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   5101篇
  免费   352篇
  国内免费   47篇
耳鼻咽喉   45篇
儿科学   113篇
妇产科学   135篇
基础医学   813篇
口腔科学   84篇
临床医学   428篇
内科学   1307篇
皮肤病学   88篇
神经病学   619篇
特种医学   113篇
外科学   463篇
综合类   8篇
一般理论   3篇
预防医学   301篇
眼科学   78篇
药学   428篇
中国医学   9篇
肿瘤学   465篇
  2024年   5篇
  2023年   53篇
  2022年   119篇
  2021年   183篇
  2020年   111篇
  2019年   151篇
  2018年   154篇
  2017年   115篇
  2016年   169篇
  2015年   164篇
  2014年   192篇
  2013年   283篇
  2012年   396篇
  2011年   397篇
  2010年   231篇
  2009年   190篇
  2008年   360篇
  2007年   361篇
  2006年   303篇
  2005年   339篇
  2004年   322篇
  2003年   262篇
  2002年   257篇
  2001年   33篇
  2000年   22篇
  1999年   33篇
  1998年   42篇
  1997年   45篇
  1996年   28篇
  1995年   39篇
  1994年   24篇
  1993年   15篇
  1992年   11篇
  1991年   9篇
  1990年   11篇
  1989年   12篇
  1988年   6篇
  1987年   6篇
  1986年   4篇
  1985年   3篇
  1984年   6篇
  1983年   4篇
  1982年   4篇
  1981年   4篇
  1980年   8篇
  1979年   7篇
  1978年   2篇
  1976年   4篇
  1973年   1篇
排序方式: 共有5500条查询结果,搜索用时 15 毫秒
21.
IntroductionDiabetic patients treated with metformin have a lower risk of developing BC or a better BC prognosis. Metformin might reduce cancer growth through direct antiproliferative effects or through indirect mechanisms, particularly the reduction of insulin. In a randomized study on nondiabetic BC patients in natural menopause with high testosterone levels, we observed a significant decrease in insulin and in testosterone levels with metformin 1500 mg/d compared with 1000 mg/d. We present the results of a new analysis of our study on the effect of metformin on the bioavailability of sex hormones.Patients and MethodsOne hundred twenty-four eligible women were initially invited to take metformin 500 mg/d for 3 months. The 108 women who completed the first 3 months continued the study using 1000 mg/d for 1 month. The women were then randomized into 2 groups, and, for the subsequent 5 months, 1 group increased the dose to 1500 mg/d, and the other group continued with 1000 mg/d.ResultsNinety-six women completed the study, 43 receiving metformin 1500 mg/day, and 53 receiving 1000 mg/day. The women receiving 1500 mg/d showed a greater and significant reduction of free testosterone (?29%) and estradiol (?38%), a borderline significant reduction of estrone and insulin-like growth factor-1, and a nonsignificant reduction of androstenedione. They also showed a nonsignificant increase of dehydroepiandrosterone sulfate.ConclusionMetformin does not interfere with the production of dehydroepiandrosterone sulfate. Besides, it decreases estradiol levels, basically through the reduction of testosterone. These hormonal changes might have clinical relevance.  相似文献   
22.
23.
24.
25.
26.
Background Biliary tract cancers (BTC) are rare but highly aggressive tumours with poor prognosis, usually detected at advanced stages. Herein, we aimed at identifying BTC-specific DNA methylation alterations.Methods Study design included statistical power and sample size estimation. A genome-wide methylation study of an explorative cohort (50 BTC and ten matched non-tumoral tissue samples) has been performed. BTC-specific altered CpG islands were validated in over 180 samples (174 BTCs and 13 non-tumoral controls). The final biomarkers, selected by a machine-learning approach, were validated in independent tissue (18 BTCs, 14 matched non-tumoral samples) and bile (24 BTCs, five non-tumoral samples) replication series, using droplet digital PCR.Results We identified and successfully validated BTC-specific DNA methylation alterations in over 200 BTC samples. The two-biomarker panel, selected by an in-house algorithm, showed an AUC > 0.97. The best-performing biomarker (chr2:176993479-176995557), associated with HOXD8, a pivotal gene in cancer-related pathways, achieved 100% sensitivity and specificity in a new series of tissue and bile samples.Conclusions We identified a novel fully efficient BTC biomarker, associated with HOXD8 gene, detectable both in tissue and bile by a standardised assay ready-to-use in clinical trials also including samples from non-invasive matrices.Subject terms: Diagnostic markers, Biliary tract cancer  相似文献   
27.
Single reports of Guillain-Barré syndrome (GBS) have been reported worldwide during the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. While case reports are likely to be biased toward uncommon clinical presentations, systematic assessment of prospective series can highlight the true clinical features and spectrum. In this prospective, observational study, we included all consecutive patients who developed GBS. In patients with SARS-CoV-2 infection as antecedent, the time-gap between the infection and GBS onset had to be ≤30 days. The referral was a neurological University Research Hospital, in the Italian Region more severely involved by the pandemic, and hospitalizing both COVID+ and non-COVID neurological diseases. Clinical, laboratory, cerebrospinal fluid, and electromyographic features of GBS diagnosed between March 2020 and March 2021 were compared to a retrospective series of GBS diagnosed between February 2019 and February 2020 (control population). Nasopharyngeal swab was still positive at GBS onset in 50% of patients. Mild-to-moderate COVID-related pneumonia, as assessed by X-ray (6 patients) or X-ray plus computerized tomography (2 patients) co-occurred in 6 of 10 patients. GBS diagnosed during the pandemic period, including 10 COVID-GBS and 10 non–COVID-GBS, had higher disability on admission (P = .032) compared to the GBS diagnosed between February 2019 and 2020, possibly related to later hospital referral in the pandemic context. Compared to non–COVID-GBS (n = 10) prospectively diagnosed in the same period (March 2020–2021), post–COVID-GBS (n = 10) had a higher disability score on admission (P = .028), lower sum Medical Research Council score (P = .022) and lymphopenia (P = .025), while there were no differences in GBS subtype/variant, severity of peripheral involvement, prognosis and response to treatment. Cerebrospinal fluid search for SARS-CoV-2 RNA and antiganglioside antibodies were negative in all COVID+ patients. Temporal clustering of cases, coinciding with the waves of the pandemic, and concomitant reduction of the incidence of COVID-negative GBSs may indicate a role for SARS-CoV-2 infection in the development of GBS, although the association may simply be related to a bystander effect of systemic inflammation; lack of prevalence of specific GBS subtypes in post–COVID-GBS also support this view. GBS features and prognosis are not substantially different compared to non–COVID-GBS.  相似文献   
28.
29.
30.
AIM: To re-evaluate the use of CT-guided needle biopsy and VATS, as our combined approach protocol for the diagnosis and treatment of peripheral pulmonary nodules. METHODS AND RESULTS: We describe the case of a male smoking patient, 50-year-old, who came to our service for the histological diagnosis of a right pulmonary lesion incidentally revealed. He was submitted to our diagnostic and therapeutic protocol for peripheral pulmonary nodules, that is a combined approach of CT-guided needle biopsy, anchorage of the lesion and VATS resection. Difficulties with this technique can raise when: 1. the cytological CT-guided needle biopsy is not diagnostic, 2. the anchorage is not successful, 3. the malignancy of the lesion cannot be surely determined by the extemporary histological examination. In this patient all these difficulties were encountered. CONCLUSIONS: We conclude that our diagnostic and therapeutic protocol for peripheral pulmonary nodules is not invalidated by this experience, even in consideration of the fact that we applied successfully the protocol in several previous cases.  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