全文获取类型
收费全文 | 443篇 |
免费 | 17篇 |
专业分类
电工技术 | 4篇 |
综合类 | 1篇 |
化学工业 | 156篇 |
金属工艺 | 9篇 |
机械仪表 | 15篇 |
建筑科学 | 5篇 |
能源动力 | 19篇 |
轻工业 | 6篇 |
水利工程 | 4篇 |
石油天然气 | 1篇 |
无线电 | 27篇 |
一般工业技术 | 132篇 |
冶金工业 | 10篇 |
原子能技术 | 3篇 |
自动化技术 | 68篇 |
出版年
2023年 | 11篇 |
2022年 | 23篇 |
2021年 | 18篇 |
2020年 | 12篇 |
2019年 | 15篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 27篇 |
2015年 | 14篇 |
2014年 | 22篇 |
2013年 | 26篇 |
2012年 | 26篇 |
2011年 | 37篇 |
2010年 | 25篇 |
2009年 | 18篇 |
2008年 | 25篇 |
2007年 | 22篇 |
2006年 | 22篇 |
2005年 | 17篇 |
2004年 | 21篇 |
2003年 | 12篇 |
2002年 | 15篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 8篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1991年 | 3篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有460条查询结果,搜索用时 15 毫秒
91.
Materials with negative Poisson’s ratio (NPR) effects have been studied for decades. However, the studies have mainly focused on 2D periodic structures which only have NPR effects in certain in-plane directions. In this paper, a novel concept is proposed to develop composite structures with isotropic NPR effects using NPR random inclusions. The study starts from a finite element analysis of deformation mechanisms of two 2D representative cells which are embedded with a re-entrant square and a re-entrant triangle, respectively. Based on the analysis results, the re-entrant triangles are selected as random inclusions into a matrix to form 2D composite structures. Four such composite structures are built with different numbers of inclusions through a parametric model, and their NPR effects and mechanical behaviors are analyzed using the finite element method. The results show that the isotropic NPR effects of composites can be obtained with high random re-entrant inclusions. Thus, the novel concept proposed is numerically proved by this study. 相似文献
92.
Soloviev VY Zacharakis G Spiliopoulos G Favicchio R Correia T Arridge SR Ripoll J 《Journal of the Optical Society of America. A, Optics, image science, and vision》2012,29(6):980-988
We report three-dimensional tomographic reconstruction of optical parameters for the mesoscopic light scattering regime from experimentally obtained datasets by using polarized light. We present a numerically inexpensive approximation to the radiative transfer equation governing the polarized light transport. This approximation is employed in the reconstruction algorithm, which computes two optical parameters by using parallel and perpendicular polarizations of transmitted light. Datasets were obtained by imaging a scattering phantom embedding highly absorbing inclusions. Reconstruction results are presented and discussed. 相似文献
93.
To clean the exhaust emissions as one of the most important tasks in pollution control, a study on the treatment of engine emissions with discharge assistance was reported. A DBD plasma source shaped in grid and cylinder was examined in different engine operational modes to reduce the NOX content of diesel engine exhaust. The composition of the exhaust gases and chemical reactions initiated by the discharge were analyzed. The discharge frequency had a crucial impact on the device’s performance and gas treatment. The voltages applied to the discharge gap could alter the chemical reactions occurring in the treated gases, which were indicated by the NO to NO2 ratio. The operation of the system was studied at frequencies ranging from 400 Hz to 16 kHz. 相似文献
94.
Friedlander Myrna L.; Friedman Michelle L.; Miller Matthew J.; Ellis Michael V.; Friedlander Lee K.; Mikhaylov Vadim G. 《Canadian Metallurgical Quarterly》2010,57(3):345
The authors conducted 3 studies to develop and investigate the psychometric properties of the American Jewish Identity Scales (AJIS), a brief self-report measure that assesses cultural identification and religious identification. Study 1 assessed the content validity of the item pool using an expert panel. In Study 2, 1,884 Jewish adults completed the initial AJIS and various measures of ethnic identity, collective self-esteem, and religiosity. Using confirmatory factor analyses, the authors selected and cross-validated 33 items that loaded highly and differentially on the 2 theorized latent factors. Study 3 assessed the AJIS's short-term stability and its relation to social desirability. Tests of reliability and construct validity provided initial psychometric support for the measure and confirmed the theorized primary salience of cultural identification. Participants reported significantly more private than public collective self-esteem, and the most Jewish-identified participants reported greater private self-esteem, acculturative stress, and perceived discrimination than did their more assimilated counterparts. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
95.
Parveen Kumar Junichi Ida Vadim V. Guliants 《Microporous and mesoporous materials》2008,110(2-3):595-599
This communication reports experimental efforts to synthesize defect-free mesoporous MCM-48 membranes with improved gas flux. We demonstrate a facile and inexpensive method of synthesizing defect-free supported MCM-48 membranes with improved N2 and CO2 permeance (>2 × 10−7 mol/m2 s Pa) employing asymmetric supports for the membrane synthesis which contain layers of macropores possessing different pore sizes. The membranes prepared on asymmetric -alumina supports displayed higher gas permeance than those fabricated on symmetric supports (N2 permeance <10−7 mol/m2 s Pa) as confirmed by unsteady-state gas permeation experiments. Further improvement in gas permeance was achieved by covering one face and the sides of the support with a ceramic tape during membrane synthesis. 相似文献
96.
Ekaterina S. Lokteva Aleksey E. LazhkoElena V. Golubina Vadim V. TimofeevAlexander V. Naumkin Tatiana V. YagodovskayaSergey N. Gaidamaka Valery V. Lunin 《The Journal of Supercritical Fluids》2011,58(2):263-271
Carbonaceous deposits formation was established as the primary reason of Pd/TiO2 catalyst deactivation during reductive processing of CCl4 to form hydrodechlorination and oligomerization products. Three methods of carbonaceous deposits elimination were tested: (1) extraction by supercritical CO2, (2) oxidation by ozone in supercritical CO2, and (3) low-temperature glow-discharge oxygen plasma treatment. Synchronic thermal analysis confirms effective carbonaceous deposits removal during regeneration by ozone or low temperature glow-discharge oxygen plasma; by XPS deep oxidation of surface Pd after oxidative treatment (by ozone or oxygen plasma) was found. Thus H2 reduction was proposed as the second step making possible full regeneration of initial catalytic activity of Pd/TiO2. 相似文献
97.
The stress–strain behaviour of polypropylene fibres is evaluated for various tensile strain rates. Fibre samples are extracted from a thermally bonded nonwoven and fixed in a low-load tensile test machine. A methodology is introduced to implement a constant true strain rate at high strain tests for conventional tensile test machines. The obtained results indicate that polypropylene fibres show a highly viscous behaviour, especially during the initial stage of load application. No significant difference in a tensile behaviour of fibres was observed for loading regimes with a constant true strain rate and a constant engineering strain rate. 相似文献
98.
A theoretical model of the combustion of a nitramine solid propellant in the presence of a plasma jet is proposed. Unlike standard double‐base compositions, nitramine propellants exhibit experimental evidence that plasma induces a burning rate enhancement. The model is based on heat transfer considerations and proposes a closed‐form solution of the enhancement of the propellant burning rate as a function of the thermophysical parameters of the system. The model provides a good qualitative agreement with experimental results. 相似文献
99.
Vadim S. Mikulich Alexander A. Muravsky Anatoli A. Murauski Iryna N. Kukhta Vladimir E. Agabekov Rashid Altamimi 《Journal of the Society for Information Display》2014,22(1):29-34
There are many photoaligned azo dyes that can be used for orientation of liquid crystals in various display devices. However, the structure of these compounds needs to be optimized to increase the rate of the process of molecule photoalignment, as well as to spread the application of these compounds. The main coordination metal that presents in the molecules of azo dyes is sodium derivatives. The use of other alkali metals remains an open question. We used quantum‐chemical computation methods and reversible intermolecular bonding model to determine the effect of metal coordination on the velocity of photoalignment. The theoretical predictions were experimentally verified using sodium, potassium, lithium, and cesium salts of the model azo dye synthesized by us. We conclude that potassium azo derivatives are the fastest, ceteris paribus. 相似文献
100.
Ecto-ATPase (ecto-adenosine triphosphatase), a key enzyme of cardiac metabolism, is responsible for modulation of the concentration of extracellular nucleotides in the heart. We present methodology consisting of the combined use of biochemical and histocytochemical techniques to study its properties. Using samples from essentially the same preparation, we applied biochemistry and histocytochemistry to determine biochemical characteristics of ecto-ATPase and an in situ localization of its reactivity. Our results indicated that detected enzyme resists fixation, depends on divalent ions, and hydrolyzes ATP, but not AMP or ADP-beta-S. Reaction product of the enzyme activity was found confined to the extracellular surface of the plasma membrane of cardiac myocytes and endothelial cells due to the corresponding orientation of the enzyme active sites. Experiments using an inhibitor justified specificity of the reaction. When used together with molecular biological and immunocytochemical techniques, the present methodological approach should be capable of yielding important information about the actual ability of ecto-ATPase to operate. 相似文献