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   507篇
  免费   13篇
化学   330篇
晶体学   7篇
力学   6篇
数学   53篇
物理学   124篇
  2023年   4篇
  2022年   5篇
  2021年   8篇
  2020年   5篇
  2019年   11篇
  2018年   4篇
  2017年   5篇
  2015年   4篇
  2014年   17篇
  2013年   26篇
  2012年   21篇
  2011年   30篇
  2010年   12篇
  2009年   11篇
  2008年   22篇
  2007年   28篇
  2006年   23篇
  2005年   26篇
  2004年   18篇
  2003年   17篇
  2002年   13篇
  2001年   8篇
  2000年   12篇
  1999年   11篇
  1996年   7篇
  1995年   4篇
  1994年   10篇
  1993年   5篇
  1992年   10篇
  1991年   7篇
  1989年   5篇
  1988年   3篇
  1987年   4篇
  1986年   3篇
  1985年   7篇
  1984年   4篇
  1983年   6篇
  1982年   12篇
  1981年   5篇
  1980年   8篇
  1979年   7篇
  1978年   4篇
  1977年   6篇
  1976年   5篇
  1975年   5篇
  1974年   5篇
  1973年   7篇
  1972年   3篇
  1971年   7篇
  1966年   3篇
排序方式: 共有520条查询结果,搜索用时 390 毫秒
61.
The authors follow up some previous work on the dynamics of pension funding by three notes. The first of these concerns contribution rates consisting of the normal cost plus a generalized amortization method for unfunded supplemental present value (actuarial accrued liability). The second note examines aggregate cost funding for active members when there exist consistent difference between the assumed and the actual rates of interest and of growth. The third note explores the operation of a variable annuity system in the context of our general model for pension funding dynamics.  相似文献   
62.
The paper develops a theory of electron transfer with torsionally induced non-Condon (NC) effects. The starting point of the theory is a generalized spin-boson Hamiltonian, where an additional torsional oscillator bilinearly coupled to other bath modes causes a sinusoidal NC modulation. We derive closed form time dependent nonadiabatic rate expressions for both sudden and relaxed initial conditions, which are applicable for general spectral densities and energetic condition. Under the assumption that the torsional motion is not correlated with the polaronic shift of the bath, simple stationary limit rate expression is obtained. Model calculations of this rate expression illustrate the effects of torsional quantization and gating on the driving force and temperature dependences of the electron transfer rate. The classical limit of the rate expression consists of three Marcus-type terms, and is shown to agree very well with the exact numerical result.  相似文献   
63.
Switching between superhydrophobicity and superhydrophilicity in porous materials was predicted theoretically and demonstrated experimentally with the example of thermally induced contact angle change; tunability of this system was also demonstrated.  相似文献   
64.
The redox behaviour of Pd-based TWCs is studied under dynamic, cycling conditions (e.g. lambda oscillations) on a 50 millisecond scale. Pd temporal response to gas inlet mixture changes is governed by metal-promoter interface properties.  相似文献   
65.
Excitation functions and angular distributions have been measured for the fission of 232Th, 238U, 244Pu and 248Cm induced by 86Kr and 136Xe ions at energies in the vicinity of the Coulomb barrier. No large differences as a function of either target or projectile were found. These results suggest that the main process occuring is not Coulomb fission.  相似文献   
66.
Closed form matrix equations are given for the information matrix of the parameters of the vector mixed autoregressive moving average time series model.  相似文献   
67.
68.
The main structural and electronic factors playing a role in intramolecular dissociative electron transfer of a simple donor-peptide-acceptor (D-peptide-A) model have been investigated by an integrated computational protocol based on the density functional theory, its time-dependent extension, and the polarizable continuum model. Our results allow us to elucidate the electronic states involved in the process and how they are perturbed by the orientation of the donor and the acceptor with respect to the peptide chain and by the presence of the solvent. We also report a semiquantitative estimation of the rate constant governing electron transfer obtained by a direct quantum mechanical evaluation of all the terms entering the kinetic expressions based on the Marcus theory and its extensions.  相似文献   
69.
We describe a proteomics procedure using bioinformatics, immunoprecipitation, two-dimensional gel electrophoresis, Western blotting, in-gel digestion, LC–MS, MALDI–MS, and MS–MS for isolation and identification of amyloid precursor protein (APP) isoforms APP695, APP751, and APP770. Retinoic acid-induced Ntera 2 cell line, derived from a human teratocarcinoma cells, was the in-vitro source of APP. Initial isolation of whole APP was performed by immunoprecipitation, using AB10, a monoclonal antibody raised to amino acids 1–17 of the β-amyloid peptide sequence, which is present in all three alpha secretase-cleaved isoforms of interest. The next stage was separation of whole APP into its isoform components by two-dimensional gel electrophoresis. Because of low APP concentrations, detection by the usual staining methods, for example Sypro Ruby, able to detect low picomole concentrations, did not enable visualisation of the isoforms. Western analysis, however, enabled primary detection of APP, because of the inherent sensitivity of antibodies raised to specific isoform regions. This initial visualization acted as a template for excision of isoforms from 2D gels, which were then subjected to peptide mass mapping. Initial theoretical digestion of each isoform revealed the presence of specific peptides, which were then used as “tags” for isoform detection.  相似文献   
70.
It is shown that the space of infinitesimal deformations of 2k-Einstein structures is finite dimensional on compact non-flat space forms. Moreover, spherical space forms are shown to be rigid in the sense that they are isolated in the corresponding moduli space.  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