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   4340篇
  免费   226篇
  国内免费   35篇
耳鼻咽喉   62篇
儿科学   96篇
妇产科学   105篇
基础医学   566篇
口腔科学   93篇
临床医学   314篇
内科学   1179篇
皮肤病学   100篇
神经病学   374篇
特种医学   84篇
外科学   340篇
综合类   21篇
预防医学   362篇
眼科学   117篇
药学   339篇
中国医学   30篇
肿瘤学   419篇
  2024年   4篇
  2023年   31篇
  2022年   81篇
  2021年   133篇
  2020年   89篇
  2019年   111篇
  2018年   140篇
  2017年   90篇
  2016年   97篇
  2015年   128篇
  2014年   145篇
  2013年   194篇
  2012年   353篇
  2011年   329篇
  2010年   181篇
  2009年   158篇
  2008年   312篇
  2007年   297篇
  2006年   288篇
  2005年   248篇
  2004年   234篇
  2003年   221篇
  2002年   219篇
  2001年   46篇
  2000年   39篇
  1999年   47篇
  1998年   37篇
  1997年   35篇
  1996年   34篇
  1995年   30篇
  1994年   25篇
  1993年   17篇
  1992年   26篇
  1991年   20篇
  1990年   20篇
  1989年   16篇
  1988年   16篇
  1987年   8篇
  1986年   8篇
  1985年   14篇
  1984年   7篇
  1983年   6篇
  1982年   6篇
  1981年   6篇
  1980年   6篇
  1979年   5篇
  1978年   7篇
  1977年   4篇
  1976年   4篇
  1975年   4篇
排序方式: 共有4601条查询结果,搜索用时 15 毫秒
991.
In this retrospective study of patients with overt orbital retinoblastoma, we evaluated minimally disseminated disease (MDD) in bone marrow and cerebrospinal fluid (CSF) using CRX and/or GD2 synthase as markers. Ten patients were evaluated—five (50%) at diagnosis and five upon relapse. MDD was detected in four cases (one in the bone marrow, two in the CSF, and in one case in both sites). All patients received chemotherapy and four received orbital radiotherapy. Seven patients relapsed or progressed and all of them died. Three patients remain in complete remission. There was no apparent correlation between MDD and the outcome.  相似文献   
992.
993.
Experimental and epidemiological data suggest that factors of one‐carbon metabolism are important in the pathogenesis of several cancers, but prospective data on head and neck cancer (HNC) and esophagus cancer are limited. The European Prospective Investigation into Cancer and Nutrition (EPIC) study recruited 385,747 participants from 10 countries who donated a blood sample. The current study included 516 cancer cases of the head and neck and esophagus and 516 individually matched controls. Plasma levels of vitamins B2, B6, B9 (folate), B12, and methionine and homocysteine were measured in pre‐diagnostic plasma samples and analyzed in relation to HNC and esophagus cancer risk, as well as post‐diagnosis all‐cause mortality. After controlling for risk factors, study participants with higher levels of homocysteine had elevated risk of HNC, the odds ratio (OR) in conditional analysis when comparing the top and bottom quartiles of homocysteine [ORQ4vs. Q1] being 2.13 (95% confidence interval [95% CI] 1.13–4.00, p for trend 0.009). A slight decrease in HNC risk was also seen among subjects with higher levels of folate (ORQ4vs. Q1 0.63, 95% CI 0.35–1.16, p for trend 0.02). Subgroup analyses by anatomical sub‐site indicated particularly strong associations with circulating homocysteine for oral cavity and gum cancer (p for trend 8 × 10?4), as well as for oropharynx cancer (p for trend 0.008). Plasma concentrations of the other investigated biomarkers did not display any clear association with risk or survival. In conclusion, study participants with elevated circulating levels of homocysteine had increased risk of developing squamous cell carcinoma of the head and neck.  相似文献   
994.
Eric J. Duell  Leila Lujan‐Barroso  Núria Sala  Samantha Deitz McElyea  Kim Overvad  Anne Tjonneland  Anja Olsen  Elisabete Weiderpass  Lill‐Tove Busund  Line Moi  David Muller  Paolo Vineis  Dagfinn Aune  Giuseppe Matullo  Alessio Naccarati  Salvatore Panico  Giovanna Tagliabue  Rosario Tumino  Domenico Palli  Rudolf Kaaks  Verena A. Katzke  Heiner Boeing  H. B Bueno‐de‐Mesquita  Petra H. Peeters  Antonia Trichopoulou  Pagona Lagiou  Anastasia Kotanidou  Ruth C. Travis  Nick Wareham  Kay‐Tee Khaw  Jose Ramon Quiros  Miguel Rodríguez‐Barranco  Miren Dorronsoro  María‐Dolores Chirlaque  Eva Ardanaz  Gianluca Severi  Marie‐Christine Boutron‐Ruault  Vinciane Rebours  Paul Brennan  Marc Gunter  Ghislaine Scelo  Greg Cote  Stuart Sherman  Murray Korc 《International journal of cancer. Journal international du cancer》2017,141(5):905-915
Noninvasive biomarkers for early pancreatic ductal adenocarcinoma (PDAC) diagnosis and disease risk stratification are greatly needed. We conducted a nested case‐control study within the Prospective Investigation into Cancer and Nutrition (EPIC) cohort to evaluate prediagnostic microRNAs (miRs) as biomarkers of subsequent PDAC risk. A panel of eight miRs (miR‐10a, ‐10b, ‐21‐3p, ‐21‐5p, ‐30c, ‐106b, ‐155 and ‐212) based on previous evidence from our group was evaluated in 225 microscopically confirmed PDAC cases and 225 controls matched on center, sex, fasting status and age/date/time of blood collection. MiR levels in prediagnostic plasma samples were determined by quantitative RT‐PCR. Logistic regression was used to model levels and PDAC risk, adjusting for covariates and to estimate area under the receiver operating characteristic curves (AUC). Plasma miR‐10b, ‐21‐5p, ‐30c and ‐106b levels were significantly higher in cases diagnosed within 2 years of blood collection compared to matched controls (all p‐values <0.04). Based on adjusted logistic regression models, levels for six miRs (miR‐10a, ‐10b, ‐21‐5p, ‐30c, ‐155 and ‐212) overall, and for four miRs (‐10a, ‐10b, ‐21‐5p and ‐30c) at shorter follow‐up time between blood collection and diagnosis (≤5 yr, ≤2 yr), were statistically significantly associated with risk. A score based on the panel showed a linear dose‐response trend with risk (p‐value = 0.0006). For shorter follow‐up (≤5 yr), AUC for the score was 0.73, and for individual miRs ranged from 0.73 (miR‐212) to 0.79 (miR‐21‐5p).  相似文献   
995.
BACKGROUND: No extensive studies are available in the literature on the eventual skin pathology induced by neurologic or systemic diseases in elderly individuals. Other factors, such as health and hygiene, socioeconomic status, and climate can also play an important role. METHODS: Fifteen-hundred subjects (886 women and 614 men; mean age, 67.8 years; range, 39-90 years) were admitted to the Department of Geriatrics at the Oasi Institute between 1992 and 1997; all these subjects were carefully evaluated from a dermatologic point of view. Each subject underwent specialist examinations, routine blood analyses, thoracic X-rays, cerebral computerized tomography (CT) scan, and magnetic resonance imaging (MRI) when appropriate. A group of subjects without significant neurologic or systemic disease, comprising 116 women and 60 men (mean age, 64.5 years; range, range, 40-90 years), was selected and used as a normal control group. Subsequently, our attention was focused on the eventual presence of the following neurologic diseases: Alzheimer-type dementia, vascular dementia, mixed-type dementia, subcortical dementia, Parkinson's disease, vascular brain disease, hemiplegia, etc. Thus, different subgroups were formed on the basis of such diagnostic categories and the frequency of skin pathology in each subgroup was evaluated. RESULTS: Of the 1500 subjects, 1439 stated that they had never been affected by dermatologic disease. No statistically significant difference in frequency of skin pathology was found between normal controls and the different patient subgroups. Unsuspected and singular dermatoses were found, however, such as paraneoplastic syndromes, idiopathic tripe palms, white fibrous papulosis of the neck as an expression of photoaging, conditions induced by former popular traditions of Sicilian culture (anetoderma secondary to the application of Hirudo medicinalis and erythema ab igne), pigmented dermatoses never described before in Italy (prurigo pigmentosa and friction amyloidosis), and nail abnormalities (atypical half-and-half nail, and dyschromic nail changes in multiple system atrophy and in hemiplegia). CONCLUSIONS: The dermatologic screening performed in 1500 patients revealed several unexpected diagnoses and some original observations. Some rare dermatoses were described and certain hypotheses were suggested to explain the peculiar dyschromic changes of the fingernails in multiple system atrophy, the atypical cases of half-and-half nail, and the so-called idiopathic tripe palms associated with psoriasis.  相似文献   
996.
The pathological process in Alzheimer's disease (AD) involves amyloid beta (Abeta) deposition and neuronal cell degeneration. The neurotoxic Abeta peptide is derived from the amyloid precursor protein (APP), a member of a larger gene family including the amyloid precursor-like proteins, APLP1 and APLP2. The APP and APLP2 molecules contain metal binding sites for copper and zinc. The zinc binding domain (ZnBD) is believed to have a structural rather than a catalytic role. The activity of the copper binding domain (CuBD) is unknown, however, APP reduces copper (II) to copper (I) and this activity could promote copper-mediated neurotoxicity. The expression of APP and APLP2 in the brain suggests they could have an important direct or indirect role in neuronal metal homeostasis. To examine this, we measured copper, zinc and iron levels in the cerebral cortex, cerebellum and selected non-neuronal tissues from APP (APP(-/-)) and APLP2 (APLP2(-/-)) knockout mice using atomic absorption spectrophotometry. Compared with matched wild-type (WT) mice, copper levels were significantly elevated in both APP(-/-) and APLP2(-/-) cerebral cortex (40% and 16%, respectively) and liver (80% and 36%, respectively). Copper levels were not significantly different between knockout and WT cerebellum, spleen or serum samples. There were no significant differences observed between APP(-/-), APLP2(-/-) and WT mice zinc or iron levels in any tissue examined. These findings indicate APP and APLP2 expression specifically modulates copper homeostasis in the liver and cerebral cortex, the latter being a region of the brain particularly involved in AD. Perturbations to APP metabolism and in particular, its secretion or release from neurons may alter copper homeostasis resulting in increased Abeta accumulation and free radical generation. These data support a novel mechanism in the APP/Abeta pathway which leads to AD.  相似文献   
997.
p62/SQSTM1/Sequestosome-1 is an autophagic protein that serves a crucial role in cellular metabolism, proliferation and malignant growth. Notably, autophagy may influence the development and resistance to therapy of numerous types of human cancer. In the present pilot study, the immunohistochemical pattern of p62 was analyzed in a cohort of patients with isocitrate dehydrogenase (IDH)1/2 wild-type glioblastoma (GBM), in primary and recurrent samples, in order to verify the concordance or discordance between the primary and recurrent tumors. In addition, the association between p62, and patient outcome and O6-methylguanine-DNA methyltransferase (MGMT) status was assessed. The results revealed p62 immunoexpression in the nucleus and cytoplasm of neoplastic elements in 45% of primary and 55% of recurrent cases of GBM. A discordant p62 immunoreactivity was detected in 35% of cases, with a variation either with positive or negative conversion of p62 status. Statistically, p62 expression and MGMT status exhibited a significant prognostic value by univariate analysis, whereas only MGMT promoter methylation status emerged as an independent prognostic factor by multivariate analysis. Finally, the most favorable prognosis was documented when the same GBM case was positively concordant for both p62 expression and MGMT methylated status. Since little data are available regarding the association between p62 expression and MGMT in GBM, further investigations may be required to determine if new targeted therapies may be addressed against autophagy-related proteins, such as p62.  相似文献   
998.
Over the last few years, the addition of small amounts of carbon nanotubes (CNTs) to construction materials has become of great interest, since it enhances some of the mechanical, electrical and thermal properties of the cement. In this sense, single-walled and multi-walled carbon nanotubes (SWCNTs and MWCNTs, respectively) can be incorporated into cement to achieve the above-mentioned improved features. Thus, the current study presents the results of the addition of SWCNTs and MWCNTs on the microstructure and the physical properties of the cement paste. Density was measured through He pycnometry and the mass change was studied by thermogravimetric analysis (TGA). The microstructure and the phases were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Finally, the electrical conductivity for different CNT concentrations was measured, and an exponential increase of the conductivity with concentration was observed. This last result opens the possibility for these materials to be used in a high variety of fields, such as space intelligent systems with novel electrical and electronic applications.  相似文献   
999.
Mitochondria participate in the maintenance of cellular homeostasis. Firstly, mitochondria regulate energy metabolism through oxidative phosphorylation. In addition, they are involved in cell fate decisions by activating the apoptotic intrinsic pathway. Finally, they work as intracellular signaling hubs as a result of their tight regulation of ion and metabolite concentrations and other critical signaling molecules such as ROS. Aging is a multifactorial process triggered by impairments in different cellular components. Among the various molecular pathways involved, mitochondria are key regulators of longevity. Indeed, mitochondrial deterioration is a critical signature of the aging process. In this scenario, we will focus specifically on the age-related decrease in CoQ levels, an essential component of the electron transport chain (ETC) and an antioxidant, and how CoQ supplementation could benefit the aging process. Generally, any treatment that improves and sustains mitochondrial functionality is a good candidate to counteract age-related mitochondrial dysfunctions. In recent years, heightened attention has been given to natural compounds that modulate mitochondrial function. One of the most famous is resveratrol due to its ability to increase mitochondrial biogenesis and work as an antioxidant agent. This review will discuss recent clinical trials and meta-analyses based on resveratrol and CoQ supplementation, focusing on how these compounds could improve mitochondrial functionality during aging.  相似文献   
1000.
This study aimed to assess the effectiveness of a two-year intervention based on the Mediterranean diet for the treatment of overweight and obesity in a sample of 51 older people from the Mediterranean city of Alicante (Spain). We also examined the effects of the intervention on psychological well-being. The participants were randomly assigned to the experimental and control groups. The experimental group received group nutritional education sessions, an individualized dietary–nutritional treatment based on a Mediterranean diet, and a physical activity program; the control group received Mediterranean nutritional education in a written format. The experimental group showed a greater loss in weight (p = 0.017) and percentage of fat mass (p = 0.049), and a greater reduction in body mass index (BMI) (p = 0.014) and waist circumference (p = 0.010). Both groups improved their depression scores using the PHQ-9; however, no significant improvement was seen in adherence to the Mediterranean diet (PREDIMED) and anxiety level (GAD-7). These results suggest that a two-year intervention based on the Mediterranean diet allows an older population with overweight or obesity to achieve greater weight loss and a greater decrease in BMI, waist circumference, and fat mass percentage. In relation to psychological well-being, depression levels improved at the end of said intervention.  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