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   1292491篇
  免费   29688篇
  国内免费   7604篇
化学   637732篇
晶体学   13878篇
力学   73736篇
综合类   101篇
数学   238840篇
物理学   365496篇
  2021年   12636篇
  2020年   15904篇
  2019年   16035篇
  2016年   27514篇
  2015年   20642篇
  2014年   30352篇
  2013年   74253篇
  2012年   37312篇
  2011年   33501篇
  2010年   36360篇
  2009年   38804篇
  2008年   33130篇
  2007年   28490篇
  2006年   35609篇
  2005年   27353篇
  2004年   28837篇
  2003年   26791篇
  2002年   24881篇
  2001年   26014篇
  2000年   22091篇
  1999年   19930篇
  1998年   18582篇
  1997年   19284篇
  1996年   19143篇
  1995年   18542篇
  1994年   18060篇
  1993年   17571篇
  1992年   17445篇
  1991年   17754篇
  1990年   16982篇
  1989年   17062篇
  1988年   16638篇
  1987年   16612篇
  1986年   15529篇
  1985年   22044篇
  1984年   23379篇
  1983年   19489篇
  1982年   21231篇
  1981年   20450篇
  1980年   19777篇
  1979年   20060篇
  1978年   21374篇
  1977年   21035篇
  1976年   20840篇
  1975年   19490篇
  1974年   19211篇
  1973年   19745篇
  1972年   14206篇
  1968年   12213篇
  1967年   12562篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
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   
82.
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   
83.
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   
84.
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   
85.
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   
86.
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   
87.
88.
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   
89.
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   
90.
Journal of Experimental and Theoretical Physics - The structural (lattice metric) and elastic characteristics of ErBaCo4O7 + x cobaltites, which are subjected to different heat treatment and are...  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