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   20621篇
  免费   154篇
  国内免费   91篇
化学   10454篇
晶体学   421篇
力学   605篇
综合类   7篇
数学   1753篇
物理学   7626篇
  2016年   245篇
  2015年   168篇
  2014年   269篇
  2013年   847篇
  2012年   579篇
  2011年   640篇
  2010年   462篇
  2009年   474篇
  2008年   625篇
  2007年   680篇
  2006年   637篇
  2005年   587篇
  2004年   502篇
  2003年   473篇
  2002年   470篇
  2001年   694篇
  2000年   516篇
  1999年   434篇
  1998年   351篇
  1997年   333篇
  1996年   304篇
  1995年   380篇
  1994年   350篇
  1993年   322篇
  1992年   349篇
  1991年   392篇
  1990年   365篇
  1989年   365篇
  1988年   338篇
  1987年   335篇
  1986年   333篇
  1985年   409篇
  1984年   426篇
  1983年   318篇
  1982年   330篇
  1981年   352篇
  1980年   325篇
  1979年   336篇
  1978年   335篇
  1977年   317篇
  1976年   333篇
  1975年   291篇
  1974年   289篇
  1973年   303篇
  1972年   185篇
  1971年   158篇
  1969年   159篇
  1968年   189篇
  1967年   334篇
  1966年   284篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
In this paper we prove that iff ∈ C([-π,π]2) and the function f is bounded partial p-variation for some p ∈ [1, ∞), then the double trigonometric Fourier series of a function f is uniformly (C;-α,-β) summable (α β< 1/p,α,β> 0) in the sense of Pringsheim. If α β≥ 1/p, then there exists a continuous function f0 of bounded partial double trigonometric Fourier series of fo diverge over cubes.  相似文献   
93.
This paper studies the problem of uniformly dissipative solutions of somefifth order non-linear differential equations by the use of frequency domaintechnique. We use the generalized theorem of Yacubovich on dissipativity toobtain some new sufficient conditions of the existence of solutions that aredissipative for (1.1) and (1.2).  相似文献   
94.
The effect of entrance channel on decrease of the complete fusion cross sections and on the yield of reaction products are associated with the quasifission which depends on the mass asymmetry and shell structure of colliding nuclei. In reactions of massive projectile and target nuclei, the competition between complete fusion and quasifission appears at the stage of compound nucleus formation, in addition to the increase of the fission probability. It is shown that the yield of quasifission products may be symmetric or asymmetric in dependence on peculiarities of shell structure of reaction fragments. Marima of mass or charge distributions are connected with the peculiarities of shell structure of reaction fragments.  相似文献   
95.
The perovskite-like compounds ACu3Ru4O12 (A=Na, Ca, Sr, La, Nd) are studied by means of density functional theory based electronic structure calculations using the augmented spherical wave (ASW) method. The electronic properties are strongly influenced by covalent-type bonding between transition metal d and oxygen p states. The characteristic tilting of the RuO6 octahedra arises mainly from the Cu–O bonding, allowing for optimal bond lengths between these two atoms. Our results provide a deeper understanding of octahedral tilting as a universal mechanism, applicable to a large variety of multinary compounds.  相似文献   
96.
A novel liquid scintillator system using metal β-diketonate chemistry based on loadings of indium, a target of current interest in low energy solar neutrino detection, is developed. The optical absorption, fluorescence and scintillation properties for this new system are described. The scintillation light output as found from the irradiation by low energy gamma-rays is presented. Notable light yields are found.  相似文献   
97.
98.
99.
Amorphous ribbons of Mg-Y-TM-[Ag] (TM: Cu, Ni), prepared by melt spinning, were subjected to electrochemical investigations. Oxide layers formed anodically under potentiostatic control in different electrolytes were investigated by AES and sputter depth profiling. Problems and specific features of characterization of the composition of oxide layers and amorphous ternary or quaternary Mg-based alloys have been investigated. In the alloys the Mg(KL(23)L(23)) peak exhibits a different shape compared to that in the pure element. Analysis of the peak of elastically scattered electrons proved the absence of plasmon loss features, characteristic of pure Mg, in the alloy. A different loss feature emerges in Mg(KL(23)L(23)) and Cu(L(23)VV). The system Mg-Y-TM-[Ag] suffers preferential sputtering. Depletion of Mg and enrichment of TM and Y are found. This is attributed mainly to the preferential sputtering of Mg. Thickness and composition of the formed oxide layer depend on the electrochemical treatment. After removing the oxide by sputtering the concentration of the underlying alloy was found to be affected by the treatment.  相似文献   
100.
A novel preference for planar tetracoordination was observed over the conventional tetrahedral arrangement in a new series of C5H2, C5H4, C5H41+/2+ and related compounds. The stability of these molecules is assessed with the ring-opening barriers, HOMO-LUMO gap, singlet-triplet energy differences and nucleus independent chemical shift values.  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