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   333158篇
  免费   6168篇
  国内免费   4902篇
化学   157080篇
晶体学   4591篇
力学   20306篇
综合类   329篇
数学   53102篇
物理学   108820篇
  2022年   2663篇
  2021年   3512篇
  2020年   3813篇
  2019年   4376篇
  2018年   12415篇
  2017年   12862篇
  2016年   10100篇
  2015年   4562篇
  2014年   6592篇
  2013年   11200篇
  2012年   13330篇
  2011年   21168篇
  2010年   14546篇
  2009年   14893篇
  2008年   18597篇
  2007年   21290篇
  2006年   8813篇
  2005年   12425篇
  2004年   9584篇
  2003年   9335篇
  2002年   7957篇
  2001年   7109篇
  2000年   5556篇
  1999年   4180篇
  1998年   3859篇
  1997年   3516篇
  1996年   3459篇
  1995年   3023篇
  1994年   3008篇
  1993年   2975篇
  1992年   2959篇
  1991年   3281篇
  1990年   3190篇
  1989年   3200篇
  1988年   2988篇
  1987年   2997篇
  1986年   2799篇
  1985年   3348篇
  1984年   3400篇
  1983年   2970篇
  1982年   2996篇
  1981年   2827篇
  1979年   3026篇
  1978年   3180篇
  1977年   3179篇
  1976年   3396篇
  1975年   3085篇
  1974年   3047篇
  1973年   3266篇
  1972年   2665篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
We find logarithmic small ball asymptotics for the L2-norm with respect to self-similar measures for a certain class of Gaussian processes including Brownian motion, Ornstein-Uhlenbeck process, and their integrated counterparts. Bibliography: 46 titles. __________ Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 311, 2004, pp. 190–213.  相似文献   
42.
The main result of the paper is a theorem, using which a new proof of Roth’s theorem is obtained, a new solvability criterion for the matrix equation AX-YB = C is proved, a formula for a particular solution of the latter is derived, and the least of the orders of square nonsingular matrices containing a given rectangular matrix as a submatrix is determined. Bibliography: 5 titles. __________ Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 323, 2005, pp. 15–23.  相似文献   
43.
Using the method of the tensor Green’s function of the wave equation, the differential and total cross sections for the scattering of surface optical electromagnetic waves (surface plasmon polaritons) by a spherical nanoparticle into surface plasmon polaritons and light have been obtained with the inclusion of the magnetic dipole contribution. Using the example of noble metal systems, it has been shown that the magnetic dipole contribution may significantly affect the angular dependence of the differential cross sections and increase their anisotropy as the plasmon wavelength increases.  相似文献   
44.
We report morphologic changes of metallic surfaces at the onset of ablation, starting from gentle ablation to the emergence of ablation craters. The evolution of both observed melting zones and of ablation craters therein are investigated in dependence of the ablation laser fluence for nanosecond ultraviolet laser pulses. Further, consequences of crater formation for cluster synthesis within the released atomic vapor are pointed out. PACS 52.38.Mf; 79.20.Ds; 65.40.De  相似文献   
45.
An expression for the ratio of the glass transition temperature to the melting temperature, T g/T m, was derived with allowance for fluctuations of the packing factor in the amorphous state. This relationship made it possible to describe the actual range of variation in T g/T m depending on a change in the packing factor in the crystalline state k o, cr. The proposed approach forms the basis for the method of determination of increments in the packing ratio k o, cr and formulation of the principles of selection of experimental data for calculations. The glass transition temperatures in polyethylene depending on the type of unit cell were calculated.  相似文献   
46.
The definition of the characteristic frequencies of zeroes and changes of sign for solutions is given. It is equal to the upper medium (with respect to the time half-axis) of their number on the half-interval of length π. We also define the main frequencies for a linear homogeneous equation of order n. These main frequencies for an equation with constant coefficients coincide with the absolute values of the imaginary parts of the roots of the corresponding characteristic polynomial. It is proved that for the second-order equation the main frequencies are the same for all solutions and that they are stable with respect to uniformly small and infinitely small perturbations of the coefficients. For the third-order equation they can be different, and for any of the main frequencies an example of nonstability is given. __________ Translated from Trudy Seminara imeni I. G. Petrovskogo, No. 25, pp. 249–294, 2005.  相似文献   
47.
In this paper, a two-dimensional finite volume unstructured mesh method (FVUM) based on a triangular background interpolation mesh is developed for analysing the evolution of the saltwater intrusion into single and multiple coastal aquifer systems. The model formulation consists of a ground-water flow equation and a salt transport equation. These coupled and non-linear partial differential equations are transformed by FVUM into a system of differential/algebraic equations, which is solved using backward differentiation formulas of order one through five. Simulation results are compared with previously published solutions where good agreement is observed.  相似文献   
48.
Optics and Spectroscopy - The relationship between the parameters of quadripoles (mirrors, for example) ensuring the fulfillment of the energy conservation law are considered. Apart from the...  相似文献   
49.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 3, pp. 438–444, March, 1991.  相似文献   
50.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 4, pp. 535–540, October, 1991.  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