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   87篇
  免费   3篇
  国内免费   17篇
化学   58篇
晶体学   5篇
力学   5篇
综合类   2篇
数学   10篇
物理学   27篇
  2022年   4篇
  2021年   1篇
  2020年   4篇
  2019年   4篇
  2015年   3篇
  2014年   1篇
  2013年   3篇
  2012年   12篇
  2011年   2篇
  2010年   2篇
  2009年   7篇
  2008年   2篇
  2007年   4篇
  2006年   5篇
  2005年   5篇
  2004年   6篇
  2003年   3篇
  2002年   2篇
  2001年   2篇
  2000年   3篇
  1999年   2篇
  1998年   5篇
  1997年   2篇
  1996年   3篇
  1995年   4篇
  1994年   3篇
  1993年   3篇
  1992年   5篇
  1991年   3篇
  1989年   1篇
  1988年   1篇
排序方式: 共有107条查询结果,搜索用时 46 毫秒
41.
合成了1-羟基-2-(1H)-吡啶硫酮及其甲基衍生物[AuL2]OH型配合物(L=PT^-,3-CH3-PT^-T 4-CH3-PT^-)。用元素,紫外光谱,外红光谱,^1HNMR谱,摩尔电导,TGDTA-DTG进行了表征,用循环伏安法研究其氧化还原性质,含甲基的配合物有较强的抑菌活性  相似文献   
42.
Theory and characteristics of the surface acoustic wave (SAW)/impedance sensor system in electrolyte solution are reported. This kind of sensor was constructed by a 62-MHz SAW resonator and a pair of conductive electrodes in series. By using the circuit network analysis theory, two oscillation equations were derived and used to explain the frequency-shift response to solution conductance. Results showed that the sensor possesses high sensitivity to the solution conductivity and can be applied to conductivity measurements in solution. Its sensitivity and accuracy could be improved in the presence of a large amount of unreacting foreign electrolytes. The sensor was successfully applied to four types of titration (acid-base, precipitation, oxidation-reduction and compleximetric titration) by monitoring the frequency-shift response. Factors influencing the frequencimetric titration curve were also investigated. Analytes at levels down to 1 × 10−5 M could be determined by the proposed titration technique. The total acidity in several food samples was determined and the results were consistent with those obtained by conventional methods.  相似文献   
43.
Four water-soluble β-CD-pentacyclic triterpene conjugates were synthesized via ester and amide linkages. All the conjugates showed lower hydrophobicity (AlogP) than their parent.  相似文献   
44.
Blood oxygenation level-dependent (BOLD) contrast-based functional magnetic resonance imaging (fMRI) has been widely utilized to detect brain neural activities and great efforts are now stressed on the hemodynamic processes of different brain regions activated by a stimulus. The focus of this paper is the comparison of Gamma and Gaussian dynamic convolution models of the fMRI BOLD response. The convolutions are between the perfusion function of the neural response to a stimulus and a Gaussian or Gamma function. The parameters of the two models are estimated by a nonlinear least-squares optimal algorithm for the fMRI data of eight subjects collected in a visual stimulus experiment. The results show that the Gaussian model is better than the Gamma model in fitting the data. The model parameters are different in the left and right occipital regions, which indicate that the dynamic processes seem different in various cerebral functional regions.  相似文献   
45.
Li  Ao  Xu  Dezhong  Zhang  Mengnan  Wu  Shengzhong  Li  Yu  Sun  Weisheng  Zhou  Yonghui  Madyan  Omar Abo  Fan  Mizi  Rao  Jiuping 《Cellulose (London, England)》2022,29(3):2017-2032
Cellulose - This paper develops a novel paper additive for effectively recycling old corrugated container (OCC) by functionalizing nanocellulose (NC) with diethylenetriaminepentaacetic acid (DTPA)...  相似文献   
46.
Nanosphere lithography (NSL) has been regarded as an inexpensive, inherently parallel, high-throughput, materials-general approach to the fabrication of nanoparticle arrays. However, the order of the resulting nanoparticle array is essentially dependent on the quality of the colloidal monolayer mask. Furthermore, the lateral feature size of the nanoparticles created using NSL is coupled with the diameter of the colloidal spheres, which makes it inconvenient for studying the size-dependent properties of nanoparticles. In this work, we demonstrate a facile approach to the fabrication of a large-area, transferrable, high-quality latex colloidal mask for nanosphere lithography. The approach is based on a combination of the air/water interface self-assembly method and the solvent-vapor-annealing technique. It enables the fabrication of colloidal masks with a higher crystalline integrity compared to those produced by other strategies. By manipulating the diameter of the colloidal spheres and precisely tuning the solvent-vapor-annealing process, flexible control of the size, shape, and spacing of the interstice in a colloidal mask can be realized, which may facilitate the broad use of NSL in studying the size-, shape-, and period-dependent optical, magnetic, electronic, and catalytic properties of nanomaterials.  相似文献   
47.
依据标准曲线法建立了单扫描极谱法测定食品中苏丹红Ⅰ的不确定度评定的数学模型,对影响测量结果的不确定度分量进行了分析,较全面地评定了测定结果的不确定度.单扫描极谱法测定食品中苏丹红Ⅰ的不确定度主要来源于峰电流的重复性、标准曲线的影响、样品称量、标准物质的纯度和称量、实验中量器的校准等因素,其中最主要的分量是通过标准曲线拟合求样品溶液浓度时引入的测量不确定度.  相似文献   
48.
连德忠 《数学研究》2012,45(2):144-158
确立了一类分块矩阵M11 M12 XM21 M22 M23Y M32 M33的最大秩公式,其中,X和Y是两个受限于四元数线性矩阵方程A_1X=C_1,XB_1=C_2,A_3XB_3=C_3,A_2Y=D_1,YB_2=D_2.的变量矩阵。作为该公式的一项应用,我们推导出上述矩阵方程解集等同于另一四元数二次矩阵方程组解集的条件。  相似文献   
49.
A single crystal of Te2V2O9 with dimensions of 15×15×5 mm3 has been grown by the top‐seeded growth method. Infrared and transmission spectra indicate the transmission cutoff wavelength of Te2V2O9 crystal is about 620 nm in visible region and 6.2 μm in infrared region. In addition, band structure and density of states calculations of Te2V2O9 were carried out using the total‐energy code CASTEP based on density functional theory. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
50.
Recently, B. Chow and R.S. Hamilton [3] introduced the cross curvature flow on 3-manifolds. In this paper, we analyze two interesting examples for this new flow. One is on a square torus bundle over a circle, and the other is on a S2 bundle over a circle. We show that the global flow exists in both cases. However, on the former the flow diverges at time infinity, and on the latter the flow converges at time infinity. Mathematics Subject Classification (1991) 53C44  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