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   1935篇
  免费   118篇
  国内免费   10篇
耳鼻咽喉   28篇
儿科学   35篇
妇产科学   22篇
基础医学   229篇
口腔科学   206篇
临床医学   126篇
内科学   398篇
皮肤病学   39篇
神经病学   134篇
特种医学   62篇
外科学   319篇
综合类   8篇
预防医学   187篇
眼科学   9篇
药学   213篇
中国医学   11篇
肿瘤学   37篇
  2023年   12篇
  2022年   28篇
  2021年   62篇
  2020年   62篇
  2019年   57篇
  2018年   59篇
  2017年   52篇
  2016年   63篇
  2015年   45篇
  2014年   70篇
  2013年   106篇
  2012年   150篇
  2011年   158篇
  2010年   88篇
  2009年   62篇
  2008年   121篇
  2007年   124篇
  2006年   103篇
  2005年   83篇
  2004年   78篇
  2003年   66篇
  2002年   44篇
  2001年   51篇
  2000年   49篇
  1999年   48篇
  1998年   14篇
  1997年   11篇
  1996年   11篇
  1995年   10篇
  1994年   10篇
  1993年   8篇
  1992年   18篇
  1991年   18篇
  1990年   15篇
  1989年   15篇
  1988年   6篇
  1987年   12篇
  1986年   7篇
  1985年   7篇
  1984年   5篇
  1983年   6篇
  1982年   4篇
  1980年   5篇
  1979年   8篇
  1978年   6篇
  1977年   6篇
  1974年   5篇
  1973年   2篇
  1972年   2篇
  1967年   2篇
排序方式: 共有2063条查询结果,搜索用时 156 毫秒
41.
In the auditory brain, some populations of neurons exhibit stimulus-specific adaptation (SSA), whereby they adapt to frequently occurring stimuli but retain sensitivity to stimuli that are rare. SA has been observed in auditory structures from the midbrain to the primary auditory cortex (A1) and has been proposed to be a precursor to the generation of deviance detection. SSA is strongly expressed in non-lemniscal regions of the medial geniculate body (MGB), the principal nucleus of the auditory thalamus. In this account we review the state of the art of SSA research in the MGB, highlighting the importance of this auditory centre in detecting sounds that may be relevant for survival.  相似文献   
42.
To better understand the recent success/emergence of Salmonella enterica serotype 4,[5],12:i:- we characterized the population diversity, fljAB deletion patterns, antibiotic resistance features and associated genetic elements of a comprehensive collection obtained in the last decade from Portugal (2002–2010). One hundred thirty-one isolates from human clinical specimens, food, environment and piggeries, verified by PCR as S. 4,[5],12:i:-, were studied for clonality (Pulsed-Field Gel Electrophoresis and Multilocus Sequence Typing), antibiotic resistance by phenotypic (disk diffusion and/or agar dilution) and genotypic (PCR/Restriction Fragment Length Polymorphism and sequencing, genomic location) methods and fljAB-deletions (PCR). Plasmid analysis included determination of size, content and characterization of the incompatibility group (PCR-Based Replicon Typing and I-CeuI/S1-hybridization). Results showed three multidrug-resistant (MDR) clones circulating and causing infections, associated with particular phenotypic and genotypic features. Most of the isolates belonged to the widespread European (ASSuT phenotype, RR1-RR2 resistance regions, ST34) and Spanish (carrying a sul3-type III integron within IncA/C plasmids, ST19) clones circulating in Europe. A third clone, here designated Southern European clone (carrying a sul3-type I integron within IncR plasmids, ST19), presents a fljAB region different from the previous clones and similar to the US strains, despite differences in the MDR mobile genetic platforms. The success of S. 4,[5],12:i:- might be related to the selective advantage offered by MDR profiles associated with stable genetic elements, also carrying virulence features, along with well adapted clones to the animal food production and causing human infections.  相似文献   
43.
Ileal intussusception is the invagination of the small intestine within itself and accounts for 1% of cases of acute obstruction. However, physicians do not initially consider intussusception as a possible diagnosis of obstruction due to its rarity in adults. Herein, we report the case of a 22-year-old male who was admitted to the Emergency Department with continuous abdominal pain. Ultrasonography and computed tomography revealed an ileal intussusception. The patient underwent surgical removal of the segment of the small bowel. Unexpectedly, pathology revealed that the invagination occurred due to a parasite egg, with features suggestive of Schistosoma species. Schistosomiasis, although considered a parasitic disease in tropical countries, is not absent from Europe and though it is highly improbable, it may be responsible for cases of intussusception in adults.  相似文献   
44.
Ecotoxicology - This study aimed to investigate the mode of action of cadmium (Cd) toxicity at cell level, especially at early stages of plant exposure. Tomato seedlings were cultivated in growth...  相似文献   
45.

Background

Metabolic syndrome (MS) is an aggregation of risk factors that increase the incidence of cardiovascular events and diabetes mellitus (DM). Population aging is accompanied by higher prevalence of MS, which varies depending on the population studied and the diagnostic criteria used.

Objective

To determine prevalence of MS in the elderly using four diagnostic criteria and agreement between them.

Methods

Cross-sectional study on 243 patients older than 60 years (180 women) in Niterói, RJ. They were evaluated by clinical examination, fasting glucose, fasting insulin, lipid profile and anthropometric measurements - weight, height, waist circumference and waist/hip ratio. Prevalence of MS was estimated by World Health Organization (WHO) modified, National Cholesterol Education Program - Adult Treatment Panel III (NCEP-ATP III), International Diabetes Federation (IDF) and Joint Interim Statement (JIS) criteria.

Results

Prevalence was high with the four criteria WHO (51.9%), NCEP-ATPIII (45.2%), IDF (64.1%) and JIS (69.1%), and agreement between criteria by kappa was moderate in almost all comparisons WHO vs. IDF (k = 0.47;95% confidence interval (CI), 0.35 to 0.58); WHO vs. NCEP-ATPIII (k = 0.51; 95% CI, 0.40 to 0.61); WHO vs. JIS (k = 0.45; 95% CI, 0.33 to 0.56); IDF vs. NCEP-ATPIII (k = 0.55; 95% CI, 0.45 to 0.65) and NCEP-ATPIII vs. JIS (k = 0.53; 95% CI, 0.43-0.64), except between IDF vs. JIS (K = 0.89;95% CI, 0.83 to 0.95), which was considered good.

Conclusion

Prevalence of MS was high with the four diagnostic criteria, mainly by JIS. There was good agreement between JIS and IDF criteria and moderate among the others.  相似文献   
46.
Two cases of swallowing of foreign material related to dental implants during dental practice are described. A conservative approach by clinical-radiographic follow-up was performed in both cases; however, one of the patients required colonoscopy under general anesthesia for the removal of the impacted foreign body from the intestinal region. These complications not only have associated economic cost but also carry the risk of malpractice litigation against the professional; thus, the surgeon was responsible for all the costs of hospital and surgery management of this case. Details of the clinical signs, radiographic examinations, type of treatment, and follow-up are presented.  相似文献   
47.

Background  

Glioblastoma remains one of the most devastating human malignancies, and despite therapeutic advances, there are no drugs that significantly improve the patient survival. Altered expression of the Aurora kinases was found in different malignancies, and their inhibition has been studied in cancer therapy. In this study, we analyzed the expression of Aurora A and Aurora B in glioblastoma samples and also analyzed whether the effects of Aurora kinase inhibition were associated with temozolomide or not on cell lines and primary cultures of glioblastoma.  相似文献   
48.
49.

Introduction

In vitro hydrodynamic characterization of prosthetic heart valves provides important information regarding their operation, especially if performed by noninvasive techniques of anemometry. Once velocity profiles for each valve are provided, it is possible to compare them in terms of hydrodynamic performance. In this first experimental study using laser doppler anemometry with mechanical valves, the simulations were performed at a steady flow workbench.

Objective

To compare unidimensional velocity profiles at the central plane of two bi-leaflet aortic prosthesis from St. Jude (AGN 21 - 751 and 21 AJ - 501 models) exposed to a steady flow regime, on four distinct sections, three downstream and one upstream.

Methods

To provide similar conditions for the flow through each prosthesis by a steady flow workbench (water, flow rate of 17L/min. ) and, for the same sections and sweeps, to obtain the velocity profiles of each heart valve by unidimensional measurements.

Results

It was found that higher velocities correspond to the prosthesis with smaller inner diameter and instabilities of flow are larger as the section of interest is closer to the valve. Regions of recirculation, stagnation of flow, low pressure, and flow peak velocities were also found.

Conclusions

Considering the hydrodynamic aspect and for every section measured, it could be concluded that the prosthesis model AGN 21 - 751 (RegentTM) is superior to the 21 AJ - 501 model (Master Series). Based on the results, future studies can choose to focus on specific regions of the these valves.  相似文献   
50.
ObjectiveCompare the anti-T. gondii IgG titer between HIV-1 infected and non HIV-1 infected pregnant women and report three cases of congenital toxoplasmosis resulting from reactivation of infection during pregnancy of HIV-1 infected women.MethodsThis study was conducted among 2,270 pregnant women with chronic Toxoplasma gondii infection (absence of IgM and presence of IgG), including 82 HIV-1 infected and 2,188 non-infected women.ResultsThe average anti-T. gondii IgG titer was 127 for the 2,188 non-HIV-1 infected women, and 227 for the 82 HIV-1-infected women (p = 0,007). These results suggested that higher anti-T. gondii IgG titers in HIV-1-infected pregnant women may not be indicative of an elevated risk for fetal infection. In this study three cases of congenital toxoplasmosis that resulted from infection reactivation during pregnancy of HIV-1-infected women were manifested by fetal death, symptomatic infection, and infant without symptoms, respectively. In two of these women, a ten-fold increase in IgG levels above used cutoff was observed (2,320 UI/mL and 3,613 UI/mL, respectively). In the third pregnant women anti-T. gondii IgG titers during pregnancy did not rise despite the occurrence of congenital toxoplasmosis (204; 198; 172 UI/mL).ConclusionsCongenital toxoplasmosis resulting reactivation of infection during pregnancy in the studied group leads us to believe that it is a public health problem, especially in our population, in which seroprevalence of T. gondii infections is high. These findings also suggest that special attention is necessary during pregnancy, because the serologic diagnosis may not be indicative of toxoplasmosis reactivation.  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