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   5203篇
  免费   148篇
  国内免费   17篇
化学   3995篇
晶体学   30篇
力学   120篇
数学   546篇
物理学   677篇
  2023年   37篇
  2022年   142篇
  2021年   214篇
  2020年   130篇
  2019年   162篇
  2018年   151篇
  2017年   113篇
  2016年   196篇
  2015年   173篇
  2014年   161篇
  2013年   336篇
  2012年   369篇
  2011年   370篇
  2010年   254篇
  2009年   198篇
  2008年   302篇
  2007年   333篇
  2006年   287篇
  2005年   234篇
  2004年   205篇
  2003年   174篇
  2002年   143篇
  2001年   54篇
  2000年   67篇
  1999年   48篇
  1998年   54篇
  1997年   39篇
  1996年   51篇
  1995年   27篇
  1994年   33篇
  1993年   31篇
  1992年   28篇
  1991年   23篇
  1990年   13篇
  1989年   9篇
  1988年   15篇
  1987年   17篇
  1985年   10篇
  1984年   18篇
  1983年   10篇
  1982年   13篇
  1981年   12篇
  1980年   8篇
  1979年   12篇
  1978年   13篇
  1976年   8篇
  1975年   7篇
  1974年   8篇
  1972年   9篇
  1970年   8篇
排序方式: 共有5368条查询结果,搜索用时 2 毫秒
41.
The Carleson maximal operator is shown to be bounded inL p (w) for certain values ofp and certain radial weightsw when acting on products of radial functions and homogeneous harmonic polynomials. Partially supported by DGICYT (MEC Spain). PB 92/187.  相似文献   
42.
The construction principle and the applicable system are considered for the highpower laser amplifier module of the “Del'fin” facility, intended for spherical heating of thermonuclear targets. Results are presented of investigations of the radiation parameters of the amplifier module under various operating regimes. The system for focusing the laser radiation on the target surfaces is described and the results of experiments on plasma heating by radiation of three composite laser beams, at a laser energy level up to 1 kJ at a flux density up to 1014 W/cm2, are analyzed.  相似文献   
43.
The interrelationship between electrical conductivity, molar volume and enthalpy of mixing was studied for molten chlorides and their mixtures. The dependence of electrical conductivity and activation energy on the molar volume is different for various groups of salts. The dependence of specific conductivity on molar volume obtained for molten alkali chlorides was found to be similar to other chloride salts. The specific conductivity of binary mixtures that lack strong chemical interactions between the components can also be described by the proposed empirical equation. The enthalpy of mixing should be taken into consideration for these chemical interactions.  相似文献   
44.
In this paper we try to bridge breakthroughs in quantitative sociology/econometrics, pioneered during the last decades by Mac Fadden, Brock–Durlauf, Granovetter and Watts–Strogatz, by introducing a minimal model able to reproduce essentially all the features of social behavior highlighted by these authors.  相似文献   
45.
We show an accurate procedure to obtain a Fourier transform (FT) with no dc term using a commercial twisted-nematic liquid-crystal display. We focus on the application to holographic storage of binary data pages, where a drastic decrease of the dc term in the FT is highly desirable. Two different codification schemes are considered: binary pi radians phase modulation and hybrid ternary modulation. Any deviation in the values of the amplitude and phase shift generates the appearance of a strong dc term. Experimental results confirm that the calculated configurations provide a FT with no dc term, thus showing the effectiveness of the proposal.  相似文献   
46.
A formula for the complex refractive index of a medium exposed to light whose amplitude and frequency are varied in time is derived.  相似文献   
47.
This paper presents the results of investigations of three types of carbon structures synthesized by different methods, such as arc discharge plasma enhanced chemical vapor deposition of carbon in a magnetic field, chemical dehydrohalogenation of the poly(vinyl chloride)/poly(vinylidene chloride) precursor, and pulsed plasma ion assisted deposition. It has been found that the samples prepared by different methods have a common feature, i.e., the presence of three-dimensional clusters based on sp2- or sp3-bonds surrounded by quasi-one-dimensional carbon chains. It has been shown that the structure of carbon materials changes depending on the synthesis conditions.  相似文献   
48.
Using results of equilibrium molecular dynamics simulation in conjunction with the Green–Kubo formalism, we present a general treatment of thermal impedance of a crystal lattice with a monatomic unit cell. The treatment is based on an analytical expression for the heat current autocorrelation function which reveals, in a monatomic lattice, an energy gap between the origin of the phonon states and the beginning of the energy spectrum of the so-called acoustic short-range phonon modes. Although, we consider here the f.c.c. Al model as a case example, the analytical expression is shown to be consistent for different models of elemental f.c.c. crystals over a wide temperature range. Furthermore, we predict a frequency ‘window’ where the thermal waves can be generated in a monatomic lattice by an external periodic temperature perturbation.  相似文献   
49.
The recently introduced analytical model for the heat current autocorrelation function of a crystal with a monatomic lattice [Evteev et al., Phil. Mag. 94 (2014) p. 731 and 94 (2014) p. 3992] is employed in conjunction with the Green–Kubo formalism to investigate in detail the results of an equilibrium molecular dynamics calculations of the temperature dependence of the lattice thermal conductivity and phonon dynamics in f.c.c. Ni. Only the contribution to the lattice thermal conductivity determined by the phonon–phonon scattering processes is considered, while the contribution due to phonon–electron scattering processes is intentionally ignored. Nonetheless, during comparison of our data with experiment an estimation of the second contribution is made. Furthermore, by comparing the results obtained for f.c.c. Ni model to those for other models of elemental crystals with the f.c.c. lattice, we give an estimation of the scaling relations of the lattice thermal conductivity with other lattice properties such as the coefficient of thermal expansion and the bulk modulus. Moreover, within the framework of linear response theory and the fluctuation-dissipation theorem, we extend our analysis in this paper into the frequency domain to predict the power spectra of equilibrium fluctuations associated with the phonon-mediated heat dissipation in a monatomic lattice. The practical importance of the analytical treatment lies in the fact that it has the potential to be used in the future to efficiently decode the generic information on the lattice thermal conductivity and phonon dynamics from a power spectrum of the acoustic excitations in a monatomic crystal measured by a spectroscopic technique in the frequency range of about 1–20 THz.  相似文献   
50.
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