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   731篇
  免费   19篇
化学   542篇
晶体学   9篇
力学   1篇
综合类   2篇
数学   67篇
物理学   129篇
  2023年   3篇
  2020年   7篇
  2019年   5篇
  2018年   5篇
  2017年   3篇
  2016年   7篇
  2015年   10篇
  2014年   12篇
  2013年   33篇
  2012年   26篇
  2011年   41篇
  2010年   19篇
  2009年   23篇
  2008年   43篇
  2007年   37篇
  2006年   32篇
  2005年   47篇
  2004年   41篇
  2003年   40篇
  2002年   25篇
  2001年   14篇
  2000年   11篇
  1999年   6篇
  1998年   11篇
  1997年   15篇
  1996年   11篇
  1995年   11篇
  1994年   15篇
  1993年   7篇
  1992年   5篇
  1991年   4篇
  1990年   8篇
  1989年   6篇
  1988年   7篇
  1987年   7篇
  1986年   5篇
  1985年   4篇
  1984年   13篇
  1983年   6篇
  1982年   15篇
  1981年   10篇
  1980年   12篇
  1979年   12篇
  1978年   14篇
  1977年   8篇
  1976年   19篇
  1975年   6篇
  1974年   7篇
  1973年   10篇
  1971年   2篇
排序方式: 共有750条查询结果,搜索用时 31 毫秒
101.
102.
A novel strategy for the synthesis of layered organosilica is demonstrated. The ionic interaction between the anionic group of a surfactant (sodium dodecyl sulfate) and the cationic organic group of an organosilane (3-aminopropyltrimethoxysilane, ATMS) under acidic conditions was utilized to create a layered organosilica at room temperature. The inorganic part of the organosilica layer was an Si-O hexagonal sheet, and organofunctional groups were alternately arranged on both sides of the sheet. The layered structure of the ATMS organosilica was retained after the removal of the surfactant with chloride anion. The properties of the layered ATMS organosilica were investigated. The layered ATMS-Cl organosilica is stable and possesses a definite layer structure in water or ethanol. Various kinds of anions can be intercalated in the interlayer space of the layered ATMS organosilicas and the layer was expanded dependent on the intercalated anions. The structure of the layered ATMS organosilica was well retained during the intercalation processes.  相似文献   
103.
The grafting of vinyl monomers by tri-n-butylborane to blood has been investigated. The infrared spectra indicated that the monomers were grafted onto blood components. The grafting seems to occur onto blood proteins, mainly onto hemoglobin. The presence of water was essential to the grafting. The hydrolysis of the graft suggests that basic amino acids in the blood proteins, such as lysine and histidine, play an important role in the grafting.  相似文献   
104.
The structural properties of microcrystalline silicon (μc-Si) are studied by Raman scattering. It is found that the intensity of each Raman band closely correlates with the absorption coefficient in the interband region and that the Raman band at ca. 150 cm?1 is a sensitive probe to randomness of Si-Si bonding structure in μc-Si.  相似文献   
105.
We show theoretically that the effect of self-induced transparency can be supported by the two-photon transition in the system of three-level atoms. The distortionless propagation of the radiation wave is composed of a train of pulses which is described by a trigonometric function, and in one limit, it approaches to a single pulse with lorentzian form for the radiation intensity.  相似文献   
106.
Total synthesis of codonocarpine (5) and its regio-isomer (15) utilizing a new cyclization procedure is described.  相似文献   
107.
Let L be a positive Z-lattice with level N = cd, (c, d) = 1. Then the Fourier expansion at cusp 1d of the theta function associated to L is a theta function associated to L1, where a lattice L1 is defined by ZpL1 = ZpL for p?c, ZpL1 = the dual of ZpL for p | c.  相似文献   
108.
109.
We introduce the concept of fusion algebras at algebraic level, as a purely algebraic concept for the fusion algebras which appear in conformal field theory in mathematical physics. We first discuss the connection between fusion algebras at algebraic level and character algebras, a purely algebraic concept for Bose-Mesner algebras of association schemes. Through this correspondence, we establish the condition when the matrix S of a fusion algebra at algebraic level is unitary or symmetric. We construct integral fusion algebras at algebraic level, from association schemes, in particular from group association schemes, whose matrix S is unitary and symmetric. Finally, we consider whether the modular invariance property is satisfied or not, namely whether there exists a diagonal matrix T satisfying the condition (ST)3 = S 2. We prove that this property does not hold for some integral fusion algebras at algebraic level coming from the group association scheme of certain groups of order 64, and we also prove that the (nonintegral) fusion algebra at algebraic level obtained from the Hamming association scheme H(d, q) has the modular invariance property.  相似文献   
110.
Serial optical interconnection is proposed for connections in a Torus asynchronous transfer mode switch. A cross-point switch was developed that operates at a bit rate of 20 Gbit/s. The switching operation was successfully performed using cascaded cross-point switches through an optical interconnection configuration consisting of commercial optoelectronics devices. The measured switching rate was 10 Gbit/s, and it was limited by the responses of the optoelectronics devices.  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