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   2742篇
  免费   323篇
  国内免费   179篇
化学   671篇
晶体学   7篇
力学   466篇
综合类   32篇
数学   926篇
物理学   1142篇
  2024年   2篇
  2023年   37篇
  2022年   52篇
  2021年   61篇
  2020年   108篇
  2019年   79篇
  2018年   83篇
  2017年   107篇
  2016年   104篇
  2015年   67篇
  2014年   144篇
  2013年   169篇
  2012年   138篇
  2011年   158篇
  2010年   159篇
  2009年   170篇
  2008年   201篇
  2007年   158篇
  2006年   152篇
  2005年   175篇
  2004年   146篇
  2003年   131篇
  2002年   90篇
  2001年   88篇
  2000年   56篇
  1999年   50篇
  1998年   44篇
  1997年   44篇
  1996年   34篇
  1995年   23篇
  1994年   33篇
  1993年   19篇
  1992年   20篇
  1991年   22篇
  1990年   19篇
  1989年   9篇
  1988年   15篇
  1987年   11篇
  1986年   14篇
  1985年   5篇
  1984年   6篇
  1983年   4篇
  1982年   5篇
  1981年   8篇
  1980年   7篇
  1979年   4篇
  1978年   5篇
  1976年   2篇
  1971年   2篇
  1969年   1篇
排序方式: 共有3244条查询结果,搜索用时 218 毫秒
951.
运用经典哈密顿代数方法 ,结合陪集表象构造了类比于热力学中熵的H函数。研究表明 ,H函数随时间增加而增大的特性可以用来表示分子内振动能量传递的方向和限度。同时 ,H函数的速率能够很好地表明水和氰化氘体系的共振特性  相似文献   
952.
Polarization properties of strange baryons produced in pp reactions, p + p↦p + Λ0 + K+ and p + p↦p + Σ0 + K+, near thresholds of the final states pΛ0K+ and pΣ0K+ are analysed relative to polarizations of colliding protons. The cross-sections for pp reactions are calculated within the effective Lagrangian approach accounting for strong pp rescattering in the initial state of colliding protons with a dominant contribution of the one-pion exchange and strong final-state interaction of daughter hadrons (Eur. Phys. J. A 9, 425 (2000)). Received: 22 October 2001 / Accepted: 14 November 2001  相似文献   
953.
Summary: The miscibility of a thermoplastic modifier with the precursors of an epoxy/diamine thermoset without chemical reaction was studied thermodynamically. The experimental cloud point curve showed a UCST behavior. A model based on the Flory‐Huggins lattice theory and on the Koningsveld approach was used for the thermodynamic analysis, in which the polydispersity of components was taken into account and the interaction parameter was considered depending on the temperature and composition. A phase diagram for the unreacted system was obtained. Calculations of species distributions in both separated phases were realized for different compositions of the modifier. Finally, the miscibility of our system was compared with that of the same system without diamine, obtaining a greater miscibility in the system with diamine.

Phase diagram for the system formed by the precursors of an epoxy thermoset without chemical reaction modified with different amounts of polystyrene.  相似文献   

954.
In this paper, the extended projective approach, which was recently presented and successfully used in some continuous nonlinear physical systems, is generalized to nonlinear partial differential-difference systems (DDEs). As a concrete example, new families of exact solutions to the (2+1)-dimensional Toda lattice system are obtained by the extended projective approach.  相似文献   
955.
A variable separation approach is proposed and extended to the (1+1)-dimensional physics system. The variable separation solution of (1+1)-dimensional Ito system is obtained. Some special types of solutions such as non-propagating solitary wave solution, propagating solitary wave solution and looped soliton solution are found by selecting the arbitrary function appropriately.  相似文献   
956.
In this paper,the variable separation approach is used to obtain localized coherent structures of the (2 1)-dimensional generalized Davey-Stewarson equations:iqt 1/2(qxx=qyy) (R S)q=0,Rx=-σ/2|q|y^2,Sy=-σ/2|q|2/x.Applying a special Baecklund transformation and introducing arbitrary functions of the seed solutions.and abundance of the localized structures of this model is derived,By selceting the arbitrary functions appropriately,some special types of localized excitations such as dromions,dromion lattice,breathers,and instantons are constructed.  相似文献   
957.
The Hamilton-Jacobi method of quantizing singular systems is discussed.The equations of motion are obtained as total differential equations in many variables.It is shown that if the system is integrable,one can obtain the canonical phase space coordinates and set of canonical Hamilton-Jacobi partial differential equations without any need to introduce unphysical auxiliary fields.As an example we quantize the O(2) nonlinear sigma model using two different approaches:the functional Schrodinger method to obtain the wave functionals for the ground and the exited state and then we quantize the same model using the canonical path integral quantization as an integration over the canonical phase-space coordinates.  相似文献   
958.
By means of an improved mapping method and a variable separation method, a series of variable separation solutions including solitary wave solutions, periodic wave solutions and rational function solutions) to the (2+1)-dimensional breaking soliton system is derived. Based on the derived solitary wave excitation, we obtain some special annihilation solitons and chaotic solitons in this short note.  相似文献   
959.
吴晓飞  朱加民  马正义 《中国物理》2007,16(8):2159-2166
In this paper, the improved Jacobian elliptic function expansion approach is extended and applied to constructing discrete solutions of the semi-discrete coupled modified Korteweg de Vries (mKdV) equations with the aid of the symbolic computation system Maple. Some new discrete Jacobian doubly periodic solutions are obtained. When the modulus $m \rightarrow 1$, these doubly periodic solutions degenerate into the corresponding solitary wave solutions, including kink-type, bell-type and other types of excitations.  相似文献   
960.
余春日  史守华  汪荣凯  杨向东 《中国物理》2007,16(11):3345-3351
An interaction potential of the Ne-HC1 van der Waals complex is obtained by utilizing the Huxley analytic potential function to fit the accurate interaction energy data, which have been computed at the coupled cluster singles and doubles including connected triple excitations level and with the augmented correlation consistent polarized valence quintuple zeta basis set extended with a set of 3s3p2dlflg mid-bond functions [CCSD (T)/aug-cc-pV5Z-33211]. The close coupling calculation of state-to-state partial cross sections for collision of Ne with HC1 is first performed by employing the fitted interaction potential. This calculation is performed at the incident energies: 40, 60, 75 and 100 meV, separately. The effects of the long-range attractive and the short-range anisotropic interactions on the inelastic state-to-state partial cross sections are discussed in detail. Two maxima are present in the rotationally inelastic partial cross sections and they originate from different mechanisms.[第一段]  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