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   11483篇
  免费   774篇
  国内免费   4篇
  2024年   9篇
  2023年   30篇
  2022年   35篇
  2021年   229篇
  2020年   146篇
  2019年   176篇
  2018年   265篇
  2017年   235篇
  2016年   376篇
  2015年   633篇
  2014年   666篇
  2013年   785篇
  2012年   1016篇
  2011年   941篇
  2010年   624篇
  2009年   556篇
  2008年   732篇
  2007年   709篇
  2006年   649篇
  2005年   549篇
  2004年   547篇
  2003年   456篇
  2002年   394篇
  2001年   274篇
  2000年   255篇
  1999年   183篇
  1998年   84篇
  1997年   71篇
  1996年   46篇
  1995年   48篇
  1994年   28篇
  1993年   26篇
  1992年   45篇
  1991年   48篇
  1990年   41篇
  1989年   49篇
  1988年   38篇
  1987年   26篇
  1986年   26篇
  1985年   31篇
  1984年   20篇
  1983年   18篇
  1981年   9篇
  1979年   12篇
  1978年   13篇
  1977年   10篇
  1974年   13篇
  1973年   15篇
  1972年   11篇
  1971年   8篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
951.
A peroxisome proliferator-activated receptor gamma (PPARgamma) ligand, 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)), has been reported to possess anti-inflammatory activity in activated monocytes/macrophages. In this study, we investigated the effect of 15d-PGJ(2) on the lipopolysaccharide (LPS)-induced expression of chemokine mRNAs, especially macrophage inhibitory protein (MIP)-2 (CXCL2), in mouse peritoneal macrophages. The inhibitory actions of the natural PPARgamma ligands, 15d-PGJ(2) and prostaglandin A1 (PGA1), on the expression of RANTES (regulated upon activation, normal T expressed and secreted; CCL5), MIP-1beta (CCL4), MIP-1alpha (CCL3), IFN-gamma-inducible protein 10 kilodaltons (IP-10; CXCL10) and monocyte chemoattractant protein-1 (MCP-1; CCL2) mRNA in LPS-treated cells were stronger than those of the synthetic PPARgamma ligands troglitazone and ciglitazone. However, 15d-PGJ(2) enhanced the expression of LPS-induced MIP-2 (CXCL2) mRNA. A specific PPARgamma antagonist (GW9662) had no effect on the inhibitory action of 15d-PGJ(2) and PGA1 in LPS-induced chemokine mRNA expression and on the synergistic action of 15d-PGJ(2) in LPS-induced MIP-2 (CXCL2) expression. Moreover, LPS itself reduced the expression of PPARgamma. Although the synergistic effect of 15d-PGJ(2) on LPS-induced MIP-2 (CXCL2) mRNA expression was remarkable, the production of MIP-2 (CXCL2) in cells treated with 15d-PGJ(2) and LPS did not increase compared to the production in cells treated with LPS alone. The synergistic action of 15d-PGJ(2) on LPS-induced MIP-2 (CXCL2) mRNA expression was dependent on the activation of nuclear factor-kappaB (NF-kappaB), and 15d-PGJ(2) increased the phosphorylation of p38 and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) in cells stimulated with LPS. These results suggest that the synergistic effect of 15d-PGJ(2) on LPS-induced MIP-2 (CXCL2) expression is PPARgamma-independent, and is mediated by the p38 and SAPK/JNK pathway in mitogen-activated protein kinase signaling pathways, which activates NF-kappaB. Our data may give more insights into the different mechanisms contrary to the anti-inflammatory effect of 15d-PGJ(2) on the expression of chemokine genes.  相似文献   
952.
953.
954.
Beta-glucan was recently shown to have the ability to enhance and stimulate the immune system in humans, but little is known about its the anti-inflammatory effects. We investigated the effect of beta-glucan on the production of tumor necrosis factor-alpha (TNF-alpha), a major pro-inflammatory mediator, in lipopolysaccharide (LPS)-stimulated BV2 microglial cells. beta-Glucan decreased the production and expression of TNF-alpha. In addition, it blocked LPS-stimulated activation of nuclear factor kappa B (NF-kappaB). Hence beta-glucan might suppress LPS-stimulated TNF-alpha production by inhibiting NF-kappaB in BV2 microglial cells.  相似文献   
955.
Microalgal growth was enhanced by the addition of levoglucosan to the culture medium. The growth-enhancing compound levoglucosan was isolated from the green seaweed Monostroma nitidum using water extraction, molecular fractionation, DEAE-cellulose column chromatography, and high-performance liquid chromatography. Yield of the compound from seaweed powder was 5 × 10−3% (w/w). At 10 mM concentration, levoglucosan enhanced cell growth and the specific growth rate of all feed microalgal species tested (Chaetoceros gracilis, Chlorella ellipsoidea, Dunaliella salina, Isochrysis galbana, Nannochloris oculata, Navicula incerta, Pavlova lutheri, Tetraselmis suecica) in most culture media by approximately 150%. Cellular fatty acid profiles and cell size differed marginally between cultures with and without levoglucosan.  相似文献   
956.
CIA07 is an immunostimulatory agent composed of bacterial DNA fragments and modified lipopolysaccharide, which has antitumor activity against bladder cancer in mice. In this study, the adjuvant activity of CIA07 was evaluated using hepatitis B virus surface antigen (HBsAg) as the immunogen. Mice were immunized intramuscularly three times at 1-week intervals with HBsAg alone or in combination with alum, bacterial DNA fragments, modified lipopolysaccharide, CIA07 or CpG1826, and immune responses were assessed. At 1 week after the final injection, the HBsAg-specific total serum IgG antibody titer in CIA07-treated mice was 14 times higher than that in animals administered antigen alone, six times higher than in mice given alum or bacterial DNA fragments and twice as high as those treated with modified lipopolysaccharide or CpG1826, and remained maximal until 8 weeks postimmunization. Animals receiving antigen alone or plus alum displayed barely detectable HBsAg-specific serum IgG2a antibody responses. However, coadministration of CIA07 with antigen led to markedly enhanced serum IgG2a antibody titer and IFN-gamma(+) production in splenocytes, indicating that CIA07 effectively induces Th1-type immune responses. In addition, the number of HBsAg-specific CD8(+) T cells in peripheral blood mononuclear cells was elevated in CIA07-treated mice. These data clearly demonstrate that CIA07 is able to induce both cellular and humoral immune responses to HBsAg, and confirm its potential as an adjuvant in therapeutic vaccines for hepatitis B virus infections.  相似文献   
957.
Genetic human papillomavirus type 16 L1 (HPV16 L1) has been widely studied for cervical cancer vaccine development. For the enzyme-linked immunosorbent assay (ELISA) screening of these vaccines, HPV16 L1 protein, which is required as a coating protein, has previously been expressed from costly and laborious recombinant baculovirus-infected insect cells. For a novel HPV16 L1 expression system characterized by a high yield of soluble form with simple purification steps, we have cloned and expressed two different types of HPV16 L1, both fused to maltose binding protein (MBP) or glutathione-S-transferase (GST) in Escherichia coli. The yield of soluble HPV16 L1 was influenced by the cultivation temperature. The yield of soluble form in the total MBP-fused HPV16 L1 protein (MBP-HPV16 L1) was 35% at 37 degrees C, but increased to 85% at 22 degrees C. Among the fusion partners, MBP provided higher yields of total and soluble HPV16 L1 than did GST. MBP-HPV16 L1 showed a 4.9-fold higher yield of the soluble form over insoluble inclusion bodies under optimized culture conditions. The soluble form of MBP-HPV16 L1 was purified via MBP affinity chromatography in a recovery yield of 9.7%. After fusion with MBP, HPV16 L1 showed binding activity to HPV16 L1-specific monoclonal antibody comparable to HPV16 L1 from the insect cells in ELISA tests. These results demonstrate that the use of MBP as a fusion partner may generate a high yield of soluble HPV16 L1 under optimized temperature conditions, and that MBP-fused HPV16 L1 might be applied further in evaluations of the immune responses of HPV16 L1-based cervical cancer vaccines.  相似文献   
958.
Kang YH  Lee KA  Yang Y  Kim SH  Kim JH  Park SN  Paik SG  Yoon DY 《Amino acids》2007,33(1):105-112
Summary. Cervical cancer is one of the leading causes of female cancer death worldwide with about 500,000 deaths per year. Both mitomycin C and cisplatin are alkylating agents, which bind and intercalate DNA, and thus used as anti-cancer drugs. In these studies, we focused on investigating the apoptotic effects of intercalating agents on HPV-negative cervical cancer C-33A cells. Accordingly, C-33A cells were treated with carboplatin, mitomycin C or cisplatin. Cell cycle analysis revealed that treatment with mitomycin C and cisplatin but not with carboplatin resulted in apoptosis. Both mitomycin C and cisplatin induced apoptosis in C-33A cells via caspase-8 and -3 processing in a Fas/FasL-dependent manner and also suppressed IL-18 expression, while they down-regulated IκB expression and up-regulated p65 expression. These results suggest that both mitomycin C and cisplatin induce apoptosis, not only via the caspase-8 and -3 dependent Fas/FasL pathway, but also via the regulation of NF-κB activity and IL-18 expression in HPV-negative cervical cancer C-33A cells.  相似文献   
959.
Green tea is a popular worldwide beverage, and its potential beneficial effects such as anti-cancer and anti-oxidant properties are believed to be mediated by epigallocatechin-3-gallate (EGCG), a major constituent of polyphenols. Recently, it was reported that EGCG might be useful in the prevention or treatment of androgenetic alopecia by selectively inhibiting 5alpha-reductase activity. However, no report has been issued to date on the effect of EGCG on human hair growth. This study was undertaken to measure the effect of EGCG on hair growth in vitro and to investigate its effect on human dermal papilla cells (DPCs) in vivo and in vitro. EGCG promoted hair growth in hair follicles ex vivo culture and the proliferation of cultured DPCs. The growth stimulation of DPCs by EGCG in vitro may be mediated through the upregulations of phosphorylated Erk and Akt and by an increase in the ratio of Bcl-2/Bax ratio. Similar results were also obtained in in vivo dermal papillae of human scalps. Thus, we suggest that EGCG stimulates human hair growth through these dual proliferative and anti-apoptotic effects on DPCs.  相似文献   
960.
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