全文获取类型
收费全文 | 4614篇 |
免费 | 206篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 55篇 |
综合类 | 3篇 |
化学工业 | 960篇 |
金属工艺 | 88篇 |
机械仪表 | 67篇 |
建筑科学 | 276篇 |
矿业工程 | 4篇 |
能源动力 | 196篇 |
轻工业 | 532篇 |
水利工程 | 30篇 |
石油天然气 | 12篇 |
无线电 | 393篇 |
一般工业技术 | 829篇 |
冶金工业 | 447篇 |
原子能技术 | 32篇 |
自动化技术 | 906篇 |
出版年
2023年 | 44篇 |
2022年 | 69篇 |
2021年 | 125篇 |
2020年 | 84篇 |
2019年 | 101篇 |
2018年 | 111篇 |
2017年 | 101篇 |
2016年 | 142篇 |
2015年 | 126篇 |
2014年 | 160篇 |
2013年 | 288篇 |
2012年 | 292篇 |
2011年 | 348篇 |
2010年 | 303篇 |
2009年 | 275篇 |
2008年 | 285篇 |
2007年 | 247篇 |
2006年 | 213篇 |
2005年 | 180篇 |
2004年 | 160篇 |
2003年 | 139篇 |
2002年 | 124篇 |
2001年 | 67篇 |
2000年 | 79篇 |
1999年 | 57篇 |
1998年 | 72篇 |
1997年 | 63篇 |
1996年 | 60篇 |
1995年 | 46篇 |
1994年 | 53篇 |
1993年 | 37篇 |
1992年 | 27篇 |
1991年 | 27篇 |
1990年 | 23篇 |
1989年 | 29篇 |
1988年 | 17篇 |
1987年 | 25篇 |
1986年 | 21篇 |
1985年 | 21篇 |
1984年 | 22篇 |
1983年 | 20篇 |
1982年 | 23篇 |
1981年 | 17篇 |
1980年 | 14篇 |
1979年 | 18篇 |
1978年 | 9篇 |
1977年 | 16篇 |
1976年 | 10篇 |
1974年 | 7篇 |
1971年 | 6篇 |
排序方式: 共有4830条查询结果,搜索用时 15 毫秒
21.
Before describing the mainFet modelings today available, the main technological evolutions ofMesfet andTegfet are summarized. It is brought some information on the various physical effects that occur in the devices and that must be taken into account in the models. It is shown that the different kinds of modelings (Monte Carlo, two dimensional, one dimensional) constitute a continuous chain, where the different elements appear strictly complementary. Finally, the present situation concerning modeling ofMesfet andTegfet will be presented. 相似文献
22.
P. Samyn P. De Baets G. Schoukens B. Hendrickx 《Polymer Engineering and Science》2003,43(8):1477-1487
As the use of common engineering plastics in tribological systems is limited to low sliding velocities and low loads because of creep and insufficient temperature resistance, there is increasing interest in application of high‐performance polymers such as polyimides, characterized by their ability to maintain favorable mechanical properties up to their melting point. However, for practical design, tribotesting remains necessary for determination of the material's performance under a given contact situation. In this article, two commercially available polyimides are tested at relatively high sliding velocities and contact pressures under atmospheric conditions of temperature and humidity. A consistent overview of tendencies in friction and wear for pure polyimides as a function of applied normal loads and sliding velocities is given. Addition of 15% by weight graphite powder as internal solid lubricant strongly influences friction and wear. Its behavior is compared with pure polyimide grades and differences are discussed in relation with experimental measured bulk‐temperatures. A linear temperature law is derived as a function of pv‐levels and a steady‐state condition is found at different temperature levels, in accordance with thermal conductivity of the polymer bulks. In case of graphite additives, a steady state in temperature coincides with the regime condition of wear rate. 相似文献
23.
Using atomic force spectroscopy, we investigated the adhesion-promoting ability of chromium. An intermediate layer of chromium can overcome the low adhesion between metal films and silicon dioxide. For the first time, we quantitatively studied this experimentally well known fact. We compared the adhesion between chromium and different substrates such as gold, silver, mica, and silicon dioxide and, beyond that, the adhesion between silicon dioxide and the same substrates. To avoid additional effects due to water, we chose ethanol as a nonpolar solvent. Taking the interfacial energies of the surfaces with the liquid into account eliminates the direct influence of the fluid medium on the adhesion of the solid material. The results we obtained corroborate the experimental fact of higher adhesion of chromium with the chosen substrates, as well as substantiate the value of chromium as an adhesion promoter. The adhesion of chromium-coated probes on gold, silicon dioxide, and mica is higher than the adhesion of silicon dioxide probes on the same substrates. 相似文献
24.
Copper deposition in the presence of an organic additive (3-mercaptopropionic acid, MPA) was studied by cyclic voltammetry and in situ scanning tunneling microscopy (STM) and the results are compared to those for additive-free solutions. It is shown that underpotential deposition (upd) of copper onto a fully MPA-covered electrode produces a defect-rich substrate, but the defects are blocked by the dense organic film for bulk deposition, resulting in a low number of nuclei. A grain-refining effect of MPA, however, was found, when Cu deposition was initiated shortly after addition of MPA to the solution, i.e., for a low-coverage MPA adlayer. 相似文献
25.
Muhammad Khafidh Natalia Valentina Rodriguez Marc Arthur Masen Dirk Jan Schipper 《Tribology - Materials, Surfaces & Interfaces》2016,10(2):70-73
The friction in tribo-systems that contain viscoelastic materials, such as elastomers, is relevant for a large number of applications. Examples include tyres, hoses, transmission and conveyor belts. To quantify the friction in these applications, one must first understand the contact behaviour of such viscoelastic materials, both in static and in dynamic situations. This work discusses an experimental study into the change of the contact area with the sliding velocity and relates the change in contact area with the mechanical properties of the elastomer. The results show that for a tribo-system containing an elastomer, there is a threshold velocity, above which the size of the contact area significantly reduces. 相似文献
26.
There exist many ideas and assumptions about the development and meaning of modularity in biological and technical neural systems. We empirically study the evolution of connectionist models in the context of modular problems. For this purpose, we define quantitative measures for the degree of modularity and monitor them during evolutionary processes under different constraints. It turns out that the modularity of the problem is reflected by the architecture of adapted systems, although learning can counterbalance some imperfection of the architecture. The demand for fast learning systems increases the selective pressure towards modularity. 相似文献
27.
A discrete Laplace‐Beltrami operator is called perfect if it possesses all the important properties of its smooth counterpart. It is known which triangle meshes admit perfect Laplace operators and how to fix any other mesh by changing the combinatorics. We extend the characterization of meshes that admit perfect Laplacians to general polygon meshes. More importantly, we provide an algorithm that computes a perfect Laplace operator for any polygon mesh without changing the combinatorics, although, possibly changing the embedding. We evaluate this algorithm and demonstrate it at applications. 相似文献
28.
Anuja Hariharan Marc Thomas Philipp Adam Timm Teubner Christof Weinhardt 《Electronic Markets》2016,26(4):339-355
Environmental conditions and the interplay of cognitive and affective processes both exert influences on bidding behavior. This paper brings the above together, considering how the (external) auction environment determines the impact of (internal) cognitive and affective processes on bidding behavior, assessed in comparison to the optimal bid. Two aspects of the auction environment were considered, namely auction dynamics (low: first-price sealed-bid auction, high: Dutch auction) and value uncertainty (low, high). In a laboratory experiment, we assess bidders’ cognitive workload and emotional arousal through physiological measurements. We find that higher auction dynamics increase the impact of emotional arousal on bid deviations, but not that of cognitive workload. Higher value uncertainty, conversely, increases the impact of cognitive workload on bid deviations, but not that of emotional arousal. Taken together, the auction environment is a critical factor in understanding the nature of the underlying decision process and its impact on bids. 相似文献
29.
Frederik Verbist Nikos Deligiannis Marc Jacobs Joeri Barbarien Peter Schelkens Adrian Munteanu Jan Cornelis 《Multimedia Tools and Applications》2013,66(3):405-430
Distributed video coding (DVC) constitutes an original coding framework to meet the stringent requirements imposed by uplink-oriented and low-power mobile video applications. The quality of the side information available to the decoder and the efficiency of the employed channel codes are primary factors determining the success of a DVC system. This contribution introduces two novel techniques for probabilistic motion compensation in order to generate side information at the Wyner-Ziv decoder. The employed DVC scheme uses a base layer, serving as a hash to facilitate overlapped block motion estimation at the decoder side. On top of the base layer, a supplementary Wyner-Ziv layer is coded in the DCT domain. Both proposed probabilistic motion compensation techniques are driven by the actual correlation channel statistics and reuse information contained in the hash. Experimental results report significant rate savings caused by the novel side information generation methods compared to previous techniques. Moreover, the compression performance of the presented DVC architecture, featuring the proposed side-information generation techniques, delivers state-of-the-art compression performance. 相似文献
30.
Françoise Détienne Béatrice Cahour Marie-Christine Legout Bernard Gourvennec Marc Relieu Gilles Coppin 《Cognition, Technology & Work》2013,15(4):445-455
Based on the analysis of “real” Second Life meetings data, in educational and professional settings, our objective is to understand the actual uses of this kind of Virtual World and more particularly, the interactive frames constructed in SL meetings and their interrelation with uses of communication media. The originality of our analytical framework stems from the combination of two perspectives: a third view perspective based on analyses of observational data and a first view perspective based on users’ reports on their experience in SL. Our results highlight: boundaries between serious and recreational registers; avatar’s expression and attribution of feelings to the person “behind”; spatial positioning as indicators and constructors of roles and engagement; management of communication fluidity and joint focus; narrowing of communication media used for task focus content; emerging mediation role for management of fractured exchanges. 相似文献