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   313篇
  免费   6篇
  国内免费   1篇
化学   283篇
晶体学   2篇
力学   2篇
数学   3篇
物理学   30篇
  2023年   2篇
  2021年   3篇
  2020年   3篇
  2019年   4篇
  2018年   5篇
  2017年   6篇
  2016年   2篇
  2015年   6篇
  2014年   10篇
  2013年   11篇
  2012年   14篇
  2011年   21篇
  2010年   8篇
  2009年   6篇
  2008年   20篇
  2007年   5篇
  2006年   17篇
  2005年   15篇
  2004年   7篇
  2003年   7篇
  2002年   12篇
  2001年   2篇
  2000年   3篇
  1996年   2篇
  1995年   1篇
  1994年   2篇
  1993年   3篇
  1990年   2篇
  1989年   1篇
  1986年   1篇
  1985年   4篇
  1984年   7篇
  1983年   4篇
  1982年   7篇
  1981年   4篇
  1980年   6篇
  1979年   7篇
  1978年   5篇
  1977年   9篇
  1976年   2篇
  1975年   8篇
  1974年   5篇
  1973年   5篇
  1972年   3篇
  1971年   3篇
  1970年   3篇
  1969年   5篇
  1968年   19篇
  1967年   7篇
  1966年   4篇
排序方式: 共有320条查询结果,搜索用时 375 毫秒
21.
Journal of Solid State Electrochemistry - The stable structures associated with the second charge of MgCo2−xMnxO4 (x = 0, 0.5), where Mg is removed from the stable first-discharge...  相似文献   
22.
23.
A fluoride-responsive (FR) amino acid that induces amide bond cleavage upon the addition of a fluoride was developed, and it was applied to an FR traceable linker. By the use of an alkyne-containing peptide as a model of an alkynylated target protein of a bioactive compound, introduction of the FR traceable linker onto the peptide was achieved. Subsequent fluoride-induced cleavage of the linker followed by labeling of the released peptide derivative was also conducted to examine the potential applicability of the FR traceable linker to the enrichment and labeling of alkynylated target molecules.  相似文献   
24.
Ferulic Acid (FA) is a highly abundant phenolic phytochemical which is present in plant tissues. FA has biological effects on physiological and pathological processes due to its anti-apoptotic and anti-oxidative properties, however, the detailed mechanism(s) of function is poorly understood. We have identified FA as a molecule that inhibits apoptosis induced by hydrogen peroxide (H2O2) or actinomycin D (ActD) in rat pheochromocytoma, PC12 cell. We also found that FA reduces H2O2-induced reactive oxygen species (ROS) production in PC12 cell, thereby acting as an anti-oxidant. Then, we analyzed FA-mediated signaling responses in rat pheochromocytoma, PC12 cells using antibody arrays for phosphokinase and apoptosis related proteins. This FA signaling pathway in PC12 cells includes inactivation of pro-apoptotic proteins, SMAC/Diablo and Bad. In addition, FA attenuates the cell injury by H2O2 through the inhibition of phosphorylation of the extracellular signal-regulated kinase (ERK). Importantly, we find that FA restores expression levels of brain-derived neurotrophic factor (BDNF), a key neuroprotective effector, in H2O2-treated PC12 cells. As a possible mechanism, FA increases BDNF by regulating microRNA-10b expression following H2O2 stimulation. Taken together, FA has broad biological effects as a neuroprotective modulator to regulate the expression of phosphokinases, apoptosis-related proteins and microRNAs against oxidative stress in PC12 cells.  相似文献   
25.
Root chemicals and DNA sequences were analyzed for Ligularia virgaurea collected in the northern Sichuan Province and adjacent areas of China. Thirty-eight samples were found to contain five chemotypes, two known and three new ones. From samples of the new chemotypes, 13 new compounds were isolated, including 3 sesquiterpene dimers and some rearranged eremophilanes. The DNA sequences suggested that the chemotype differentiation had a genetic origin.  相似文献   
26.
Ueda  Chiaki  Okita  Atsushi  Tanaka  Go  Suetake  Noriaki  Uchino  Eiji 《Optical Review》2017,24(3):442-447
Optical Review - A novel color removal method for digital color images is proposed. In this method, differences of colors in an input color image are reflected effectively, and the perceived...  相似文献   
27.
Polymers having thioether, thiolester, and amide linkages in each repeating unit of a polymer main chain were prepared by the polyaddition reaction of pseudoxazolones (2-isopropylidene-4-alkyl-3-oxazolin-5-ones) and dimercaptans. The polymers had inherent viscosities in a range of 0.08–0.22 and gave transparent films by solution casting.  相似文献   
28.
PVTx relationships of the m-xylene-p-xylene system have been measured with a glass piezometer at 283.15 and 298.15 K and pressures up to 200 MPa, or up to the point of solidification of m-xylene where this occurred at a lower pressure. Freezing pressures of m-xylene were observed as a discontinuity in the volume at increasing pressure. Approximate solid-liquid equilibria under high pressures were obtained from the freezing pressure measurement. The Carnahan-Starling-van der Waals (CS-vdW) equation of state was used to correlate the PVTx data. The solid-liquid equilibria under high pressures were calculated with the CS-vdW equation of state for the liquid phase and a simple equation of state for the solid phase. In order to test the validity of the calculation method, the solid-liquid equilibrium relationships of the benzene-cyclohexane system were also calculated. It was found that the solid molar volume should be treated as a function of temperature and/or pressure to fit the experimental data.  相似文献   
29.
Effect of mixing and processing conditions at T‐die extrusion on the structure and mechanical properties is studied for isotactic polypropylene (PP) containing a small amount of β‐form nucleating agent, N,N′‐dicyclohexyl‐2,6‐naphthalenedicarboxamide. It is found that trigonal β crystals are predominantly formed in the extruded samples containing the nucleating agent irrespective of the mixing and processing conditions, leading to the marked mechanical toughness. On the contrary, the molecular orientation is significantly affected by the mixing and processing conditions. In particular, it should be noted that PP molecules in the extruded sheet which was mixed at high temperature (260 °C) and extruded at low temperature (200 °C) orient perpendicular to the applied flow direction. As a result, the sheet shows anomalous mechanical anisotropy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 424–433, 2009  相似文献   
30.
Recently, measuring the complexity of body movements during sleep has been proven as an objective biomarker of various psychiatric disorders. Although sleep problems are common in children with autism spectrum disorder (ASD) and might exacerbate ASD symptoms, their objectivity as a biomarker remains to be established. Therefore, details of body movement complexity during sleep as estimated by actigraphy were investigated in typically developing (TD) children and in children with ASD. Several complexity analyses were applied to raw and thresholded data of actigraphy from 17 TD children and 17 children with ASD. Determinism, irregularity and unpredictability, and long-range temporal correlation were examined respectively using the false nearest neighbor (FNN) algorithm, information-theoretic analyses, and detrended fluctuation analysis (DFA). Although the FNN algorithm did not reveal determinism in body movements, surrogate analyses identified the influence of nonlinear processes on the irregularity and long-range temporal correlation of body movements. Additionally, the irregularity and unpredictability of body movements measured by expanded sample entropy were significantly lower in ASD than in TD children up to two hours after sleep onset and at approximately six hours after sleep onset. This difference was found especially for the high-irregularity period. Through this study, we characterized details of the complexity of body movements during sleep and demonstrated the group difference of body movement complexity across TD children and children with ASD. Complexity analyses of body movements during sleep have provided valuable insights into sleep profiles. Body movement complexity might be useful as a biomarker for ASD.  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