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   162596篇
  免费   16097篇
  国内免费   10931篇
耳鼻咽喉   1732篇
儿科学   2233篇
妇产科学   1374篇
基础医学   15025篇
口腔科学   2865篇
临床医学   19955篇
内科学   19902篇
皮肤病学   1924篇
神经病学   6485篇
特种医学   6178篇
外国民族医学   68篇
外科学   16821篇
综合类   35503篇
现状与发展   49篇
一般理论   10篇
预防医学   13579篇
眼科学   3635篇
药学   17378篇
  184篇
中国医学   12584篇
肿瘤学   12140篇
  2024年   503篇
  2023年   2099篇
  2022年   4921篇
  2021年   7655篇
  2020年   6142篇
  2019年   4622篇
  2018年   5074篇
  2017年   5178篇
  2016年   4864篇
  2015年   7771篇
  2014年   9491篇
  2013年   9902篇
  2012年   14293篇
  2011年   15354篇
  2010年   11595篇
  2009年   9677篇
  2008年   10865篇
  2007年   10398篇
  2006年   9761篇
  2005年   8272篇
  2004年   5865篇
  2003年   5507篇
  2002年   4516篇
  2001年   3429篇
  2000年   2639篇
  1999年   2011篇
  1998年   1158篇
  1997年   1099篇
  1996年   868篇
  1995年   786篇
  1994年   601篇
  1993年   377篇
  1992年   402篇
  1991年   324篇
  1990年   296篇
  1989年   226篇
  1988年   196篇
  1987年   186篇
  1986年   141篇
  1985年   110篇
  1984年   57篇
  1983年   44篇
  1982年   33篇
  1981年   38篇
  1980年   20篇
  1979年   42篇
  1977年   19篇
  1976年   17篇
  1974年   22篇
  1973年   28篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The effects of long-term smoking on mitochondrial DNA (mtDNA) deletions in hair follicles were investigated in subjects with different antioxidant capacity. Twenty-two male smokers with a smoking index of greater than 5 pack-years and without any known systemic diseases were recruited for this study. Forty healthy nonsmoking males were included as controls. We found that the concentrations of ascorbate and alpha-tocopherol and the activities of glutathione S-transferase (GST) and glutathione peroxidase in blood plasma were significantly decreased in smokers. The levels of glutathione and protein thiols in whole blood and the incidence of a 4,977 bp deletion of mtDNA (dmtDNA) in hair follicles were significantly increased in smokers. A significantly higher incidence of the 4,977 bp dmtDNA was found in smokers with plasma GST activity less than 5.66 U/l (OR = 7.2, P = 0.020). Using multiple covariate ANOVA and logistic regression, we found that age and low plasma GST activity were the only two risk factors for the 4,977 bp dmtDNA. These results suggest that smoking depletes antioxidants and causes mtDNA deletions and that plasma GST may play an important role in the preservation of the mitochondrial genome in tissue cells of smokers.  相似文献   
992.
Acute lung injury (ALI) induced by lipopolysaccharide (LPS) is a major cause of mortality among humans. ALI is characterized by microvascular protein leakage, neutrophil influx, and expression of proinflammatory mediators, followed by severe lung damage. LPS binding to its receptors is the crucial step in the causation of these multistep events. LPS binding and signaling involves CD14 and Toll-like receptor 4 (TLR4). However, the relative contributions of CD14 and TLR4 in the induction of ALI and their therapeutic potentials are not clear in vivo. Therefore, the aim of the present study was to compare the roles of CD14 and TLR4 in LPS-induced ALI to determine which of these molecules is the more critical target for attenuating ALI in a mouse model. Our results show that CD14 and TLR4 are necessary for low-dose (300-microg/ml) LPS-induced microvascular leakage, NF-kappaB activation, neutrophil influx, cytokine and chemokine (KC, macrophage inflammatory protein 2, tumor necrosis factor alpha, interleukin-6) expression, and subsequent lung damage. On the other hand, when a 10-fold-higher dose of LPS (3 mg/ml) was used, these responses were only partially dependent on CD14 and they were totally dependent on TLR4. The CD14-independent LPS response was dependent on CD11b. A TLR4 blocking antibody abolished microvascular leakage, neutrophil accumulation, cytokine responses, and lung pathology with a low dose of LPS but only attenuated the responses with a high dose of LPS. These data are the first to demonstrate that LPS-induced CD14-dependent and -independent (CD11b-dependent) signaling pathways in the lung are entirely dependent on TLR4 and that blocking TLR4 might be beneficial in lung diseases caused by LPS from gram-negative pathogens.  相似文献   
993.
Multi-virulence-locus sequence typing (MVLST) was used to analyze isolates from two major listeriosis outbreaks in the United States in 1998 and 2002 that were due to consumption of contaminated hot dogs and turkey deli meat, respectively. MVLST demonstrated high epidemiological relevance and indicated that the two outbreaks were the result of one epidemic.  相似文献   
994.
应用肿瘤基因芯片筛选早期肺鳞癌相关基因   总被引:1,自引:2,他引:1  
目的: 研究人早期肺鳞癌发生相关基因表达谱, 探讨肺鳞癌发生的分子机制。方法:选取人早期肺鳞癌组织以及相应正常组织,提取RNA, 与含480个与肿瘤相关基因的芯片杂交, 结果经SuperArray Image 软件分析后比较两种组织中的差异表达基因。结果:共筛查出差异表达基因192 条,其中表达上调基因127 条, 下调基因65条; 按照基因功能可分为运输载体、代谢相关基因、细胞信号转导分子、细胞骨架、转录调控因子基因。结论:基因芯片可用于早期肺鳞癌相关基因表达谱的筛查,可为明确早期肺鳞癌发生机制提供重要参考。  相似文献   
995.
目的结合移植物细胞因子表达的实验和临床病例研究,探索早期诊断小肠移植急性排斥反应的细胞因子相关的敏感指标。方法①两例短肠综合症患者接受活体小肠移植术。定期或病情变化时随时行内镜组织学检查并测定受体大鼠移植物sIL-2R、IL-4、IL-6和IFN-γ表达水平。②BN-LEW大鼠部分小肠移植,A组:SBT(n=20);B组:SBT+FK506(2.5mg/kg,n=20),术后第1、4、7、14和30天测定受体大鼠移植物sIL-2R、IL-4、IL-6和IFN-γ水平同时取移植肠黏膜行病理组织学检查。结果首例术后67d发生排斥反应,第2例于术后20d和80d分别发生强烈排斥反应。发生排斥反应相应时相均发生IL-2Rα、IFN-γ表达的显著升高,排斥反应控制后IL-2Rα迅速恢复,但IFN-γ仍在较高水平维持较长时间。A组大鼠术后第1天始即显示IL-2Rα、IFN-γ和IL-6表达的显著升高,于术后7d达到最高,移植后14d仍在高水平。B组仅术后第1天出现IL-2Rα、IFN-γ和IL-6表达的迅速升高,第4天已恢复至基本正常。结论移植物IL-2Rα、IFN-γ表达的升高与小肠移植急性排斥反应密切相关,有望成为早期诊断小肠移植急性排斥反应的敏感指标。  相似文献   
996.
目的:砒石是化腐生肌的常用中药,其主要成分是三氧化二砷(As2O3)。本研究通过观察As2O3对基质金属蛋白酶(MMPs)活性、基质金属蛋白酶组织抑制因子-1(TIMP-1)及转化生长因子β1(TGF-β1)表达影响,探讨化腐中药能否调节胶原代谢,从而治疗慢性皮肤溃疡。方法:明胶酶谱法检测大鼠中性粒细胞(PMNs)来源的MMP-9活性、人成纤维细胞(hFb)分泌的MMP-1、MMP-2的活性,免疫细胞化学法检测hFb TIMP-1、TGF-β1的表达。结果:As2O3浓度在50 mg/L时可以提高大鼠PMNs来源的MMP-9的活性(P<0.01);在0.8 mg/L可以提高hFb分泌的MMP-1、MMP-2的活性(分别P<0.01);同时As2O3作用于hFb 6 h、12 h、18 h后,TIMP-1、TGF-β1表达持续降低(P<0.01)。结论:As2O3在一定范围内可提高PMNs来源的MMP-9的活性;也可提高hFb分泌的MMP-1、MMP-2的活性,同时抑制hFbTIMP-1、TGF-β1的表达。提示砷类制剂可通过提高多种MMPs的活性,降低TIMP-1的表达从而发挥化腐作用。  相似文献   
997.
A dipstick dye immunoassay (DDIA) was developed to detect immunoglobulin G (IgG) or IgM antibodies of toxoplasmosis infection in humans. The assays employ a blue colloidal dye particles (D-1) conjugated to sheep anti-human IgG and rabbit anti-human IgM as the visualizing agents and a soluble antigen of tachyzoites of Toxoplasma gondii strain RH (TSA) as the detective antigen. The mixture of dye-labeled anti-human antibody-special human antibody was captured by TSA onto a nitrocellulose membrane dipstick by means of immunochromatography. The assays are rapid (the whole test can be completed within 15 min), simple, and cheap, and they don't require any equipment. They are sensitive and specific for the detection of anti-Toxoplasma IgG or IgM antibodies and generally agree closely with the results from the enzyme-linked immunosorbent assay. The assays are especially suitable for field applications.  相似文献   
998.
Specific immunoglobulin G antibody for severe acute respiratory syndrome (SARS) coronavirus was detected in maternal blood, umbilical blood, and amniotic fluid from a pregnant SARS patient. Potential protection of fetus from infection was suggested.  相似文献   
999.
1000.
体外反搏对血液流变性和血小板聚集性的影响   总被引:2,自引:0,他引:2  
观察40例心脑血管疾病患者体外反搏前后血液流变性和血小板聚集性变化。结果表明,反搏后全血比及还原比粘度、血浆粘度有不同程度的下降(P<0.05~0.01)。反搏治疗后,1~5min血小板聚集率、最大聚集率和最大聚集速度较反搏前均明显降低(P<0.05~0.01),而5min解聚率则明显增加(P<0.05)。提示体外反搏治疗不仅影响血液动力学,而且明显降低血液粘度,对血小板聚集功能有明显抑制作用。  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