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   630178篇
  免费   5067篇
  国内免费   1635篇
化学   319442篇
晶体学   9245篇
力学   32044篇
综合类   27篇
数学   83008篇
物理学   193114篇
  2021年   5843篇
  2020年   6293篇
  2019年   7180篇
  2018年   9690篇
  2017年   9816篇
  2016年   13578篇
  2015年   7290篇
  2014年   12339篇
  2013年   27955篇
  2012年   21644篇
  2011年   25771篇
  2010年   19430篇
  2009年   19381篇
  2008年   24382篇
  2007年   24138篇
  2006年   21910篇
  2005年   19576篇
  2004年   18347篇
  2003年   16533篇
  2002年   16351篇
  2001年   17521篇
  2000年   13475篇
  1999年   10447篇
  1998年   8981篇
  1997年   8901篇
  1996年   8336篇
  1995年   7470篇
  1994年   7551篇
  1993年   7272篇
  1992年   7833篇
  1991年   8224篇
  1990年   7946篇
  1989年   7857篇
  1988年   7651篇
  1987年   7386篇
  1986年   7110篇
  1985年   9111篇
  1984年   9527篇
  1983年   7960篇
  1982年   8189篇
  1981年   7750篇
  1980年   7325篇
  1979年   7958篇
  1978年   8186篇
  1977年   8164篇
  1976年   8141篇
  1975年   7776篇
  1974年   7570篇
  1973年   7932篇
  1972年   5833篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
An estimate of the remainder in the spectral decomposition of the generalized ζ function is given, which is more precise than the known ones. This paper is a continuation of a previous paper published in one of the preceding issues. Bibliography: 1 title. __________ Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 330, 2006, pp. 77–92.  相似文献   
962.
A theorem on the existence of a G-representation and a differential-geometric criterion of the kinematic integrability for nonlinear differential equations from the Λ2-G-classes is proved. Examples of zero-curvature representations and metrics for some equations of mathematical physics are presented. __________ Translated from Fundamental’naya i Prikladnaya Matematika (Fundamental and Applied Mathematics), Vol. 11, No. 1, Geometry, 2005.  相似文献   
963.
964.
It is suggested to produce metal-carbon composite coatings by magnetron sputtering of mosaic cathodes, which are Group IV, V, and VI metals. The mosaic structure of the cathode elements are computer-optimized for each of the metals. Reflection electron diffraction studies show that the coatings have the amorphous or nanocrystalline structures, which are thermally stable. The coatings offer specific physical properties, in particular, low friction factor and high hardness.  相似文献   
965.
In this context, we introduce and investigate the properties of the nonlinear negative binomial state (the state which interpolates between the nonlinear coherent and the number states). Mainly we concentrate on the statistical properties for such state where we have discussed two different cases of squeezing phenomenon. The first case is the normal squeezing while the second is the amplitude squared squeezing, further the second order correlation function is also considered. Our discussion have been extended to include the quasi-probability distribution functions (W-Wigner and Q-functions). The quadrature distribution and the phase properties in Pegg-Barnett formalism besides the phase variances are considered. Examination of the resonance fluorescence against the present state is given (single atom and thermodynamic limit). It has been shown that the atomic inversion is sensitive to any variation in the nonlinear negative binomial number m.  相似文献   
966.
The aim of this paper is to highlight the added value of the generalized Gouy phase shift introduced by Siegman. Although suited for optical systems study, including those more complex than free space, we note that it did not meet the use that it deserves so far. The analysis of the whole of the ideas and analytical approaches associated to the important concept of the Gouy phase proves its effectiveness.

Usually, the resonance condition is systematically built on the basis of the equivalent empty cavity. Unfortunately, this approach does not cover some of the useful parameters of the real resonator. By means of the generalized Gouy phase and the self-consistent complex parameter q, we derive here a new approach for the calculation of the resonance condition for the real cavity. Moreover, the use of the generalized Gouy phase clearly simplifies the study of resonators, while making it possible to avoid the use of the Huygens’ Fresnel integral.  相似文献   

967.
(Na, K)NbO3 crystals with a perovskite structure and a KNbO3 content up to 40 mol % were grown from flux with the use of the solvent NaBO2. The dielectric measurements of the crystals grown revealed phase transitions that had never been observed before in ceramic samples.  相似文献   
968.
969.
The Meyerhoff Program is an intensive, multicomponent program focused on enhancing the success of talented African-American students in science and engineering at a predominantly white, medium-sized university. The program components, taken together, address the four primary factors emphasized in the research literature as limiting minority student performance and persistence in science: knowledge and skills, motivation and support, monitoring and advising, and academic and social integration. Outcome analyses indicated that the first three cohorts of Meyerhoff students (total N=69) achieved an overall GPA (mean=3.5) significantly greater than that of an African-American historical comparison sample (mean=2.8) of comparably talented science students at the university. This difference was even greater for first year science GPA (means of 3.4 and 2.4, respectively), and in specific science and mathematics courses. Observational and questionnaire data indicated that the Meyerhoff program study groups, peerbased community, financial scholarships, summer bridge program and staff appear to be especially important contributors to student success. Implications of the findings for enhancing the success of African-American and other underrepresented populations in science are discussed.  相似文献   
970.
A metatheory of Nudel'man outlined in [1] is proved inconsistent. The groundwork for the proof is the method of arithmetization of metamathematics.Translated fromAlgebra i Logika, Vol. 34, No. 1, pp. 41–43, January–February, 1995.  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