organization clinical criteria for severe pneumonia and malaria were recruited for 12 months and thoroughly investigated to ascertain an accurate diagnosis. Although symptom overlap between malaria and severe pneumonia was frequent among hospitalized children, true disease overlap was uncommon. Clinical presentation and laboratory determinations were ineffective in reliably distinguishing between the two diseases. Infection with human immunodeficiency virus differentially influenced the epidemiology and clinical presentation of these two infectious diseases, further challenging their discrimination on clinical grounds, and having a greater impact on the current burden and prognosis of severe pneumonia.  相似文献   
972.

Objective

Chemical solutions have been widely used for disinfection of dentures, but their effect on color stability of denture tooth acrylic resins after repeated procedures is still unclear. The aim of this in vitro study was to evaluate whether repeated cycles of chemical disinfectants affected the color stability of two denture tooth acrylic resins.

Material and Methods

Sixty disc-shaped specimens (40 mm x 3 mm) were fabricated from two different brands (Artiplus and Trilux) of denture tooth acrylic resin. The specimens from each brand (n=30) were randomly divided into 6 groups (n=5) and immersed in the following solutions: distilled water (control group) and 5 disinfecting solutions (1% sodium hypochlorite, 2% sodium hypochlorite, 5.25% sodium hypochlorite, 2% glutaraldehyde, and 4% chlorhexidine gluconate). Tooth color measurements were made by spectrophotometry. Before disinfection, the initial color of each tooth was recorded. Further color measurements were determined after subjecting the specimens to 7, 21, 30, 45, 60, and 90 immersion cycles in each tested solution. Color differences (ΔE*) were determined using the CIE L*a*b* color system. Data were analyzed using two-way repeated measures analysis of variance (ANOVA) followed by Tukey tests. The significance level was set at 5%.

Results

There were statistically significant differences in ΔE* among the 5 disinfectants and water during the 90 cycles of immersion for both denture tooth acrylic resins. Distilled water promoted the greatest color change in both denture tooth acrylic resins, nevertheless none of tested disinfectants promoted ΔE* values higher than 1.0 on these acrylic materials during the 90 cycles of disinfection.

Conclusions

Repeated immersion cycles in disinfecting solutions alter ∆E* values, however these values do not compromise the color of the tested denture tooth acrylic resins because they are imperceptible to the human eye.  相似文献   
973.
The aim of the present study was to analyze dental research trends in Brazil over the past nine years. All abstracts presented at the 26th Annual Meeting of the Brazilian Society for Dental Research in 2009 (n = 2648) were classified based on field of knowledge, home institution and geographic region. Data were compared with those previously published based on abstracts presented at various meetings. Between 2001 and 2006, five fields of knowledge had a greater than 10% representation among the total number of studies. These fields included restorative dentistry/dental materials (RD/DM), periodontics, endodontics, pediatric dentistry and population-based oral health. In 2009, only RD/DM maintained a greater than 10% proportion of meeting abstracts, and basic fields comprised the second position among those fields with greater representation (9.8%). The majority of research studies were performed at public institutions, and the number of abstracts per state increased significantly in 2009 (Wilcoxon test, p < 0.001). The southeastern region of Brazil submitted the greatest number of abstracts; however, other regions also demonstrated increased participation in research (11%). The percentage distribution of abstracts between states remained constant (Wilcoxon test, p = 0.255; r s = 0.873). The results of the present study suggest a slight shift in the scientific research profile in Brazilian dentistry: fields related to professional disciplines have declined in relative research participation, while increasing interest has been observed in basic fields and new specialties.  相似文献   
974.
Five multidrug-resistant nonclonally related Enterobacteriaceae isolates were recovered in Belgium in 2010 from three patients who had been hospitalized in Pakistan, Montenegro, and Serbia/Kosovo. New Delhi metallo-β-lactamase (NDM-1) was detected in each of the isolates in addition to several extended-spectrum β-lactamases (CTX-M-15, SHV-12), plasmidic cephalosporinases (CMY-16, CMY-58), rRNA methylases (ArmA, RmtB), and Qnr genes (qnrA6, qnrB1, qnrB2). One patient died from uncontrolled sepsis, while the two others recovered. No secondary cases occurred in any of the hospitals.  相似文献   
975.
Leptospirosis is a widespread re-emerging zoonosis of human and veterinary concern. It has been shown that virulent leptospires protect themselves against the host’s innate immune system, a strategy that allows the bacteria to reach immunologically safe environments. Although extensive studies on host–pathogen interactions have been performed, little is known on how leptospires deal with host immune attack. In a previous work, we demonstrated the ability of leptospires to bind human plasminogen (PLG), that after treatment with activators, conferred plasmin (PLA) activity on the bacteria surface. In this study, we show that the PLA activity associated to the outer surface of Leptospira could interfere with the host immune attack by conferring some evasion advantage during infection. We demonstrate that PLA-coated leptospires interfere with complement C3b and IgG depositions on the bacterial surface, probably through the degradation of these components, thus diminishing opsonization process. Similar decrease on the deposition was observed when normal and immune sera from patients diagnosed with leptospirosis were employed as a source of IgG. We believe that decreasing opsonization by PLA generation might be an important aspect of the leptospiral immune escape strategy and survival. To our knowledge, this is the first proteolytic activity of plasmin associated-Leptospira related to anti-opsonic properties reported to date.  相似文献   
976.

Background

Few investigations have correlated long-term nutritional support (NS) with outcome in the intensive care unit, in comparison with NS for shorter periods.

Objective

In a retrospective protocol, duration of enteral and/or parenteral nutrition was analyzed in the light of severity of illness, targeting hospital mortality.

Results

Seriously ill patients (n = 100), nearly all (94/100) receiving enteral nutrition (51/100), parenteral nutrition (22/100), or both (21/100), were investigated. Mean age ± SD was 60.0 ± 19.5 years (54.0% males), 56.0% were in the trauma or surgery diagnostic category, Mean Acute Physiologic and Chronic Health Evaluation II ± SD was 14.2 ± 6.7, mechanical ventilation was necessary in 41.0%, and hospital mortality was 14.0%. Nutritional support of any modality administered for 18 days or less (mean ± SD, 4.3 ± 3.6 days) was associated with favorable survival rate, whereas for longer periods (mean ± SD, 48.5 ± 29.4 days), mortality substantially increased (7.7% vs 50.0%, P = .004). Results were confirmed when long-term patients were propensity matched regarding age, Acute Physiologic and Chronic Health Evaluation II, Glasgow scale, and mechanical ventilation (6.3% vs 50.0%, P = 04).

Conclusions

Nutritional support of more than 18 days was associated with higher mortality. This finding persisted after adjustment for major risk factors, in agreement with the hypothesis that prolonged impossibility of oral alimentation is a marker of mortality in the intensive care unit setting.  相似文献   
977.
BackgroundDespite constant improvement and refinement of the prostheses, the decision between mechanical and biological valves for aortic valve replacement is still controversial.ObjectiveTo compare outcomes of aortic valve replacement with bioprosthesis and mechanical prosthesis.MethodsThis was an observational, historical cohort study with review of medical records. A total of 202 patients who underwent heart valve replacement surgery between 2004 and 2008 were selected, with a mean follow-up of 10 years. The level of significance set at 5%.ResultsMean age of patients was approximately 50 years; most patients were male (70%). Overall mortality- and reoperation-free survival was significantly higher in patients with mechanical prosthesis (HR=0.33; 95%CI=0.13-0.79; p=0.013). No difference was found in late mortality between the two groups. On the other hand, the risk of reoperation was significantly higher in patients with bioprosthesis than mechanical prosthesis (HR=0.062; 95%CI=0.008-0.457; p=0.006). The risk of composite adverse events – stroke, bleeding, endocarditis, thrombosis and paravalvular leak – was similar between the groups (HR=1.20; 95%CI= 0.74-1.93; p=0.44). The risk of bleeding was significantly higher in patients with mechanical prosthesis (HR=3.65; 95%CI= 1.43-9.29; p = 0.0064), although no case of fatal bleeding was reported.ConclusionNo difference in 10-year mortality was found between the groups. The risk of reoperation significantly increases with the use of bioprosthesis, especially for patients younger than 30 years. Patients with mechanical prosthesis are at increased risk of nonfatal bleeding.  相似文献   
978.
Currently, there is no characteristic microRNA (miRNA) expression pattern in Epstein-Barr virus+ diffuse large B-cell lymphoma of the elderly (EBV+DLBCLe). This study aims to characterize a signature profile and identify miRNAs that can be used as biomarkers and alternative therapeutic targets for EBV+DLBCLe. Seventy-one DLBCL patients aged 50 years and older were included and four EBV+ and four EBV– samples were analyzed in two miRNA array platforms (pilot study). A larger multicenter cohort (29 EBV+DLBCLe and 65 EBV–DLBCL patients) was used to validate the results by real-time polymerase chain reaction. In the pilot study, 9% of DLBCL were EBV+DLBCLe by in situ hybridization. In multicenter study, EBV+DLBCLe group showed a predominance of non-germinal center B-cell origin. Overall survival duration of EBV+DLBCLe was significantly inferior to that of EBV–DLBCL patients. We found 10 deregulated miRNAs in the two groups, but only seven were statistically different. We confirmed overexpression of hsa-miR-126, hsa-miR-146a, hsa-miR-146b, hsa-miR-150, and hsa-miR-222 and underexpression of hsa-miR-151 in EBV+DLBCLe cases compared to EBV–DLBCL cases. Hsa-miR-146b and hsa-miR-222 showed high specificity for identifying EBV+DLBCLe. The present study proposed a miRNA signature for EBV+DLBCLe and our findings suggest that hsa-miR-146b and hsa-miR-222 could be biomarkers and therapeutic targets.  相似文献   
979.
BACKGROUND: There are few studies in the literature performed in human fetuses evaluating the incidence of genitourinary anomalies. AIMS: Analyze the incidence of congenital urogenital malformations in human male fetuses. STUDY DESIGNS AND SUBJECTS: We analyzed 166 human male fetuses well preserved. The gestational age was determined in weeks post conception (WPC) according to the foot length criterion and ranged from 10 to 35 WPC. The fetuses were dissected with the aid of a stereoscopic lens with 2.5x magnification. We performed abdominal and pelvic incisions to expose the urogenital organs. We studied the incidence of renal, ureteral, vesicle, urethral, testicular, epididymal, vas deferens, prostate and penile anomalies. RESULTS: Of the 166 fetuses, 7 (4.2%) presented some kind of anomaly of the urogenital system. Renal anomalies were found in two fetuses (1.2%). Unilateral renal agenesis was found in a 25 WPC fetus. Horseshoe kidney was found in a 20 WPC fetus. In a 23 WPC fetus (0.6%) the two testes were absent. Epididymal disjunction anomalies were found in four fetuses (2.4%). CONCLUSIONS: The urogenital anomalies in human male fetuses are rare and have an incidence around 4%.  相似文献   
980.

Introduction

Total surgical resection is the treatment of choice for choroid plexus tumors. However, the hypervascular nature of such lesions imposes challenges to the surgical treatment. Preoperative embolization for intracranial tumors has been widely used in an attempt to reduce blood loss, but rarely with choroid plexus tumors.

Case report

We describe the first case of preoperative embolization of choroid plexus papilloma with Onyx via the anterior choroidal artery. The procedure underwent without any complications and surgical treatment was possible with minimal blood loss.

Discussion

Embolization of choroid plexus tumors via anterior choroidal artery is potentially dangerous, but following a meticulous technique, it can be used as a safe and effective preoperative procedure.  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