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   553453篇
  免费   4744篇
  国内免费   1497篇
化学   285485篇
晶体学   7751篇
力学   26577篇
综合类   18篇
数学   72905篇
物理学   166958篇
  2021年   5261篇
  2020年   5763篇
  2019年   6484篇
  2018年   8659篇
  2017年   8821篇
  2016年   12150篇
  2015年   6730篇
  2014年   11016篇
  2013年   24748篇
  2012年   19517篇
  2011年   23220篇
  2010年   17240篇
  2009年   16994篇
  2008年   21900篇
  2007年   21762篇
  2006年   19925篇
  2005年   17795篇
  2004年   16594篇
  2003年   14898篇
  2002年   14743篇
  2001年   15131篇
  2000年   11712篇
  1999年   9089篇
  1998年   7939篇
  1997年   7855篇
  1996年   7278篇
  1995年   6562篇
  1994年   6611篇
  1993年   6333篇
  1992年   6652篇
  1991年   7154篇
  1990年   6833篇
  1989年   6741篇
  1988年   6561篇
  1987年   6334篇
  1986年   6093篇
  1985年   7735篇
  1984年   8106篇
  1983年   6817篇
  1982年   7130篇
  1981年   6612篇
  1980年   6314篇
  1979年   6751篇
  1978年   7016篇
  1977年   6887篇
  1976年   6800篇
  1975年   6484篇
  1974年   6315篇
  1973年   6580篇
  1972年   4812篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
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   
12.
A new solvent-free sample preparation method using silver trifluoroacetate (AgTFA) was developed for the analysis of low molecular weight paraffins and microcrystalline waxes by laser desorption/ionization time-of-flight mass spectrometry (LDI-TOFMS). Experiments show that spectral quality can be enhanced by dispersing AgTFA directly in liquid paraffins without the use of additional solvents. This preparation mixture is applied directly to the MALDI probe. Solid waxes could be examined by melting prior to analysis. The method also provides sufficiently reproducible spectra that peak area ratios between mono- and bicyclic alkane peaks indicated variations in the cycloalkane content of paraffin samples. Dehydrogenation of hydrocarbons observed during the desorption/ionization process was studied by analysis of alkane standards.  相似文献   
13.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 5, pp. 815–819, May, 1991.  相似文献   
14.
A multidimensional generalization of the Reissner-Nordström solution of general relativity is obtained for the case of n Ricci-flat internal spaces. A two-parameter family of black-hole solutions for an arbitrary dimensionality D is selected. Nontrivial black holes with D > 4 are shown to exist only with a nonzero electric charge. Observational consequences are discussed, in particular, a violation of Coulomb's law.  相似文献   
15.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 3, pp. 438–444, March, 1991.  相似文献   
16.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 4, pp. 535–540, October, 1991.  相似文献   
17.
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   
18.
Time‐dependent differential equations can be solved using the concept of method of lines (MOL) together with the boundary element (BE) representation for the spatial linear part of the equation. The BE method alleviates the need for spatial discretization and casts the problem in an integral format. Hence errors associated with the numerical approximation of the spatial derivatives are totally eliminated. An element level local cubic approximation is used for the variable at each time step to facilitate the time marching and the nonlinear terms are represented in a semi‐implicit manner by a local linearization at each time step. The accuracy of the method has been illustrated on a number of test problems of engineering significance. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2006  相似文献   
19.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 6, pp. 970–975, June, 1991.  相似文献   
20.
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