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   28373篇
  免费   2778篇
  国内免费   2258篇
耳鼻咽喉   204篇
儿科学   311篇
妇产科学   315篇
基础医学   3691篇
口腔科学   478篇
临床医学   3882篇
内科学   4567篇
皮肤病学   247篇
神经病学   1443篇
特种医学   1005篇
外国民族医学   21篇
外科学   2959篇
综合类   4472篇
现状与发展   9篇
一般理论   4篇
预防医学   1736篇
眼科学   717篇
药学   2854篇
  32篇
中国医学   1542篇
肿瘤学   2920篇
  2024年   112篇
  2023年   503篇
  2022年   1298篇
  2021年   1643篇
  2020年   1227篇
  2019年   978篇
  2018年   1074篇
  2017年   911篇
  2016年   873篇
  2015年   1380篇
  2014年   1693篇
  2013年   1339篇
  2012年   2009篇
  2011年   2258篇
  2010年   1369篇
  2009年   1077篇
  2008年   1408篇
  2007年   1472篇
  2006年   1399篇
  2005年   1524篇
  2004年   901篇
  2003年   802篇
  2002年   746篇
  2001年   621篇
  2000年   615篇
  1999年   690篇
  1998年   521篇
  1997年   476篇
  1996年   396篇
  1995年   360篇
  1994年   289篇
  1993年   164篇
  1992年   226篇
  1991年   168篇
  1990年   149篇
  1989年   135篇
  1988年   153篇
  1987年   101篇
  1986年   96篇
  1985年   71篇
  1984年   41篇
  1983年   34篇
  1982年   28篇
  1981年   21篇
  1980年   10篇
  1979年   18篇
  1978年   5篇
  1975年   3篇
  1971年   5篇
  1969年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
AIM:To establish a mice model of hepatitis B by using HBV-transgenic mice, and to transfer HBV-specific cytotoxic T lymphoo/tes (CTL) induced from syngeneic BALB/c mice immunized by a eukaryotic expression vector containing HBV complete genome DNA.METHODS: HBV DNA was obtained from digested pBR3222HBV and ligated with the vector pcDNA3. Recombinant pcDNA3-HBV was identified by restriction endonuclease assay and transfected into human hepatoma cell line HepG2 with lipofectin. ELISA was used to detect the expression of HBsAg in culture supernatant, and RT-PCR to determine the existence of HBV PreS1 mRNA.BALB/c mice were immunized with pcDNA3-HBV or pcDNA3 by intramuscular injection.ELISA was used to detect the expression of HBsAb in serum. MTT assay was used to measure non-specific or specific proliferation ability and specific killing activity of spleen lymphocytes. Lymphocytes from immunized mice were transferred into HBV-transgenic mice (2.5×10^7 per mouse).Forty-eight hours later,the level of serum protein and transaminase was detected with biochemical method,liver and kidney were sectioned and stained by HE to observe the pathological changes.RESULTS: By enzyme digestion with Eco RI, Xho I and Hind Ⅲ,the recombinant pcDNA3-HBV was verified to contain a single copy of HBV genome,which was inserted in the positive direction.HepG2 cells transfected with the recombinant could stably express PreS1 mRNA and HBsAg.After immunized by pcDNA3-HBV for 4 weeks,HBsAb was detected in the serum of BALB/c mice. The potential of spleen lymphoo/tes for both non-specific and specific proliferation and the specific killing activity against target cells were enhanced. The transgenic mice in model group had no significant changes in the level of serum protein but had an obvious increase of ALT and AST. The liver had obvious pathological changes, while the kidney had no evident damage.CONCLUSION:A eukaryotic expression vector pcDNA3-HBV containing HBV complete genome is constructed successfully. HepG2 cells transfected with the recombinant can express PreS1 mRNA and HBsAg stably.Specific cellular immune response can be induced in mice immunized by pcDNA3-HBV.A mice model of acute hepatitis with HBV has been established.  相似文献   
993.
OBJECTIVES: The purpose of this study was to determine whether p38 mitogen-activated protein kinase (p38-MAPK) contributes to tumor necrosis factor-alpha (TNFalpha)-induced contractile depression. BACKGROUND: Tumor necrosis factor has both beneficial and detrimental consequences that may result from the activation of different downstream pathways. Tumor necrosis factor activates p38-MAPK, a stress-responsive kinase implicated in contractile depression and cardiac injury. METHODS: In isolated hearts from mice lacking the p38-MAPK activator, MAPK kinase 3 (MKK3), perfused at constant coronary pressure or flow, we measured the left ventricular developed pressure (LVDP) and the relationship between end-diastolic volume and LVDP in the presence and absence of 10 ng/ml TNFalpha. RESULTS: Within 15 min at constant pressure, TNFalpha significantly reduced LVDP and coronary flow in outbred and mkk3(+/+) mice. This early negative inotropic effect was associated with a marked phosphorylation of both p38-MAPK and its indirect substrate, HSP27. In hearts lacking MKK3, TNFalpha failed to activate p38-MAPK or to cause significant contractile dysfunction. The actions of TNFalpha were similarly attenuated in MAPK-activated protein kinase 2 (MK2)-deficient hearts, which have a marked reduction in myocardial p38-MAPK protein content, and by the p38-MAPK catalytic site inhibitor SB203580 (1 micromol/l). Under conditions of constant coronary flow, the p38-MAPK activation and contractile depression induced by TNFalpha, though attenuated, remained sensitive to the absence of MKK3 or the presence of SB203580. The role of p38-MAPK in TNFalpha-induced contractile depression was confirmed in isolated murine cardiac myocytes exposed to SB203580 or lacking MKK3. CONCLUSIONS: Tumor necrosis factor activates p38-MAPK in the intact heart and in isolated cardiac myocytes through MKK3. This activation likely contributes to the early cardiodepressant action of TNFalpha.  相似文献   
994.
Highly active antiretroviral therapy has decreased the morbidity and mortality of human immunodeficiency virus (HIV) infection, but latently infected cells remain for prolonged periods. CD4(+) CD45RO(+) T cells are a major latent virus reservoir in HIV-infected persons. Replication-competent, latently HIV-infected T cells can be generated in vitro by infecting peripheral blood mononuclear cells with HIV and then eliminating the HIV-producing cells with an anti-CD25 immunotoxin (IT). The CD25(-) latently infected cells then can be eliminated with an anti-CD45RO IT. This study determined whether this IT also could kill latently infected CD4 T cells from HIV-infected persons with or without detectable plasma viremia. The results show that ex vivo treatment of cells from HIV-positive persons by anti-CD45RO IT reduces the frequency of both productively and latently infected cells. In contrast, CD4(+) CD45RA(+) naive T cells and a proportion of CD4(+) CD45RO(lo) memory T cells are spared.  相似文献   
995.
BACKGROUND: Tuberculous meningitis (TBM) caused by Mycobacterium tuberculosis resistant to 1 or more antituberculosis drugs is an increasingly common clinical problem, although the impact on outcome is uncertain. METHODS: We performed a prospective study of 180 Vietnamese adults admitted consecutively for TBM. M. tuberculosis was cultured from the cerebrospinal fluid (CSF) of all patients and was tested for susceptibility to first-line antituberculosis drugs. Presenting clinical features, time to CSF bacterial clearance, clinical response to treatment, and 9-month morbidity and mortality were compared between adults infected with susceptible and those infected with drug-resistant organisms. RESULTS: Of 180 isolates, 72 (40.0%) were resistant to at least 1 antituberculosis drug, and 10 (5.6%) were resistant to at least isoniazid and rifampicin. Isoniazid and/or streptomycin resistance was associated with slower CSF bacterial clearance but not with any differences in clinical response or outcome. Combined isoniazid and rifampicin resistance was strongly predictive of death (relative risk of death, 11.63 [95% confidence interval, 5.21-26.32]) and was independently associated with human immunodeficiency virus infection. CONCLUSIONS: Isoniazid and/or streptomycin resistance probably has no detrimental effect on the outcome of TBM when patients are treated with first-line antituberculosis drugs, but combined isoniazid and rifampicin resistance is strongly predictive of death.  相似文献   
996.
Aberrant expression of receptor tyrosine kinase EphA1 in malignant tissues has been reported. However, the expression profile of EphA1 in renal cell carcinoma (RCC) and its association with clinicopathological parameters remain unknown. The aim of this study was to determine the cancerous value of the EphA1 protein expression in patients with renal cell carcinomas. This study included 144 patients with clear cell RCC (ccRCC), 18 patients with chromophobe RCC and 6 patients with papillary RCC. The EphA1 protein was detected in RCC tissue samples by an immunohistochemical staining with a specific polycolonal antibody. The correlation of the expression of the EphA1 protein with clinicopathological parameters was evaluated. High level of the expression of EphA1 was observed in all normal renal tubes. The EphA1 protein was negatively or weakly expressed in 93 out of 144 ccRCC (64.6%) and positively expressed in 51 out of 144 ccRCC (35.4%). The high level expression of the EphA1 protein was significantly associated with younger patients (P<0.001), sex (P=0.016) and lower nuclear grade (P<0.001). No significant relation between the expression of EphA1 and tumor diameter was found (P=0.316). Positive expression of EphA1 was observed in all samples of chromophobe RCC and papillary RCC. Our data indicated that the EphA1 protein may be a new marker for the prognosis of ccRCC.  相似文献   
997.
Objective: To study the correlation of β2-AR gene 5’-regulatory region SNPs and essential hypertension (EH) in Chinese Kazakh ethnic minority group. Methods: The Sequenom MassArray® SNP detection technology was used to detect β2-AR gene 5’-regulatory region SNPs in 150 Xinjiang Kazakh EH patients and 150 controls. Biochemical analyzer was used to detect lipid and other related biochemical parameters. SHEsis and other software were used to analyze linkage disequilibrium and haplotype. Results: Six loci rs205304 (-1023G/A), rs17108803 (-893T/G), rs12654778 (-654G/A), rs11168070 (-468C/G), rs11959427 (-367C/T) and rs2895795 (-1429T/A) polymorphisms of β2-AR gene 5’-regulatory region were found in the Xinjiang Kazakh populations. While, there was no significant difference between EH group and NH in genotypes and allele frequency of rs2053044, rs12654778, rs2895795, rs17108803 and rs11959427 (P>0.05). However; significant differences were detected of rs11168070 genotypes and allele frequency in two groups (P<0.05). Analysis of the linkage disequilibrium and haplotype in Kazakh population, there is a strong linkage disequilibrium of rs11168070, rs2053044, rs2895795 gene polymorphism in the EH group, and rs11168070, rs12654778, rs17108803 gene polymorphism in controls. Frequency of haplotype GTCCAT, GACTGT and ATGCGT in EH group was higher (P<0.05), while frequency of ATCTGT, ATGTGT, GTCCGT, GTCTAT, GACCAT and GTCTGT in the EH group was significantly lower than the control (P<0.05). Conclusions: β2-AR gene 5’-regulatory region of rs11168070, rs2053044, rs17108803, rs12654778, rs11959427 and rs2895795 genetic polymorphism exists in Kazakh. Among them, rs11168070 locus genotype and allele frequency distribution in the two groups are significant differences. In six polymorphic loci, there is a strong linkage disequilibrium, which haplotypes GTCCAT, GACTGT, ATGCGT are risk factors of EH, and the ATCTGT, ATGTGT, GTCCGT, GTCTAT, GACCAT, GTCTGT are protective factors.  相似文献   
998.
Hepatocellular carcinoma (HCC) is the most common primary liver tumor. Due to the asymptomatic nature of early HCC and lack of effective screening strategies, 80% of patients present with advanced HCC at the time of diagnosis. Novel molecular marker identification will be valuable for effective diagnosis and treatment. In this study we reported HCLS1-associated protein X-1 (HAX-1) is overexpression in HCC in human HCC sample. Furthermore, we provided evidence that HAX-1 expression positively correlated with that of Ki67 in patient sample. Statistic analysis indicated that HAX-1 expression level significantly correlated with clinic outcome of HCC. Cell based assay revealed that knockdown of HAX-1 inhibits cell proliferation. This result suggests that HAX-1 can be a novel molecular marker for HCC.  相似文献   
999.
Oral squamous cell carcinoma (OSCC) ranks as the fifth most common cancer worldwide with poor prognosis. Recently, tumor necrosis factor receptor-associated factor 4 (TRAF4) has attracted increasing attenuation due to its overexpression in certain cancers. However, its function and underlying mechanism in OSCC remains elusive. In this study, the high expression of TRAF4 mRNA and protein levels was noted in OSCC cell lines. Its overexpression with pcDNA3.1-TRAF4 vector transfection dramatically promoted cell proliferation and inhibited cell apoptosis, indicating a pivotal role of TRAF4 in OSCC cell growth. Simultaneously, TRAF4 elevation also increased cell invasion and migration. Mechanism analysis confirmed that TRAF4 up-regulation induced the expression of β-catenin and the downstream target molecules of cyclinD1, c-myc, Bcl-2, MMP-9 and MMP-2, indicating that TRAF4 could induce the activation of Wnt/β-catenin pathway. After pretreatment with β-catenin siRNA, the pathway was remarkably silenced. Simultaneously, cell growth, invasion and migration induced by TRAF4 were strikingly abrogated, suggesting that TRAF4 may promote OSCC cell growth, invasion and migration by Wnt/β-catenin pathway. Together, this study confirmed that TRAF4 acts as an oncogene for the development and progression of OSCC. Therefore, our study may support a promising therapeutic target for the treatment of OSCC.  相似文献   
1000.
We observed whether the effect of tumor-associated macrophages on gastric cancer stem cell in omental milky spots and lymph nodes micrometastasis and research its possible mechanism. Macrophage THP-1 cells and Human gastric adenocarcinoma SGC-7901 cells were collectively cultivated in vivo. We found macrophage could suppress the proliferation and accelerated cell death of MFC cell. Meanwhile, these effects may be concerned with many signaling pathways, and we detected MCP-1 and COX-2 miRNA expressions, PGE-2 release levels, IL-4 and IL-10 activities, and TGF-β, IFN-γ, VEGF, MMP-2 and MMP-9 protein expressions in collectively cultivated cell. We found that MCP-1 and COX-2 miRNA expressions, and PGE-2 release levels were suppressed, IL-4 activity was inhibited and IL-10 activity was activated in collectively cultivated cell. Meanwhile, TGF-β, MMP-2 and MMP-9 protein expressions were inhibited and IFN-γ and VEGF protein expressions were activated in collectively cultivated cell. Taken together, these results suggest that the effect of tumor-associated macrophages on gastric cancer stem cell in omental milky spots and lymph nodes micrometastasis via COX-2/PGE-2/TGF-β/VEGF signal pathways.  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