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   899篇
  免费   63篇
  国内免费   2篇
化学   671篇
晶体学   4篇
力学   11篇
数学   156篇
物理学   122篇
  2023年   5篇
  2022年   19篇
  2021年   28篇
  2020年   27篇
  2019年   29篇
  2018年   20篇
  2017年   14篇
  2016年   36篇
  2015年   48篇
  2014年   56篇
  2013年   57篇
  2012年   64篇
  2011年   72篇
  2010年   41篇
  2009年   33篇
  2008年   52篇
  2007年   62篇
  2006年   51篇
  2005年   46篇
  2004年   30篇
  2003年   27篇
  2002年   21篇
  2001年   8篇
  2000年   15篇
  1999年   6篇
  1998年   8篇
  1997年   11篇
  1996年   5篇
  1995年   3篇
  1994年   6篇
  1993年   6篇
  1992年   5篇
  1991年   3篇
  1990年   3篇
  1989年   2篇
  1988年   3篇
  1987年   2篇
  1986年   2篇
  1984年   2篇
  1983年   3篇
  1982年   5篇
  1981年   4篇
  1977年   2篇
  1976年   2篇
  1972年   2篇
  1971年   2篇
  1969年   3篇
  1958年   2篇
  1954年   1篇
  1909年   2篇
排序方式: 共有964条查询结果,搜索用时 15 毫秒
891.
892.
The adsorption of individual [11]anthrahelicene molecules and their self‐assembly into monolayer islands on an InSb(001) c(8×2) reconstructed surface is studied with low‐temperature scanning probe microscopy. A racemic mixture is deposited on atomically flat terraces of InSb at room temperature. At lower coverage, the molecules tend to decorate atomic step edges of the substrate. At higher coverage, [11]anthrahelicene molecules form 2D islands. A quasi‐hexagonal ordering of molecules within the layer is identified. Furthermore, it is shown that molecules adsorb with the helical axis almost perpendicular to the substrate. Interference between tunneling through the molecular layer and directly through space is reported. Finally, experimental results are compared to those of theoretical calculations.  相似文献   
893.
894.
Novel bis‐4,9‐diazapyrenium dication has shown reversible pH dependent formation of 4,9‐ diazapyrenium pseudobase in water characteristic for most 4,9‐diazapyrenium derivatives. The compound has formed non‐covalent complexes with nucleotides in water, whose stability is controlled dominantly by aromatic stacking interactions. No cooperativity between two 4,9‐diazapyrenium subunits was observed in binding of nucleotides. Novel bis‐4,9‐diazapyrenium dication formed mono‐intercalative complexes with studied double stranded DNA and RNA. Additional interactions of non‐intercalated part were found to depend significantly on the polynucleotide secondary structure, yielding strong DNA over RNA preference. Appearance of ICD band of 3 was found to be specific for DNA polynucleotides and together with observed destabilisation of double stranded RNA is attributed to the aggregation of compound in one of the RNA grooves. All bis‐4,9‐diazapyrenium dications prepared till now have shown considerable antiproliferative activity against five human tumour cell lines, which suggested mechanism of action by interacting with cell DNA. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   
895.
896.
The construction of new mediator-free and fully electroactive protein multilayer electrodes based on DNA and cyt c is demonstrated. The assembly is characterized by a rather high stability, effective electron transfer, and a tunability of the electroactive protein amount by the number of deposited cyt c layers.  相似文献   
897.
In this paper we consider the inverse problem of recovering the viscosity coefficient in a dissipative wave equation via boundary measurements. We obtain stability estimates by considering all possible measurements implemented on the boundary. We also prove that the viscosity coefficient is uniquely determined by a finite number of measurements on the boundary provided that it belongs to a given finite dimensional vector space.  相似文献   
898.
Five different isotopologues of the benzoic acid dimer and a vibronic band located 57 cm?1 above the electronic origin, which is assigned to the out‐of‐plane butterfly motion, are studied by rotationally resolved UV spectroscopy. From these measurements a ground‐state structure with C2h symmetry is deduced, whereas the symmetry is lowered to Cs in the S1 state. The increase in the center‐of‐mass distance between the two monomers that is found on electronic excitation indicates a decrease in hydrogen‐bond strength. The tunneling splittings in the S0 and S1 states are 1385.2±0.7 and 271.2±0.7 MHz, respectively, corresponding to an increase in barrier height by 7.2 % on electronic excitation.  相似文献   
899.
Nonlinear least squares optimization problems in which the parameters can be partitioned into two sets such that optimal estimates of parameters in one set are easy to solve for given fixed values of the parameters in the other set are common in practice. Particularly ubiquitous are data fitting problems in which the model function is a linear combination of nonlinear functions, which may be addressed with the variable projection algorithm due to Golub and Pereyra. In this paper we review variable projection, with special emphasis on its application to matrix data. The generalization of the algorithm to separable problems in which the linear coefficients of the nonlinear functions are subject to constraints is also discussed. Variable projection has been instrumental for model-based data analysis in multi-way spectroscopy, time-resolved microscopy and gas or liquid chromatography mass spectrometry, and we give an overview of applications in these domains, illustrated by brief case studies.  相似文献   
900.
    
  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