全文获取类型
收费全文 | 3170篇 |
免费 | 209篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 21篇 |
化学工业 | 890篇 |
金属工艺 | 55篇 |
机械仪表 | 80篇 |
建筑科学 | 118篇 |
矿业工程 | 13篇 |
能源动力 | 106篇 |
轻工业 | 568篇 |
水利工程 | 28篇 |
石油天然气 | 18篇 |
无线电 | 201篇 |
一般工业技术 | 462篇 |
冶金工业 | 192篇 |
原子能技术 | 25篇 |
自动化技术 | 606篇 |
出版年
2024年 | 9篇 |
2023年 | 50篇 |
2022年 | 127篇 |
2021年 | 174篇 |
2020年 | 103篇 |
2019年 | 125篇 |
2018年 | 142篇 |
2017年 | 125篇 |
2016年 | 161篇 |
2015年 | 103篇 |
2014年 | 169篇 |
2013年 | 247篇 |
2012年 | 213篇 |
2011年 | 227篇 |
2010年 | 161篇 |
2009年 | 167篇 |
2008年 | 146篇 |
2007年 | 147篇 |
2006年 | 93篇 |
2005年 | 72篇 |
2004年 | 81篇 |
2003年 | 55篇 |
2002年 | 70篇 |
2001年 | 40篇 |
2000年 | 34篇 |
1999年 | 28篇 |
1998年 | 38篇 |
1997年 | 35篇 |
1996年 | 28篇 |
1995年 | 38篇 |
1994年 | 25篇 |
1993年 | 22篇 |
1992年 | 13篇 |
1991年 | 13篇 |
1990年 | 13篇 |
1989年 | 12篇 |
1988年 | 10篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有3383条查询结果,搜索用时 0 毫秒
1.
Effect of the Twisting Motion on the Nonunifornities of Transmyocardial Fiber Mechanics and Energy Demand A Theoretical Study 总被引:3,自引:0,他引:3
The contraction of the left ventricle (LV) is manifested by a distribution of strains and strain rates throughout the muscle thickness. Using a nested shell spheroidal model of the LV, which accounts for a fiber angle distribution from + 60°at the endocardium to ?60° at the epicardium, and the radial electrical activation pattern from the endocardium to the epicardium, it can be shown that endocardial layers undergo higher strains than the epicardial layers throughout the cardiac cycle, and higher length changes characterize the endocardial sarcomeres relative to the epicardial sarcomeres. However, the calculated nonuniformities in the sarcomeres' shortening are significantly moderated when the physiological twisting motion of the LV around the longitudinal axis is accounted for. Thus, the twisting motion of the heart is a basic mechanism by which the sarcomere function is maintained within its physiological range. 相似文献
2.
3.
Symbolic parametrization of curves 总被引:1,自引:0,他引:1
If algebraic varieties like curves or surfaces are to be manipulated by computers, it is essential to be able to represent these geometric objects in an appropriate way. For some applications an implicit representation by algebraic equations is desirable, whereas for others an explicit or parametric representation is more suitable. Therefore, transformation algorithms from one representation to the other are of utmost importance.We investigate the transformation of an implicit representation of a plane algebraic curve into a parametric representation. Various methods for computing a rational parametrization, if one exists, are described. As a new idea we introduce the concept of working with classes of conjugate (singular or simple) points on curves. All the necessary operations, like determining the multiplicity and the character of the singular points or passing a linear system of curves through these points, can be applied to such classes of conjugate points. Using this idea one can parametrize a curve if one knows only one simple point on it. We do not propose any new method for finding such a simple point. By classical methods a rational point on a rational curve can be computed, if such a point exists. Otherwise, one can express the coordinates of such a point in an algebraic extension of degree 2 over the ground field. 相似文献
4.
5.
6.
7.
Summary The thermal properties of an epoxy resin (diglycidyl ether Bisphenol A, DGEBA) cured with a primary amine (ethylenediamine, ETDA) and filled with 10, 20 and 30 wt. % of ultra fine copper particles were analyzed. The thermal results were evaluated by means of the Romero-Garcia method, which allowed to obtain the resin degradation kinetic parameters, as well as the possible decomposition mechanism. From the obtained results is possible to infer that higger copper content strongly affects the degradation process of the epoxy resin, which causes a drop off on the composites thermal stability. This behavior could be attributed to water presence, being this effect less pronounced for the resin with 10 wt. % copper and unfilled resin. Regarding to decomposition mechanism, three way transport showed the best correlation for all samples. 相似文献
8.
Javier Lara-Romero Rafael Maya-Yescas José Luis Rico-Cerda José Luis Rivera-Rojas Fernando Chiñas Castillo Matey Kaltchev 《Thin solid films》2006,496(2):463-468
The thermal decomposition of model extreme-pressure lubricant additives on clean iron was studied in ultrahigh vacuum conditions using molecular beam strategies. Methylene chloride and chloroform react to deposit a solid film consisting of FeCl2 and carbon, and evolve only hydrogen into the gas phase. No gas-phase products and less carbon on the surface are detected in the case of carbon tetrachloride. Dimethyl and diethyl disulfide react on clean iron to deposit a saturated sulfur plus carbon layer at low temperatures (∼600 K) and an iron sulfide film onto a Fe + C underlayer at higher temperatures (∼950 K). Methane is the only gas-phase product when dimethyl disulfide reacts with iron. Ethylene and hydrogen are detected when diethyl disulfide is used. 相似文献
9.
EL Romano RF Monta?o B Brito R Apitz J Alonso M Romano S Gebrán A Soyano 《Canadian Metallurgical Quarterly》1997,19(1):15-36
An increasing flow of evidences collected on elementary forms of learning processes in selected animal models evidentiates some mechanisms which can represent the basic cellular principles underlying plastic changes: 1. 5HT and second messengers of nucleotide type (like cAMP) have a pivotal role in the learning process. 2. In almost all short-term learning processes the modifications are subserved by a mechanism of protein phosphorylation. 3. In various animal models the modulation of K+ and Ca2+ channels is the molecular mechanism for learning. Experiments performed in sensory T neuron of the leech indicate that the modulation of Na+/K+ electrogenic pump is one of the fundamental mechanism for learning. 4. In long-term plastic changes, the most important finding is that newly synthesized proteins are formed. 5. In addition to what has been observed in the Aplysia model, where changes in synaptic efficacy represent the basic principles of memory storage, in the leech it has been demonstrated that a molecular machinery present in a single neuron can adapt the activity of the cell to environmental stimuli. 相似文献
10.