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   1942篇
  免费   71篇
  国内免费   6篇
化学   1285篇
晶体学   11篇
力学   70篇
综合类   2篇
数学   210篇
物理学   441篇
  2023年   12篇
  2022年   21篇
  2021年   38篇
  2020年   35篇
  2019年   19篇
  2018年   28篇
  2017年   16篇
  2016年   50篇
  2015年   44篇
  2014年   57篇
  2013年   100篇
  2012年   135篇
  2011年   131篇
  2010年   79篇
  2009年   85篇
  2008年   132篇
  2007年   126篇
  2006年   113篇
  2005年   96篇
  2004年   71篇
  2003年   72篇
  2002年   83篇
  2001年   30篇
  2000年   43篇
  1999年   19篇
  1998年   20篇
  1997年   25篇
  1996年   30篇
  1995年   16篇
  1994年   13篇
  1993年   21篇
  1992年   23篇
  1991年   13篇
  1990年   18篇
  1989年   19篇
  1988年   8篇
  1986年   12篇
  1985年   15篇
  1984年   12篇
  1983年   10篇
  1982年   9篇
  1981年   11篇
  1980年   6篇
  1979年   14篇
  1978年   7篇
  1977年   13篇
  1976年   10篇
  1974年   11篇
  1973年   6篇
  1972年   7篇
排序方式: 共有2019条查询结果,搜索用时 15 毫秒
141.
142.
143.
144.
We present a primitive recursive programinf_with_lists computing the minimum of two natural numbersn andp (written in unary notation) and using primitive recursion on lists. This program has at first sight the required property of visiting simultaneously its inputs, so it is a counterexample to a theorem showing that such a program cannot be written in the language of primitive recursion on natural numbers, in the more general framework of primitive recursion on term algebras. However, its complexity is at leastinf(n,p)2 so it does not implement the algorithm we have in mind to computeinf(n,p).  相似文献   
145.
The complexes R2SnCl2·(H2glygly), (H2glygly = glycylglycine) (R = Me, Bun, Octn, Ph) and RSnCl3·(H2glygly)  相似文献   
146.
147.
Calculations of ESCA chemical shifts, using Jolly's equivalent core approximation and the MINDO/3 semi-empirical SCF MO method, have given results in reasonable agreement with experiment.  相似文献   
148.
Zhang DY  Justis N  Lo YH 《Optics letters》2004,29(24):2855-2857
An integrated fluidic adaptive zoom lens is demonstrated for what is believed to be the first time. A zoom lens was fabricated using an UV lithographic-galvanic-like process involving soft lithography and wafer bonding. The zooming capability of such a lens was achieved by varying the focal length instead of the distance between the lenses. A zoom ratio of greater than 2 was obtained for devices that are 8 mm thick and have a 20-mm lens diameter. Including the 30-mm image distance, the total physical length of the fluidic zoom lens was less than 43 mm. More-compact systems with a higher zoom ratio can be obtained by reduction of the aperture size.  相似文献   
149.
Using a series of Ir(I) and Rh(I) ketene complexes, conclusions about the structure and bonding of complexes of the fundamentally important ketene ligand class are reached. In a unique comparison of X-ray structures of the same metal fragment to ketenes in both the eta(2)-(C,C) and the eta(2)-(C,O) binding mode, the Ir-Cl bond distances in complexes of trans-Cl(Ir)[P(i-Pr)(3)](2) to phenylketene [4, eta(2)-(C,C)] and diphenylketene [2a, eta(2)-(C,O)] are 2.371(3) and 2.285(2) A, respectively. This would be consistent with greater trans influence of a ketene ligand bound to a metal through its C=C bond than one connected by its C=O bond. Back-bonding of Ir(I) and Rh(I) to diphenylketene was assessed using trans-Cl(M)[P(i-Pr)(3)](2)[eta(2)-(C,O)-diphenylketene] (2a and 2d). Most bond lengths and angles are identical, but slightly greater back-bonding by Ir(I) is suggested by the somewhat greater deformation of the ketene C=C=O system [C-C-O angles are 136.6(4) and 138.9(4) in the Ir and Rh cases 2a and 2d, respectively]. Syntheses of new labeled ketenes Ph(2)C=(13)C=O and Ph(2)C=C=(18)O and their Ir(I) and Rh(I) complexes are reported, along with the generation of an Ir(I) complex of PhCH=(13)C=O. The effects of isotopic substitution on infrared absorption data for ketene complexes are presented for the first time. Preliminary normal coordinate mode analysis allowed definitive assignment of absorptions ascribed to the C-O stretching frequencies of coordinated ketenes, which are near the absorptions for aromatic ring systems commonly found as substituents on ketenes. For free diphenylketene and four of its complexes and a phenylketene complex characterized by X-ray diffraction, the magnitude of the (13)C-(13)C coupling between the two ketene carbons is correlated to carbon-carbon bond distance.  相似文献   
150.
Entangled two-photon generalized binomial states of the electromagnetic field in two separate cavities are considered. The nonlocal properties of this entangled field state are analyzed by studying the electric field correlations between the two cavities. A Bell’s inequality violation is obtained using an appropriate dichotomic cavity operator that is, in principle, measurable. The text was submitted by the authors in English.  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