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   1947篇
  免费   123篇
  国内免费   53篇
耳鼻咽喉   16篇
儿科学   44篇
妇产科学   11篇
基础医学   244篇
口腔科学   42篇
临床医学   178篇
内科学   340篇
皮肤病学   20篇
神经病学   111篇
特种医学   21篇
外科学   180篇
综合类   285篇
现状与发展   1篇
预防医学   176篇
眼科学   7篇
药学   144篇
中国医学   28篇
肿瘤学   275篇
  2023年   19篇
  2022年   109篇
  2021年   92篇
  2020年   59篇
  2019年   91篇
  2018年   94篇
  2017年   81篇
  2016年   69篇
  2015年   66篇
  2014年   118篇
  2013年   135篇
  2012年   126篇
  2011年   132篇
  2010年   102篇
  2009年   89篇
  2008年   94篇
  2007年   94篇
  2006年   56篇
  2005年   68篇
  2004年   80篇
  2003年   51篇
  2002年   50篇
  2001年   57篇
  2000年   21篇
  1999年   29篇
  1998年   14篇
  1997年   10篇
  1996年   11篇
  1995年   17篇
  1994年   9篇
  1993年   4篇
  1992年   3篇
  1990年   2篇
  1989年   3篇
  1988年   4篇
  1987年   3篇
  1985年   8篇
  1984年   6篇
  1983年   6篇
  1982年   7篇
  1981年   8篇
  1980年   4篇
  1979年   4篇
  1978年   2篇
  1977年   1篇
  1976年   2篇
  1975年   3篇
  1974年   4篇
  1973年   2篇
  1971年   1篇
排序方式: 共有2123条查询结果,搜索用时 15 毫秒
51.
《Dental materials》2019,35(9):e185-e192
ObjectiveTo investigate the effectiveness of a new zinc-reinforced glass-ionomer in comparison to a common high-viscous glass-ionomer cement (HVGIC) used in multiple-surface ART-prepared cavities. The hypothesis tested was that the cumulative survival percentage of the new HVGIC is higher than that of the common HVGIC over 2 years.MethodsA randomized triple-blind parallel group clinical trial was used. A total of 218 participants, average age 15.4 years (SD = 0.2), with an occluso-proximal carious lesion in a permanent (pre-) molar were included. Restorations using test (ChemFil Rock) and control (Fuji IX GP) restoratives were placed according to the ART method by four calibrated operators. Restorations were evaluated after one week (baseline), and at 6-, 12-, 18- and 24 months from replicas and coloured photographs according to the ART restoration assessment criteria by two independent evaluators. Restoration survival curves were estimated using the Kaplan–Meier method and difference between dependent and independent variables tested with a Wald (chi-square) test.ResultsThere was a statistically significant difference in cumulative survival percentages between the two types of restorations at 2 years (P = 0.02). A higher percentage of multiple-surface restorations of Fuji IX GP (95.4%) than ChemFil Rock (85.3%) survived. Gender (P = 0.64), operator (P = 0.56) and cavity size (P = 0.81) had no effect on the survival of the type of restoration observed. Type of tooth (P = 0.004) and type of jaw (P = 0.05) showed an effect. Severe wear was the major reason for restoration failure (ChemFil Rock = 7; Fuji IX GP = 1).SignificanceChemFil Rock appears not to be a viable alternative to Fuji IX GP in restoring ART multiple-surface cavities in permanent posterior teeth.  相似文献   
52.
53.

Introduction

Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy (TMA), related to a severe functional deficiency of ADAMTS13 activity (< 10% of normal). ADAMTS13 activity is thus crucial to confirm the clinical suspicion of TTP, to distinguish it from other TMAs, and to perform the follow-up of TTP patients.

Material and methods

We compared the performance of the commercial chromogenic assay Technozym® ADAMTS13 Activity ELISA (chromogenic VWF73 substrate, Chr-VWF73, Technoclone, Vienna, Austria), to that of our in-house FRETS-VWF73 used as reference method. A large group of 247 subjects (30 healthy volunteers and 217 patients with miscellaneaous TMAs) was studied.

Results

The lower limit of detection of the Chr-VWF73 was 3%, which is well adapted to the clinically relevant threshold for TTP diagnosis (10%). Our results showed a reasonable agreement between FRETS-VWF73 and Chr-VWF73 assays to distinguish samples with an ADAMTS13 activity < 10% from those with an ADAMTS13 activity > 10%. However, Chr-VWF73 assay provided false negative results in ~ 12% of acute TTP patients. Inversely, the Chr-VWF73 assay globally underestimated ADAMTS13 activity in detectable values ranging from 11 to 100% (with a great variability compared to FRETS-VWF73), which may be a concern for the follow-up of TTP patients in remission.

Conclusion

In-house assays developed and performed by expert laboratories remain the reference methods that should be used without limitation to control values provided by commercial assays when needed. Also, the development of an international reference preparation will be crucial to improve standardization.  相似文献   
54.
Research on the regulation and function of ascending noradrenergic, dopaminergic, serotonergic, and cholinergic systems has focused on the organization and function of individual systems. In contrast, evidence describing co-activation and interactions between multiple neuromodulatory systems has remained scarce. However, commonalities in the anatomical organization of these systems and overlapping evidence concerning the post-synaptic effects of neuromodulators strongly suggest that these systems are recruited in concert; they influence each other and simultaneously modulate their target circuits. Therefore, evidence on the regulatory and functional interactions between these systems is considered essential for revealing the role of neuromodulators. This postulate extends to contemporary neurobiological hypotheses of major neuropsychiatric disorders. These hypotheses have focused largely on aberrations in the integrity or regulation of individual ascending modulatory systems, with little regard for the likely possibility that dysregulation in multiple ascending neuromodulatory systems and their interactions contribute essentially to the symptoms of these disorders. This review will paradigmatically focus on neuromodulator interactions in the PFC and be further constrained by an additional focus on their role in cognitive functions. Recent evidence indicates that individual neuromodulators, in addition to their general state-setting or gating functions, encode specific cognitive operations, further substantiating the importance of research concerning the parallel recruitment of neuromodulator systems and interactions between these systems.  相似文献   
55.
《Vaccine》2018,36(6):859-865
IntroductionInfluenza vaccination has been shown to be safe and effective against influenza and in the prevention of complicating secondary respiratory illnesses. However, its uptake in young children remains low. This study explored the views, attitudes and practices of parents and primary care providers (PCPs) on their knowledge and acceptance of influenza vaccination in children under 5.MethodsUsing a cross-sectional qualitative research design, we conducted 30 in-depth interviews with PCPs (i.e., general practitioners, practice nurses, maternal and child health nurses, and pharmacists) and five focus groups with parents (n = 50) between June 2014 and July 2015 in Melbourne, Australia. Data were thematically analysed.ResultsParents thought the vaccine could cause influenza, and influenza vaccination was not necessary for their children as they needed to build their own ‘immunity’. Parents said that they would consider vaccinating their children if recommended by their GP and if the influenza vaccine was part of the immunisation schedule. PCPs also expressed concerns regarding the efficacy of the vaccine as well as out-of-pocket costs incurred by families, and uncertainty regarding the mortality and morbidity of influenza in otherwise healthy children. However, they said they would recommend the vaccine to high-risk groups (e.g. children with chronic disease(s), and asthma).ConclusionDespite the established safety of influenza vaccines, barriers to uptake include concerns regarding the iatrogenic effects of vaccination, its administration schedule, and knowledge of influenza severity. Updated information on influenza and the efficacy of the vaccine, and incorporating influenza vaccination into the immunisation schedule may overcome some of these barriers to increase influenza vaccination in this vulnerable cohort.  相似文献   
56.
57.
58.
59.
60.
Porcine reproductive and respiratory syndrome (PRRS) causes significant economic losses to the swine industry worldwide. Although inactivated and live vaccines are commercially available for the control of PRRS, both types of vaccine have not always proven successful in terms of generating a protective immune response, particularly in the case of inactivated vaccines. In this study, we tested whether an inactivated vaccine could induce a humoral immune response to PRRS during a homologous challenge. Amino acid substitutions were introduced into glycoprotein (GP) 5 of the FL12 strain of the PRRS virus (PRRSV) using site-directed mutagenesis with a pFL12 infectious clone. The substitutions led to double deglycosylation in the putative glycosylation moieties on GP5. The mutant virus was subsequently inactivated with binary ethylenimine. The efficacy of the inactivated mutant virus was compared with that of the inactivated wild-type PRRSV. Only the inactivated mutant PRRSV induced serum neutralizing antibodies at six weeks post-vaccination. The group that was administered the inactivated mutant virus twice exhibited a significantly increased neutralizing antibody titer after a challenge with the virulent homologous strain and exhibited more rapid clearing of viremia compared to other groups, including the groups that were administered either the inactivated mutant or wild-type virus only once and the group that was administered the inactivated wild-type virus twice. Histopathological examination of lung tissue sections revealed that the group that was administered the inactivated mutant virus twice exhibited significantly thinner alveolar septa, whereas the thickness of the alveolar septa of the other groups were markedly increased due to lymphocyte infiltration. These results indicated that the deglycosylation of GP5 enhanced the immunogenicity of the inactivated mutant PRRSV and that twice administrations of the inactivated mutant virus conferred better protection against the homologous challenge. These findings suggest that the inactivated PRRSV that expresses a hypo-glycosylated GP5 is a potential inactivated vaccine candidate and a valuable tool for controlling PRRS for the swine industry.  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