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   25800篇
  免费   1311篇
  国内免费   177篇
耳鼻咽喉   197篇
儿科学   534篇
妇产科学   440篇
基础医学   2830篇
口腔科学   618篇
临床医学   2072篇
内科学   6772篇
皮肤病学   488篇
神经病学   2995篇
特种医学   779篇
外科学   3890篇
综合类   44篇
一般理论   5篇
预防医学   1087篇
眼科学   452篇
药学   1471篇
中国医学   30篇
肿瘤学   2584篇
  2023年   164篇
  2022年   380篇
  2021年   750篇
  2020年   449篇
  2019年   620篇
  2018年   695篇
  2017年   557篇
  2016年   627篇
  2015年   696篇
  2014年   1017篇
  2013年   1279篇
  2012年   2006篇
  2011年   1997篇
  2010年   1160篇
  2009年   1075篇
  2008年   1752篇
  2007年   1809篇
  2006年   1672篇
  2005年   1653篇
  2004年   1631篇
  2003年   1353篇
  2002年   1323篇
  2001年   191篇
  2000年   118篇
  1999年   153篇
  1998年   250篇
  1997年   210篇
  1996年   194篇
  1995年   170篇
  1994年   128篇
  1993年   131篇
  1992年   113篇
  1991年   89篇
  1990年   88篇
  1989年   67篇
  1988年   68篇
  1987年   65篇
  1986年   59篇
  1985年   56篇
  1984年   80篇
  1983年   45篇
  1982年   47篇
  1981年   44篇
  1980年   34篇
  1979年   21篇
  1978年   17篇
  1977年   31篇
  1976年   17篇
  1974年   15篇
  1973年   16篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
993.
994.
BackgroundItaly has been one of the most affected countries in the world by COVID-19. There has been increasing concern regarding the impact of COVID‐19 on patients with inflammatory bowel disease (IBD), particularly in patients treated with immunosuppressants or biologics. The aim of our study is to understand the incidence of COVID-19 in a large cohort of patients with IBD. Furthermore, we analyzed possible risk factors for infection and severity of COVID-19.MethodsThis was an observational study evaluating the impact of COVID-19 on IBD patients in a single tertiary center. A 23 multiple-choice-question anonymous survey was administered to 1200 patients with IBD between March 10th and June 10th 2020.Results1158 questionnaires were analyzed. The majority of patients had Crohn's disease (CD) (60%) and most of them were in clinical remission. Among the 26 patients (2.2%) who tested positive for COVID-19, only 5 (3CD) were on biological treatment and none required hospitalization. Two patients died and were on treatment with mesalazine only. Of the 1158 patients, 521 were on biological therapy, which was discontinued in 85 (16.3%) and delayed in 195 patients (37.4%). A worsening of IBD symptoms was observed in 200 patients on biological therapy (38.4%). Most of these patients, 189 (94.5%), had stopped or delayed biological treatment, while 11 (5.5%) had continued their therapy regularly (p<0.001).ConclusionsOur data are in line with the current literature and confirm a higher incidence compared to the general population. Biological therapy for IBD seems to not be a risk factor for infection and should not be discontinued in order to avoid IBD relapse.  相似文献   
995.
In this paper, the best laser powder bed fusion (L-PBF) printing conditions for FeSi steels with two different Si content (3.0% and 6.5%) are defined. Results show very strict processing window parameters, following a lack of fusion porosity at low specific energy values and keyhole porosity in correspondence with high specific energy values. The obtained microstructure consists of grains with epitaxial growth starting from the grains already solidified in the underling layer. This allows the continuous growth of the columnar grains, directed parallel to the built direction of the component. The magnetic behaviour of FeSi6.5 samples, although the performances found do not still fully reach those of the best commercial electrical steels (used to manufacture magnetic cores of electrical machines and other similar magnetic components), appears to be quite promising. An improvement of the printing process to obtain thin sheets with increased Si content, less than 0.5 mm thick, with accurate geometry and robust structures, can result to an interesting technology for specific application where complex geometries and sophisticated shapes are required, avoiding mechanical machining processes for electrical steel with high silicon content.  相似文献   
996.
997.
Background: Cryoablation of accessory pathways (APs) is effective and very safe in children, as previously reported by our group. The aim of this retrospective study was to evaluate the current efficacy of 3D non-fluoroscopic cryoablation of right sided APs in children, comparing results obtained with the Ensite VelocityTM and the more recent Ensite PrecisionTM 3D mapping systems. Methods and Results: From January 2016 to December 2019, 102 pediatric patients [mean age 12.5 ± 2.8, 62 males (61% of total cohort)] with right APs underwent 3D non-fluoroscopic transcatheter cryoablation at our Institution. Fifteen (14.7%) patients had previously undergone catheter ablation. Acute procedural success rate was 95.1% (n = 97). No significant differences were detected in acute success rates achieved with Ensite VelocityTM or Ensite PrecisionTM systems nor between manifest (94%) and concealed APs (100%). No permanent complications occurred. During follow-up (428 ± 286 days, median 396 days [interquartile range 179-713]), 19 patients (19.6%) had recurrences. Recurrences were more frequent for parahissian/anterior APs compared to midseptal/posterior and lateral APs (p = 0.043). Recurrences were not related to the Ensite system used. A redo ablation procedure was attempted in 13 cases, 11 cryoablation and 2 radiofrequency ablations: the former was successful in 10 cases out of 11 (90.9%). Conclusion: 3D cryoablation of right-sided APs is associated with a very high acute success rate with limited use of fluoroscopy, resulting in great benefit to the children. Recurrence rates are not high and patients can be retreated with cryo-energy with higher success rates.  相似文献   
998.
999.
In phase III ImPassion130 trial, the addition of immunotherapy to chemotherapy improved overall survival in metastatic triple-negative breast cancer patients. This benefit was significant only in patients harboring PD-L1-positive tumors, suggesting that stratification according to response biomarkers is needed to achieve consistent responses. Besides PD-L1 expression, a variety of potential biomarkers are under investigation for predicting immunotherapy efficacy in breast cancer, such as tumor-infiltrating lymphocytes, gene signatures, tumor mutational burden, microsatellite instability, and gut microbiome. Enriching future trials through these biomarkers could help identifying the population of responders, realizing what has been called precision immunotherapy.  相似文献   
1000.
Prandoni P 《Blood》2005,106(13):4027-4033
Venous thromboembolism (VTE) is a frequent complication in cancer patients and represents an important cause of morbidity and mortality. Especially in patients who have a poor life expectancy, preventing death from pulmonary embolism is the mainstay of treatment. Critically ill patients should promptly be administered thrombolytic drugs. Except for selected patients requiring aggressive therapy, the initial VTE treatment should be conducted with either adjusted-dose unfractionated heparin or fixed-dose low-molecular-weight heparin (LMWH). LMWHs have the potential to greatly simplify the initial treatment of VTE, making the treatment of suitable patients feasible in an outpatient setting. During anticoagulant therapy, cancer patients have a 2- to 4-fold higher risk of recurrent VTE and major bleeding complications when compared with noncancer patients. The long-term administration of LMWH should be considered as an alternative to anti-vitamin K drugs in patients with advanced disease and in those with conditions limiting the use of oral anticoagulants. Prolongation of anticoagulation should be considered for as long as the malignant disorder is active. The evidence of lowered cancer mortality in patients on LMWH has stimulated renewed interest in these agents as antineoplastic drugs and raises the distinct possibility that cancer and thrombosis share common mechanisms.  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