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   936篇
  免费   55篇
  国内免费   48篇
耳鼻咽喉   2篇
儿科学   53篇
妇产科学   33篇
基础医学   105篇
口腔科学   38篇
临床医学   111篇
内科学   257篇
皮肤病学   11篇
神经病学   28篇
特种医学   118篇
外科学   108篇
综合类   14篇
预防医学   48篇
眼科学   4篇
药学   75篇
  1篇
中国医学   1篇
肿瘤学   32篇
  2023年   6篇
  2022年   9篇
  2021年   12篇
  2020年   7篇
  2019年   9篇
  2018年   19篇
  2017年   11篇
  2016年   16篇
  2015年   18篇
  2014年   28篇
  2013年   37篇
  2012年   21篇
  2011年   28篇
  2010年   26篇
  2009年   33篇
  2008年   15篇
  2007年   50篇
  2006年   27篇
  2005年   22篇
  2004年   26篇
  2003年   16篇
  2002年   18篇
  2001年   13篇
  2000年   19篇
  1999年   18篇
  1998年   46篇
  1997年   53篇
  1996年   56篇
  1995年   47篇
  1994年   31篇
  1993年   30篇
  1992年   4篇
  1991年   18篇
  1990年   14篇
  1989年   26篇
  1988年   32篇
  1987年   25篇
  1986年   22篇
  1985年   28篇
  1984年   13篇
  1983年   15篇
  1982年   12篇
  1981年   8篇
  1980年   11篇
  1978年   5篇
  1977年   8篇
  1976年   3篇
  1975年   5篇
  1973年   6篇
  1972年   3篇
排序方式: 共有1039条查询结果,搜索用时 15 毫秒
41.
Manometry of the alimentary tract is a valuable and widely used means to evaluate and diagnose the function of the alimentary tract. However, the measurement can be inconvenient due to the invasive method used, and the many factors affecting results. Research on colonic pressure data is even more insufficient. This paper deals with colonic pressure data via an improved method ensuring that pressure data of the whole colon is available. The data is analysed based on the learning vector quantization (LVQ) method. Testing results show that this method distinguishes the normal data and the abnormal data, consistently with the original diagnoses. This method can serve as an assistant diagnosis of colonic motility and contributes to further research on colonic motility based on pressure data.  相似文献   
42.
As more mutations are identified in genes of known sequence, there is a crucial need in the areas of medical genetics and genome analysis for rapid, accurate and cost-effective methods of mutation detection. We have developed a multiplex allele-specific diagnostic assay (MASDA) for analysis of large numbers of samples (> 500) simultaneously for a large number of known mutations (> 100) in a single assay. MASDA utilizes oligonucleotide hybridization to interrogate DNA sequences. Multiplex DNA samples are immobilized on a solid support and a single hybridization is performed with a pool of allele-specific oligonucleotide (ASO) probes. Any probes complementary to specific mutations present in a given sample are in effect affinity purified from the pool by the target DNA. Sequence-specific band patterns (fingerprints), generated by chemical or enzymatic sequencing of the bound ASO(s), easily identify the specific mutation(s). Using this design, in a single diagnostic assay, we tested samples for 66 cystic fibrosis (CF) mutations, 14 beta-thalassemia mutations, two sickle cell anemia (SCA) mutations, three Tay-Sachs mutations, eight Gaucher mutations, four mutations in Canavan disease, four mutations in Fanconi anemia, and five mutations in BRCA1. Each mutation was correctly identified. Finally, in a blinded study of 106 of these mutations in > 500 patients, all mutations were properly identified. There were no false positives or false negatives. The MASDA assay is capable of detecting point mutations as well as small insertion or deletion mutations. This technology is amenable to automation and is suitable for immediate utilization for high-throughput genetic diagnostics in clinical and research laboratories.   相似文献   
43.
44.
45.
该文旨在介绍Beth Israel医疗中心采用大剂量术中放疗(HDR-IORT)治疗复发头颈癌的经验。对2001-2010年间头颈癌局部复发接受大剂量HDR-IORT的患者进行回顾分析。结果,76例患者的87个部位在肿瘤切除后接受了治疗。术后2年控制率为62%。平均总生存期为19个月,其中42%的患  相似文献   
46.
47.
Tumor cells from eight adult patients with T-cell chronic malignancies were investigated with a series of monoclonal antibodies recognizing T- cell differentiation antigens. This series allowed definition of discrete subpopulations of mature T cells with functional specialization. All six patients with Sezary syndrome and one patient with T-chronic lymphocytic leukemia had cells with the same phenotype as normal helper/inducer T cells, whereas the other patient with T- chronic lymphocytic leukemia had cell with the same phenotype as normal cytotoxic/suppressor T cells. Some clinical manifestations observed in these patients may reflect retention of functional activities by their malignant cells.  相似文献   
48.
Ingraham  LM; Boxer  LA; Haak  RA; Baehner  RL 《Blood》1981,58(4):830-835
We have studied membrane fluidity changes in polymorphonuclear leukocytes (PMN) during phagocytosis. Membrane fluidity was assessed by electron spin resonance (ESR) using a nitroxide-substituted stearic acid analog (5DS) as a spin probe. PMN from normal subjects and from 3 CGD patients (2 males, 1 female) were incubated in Kreb's Ringers phosphate with or without opsonized zymosan. ESR spectra were obtained and the order parameter (S), which is inversely related to membrane fluidity, was calculated. Without zymosan addition, S for normal (0.638) and for CGD (0.635) were not significantly different (p less than 0.35). The S values indicate that under resting conditions the molecular environment of the CGD membrane is similar to that of normal PMN membranes. However, with addition of opsonized zymosan, the normal, but not the CGD, PMN showed a significant increase (CGD, S = 0.638; normal, S = 0.647; p less than 0.001). This change in S for the normals is consistent with a more restricted movement of 5DS. Treatment of normal PMN with a mixture of scavengers specific for H2O2 (catalase, 1600 U/ml), O2-.(superoxide dismutase, 100 micrograms/ml), and for HO., (sodium benzoate, 1mM) during zymosan stimulation gave S values similar to those of resting cells. Catalase alone also lowered S value, suggesting that H2O2 was instrumental in causing the initial S value increase. This idea was supported by studies in which CGD cells were incubated with zymosan in the presence of glucose oxidase, an enzyme that catalyzes glucose oxidation resulting in the direct reduction of molecular oxygen to H2O2. Our results indicate that reduced O2 by- products, particularly H2O2, can cause altered biophysical properties of PMN membrane during phagocytosis.  相似文献   
49.

Background

In pig‐to‐human xenotransplantation, interactions between human natural killer (NK) cells and porcine endothelial cells (pEC) are characterized by recruitment and cytotoxicity. Protection from xenogeneic NK cytotoxicity can be achieved in vitro by the expression of the non‐classical human leukocyte antigen‐E (HLA‐E) on pEC. Thus, the aim of this study was to analyze NK cell responses to vascularized xenografts using an ex vivo perfusion system of pig limbs with human blood.

Methods

Six pig forelimbs per group, respectively, stemming from either wild‐type (wt) or HLA‐E/hCD46 double‐transgenic (tg) animals, were perfused ex vivo with heparinized human blood for 12 hours. Blood samples were collected at defined time intervals, cell numbers counted, and peripheral blood mononuclear cells analyzed for phenotype by flow cytometry. Muscle biopsies were analyzed for NK cell infiltration. In vitro NK cytotoxicity assays were performed using pEC derived from wt and tg animals as target cells.

Results

Ex vivo, a strong reduction in circulating human CD45 leukocytes was observed after 60 minutes of xenoperfusion in both wt and tg limb groups. NK cell numbers dropped significantly. Within the first 10 minutes, the decrease in NK cells was more significant in the wt limb perfusions as compared to tg limbs. Immunohistology of biopsies taken after 12 hours showed less NK cell tissue infiltration in the tg limbs. In vitro, NK cytotoxicity against hCD46 single tg pEC and wt pEC was similar, while lysis of double tg HLA‐E/hCD46 pEC was significantly reduced. Finally, circulating cells of pig origin were observed during the ex vivo xenoperfusions. These cells expressed phenotypes mainly of monocytes, B and T lymphocytes, NK cells, as well as some activated endothelial cells.

Conclusions

Ex vivo perfusion of pig forelimbs using whole human blood represents a powerful tool to study humoral and early cell‐mediated rejection mechanisms of vascularized pig‐to‐human xenotransplantation, although there are several limitations of the model. Here, we show that (i) transgenic expression of HLA‐E/hCD46 in pig limbs provides partial protection from human NK cell‐mediated xeno responses and (ii) the emergence of a pig cell population during xenoperfusions with implications for the immunogenicity of xenografts.  相似文献   
50.
It is premature to try to compare the results of aortic valve surgery obtained by the so-called minimally-invasive techniques, with those obtained with the use of the conventional median sternotomy approach. The experience accumulated with this type of limited access surgery is small and remains anecdotal. We reviewed one hundred consecutive aortic valve patients operated at the Mayo Clinic. There was one hospital death. There were no instances of post-operative bleeding or mediastinitis. Average duration of extracorporeal circulation was 72 minutes; average duration of aortic cross-clamp was 50 minutes. Duration of hospitalization in these patients averaged 6.4 days. These results compare favorably with those reported with the minimally invasive procedures.  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