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   1521篇
  免费   277篇
  国内免费   44篇
  1842篇
  2024年   14篇
  2023年   49篇
  2022年   74篇
  2021年   107篇
  2020年   81篇
  2019年   105篇
  2018年   76篇
  2017年   59篇
  2016年   55篇
  2015年   73篇
  2014年   122篇
  2013年   123篇
  2012年   89篇
  2011年   88篇
  2010年   52篇
  2009年   47篇
  2008年   59篇
  2007年   42篇
  2006年   62篇
  2005年   58篇
  2004年   38篇
  2003年   41篇
  2002年   33篇
  2001年   17篇
  2000年   27篇
  1999年   15篇
  1998年   22篇
  1997年   23篇
  1996年   21篇
  1995年   14篇
  1994年   23篇
  1993年   21篇
  1992年   16篇
  1991年   17篇
  1990年   11篇
  1989年   9篇
  1988年   11篇
  1987年   4篇
  1986年   6篇
  1985年   9篇
  1984年   13篇
  1983年   3篇
  1982年   5篇
  1981年   2篇
  1979年   1篇
  1978年   1篇
  1977年   1篇
  1976年   1篇
  1975年   1篇
  1972年   1篇
排序方式: 共有1842条查询结果,搜索用时 15 毫秒
31.
Recently, variants (rs2568494, rs2869967 and rs3821104) in the IREB2, FAM13A and XRCC5 genes were found to be associated with chronic obstructive pulmonary disease (COPD) in non-Asian populations by genome-wide association study (GWAS) analysis. To evaluate whether variants in these genes are related to COPD in Chinese Han population, we investigated COPD patients of Chinese Han ethnicity from Mainland China. Significant differences in genotypic distributions (χ2 = 6.319, p = 0.042 for rs2869967; χ2 = 6.062, p = 0.048 for rs3821104) and allele distributions (χ2 = 4.014, p = 0.045 for rs2869967; χ2 = 5.607, p = 0.018 for rs3821104) were observed between patients and control subjects for variants rs2869967 and rs3821104, whereas no statistically significant associations for genotypic and allelic distribution between IREB2 rs2568494 and COPD phenotype (p > 0.05) were identified. Our results support that FAM13A rs2869967 and XRCC5 rs3821104 are associated with COPD in Chinese Han population.  相似文献   
32.
We examined the protective effect of intratracheal immunization with Pseudomonas aeruginosa pili protein against respiratory infection caused by P. aeruginosa. Mice were immunized intratracheally or subcutaneously with purified pili protein or bovine serum albumin as a control. Intratracheally but not subcutaneously pili protein-immunized mice showed significant improvement of survival after intratracheal challenge with the PAO1 strain. Furthermore, bacterial cell counts in pili protein-immunized murine lungs were significantly decreased compared to controls at 18 h after the challenge. Antipili protein antibody titers in bronchoalveolar lavage fluid of intratracheally pili protein-immunized mice were higher than in bovine serum albumin immunized mice. However, antipili antibody titers were not increased in bronchoalveolar lavage fluid of subcutaneously pili protein-immunized mice, despite the high serum antipili antibody titers. Inoculation of P. aeruginosa induced immediate increases in interleukin-12 and interferon-gamma in bronchoalveolar lavage fluid of pili protein-immunized mice, reflecting an adequate and rapid immune response against P. aeruginosa respiratory tract infection. Our findings suggest that intratracheal pili protein immunization is effective against respiratory tract infection caused by P. aeruginosa in mice.  相似文献   
33.
阿米洛利抑制NHE-1减轻低氧性肺动脉平滑肌细胞增殖   总被引:1,自引:0,他引:1  
目的:研究Na^+/H^+交换抑制剂阿米洛利对低氧刺激的大鼠肺动脉平滑肌细胞(PASMCs)增殖的影响,以及Na^+/H^+交挟体-l(NHE-1)活性和表达的变化.方法:常氧(21%O2)或低氧(2%O2)条件下培养PASMCs,并分别给予浓度为1.653、3.125、6.25、12.5、25和50μmol/L.等不同浓度的阿米洛利,培养24h,采用MTT比色实验和免疫组化检测PCNA阳性细胞率的方法反映细胞增殖情况,同时采用激光共聚焦检测细胞内pH以反映Na^+/H^+交换体-1活性,RT—PCR法检测Na^+/H^+交换体-1mRNA的表达量.结果:低氧培养的PASMCs细胞内pH升高,NHE—1mRNA的表达增多,而阿米洛利可以降低细胞内pH,减少NHE—1mRNA的表达量。同时低氧较常氧培养MTT光吸收值较常氧培养明显升高。PCNA阳性细胞率明显增高,而给予阿米洛利时上述两个指标随药物浓度增加而逐渐下降。结论:低氧可以激活PASMCs细胞膜上的E—1,增加其mRNA水平表达量,使细胞内碱化,促进细胞增殖,而Na^+/H^+交换抑制剂阿米洛利可以抑制其活性,减少mRNA水平的表达,导致细胞内酸化,从而抑制细胞增殖,并且此抑制作用在3.125~50μmol/L.浓度范围内呈现明显的浓度依赖性。  相似文献   
34.
Epithelial–mesenchymal transition (EMT) is associated with pulmonary fibrosis, including idiopathic pulmonary fibrosis (IPF). In this study, we investigated EMT of human pulmonary epithelial-derived cells (A549). A549 cells was either cultured by itself or co-cultured with THP-1 macrophages under normoxic (21% O2) and hypoxic (2% O2) conditions. We evaluated the presence of EMT by determining the expression of EMT markers, E-cadherin, vimentin, and fibronectin. To determine the role of TGF-β1 and IL-1β in EMT of the A549 cells, we analyzed the effects of blocking their activity with TGF-β1 inhibitor or IL-1β neutralizing antibody respectively. The A549 cells presented EMT when they were co-cultured with THP-1 macrophages. The EMT of the A549 cells co-cultured with THP-1 macrophages was exacerbated under hypoxia. In addition, the EMT were prevented by the addition of TGF-β1 type I receptor kinase inhibitor. The hypoxic condition increased the mRNA levels of TGF-β1 in A549 cells and THP-1 macrophages and that of IL-1β in THP-1 macrophages when each cells were co-cultured. Anti-IL-1β neutralizing antibody attenuated TGF-β1 secretion in co-culture media under hypoxic conditions. Thus, the IL-1β from THP-1 macrophages up-regulated the TGF-β1 from A549 cells and THP-1 macrophages, and then the TGF-β1 from both cells induced and promoted the EMT of A549 cells when they were co-cultured under hypoxia. Together, these results demonstrate that the interaction between type II pneumocytes and macrophages under hypoxia is necessary for the development of pulmonary fibrosis.  相似文献   
35.
目的通过典型病例回顾探讨自身免疫性大疱病糖皮质激素治疗过程中合并肺曲霉病的诊断和治疗情况。方法报告3例自身免疫性大疱病合并侵袭性肺曲霉病病例。3例病例均行痰镜检、培养、抗原检测、胸部CT或者坏死组织病理检查。分离病原菌经形态学和分子生物学鉴定为烟曲霉、黄曲霉和刺孢裸胞壳。结果 3例病例证实为侵袭性肺曲霉病。进行以伏立康唑为主的综合治疗后均治愈。结论自身免疫性大疱病糖皮质激素治疗过程中应警惕肺曲霉病的发生。多种实验室检查可以帮助早期诊断,提高疗效。  相似文献   
36.
The pulmonary alveolar epithelium is composed of two morphologically distinct cell types, type I (TI) and type II (TII) cells. Alveolar TII cells synthesize, secrete, and recycle surfactant components; contain ion transporters; and secrete immune effector molecules. In response to alveolar injury, TII cells have the capacity to act as progenitor cells, proliferating and transdifferentiating into TI cells. Although various proteins are associated with TII cells, a plasma membrane marker specific to human TII cells that would be useful for identification in tissue and for isolating this cell type has not been described previously. We devised a strategy to produce a monoclonal antibody (MAb) specific to the apical surface of human TII cells and developed an MAb that appears to be specific for human TII cells. The antibody recognizes a 280- to 300-kDa protein, HTII-280, which has the biochemical characteristics of an integral membrane protein. HTII-280 is detected by week 11 of gestation and is developmentally regulated. HTII-280 is useful for isolating human TII cells with purities and viabilities >95%. HTII-280 is likely to be a useful morphological and biochemical marker of human TII cells that may help to advance our understanding of various lung pathological conditions, including the origin and development of various lung tumors. (J Histochem Cytochem 58:891–901, 2010)  相似文献   
37.
A novel series of formoterol–phthalazinone hybrids were synthesised and evaluated as dual pharmacology β2-adrenoceptor agonists and PDE4 inhibitors. Most of the hybrids displayed high β2-adrenoceptor agonist and moderate PDE4 inhibitory activities. The most potent compound, (R,R)-11c, exhibited agonist (EC50 = 1.05 nM, pEC50 = 9.0) and potent PDE4B2 inhibitory activities (IC50 = 0.092 μM).  相似文献   
38.
39.
Congenital generalized lipodystrophy (CGL) and pulmonary arterial hypertension (PAH) have recently been associated with mutations in the caveolin‐1 ( CAV1 ) gene, which encodes the primary structural protein of caveolae. However, little is currently known about how these CAV1 mutations impact caveolae formation or contribute to the development of disease. Here, we identify a heterozygous F160X CAV1 mutation predicted to generate a C‐terminally truncated mutant protein in a patient with both PAH and CGL using whole exome sequencing, and characterize the properties of CAV1 , caveolae‐associated proteins and caveolae in skin fibroblasts isolated from the patient. We show that morphologically defined caveolae are present in patient fibroblasts and that they function in mechanoprotection. However, they exhibited several notable defects, including enhanced accessibility of the C‐terminus of wild‐type CAV1 in caveolae, reduced colocalization of cavin‐1 with CAV1 and decreased stability of both 8S and 70S oligomeric CAV1 complexes that are necessary for caveolae formation. These results were verified independently in reconstituted CAV1 ?/? mouse embryonic fibroblasts. These findings identify defects in caveolae that may serve as contributing factors to the development of PAH and CGL and broaden our knowledge of CAV1 mutations associated with human disease.   相似文献   
40.
目的:观察肺纤维化初期肺动脉高压大鼠肺动脉血管反应性的变化。方法:66只雄性SD大鼠,随机分为博莱霉素(BLM)组和手术对照(Sham)组。BLM组为气管内一次性滴注BLM(5 mg/kg);Sham组为气管内滴注等容量的生理盐水(NS)。应用离体血管张力检测技术测定大鼠肺动脉血管反应性变化;用HE显示肺动脉壁病理形态学变化;Masson染色检测肺纤维化程度;右心漂浮导管技术测定大鼠平均肺动脉压。结果:①BLM组大鼠的肺动脉血管(保留内皮和去内皮)对苯肾上腺素(PE)的收缩反应均弱于Sham组(P均〈0.05)。②BLM组大鼠肺动脉血管(保留内皮)对氯化乙酰胆碱(Ach)的舒张反应明显弱于Sham组(P〈0.01)。③Sham组有内皮的肺动脉血管对L-NAME和PE联合作用的收缩反应明显强于PE单独作用(P〈0.01),而BLM组有内皮肺动脉血管对L-NAME和PE联合作用的收缩反应与对PE单独作用比,其差异无统计学意义(P〉0.05)。④BLM组肺动脉内皮细胞脱落。⑤BLM组大鼠肺组织呈现纤维增生初期的病理特征,且大鼠的平均肺动脉压明显高于Sham组(P〈0.05)。结论:肺纤维化形成初期肺动脉高压大鼠肺动脉血管反应性出现异常。  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