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   24402篇
  免费   1413篇
  国内免费   135篇
耳鼻咽喉   249篇
儿科学   625篇
妇产科学   502篇
基础医学   3668篇
口腔科学   1043篇
临床医学   2175篇
内科学   5662篇
皮肤病学   669篇
神经病学   2133篇
特种医学   562篇
外科学   2203篇
综合类   50篇
一般理论   10篇
预防医学   2333篇
眼科学   477篇
药学   1645篇
中国医学   112篇
肿瘤学   1832篇
  2024年   33篇
  2023年   256篇
  2022年   602篇
  2021年   1023篇
  2020年   611篇
  2019年   818篇
  2018年   929篇
  2017年   643篇
  2016年   769篇
  2015年   838篇
  2014年   1109篇
  2013年   1403篇
  2012年   2192篇
  2011年   2287篇
  2010年   1198篇
  2009年   985篇
  2008年   1684篇
  2007年   1625篇
  2006年   1477篇
  2005年   1366篇
  2004年   1186篇
  2003年   1000篇
  2002年   880篇
  2001年   96篇
  2000年   63篇
  1999年   86篇
  1998年   124篇
  1997年   106篇
  1996年   86篇
  1995年   65篇
  1994年   56篇
  1993年   57篇
  1992年   39篇
  1991年   34篇
  1990年   27篇
  1989年   29篇
  1988年   22篇
  1987年   11篇
  1986年   22篇
  1985年   17篇
  1984年   26篇
  1983年   14篇
  1982年   16篇
  1981年   10篇
  1980年   3篇
  1979年   6篇
  1978年   5篇
  1977年   5篇
  1975年   2篇
  1974年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
We report three cases of well-differentiated neuroendocrine carcinoma originating primarily in the anterior mediastinum which had been initially investigated by fine-needle aspiration cytology in conjunction with immunocytochemistry and subsequently recognized as thymic in origin. Aspirates consisted of loosely cohesive or aggregated medium sized elements with round to oval nuclei and scanty cytoplasm. in all cases the Romanowsky stain provided an excellent delineation of definite paranuclear inclusion-like structures having a semicircular or discoid appearance which appeared to contain cytokeratin by immunocytochemical studies and were very similar to the intermediate filament paranuclear “buttons” found in neuroendocrine Merkel cell carcinoma of the skin. This appears to be a novel cytologic observation for thymic neuroendocrine carcinoma. We discuss the significance of the above cytologic and immunocytochemical findings and their possible role in the diagnosis of thymic neuroendocrine carcinoma by fine-needle aspiration biopsy. © 1995 Wiley- Liss, Inc.  相似文献   
62.
Introduction: Neuropsychiatric systemic lupus erythematosus (NPSLE) is characterized by a heterogeneity of clinical manifestations. The absence of diagnostic criteria and the lack of clinical trials is a challenge in clinical practice.

Areas covered: A literature review was performed to describe epidemiology, characterization (clinical, immunological, and imaging), diagnosis and treatment of NPSLE. Classification criteria have been the first step towards a uniform definition. More recently, different attribution models have been developed to help to determine if the NP event is due to SLE. Disease activity is a major risk factor for NP events. Cytokines and autoantibodies are associated with NP events, however, only a few studies have identified risk factors for individual NP events.

Expert opinion: Further research needs to search for and validate biomarkers for NPSLE and individual NP events, including neuroimaging findings, attribution models, and serologic markers. This will be a fundamental step in planning randomized control trials in the treatment of NPSLE to improve outcome.  相似文献   

63.
Maternal and Child Health Journal - Dietary patterns can influence maternal and child health outcomes. The study aims to characterize dietary patterns during pregnancy as well as to identify their...  相似文献   
64.
Childhood obesity has become a major global health problem. Vitamin D deficiency and poor cardiorespiratory fitness are highly prevalent in children with overweight or obesity, but little is known about their relationships. In this study, we aimed to analyze the relationship between serum 25-hydroxyvitamin D (25(OH)D) and cardiorespiratory fitness parameters in prepubertal obese and overweight children. A cross-sectional design with a sample of 57 prepubertal children, aged 9–11 years, with overweight or obesity was used. The fasting concentration of 25(OH)D was analyzed with a chemiluminescent microparticle immunoassay. Fat and lean body masses were determined by using DXA. Maximal oxygen uptake (VO2max) was measured with the maximal treadmill test. A total of 68.4% of the sample had sufficient levels of 25(OH)D. As expected, their cardiorespiratory fitness was poor compared with that of normal-weight children, but 60% of the group exceeded the median obesity-specific reference values. No differences were found between the sexes for relative VO2max or 25(OH)D levels. Moreover, no correlations were found between 25(OH)D and body composition or cardiorespiratory parameters for sex or vitamin D groups. Vitamin D status seems not to be directly related to body composition or cardiorespiratory fitness in prepubertal overweight or obese children.  相似文献   
65.
66.
Neurosurgical Review - Chordoma is a rare slow-growing neoplastic bone lesion. However, they show an invasive local growth and high recurrence rate, leading to an overall survival rate of 65% at 5...  相似文献   
67.
Annals of Surgical Oncology - Long-term pancreatoduodenectomy (PD) survivors have previously reported favorable quality of life (QoL). However, there has been a paucity of studies utilizing...  相似文献   
68.
The role of tumour suppressor genes in the development of human cancers has been studied extensively. In viral carcinogenesis, the inactivation of suppressor proteins such as retinoblastoma (pRb) and p53, and cellular oncogenes overexpression, such as c-myc, has been the subject of a number of investigations. In uterine-cervix carcinomas, where high-risk human papillomavirus (HPV) plays an important role, pRb and p53 are inactivated by E7 and E6 viral oncoproteins, respectively. However, little is known about the in situ expression of some of these proteins in pre-malignant and malignant cervical tissues. On the other hand, it has also been demonstrated that c-myc is involved in cervical carcinogenesis, and that pRb participates in the control of c-myc gene expression. By using immunostaining techniques, we investigated pRb immunodetection pattern in normal tissues, squamous intraepithelial lesions (SILs) and invasive carcinomas from the uterine cervix. Our data show low pRb detection in both normal cervical tissue and invasive lesions, but a higher expression in SILs. C-Myc protein was observed in most of the cellular nuclei of the invasive lesions, while in SILs was low. These findings indicate a heterogeneous pRb immunostaining during the different stages of cervical carcinogenesis, and suggest that this staining pattern could be a common feature implicated in the pathogenesis of uterine-cervix carcinoma.  相似文献   
69.
Multiple sclerosis (MS) is a T-cell-mediated autoimmune demyelinating disease of the central nervous system (CNS), associated with an altered immunoregulation. Interferon (IFN)-, also known as immune IFN, is a cytokine with several effects on the immune system. Specific IFN- receptors have been found on human lymphocytes, as well as on other cell types (e.g. gliocytes), even in the CNS. The aim of the present study was to evaluate IFN- binding on peripheral blood T-lymphocytes from MS patients, compared with those from healthy subjects. Thirty-two patients were selected according to the classical criteria for definite MS; as controls, 21 healthy subjects were studied. We have found that T-lymphocytes from MS patients bear a significantly smaller amount of IFN- receptors than those from controls [B max: 568, 18 vs 708, 14 (mean, SE) receptors/cell]. Such IFN- binding sites are of the same type in patients and healthy subjects [K d: 1.0, 0.05 vs 0.9, 0.02 (mean, SE) nM]. These findings are discussed in terms of immunopathogenesis of MS, since it has been reported that activated T-lymphocytes have decreased amounts of IFN- receptors.  相似文献   
70.
Summary The influence of respiratory and metabolic acid-base alterations on the myocardial sensitivity to catecholamines was studied in the isolated rat atria. The ability of noradrenaline for increasing the atrial rate was enhanced during alkalosis and conversely, it was decreased by acidosis. These changes in sensitivity shifted the concentration-effect curve for noradrenaline to the right by about 0.5 log unit when the pH was lowered from 7.60 to 7.00. No changes in the maximum attainable response were detected. Essentially the same shifts of the concentration-effect curves were obtained with changes in pH brought about by altering the pCO2 or at constant pCO2. The decrease in the pH produced a similar shift to the right of the concentration-effect curve for isoprenaline, after the extraneuronal uptake inhibition by hydrocortisone and also in atria tissue with low content of endogenous noradrenaline (reserpine-pretreated and newborn rats). The ability of isoprenaline for increasing cyclic AMP levels in atrial tissue was also enhanced by alkalosis and decreased by acidosis. However, the shift to the right of the concentration-effect curve for cyclic AMP induced by the decrease in the pH was greater than the shift detected in the chronotropic-effect curve. In addition a decrease in the maximum increment of cyclic AMP was detected under acidosis, in spite of equal maximal chronotropic response.Our results support the hypothesis that the alterations in the sensitivity to catecholamines induced by the changes in pH are not due to a release of endogenous noradrenaline nor to alterations of the mechanisms which remove catecholamines from the biophase. The fact that cyclic AMP response to catecholamines was also reduced by acidosis strongly suggests that the mechanism(s) involved is located in the earlier steps of the events leading to the chronotropic effect of the -agonists.  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