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   4297篇
  免费   223篇
  国内免费   35篇
耳鼻咽喉   45篇
儿科学   58篇
妇产科学   53篇
基础医学   581篇
口腔科学   118篇
临床医学   321篇
内科学   1325篇
皮肤病学   97篇
神经病学   367篇
特种医学   98篇
外科学   628篇
综合类   21篇
一般理论   1篇
预防医学   198篇
眼科学   68篇
药学   268篇
中国医学   9篇
肿瘤学   299篇
  2023年   28篇
  2022年   70篇
  2021年   99篇
  2020年   64篇
  2019年   80篇
  2018年   111篇
  2017年   70篇
  2016年   81篇
  2015年   104篇
  2014年   158篇
  2013年   190篇
  2012年   286篇
  2011年   287篇
  2010年   172篇
  2009年   153篇
  2008年   289篇
  2007年   301篇
  2006年   271篇
  2005年   305篇
  2004年   281篇
  2003年   260篇
  2002年   216篇
  2001年   37篇
  2000年   30篇
  1999年   35篇
  1998年   37篇
  1997年   33篇
  1996年   37篇
  1995年   46篇
  1994年   31篇
  1993年   28篇
  1992年   36篇
  1991年   24篇
  1990年   21篇
  1989年   14篇
  1988年   21篇
  1987年   27篇
  1986年   14篇
  1985年   7篇
  1984年   21篇
  1983年   18篇
  1982年   19篇
  1981年   9篇
  1980年   8篇
  1979年   7篇
  1977年   9篇
  1976年   7篇
  1975年   10篇
  1974年   7篇
  1944年   5篇
排序方式: 共有4555条查询结果,搜索用时 15 毫秒
71.
72.
73.
To test a prediction of our previous computational model of cortico‐hippocampal interaction (Gluck and Myers [1993, 2001]) for characterizing individual differences in category learning, we studied young healthy subjects using an fMRI‐adapted category‐learning task that has two phases, an initial phase in which associations are learned through trial‐and‐error feedback followed by a generalization phase in which previously learned rules can be applied to novel associations (Myers et al. [2003]). As expected by our model, we found a negative correlation between learning‐related hippocampal responses and accuracy during transfer, demonstrating that hippocampal adaptation during learning is associated with better behavioral scores during transfer generalization. In addition, we found an inverse relationship between Blood Oxygenation Level Dependent (BOLD) activity in the striatum and that in the hippocampal formation and the orbitofrontal cortex during the initial learning phase. Conversely, activity in the dorsolateral prefrontal cortex, orbitofrontal cortex and parietal lobes dominated over that of the hippocampal formation during the generalization phase. These findings provide evidence in support of theories of the neural substrates of category learning which argue that the hippocampal region plays a critical role during learning for appropriately encoding and representing newly learned information so that that this learning can be successfully applied and generalized to subsequent novel task demands. Hum Brain Mapp 35:3122–3131, 2014. © 2013 Wiley Periodicals, Inc .  相似文献   
74.
Renalase is a novel flavoprotein, highly expressed in kidney and heart, which metabolizes catecholamines and catecholamine-like substances via a superoxide (O2)-dependent mechanism using nicotinamide adenine dinucleotide (NADH) as a cofactor. Its mechanism of action is distinct from that of monoaminooxidases A and B, because it oxidizes catecholamines (epinephrine>>L-DOPA>dopamine = norepinephrine) to aminochrome, and the reaction rate increases ~4- to 6-fold in presence of NADH. Tissue and plasma renalase levels are decreased in animal models of chronic kidney disease, and renalase deficiency is associated with increased blood pressure and elevated circulating catecholamines. Renalase plasma levels, measured by enzyme-linked immunosorbent assay, are reported to be ~ 5-fold higher in patients with end-stage renal disease than in normal control subjects. They were also increased in kidney and heart transplant recipients, and inversely correlated with estimated glomerular filtration rate. Renalase has potential therapeutic applications. Experimental models demonstrate that the chronic administration of renalase decreases ambulatory blood pressure and prevents the development of cardiac hypertrophy in rats, and that its acute administration decreases ischemic acute kidney injury in mice. Here we provide a detailed review of renalase biology including its mechanism of action, secretion into blood, interaction with the renal dopamine and epinephrine system, and early studies evaluating its association with outcomes related to hypertension and target-organ injury.  相似文献   
75.
76.
77.
The association between inflammation, platelets, and patent ductus arteriosus (PDA) has not been studied so far. The purpose of this study was to evaluate whether C-reactive protein (CRP) is related to low platelet count and PDA. This was a retrospective study of 88 infants with a birth weight ≤1500 g and a gestational age ≤30 weeks. Platelet count, CRP, and an echocardiogram were assessed in all infants. The subjects were matched by sex, gestational age, and birth weight. Differences were compared using the χ2, t-test, or Mann–Whitney U-test, as appropriate. Significant variables were entered into a logistic regression model. The association between CRP and platelets was evaluated by correlation and regression analysis. Platelet count (167 000 vs. 213 000 µl?1, p = 0.015) was lower and the CRP (0.45 vs. 0.20 mg/dl, p = 0.002) was higher, and the platelet count correlated inversely with CRP (r = ?0.145, p = 0.049) in the infants with vs. without PDA. Only CRP was independently associated with PDA in a logistic regression model (OR 64.1, 95% confidence interval 1.4–2941, p = 0.033).  相似文献   
78.
79.
Malignant mesothelioma is a rare malignancy with a poor prognosis whose development is related to asbestos fiber exposure. An increasing role of genetic predisposition has been recognized recently. Pleural biopsy is the gold standard for diagnosis, in which the identification of pleural invasion by atypical mesothelial cell is a major criterion. Pleural effusion is usually the first sign of disease; therefore, a cytological specimen is often the initial or the only specimen available for diagnosis. Given that reactive mesothelial cells may show marked atypia, the diagnosis of mesothelioma on cytomorphology alone is challenging. Accordingly, cell block preparation is encouraged, as it permits immunohistochemical staining. Traditional markers of mesothelioma such as glucose transporter 1 (GLUT1) and insulin-like growth factor 2 mRNA-binding protein 3 (IMP3) are informative, but difficult to interpret when reactive proliferations aberrantly stain positive. BRCA1-associated protein 1 (BAP1) nuclear staining loss is highly specific for mesothelioma, but sensitivity is low in sarcomatoid tumors. Cyclin-dependent kinase inhibitor 2A (CDKN2A)/p16 homozygous deletion, assessed by fluorescence in situ hybridization, is more specific for mesothelioma with better sensitivity, even in the sarcomatoid variant. The surrogate marker methylthioadenosine phosphorylase (MTAP) has been found to demonstrate excellent diagnostic correlation with p16. The purpose of this review is to provide an essential appraisal of the literature regarding the diagnostic value of many of these emerging biomarkers for malignant mesothelioma in effusion cytology.  相似文献   
80.
BackgroundOutcomes of newly diagnosed multiple myeloma (NDMM) in developing regions have not paralleled those in developed settings. Economic disadvantage, comorbidities, and aggressive disease behavior play competing roles on defining outcomes. Our aim was to analyze the impact of socioeconomic characteristics and comorbidities on therapy initiation, drug selection, and survival outcomes of NDMM in a resource-constrained setting.Patients and MethodsThis retrospective single-center cohort included ≥ 18-year-old NDMM patients from January 2006 to December 2018.ResultsA total of 245 patients were included with a median age of 62 years, Eastern Cooperative Oncology Group performance status ≤ 2 in 70.2%, International Staging System score ≥ 2 in 89.4%, and high-risk disease in 31.6%. Comorbidities were reported in 69.4%, and Charlson comorbidity index (CCI) was ≥ 2 in 64.1%. A total of 87.4% (n = 214) received thalidomide-, alkylating-, and bortezomib-based induction in 67.8%, 18.2%, and 13.1%. Patient-related factors including performance status, comorbidities, and CCI, but not myeloma-related factors, were associated with a decreased likelihood of initiating induction therapy. On multivariate analysis, CCI ≥ 2 remained statistically significant (odds ratio, 5.81; P = .005). Overall survival was 44 months. Although both patient- and myeloma-related factors were associated with a decreased overall survival, only International Staging System score > 2 (hazard ratio, 3.53; P = .004) and induction without bortezomib-based regimens (hazard ratio, 4.45; P < .001) were statistically significant on multivariate analysis.ConclusionMyeloma- and treatment-related factors are the main determinants of survival in NDMM induction-eligible patients. Patient-related factors play a pivotal role determining access to therapy and survival outcomes. Comorbidity index and performance status were determinant on defining therapy initiation in this real-world population, which emphasizes the need to improve health baseline conditions in resource-constrained settings.  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