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   128024篇
  免费   1748篇
  国内免费   473篇
化学   70940篇
晶体学   2068篇
力学   5005篇
综合类   5篇
数学   12363篇
物理学   39864篇
  2016年   1412篇
  2015年   1084篇
  2014年   1471篇
  2013年   4990篇
  2012年   3655篇
  2011年   4675篇
  2010年   2904篇
  2009年   2673篇
  2008年   4143篇
  2007年   4182篇
  2006年   4204篇
  2005年   4121篇
  2004年   3630篇
  2003年   3268篇
  2002年   3185篇
  2001年   3622篇
  2000年   2749篇
  1999年   2232篇
  1998年   1901篇
  1997年   1886篇
  1996年   1823篇
  1995年   1793篇
  1994年   1562篇
  1993年   1549篇
  1992年   1785篇
  1991年   1761篇
  1990年   1682篇
  1989年   1691篇
  1988年   1689篇
  1987年   1680篇
  1986年   1594篇
  1985年   2152篇
  1984年   2269篇
  1983年   1891篇
  1982年   2218篇
  1981年   2038篇
  1980年   2081篇
  1979年   2064篇
  1978年   2192篇
  1977年   2099篇
  1976年   2120篇
  1975年   2060篇
  1974年   1906篇
  1973年   2105篇
  1972年   1283篇
  1971年   977篇
  1970年   912篇
  1969年   923篇
  1968年   1052篇
  1967年   1101篇
排序方式: 共有10000条查询结果,搜索用时 671 毫秒
291.
We consider the support problem of Erdös in the context of l-adic representations of the absolute Galois group of a number field. Main applications of the results of the paper concern Galois cohomology of the Tate module of abelian varieties with real and complex multiplications, the algebraic K-theory groups of number fields and the integral homology of the general linear group of rings of integers. We answer the question of Corrales-Rodrigáñez and Schoof concerning the support problem for higher dimensional abelian varieties.  相似文献   
292.
293.
294.
Cao  H. P.  Chen  G.  Grechkoseeva  M. A.  Mazurov  V. D.  Shi  W. J.  Vasil'ev  A. V. 《Siberian Mathematical Journal》2004,45(6):1031-1035
The spectrum of a finite group is the set of its element orders. A finite group G is said to be recognizable by spectrum, if every finite group with the same spectrum as G is isomorphic to G. The purpose of the paper is to prove that for every natural m the finite simple Chevalley group F 4(2 m ) is recognizable by spectrum.  相似文献   
295.
By the application of microwave technology, a general protocol has been developed for the rapid synthesis of diverse 3,5,6-trisubstituted 1,2,4-triazines in excellent yield and purity, including many previously unknown 3-heterocyclic-1,2,4-triazines.  相似文献   
296.
We propose a new approach towards proving that the fixed point property for ordered sets is preserved by products. This approach uses a characterization of fixed points in products via isotone relations. First explorations of classes of isotone relations are presented. These first explorations give us hope that this approach could lead to advances on the Product Problem.  相似文献   
297.
The Li oxides species formed on Li over-deposited V2O5 thin film surfaces have been studied by using X-ray and UV induced photoelectron spectroscopy (XPS and UPS). The photoelectron spectroscopic data show that the Li over-deposited V2O5 system itself is not stable. Further chemical decomposition reactions are taken place even under UHV conditions and lead to form Li2O and Li2O2 compounds on the surface. The formation of Li2O2 causes to arise an emission line at about 11.3 eV in the valence band spectra.  相似文献   
298.
In this paper, we have developed a load-bearing outer skin for antennas, which is termed a composite smart structure (CSS). The CSS is a multilayer composite sandwich structure in which antenna layers are inserted. A direct-feed stacked patch antenna is considered. A design procedure including the structure design, material selection, and design of antenna elements in order to obtain high electric and mechanical performances is presented. An optimized honeycomb thickness is selected for efficient radiation and impedance characteristics. High gain conditions can be obtained by placing the outer facesheet in the resonance position, which is at about a half wavelength distance from the ground plane. The measured electrical performances show that the CSS has a great bandwidth (over 10%) and a higher gain than an antenna without a facesheet and has excellent mechanical performances, owing to the composite laminates and honeycomb cores. The CSS concept can be extended to give a useful guide for manufacturers of structural body panels and for antenna designers.  相似文献   
299.
We prove a Tauberian theorem for Walsh series of two variables, and use it to obtain several results about uniqueness of Cesàro summable double Walsh series. Namely, we show that up to sets of measure zero, Cesàro summability of double Walsh series is the same as convergence of the square dyadic partial sums and, under a suitable growth condition, that uniqueness holds for Cesàro summable double Walsh series.  相似文献   
300.
Usually, numerical self-consistent calculations predict a much larger intrinsic bistability region than actually is measured in resonant tunneling diodes (RTDs). In addition, numerical calculations have shown that scattering in the well reduces bistability. We used a unified treatment of current flowing from continuum states and emitter quasi-bound states to show numerically and analytically that not only the scattering in the quantum well but also the scattering in the emitter reduces bistability. Moreover, within the Hartree approximation, bistability occurs by tunneling resonantly between emitter quasi-bound state and well quasi-bound state as a pitchfork bifurcation.  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