全文获取类型
收费全文 | 521篇 |
免费 | 66篇 |
国内免费 | 65篇 |
专业分类
化学 | 270篇 |
晶体学 | 4篇 |
力学 | 11篇 |
综合类 | 3篇 |
数学 | 53篇 |
物理学 | 151篇 |
无线电 | 160篇 |
出版年
2024年 | 1篇 |
2023年 | 13篇 |
2022年 | 16篇 |
2021年 | 18篇 |
2020年 | 18篇 |
2019年 | 27篇 |
2018年 | 17篇 |
2017年 | 14篇 |
2016年 | 24篇 |
2015年 | 19篇 |
2014年 | 32篇 |
2013年 | 26篇 |
2012年 | 43篇 |
2011年 | 40篇 |
2010年 | 28篇 |
2009年 | 30篇 |
2008年 | 34篇 |
2007年 | 22篇 |
2006年 | 29篇 |
2005年 | 38篇 |
2004年 | 17篇 |
2003年 | 19篇 |
2002年 | 17篇 |
2001年 | 14篇 |
2000年 | 8篇 |
1999年 | 16篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 11篇 |
1995年 | 11篇 |
1994年 | 11篇 |
1993年 | 9篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1986年 | 4篇 |
1985年 | 1篇 |
排序方式: 共有652条查询结果,搜索用时 3 毫秒
191.
192.
Single-wall carbon nanotubes (SWNTs) chemically assembled on gold substrates were employed as electrodes to investigate the charge transfer process between SWNTs and the underlying substrates. Cyclic voltammetry (CV) indicates that the assembled SWNTs allow electron communication between a gold electrode and the redox couple in solution, though the SWNTs are linked directly onto the insulating monolayer of 11-amino-n-undecanethiol (AUT) on the Au substrate. An electron transfer (ET) mechanism, which contains an electron tunneling process across the AUT monolayer, is proposed to explain the CV behavior of Au/AUT/SWNT electrodes. Electrochemical measurements show that the apparent electron tunneling resistance, which depends on the surface density of assembled SWNTs, has apparent effects similar to those of solution resistance on CV behavior . The theory of solution resistance is used to describe the apparent tunneling resistance. The experimental results of the dependence of ET parameter psi on the potential scan rate upsilon are in good agreement with the theoretical predictions. Kinetic studies of the chemical assembly of SWNTs by atomic force microscopic (AFM), electrochemical, and Raman spectroscopic methods reveal that two distinct assembly kinetics exist: a relatively fast step that is dominated by the surface reaction, and a successive slow step that is governed by bundle formation. 相似文献
193.
Adsorption, vibration, and diffusion of O atoms on Rh low-index and (711) stepped defective surfaces
Diao ZY Hao C Wang ZX Dong CC Pang XH 《The journal of physical chemistry. B》2005,109(25):12467-12473
The adsorption, vibration, and diffusion of O atoms on Rh(100), Rh(111), Rh(110), and Rh(711) surfaces were studied using the 5-parameter Morse potential (5-MP) of interaction between an adatom and a metal surface cluster. Our theoretical calculations provide information about adsorption sites, adsorption geometry, binding energy, and eigenvibration. Our results agreed very well with experimental results. Four major results follow. First, the theoretical calculation showed that on the Rh(100) surface the 4-fold hollow site is the only adsorption site. Second, on the O-Rh(111) system, the 3-fold hollow site is the stable adsorption site. Third, on the Rh(110) surface at low coverage, the O atom is adsorbed preferably on the pseudo-3-fold site, while with increasing coverage, the O atom is adsorbed not only on the pseudo-3-fold site but also on the long bridge site. Last, as for the Rh(711) stepped surface, the 3-fold site on the (111) step is metastable, whereas the 4-fold sites on the (100) terrace are stable, which enables the O atoms to diffuse easily from the 3-fold to the 4-fold site at low coverage. Therefore, the O atoms are adsorbed preferrably on the stable 4-fold sites of the (100) terrace and then later as coverage increases on the metastable 3-fold site of the (110) step. 相似文献
194.
用电容平面图研究金/十八硫醇单分子膜的自组装过程和缺陷情况 总被引:1,自引:0,他引:1
推导了电化学体系中理想极化电极、电化学极化电极的复数电容表达式。根据这些表达式分析了上述体系的电容平面图 (Capacitance Plane Plot,CPP) ,利用 CPP可以方便地监测体系的电容值。用电子元件组成了上述体系的等效电路 ,测定了交流阻抗谱 ,得到了 CPP与理论推导一致。研究了金 /十八硫醇自组装膜的 CPP,根据 CPP讨论了金 /硫醇膜的组装过程及缺陷和组装时间的关系。 相似文献
195.
离子色谱是目前分析离子型样品的成熟技术,其水相工作介质的特点相对于液相色谱更适合于生物样品的分析。毛细管离子色谱(CIC)由于其节省样品的特点在生物分析方面的优势更为明显。CIC大体上可分为开管型、填充柱型和整体柱型3种类型。本文以填充型CIC几大关键部件技术发展为主线,综述了近年来CIC的研究进展。 相似文献
196.
197.
The stability of hydrogen-bonded complexes, DMF–H
n
CCl4−n
(n = 1–3), has been investigated by several theoretical methods including the MP2 level of ab initio theory at various basis
sets from 6-31+G* to 6-311++G**. Two stable configurations (respectively a and b) were obtained for each complex with no imaginary frequencies. The minimum energy structure of these complexes has also been
analyzed by means of the atoms in molecule theory at MP2/6-311++G** level. It is found that C–H···O hydrogen bonding exists
in these systems and that the intensity of HB interaction gradually increases with successive chlorination. Computed results
indicate that these complexes automatically assemble into different stable configurations. For the complexes under consideration,
their stabilities can be mainly ascribed to the intermolecular HB interaction. The present work is helpful to clearly understand
the interaction mechanism of these complexes in theory. 相似文献
198.
Average life of oxygen vacancies of quartz in sediments is estimated by using the ESR (electron spin resonance) signals of E’ centers from the thermal activation technique. The experimental results show that the second-order kinetics equation is more applicable to the life estimation compared with the first order equation. The average life of oxygen vacancies of quartz from 4895 to 4908 deep sediments in the Tarim Basin is about 1018 a at 27°C. 相似文献
199.
C. -S. Jia P. Guo Y. -F. Diao L. -Z. Yi X. -J. Xie 《The European Physical Journal A - Hadrons and Nuclei》2007,34(1):41-48
By using the basic concepts of the supersymmetric quantum mechanics formalism and the function analysis method, we solve the
Dirac equation with vector and scalar potentials and obtain the bound-state solutions for the nuclei in the relativistic P?schl-Teller
potential. All of the analyses are prepared under the conditions of the exact spin symmetry and pseudospin symmetry. The exact
energy equation and corresponding two-component spinor wave functions for s -wave bound states are obtained analytically. 相似文献
200.
X. Dai Y. Diao Q. Gu D. Han 《Proceedings of the American Mathematical Society》2002,130(11):3259-3267
Let be a real expansive matrix. We characterize the reducing subspaces of for -dilation and the regular translation operators acting on We also characterize the Lebesgue measurable subsets of such that the function defined by inverse Fourier transform of generates through the same -dilation and the regular translation operators a normalized tight frame for a given reducing subspace. We prove that in each reducing subspace, the set of all such functions is nonempty and is also path connected in the regular -norm.