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   1502篇
  免费   340篇
  国内免费   30篇
耳鼻咽喉   5篇
儿科学   92篇
妇产科学   14篇
基础医学   363篇
口腔科学   20篇
临床医学   169篇
内科学   285篇
皮肤病学   28篇
神经病学   110篇
特种医学   13篇
外科学   403篇
综合类   74篇
现状与发展   1篇
预防医学   72篇
眼科学   11篇
药学   126篇
中国医学   25篇
肿瘤学   61篇
  2023年   20篇
  2022年   22篇
  2021年   53篇
  2020年   53篇
  2019年   111篇
  2018年   128篇
  2017年   120篇
  2016年   82篇
  2015年   99篇
  2014年   126篇
  2013年   141篇
  2012年   95篇
  2011年   105篇
  2010年   77篇
  2009年   64篇
  2008年   59篇
  2007年   58篇
  2006年   44篇
  2005年   36篇
  2004年   39篇
  2003年   39篇
  2002年   27篇
  2001年   31篇
  2000年   26篇
  1999年   22篇
  1998年   17篇
  1997年   15篇
  1996年   11篇
  1995年   4篇
  1994年   10篇
  1993年   10篇
  1992年   14篇
  1991年   13篇
  1990年   6篇
  1989年   3篇
  1988年   4篇
  1987年   10篇
  1986年   2篇
  1985年   9篇
  1984年   21篇
  1983年   7篇
  1982年   7篇
  1981年   12篇
  1980年   7篇
  1979年   2篇
  1978年   2篇
  1977年   2篇
  1976年   3篇
  1975年   1篇
  1973年   3篇
排序方式: 共有1872条查询结果,搜索用时 31 毫秒
11.

Background

Myositis is a heterogeneous group of muscular auto-immune diseases with clinical and pathological criteria that allow the classification of patients into different sub-groups. Inclusion body myositis is the most frequent myositis above fifty years of age. Diagnosing inclusion body myositis requires expertise and is challenging. Little is known concerning the pathogenic mechanisms of this disease in which conventional suppressive-immune therapies are inefficacious.

Objectives

Our aim was to deepen our understanding of the immune mechanisms involved in inclusion body myositis and identify specific biomarkers.

Methods

Using a panel of thirty-six markers and mass cytometry, we performed deep immune profiling of peripheral blood cells from inclusion body myositis patients and healthy donors, divided into two cohorts: test and validation cohorts. Potential biomarkers were compared to myositis controls (anti-Jo1-, anti-3-hydroxyl-3-methylglutaryl CoA reductase-, and anti-signal recognition particle-positive patients).

Results

Unsupervised analyses revealed substantial changes only within CD8+ cells. We observed an increase in the frequency of CD8+ cells that expressed high levels of T-bet, and containing mainly both effector and terminally differentiated memory cells. The senescent marker CD57 was overexpressed in CD8+T-bet+ cells of inclusion body myositis patients. As expected, senescent CD8+T-bet+ CD57+ cells of both patients and healthy donors were CD28nullCD27nullCD127null. Surprisingly, non-senescent CD8+T-bet+ CD57- cells in inclusion body myositis patients expressed lower levels of CD28, CD27, and CD127, and expressed higher levels of CD38 and HLA-DR compared to healthy donors. Using classification and regression trees alongside receiver operating characteristics curves, we identified and validated a frequency of CD8+T-bet+ cells >51.5% as a diagnostic biomarker specific to inclusion body myositis, compared to myositis control patients, with a sensitivity of 94.4%, a specificity of 88.5%, and an area under the curve of 0.97.

Conclusion

Using a panel of thirty-six markers by mass cytometry, we identify an activated cell population (CD8+T-bet+ CD57- CD28lowCD27lowCD127low CD38+ HLA-DR+) which could play a role in the physiopathology of inclusion body myositis, and identify CD8+T-bet+ cells as a predominant biomarker of this disease.  相似文献   
12.
肝癌细胞微细胞介导染色体转移方法学的建立与探讨   总被引:13,自引:0,他引:13  
目的建立肝癌细胞微细胞介导染色体转移方法,为肝癌转移抑制基因的染色体功能定位建立技术平台。方法人单染色体供体细胞通过微核化、出核、融合步骤将随机标记有耐药neo基因的正常人8号染色体导入到大鼠肝癌高转移细胞系C5F中,对微细胞杂交克隆进行药物筛选和单细胞克隆,并填序列标签位点-PCR和全染色体涂染荧光原位杂交方法验证人染色体转移的结果。结果获得具有G418和HAT双重抗性的微细胞杂交细胞,通过单细胞分离克隆方法获得15个具有双重抗性的微细胞杂交克隆,序列标签位点-PCR结果发现导入染色体的随机片段丢失,全染色体涂染荧光原位杂交结果发现导入的人8号染色体与大鼠染色体发生了稳定的重组。结论成功建立微细胞介导的染色体转移技术,为肝癌转移抑制基因的染色体功能定位奠定了技术基础。  相似文献   
13.
The sensitivity of the rat submaxillary gland was examined 3–4 weeks after either parasympathetic decentralization or sympathetic decentralization or denervation. The threshold doses for secretion of saliva of parasympathomimetic (methacholine) and sympathomimetic (noradrenaline, adrenaline, phenylephrine and isoprenaline) drugs were estimated and the amount of saliva secreted in response to supraliminal doses of these drugs was measured. Each type of operation caused the development of a supersensitivity that involved all three types of receptors, i.e. muscarinic cholinoceptors, alpha;-adrenoceptors and β-adrenoceptors. Following parasympathetic decentralization the sensitization was predominantly mediated via α-adrenoceptors, and also via cholinoceptors. Following sympathetic decentralization or denervation the postjunctional sensitization was predominantly mediated via β-adrenoceptors; most of the supersensitivity to noradrenaline, adrenaline and phenylephrine found after sympathetic denervation was of the prejunctional type. An increase in receptor density and an intracellular arrangement where the response of cholinoceptors and α-adrenoceptors is mediated via one pathway and the response of β-adrenoceptors via another are suggested as factors that may be of importance for the development of the postjunctional supersensitivity. The present study shows that the traffic of secretory impulses in the sympathetic nerve is of importance for the level of sensitivity of the secretory cells. Since postjunctional supersensitivity following sympathetic denervation did not exceed that following sympathetic decentralization it is suggested that under normal conditions a continuous release of noradrenaline from the nerve endings is of little importance for the level of sensitivity.  相似文献   
14.
PROBLEM: To characterize the constitutive internalization of major histocompatibility complex (MHC) class I molecules, we have studied the expression of completely conformed (full) and unconformed (empty) L(d) molecules on non-polarized murine P815 cells. METHODS OF STUDY: Spontaneous endocytosis of L(d) molecules was induced by cycloheximide, an inhibitor of protein synthesis, and their disappearance from the cell surface was determined by flow cytometry. In order to investigate the mechanism of internalization, a palette of inhibitors of endocytosis and vesicular transport was used. RESULTS: Inhibitors of clathrine endocytosis did not influence the internalization of L(d) molecules. Inhibitors of caveolar endocytosis and inhibitors of endolysosomal degradation prevented down-regulation of empty, but not of full L(d) molecules. CONCLUSIONS: Empty L(d) molecules are internalized mostly by caveolar endocytosis and full L(d) molecules use a different pathway, neither clathrine-mediated nor caveolar. After internalization, full L(d) molecules are probably degraded and empty L(d) molecules recycle between endosomal compartment and the cell surface before they enter into the degradation compartment.  相似文献   
15.
Sivakumar PV  Foster DC  Clegg CH 《Immunology》2004,112(2):177-182
Cytokines and their receptors represent key targets for therapeutic intervention. Ligands are being used to supplement cell numbers that become depleted as a result of disease (organ failure, infection) or subsequent disease treatments (i.e. chemotherapy). Conversely, the inhibition of target cell binding by cytokines is an established strategy for abrogating pathologic cellular activities common to many immunological diseases. Considerable effort in biomedical research is being focused on the cytokine families that play a dominant role in regulating immunity and then prioritizing each member for its therapeutic potential. Currently, the interleukin-2 (IL-2) family of cytokines is widely recognized for its central involvement in controlling lymphocyte function and is the most explored for medical utility. Collectively, these proteins (or their antagonists) are either marketed drugs or have received advanced testing for an impressive array of indications including cancer, infectious disease, transplantation, inflammation and allergic asthma. Here we review the current understanding of IL-21, the most recent member of this cytokine family to be discovered. As will be discussed, IL-21 shares many of the same attributes as its relatives in that it has broad immunoregulatory activity and can modulate both humoral and cell-mediated responses. Its ability to stimulate durable anti-tumour responses in mice defines one therapeutic indication that merits clinical development.  相似文献   
16.
目的 检测肺鳞状细胞癌中死亡相关蛋白激酶 (DAP K)mRNA表达及细胞凋亡 ,探讨DAP K与细胞凋亡的关系及其在肺鳞状细胞癌发生、发展中的作用。方法 用原位分子杂交法检测 6 0例肺鳞状细胞癌、9例癌旁肺组织DAP KmRNA表达 ;用原位末端标记TUNEL法检测相应组织中细胞凋亡 ,计算凋亡指数 (AI)。结果 肺鳞状细胞癌的DAP KmRNA阳性表达率为 4 6 7% ,癌旁肺组织为 6 7 7% ,其阳性率高于肿瘤组织 (P <0 0 1 )。在肺鳞状细胞癌中 ,高分化癌DAP KmRNA阳性率为 70 % ,低分化癌为 2 3 3% ,高分化癌的DAP KmRNA阳性率高于低分化癌 (P <0 0 1 )。肺鳞状细胞癌的细胞AI为(0 6 72 8± 0 4 2 6 1 ) % ,癌旁肺组织中支气管肺泡上皮细胞AI为 (1 0 2 89± 0 2 4 33) % ,癌旁肺组织的AI高于肿瘤组织 (P<0 0 1 )。在肺鳞状细胞癌中 ,高分化癌的AI为 (0 5 82 3± 0 1 92 2 ) % ,低分化癌为 (0 4 4 6 0± 0 1 92 5 ) % ,高分化癌的AI高于低分化癌 (P <0 0 1 )。DAP KmRNA呈阳性表达的肺癌 ,其AI为 (0 5 31 7± 0 2 0 97) % ;DAP KmRNA呈阴性者 ,其AI为 (0 4 872± 0 1 91 8) % ,两组间差异有显著性 (P <0 0 5 )。在连续切片上 ,DAP KmRNA阳性细胞的分布区域与凋亡阳性细胞的分布相似。DAP KmRNA呈阳性表达  相似文献   
17.
In order to study the relationship between cell-mediated immune responses to Chlamydia trachomatis and the pathogenesis of human chlamydial eye disease, we have measured the peripheral blood lymphocyte proliferative responses to whole chlamydial elementary bodies in 40 subjects with oculogenital chlamydial infection of varying severity, 13 subjects with genital chlamydial infections and 12 healthy seronegative controls. The mean stimulation index was significantly higher in those with oculogenital infections than in controls. There was a strong correlation between the response to C. trachomatis serotypes B and L1. We studied the relationship between proliferative responses and four clinical parameters: follicular conjunctivitis, papillary hypertrophy, corneal pannus and epithelial punctate keratitis, but were unable to show a significant association with any of these. Nor was there any association between proliferative response and serum antibody titre to C. trachomatis (pooled serotypes D-K), duration of disease or quantitative isolation of chlamydia from the conjunctiva. The depletion of CD8+ cells had no consistent effect on proliferative responses to serotype L1 in 13 subjects.  相似文献   
18.
19.
Individual specific antigenic rubella virus (RV) structural proteins are required for accurate serological diagnosis of acute and congenital rubella infections as well as rubella immune status. The RV envelope glycoprotein E1 is the major target antigen and plays an important role in viral-specific immune responses. The native virion is difficult to produce in large quantities and the protein subunits are also difficult to isolate without loss of antigenicity. The production of a soluble RV E1 (designated E1ΔTm) using the baculovirus-insect cell expression system is described. In contrast to wild-type RV E1, the genetically engineered E1ΔTm protein lacks a transmembrane anchor. It behaved as a secretory protein and was secreted abundantly from insect cells. Pulse-chase studies were used to examine the synthesis, glycosylation, and secretion of E1ΔTm by the insect cells. The secreted E1ΔTm protein was purified from serum-free medium by onestep immunochromatography. The purified E1ΔTm protein retained full antigenicity and may be a convenient source of E1 protein for use in diagnostic assay and rubella vaccine development.  相似文献   
20.
In order to identify T cell epitopes within the Mycobacterium leprae 45-kD serine-rich antigen, we analysed responses to overlapping 17-mer peptides encompassing the whole antigen in non-exposed UK controls, Pakistani leprosy patients and tuberculosis patients in both the United Kingdom and Pakistan. This antigen has been described as M. leprae-specific, although it has a hypothetical homologue in M. tuberculosis. Human peripheral blood mononuclear cells were stimulated with peptide for 5 days and IFN-gamma measured in supernatants by ELISA. Some peptides were recognized more frequently by T cells from tuberculoid leprosy patients than those from UK controls, suggesting that such T cell epitopes might have diagnostic potential, while other peptides induced greater responses among UK control subjects. Short-term cell lines confirmed that these assays detected specific T cell recognition of these peptides. However, many tuberculosis patients also recognized these potentially specific peptides suggesting that there could be a true homologue present in M. tuberculosis.  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