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   5866篇
  免费   648篇
  国内免费   234篇
耳鼻咽喉   31篇
儿科学   119篇
妇产科学   39篇
基础医学   1249篇
口腔科学   321篇
临床医学   511篇
内科学   1337篇
皮肤病学   265篇
神经病学   288篇
特种医学   77篇
外科学   332篇
综合类   842篇
预防医学   188篇
眼科学   72篇
药学   554篇
中国医学   235篇
肿瘤学   288篇
  2024年   1篇
  2023年   64篇
  2022年   74篇
  2021年   174篇
  2020年   164篇
  2019年   254篇
  2018年   263篇
  2017年   237篇
  2016年   213篇
  2015年   214篇
  2014年   406篇
  2013年   360篇
  2012年   333篇
  2011年   380篇
  2010年   294篇
  2009年   239篇
  2008年   255篇
  2007年   236篇
  2006年   209篇
  2005年   215篇
  2004年   218篇
  2003年   308篇
  2002年   291篇
  2001年   216篇
  2000年   175篇
  1999年   200篇
  1998年   167篇
  1997年   131篇
  1996年   82篇
  1995年   56篇
  1994年   55篇
  1993年   47篇
  1992年   30篇
  1991年   34篇
  1990年   26篇
  1989年   28篇
  1988年   18篇
  1987年   10篇
  1986年   11篇
  1985年   43篇
  1984年   8篇
  1983年   3篇
  1982年   4篇
  1981年   1篇
  1980年   1篇
排序方式: 共有6748条查询结果,搜索用时 62 毫秒
31.
BACKGROUND: Inflammation has been proposed to play essential roles in the pathophysiology of endometriosis, in which neutrophils and mast cells have been suggested to be involved. We studied whether the protease-activated receptor 2 (PAR2), which is activated by enzymes from neutrophils and mast cells, in endometriotic stromal cells (ESC) has any implication in the development of the disease. METHODS: Cultured ESC were stimulated with various concentrations of a specific PAR2 agonist peptide. Proliferating activity of the cells was determined using immunostaining of proliferating cell nuclear antigen (a cell proliferation marker), 5-bromo-2'-deoxyuridine incorporation into DNA and cell count. The concentrations of interleukin (IL)-6 and IL-8 were measured using specific enzyme-linked immunosorbent assay kits. The phosphorylation of three mitogen-activated protein kinases (MAPK), i.e. p38 MAPK, p42/44 MAPK and stress-activated protein Kinase/c-jun N terminal Kinase, in ESC was examined with Western blot analysis. RESULTS: Activation of PAR2 stimulated the proliferation of ESC and the secretion of IL-6 and IL-8 from ESC in a dose-dependent manner. Activation of PAR2 stimulated the phosphorylation of all three MAPK, and inhibitors of each MAPK suppressed the PAR2 activation-induced proliferation of ESC. CONCLUSIONS: The activation of PAR2 in ESC may be involved in the pathophysiology of endometriosis by inducing the growth and inflammation of endometriotic lesions.  相似文献   
32.
Reconstitution of functional CD4(+) T cell responsiveness to in vitro stimuli is associated with continuous highly active antiretroviral therapy (HAART). Thirty-six antiretroviral naive patients received HAART over 16 weeks. Antigen-specific, mitogen and interleukin (IL)-2 induced lymphocyte proliferative responses and specific IL-2 and IL-4 production were assessed at each time-point, together with quantification of HIV-1 RNA load and lymphocyte populations. Reconstitution of recall responses was limited largely to persistent antigens such as Herpes simplex virus and Candida, rather than to HIV-1 or neo-antigens. Recall antigens, mitogens and IL-2-induced renewed responses were associated with in-vitro production of IL-2, but not IL-4. Differential responsiveness to low versus high concentration IL-2 stimulus increases in a stepwise manner, suggesting normalization of IL-2 receptor expression and improved functionality. These increases in in-vitro proliferative responses thus probably reflect short lived effector clones, driven by ongoing antigenic stimulus associated with persisting long-term organisms. In this context non-responsiveness to HIV-1 antigens suggests ongoing HIV-1 specific clonal T cell anergy.  相似文献   
33.
The contribution of sialic acids and of N-linked sugars to the biological activity of the receptor for IL 2 has been evaluated by treating activated cells with Neuraminidase or by growing them in the presence of inhibitors of N-linked glycosylation or processing. After treatment with Neuraminidase, Con A-activated spleen cells had not lost their ability to bind IL 2. The IL 2-absorbing capability was, however, strongly reduced after trypsinisation. 6 hours after Trypsin treatment, this property was again expressed. Proliferation of the IL 2-dependent CTLL cells was normal in the presence of Swainsonine but strongly impaired in the presence of Tunicamycin. Glycosylation of the IL 2 receptor may thus be required, but integrity of the sugars is not critical.  相似文献   
34.
The TGF-1(–/–) mouse is a murine model for systemic autoimmune disease. The aim of this study is to elucidate the immunological mechanism that leads to multifocal tissue inflammation and autoantibody production in TGF-1(–/–) mice. Heart, lung, liver, and salivary gland from TGF-1(–/–) were assessed for CD154 expression by RT-PCR and immunohistochemistry. Compared to wild-type littermates, CD154 expression was elevated in all tissues studied. Furthermore, IL-12 mRNA was expressed in the salivary gland and heart of TGF-1(–/–) mice and not in wild-type littermates. This suggests that the CD154 pathway is activated in these tissues. This shows that TGF-1 regulates CD154 expression leading to spontaneous IL-12 production and autoimmunity.  相似文献   
35.
目的在COS7细胞中表达具有生物学功能的人可溶性IL-6R(sIL-6R),作为研究sIL-6R结构与功能关系的基础。方法首先利用PCR技术扩增出人可溶性IL-6R(hsIL-6R)编码基因片段,并重组入克隆载体pALTER-1。通过基因序列分析确定了目的基因的核苷酸序列,并进一步构建了由SV40晚期启动子和HCMV早期启动子控制的表达质粒pSVL6R和pCMV6R。用脂质体介导的方法将表达质粒转染COS7细胞,并分别在mRNA水平(斑点杂交)和蛋白水平(ELISA和Western-blot)检测sIL-6R基因在COS7细胞中的表达。在7TD1,LT12两种IL-6反应细胞系上检测转染细胞上清(含sIL-6R)的生物学活性。结果在mRNA水平和蛋白水平分别检测到sIL-6R基因在COS7细胞中的表达,表达产物分子量约为50000。表达产物在7TD1,LT12细胞系上检测到明显的生物学活性。结论天然sIL-6R基因在COS7细胞中的成功表达为进一步制备sIL-6R突变体及其结构与功能关系的研究奠定了基础  相似文献   
36.
Acute emotional stress results in damage to gastric mucous membranes in August, Wag, and particularly Wistar rats. The damage is less severe in rats preinjected with inter-leukin 1β into a lateral ventricle of the cerebrum. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 117, N o 3, pp. 238–239, March, 1994  相似文献   
37.
应用细胞原位杂交技术,观察经重组小鼠白细胞介素-19(IL-1β)处理后的体外培养的新生1d大鼠中脑黑质神经元c-jun基因的表达.结果显示,培养的黑质细胞多为酪氨酸羟化酶阳性神经元,IL-1β可诱导体外培养的黑质神经元c-junmRNA表达,高水平的表达出现在IL-1β处理后2~4h。说明IL-1β有兴奋黑质神经元的作用,并提示黑质神经元上可能存在IL-1β受体.  相似文献   
38.
目的:观察炎症因子IL-1及肿瘤坏死因子(TNF)对人肾小球系膜细胞(HMC)分泌IL-8的影响。方法:体外细胞培养技术及ELISA夹心法。结果:IL-1、TNF均可诱导HMC分泌IL-8,并呈剂量依赖性。结论:在一些炎症因子刺激下,HMC可能通过分泌趋化因子IL-8参与肾脏炎症反应的启动和维持  相似文献   
39.
The present study was undertaken to examine the T-lymphocyte activation in IgA nephropathy. Serum-soluble interleukin 2 receptor (sIL2R) levels were studied in 29 IgA nephritic patients, 17 patients with chronic glomerulonephritis (non-IgA nephropathy), and 30 healthy controls during an infection-free period. No difference in serum sIL2R level was demonstrated among these three groups of subjects. However, the serum sIL2R levels of IgA nephritic patient rose significantly during clinical exacerbation with synpharyngitic macroscopic hematuria and the serum sIL2R levels fell when hematuria subsided. Mitogen-stimulated cellular interleukin 2 receptor (IL2R) expression, sIL2R release, and interleukin 2 (IL2) production were also examined in peripheral blood mononuclear cells (PBMC) cultured for 24–48 hr in 21 patients with IgA nephropathy, 17 patients with chronic glomerulonephritides, and 17 healthy controls. The total cellular IL2R expression and sIL2R release did not differ among these three groups of subjects. However, the individual T-cell subsets bearing IL2R were distinctly different between IgA nephritic patients and the other two groups of controls. IgA nephritic patients had increased activated CD4+ lymphocytes and reduced activated CD8+ lymphocytes. Furthermore, IL2 production in response to phytohemagglutinin and pokeweed mitogen stimulation was increased in lymphocytes from patients with IgA nephropathy. The IL2 production did not correlate with the quantities of cellular and sIL2R yet the cellular IL2R expression paralleled the sIL2R released by cultured lymphocytes. Our present study suggests that the T lymphocytes from patients with IgA nephropathy have a defect in overproduction of IL2 and increased activated T helper-cell subset upon mitogenic stimulation. Serum measurement of sIL2R could potentially be useful in monitoring the disease activity.  相似文献   
40.
(LEW X BN)F1 cardiac allografts are rejected within 8 days in untreated LEW recipients. At the critical time point of 5 days after transplantation, the obviously rejecting grafts are enlarged and maximally infiltrated by host cells as shown by 111In-labeled lymphocyte tracer studies. However, when such hearts were retransplanted back to naive (LEW X BN)F1 secondary hosts, they survive indefinitely, showing that even late rejection is reversible in the absence of sustained host immunological drive. Attempts were then made to abrogate this advanced immune responsiveness using Cyclosporine (CsA). CsA therapy (15 mg/kg/day for 7 days) starting from day 5 produced indefinite graft survival, similar as if initiated at the time of operation. Addition of exogenous IL-2, which drives the proliferation of Tc, could not reverse this effect. Serial changes in phenotype of lymphocyte subpopulations infiltrating both acutely rejecting and indefinitely functioning cardiac allografts in unmodified and CsA treated hosts, respectively, were then studied. Ratio of Th:Tc/s cells in acutely rejecting grafts was 1.6 by day 3; it inverted abruptly to 0.7 by day 5-6, suggesting predominance of Tc/s during the later stages of allograft rejection. Similarly, treatment with CsA produced a transient depression of Th, with recovery of original Th:Tc/s ratio during the next 2-3 weeks. Adoptive transfer experiments were then performed to investigate the functional significance of these findings.(ABSTRACT TRUNCATED AT 250 WORDS)  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