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   1686篇
  免费   241篇
  国内免费   16篇
  2024年   8篇
  2023年   26篇
  2022年   58篇
  2021年   101篇
  2020年   96篇
  2019年   73篇
  2018年   58篇
  2017年   62篇
  2016年   53篇
  2015年   92篇
  2014年   174篇
  2013年   148篇
  2012年   107篇
  2011年   118篇
  2010年   75篇
  2009年   59篇
  2008年   64篇
  2007年   75篇
  2006年   71篇
  2005年   39篇
  2004年   46篇
  2003年   41篇
  2002年   33篇
  2001年   10篇
  2000年   19篇
  1999年   15篇
  1998年   17篇
  1997年   24篇
  1996年   13篇
  1995年   13篇
  1994年   14篇
  1993年   17篇
  1992年   13篇
  1991年   9篇
  1990年   7篇
  1989年   8篇
  1988年   6篇
  1987年   5篇
  1986年   5篇
  1985年   6篇
  1984年   8篇
  1983年   4篇
  1982年   9篇
  1981年   5篇
  1980年   6篇
  1979年   6篇
  1978年   6篇
  1977年   4篇
  1971年   3篇
  1970年   3篇
排序方式: 共有1943条查询结果,搜索用时 31 毫秒
101.
目的:探讨用表面增强激光解吸电离飞行时间质谱(SELDI-TOF-MS)技术筛查肺癌血清特异性蛋白质的临床意义。方法:应用SELDI-TOF-MS对35例正常对照组、43例治疗前肺癌病人的血清样品进行蛋白质指纹图谱测定,用BioMarker Wizard 3.01及BioMarker Parrern System 5.01分析软件对测得的数据进行处理及建立诊断模型。结果:共检测到251个蛋白质峰,筛选出差异蛋白质峰11个,以质荷比(m/z)分别为M2799_26,M3227_41,M5739_70和M8164_30的4个蛋白质峰为依据组合构建分类决策树模型,分出5个终节点。决策树模型的原始判别总准确率为91.0%(71/78),敏感性为88.4%(38/43),特异性为94.3%(33/35);交叉验证总准确率为85.9%(67/78),敏感性为88.4%(38/43),特异性为82.9%(29/35)。结论:SELDI-TOF-MS在肺癌血清特异性蛋白质的筛选及诊断模型的建立有一定的临床意义。  相似文献   
102.
目的:观察硝黄散外敷联合加味五虎汤口服治疗痰热闭肺型肺炎支原体肺炎(MPP)患儿对肺功能和血清肿瘤坏死因子-α(TNF-α)、γ-干扰素(IFN-γ)、白介素-4(IL-4)水平的影响。方法:研究对象为我院2019年6月~2021年1月期间收治的MPP患儿80例,采用随机数字表法将患儿分为对照组(n=40,阿奇霉素抗感染治疗)和研究组(n=40,对照组基础上加用硝黄散外敷联合加味五虎汤口服治疗),均治疗7 d。比较两组患儿临床疗效,比较两组治疗前、治疗7 d后的中医证候积分、临床症状改善情况、肺功能和血清TNF-α、IFN-γ、IL-4水平。结果:研究组治疗7 d后的临床总有效率为92.50%(37/40),高于对照组的72.50%(29/40),差异有统计学意义(P<0.05)。与对照组相比,研究组的症状(咳嗽憋喘、发热、肺部干湿啰音)消失时间均更短(P<0.05)。与对照组相比,研究组治疗7 d后用力肺活量(FVC)、最高呼气峰流速(PEF)、第1秒最大呼气容积(FEV1)、FEV1/FVC均更高(P<0.05),研究组治疗7 d后的中医证候积分及血清TNF-α、IFN-γ和IL-4水平均更低(P<0.05)。结论:痰热闭肺型MPP患儿采用硝黄散外敷联合加味五虎汤口服治疗,可有效缩短患儿症状消失时间,显著改善其肺功能、血清炎症因子水平,疗效显著。  相似文献   
103.
摘要 目的:研究脂蛋白脂肪酶(lipoprotein lipase,LPL)基因敲除对雨蛙素诱导的高脂血症急性胰腺炎小鼠肺损伤的影响。方法:将C57BL/6小鼠分为三组,Control组和AP-Model组为野生型C57 BL/6小鼠,LPL ko组为LPL基因敲除C57 BL/6小鼠;Control组小鼠正常饲养,AP-Model和LPL ko组小鼠建立高脂血症性急性胰腺炎模型,比较三组小鼠死亡率、胰腺和肺病理损伤以及血清淀粉酶(amylase, AMY)、丙二醛(malondialdehyde, MDA)、肿瘤坏死因子-α(Tumor necrosis factor-α, TNF-α)和白介素-6(Interleukin-6, IL-6)含量。结果:急性胰腺炎建立48 h后,Control组、AP-Model组和LPL ko组小鼠死亡率分别为0 %、20 %和40 %。与Control组相比,AP-Model组和LPL ko组小鼠急性胰腺炎诱导24和48 h后的胰腺和肺组织湿/干重比值,胰腺和肺组织病理评分,血清AMY、MDA、TNF-α和IL-6含量均显著升高(P<0.05);与AP-Model组相比,LPL ko组小鼠急性胰腺炎诱导24和48 h后的胰腺和肺组织湿/干重比值,胰腺和肺组织病理评分,血清AMY、MDA、TNF-α和IL-6含量均显著升高(P<0.05)。结论:LPL基因敲除小鼠急性高脂血症性胰腺炎肺损伤更严重,其机制可能与LPL基因敲除引起更强的氧化应激和炎症有关。  相似文献   
104.
胡滨滨  张明 《生物信息学》2022,20(2):124-135
为探讨RNA m6A甲基化调节因子在肺腺癌中的作用,从TCGA数据库下载肺腺癌患者的RNA表达数据和临床数据。通过limma软件包分析12种m6A调节剂的表达情况。使用Pheatmap、vioplot和corrplot软件包生成热图、小提琴图和表达相关图。采用Kaplan-Meier方法分别计算肺腺癌中12种RNA m6A调节因子的生存曲线。使用Cox回归和Kaplan-Meier方法分析TCGA肺腺癌患者的总体存活相关的临床病理学特征。最后用Kruskal(KS)检验和logistic回归分析临床病理学特征与HNRNPC表达的关系。 在肺腺癌的TCGA队列中,发现HNRNPC、WTAP、YTHDF3、FTO、ZC3H13、METTL14、METTL3、YTHDF1、YTHDF2这些基因是差异表达的。Kaplan-Meier生存分析显示,在这些差异表达的基因中仅仅HNRNPC和YTHDF2的表达与生存显著相关。然后,通过多因素Cox回归结果表明HNRNPC的表达在肺腺癌TCGA队列中是个独立危险因素。最后,HNRNPC在肺腺癌中的表达与临床分期(IV vs I, OR=3.692 308)和组织浸润(T2 vs T1, OR=1.776 471;T4 vs T1, OR=6.303 03)显著相关(所有p<0.05)。 结论认为HNRNPC可能作为肺腺癌的独立的预后因子。  相似文献   
105.
本文报告了树肺脏的一般结构和超微结构。与人和灵长目相似,其肺实质也是由导气部和呼吸部构成。但不同的是其细支气管粘膜形成很高的皱襞。在电镜下Clara细胞电子密度高,顶部胞质中含有大量膜包颗粒,这些结构与大白鼠和家兔的结构相似。许多毛细血管外方都包绕着基膜和肺泡Ⅰ型上皮细胞的胞质。气血屏障由肺泡上皮细胞、融合的基膜和内皮细胞胞质构成。说明树肺脏不但是呼吸器官,也是一些激素和介质产生及代谢的重要器官。本文为研究树的正常生理功能及分类提供形态学资料。  相似文献   
106.
Endotoxin shock is characterized by systemic hypotension, hyporeactiveness to vasoconstrictors and acute lung edema. A nitric oxide synthase (NOS) inhibitor, NG-monomethyl-L-arginine (L-NMMA) has been shown to be effective in reversing acute lung injury. In the present study, we evaluated the effects of NOS blockade by different mechanisms on the endotoxin-induced changes. In anesthetized rats, lipopolysaccharide (LPS,Klebsiella pneumoniae) was administered intravenously in a dose of 10 mg/kg. LPS caused sustained systemic hypotension accompanied by an eightfold increase of exhaled NO during an observation period of 4 h. After the experiment, the lung weight was obtained and lung tissues were taken for the determination of mRNA expressions of inducible NOS (iNOS), interleukin-1 (IL-1) and tumor necrosis factor--(TNF-). Histological examination of the lungs was also performed. In the control group injected with saline solution, mRNA expressions of iNOS, IL-1 and TNF- were absent. Four hours after LPS, the mRNA expressions of iNOS and IL-1 were still significantly enhanced, but TNF- was not discernibly expressed. LPS also caused a twofold increase in lung weight. Pathological examination revealed endothelial damage and interstitial edema. Various NOS inhibitors were given 1 h after LPS administration. These agents included N-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg), a constitutive NOS and iNOS inhibitor; S,S-1,4-phenylene-bis-(1,2-ethanedinyl) bis-isothiourea dihydrobromide (1,4-PBIT, 10 mg/kg), a relatively specific iNOS inhibitor, and dexamethasone (3 mg/kg), an inhibitor of iNOS expression. These NOS inhibitors all effectively reversed the systemic hypotension, reduced the exhaled NO concentration and prevented acute lung injury. The LPS-induced mRNA expressions of iNOS and IL-1 were also significantly depressed by these NOS inhibitors. Our results suggest that NO production through the iNOS pathway is responsible for endotoxin-induced lung injury. Certain cytokines such as IL-1 are possibly involved. These changes are minimized by NOS inhibitors through different mechanisms.  相似文献   
107.
Diesel exhaust particles consist of various organic chemicals, heavy metals, and carbon particles. Knowledge of the fate of organic chemicals and carbon particles in the lungs is important to determine the mechanisms responsible for lung tumors. In the present study, diesel particle extracts were found to show mutagenicity for YG3003, a sensitive strain to some oxidative mutagens, as well as other mutant strains, and those of lung tissues obtained from lung cancer patients exhibited potent mutagenicity. Formation of 8-hydroxyguanosine (8-OHdG) as a biomarker of oxidative damage was analyzed with in vitro and in vivo assay systems. The 8-OHdG was detected in all 22 cases of lung tissues with carcinomas tested and their levels increased with the increasing age of the patients, suggesting a correlation between age and the presence of carbon particles in lung tissues. Therefore, the formation of 8-OHdG due to diesel exhaust particles was investigated via intratracheal injections into mice. 8-OHdG formation was elevated when carboneceous particles, after removal of organic chemicals with various solvents, were administered to mice, but it was not elevated when polyaromatic compounds such as benzo[a]pyrene, 1,8-dinitropyrene, and 1-nitropyrene were used in the same procedure in mice. The carboneceous particles were formed from a giant particle that was aggregated by micro-particles with diameters of 1.47 +/- 1.34 to 1.05 +/- 0.83 microm. These results suggest that carboneceous particles, but not mutagens and carcinogens, promote the formation of 8-OHdG, and that as a mechanism, alveolar macrophages may be involved in oxidative damage. The oxidative damage may be due to the fact that the mutation is involved with the generation of a hydroxyl radical during phagocytosis, and the hydroxyl radical leads to hydroxylation at the C-8 position of the deoxyguanosine residue in the DNA.  相似文献   
108.
Benzene is an occupational and environmental toxicant. The main human health concern associated with benzene exposure is leukemia. The toxic effects of benzene are dependent on its metabolism by the cytochrome p450 enzyme system. The cytochrome p450 enzymes CYP2E1 and CYP2F2 are the major contributors to the bioactivation of benzene in rats and mice. Although benzene metabolism has been shown to occur with mouse and human lung microsomal preparations, little is known about the ability of human CYP2F to metabolize benzene or the lung cell types that might activate this toxicant. Our studies compared bronchiolar derived (BEAS-2B) and alveolar derived (A549) human cell lines for benzene metabolizing ability by evaluating the roles of CYP2E1 and CYP2F1. BEAS-2B cells that overexpressed CYP2F1 and recombinant CYP2F1 were also evaluated. BEAS-2B cells overexpressing the enzyme CYP2F1 produced 47.4 +/- 14.7 pmols hydroxylated metabolite/10(6) cells/45 min. The use of the CYP2E1-selective inhibitor diethyldithiocarbamate and the CYP2F2-selective inhibitor 5-phenyl-1-pentyne demonstrated that both CYP2E1 and CYP2F1 are important in benzene metabolism in the BEAS-2B and A549 human lung cell lines. The recombinant expressed human CYP2F1 enzyme had a K(m) value of 3.83 microM and a V(max) value of 0.01 pmol/pmol p450 enzyme/min demonstrating a reasonably efficient catalysis of benzene metabolism (V(max)/K(m) = 2.6). Thus, these studies have demonstrated in human lung cell lines that benzene is bioactivated by two lung-expressed p450 enzymes.  相似文献   
109.
The role of ephrins and Eph receptors in cancer   总被引:10,自引:0,他引:10  
Eph receptors are the largest receptor tyrosine kinase family of transmembrane proteins with an extracellular domain capable of recognizing signals from the cells’ environment and influencing cell–cell interaction and cell migration. Ephrins are the ligands to Eph receptors and stimulate bi-directional signaling of the Eph/ephrin axis. Eph receptor and ephrin overexpression can result in tumorigenesis as related to tumor growth and survival and is associated with angiogenesis and metastasis in many types of human cancer. Recent data suggest that Eph/ephrin signaling could play an important role in the development of novel inhibition strategies and cancer treatments to potentially target this receptor tyrosine kinase and/or its ligand. A deeper understanding of the molecular basis for normal versus defective cell–cell interaction through the Eph/ephrin axis will enable the potential development of novel cancer treatments. This review emphasizes the biology of Eph/ephrin as well as the potential for novel targeted therapy through this pathway.  相似文献   
110.
Proteomic signature of human cancer cells   总被引:3,自引:0,他引:3  
We assessed proteomic profiles as biomarkers for monitoring cell phenotypes. Protein expression profiles were obtained by fluorescence two-dimensional difference gel electrophoresis (2-D-DIGE), in which quantitative ability is improved by labeling proteins with fluorescent dyes prior to electrophoresis. Integrated protein spot intensities were analyzed by a statistical approach. The proteomic data of two groups of cell lines: (1) adenocarcinoma (AC) cell lines derived from lung, pancreas and colon tissues and (2) lung cancer cell lines with different histological backgrounds, including AC, squamous cell carcinoma and small cell carcinoma, were assessed on the basis of prior biological information. Hierarchical clustering analysis and principal component analysis were used to divide the cell lines into subgroups on the basis of similarities between their protein expression profiles. The majority of cell lines were grouped according to their organ of origin or histological background. A machine-learning algorithm selected 32 protein spots that were responsible for the classification. The results indicate that proteomic data generated by 2-D-DIGE can provide a signature of essential cell phenotypes, suggesting that it might be possible to apply this technique to developing tumor markers that could identify the organ of origin of metastatic tumors and contribute to the differential diagnosis of lung cancer.  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