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   253篇
  免费   0篇
  国内免费   1篇
化学   108篇
晶体学   1篇
力学   24篇
数学   88篇
物理学   33篇
  2020年   3篇
  2019年   3篇
  2017年   4篇
  2016年   9篇
  2015年   8篇
  2014年   7篇
  2013年   12篇
  2012年   13篇
  2011年   12篇
  2010年   7篇
  2009年   9篇
  2008年   10篇
  2007年   10篇
  2006年   9篇
  2005年   13篇
  2004年   12篇
  2003年   6篇
  2002年   6篇
  2000年   7篇
  1999年   5篇
  1998年   3篇
  1996年   5篇
  1995年   2篇
  1994年   2篇
  1993年   3篇
  1991年   3篇
  1990年   3篇
  1985年   3篇
  1984年   5篇
  1982年   2篇
  1981年   3篇
  1980年   3篇
  1979年   5篇
  1978年   5篇
  1976年   4篇
  1975年   5篇
  1974年   2篇
  1973年   4篇
  1972年   2篇
  1970年   1篇
  1968年   1篇
  1967年   2篇
  1966年   2篇
  1964年   1篇
  1958年   1篇
  1915年   1篇
  1909年   1篇
  1901年   1篇
  1888年   1篇
  1862年   1篇
排序方式: 共有254条查询结果,搜索用时 20 毫秒
11.
Nitrate radical (NO(3)) reactions with benzene (R-1), toluene (R-2), p-xylene (R-3), p-cresol (R-4) and mesitylene (R-5) have been studied by laser photolysis/long path laser absorption (LP-LPLA) in aqueous solution. Rate constants of k(1)=(4.0+/-0.6). 10(8), k(2)=(1.2+/-0.3). 10(9), k(3)=(1.6+/-0.1). 10(9), k(4)= (8.4+/-2.3). 10(8) and k(5)=(1.3+/-0.3). 10(9) lmol(-1)s(-1) were obtained at T=298 K. In addition, reaction rate coefficients for SO(-)(5)+Fe(2+)-->prod. (R-6) and SO(-)(5)+Mn(2+)-->prod. (R-7) of k(6)=(4.3+/-2.4). 10(7) lmol(-1)s(-1) and k(7)=(4.6+/-1.0). 10(6) lmol(-1)s(-1) (T=298 K, I-->0) have been obtained by the application of laser photolysis/UV-VIS broadband diode array spectroscopy. A new laser photolysis/UV-long path laser absorption experiment has been applied to study the reaction of the Cl(-)(2) radical anion with dissolved sulfur(IV). For the reactions Cl(-)(2)+HSO(-)(3)-->2Cl(-)+H(+)+SO(-)(3) (R-8) and Cl(-)(2)+SO(2-)(3)-->2Cl(-)+SO(-)(3) (R-9) rate coefficients of k(8)=(1.7+/-0.2). 10(8) lmol(-1)s(-1) (T=298 K, I-->0) and of k(9)=(6.2+/-0.3). 10(7) lmol(-1)s(-1) (T=279 K, I-->0) were obtained.  相似文献   
12.
This work is concerned with the development of an efficient two-scale numerical scheme for the prediction of the local and effective mechanical response of heterogeneous materials with non-linear constitutive behavior. In order to ensure both, accurate micromechanical fields and feasible overall CPU-times, an efficient but rather simple solution scheme is proposed. Its capabilities are demonstrated using the FE-FFT method [2,3] for the solution of simple two-scale problems. As an example, two-dimensional polycrystalline microstructures with an elasto-viscoplastic constitutive law are considered. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
13.
In this work, the simulation of earings in cup drawing by means of a recently developed anisotropic combined hardening material model is discussed. The model represents a multiplicative formulation of anisotropic elastoplasticity in the finite strain regime with nonlinear kinematic and isotropic hardening. Plastic anisotropy is described by the use of second-order structure tensors as additional arguments in the representation of the yield function and the plastic flow rule. The evolution equations are integrated by a form of the exponential map that preserves the plastic volume and the symmetry of the internal variables. Finite element simulations of cylindrical cup drawing processes are performed by means of ABAQUS/Standard where the discussed material model has been implemented into a user-defined reduced integration solid-shell element. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
14.
Laminated paperboard is widely used in packaging products. It usually consists of multiple layers bonded to each other by starch or adhesion. The indentation of fold lines (creasing) plays a crucial role during the whole converting process. It is important to control delamination and other damage effects to arrive at commercial cartons with high quality. Thus, the aim of this study is to describe the material behavior of a laminated paperboard during the creasing process. The paperboard was considered as a laminate of three different layers, and each was modeled separately with an anisotropic elastic-plastic material model while a cohesive zone approach described the opening behavior in between. The initial yielding was given by the Hill's 48 yield criterion, while the isotropic strain hardening was described by a power law hardening function. To calibrate the material parameters, a sequence of tensile and compression tests was conducted for each layer in different directions to account for the material's anisotropy. Finally, the creasing process was investigated using a two-dimensional plane strain finite element model. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
15.
Fibre reinforced composites consisting of several layers, each of which is composed of a woven fabric embedded in a matrix material, are investigated in this paper. Such materials are characterized by a complex anisotropic behavior, which necessitates a fully three-dimensional formulation of the constitutive equations. On the other hand, they are frequently used in thin shell-like applications. In order to account for the three-dimensional material law while still providing the suitable shape for thin structures, a solid-shell finite element for fibre composite materials is presented herein. Locking phenomena are treated by both the enhanced assumed strain (EAS) concept and the assumed natural strain concept (ANS). Using reduced integration together with hourglass stabilization leads to high computational efficiency. The anisotropic constitutive behavior of the composites is reflected by a micromechanically motivated continuum model, which –together with the solid-shell formulation– allows for an accurate representation of the through-the-thickness stress distribution even for thin structures. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
16.
For bounded normal operators in Krein spaces we give a necessary and sufficient condition for strong stability. The same result for unitary operators was obtained by M.G.Krein [1] (see also [2]). For selfadjoint operators we refer to the papers of P.Jonas, H.Langer [3] and H.Langer [4].  相似文献   
17.
The present contribution focuses on the finite element modelling of NiTi‐based shape memory alloys. For this purpose, the concept of Helm [1] has been further developed and implemented into a finite element formulation. The model is able to describe the multiaxial behaviour of SMA and therefore useful for the simulation of complex problems. Additional emphasis is put on the modelling of the shape memory effect in composites where the interaction between the alloy and other materials like e.g. polymers plays an important role. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
18.
We give a characterization of the boundaries of holomorphic chains in complex projective space. This extends previous work of the authors and complements results of Dolbeault and Henkin.  相似文献   
19.
This paper presents a simple, self‐contained account of Gårding's theory of hyperbolic polynomials, together with a recent convexity result of Bauschke‐Güler‐Lewis‐Sendov and an inequality of Gurvits. This account begins by establishing some new results. The first concerns the existence of a pointwise arrangement of the eigenvalues so that they become global real analytic functions. The second asserts that the associated “branches” are independent of the choice of hyperbolic direction. © 2013 Wiley Periodicals, Inc.  相似文献   
20.
TS ENKHBAT 《Pramana》2012,79(4):879-882
A study of bound states of the fourth-generation quarks in the range of 500?C700 GeV is presented, where the binding energies are expected to be mainly of Yukawa origin, with QCD subdominant. Near degeneracy of their masses exhibits a new ??isospin??. The production of a colour-octet, isosinglet vector meson via $q\bar q \to \omega_8$ is the most interesting. Its leading decay modes are $\pi_8^\pm W^\mp$ , $\pi_8^0Z^0$ , and constituent quark decay, with $q\bar q$ and $t\bar t'$ and $b\bar b'$ subdominant. The colour octet, isovector pseudoscalar ?? 8 meson decays via constituent quark decay, or to Wg. This work calls for more detailed study of fourth-generation phenomena at LHC.  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