全文获取类型
收费全文 | 197篇 |
免费 | 4篇 |
专业分类
化学 | 101篇 |
晶体学 | 5篇 |
力学 | 2篇 |
数学 | 79篇 |
物理学 | 14篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 8篇 |
2017年 | 5篇 |
2016年 | 3篇 |
2015年 | 6篇 |
2014年 | 12篇 |
2013年 | 16篇 |
2012年 | 11篇 |
2011年 | 17篇 |
2010年 | 13篇 |
2009年 | 12篇 |
2008年 | 10篇 |
2007年 | 5篇 |
2006年 | 6篇 |
2005年 | 7篇 |
2004年 | 7篇 |
2003年 | 5篇 |
2002年 | 8篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1971年 | 1篇 |
1960年 | 3篇 |
1958年 | 1篇 |
排序方式: 共有201条查询结果,搜索用时 15 毫秒
121.
A new, efficient method for investigating and optimizing the ion-nitriding process in a glow-discharge plasma is proposed and worked out in detail for the mass kinetics of Rp-3 steel. This method, which is based on the concepts of experiment planning, mathematical modelling, and nonlinear optimization, is quite general and potentially applicable to a wide class of technological and other processes depending on several parameters. 相似文献
122.
The influence of the sample surface on the propagation of ballistic phonons in cylindrical samples of hexagonal crystals is studied. Our approach is based on the solution of the Boltzmann-Peierls equation with an external phonon source. The phonon irradiation of a detector face is calculated for4He and Zn crystals. It is shown how the strong phonon focusing, occurring in the slow modes of these solids, affects on the shape of energy flux falling upon the detector area. For an appropriately chosen lengthto-radius sample ratio, phonons reflected from the sample surface dominate in the detected signal. 相似文献
123.
124.
Nguyen Van Dung Adrian Petruşel 《Journal of Fixed Point Theory and Applications》2017,19(4):2271-2285
In this paper we will point out an error in proving some results on finite iterated function systems consisting of Kannan maps, Reich maps and Chatterjea type maps. In this respect, some counter-examples are given. We also answer some open questions on iterated function systems consisting of contractive maps of Reich type and we present revisions of some theorems on iterated function systems consisting of Kannan, Reich and Chatterjea type maps, by adding a commutativity assumption on the maps. 相似文献
125.
Given a directed graph, an acyclic set is a set of vertices inducing a directed subgraph with no directed cycle. In this note, we show that for all integers , there exist oriented planar graphs of order n and digirth g for which the size of the maximum acyclic set is at most . When this result disproves a conjecture of Harutyunyan and shows that a question of Albertson is best possible. 相似文献
126.
We propose a general concept of triplet of Hilbert spaces with closed embeddings, instead of continuous ones, and we show how rather general weighted $L^2$ spaces yield this kind of generalized triplets of Hilbert spaces for which the underlying spaces and operators can be explicitly calculated. Then we show that generalized triplets of Hilbert spaces with closed embeddings can be naturally associated to any pair of Dirichlet type spaces $\mathcal{D }_\alpha (\mathbb{D }^N)$ of holomorphic functions on the unit polydisc $\mathbb{D }^N$ and we explicitly calculate the associated operators in terms of reproducing kernels and radial derivative operators. We also point out a rigging of the Hardy space $H^2(\mathbb{D }^N)$ through a scale of Dirichlet type spaces and Bergman type spaces. 相似文献
127.
A three-dimensional computation of the electric field and breakdown voltage in power cable insulation containing water trees and space charges is presented. The breakdown voltage and the conductivity of cylindrical samples of cable insulation containing water trees were measured. The samples have been aged in wet environment under ac voltages of frequencies comprised between 1 and 5 kHz. Exponential and parabolic spatial variations of permittivity and space charge density and the electrostatic, electro-kinetic and quasi-stationary regimes of the electric field were considered. The best correlation between the experimental breakdown voltage and the calculated one has been obtained in quasi-stationary regime. 相似文献
128.
129.
Wakeham D Niga P Ridings C Andersson G Nelson A Warr GG Baldelli S Rutland MW Atkin R 《Physical chemistry chemical physics : PCCP》2012,14(15):5106-5114
The nanostructure of the ethanolammonium nitrate (EtAN)-air surface has been investigated using X-ray reflectometry (XRR), vibrational sum frequency spectroscopy (VSFS) and neutral impact collision ion scattering spectroscopy (NICISS). The XRR data decays more rapidly than expected for a perfectly sharp interface, indicating a diffuse electron (scattering length) density profile. Modelling of the XRR data using three different fitting routines produced consistent interfacial profiles that suggest the formation of interfacial EtAN clusters. Consistent with this, VSFS reveals that the EtAN surface is predominantly covered by -CH(2)- moieties, with the -NH(3)(+) and -OH groups of the cation buried slightly deeper in the interface. The elemental profiles determined using NICISS also show enrichment of carbon relative to nitrogen and oxygen in the outermost surface layer, which is consistent with the surface cation orientation deduced from VSFS, and with the presence of EtAN aggregates at the liquid surface. 相似文献
130.
Glasses of the system xSm2O3?(100-x)[6TeO2? 4V2O5] where 0 ≤ x ≤ 50 mol% were prepared and investigated. IR and UV–VIS spectra show that with increase x, the network continuity breaks down with the formation of the larger numbers of non-bridging oxygen. The accommodation of the network with the excess of oxygen ions is possible by the depolymerization of the vanadate network in shorter chains, especially ortho- and pyrovanadate structural units. In order to improve the local orders and to develop crystalline phases the glass samples were kept at 275° C for 7 h. Some structural changes were observed and new crystalline phases, namely Te2V2O9 and SmVO4 crystalline phases appeared in the structure of the samples. Our UV–VIS spectroscopic data show the conversion of the Sm+ 3 to Sm+ 2 species in same time with the oxidation of V+ 3, + 4 to V+ 5 ions. 相似文献