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   289767篇
  免费   2055篇
  国内免费   810篇
化学   135813篇
晶体学   4230篇
力学   17115篇
综合类   10篇
数学   54627篇
物理学   80837篇
  2021年   2134篇
  2020年   2244篇
  2019年   2785篇
  2018年   14057篇
  2017年   13828篇
  2016年   11170篇
  2015年   3526篇
  2014年   4973篇
  2013年   9685篇
  2012年   11277篇
  2011年   19039篇
  2010年   12375篇
  2009年   12920篇
  2008年   14728篇
  2007年   16752篇
  2006年   7529篇
  2005年   7719篇
  2004年   7536篇
  2003年   7461篇
  2002年   6496篇
  2001年   6050篇
  2000年   4628篇
  1999年   3408篇
  1998年   2992篇
  1997年   2998篇
  1996年   2861篇
  1995年   2417篇
  1994年   2495篇
  1993年   2432篇
  1992年   2658篇
  1991年   2763篇
  1990年   2654篇
  1989年   2728篇
  1988年   2625篇
  1987年   2648篇
  1986年   2499篇
  1985年   3157篇
  1984年   3211篇
  1983年   2673篇
  1982年   2648篇
  1981年   2605篇
  1980年   2411篇
  1979年   2768篇
  1978年   2734篇
  1977年   2912篇
  1976年   2904篇
  1975年   2701篇
  1974年   2631篇
  1973年   2749篇
  1972年   2112篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
A new geometrical method to determine the surface damage threshold for ultrashort pulses is presented. It consists in the formation of a surface damage profile by a movement of the sample across the laser beam focus. A single measurement of the maximum transversal dimension of this damage profile, which depends solely on the laser beam power, is used to calculate the local damage threshold intensity. It is also theoretically shown that the damage in the transverse dimension can be controlled under the diffraction-limited spot.  相似文献   
22.
The excitation of eigen surface waves by tubular electron beams in cylindrical discharge devices is studied. The influence of the wave‐field azimuthal structure on the excitation efficiency and nonlinear stage of the plasmabeam instability is investigated both numerically and analytically. Analytical expressions for the saturation amplitude and excitation efficiency of the wave under study are derived. They are found to agree well with results obtained by numerical modelling of the plasma‐beam interaction presented in this paper. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
23.
24.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 6, pp. 970–975, June, 1991.  相似文献   
25.
We develop a method of computing the nonsteady-state and free oscillations of a framed elastic structure situated on an elastic base and containing an ideal compressible fluid. The solution uses the method of integral transforms in conjunction with the method of orthogonal polynomials. In the transform space the problem reduces to systems of linear algebraic equations. The Fourier transform is applied to return to the original space. Examples of the computation are given.Translated fromDinamicheskie Sistemy, No. 6, 1987, pp. 69–72.  相似文献   
26.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 51, No. 2, pp. 212–217, August, 1989.  相似文献   
27.
Courses which teach discrete-event simulation are based on many different simulation languages. The requirements for a language to support teaching simulation are discussed. In particular, it is recommended that such languages separate into distinct modules those aspects of simulation which are taught as separate topics. Implementation of the separation is discussed. The SEESIM language, developed as a teaching aid, is described, and examples of its use are given. Straightforward use of SEESIM can be learned quickly, yet the language provides facilities for a staged introduction to advanced concepts of simulation.  相似文献   
28.
Renormalization formulas connecting the points of the orbits O 0 ± , i.e., the sequences generated by an irrational shift on the half-open interval [0, 1) or (0, 1], and the points of the orbits' derivatives dmO 0 ± , i.e., the sequences obtained by restricting O 0 ± to half-open intervals of smaller length, are obtained. Bibliography: 5 titles. __________ Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 314, 2004, pp. 142–154.  相似文献   
29.
A noiselike fine structure of ferromagnetic resonance spectra in magnetic powders was investigated after ultrasonic treatment. Magnetic interactions between particles are proved to have an influence upon the fine structure formation. After decreasing dipole-dipole magnetic interactions in dilute suspension a special order appears in fine-structure spectra, which is generally the same for different systems.  相似文献   
30.
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