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   370666篇
  免费   3225篇
  国内免费   1040篇
化学   199709篇
晶体学   5810篇
力学   16198篇
综合类   13篇
数学   40635篇
物理学   112566篇
  2018年   3657篇
  2017年   3592篇
  2016年   5573篇
  2015年   3528篇
  2014年   5412篇
  2013年   14778篇
  2012年   10984篇
  2011年   13534篇
  2010年   9372篇
  2009年   9005篇
  2008年   12510篇
  2007年   12755篇
  2006年   12201篇
  2005年   11258篇
  2004年   10257篇
  2003年   9301篇
  2002年   9151篇
  2001年   10094篇
  2000年   7786篇
  1999年   6106篇
  1998年   5409篇
  1997年   5375篇
  1996年   5061篇
  1995年   4756篇
  1994年   4735篇
  1993年   4449篇
  1992年   5083篇
  1991年   5079篇
  1990年   4948篇
  1989年   4818篇
  1988年   4908篇
  1987年   4823篇
  1986年   4567篇
  1985年   6103篇
  1984年   6481篇
  1983年   5407篇
  1982年   5792篇
  1981年   5560篇
  1980年   5583篇
  1979年   5567篇
  1978年   5970篇
  1977年   5815篇
  1976年   5930篇
  1975年   5532篇
  1974年   5445篇
  1973年   5824篇
  1972年   3961篇
  1971年   3222篇
  1968年   3013篇
  1967年   3111篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
162.
We construct models for the level by level equivalence between strong compactness and supercompactness in which for κ the least supercompact cardinal and δκ any cardinal which is either a strong cardinal or a measurable limit of strong cardinals, 2δ > δ + and δ is < 2δ supercompact. In these models, the structure of the class of supercompact cardinals can be arbitrary, and the size of the power set of κ can essentially be made as large as desired. This extends and generalizes [5, Theorem 2] and [4, Theorem 4]. We also sketch how our techniques can be used to establish a weak indestructibility result. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
163.
Effect of errors of different origin on the efficiency of sound absorption by a local active absorber is investigated. Degradation of the efficiency of absorption because of the errors is shown to be minimal in the case when the controller does not detect the field of the secondary radiator. Estimates of admissible errors are presented. Several active absorber configurations in which the radiator does not affect the receiver are considered.  相似文献   
164.
The effect of crack tip sharpness on crack propagation in vulcanized rubbers has been studied. For very sharp cracks, tearing is found to occur on a small scale at very low energies not far above the threshold required for the onset of mechanical crack growth. The “small-scale” tearing energies show relatively little variation for rubbers that differ widely in tear strength as normally measured. Thus the latter property appears to be strongly influenced by variations in the ability of rubbers to promote tip blunting. The small-scale tear behavior is of relevance to other fracture phenomena, including cutting by sharp objects and tensile failure. Natural variations in tip sharpness occur during cyclic or time-dependent mechanical crack growth and influence the form of the crack growth characteristics.  相似文献   
165.
In this article we investigate some integral functional inequalities of Bellman–Bihari type for piecewise-continuous functions with some fixed points of discontinuity. We also prove a new analogy and generalization of results which were obtained by Bellman and Bihari to integro-sum inequalities with delay and discontinuities that do not belong to Lipschitz’s type.  相似文献   
166.
167.
168.
The QQ mass spectrometer is shown to be applicable to ion structure determination via collision-induced dissociations of mass-selected ions. The instrument can be scanned so as to record the products of dissociation as well as those of ion—molecule association reactions. The dissociations correspond to those observed at high kinetic energy in mass-analyzed ion kinetic energy spectrometers and the association reactions show parallels with reactions seen in ion cyclotron resonance spectroscopy and in high-pressure mass spectrometry  相似文献   
169.
170.
Binding energy spectra of the valence electrons of the open shell molecule NO have been obtained up to 55 eV at azimuthal angles of 0° and 7° using binary (e, 2e) spectroscopy at an impact energy of 1200 eV. The momentum distribution has been obtained for the least tightly bound (unpaired) electron, removal of which leads to formation of the X 1Σ+ ground state of NO+. Momentum distributions have also been measured at 21.0 and 40.5 eV. The measured momentum distributions are compared with several literature wavefunctions of varying complexity. They are found to be in excellent agreement with those calculated using the natural spin orbital wavefunctions of Kouba and Ohrn.  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