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   1263篇
  免费   59篇
  国内免费   4篇
耳鼻咽喉   32篇
儿科学   68篇
妇产科学   48篇
基础医学   86篇
口腔科学   52篇
临床医学   135篇
内科学   230篇
皮肤病学   40篇
神经病学   73篇
特种医学   85篇
外科学   220篇
综合类   18篇
预防医学   43篇
眼科学   59篇
药学   66篇
中国医学   2篇
肿瘤学   69篇
  2024年   1篇
  2023年   16篇
  2022年   19篇
  2021年   52篇
  2020年   35篇
  2019年   36篇
  2018年   36篇
  2017年   32篇
  2016年   39篇
  2015年   45篇
  2014年   50篇
  2013年   77篇
  2012年   82篇
  2011年   87篇
  2010年   62篇
  2009年   45篇
  2008年   99篇
  2007年   105篇
  2006年   92篇
  2005年   81篇
  2004年   64篇
  2003年   70篇
  2002年   58篇
  2001年   16篇
  2000年   3篇
  1999年   3篇
  1998年   3篇
  1997年   4篇
  1996年   2篇
  1995年   2篇
  1994年   7篇
  1993年   1篇
  1988年   1篇
  1987年   1篇
排序方式: 共有1326条查询结果,搜索用时 15 毫秒
1.
The Human Leukocyte Antigen (HLA) typing of large groups of patients with various autoimmune diseases has demonstrated that some HLA alleles occur at higher frequencies in specific diseases than in the general population. Chronic urticaria has been shown to have an autoimmune basis by a previous study which found an association between chronic urticaria and specific HLA groups. We investigated the HLA subtypes of Turkish chronic urticaria patients. For this purpose 42 Turkish patients with chronic urticaria and 115 healthy controls were typed for HLA-DR and DQ by PCR-SSP (Polymerase Chain Reaction Sequence Specific Primers) low resolution DNA technique. We found an increased frequency of DR4 (42.9%, p=0.01) in chronic urticaria patients in comparison with that in healthy controls. This study supports the hypothesis that HLA alleles may be involved in the pathogenesis of chronic urticaria and that they appear to be directly involved in the initiation of the immune response.  相似文献   
2.
Whole-body UV-B phototherapy has been used for the treatment of graft-versus-host disease (GVHD) of the skin and has systemic immunosuppressive and tolerogenic effects. We hypothesized that whole-body UV-B therapy would improve donor engraftment and decrease the incidence and severity of GVHD that is associated with decreased intensity allogeneic hematopoietic stem cell transplantation. This study tested the feasibility of using UV-B phototherapy that was initiated before grafting and continued until engraftment to determine its effect on transplantation outcome. Eight patients (median age, 55.5 years; range, 32-65 years) with hematologic malignancies were included. Allogeneic peripheral blood stem cells were obtained from matched related (n=5) or matched unrelated (n=3) donors. Conditioning regimen was fludarabine 30 mg/m2 intravenously for 5 days, cyclophosphamide 1 g/m2/d intravenously for 2 days, and equine antithymocyte globulin 30 mg/kg/d for 2 days. GVHD prophylaxis included cyclosporine, methylprednisolone, and escalating doses of narrowband UV-B (311 nm) according to skin tolerance, 3 days a week, from 10 days before to 28 days after transplantation. The conditioning regimen and the UV-B therapy were well tolerated. Two patients received all 14 prescribed UV-B treatments (cumulative doses of 2000 and 3260 mJ/cm2, respectively) and 6 patients received 8 to 13 treatments with a cumulative dose range of 528-3465 mJ/cm2. There was a rapid decrease in epidermal CD1a+ cells by day of transplantation. Myeloid engraftment was rapid. One patient had secondary engraftment failure at 3 months and another had mixed chimerism at day 100. Seven of 8 patients developed severe acute GVHD (grade III, n=5; grade IV, n=2). Six had skin involvement, 5 had gastrointestinal involvement, and 1 had liver involvement. Four patients died (2 from sepsis, 1 from acute GVHD, and 1 from chronic GVHD). Four patients are alive (130-287 days), 3 with extensive chronic GVHD. We conclude that extended peritransplant UV-B therapy at the standard minimally erythemogenic dose is detrimental to the outcome of allogeneic stem cell transplantation. It is unclear how UV-B at this immunsuppressive dose might have altered skin and systemic cytokine and immune cell compositions in the host and increased GVHD- and treatment-related mortalities. Different UV-B dose and schedules should be further explored. However, although other phototherapeutic modalities may be effective against GVHD, extended UV-B therapy should not be used during early phases of decreased conditioning allogeneic transplantation.  相似文献   
3.
4.
Introduction: Chronic progressiveexternal ophthalmoplegia is characterisedby limitation of ocular motility in alldirections of gaze and ptosis.Innervational or myogenic factors wereclaimed to be responsible for thismotility disorder. The aim of thisstudy was toinvestigate the extraocular muscles inCPEO with computerized tomography in an attemptto distinguish extraocular musclemorphology caused by this disorderfrom that occurring in normal individuals.Methods: Eighteen orbits from 9patients diagnosed with CPEOwere included in the study. Axialand coronal scans were obtained for CTevaluation of extraocular muscles and thedimensions of extraocular muscles were measured.The control group consisted of40 orbits belonging to 20 individuals and,the results were compared with a student'st test.Results: The thickness (the verticaldimension of vertical recti and thehorizontal dimension of horizontal recti)of all rectus muscles wassignificantly decreased in comparison with the controlgroup, whereas the width (the horizontal dimensionof vertical recti and the verticaldimension of horizontal recti) was similar inboth the diseased and normal orbits.In all the rectus musclesof the diseased orbits,the normal fusiform shape was lost and the muscles appeared asthin bands.Discussion: The differentiation ofCPEO from other myogenic and neurogenicdisorders may present difficulty,and a cluster of criteria are required fora final diagnosis. CT has provento be a valuable tool in assessing extraocularmuscles [1, 2]. In this study, an extremeatrophy of all rectus muscles wasdemonstrated by means of CT. This diagnostic method mayconsequently contribute to a properdiagnosis of CPEO.  相似文献   
5.
Nitrogen doped carbon nanoparticles on highly porous carbon nanofiber electrodes were successfully synthesized via combining centrifugal spinning, chemical polymerization of pyrrole and a two-step heat treatment. Nanoparticle-on-nanofiber morphology with highly porous carbon nanotube like channels were observed from SEM and TEM images. Nitrogen doped carbon nanoparticles on highly porous carbon nanofiber (N-PCNF) electrodes exhibited excellent cycling and C-rate performance with a high reversible capacity of around 280 mA h g−1 in sodium ion batteries. Moreover, at 1000 mA g−1, a high reversible capacity of 172 mA h g−1 was observed after 300 cycles. The superior electrochemical properties were attributed to a highly porous structure with enlarged d-spacings, enriched defects and active sites due to nitrogen doping. The electrochemical results prove that N-PCNF electrodes are promising electrode materials for high performance sodium ion batteries.

Nitrogen doped carbon nanoparticles on highly porous carbon nanofiber electrodes were successfully synthesized via combining centrifugal spinning, chemical polymerization of pyrrole and a two-step heat treatment.  相似文献   
6.
Clinical and Experimental Medicine - Breast cancer (BC) is the leading cause of cancer deaths in women. One of the reasons for the failure of BC treatment is reportedly the ineffectiveness of...  相似文献   
7.
8.
Drug-resistant tuberculosis is a serious problem throughout the world. Resistance to Rifampicin (RIF) is mainly caused by the mutations in the rpoB gene coding the beta-subunit of RNA polymerase. In this study, we aimed to detect the distribution of rpoB gene mutations in 80 RIF-resistant clinical Mycobacterium tuberculosis (MTB) isolates from Turkey. The rpoB gene was amplified by PCR and mutations leading to RIF resistance were determined by automated sequence analysis. A total of 72 of the 80 isolates (90%) were found to carry mutations in the amplified region, whereas eight isolates (10%) carried no mutations. Overall, 24 different missense mutations affecting 14 codons, and two deletion mutants were identified. Nine new mutations, six in the hot-spot region and three outside this region, were found. The codon numbers of the most frequently encountered mutations were 531 (51.4%), 526 (18.1%), 516 (13.9%), and 513 (12.5%). As a result, 90% of the RIF-resistant MTB isolates from the Turkish patients were found to carry a mutation in the rpoB gene, Ser531Leu being the most frequent one. Although molecular methods identify mutations leading to RIF resistance very quickly, results of the antimycobacterial susceptibility tests must be taken into consideration for the patients carrying no mutations in this region.  相似文献   
9.
Previous studies showed oxidative stress had an important impact on osteoclastic and osteoblastic functions. Oxidative stress or low levels of antioxidants are supposed to reduce BMD and cause osteoporosis. hcy, gamma glutamyltransferase (GGT), uric acid, albumin and total bilirubin are simple laboratory parameters that are related with oxidative stress. In this study we compare the serum hcy and antioxidant levels in patients with osteoporosis, osteopenia and control subjects. A total of 2190 elderly persons (1348 patients with osteoporosis, 643 patients with osteopenia and 199 control subjects) who were referred to the outpatient clinic of the Department of Internal Medicine, Division of Geriatric Medicine at Hacettepe University Hospital for comprehensive geriatric assessment were included in this cross-sectional study. Mean age of subjects were 72.30±6.34 in osteoporosis group, 71.92±6.90 in osteopenia and 71.86±5.88 in control group (p: 0.260). Multivariate regression analysis revealed that hypertension (HT) (OR: 0.675, 95% CI: 0.534-0.854, p: 0.001), diabetes mellitus (DM) (OR: 1.669, 95% CI: 1.301-2.142, p: <0.001), age (OR: 1.025, 95% CI: 1.006-1.044, p: 0.009), male gender (OR: 0.451, 95% CI: 0.358-0.569, p<0.001), uric acid (OR: 0.893, 95% CI: 0.837-0.952, p: 0.001), hcy (OR: 1.042, 95% CI: 1.023-1.061, p<0.001), albumin (OR: 0.521, 95% CI: 0.376-0.724, p<0.001), GGT (OR: 1.010, 95% CI: 1.003-1.017, p: 0.003), creatinine (OR: 0.630, 95% CI: 0.459-0.864, p: 0.004) were independent variables predicting the occurrence of osteoporosis. This study shows there is an imbalance between natural antioxidative and oxidative markers in patients with osteoporosis. Higher serum uric acid and albumin levels are associated with a lower prevalence of osteoporosis whereas higher hcy and GGT levels are associated lower BMD and higher osteoporosis prevalence.  相似文献   
10.
OBJECTIVES: To compare endothelial function of people with Alzheimer's disease (AD) with that of people without. DESIGN: Case-control study. SETTING: Geriatric medicine outpatient clinic of a university hospital. PARTICIPANTS: Twenty-five patients with AD who were free of vascular risk factors and 24 healthy elderly controls were enrolled. Exclusion criteria were diabetes mellitus, hypertension, dyslipidemia, evident stroke, smoking, documented coronary artery disease, history of myocardial infarction, heart failure, acute or chronic infection, malignancy, peripheral artery disease, renal disease, rheumatologic diseases, alcohol abuse, and certain drugs that may affect endothelial function. Both groups underwent comprehensive geriatric assessment and neuropsychiatric assessment. MEASUREMENTS: Endothelial function was evaluated according to flow-mediated dilation (FMD) from the brachial artery. RESULTS: Mean age +/- standard deviation was 78 +/- 5.9 in the group with AD (11 female and 14 male) and 72.1 +/- 5.8 in the control group (9 female and 11 male). Multiple linear regression analysis revealed that FMD was significantly lower in patients with AD (median 3.45, range 0-7) than controls (median 8.41, range 1-14) (P < .001), independent of age. It was also found that FMD values were inversely correlated with the stage of the disease as determined according to the Clinical Dementia Rating scale (r=-0.603, P < .001). CONCLUSION: Endothelial function is impaired in patients with AD. Endothelial function was worse in patients with severe AD. These findings provide evidence that vascular factors have a role in the pathogenesis of AD.  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