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   994篇
  免费   65篇
  国内免费   1篇
耳鼻咽喉   35篇
儿科学   31篇
妇产科学   18篇
基础医学   132篇
口腔科学   18篇
临床医学   57篇
内科学   258篇
皮肤病学   13篇
神经病学   78篇
特种医学   20篇
外科学   134篇
综合类   9篇
预防医学   46篇
眼科学   94篇
药学   53篇
中国医学   3篇
肿瘤学   61篇
  2023年   9篇
  2022年   12篇
  2021年   17篇
  2020年   17篇
  2019年   22篇
  2018年   50篇
  2017年   26篇
  2016年   25篇
  2015年   25篇
  2014年   20篇
  2013年   35篇
  2012年   51篇
  2011年   62篇
  2010年   33篇
  2009年   28篇
  2008年   33篇
  2007年   45篇
  2006年   50篇
  2005年   50篇
  2004年   40篇
  2003年   43篇
  2002年   37篇
  2001年   36篇
  2000年   32篇
  1999年   24篇
  1998年   8篇
  1997年   4篇
  1996年   8篇
  1995年   7篇
  1994年   6篇
  1993年   4篇
  1992年   19篇
  1991年   13篇
  1990年   13篇
  1989年   11篇
  1988年   16篇
  1987年   16篇
  1986年   12篇
  1985年   15篇
  1984年   12篇
  1983年   6篇
  1982年   4篇
  1981年   5篇
  1979年   12篇
  1978年   8篇
  1973年   5篇
  1971年   4篇
  1970年   3篇
  1969年   4篇
  1966年   3篇
排序方式: 共有1060条查询结果,搜索用时 15 毫秒
1.
The accuracy of 2D phase contrast (PC) magnetic resonance angiography (MRA) depends on the alignment between the vessels and the imaging plane. PC MRA imaging of blood flow is challenging when the flow in several vessels is to be evaluated with one acquisition. For this purpose, semi-automatic determination of the plane most perpendicular to several vessels is proposed based on centerlines extracted from 3D MRA. Arterial centerlines are extracted from 3D MRA based on iterative estimation-prediction, multi-scale analysis of image moments, and a second-order shape model. The optimal plane is determined by minimizing misalignment between its normal vector and the centerlines’ tangent vectors. The method was evaluated on a phantom and on 35 patients, by seeking the optimal plane for cerebral blood flow quantification simultaneously in internal carotids and vertebral arteries. In the phantom, difference of orientation and of height between known and calculated planes was 1.2° and 2.5 mm, respectively. In the patients, all but one centerline were correctly extracted and the misalignment of the plane was within 12° per artery. Semi-automatic centerline extraction simplifies and automates determination of the plane orthogonal to one vessel, thereby permitting automatic simultaneous minimization of the misalignment with several vessels in PC MRA.  相似文献   
2.
Beta-thalassemia major (TM) is caused by any of approximately 150 mutations within the beta-globin gene. To establish the degree of chimerism after bone marrow transplantation (BMT), we have performed molecular analysis of beta-globin mutations in 14 patients with TM over a period of 10 years. All patients underwent T cell-depleted allogeneic BMT from HLA-identical related donors, using either in vitro T-cell depletion with CAMPATH 1M and complement or in vivo depletion using CAMPATH 1G in the bone marrow collection bag. To date, at different time periods after BMT, seven patients have some degree of chimerism; six of these patients, all blood transfusion-independent, have donor cells in the range of 70% to 95%, with stable mixed chimerism (MC). The seventh patient has less than 10% donor cells with, surprisingly, only minimal transfusion requirements. The detection of beta-globin gene point mutation, as used here, is a highly specific and sensitive marker for engraftment and MC in patients with thalassemia. In light of its specificity, the method is applicable in all cases of TM, as it is independent of sex and other non-globin-related DNA markers. The high incidence of MC found in our patients may be a consequence of the pre- BMT T-cell depletion. Because MC was associated with transfusion independence, complete eradication of residual host cells for effective treatment of TM and possibly other genetic diseases may prove not to be essential.  相似文献   
3.
A case of neurofibromatosis is presented in a 3-year-old male with leucokoria in his left eye. Enucleation was performed, and on pathological examination the mass filling the globe proved to be retinoblastoma. We believe ours to be the first reported case of this rare association.  相似文献   
4.
5.
The synthesis and structure-activity relationships of C-terminal octapeptide analogues of anaphylatoxin C5a have been studied. The introduction of hydrophobic amino acids into the N-acetylated native octapeptide (N-Ac-His-Lys-Asp-Met-Gln-Leu-Gly-Arg-OH) (1) has led to an analogue with 100 times more activity than the native octapeptide in inhibiting the binding of 125I-labeled anaphylatoxin C5a to human neutrophil membrane receptors. The observed apparent binding Ki's for the compounds (8-10) are in the range of 1-3 microM, and they possess nearly full agonist activity, despite the fact that these analogues are one-eighth or -ninth the size of the natural ligand anaphylatoxin C5a.  相似文献   
6.
In 30 patients on chronic haemodialysis treatment the platelet activity and function were studied before and during antiplatelet therapy with alpha-tocopherol and sulphinpyrazone. In both kinds of treatment a significant decrease of ADP-induced and spontaneous aggregation was observed. Sulphinpyrazone exerts an inhibitory effect not only on platelet aggregation but also on platelet factor 3 and provokes a significant prolongation of the bleeding time.  相似文献   
7.
A 6-month-old child with familial hemophagocytic lymphohistiocytosis (FHL) experienced early sequential pneumonia due to respiratory syncytial virus (RSV) and cytomegalovirus (CMV) following bone marrow transplantation (BMT). The patient was deficient in natural killer (NK) cell activity (as found frequently in patients with FHL), and this risk factor may have played a major role in the concomitant infection by the two viral pathogens. Rapid diagnostic methods for both viruses are essential and early specific treatment may serve to ameliorate RSV- and CMV-induced lung injury in these life-threatening infections. © 1995 Wiley-Liss, Inc.  相似文献   
8.
BackgroundHealth literacy, the ability to access, understand, evaluate and apply health information, was found to contribute to positive health outcomes, possibly via promoting healthy behaviours. However, the specific pathways linking different health literacy skills to health and well‐being have remained unclear.MethodsA cross‐sectional survey with structural questionnaires was administered among 2236 adults in Hong Kong (mean age = 46.10 ± 19.05). Health literacy was measured by HLS‐Asian‐47. Participants'' physical conditions and subjective well‐being were predicted by health literacy and health behaviours with structural modelling path analysis.ResultsHealth literacy in finding and understanding information showed a direct effect on enhancing physical health, while applying information capacity had an indirect positive effect via promoting health behaviours, which was moderated by sex. Only among women, this indirect effect predicting fewer physical symptoms and better well‐being was significant.ConclusionsDifferent health literacy dimensions showed distinct direct and indirect pathways in influencing health for men and women. Based on the findings, skill trainings should be developed to enhance both gender''s abilities of finding and understanding health information, while the ability of applying health information should also be improved for modifying lifestyle and promoting health, particularly for women.Patient or Public ContributionTwo thousand and two hundred thirty‐six adults from different districts of Hong Kong participated in the study, and responded to questions on health literacy, behaviours and health status.  相似文献   
9.
The purpose of this study was to define the treatment of choice (partial laryngectomy vs radiotherapy) in the early stage of supraglottic squamous cell cancer (ESSC). One hundred and fifteen patients with ESSC were treated with either partial laryngectomy (25 patients) or with radiotherapy(90 patients) between January 1984 and December 1996. All patients had a follow-up of over ¶29 months. Radiotherapy (RT) had a local control rate of 79%, which increased to 90% with salvage surgery, and a high larynx preservation rate (83%). Partial laryngectomy (PL) offered a better initial local control rate of 84%, which increased to 88% with salvage surgery, and functional results were also good (80%). No statistically significant differences were found between RT and PL. RT was less costly, showed better suitability for treatment, produced moderate morbidity and sequelae, and local recurrence was easier to rescue. However, it is a once-only application technique. PL showed higher immediate postoperative morbidity, higher cost and lower suitability for treatment but had fewer sequelae, offered the best initial local control and is multi-applicable. No clear oncological arguments were found in our series to define whether PL or RT is the treatment of choice for ESSC. Both are effective therapies. Secondary factors such as suitability for treatment, morbidity, cost and applicability should be individually evaluated when choosing the type of treatment. As the laser endoscopic approach decreases morbidity and costs and makes the condition more suitable for treatment, it could be the treatment of choice for ESSC, in cases where local tumoral extent and larynx exposure allow radical excision.  相似文献   
10.
The serum levels of type IV collagen 7s domain (7s collagen) were determined in 80 patients with hepatocellular carcinoma (HCC) and in 105 with chronic liver disease without HCC. Among 86 patients with HCV infection, serum levels of the 7s collagen were significantly higher in those with HCC than-in those without HCC (p<0.05). In contrast, no significant differences were recognized between these two groups in 84 patients with HBV infection. Patients with HCV infection having high serum levels of the 7s collagen exceeding 7.0 ng/ml, were diagnosed as HCC with a sensitivity of 71.8%, a specificity of 74.5%, and a reliability of 77.9%. It was concluded that the progression of hepatic fibrosis plays an important role in the hepatocarcinogenesis of HCV, and that serum levels of the 7s collagen appeared to be useful as a risk factor of the development of HCV-related HCC.  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