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   5924篇
  免费   354篇
  国内免费   190篇
耳鼻咽喉   50篇
儿科学   116篇
妇产科学   186篇
基础医学   1530篇
口腔科学   130篇
临床医学   421篇
内科学   1158篇
皮肤病学   170篇
神经病学   576篇
特种医学   50篇
外科学   554篇
综合类   469篇
预防医学   281篇
眼科学   57篇
药学   408篇
  1篇
中国医学   124篇
肿瘤学   187篇
  2024年   2篇
  2023年   33篇
  2022年   84篇
  2021年   144篇
  2020年   153篇
  2019年   121篇
  2018年   142篇
  2017年   165篇
  2016年   243篇
  2015年   225篇
  2014年   383篇
  2013年   488篇
  2012年   303篇
  2011年   445篇
  2010年   325篇
  2009年   384篇
  2008年   425篇
  2007年   357篇
  2006年   334篇
  2005年   291篇
  2004年   268篇
  2003年   195篇
  2002年   153篇
  2001年   130篇
  2000年   111篇
  1999年   77篇
  1998年   90篇
  1997年   76篇
  1996年   83篇
  1995年   77篇
  1994年   58篇
  1993年   47篇
  1992年   30篇
  1991年   10篇
  1990年   8篇
  1989年   5篇
  1988年   2篇
  1987年   1篇
排序方式: 共有6468条查询结果,搜索用时 15 毫秒
81.
目的: 抗体蛋白质芯片初步筛选常见细胞因子在卵巢癌耐药细胞株中的表达。 方法: 对6株卵巢癌细胞分别进行平行药敏试验及细胞因子抗体蛋白质芯片检测,同时筛选78种细胞因子的表达差异,并进行两两比较。 结果: 不同种类卵巢癌细胞系对于ADM的IC50值从高到低前3位依次为SKOV3,OVCAR5,OVCAR4;CBPDA为IGROV1,SKOV3,OVCAR3;TAXOL为OVCAR4,SKOV3,IGROV1;VP16为OVCAR4,OVCAR5,OVCAR8。在对一线化疗药ADM和 CBPDA耐药性较高的SKOV3细胞中GRO,IL-6,IL-8和TIMP-2均较其余5株相对敏感细胞增高,对二线化疗药TAXOL,VP16耐药性较高细胞株OVCAR4中IL-6,IL-8较之IGROV1,OVCAR3,OVCAR5升高。 结论: 在常见分泌型细胞因子中,GRO,IL-6,IL-8和TIMP-2升高与一线化疗药ADM和CBPDA耐药性相关,IL-6,IL-8与二线化疗药TAXOL,VP16耐药性相关,不同来源的卵巢癌细胞分泌型蛋白作用机制可能存在共同的上述几种蛋白参与的调节体系。  相似文献   
82.
张斗霞  张丽梅  张凌  白明 《微循环学杂志》2005,15(2):36-38,F003
目的:探讨兔急性肺血栓栓塞症(PTE)时血浆及支气管肺泡灌洗液(BALF)中TNF-α,IL-8、IL-10的水平和地塞米松(Dex)的影响。方法:采用自体血栓回输法建立兔急性PTF模型。36只兔随机分为对照组、Dex治疗组和PTE模型组。用ELISA方法检测上述细胞因子(CK)水平,术毕肺组织行病理观察。结果:栓塞后上述CK均有升高,治疗后TNF-α、IL-8均有下降,IL-10变化不明显。组织病理学可见栓塞后肺动脉内血栓形成,肺组织萎缩、出血、炎性反应明显,Dex治疗后肺组织病理改变明显减轻。结论:PTE后促炎性CK在引起肺部炎性反应和肺组织及肺动脉病损中起了重要作用,抗炎治疗可以明显减轻CK引起的这种损伤。抗炎治疗能降低PTE急性期病死率,改善远期预后,CK可能起了很重要的作用。  相似文献   
83.
SARS患者血清IL-8、IL-12和TGF-β1的检测及意义   总被引:5,自引:0,他引:5  
目的 :探讨SARS患者血清IL 8、IL 12和TGF β1在SARS冠状病毒感染致病中的作用。 方法 :应用酶联免疫吸附法 (ELISA)测定广州地区 2 8例SARS冠状病毒感染患者双份血清IL 8、IL 12和TGF β1的水平。实验数据采用两样本均数t检验法。结果 :2 8例SARS冠状病毒感染者血清IL 8水平、病程第 2周IL 12水平比正常健康对照组明显降低 (P <0 0 5 )。SARS冠状病毒感染者血清TGF β1水平与对照组比较无明显差异 (P >0 0 5 )。 结论 :IL 8和IL 12在SARS冠状病毒的致病与免疫过程中可能起降低细胞免疫功能作用  相似文献   
84.
Cytokine production in the spleens of mice infected with the protozoan parasite Trypanosoma cruzi was analyzed in three models which differ in the outcome of the infection. Using immunocytochemical techniques to detect cytokine-producing cells, the production of type 1 [interleukin-2 (IL-2) and interferon (IFN)-γ], type 2 (IL-4, IL-5, IL-10), inflammatory [tumor necrosis factor (TNF)-α, IL-1α, IL-6] and regulatory (transforming growth factor-β) cytokines were examined. With the exception of IL-4 and IL-5, cells producing all of the cytokines assayed were detected in both the resistant and susceptible models of T. cruzi infection. Cells producing IL-4 and IL-5 were not detected until later in infection in the resistant mice (>34 days), at about the time animals of the susceptible strain succumb to the infection. Mice of the susceptible model showed a slight delay in the appearance of cells producing the type 1 cytokines IL-2 and IFN-γ and an earlier appearance of TNF-producing cells, in comparison to resistant mice. Cells producing IL-2 or IL-10 were transient in their appearance in the spleen while cells producing IL-1, IL-4, IL-5, IL-6, IFN-γ, TNF, or TGF-β were first detectable in either the acute or post-acute stage of the infection and persisted up to 700 days post infection in two different resistant models of the infection. Cells producing IFN-γ, TNF-α and TGF-β were particularly numerous even very late in the infection. Double-staining techniques were used to show that the vast majority of the IFN-γ-producing cells in the spleen were CD4?, CD8? α/β TCR+ T cells. This study confirms the transience of IL-2 production in the acute stage of T. cruzi infection and the persistent and simultaneous production of type 1 and type 2 cytokines during the late-acute and chronic stages of the infection. Susceptibility or resistance to T. cruzi infection does not associate with a Th2 pattern of cytokine production in the three models examined in this study. The overlapping pattern of type 1 and type 2 cytokine-producing cells in both the acute and chronic stages of T. cruzi infection demonstrates that longterm infections do not necessarily lead to a dominance of either type 1 or type 2 cytokine production.  相似文献   
85.
The previously observed occurrence of antineutrophil cytoplasmic autoantibodies (ANCA) in patients who have cystic fibrosis (CF), together with the reported decrease in IgG2, a Th1-controlled isotype, suggests a potential for Th1/Th2 imbalance in CF patients with a possible Th2 predominance. 48 CF patients and 16 controls had levels of IFNgamma, IL-4, and IL-10 measured in supernatants of whole blood cell cultures stimulated by lipopolysaccharide (LPS) and phytohemaglutinine (PHA). The patients were divided into 2 groups: "low responders", having negligible secretion of cytokines (IFNgamma: 10.0-200.0 pg/ml, IL-4: 0.0-0.3 pg/ml) and "high responders", producing high levels of both IFNgamma (500.0-2000.0 pg/ml) and IL-4 (1.0-200.0 pg/ml). There was a statistically significant (P < 0.01) deterioration of lung function measured by an FEV(1) decline by 11.2% over 3 years in the "low responder" group. 10 of 16 "low responders" had chronic lung infections with P. aeruginosa while such infection was less prevalent in the "high responder" group where only 13 of 32 CF patients had positive cultures. A shift towards Th2 response was observed in the "high responder" group as children chronically infected with P. aeruginosa had greater IL-4 production than non-infected CF patients within the same cohort. ANCA autoantibodies were found only in the "high responder" group. Th2 immune response predominance in a subset of CF patients is associated with chronic P. aeruginosa infection.  相似文献   
86.
Immunity against Eimeria-infections is highly specific and it depends on cell-mediated effector mechanisms. Infections of BALB/c mice with 1000 sporulated oocysts of Eimeria falciformis led to protection against challenge infections. Treatment with the anticoccidium Toltrazuril, during primary infection, terminated the ongoing disease and did not interfere with the establishment of protective immunity against challenge infections. Mesenteric lymph node cells of infected, treated as well as non-treated and challenged BALB/c mice, showed a similar proliferation upon stimulation with parasite antigen. In contrast, neither cells of the Peyers patches, intraepithelial lymphocytes, nor spleen cells responded to stimulation with parasite antigens. Cells from all compartments and of all investigated groups proliferated and released the cytokines IFN- and IL-4 in response to the mitogen Concanavalin A. The number of cells releasing IFN- or IL-4 was not dependent on the status of infection or previous treatment with Toltrazuril. The serum IgG response against total sporozoite antigens of individual mice showed that in addition, a systemic humoral response developed in infected mice, independent of a previous drug treatment, although the specific IgG antibody concentration was higher in non-treated mice. Thus, Toltrazuril does not impair the parasite specific intestinal cellular and systemic antibody response and does not prevent the development of protection against challenge infection.  相似文献   
87.
Effector T cells fall into two subpopulations based on cytokine-secretion. Type 1 cells secrete IFN-gamma, whereas type 2 cells secrete IL-4, IL-10, and GM-CSF. NKT cells represent a third subpopulation that secretes similar cytokines and have been associated with immunoregulation. Using the TS/A adenocarcinoma, we assessed the phenotype and kinetics of tumor-infiltrating lymphocytes (TIL) in mice challenged subcutaneously in the mammary region. Flow cytometric analysis shows that T cells do not infiltrate the primary tumor site until days 7-14 following tumor challenge. Both CD4 and CD8 TILs were predominantly CD44(High) and expressed CD25, CD69, and CD95 cell surface activation markers. Activated CD4/CD44(High) TIL numbers reached peak levels at day 21 that precipitously decreased by day 28 whereas corresponding CD8 cell numbers progressively increased, however, at lower levels and with later kinetics. Intracellular cytokine staining showed that greater numbers of IL-4-producing Th2 cells were elicited and with earlier kinetics than that of IFN-gamma-producing Th1 cells. T cells co-expressing DX5 (CD3(+)/DX5(+)) emerged (>21 days), suggesting a recruitment of NK-like T cells at later stages of tumor progression. Moreover, tumors selectively up-regulated TGF-beta, MIF, and IP-10 gene expression at times as early as day 4, with peak levels at day 7 in vivo. Such gene expression remained elevated and correlated with a continued progression in tumor growth suggesting that preferential effector cell recruitment and production of select factors during different stages of tumor maturation may aid in regulating effective endogenous antitumor responses in progressive breast cancer.  相似文献   
88.
Summary Weight loss is the main symptom of so-called tumor cachexia. The pathogenetic mechanisms underlying cachexia are poorly understood; however, it appears that enhanced formation of cytokines such as interferon- and tumor necrosis factor- are involved. In 94 patients suffering from hematological neoplasias we compared body weight changes with serum neopterin, tryptophan, and kynurenine. Biochemical changes, the formation of neopterin, the degradation of tryptophan are closely related to interferon- activity. The majority of our patients had increased neopterin and decreased tryptophan concentrations. Weight loss was seen particularly in patients with higher neopterin and lower tryptophan values. An association between higher neopterin levels and greater weight loss was apparent at study entry and during the follow-up of patients. Our data support the concept that weight loss is closely linked to endogenous interferon- activity.Abbreviations NHL non-Hodgkin's lymphoma - HD Hodgkin's disease - MM multiple myeloma - MGUS monoclonal gammopathy of unknown significance - IFN- interferon- - TNF- tumor necrosis factor-  相似文献   
89.
Immune regulation by novel costimulatory molecules   总被引:10,自引:0,他引:10  
CD4 helper T (Th)-cells and the cytokines that they produce play essential regulatory roles in immune and autoimmune responses. Th activation and differentiation is regulated by costimulatory receptors. CD28 and CTLA-4 are important in maintaining the threshold of T-cell activation. ICOS and PD-1 are novel costimulatory receptors expressed on activated T-cells. B7-H3 recognizes a putative costimulatory receptor on activated T-cells. Here we summarize the latest developments in the novel costimulatory molecules and their roles in regulating Th activation, differentiation, and function.  相似文献   
90.
Notch1 proteins are involved in binary cell fate decisions. To determine the role of Notch1 in the differentiation of CD4(+) Th1 versus Th2 cells, we have compared T helper polarization in vitro in naive CD4(+) T cells isolated from mice in which the N1 gene is specifically inactivated in all mature T cells. Following activation, Notch1-deficient CD4(+) T cells transcribed and secreted IFN-gamma under Th1 conditions and IL-4 under Th2 conditions at levels similar to that of control CD4(+) T cells. These results show that Notch1 is dispensable for the development of Th1 and Th2 phenotypes in vitro. The requirement for Notch1 in Th1 differentiation in vivo was analyzed following inoculation of Leishmania major in mice with a T cell-specific inactivation of the Notch1 gene. Following infection, these mice controlled parasite growth at the site of infection and healed their lesions. The mice developed a protective Th1 immune response characterized by high levels of IFN-gamma mRNA and protein and low levels of IL-4 mRNA with no IL-4 protein in their lymph node cells. Taken together, these results indicate that Notch1 is not critically involved in CD4(+) T helper 1 differentiation and in resolution of lesions following infection with L. major.  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