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   675528篇
  免费   5583篇
  国内免费   1788篇
化学   352091篇
晶体学   10198篇
力学   32163篇
综合类   19篇
数学   83451篇
物理学   204977篇
  2021年   5656篇
  2020年   6189篇
  2019年   6973篇
  2018年   9233篇
  2017年   9353篇
  2016年   13161篇
  2015年   7378篇
  2014年   12134篇
  2013年   29178篇
  2012年   22029篇
  2011年   26464篇
  2010年   19606篇
  2009年   19402篇
  2008年   24835篇
  2007年   24818篇
  2006年   22750篇
  2005年   20365篇
  2004年   18981篇
  2003年   17060篇
  2002年   16876篇
  2001年   18679篇
  2000年   14502篇
  1999年   11269篇
  1998年   9548篇
  1997年   9494篇
  1996年   8947篇
  1995年   8092篇
  1994年   8013篇
  1993年   7748篇
  1992年   8487篇
  1991年   8858篇
  1990年   8547篇
  1989年   8517篇
  1988年   8264篇
  1987年   8148篇
  1986年   7741篇
  1985年   9910篇
  1984年   10313篇
  1983年   8669篇
  1982年   9051篇
  1981年   8533篇
  1980年   8176篇
  1979年   8783篇
  1978年   9254篇
  1977年   9061篇
  1976年   8940篇
  1975年   8528篇
  1974年   8336篇
  1973年   8616篇
  1972年   6211篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
12.
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   
13.
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   
14.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 5, pp. 815–819, May, 1991.  相似文献   
15.
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   
16.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 3, pp. 438–444, March, 1991.  相似文献   
17.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 4, pp. 535–540, October, 1991.  相似文献   
18.
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   
19.
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   
20.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 6, pp. 970–975, June, 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