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   225篇
  免费   15篇
  240篇
  2024年   1篇
  2023年   5篇
  2022年   17篇
  2021年   12篇
  2020年   17篇
  2019年   27篇
  2018年   21篇
  2017年   13篇
  2016年   7篇
  2015年   11篇
  2014年   17篇
  2013年   27篇
  2012年   10篇
  2011年   12篇
  2010年   6篇
  2009年   3篇
  2008年   7篇
  2007年   3篇
  2006年   3篇
  2004年   1篇
  2003年   2篇
  2002年   4篇
  2000年   2篇
  1998年   1篇
  1994年   1篇
  1988年   1篇
  1984年   2篇
  1983年   2篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1975年   1篇
  1970年   1篇
排序方式: 共有240条查询结果,搜索用时 15 毫秒
1.
The flavonoids of five Geranium, fourteen Erodium and four Monsonia species were studied. Quercetin was the most common aglycone with lesse  相似文献   
2.
Mechanical stresses directly regulate the function of several proteins of the integrin-mediated focal adhesion complex as they experience intra- and extracellular forces. Kindlin is a largely overlooked member of the focal adhesion complex whose roles in cellular mechanotransduction are only recently being identified. Recent crystallographic experiments have revealed that kindlins can form dimers that bind simultaneously to two integrins, providing a mechanistic explanation of how kindlins may promote integrin activation and clustering. In this study, using the newly identified molecular structure, we modeled the response of the kindlin2 dimer in complex with integrin β1 to mechanical cytoskeletal forces on integrins. Using molecular dynamics simulations, we show that forces on integrins are directly transmitted to the kindlin2 dimerization site, resulting in a shift in an R577-S550/E553 interaction network at this site. Under force, R577 on one protomer switches from interacting with S550 to forming new hydrogen bonds with E553 on the neighboring protomer, resulting in the strengthening of the kindlin2 dimer in complex with integrin β1. This force-induced strengthening is similar to the catch-bond mechanisms that have previously been observed in other adhesion molecules. Based on our results, we propose that the kindlin2 dimer is mechanosensitive and can strengthen integrin-mediated focal adhesions under force by shifting the interactions at its dimerization sites.  相似文献   
3.
The peroxisomal proliferator-activated receptor γ (PPARγ) is a nuclear receptor that controls inflammation and immunity. Innate immune defense against bacterial infection appears to be compromised by PPARγ. The relevance of PPARγ in myeloid cells, that organize anti-bacterial immunity, for the outcome of immune responses against intracellular bacteria such as Listeria monocytogenes in vivo is unknown. We found that Listeria monocytogenes infection of macrophages rapidly led to increased expression of PPARγ. This prompted us to investigate whether PPARγ in myeloid cells influences innate immunity against Listeria monocytogenes infection by using transgenic mice with myeloid-cell specific ablation of PPARγ (LysMCre×PPARγ(flox/flox)). Loss of PPARγ in myeloid cells results in enhanced innate immune defense against Listeria monocytogenes infection both, in vitro and in vivo. This increased resistance against infection was characterized by augmented levels of bactericidal factors and inflammatory cytokines: ROS, NO, IFNγ TNF IL-6 and IL-12. Moreover, myeloid cell-specific loss of PPARγ enhanced chemokine and adhesion molecule expression leading to improved recruitment of inflammatory Ly6C(hi) monocytes to sites of infection. Importantly, increased resistance against Listeria infection in the absence of PPARγ was not accompanied by enhanced immunopathology. Our results elucidate a yet unknown regulatory network in myeloid cells that is governed by PPARγ and restrains both listeriocidal activity and recruitment of inflammatory monocytes during Listeria infection, which may contribute to bacterial immune escape. Pharmacological interference with PPARγ activity in myeloid cells might represent a novel strategy to overcome intracellular bacterial infection.  相似文献   
4.
The temperature‐dependent aggregation behavior of PffBT4T polymers used in organic solar cells plays a critical role in the formation of a favorable morphology in fullerene‐based devices. However, there is little investigation into the impact of donor/acceptor ratio on morphology tuning, especially for nonfullerene acceptors (NFAs). Herein, the influence of composition on morphology is reported for blends of PffBT4T‐2DT with two NFAs, O‐IDTBR and O‐IDFBR. The monotectic phase behavior inferred from differential scanning calorimetry provides qualitative insight into the interplay between solid–liquid and liquid–liquid demixing. Transient absorption spectroscopy suggests that geminate recombination dominates charge decay and that the decay rate is insensitive to composition, corroborated by negligible changes in open‐circuit voltage. Exciton lifetimes are also insensitive to composition, which is attributed to the signal being dominated by acceptor excitons which are formed and decay in domains of similar size and purity irrespective of composition. A hierarchical morphology is observed, where the composition dependence of size scales and scattering intensity from resonant soft X‐ray scattering (R‐SoXS) is dominated by variations in volume fractions of polymer/polymer‐rich domains. Results suggest an optimal morphology where polymer crystallite size and connectivity are balanced, ensuring a high probability of hole extraction via such domains.  相似文献   
5.
Molecular Biology Reports - Both extreme usage of water in agriculture i.e., drought and flooding affect physiological and growth aspects of the plant as well as gene expression undertaken in water...  相似文献   
6.
The properties of Trematosphaeria mangrovei laccase enzyme purified on Sephadex G-100 column were investigated. SDS–PAGE of the purified laccase enzyme showed a single band at 48 kDa. The pure laccase reached its maximal activity at temperature 65 °C, pH 4.0 with Km equal 1.4 mM and Vmax equal 184.84 U/mg protein. The substrate specificity of the purified laccase was greatly influenced by the nature and position of the substituted groups in the phenolic ring. The pure laccase was tested with some metal ions and inhibitors, FeSO4 completely inhibited laccase enzyme and also highly affected by (NaN3) at a concentration of 1 mM. Amino acid composition of the pure enzyme was also determined. Carbohydrate content of purified laccase enzyme was 23% of the enzyme sample. The UV absorption spectra of the purified laccase enzyme showed a single peak at 260–280 nm.  相似文献   
7.
Molecular Biology Reports - Gastric cancer is one of the common types of cancer around the world which has few therapeutic options. Nitrogen heterocyclic derivatives such as thiazoles are used as...  相似文献   
8.
Plant Molecular Biology Reporter - The original version of this article unfortunately contained some mistakes in article Title and Table 1.  相似文献   
9.
Graft versus host disease (GVHD) is a major complication of bone marrow transplantation (BMT). Numerous studies have shown the potential role of cytokine genotypes in the occurrence of GVHD. In this retrospective, case–control study we aimed to investigate the association between 13 cytokine genes and acute GVHD (aGVHD) after HLA-identical sibling BMT in 91 Iranian subjects. Negative association was found between aGVHD and donor IL-10/GCC haplotype or donor IL-4Ra-A allele in the population study. When compared within the leukemia subgroup, we observed positive association between recipient IL-1α ?889/C allele and aGVHD. Also there were negative association between recipient IL-10/CAA haplotype and donor IL-4Ra/A allele and development of aGVHD. Among the different genotypes only donor IL-4Ra and donor IL-12 showed significant association. We conclude that several cytokine polymorphisms are positively and negatively associated with aGVHD in Iranian HLA matched siblings, of which IL-4Ra and IL-12 may play important roles.  相似文献   
10.
The phytochemical analysis of the ethanolic extract of branches of Cotoneaster horizontalis, Decne revealed the presence of: β-carotene, ascorbic acid and less amounts of α-tocopherol and amygdalin (vitamin B17) in proportions of: 2,500, 70, 0.093, 0.334 mg 100 g?1, respectively. Acute oral toxicity test revealed its safety profile. In vitro study revealed its good 2, 2-diphenyl-1-picrylhydrazyl radical scavenging and anticancer activities. Invivo study, simultaneous administration of this extract at a dose of 100 or 200 mg kg?1 body weight for 4 weeks, exhibited a significant protection in a dose-dependant manner against hepatotoxicity induced by repeated dose of acetaminophen (1 g kg?1 body weight day?1, p.o.) by preserving the liver function parameters, hepatic redox state and serum lipid profile near the healthy levels. Consequently, in vitro culture was carried out on full or half strength of Murashige and Skoog medium supplemented with different concentrations of benzyl amino purine or kinetin provided shootlets production; different concentrations of 2,4-dichlorophenoxy acetic acid and naphthalene acetic acid showed an increase of callus. Determination of α-tocopherol and amygdalin in different shootlets and callus extracts showed a pronounced increases up to 30.62 and 3.69 mg 100 g?1 in shootlet extract, respectively as well as 26.61 and 12.71 mg 100 g?1 in callus extract, respectively, as compared with those of the mother plant (0.76 and 0.11 mg 100 g?1 extract, respectively).  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