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   889篇
  免费   42篇
  国内免费   6篇
化学   723篇
晶体学   8篇
力学   7篇
数学   54篇
物理学   145篇
  2023年   4篇
  2022年   8篇
  2021年   5篇
  2020年   16篇
  2019年   19篇
  2018年   9篇
  2017年   9篇
  2016年   17篇
  2015年   29篇
  2014年   25篇
  2013年   50篇
  2012年   49篇
  2011年   59篇
  2010年   31篇
  2009年   27篇
  2008年   61篇
  2007年   43篇
  2006年   54篇
  2005年   51篇
  2004年   45篇
  2003年   27篇
  2002年   26篇
  2001年   12篇
  2000年   12篇
  1999年   6篇
  1998年   9篇
  1997年   6篇
  1996年   9篇
  1995年   7篇
  1994年   5篇
  1993年   5篇
  1992年   5篇
  1991年   10篇
  1990年   11篇
  1989年   7篇
  1988年   8篇
  1987年   8篇
  1986年   10篇
  1985年   19篇
  1984年   11篇
  1983年   12篇
  1982年   15篇
  1981年   12篇
  1980年   13篇
  1979年   12篇
  1978年   6篇
  1977年   10篇
  1976年   10篇
  1975年   7篇
  1973年   4篇
排序方式: 共有937条查询结果,搜索用时 31 毫秒
61.
The pH dependencies of electrochemomechanical deformation (ECMD) including the cyclic voltammetry and the expansion ratio in conducting polymers, polyaniline (PANI), and poly(o-methoxyaniline) film were studied to elucidate the mechanisms. It was found that the ECMD is governed by the conformational change of polymer structure as well as the insertion of bulky ions in the manner of comparable magnitude. Expansion ratios >20% in the ECMD were demonstrated for the thickness direction of PANI film. The results suggest that the magnitude of ECMD can be improved by choosing the preparation method of films.  相似文献   
62.
Assuming naturalness that the quantum corrections to the mass should not exceed the order of the observed mass, we derive and apply model-independent bounds on the anomalous magnetic moments and electric dipole moments of leptons and quarks due to new physics.  相似文献   
63.
A nonlinear optical crystal YCa(4)O(BO(3))(3) (YCOB) is phase matchable for third-harmonic generation (THG) of a Nd:YAG laser by type I mixing between 1.064 and 0.532mum . By partial substitution of Gd for Y in YCOB, a solid solution Gd(x)Y(1-x)Ca(4)O(BO(3))(3) gradually changes the phase-matching angles of THG to (theta, ?)=(90( degrees ), 90 ( degrees )) . We present the properties of noncritically phase-matched THG in Gd(x) Y(1-x)Ca(4)O(BO(3))(3) (x=0.28) .  相似文献   
64.
(S)-Hexakis(4-(4'-(6-methyl)octyloxy)biphenoxy)cyclotriphosphazene (SMOCP) was synthesized in a search for new ferroelectric liquid crystalline compounds. We found an enantiotropic ferroelectric smectic C* phase between 419 and 441 K in SMOCP by using polarizing microscopy and DSC measurements. The spontaneous polarization was estimated to be -130.5 μCm-2 at 437.6 K, several times larger than that of DOBAMBC ((S)-2-methylbutyl 4-(4'-decyloxybenzylidene)aminocinnamate.  相似文献   
65.
We investigate the relation between the Lee-Yang circle theorem and the correlation inequalities. These results are general and independent of models. General properties of the partition functions which belong to the Lee-Yang class are given.  相似文献   
66.
67.
The selective deposition of a metal (tungsten) into ordered nanohole arrays of an anodic porous alumina membrane was performed using an electron-beam-induced deposition process. After deposition, the membrane was observed and analyzed using electron microscopy and energy-dispersive X-ray spectroscopy. It is shown that the deposition was preferentially conducted in the holes in the irradiated area of the electron beam. A calculation of the electron-beam intensity explains the reason for the preferential deposition in the holes. PACS 81.07.-b; 81.16.Rf; 61.46.+w  相似文献   
68.
It is known that an amphiphilic merocyanine dye, 3-carboxymethyl-5-[2-(3-octadecyl-2(3H)- benzothiazolylidene)ethylidene]-2-thioxo-4-thiazolidinone (DS) and its derivatives DSe and 6MeDS form J aggregates under the presence of metallic cations, although the dyes' static dipole moments must be favorable for H aggregates. A metal-free J aggregate of 6MeDS has been generated in its pure Langmuir films and transferred onto CaF2 substrates to investigate the molecular environment around the carboxylic group born by the dye. Combining visible and infrared spectroscopy, geometrical consideration based on ab initio calculations, and simulation of the excitation energy, a structural model of this J aggregate has been proposed. With this model, formation of intermolecular carboxyl-keto hydrogen bonds, which can compensate the electrostatic disadvantage of the J aggregate under the presence of water, has been suggested. As for another derivative of DS, DO, similar discussion has been made for its Mg2+ -containing J aggregate, which is found in this work. In addition, the proposed structural model can tell the cause of the difference in the tendency to J aggregate among 6MeDS, DSe, DS, and DO.  相似文献   
69.
We introduce the concept of -adic -basis as an extension of the concept of -basis. Let be a regular local ring of prime characteristic and a ring such that . Then we prove that is a regular local ring if and only if there exists an -adic -basis of and is Noetherian.

  相似文献   

70.
Photoinduced dissociation in the ultraviolet region has been investigated for Ag nF n-1 + cluster ions. Photodissociation spectrum of Ag2F+ in the energy of 3.8–5.6 eV exhibits several sharp bands corresponding to the transition to electronically excited states. In this dissociation, only the Ag2 + ion was observed as a fragment ion. Theoretical calculation indicates that the parent Ag2F+ ion has a linear Ag-F-Ag equilibrium geometries in the ground and excited states. Since conformational changes by excitation of bending vibration are necessary for the fragmentation of an F atom, this indicates that production of Ag2 + from Ag2F+ is a result of internal conversion and following conformational changes.  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