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   732篇
  免费   17篇
  国内免费   3篇
化学   480篇
晶体学   12篇
力学   33篇
数学   88篇
物理学   139篇
  2024年   1篇
  2023年   7篇
  2022年   20篇
  2021年   20篇
  2020年   17篇
  2019年   12篇
  2018年   16篇
  2017年   5篇
  2016年   26篇
  2015年   23篇
  2014年   23篇
  2013年   37篇
  2012年   60篇
  2011年   65篇
  2010年   38篇
  2009年   36篇
  2008年   47篇
  2007年   56篇
  2006年   43篇
  2005年   52篇
  2004年   28篇
  2003年   25篇
  2002年   30篇
  2001年   3篇
  2000年   6篇
  1999年   4篇
  1998年   3篇
  1997年   4篇
  1996年   10篇
  1995年   3篇
  1994年   5篇
  1993年   5篇
  1992年   5篇
  1991年   1篇
  1990年   3篇
  1988年   3篇
  1987年   1篇
  1986年   2篇
  1985年   2篇
  1982年   2篇
  1979年   1篇
  1976年   1篇
  1915年   1篇
排序方式: 共有752条查询结果,搜索用时 15 毫秒
161.
A new polymer based on a functionalized benzofulvene moiety has been synthesized by spontaneous polymerization of the monomer in the solid state. This polymer shows a very high molar mass, high solubility in the most common organic solvents, and thermoreversible polymerization properties. An interesting application in synthesis is reported.  相似文献   
162.
163.
The rearrangement of γ-chlm, β-hydroxy or β-vmyl N-allyl-N-benzyl-α,α-dichlorocarboxyamides to γ-aminobutynic acid analogues is efficiently promoted by CuCI\N,N,N′,N′-tetramethylethylendiamine. With the β-vinyl functionalization a tandem radical-radical reaction, yieldmg 3-aza-2-oxo-bicyclo[3,3,0]actatre adducts, is also observed.  相似文献   
164.
A numerical study of scalar dispersion is presented to investigate the effectiveness of pairing the v2f turbulence model with algebraic models for the scalar flux. This approach is contrasted with utilizing a full Second Moment Closure (SMC) as the flow field input to the scalar model. Predictions of scalar transport in a turbulent channel and over a wavy wall are compared to available DNS databases. The latter case includes a scalar release from a point source and therefore detailed comparisons of the three-component turbulent scalar flux are reported. It is found that the transported variable v2, representing the near wall turbulent velocity fluctuation scale, can be used to increase the level of normal stress anisotropy provided to algebraic scalar models and thereby improve mean scalar prediction over that of the Standard Gradient Diffusion Hypothesis (SGDH). Improvement is most significant in the near wall region. Three specifications of the normal stresses, derived from v2, are considered to provide the link from the v2f model to the algebraic flux models used to close the scalar transport equation. Barycentric maps are used to examine the state of turbulence anisotropy in each case. As the anisotropy in the normal stress specification becomes more accurate, improvements are realized in the prediction of the spanwise flux as well as the mean concentration.  相似文献   
165.
As a simple model for piezoelectricity we consider a gas of infinitely many non-interacting electrons subject to a slowly time-dependent periodic potential. We show that in the adiabatic limit the macroscopic current is determined by the geometry of the Bloch bundle. As a consequence we obtain the King-Smith and Vanderbilt formula up to errors smaller than any power of the adiabatic parameter.  相似文献   
166.
Moscolari  Massimo  Panati  Gianluca 《Acta Appl Math》2019,162(1):105-120

We investigate the relation between broken time-reversal symmetry and localization of the electronic states, in the explicitly tractable case of the Landau model. We first review, for the reader’s convenience, the symmetries of the Landau Hamiltonian and the relation of the latter with the Segal-Bargmann representation of Quantum Mechanics. We then study the localization properties of the Landau eigenstates by applying an abstract version of the Balian-Low Theorem to the operators corresponding to the coordinates of the centre of the cyclotron orbit in the classical theory. Our proof of the Balian-Low Theorem, although based on Battle’s main argument, has the advantage of being representation-independent.

  相似文献   
167.
Trastuzumab, a humanized monoclonal antibody directed against the epidermal growth factor receptor 2 (HER2), is a milestone in the treatment of HER2-overexpressing breast cancer patients. An enzyme-linked immunosorbent assay (ELISA) for trastuzumab has been developed for routine use in the laboratory to support clinical and pharmacokinetic studies to optimize therapy. The method relies on an antigen peptide linked to a 96-well plate via the streptavidin/biotin system. The peptide sequence mimics the extracellular portion of the HER2 receptor that is recognized by trastuzumab. The calibration range of the assay is 10 to 360 ng/mL per well, corresponding to a trastuzumab serum concentration from 5 to 180 μg/mL with a lower limit of quantification of 10 μg/mL. Validation results demonstrate that trastuzumab can be accurately and precisely quantified in human serum using this assay. The procedure was also tested in sera obtained from breast cancer patients to evaluate trastuzumab serum levels, confirming the applicability of method that could be a valid assay to use in daily laboratory practice.  相似文献   
168.
169.
We consider the weak solution of the Laplace equation in a planar domain with a straight crack, prescribing a homogeneous Neumann condition on the crack and a nonhomogeneous Dirichlet condition on the rest of the boundary. For every k we express the k-th derivative of the energy with respect to the crack length in terms of a finite number of coefficients of the asymptotic expansion of the solution near the crack tip and of a finite number of other parameters, which only depend on the shape of the domain.  相似文献   
170.
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