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   11832篇
  免费   784篇
  国内免费   55篇
耳鼻咽喉   77篇
儿科学   365篇
妇产科学   347篇
基础医学   1663篇
口腔科学   186篇
临床医学   1358篇
内科学   2437篇
皮肤病学   270篇
神经病学   1347篇
特种医学   378篇
外科学   1020篇
综合类   95篇
一般理论   1篇
预防医学   1019篇
眼科学   362篇
药学   652篇
中国医学   26篇
肿瘤学   1068篇
  2024年   15篇
  2023年   134篇
  2022年   222篇
  2021年   453篇
  2020年   289篇
  2019年   416篇
  2018年   392篇
  2017年   314篇
  2016年   360篇
  2015年   369篇
  2014年   481篇
  2013年   689篇
  2012年   985篇
  2011年   998篇
  2010年   525篇
  2009年   427篇
  2008年   763篇
  2007年   788篇
  2006年   684篇
  2005年   590篇
  2004年   590篇
  2003年   528篇
  2002年   529篇
  2001年   58篇
  2000年   50篇
  1999年   80篇
  1998年   92篇
  1997年   66篇
  1996年   53篇
  1995年   46篇
  1994年   47篇
  1993年   43篇
  1992年   37篇
  1991年   44篇
  1990年   20篇
  1989年   26篇
  1988年   20篇
  1987年   27篇
  1985年   26篇
  1984年   28篇
  1983年   20篇
  1982年   31篇
  1981年   32篇
  1980年   32篇
  1979年   19篇
  1978年   23篇
  1977年   17篇
  1976年   16篇
  1975年   16篇
  1974年   17篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
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   
83.
Human cytomegalovirus (CMV) utilizes different glycoproteins to enter into fibroblast and epithelial cells. A trimer of glycoproteins H, L, and O (gH/gL/gO) is required for entry into all cells, whereas a pentamer of gH/gL/UL128/UL130/UL131A is selectively required for infection of epithelial, endothelial, and some myeloid-lineage cells, but not of fibroblasts. Both complexes are of considerable interest for vaccine and immunotherapeutic development but present a conundrum: gH/gL-specific antibodies have moderate potency yet neutralize CMV entry into all cell types, whereas pentamer-specific antibodies are more potent but do not block fibroblast infection. Which cell types and neutralizing activities are important for protective efficacy in vivo remain unclear. Here, we present evidence that certain CMV strains have evolved polymorphisms in gO to evade trimer-specific neutralizing antibodies. Using luciferase-tagged variants of strain TB40/E in which the native gO is replaced by gOs from other strains, we tested the effects of gO polymorphisms on neutralization by monoclonal antibodies (mAbs) targeting four independent epitopes in gH/gL that are common to both trimer and pentamer. Neutralization of fibroblast entry by three mAbs displayed a range of potencies that depended on the gO type, a fourth mAb failed to neutralize fibroblast entry regardless of the gO type, while neutralization of epithelial cell entry by all four mAbs was potent and independent of the gO type. Thus, specific polymorphisms in gO protect the virus from mAb neutralization in the context of fibroblast but not epithelial cell entry. No influence of gO type was observed for protection against CMV hyperimmune globulin or CMV-seropositive human sera, suggesting that antibodies targeting protected gH/gL epitopes represent a minority of the polyclonal neutralizing repertoire induced by natural infection.  相似文献   
84.
非典型性帕金森样病亦称帕金森综合征,为一组临床表现多样的疾病症候群,除了覆盖原发性帕金森病(PD)的主要临床症状[静止性震颤、肌强直、运动不能和(或)运动迟缓、姿势反射障碍]外,还具有进展迅速、对左旋多巴反应不佳或其他特征性表现,如疾病早期易跌倒。与原发性帕金森病相比,非典型性帕金森样病包括原发性神经变性疾病,以及由药物、中毒、代谢性疾病或脑血管事件等导致的继发性症候群,而典型的原发性帕金森病是  相似文献   
85.
Background: Nutritional quality during pregnancy is crucial for mother and child health and their short/long-term outcomes. The aim of this study is to evaluate the adherence to nutritional recommendations in Italy during the three pregnancy trimesters in Normal Weight (NW) and Over Weight (OW) women. Methods: Data from a multicenter randomized controlled trial included 176 women (NW = 133; OW = 43) with healthy singleton pregnancies enrolled within 13 + 6 weeks of gestation. Dietary intake was assessed every trimester by a Food Frequency Questionnaire. Results: OW and NW had similar gestational weight gain. However, as Institute of Medicine (IOM) recommend lower gestational weight gain (GWG) for OW, they exceeded the suggested range. In both groups, caloric intake during the three trimesters never met recommendations. Protein intake in first and second trimester was higher than recommendations, as was sugars percentage. Dietary fiber intake was lower in OW. Polyunsaturated fatty acids, calcium, iron and folic acid requirements were never satisfied, while sodium intake exceeded recommendations. Conclusions: NW and OW women in Italy do not adhere to nutritional recommendations during pregnancy, with lower caloric intake, protein and sugars excess and inadequacies in micronutrients intake. Pregnant women in Italy should be provided with an adequate counseling and educational intervention as well as supplementation when indicated.  相似文献   
86.

Background

Positron emission tomography (PET) as an adjunct to conventional imaging in the staging of pancreatic adenocarcinoma is controversial. Herein, we assess the utility of PET in identifying metastatic disease and evaluate the prognostic potential of standard uptake value (SUV).

Methods

Imaging and follow-up data for patients diagnosed with pancreatic adenocarcinoma were reviewed retrospectively. Resectability was assessed based on established criteria, and sensitivity, specificity, and accuracy of PET were compared to those of conventional imaging modalities.

Results

For 123 patients evaluated 2005–2011, PET and CT/MRI were concordant in 108 (88 %) cases; however, PET identified occult metastatic lesions in seven (5.6 %). False-positive PETs delayed surgery for three (8.3 %) patients. In a cohort free of metastatic disease in 78.9 % of cases, the sensitivity and specificity of PET for metastases were 89.3 and 85.1 %, respectively, compared with 62.5 and 93.5 % for CT and 61.5 and 100.0 % for MRI. Positive predictive value and negative predictive value of PET were 64.1 and 96.4 %, respectively, compared with 75.0 and 88.9 % for CT and 100.0 and 91.9 % for MRI. Average difference in maximum SUV of resectable and unresectable lesions was not statistically significant (5.65 vs. 6.5, p?=?0.224) nor was maximum SUV a statistically significant predictor of survival (p?=?0.18).

Conclusion

PET is more sensitive in identifying metastatic lesions than CT or MRI; however, it has a lower specificity, lower positive predictive value, and in some cases, can delay definitive surgical management. Therefore, PET has limited utility as an adjunctive modality in staging of pancreatic adenocarcinoma.  相似文献   
87.
88.
89.
90.
The World Economic Forum recently released a Global Health Data Charter. The objective of this qualitative case study was to determine if the Charter's eight principles, along with a set of data management practice standards, could be used as an assessment tool to determine the maturity of data management practices within a health organization. The Health Authority — Abu Dhabi (HAAD) — represented the bounded holistic case for this study. The data collection methods included structured interviews, completion of an assessment tool, and electronic documentation review. The findings demonstrated good to excellent compliance between HAAD's data management practices and the Charter principles, indicating a high level of data management maturity. Applying the Charter as the assessment framework proved to be successful. This framework provided a simple yet comprehensive approach to rapidly determine HAAD's level of health data management maturity. This assessment tool may prove to be useful for other health organizations.  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