全文获取类型
收费全文 | 1549篇 |
免费 | 60篇 |
国内免费 | 88篇 |
专业分类
系统科学 | 7篇 |
丛书文集 | 42篇 |
教育与普及 | 8篇 |
理论与方法论 | 2篇 |
现状及发展 | 49篇 |
综合类 | 1589篇 |
出版年
2024年 | 3篇 |
2023年 | 9篇 |
2022年 | 19篇 |
2021年 | 20篇 |
2020年 | 28篇 |
2019年 | 27篇 |
2018年 | 16篇 |
2017年 | 29篇 |
2016年 | 36篇 |
2015年 | 46篇 |
2014年 | 56篇 |
2013年 | 51篇 |
2012年 | 81篇 |
2011年 | 72篇 |
2010年 | 48篇 |
2009年 | 60篇 |
2008年 | 54篇 |
2007年 | 101篇 |
2006年 | 92篇 |
2005年 | 65篇 |
2004年 | 73篇 |
2003年 | 87篇 |
2002年 | 66篇 |
2001年 | 53篇 |
2000年 | 50篇 |
1999年 | 52篇 |
1998年 | 53篇 |
1997年 | 53篇 |
1996年 | 43篇 |
1995年 | 36篇 |
1994年 | 47篇 |
1993年 | 32篇 |
1992年 | 27篇 |
1991年 | 30篇 |
1990年 | 20篇 |
1989年 | 20篇 |
1988年 | 13篇 |
1987年 | 13篇 |
1986年 | 7篇 |
1985年 | 9篇 |
排序方式: 共有1697条查询结果,搜索用时 31 毫秒
941.
Regulation of mitochondrial oxidative phosphorylation by second messenger-mediated signal transduction mechanisms 总被引:2,自引:0,他引:2
Boneh A 《Cellular and molecular life sciences : CMLS》2006,63(11):1236-1248
The mitochondrial oxidative phosphorylation system is responsible for providing the bulk of cellular ATP molecules. There
is a growing body of information regarding the regulation of this process by a number of second messenger-mediated signal
transduction mechanisms, although direct studies aimed at elucidating this regulation are limited. The main second messengers
affecting mitochondrial signal transduction are cAMP and calcium. Other second messengers include ceramide and reactive oxygen
species as well as nitric oxide and reactive nitrogen species. This review focuses on available data on the regulation of
the mitochondrial oxidative phosphorylation system by signal transduction mechanisms and is organised according to the second
messengers involved, because of their pivotal role in mitochondrial function. Future perspectives for further investigations
regarding these mechanisms in the regulation of the oxidative phosphorylation system are formulated.
Received 11 December 2005; received after revision 14 January 2006; accepted 6 February 2006 相似文献
942.
Selenocystine (SeC), a naturally occurring selenoamino acid, has been shown to be a novel compound with broad-spectrum anticancer activity. In this study, we showed that SeC triggered time- and dose-dependent apoptosis in A375 human melanoma cells by activating the mitochondria-mediated and death receptor-mediated apoptosis pathways. Pretreatment of cells with a general caspase inhibitor z-VAD-fmk significantly prevented SeC-induced apoptosis. A375 cells exposed to SeC showed an increase in levels of total p53 and phosphorylated p53 (serine-15). Silencing of p53 expression with RNA interference significantly suppressed SeC-induced p53 phosphorylation, caspase activation and apoptotic cell death. Moreover, generation of reactive oxygen species and subsequent induction of DNA strand breaks were found to be upstream mediators of p53 activation induced by SeC. In a nude mice xenograft experiment, SeC significantly inhibited the tumor growth of A375 cells via induction of apoptosis. Taken together, these results suggest the potential applications of SeC in cancer chemoprevention. 相似文献
943.
The family of iron responsive RNA structures regulated by changes in cellular iron and oxygen 总被引:1,自引:1,他引:0
The life of aerobes is dependent on iron and oxygen for efficient bioenergetics. Due to potential risks associated with iron/oxygen
chemistry, iron acquisition, concentration, storage, utilization, and efflux are tightly regulated in the cell. A central
role in regulating iron/oxygen chemistry in animals is played by mRNA translation or turnover via the iron responsive element
(IRE)/iron regulatory protein (IRP) system. The IRE family is composed of three-dimensional RNA structures located in 3′ or
5′ untranslated regions of mRNA. To date, there are 11 different IRE mRNAs in the family, regulated through translation initiation
or mRNA stability. Iron or oxidant stimuli induce a set of graded responses related to mRNA-specific IRE substructures, indicated
by differential responses to iron in vivo and binding IRPs in vitro. Molecular effects of phosphorylation, iron and oxygen remain to be added to the structural information of the IRE-RNA and
IRP repressor in the regulatory complex.
Received 21 April 2007; received after revision 13 July 2007; accepted 2 August 2007 相似文献
944.
Kang SW 《Cellular and molecular life sciences : CMLS》2007,64(5):533-541
The tyrosine phosphorylation cascade is a hallmark of platelet-derived growth factor (PDGF)- induced signal transduction.
The amplitude and propagation of the tyrosine phosphorylation signal relies on the balance between tyrosine kinase and tyrosine
phosphatase. The tyrosine kinase is latent in the absence of stimulation, whereas the tyrosine phosphatase is highly and constitutively
active. Therefore, the kinase activation should be accompanied by temporal and spatial inactivation of tyrosine phosphatase
to achieve the robust amplification of tyrosine phosphorylation. For the past decade, reactive oxygen species have been receiving
a great deal of attention with regard to their ability to shut down tyrosine phosphatase activities in a reversible manner.
In this article, the crosstalk between tyrosine phosphorylation and reactive oxygen species in PDGF signaling is discussed.
Received 2 October 2006; received after revision 13 November 2006; accepted 27 November 2006 相似文献
945.
946.
目的:观察刺果紫玉盘素J(Calamistrin J,Cal-J)诱导人结肠癌Lovo细胞凋亡的作用,并探讨其诱导细胞凋亡的可能机制.方法:Hoechst33258染色后在荧光显微镜下观察凋亡细胞的形态变化,流式细胞仪(FCM)分析细胞DNA含量变化及计算凋亡率.荧光酶标仪检测DCFH-DA荧光探针标记的活性氧(ROS),以DiOC6(3)标记、流式细胞仪测定细胞线粒体膜电位(△ψm)的改变.结果:Cal-J作用48 h后,荧光显微镜下可见细胞核固缩,染色质凝聚等典型凋亡形态学特征.FCM检测可见Lovo细胞凋亡率明显增加,且具有时间、剂量的双重依赖性.Cal-J处理Lovo细胞12 h后,可剂量依赖性地增高胞内ROS水平,Cal-J 100 μg·mL-1作用于Lovo细胞,可时间依赖性降低△ψm.结论:Cal-J具有诱导Lovo细胞凋亡的作用,该作用呈一定的剂量和时间依赖性,其机制与提高细胞内ROS水平和降低线粒体膜电位有关. 相似文献
947.
在脉冲激光沉积(pulsed laser deposition,PLD)法生长氧化物纳米材料的过程中,环境中的氧气对氧化物纳米结构的形成起着至关重要的作用。在溅射了Au纳米层的Si(111)衬底上,采用PLD法在不同氧分压下制备了Mn-Co-Ni-O纳米结构,并用X射线衍射仪(X-ray diffractometer,XRD)和场发射扫描电子显微镜(scanning electron microscope,SEM)表征了Mn-Co-Ni-O的结构特性和表面形貌。研究发现生长温度为750 ℃的Mn-Co-Ni-O微观结构与氧分压密切相关。在较低的氧分压环境下(1 Pa和5 Pa),Si衬底上生长的Mn-Co-Ni-O纳米锥结构是由Au催化的气–液–固(vapor-liquid-solid,VLS)生长机制控制。当氧分压增加到15 Pa,Mn-Co-Ni-O纳米结构的形态从纳米锥向纳米线转变,该过程是由VLS和气–固(vapor-solid,VS)生长机制共同作用。深入研究Mn-Co-Ni-O纳米结构的生长机制为获得更多的纳米线提供了理论基础。 相似文献
948.
煤炭是世界上储量最为丰富的化石燃料之一,是制造多孔碳、纳米碳、碳质复合材料和石墨烯的主要原料。燃料电池是一种通过化学反应将化学燃料直接转化为电能的装置,它不受卡诺循环限制,具有高效率、高功率密度和环境友好等特点,有着巨大的应用前景。但其阴极氧还原反应(cathodic oxygen reduction reaction, ORR)动力学非常缓慢,需要在催化剂的作用下加速其反应。现有的催化剂主要是贵金属Pt,但Pt资源储量少、成本高、稳定性差,限制了燃料电池的商业化应用。近年来的研究表明,碳基材料是最有希望替代Pt的催化剂材料。基于此,对近年来煤基多孔碳的制备方法进行了综述,并在此基础上阐述了以煤基活性炭为基体的燃料电池用氧还原电催化剂的研究进展。 相似文献
949.
对吉林省部分河流在不同时间采样, 测其化学需氧量(COD)和总有机碳(TOC), 用最小二乘法对二者进行线性回归, 并进行相关关系的显著性检验, 建立吉林省部分河流COD和TOC的定量关系模型. 结果表明, 水体中COD与TOC具有良好的线性相关关系. 相似文献
950.
在铁矿石烧结过程中进行富氧,观察富氧后烧结固体燃料消耗、成品率、利用系数、冶金性能及矿相显微结构等指标的变化情况.试验表明:富氧时间为2~4 min、富氧量为5~8 m3/t时,烧结矿的各项指标较好.在该条件下,与基准烧结矿相比,成品率提高2.12%、转鼓强度值提高0.92%、固体燃料消耗降低1.56 kg/t;富氧烧结对改善烧结矿成品率的试验结果表明:16组烧结试验中,对烧结过程进行富氧后,成品率提高了0.79%~2.05%,富氧后的成品率平均高于基准成品率1.35%.随着富氧量的增加,成品率呈现出增长趋势;而随着富氧时间的增加,成品率没有明显增长.同时,富氧烧结后,烧结固体燃料消耗下降0.69~1.41 kg/t. 相似文献