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   640463篇
  免费   8500篇
  国内免费   3984篇
化学   332611篇
晶体学   9266篇
力学   31779篇
综合类   216篇
数学   80772篇
物理学   198303篇
  2021年   6394篇
  2020年   6908篇
  2019年   7652篇
  2018年   9847篇
  2017年   9928篇
  2016年   13948篇
  2015年   8126篇
  2014年   12928篇
  2013年   28884篇
  2012年   23025篇
  2011年   27246篇
  2010年   20129篇
  2009年   20007篇
  2008年   25281篇
  2007年   24882篇
  2006年   23002篇
  2005年   20540篇
  2004年   18970篇
  2003年   17054篇
  2002年   16764篇
  2001年   18693篇
  2000年   14335篇
  1999年   11178篇
  1998年   9314篇
  1997年   9199篇
  1996年   8625篇
  1995年   7825篇
  1994年   7793篇
  1993年   7351篇
  1992年   8110篇
  1991年   8548篇
  1990年   8153篇
  1989年   7964篇
  1988年   7743篇
  1987年   7596篇
  1986年   7156篇
  1985年   9103篇
  1984年   9404篇
  1983年   7810篇
  1982年   8121篇
  1981年   7490篇
  1980年   7223篇
  1979年   7839篇
  1978年   8163篇
  1977年   8000篇
  1976年   7933篇
  1975年   7575篇
  1974年   7365篇
  1973年   7658篇
  1972年   5522篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Summary The main purpose of this paper is to introduce the concepts of η-sets, ηζ-sets,η-continuity and ηζ-continuity and to obtain a decomposition of continuity.  相似文献   
52.
The paper mentioned above is a contribution of the authors to Volume 18 (2002) of this journal, see . Recently, J. Domsta pointed out to us that the proof of Theorem 4.2 in that paper contains an error. The purpose of this addendum is to present a correct argument for it.  相似文献   
53.
54.
The interferometric intensity patterns from a 2D shearing interferometer are shown and discussed. The intensity patterns can be obtained in two different approaches incorporating differential and extended wavefront controlled displacements. The reliable directional sensitivity of this interferometer allows the optimization of the measurement parameters to estimate the wavefront of the intensity patterns by regularization techniques.  相似文献   
55.
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   
56.
A numerical procedure, with an exact strain-displacement relationship of twisted and curved cylindrical panels having variable thickness derived by considering the Green strain tensor on general shell theory, is presented using the principle of virtual work and the Rayleigh-Ritz method with algebraic polynomials as in-plane and transverse displacement functions. The accuracy and applicability of the procedure are verified by comparing the present results with previous experimental and theoretical results for several panels. The effects of variation ratio of thickness in chordwise and lengthwise directions, twist, and curvature both in two directions aforementioned on vibrations of cylindrical panels are studied in detail, and typical vibration mode shapes are plotted to demonstrate the effects.  相似文献   
57.
In this paper a new state called odd-excited binomial state (OEBS) is introduced. It interpolates between the odd number state and the odd-excited coherent state. We discuss some statistical properties, such as the Glauber second-order correlation function and squeezing phenomenon (normal and amplitude-squared squeezing) for this state. The quasiprobability distribution functions (Husimi Q-function and Wigner W-function) are also examined.  相似文献   
58.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 5, pp. 815–819, May, 1991.  相似文献   
59.
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   
60.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 3, pp. 438–444, March, 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