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   1324749篇
  免费   29746篇
  国内免费   7711篇
化学   654404篇
晶体学   14502篇
力学   74753篇
综合类   110篇
数学   241628篇
物理学   376809篇
  2021年   12779篇
  2020年   15935篇
  2019年   16078篇
  2018年   14091篇
  2016年   28488篇
  2015年   20961篇
  2014年   30459篇
  2013年   74371篇
  2012年   38856篇
  2011年   36994篇
  2010年   38210篇
  2009年   40475篇
  2008年   35927篇
  2007年   32066篇
  2006年   36347篇
  2005年   30101篇
  2004年   30859篇
  2003年   28833篇
  2002年   26539篇
  2001年   26808篇
  2000年   22549篇
  1999年   20098篇
  1998年   18686篇
  1997年   19299篇
  1996年   19196篇
  1995年   18556篇
  1994年   18075篇
  1993年   17604篇
  1992年   17573篇
  1991年   17854篇
  1990年   17072篇
  1989年   17096篇
  1988年   16736篇
  1987年   16721篇
  1986年   15613篇
  1985年   22153篇
  1984年   23427篇
  1983年   19531篇
  1982年   21259篇
  1981年   20471篇
  1980年   19800篇
  1979年   20071篇
  1978年   21390篇
  1977年   21049篇
  1976年   20791篇
  1975年   19510篇
  1974年   19131篇
  1973年   19690篇
  1972年   14167篇
  1967年   12521篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Theoretical and Mathematical Physics - We present a one-line closed-form expression for the three-parameter breather of the nonlinear Schrödinger equation. This provides an analytic proof of...  相似文献   
82.
Journal of Fourier Analysis and Applications - We develop a theory of Sobolev orthogonal polynomials on the Sierpiński gasket ( $$SG$$ ), which is a fractal set that can be viewed as a limit...  相似文献   
83.
Journal of Applied Spectroscopy - It is shown that the relations for determining a purely electronic transition from diffuse absorption or emission spectra, obtained under the assumption of...  相似文献   
84.
In this article, the effect of ionization on the energy spectrum of electrons within the interaction of a laser pulse with hydrogen atoms is investigated using particle-in-cell simulation codes. The results show that the behaviour of electrons' energy distribution function in the field-ionized plasma, which occurred due to the field ionization, compared with that in the pre-plasma strongly depends on the pulse shape. For short rise-time pulses (here 30 fs), due to the rapid enhancement of laser electric field, ionization occurs quickly, and as a result, there is not much difference in the electron energy in both the media. However, for pulses with rise time of 40 fs, in the pre-plasma state, the electron population reaches higher energies compared with the field-ionized plasma state. The main reason for this difference is the nonlinear wave breaking that happens earlier due to density inhomogeneity in the field-ionized plasma. On the other hand, at longer rise-time pulses (here 60 and 70 fs), electrons achieve higher energies in the field-ionized plasma than those in the case of pre-plasma. In this case, because of density fluctuations in the field-ionized plasma, the Raman backscattered radiations are seeded by a strong initial noise at the earlier times and the Mendonca condition for chaos threshold is met sooner. Therefore, the electrons gain more energy through the stochastic mechanism that is in agreement with chaotic nature of the motion.  相似文献   
85.
Radiophysics and Quantum Electronics - This work is a review of recent results, which have been obtained within the framework of the mathematical theory of dynamical chaos and are related to the...  相似文献   
86.
Garmanova  T. A. 《Mathematical Notes》2021,109(3-4):527-533
Mathematical Notes - The paper deals with sharp estimates of derivatives of intermediate order $$k\le n-1$$ in the Sobolev space $$\mathring W^n_2[0;1]$$ , $$n\in\mathbb N$$ . The functions...  相似文献   
87.
We prove a well-posedness result for two pseudo-parabolic problems, which can be seen as two models for the same electrical conduction phenomenon in heterogeneous media, neglecting the magnetic field. One of the problems is the concentration limit of the other one, when the thickness of the dielectric inclusions goes to zero. The concentrated problem involves a transmission condition through interfaces, which is mediated by a suitable Laplace-Beltrami type equation.  相似文献   
88.
89.
Kobayashi  M.  Zhang  Y.  Ishikawa  H.  Sun  J.  Oddershede  J.  Juul Jensen  D.  Miura  H. 《Experimental Mechanics》2021,61(5):817-828
Experimental Mechanics - The internal strain distribution developing during plastic deformation is important for understanding the mechanical properties of polycrystalline materials. Such...  相似文献   
90.
Journal of Applied Mechanics and Technical Physics - This paper describes a problem of steady-state creep of a long narrow rectangular membrane in the case of a linear dependence between the...  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