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   16546篇
  免费   1209篇
  国内免费   1088篇
耳鼻咽喉   7篇
儿科学   758篇
妇产科学   125篇
基础医学   1089篇
口腔科学   10篇
临床医学   1584篇
内科学   4543篇
皮肤病学   15篇
神经病学   1406篇
特种医学   781篇
外科学   3102篇
综合类   1915篇
预防医学   595篇
眼科学   23篇
药学   910篇
  9篇
中国医学   213篇
肿瘤学   1758篇
  2024年   36篇
  2023年   302篇
  2022年   674篇
  2021年   835篇
  2020年   668篇
  2019年   608篇
  2018年   610篇
  2017年   441篇
  2016年   684篇
  2015年   648篇
  2014年   1267篇
  2013年   1012篇
  2012年   979篇
  2011年   1117篇
  2010年   857篇
  2009年   951篇
  2008年   943篇
  2007年   1002篇
  2006年   823篇
  2005年   618篇
  2004年   457篇
  2003年   476篇
  2002年   397篇
  2001年   311篇
  2000年   262篇
  1999年   223篇
  1998年   183篇
  1997年   163篇
  1996年   144篇
  1995年   107篇
  1994年   114篇
  1993年   102篇
  1992年   88篇
  1991年   86篇
  1990年   63篇
  1989年   71篇
  1988年   67篇
  1987年   42篇
  1986年   59篇
  1985年   54篇
  1984年   49篇
  1983年   24篇
  1982年   28篇
  1981年   36篇
  1980年   38篇
  1979年   21篇
  1978年   21篇
  1977年   18篇
  1976年   21篇
  1973年   9篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
PurposeThe purpose of this study was to determine whether computed tomography (CT)-based machine learning of radiomics features could help distinguish autoimmune pancreatitis (AIP) from pancreatic ductal adenocarcinoma (PDAC).Materials and MethodsEighty-nine patients with AIP (65 men, 24 women; mean age, 59.7 ± 13.9 [SD] years; range: 21–83 years) and 93 patients with PDAC (68 men, 25 women; mean age, 60.1 ± 12.3 [SD] years; range: 36–86 years) were retrospectively included. All patients had dedicated dual-phase pancreatic protocol CT between 2004 and 2018. Thin-slice images (0.75/0.5 mm thickness/increment) were compared with thick-slices images (3 or 5 mm thickness/increment). Pancreatic regions involved by PDAC or AIP (areas of enlargement, altered enhancement, effacement of pancreatic duct) as well as uninvolved parenchyma were segmented as three-dimensional volumes. Four hundred and thirty-one radiomics features were extracted and a random forest was used to distinguish AIP from PDAC. CT data of 60 AIP and 60 PDAC patients were used for training and those of 29 AIP and 33 PDAC independent patients were used for testing.ResultsThe pancreas was diffusely involved in 37 (37/89; 41.6%) patients with AIP and not diffusely in 52 (52/89; 58.4%) patients. Using machine learning, 95.2% (59/62; 95% confidence interval [CI]: 89.8–100%), 83.9% (52:67; 95% CI: 74.7–93.0%) and 77.4% (48/62; 95% CI: 67.0–87.8%) of the 62 test patients were correctly classified as either having PDAC or AIP with thin-slice venous phase, thin-slice arterial phase, and thick-slice venous phase CT, respectively. Three of the 29 patients with AIP (3/29; 10.3%) were incorrectly classified as having PDAC but all 33 patients with PDAC (33/33; 100%) were correctly classified with thin-slice venous phase with 89.7% sensitivity (26/29; 95% CI: 78.6–100%) and 100% specificity (33/33; 95% CI: 93–100%) for the diagnosis of AIP, 95.2% accuracy (59/62; 95% CI: 89.8–100%) and area under the curve of 0.975 (95% CI: 0.936–1.0).ConclusionsRadiomic features help differentiate AIP from PDAC with an overall accuracy of 95.2%.  相似文献   
2.
Objective To obtain the dendritic cells ( DC)-based vaccine modified by adenovirus containing MUC4 gene , and evaluate the anti-tumor efficacy of DC vaccine to pancreatic tumor cells. Meth-ods The mRNA sequence of tumor associated antigen, MUC4, was obtained from NCBI, and MUC4 se-quence was acquired through the restriction enzyme sites and over lap PCR, then subcloned into adenovirus plasmid to create recombinant adenovirus ( rAd-MUC4) . The DCs were infected by rAd-MUC4 virus and then stimulated the lymph cells from the same donor to induce MUC4 specific cytotoxicity T lympbocytes ( CTL) . The efficacy of CTL was analyzed by LDH releasing assay. Elispot was used to detect the IFN-γ release. Results The recombinant adenovirus containing MUC4 ( sv12) gene was obtained. The MUC4-induced CTL could specifically kill the Capan-1 pancreatic tumor cells [ ( 13. 7±6.0)% , ( 21.4± 4. 7)% , (36.1±9. 5)% at ratios of 10: ,20: ,40: ] , higher than MCF-7 and Bxpc-3 cells respectively, P < 0. 05. The spots number of CTL induced by rAd-MUC4 was ( 139.1±23.3) , more than GFP and PBS control group,P<0.05. Conclusion The Muc4 gene modified DC vaccine could induce the proliferation of CTL, which provided a significant cytotoxicity to HLA-matched MUC4 positive tumor cell lines in vitro.  相似文献   
3.
4.
Neurologic complications are common after transplantation and affect 30-60% of transplant recipients. The etiology of most of the posttransplant neurologic disorders is related to the opportunistic infections, both systemic and involving central nervous system (CNS), toxicity of immunosuppressive medications, and the metabolic insult created by the underlying primary disease and the transplant procedure. Neuroimaging studies are one of the key tools in the evaluation and enable early diagnosis of neurologic complications in transplant patients, especially posterior reversible leukoencephalopathy syndrome, central pontine myelinolysis, intracerebral hemorrhage, and fungal and bacterial abscesses. Magnetic resonance imaging (MRI) is the preferred technique, but each of the available neuroimaging techniques offers a unique insight into the pathophysiologic mechanisms underlying neurologic complications of transplantation. The role of neuroimaging in this population includes early detection of calcineurin inhibitor neurotoxicity, opportunistic infections, neoplasia, metabolic disorders, or cerebrovascular diseases. In addition, we can monitor longitudinal progression of disease and treatment response.  相似文献   
5.
乌司他丁对大鼠胰性脑病保护作用的实验研究   总被引:12,自引:0,他引:12  
目的 :探讨乌司他丁对大鼠急性出血坏死性胰腺炎时对脑组织损害的保护作用 ,为胰性脑病的治疗提供实验依据。方法 :将 90只SD大鼠随机分为正常对照组 ,急性出血坏死性胰腺炎诱导组和乌司他丁处理组 ,经胰胆管逆行注射 5%牛磺胆酸钠建立大鼠ANP模型 ,12h后处死动物 ,测定血清TNFα水平 ,并检测脑组织含水量、脑微血管内白细胞聚集及附壁现象。结果 :经乌司他丁处理后 ,血清中乌司他丁水平、脑组织含水量、脑组织MDA含量、脑微血管内白细胞聚集及附壁现象显著降低(P <0 .0 1)。结论 :乌司他丁可以减轻急性出血坏死性胰腺炎时脑损害的发生和发展  相似文献   
6.
Acute encephalopathy associated with influenza and other viral infections   总被引:7,自引:0,他引:7  
Acute encephalopathy is the most serious complication of pediatric viral infections, such as influenza and exanthem subitum. It occurs worldwide, but is most prevalent in East Asia, and every year several hundreds of Japanese children are affected by influenza-associated encephalopathy. Mortality has recently declined, but is still high. Many survivors are left with motor and intellectual disabilities, and some with epilepsy. This article reviews various syndromes of acute encephalopathy by classifying them into three major categories. The first group caused by metabolic derangement consists of various inherited metabolic disorders and the classical Reye syndrome. Salicylate is a risk factor of the latter condition. The second group, characterized by a systemic cytokine storm and vasogenic brain edema, includes Reye-like syndrome, hemorrhagic shock and encephalopathy syndrome, and acute necrotizing encephalopathy. Non-steroidal anti-inflammatory drugs, such as diclofenac sodium and mephenamic acid, may aggravate these syndromes. Severe cases are complicated by multiple organ failure and disseminated intravascular coagulation. Mortality is high, although methylprednisolone pulse therapy may be beneficial in some cases. The third group, characterized by localized edema of the cerebral cortex, has recently been termed acute encephalopathy with febrile convulsive status epilepticus, and includes hemiconvulsion-hemiplegia syndrome and acute infantile encephalopathy predominantly affecting the frontal lobes. Theophylline is a risk factor of these syndromes. The pathogenesis is yet to be clarified, but an increasing body of evidence points to excitotoxicity and delayed neuronal death.  相似文献   
7.
目的:探讨细胞活素肿瘤坏死因子-α(TNF-α)、SNAP(S-Nitroso-Nacetyl-penicillamine)对胰腺癌细胞产生血管内皮生长因子A、C(VEGF-A、C)的调节.方法:用Northern杂交和Western杂交法分析6种人胰腺癌细胞株中VEGF-A、C基因和蛋白的表达;以TNF-α或SNAP刺激其中两个细胞株后用逆转录-聚合酶链式反应技术(RT-PCR)分析其VEGF-A、C基因的表达.结果:Northern杂交法显示这6种胰腺癌细胞株均有4.1kb VEGF-A基因和2.4kb VEGF-C基因的表达;Western杂交法显示它们均有分子量为43kD的VEGF-A蛋白质和分子量为55kD的VEGF-C蛋白质的表达.RT-PCR分析法显示:TNF-α使细胞株COLO-357产生VEGF-A、VEGF-C mRNA分别减少约1~2.5倍、1~2倍,使细胞株CAPAN-1产生VEGF-A、VEGF-C mRNA分别减少约1倍、1.6~2.5倍;而SNAP刺激细胞株COLO-357产生VEGF-A mRNA增加约5倍,刺激细胞株CAPAN-1产生VEGF-A mRNA增加约4倍,但对这两种细胞株产生VEGF-C mRNA均无明显刺激作用.结论:细胞活素TNF-α和低氧通过调节血管内皮生长因子A、C的表达而影响胰腺癌细胞的生物学特性,抑制癌细胞的增殖,促进其凋亡、死亡或进展、恶化.  相似文献   
8.
胰腺肿瘤的B型超声诊断   总被引:4,自引:0,他引:4  
本文将资料完整的并经手术及病理证实的27例胰腺肿瘤初步小结。详细描述各例肿瘤的临床们诊与诊断、B型超声和手术情况,并重点讨论:临床们诊和B型超声未能检出的肿瘤,检出肿瘤大小较手术所见尺寸的要,10mm~40mm以及未见肿瘤浸润的原因。  相似文献   
9.
The aim of this study was to evaluate the cerebral synthesis of eicosanoids in the asphyctic newborn and to investigate the relation between the prostanoid profiles in cerebrospinal fluid (CSF) and the appearance and severity of hypoxic-ischaemic encephalopathy (HIE). Levels of 6-keto-PGF 1-α, TXB2, PGE2 and PGF2-α in CSF were measured in 40 full term newborns during the first day of life. Thirty of these newborns had birth asphyxia and were divided into three groups: 10 without HIE, 12 with mild HIE and 8 with moderate-severe HIE. They were compared to a control group of 10 non-hypoxic newborns. Determinations of the metabolites in CSF were performed by RIA and expressed as pg/ml (mean ± SD). The CSF TXB2 (thromboxane A2 metabolite) in asphyxiated newborns was always higher than in the control group (28.12 ± 10.6), and related to the severity of HIE ( p = 0:005): without HIE (50.84 ± 16.4; p = 0:02), mild HIE (80.65 ± 12.64; p ± 0:01) and moderate-severe HIE (178.14 ± 20.5; p < 0:01). The CSF 6-keto-PGF 1-α (prostacyclin metabolite) in asphyxiated newborns was always higher than in the control group (80.55 ± 12.56), but indirectly related to the severity of HIE: without HIE (240.95 ± 28.12; p < 0:01), mild HIE (183.65 ± 30.1; p < 0:01) and moderate-severe HIE (140.55 ± 25.12; p < 0:01). In the moderate-severe HIE group, the increase in TXB2 was higher than the rise in 6-keto-PGF 1-α.  相似文献   
10.
薄层动态CT对胰腺癌的早期诊断   总被引:1,自引:0,他引:1  
笔者采用薄层动态CT扫描,诊断直径≤3cm的胰腺癌12例,其直接征象为胰头轻度不规则增大或有小的局部隆起、钩突圆隆变形、胰腺实质的分叶形态消失;间接征象为胰管、胆管的梗阻性扩张。认为薄层动态CT扫描是早期胰腺癌诊断的有效方法。  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