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   3007篇
  免费   182篇
  国内免费   23篇
耳鼻咽喉   14篇
儿科学   70篇
妇产科学   55篇
基础医学   495篇
口腔科学   67篇
临床医学   330篇
内科学   666篇
皮肤病学   41篇
神经病学   283篇
特种医学   79篇
外科学   329篇
综合类   19篇
预防医学   240篇
眼科学   43篇
药学   171篇
中国医学   3篇
肿瘤学   307篇
  2024年   7篇
  2023年   42篇
  2022年   43篇
  2021年   86篇
  2020年   69篇
  2019年   94篇
  2018年   92篇
  2017年   83篇
  2016年   86篇
  2015年   85篇
  2014年   154篇
  2013年   179篇
  2012年   225篇
  2011年   285篇
  2010年   150篇
  2009年   138篇
  2008年   235篇
  2007年   224篇
  2006年   175篇
  2005年   171篇
  2004年   130篇
  2003年   118篇
  2002年   93篇
  2001年   11篇
  2000年   12篇
  1999年   21篇
  1998年   24篇
  1997年   23篇
  1996年   19篇
  1995年   18篇
  1994年   13篇
  1993年   13篇
  1992年   12篇
  1991年   4篇
  1989年   3篇
  1988年   3篇
  1987年   5篇
  1986年   5篇
  1985年   4篇
  1984年   10篇
  1983年   4篇
  1982年   7篇
  1981年   3篇
  1977年   2篇
  1975年   3篇
  1974年   2篇
  1972年   2篇
  1969年   2篇
  1968年   2篇
  1955年   2篇
排序方式: 共有3212条查询结果,搜索用时 296 毫秒
991.
992.
993.
994.
The diagnosis of hepatitis B e antigen (HBeAg)-negative chronic hepatitis B indicating therapeutic intervention currently requires serum hepatitis B virus (HBV) DNA >or=2,000 IU/mL. We evaluated the severity of liver histology and the presence of histological indication for treatment in patients with HBeAg-negative chronic HBV infection focusing on those with low viremia and/or normal alanine aminotransferase (ALT). In total, 399 patients with increased ALT and detectable serum HBV DNA (chronic hepatitis B patients) and 35 cases with persistently normal ALT and HBV DNA >2,000 IU/mL (inactive carriers) were included. Histological indication for treatment (grading score >or=7 and/or stage >or=2 in Ishak's classification) was found in 91% (185/203), 82% (75/91), 75% (47/63), and 62% (26/42) of chronic hepatitis B patients with HBV DNA >or=200,000, 20,000-199,999, 2,000-19,999, and <2,000 IU/mL, respectively (P < 0.001). Histological indication for treatment was more frequent in chronic hepatitis B patients with persistently elevated ALT (86% or 275/321), but it was also found in 74% (58/78) of those with transiently normal ALT (P = 0.025). All inactive carriers had HBV DNA <20,000 IU/mL. Histological indication for treatment was present in 17% (6/35) of inactive carriers always due to moderate (stage 2) fibrosis without active necroinflammation. CONCLUSION: HBeAg-negative chronic HBV patients with persistently or transiently increased ALT and HBV DNA >or=20,000 IU/mL almost always require therapeutic intervention, but histological indications for treatment are also present in the majority of such cases with HBV DNA <20,000 and even <2,000 IU/mL. In contrast, minimal histological lesions are observed in the majority of HBeAg-negative patients with persistently normal ALT and HBV DNA >2,000 IU/mL, who may not require immediate liver biopsy and treatment but only close follow-up.  相似文献   
995.
BACKGROUND: In clinical trials, canarypox ALVAC-human immunodeficiency virus (HIV) vaccines have been shown to elicit human HIV-specific cytotoxic T lymphocyte (CTL) responses in some but not all healthy uninfected adults.Methods. A clinical trial was conducted to examine whether the vaccine vCP1452 would elicit a greater HIV-specific CTL response when given at a dose of 10(8.0) TCID50 (60 participants) than when given at the regular dose, 10(7.26) TCID50 (40 participants); as a control, a placebo vaccine preparation also was administered (10 participants). RESULTS: Two weeks after the last vaccination in a series, HIV-specific CTL responses were not significantly different when measured by either chromium-release assay (8% and 16% in the high- and regular-dose recipients, respectively) or interferon- gamma ELISpot assay (8% and 15% in the high- and regular-dose recipients, respectively); moreover, recipients of the higher dose had greater local and systemic reactions (P<.001). CONCLUSIONS: High reactogenicity associated with an increased dose of vCP1452 negates the need for further evaluation of this strategy to boost the frequency of HIV-specific CTL response in seronegative human subjects. Development of highly immunogenic canarypox vectors requires further work to optimize vector and insert design, as well as novel ways to increase dosage and to reduce reactogenicity.  相似文献   
996.
Selective protein degradation targeted by members of the F-box protein family plays pivotal roles in cell biology. It is widely accepted that an F-box protein directs substrate ubiquitination within a Skp1.CUL1.F-box protein.ROC1 (SCF-ROC1) E3 ubiquitin ligase complex. This assembly utilizes the CUL1 molecular scaffold, allowing the F-box protein to position its bound substrate for ubiquitination by a ROC1-recruited E2-conjugating enzyme. Here, we describe an alternative mechanism for assembling an F-box protein-based E3 complex through a previously uncharacterized cullin, CUL7, identified by mass spectrometry as a ROC1-interacting protein. CUL7 is a large polypeptide containing a cullin domain, which is responsible for ROC1 binding, and a DOC domain, which is also present in the anaphase-promoting complex. Remarkably, CUL7 assembles an SCF-ROC1-like E3 ubiquitin ligase complex consisting of Skp1, CUL7, the Fbx29 F-box protein, and ROC1. In contrast to CUL1 that binds Skp1 by itself, CUL7 interacts with the Skp1.Fbx29 complex, but not with Skp1 alone. Strikingly, CUL7 selectively interacts with Skp1.Fbx29 but not with Skp1.betaTRCP2 or Skp1.Skp2. Thus, CUL7 may define a previously uncharacterized, Fbx29-mediated, and ubiquitin-dependent proteolysis pathway.  相似文献   
997.
Infliximab for steroid-refractory acute GVHD: a case series   总被引:3,自引:0,他引:3  
Acute and chronic graft-versus-host disease (GVHD) remain major barriers to successful hematopoietic stem cell transplantation (SCT). TNF-alpha has been implicated in the pathogenesis of GVHD and TNF-alpha blockade has been explored for treatment of GVHD. The development of a chimeric mouse/human monoclonal antibody (infliximab) which binds to cells producing TNF-alpha, allowing for not only the neutralization of TNF-alpha but also lysis of the cells producing the TNF-alpha, makes this an attractive drug to explore in GVHD. We report on 11 patients with acute GVHD who were treated with infliximab after failing other therapies. The survival was very poor, in keeping with previously published reports of steroid-refractory acute GVHD. Two patients with severe diarrhea from acute GI GVHD resolved their symptoms after treatment with infliximab. Only these two patients survived. It appears that of all acute GVHD manifestations, gastrointestinal GVHD may be more responsive to treatment with infliximab than others. Caution is recommended when using this agent since it may exacerbate active infections, particularly aspergillosis. Furthermore, we do not know the correct dose or schedule to use with this drug. Given these data, controlled studies assessing dose and timing of administration may be warranted to study infliximab in acute GVHD.  相似文献   
998.
999.

Introduction and objectives

Despite the established diagnostic value of the electrocardiogram in preparticipation screening of athletes, some cardiac structural changes can be missed, particularly in early disease stages. The aim of this study was to evaluate the prevalence of cardiac structural changes via the systematic use of echocardiography in preparticipation screening of competitive athletes.

Methods

Professional athletes or participants in a competitive athletic program underwent a screening that included family and personal medical history, physical examination, electrocardiography, exercise testing, and Doppler echocardiography.

Results

A total of 2688 athletes (67% men; mean age [standard deviation], 21 [10] years) were included. Most of the echocardiographic evaluations (92.5%) were normal and only 203 (7.5%) showed changes; the most frequent change was left ventricular hypertrophy, seen in 50 athletes (1.8%). Cessation of athletic activity was indicated in 4 athletes (0.14%): 2 for hypertrophic cardiomyopathy (electrocardiography had shown changes that did not meet diagnostic criteria), 1 pectus excavatum with compression of the right ventricle, and 1 significant pulmonary valve stenosis; the rest of the changes did not entail cessation of athletic activity and only indicated periodic monitoring.

Conclusions

Although rare, some cardiac structural changes can be missed on physical examination and electrocardiography; in contrast, they are easily recognized with echocardiography. These findings suggest the use of echocardiography in at least the first preparticipation screening of competitive athletes to improve the effectiveness of programs aimed at preventing sudden death in athletes.Full English text available from:www.revespcardiol.org/en  相似文献   
1000.

Background–aim

Recent LBBB in connective tissue diseases (CTDs) is challenging, due to high incidence of underlying pathology that may remain undetected, due to limitations of imaging tests. We hypothesized that cardiovascular magnetic resonance (CMR) may be of diagnostic value in CTDs with recent LBBB and normal echocardiogram.

Patients–methods

26 CTDs, aged 32 ± 7 yrs (19 F) and 26 controls without CTDs, aged 60 ± 4 yrs (10 F) with recent LBBB and normal echo were evaluated by CMR. The CTDs included 6 sarcoidosis (SRC), 4 systemic sclerosis (SSc), 6 systemic lupus erythematosus (SLE), 6 rheumatoid arthritis (RA) and 4 inflammatory myopathies (IM). CMR was performed by 1.5 T. LVEF, T2 ratio (oedema imaging) and late gadolinium enhancement (LGE) (fibrosis imaging) were evaluated. Acute and chronic lesions were characterised by T2 > 2 and positive LGE and T2 < 2 and positive LGE, respectively. According to LGE, lesions were characterised as diffuse subendo-, subepicardial/intramural not following and subendocardial/transmural following the distribution of coronaries, indicative of vasculitis, myocarditis and myocardial infarction, respectively.

Results

CTDs were younger (p < 0.001), with higher incidence of abnormal CMR (42.31 vs 30.77%, p = NS), including dilated cardiomyopathy (11.54%), diffuse subendocardial fibrosis (11.54%), myocardial infarction (7.69%) and acute myocarditis (11.54%) vs dilated cardiomyopathy (19.23%), myocardial infarction (7.69%) and acute myocarditis (3.85%), detected in non-CTDs.

Conclusions

In CTDs with recent LBBB, CMR documented acute and chronic cardiac pathology, particularly myocarditis. CMR should be considered as an adjunct to conventional diagnostic workup in both patient groups, more so in CTDs.  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