全文获取类型
收费全文 | 681篇 |
免费 | 35篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 5篇 |
化学工业 | 133篇 |
金属工艺 | 36篇 |
机械仪表 | 23篇 |
建筑科学 | 2篇 |
能源动力 | 21篇 |
轻工业 | 5篇 |
石油天然气 | 9篇 |
无线电 | 89篇 |
一般工业技术 | 241篇 |
冶金工业 | 33篇 |
原子能技术 | 18篇 |
自动化技术 | 104篇 |
出版年
2023年 | 5篇 |
2022年 | 12篇 |
2021年 | 13篇 |
2020年 | 22篇 |
2019年 | 12篇 |
2018年 | 21篇 |
2017年 | 20篇 |
2016年 | 23篇 |
2015年 | 15篇 |
2014年 | 38篇 |
2013年 | 55篇 |
2012年 | 49篇 |
2011年 | 76篇 |
2010年 | 56篇 |
2009年 | 51篇 |
2008年 | 49篇 |
2007年 | 25篇 |
2006年 | 26篇 |
2005年 | 29篇 |
2004年 | 21篇 |
2003年 | 8篇 |
2002年 | 16篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 13篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1975年 | 3篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1967年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有719条查询结果,搜索用时 15 毫秒
51.
The effect of traffic distribution on communication rates and receiver complexity in ad-hoc networks is addressed, considering
a network with constant density of users and a certain traffic model. Information theoretic upper bounds on communication
rates are derived under an assumption that transmitting nodes as well as receiving nodes cooperate. It is shown that for the
case of large signal attenuation the bounds hold even when the cooperation among users is limited to a certain region of the
network domain. Furthermore, achievability bounds on communication rates are derived. The bounds rely on two proposed local
cooperation strategies. A comparison shows that the upper bounds are tight and closely follow the achievability results. Finally,
the impact of traffic localization on the receiver complexity is addressed. 相似文献
52.
Dmitri Muraviev 《溶剂提取与离子交换》2013,31(4):753-778
ABSTRACT This paper describes new perspectives for the development and wider application of extraction and ion-exchange chromatography for separation of metal ion mixtures. The stabilization of extraction chromatographic materials by different techniques, the evaluation of changes in the behaviour of immobilized reagents (extractants or water-soluble ligands) as compared to those in their “free” state, and the combination of extraction and ion-exchange within one fractionation technique are considered and discussed along with some related problems. 相似文献
53.
Using a single mode 915 MHz applicator, we fabricate novel Cu50Zr45Al5 metallic glass/polyphenylene sulfide (PPS) composites with high relative densities by microwave processing the constituents in a separated H-field with an applied pressure of about 5 MPa. The heating behaviors and structural changes of the composites have been investigated. A good bonding state between metallic glassy and PPS particles is found. The gradient structure is also induced by microwave heating of the composites with a high fraction of PPS phase. 相似文献
54.
Dmitri V. Malakhov Xing Jun Liu Ikuo Ohnuma Kiyohito Ishida 《Journal of Phase Equilibria》2000,21(6):514-520
A thermodynamic assessment of the Bi-Sn-Zn ternary system was carried out by considering the experimental data including the phase equilibria and thermodynamic properties on the basis of the CALPHAD method. A set of optimized thermodynamic parameters has been obtained, which leads to a very good fit between calculation and experiments. In particular, the thermodynamic calculations in the Sn-rich portion are presented in view of the recent progress in Pb-free solder alloys. 相似文献
55.
Zineb Felfli Amanda R. Eure Dmitri Sokolovski 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2010,268(9):1370-1052
Electron elastic total cross sections (TCSs) and differential cross sections (DCSs) in both impact energy and scattering angle for the excited Au and Pt atoms are calculated in the electron impact energy range 0 ? E ? 4.0 eV. The cross sections are found to be characterized by very sharp long-lived resonances whose positions are identified with the binding energies of the excited anions formed during the collisions. The recent novel Regge-pole methodology wherein is embedded through the Mulholland formula the electron-electron correlations is used together with a Thomas-Fermi type potential incorporating the crucial core-polarization interaction for the calculations of the TCSs. The DCSs are evaluated using a partial wave expansion. The Ramsauer-Townsend minima, the shape resonances and the binding energies of the excited Au− and Pt− anions are extracted from the cross sections, while the critical minima are determined from the DCSs. 相似文献
56.
V. A. Sadykov S. N. Pavlova N. F. Saputina I. A. Zolotarskii N. A. Pakhomov E. M. Moroz V. A. Kuzmin A. V. Kalinkin 《Catalysis Today》2000,61(1-4):93-99
A specially designed tubular microreactor with independent control of feed preheat as well as catalyst temperature and allowing to rapidly quench reaction products was used to test performance of supported Pt-based monolithic catalysts in the reaction of propane oxidative dehydrogenation at short contact times. To minimize the impact of undesired homogeneous reactions capable of decreasing propylene selectivity, proprietary straight-channel thin-wall high cell density corundum micromonoliths were chosen as supports. Catalytic properties of supported platinum were modified by using promoters known as dehydrogenation catalysts (tin, zinc aluminate spinel, transition metal pyrophosphates) as well as by tuning reaction mixture composition (propane/oxygen ratio, water and hydrogen content). In the operation temperature range up to 900°C with contact times 0.03–0.1 s, ethylene/propylene selectivities were found to strongly depend upon the chemical composition of the active component and type of feed. The results thus obtained demonstrate that for Pt-based catalysts, propylene yield can be substantially improved by suppressing secondary reactions of deep oxidation and cracking. 相似文献
57.
Dmitri V. Louzguine-Luzgin Alain R. Yavari Gavin Vaughan Akihisa Inoue 《Intermetallics》2009,17(7):477-480
This paper presents some crystalline structures which can be taken as the approximants of the corresponding metallic glassy phases. Such phases have a clustered structure and preferably (but not strictly necessarily) a large unit cell. Peak intensities of their radial distribution functions (RDFs) must be integrated at a step of about 0.01 nm in order to obtain RDFs similar to those of the corresponding glassy alloys owing to a degree of disorder related to the corresponding glassy structures. 相似文献
58.
The effect of Fe3+ concentration on saturation magnetic flux density (Bs) of electrodeposited Co40-44Fe60-56 films was investigated. The results show that if the conditions at the electrochemical interface for nucleation/precipitation of iron(III) hydroxide (Fe(OH)3) are reached, the Bs of electrodeposited Co40-44Fe60-56 films quickly decreases as a result of the Fe(OH)3 incorporation into deposit. These conditions are discussed as a function of the solution formulation (pH) and the parameters of electrodeposition process (current density, current efficiency, diffusion layer thickness) and a simple analytical model is developed qualitatively describing the hydroxide incorporation phenomenon and resulting decrease in Bs of Co40-44Fe60-56 films. 相似文献
59.
60.