全文获取类型
收费全文 | 3544篇 |
免费 | 250篇 |
国内免费 | 41篇 |
专业分类
电工技术 | 60篇 |
综合类 | 44篇 |
化学工业 | 800篇 |
金属工艺 | 135篇 |
机械仪表 | 135篇 |
建筑科学 | 189篇 |
矿业工程 | 18篇 |
能源动力 | 188篇 |
轻工业 | 543篇 |
水利工程 | 25篇 |
石油天然气 | 69篇 |
武器工业 | 5篇 |
无线电 | 216篇 |
一般工业技术 | 612篇 |
冶金工业 | 129篇 |
原子能技术 | 65篇 |
自动化技术 | 602篇 |
出版年
2024年 | 22篇 |
2023年 | 50篇 |
2022年 | 87篇 |
2021年 | 159篇 |
2020年 | 134篇 |
2019年 | 113篇 |
2018年 | 191篇 |
2017年 | 185篇 |
2016年 | 192篇 |
2015年 | 123篇 |
2014年 | 199篇 |
2013年 | 448篇 |
2012年 | 241篇 |
2011年 | 239篇 |
2010年 | 211篇 |
2009年 | 227篇 |
2008年 | 170篇 |
2007年 | 178篇 |
2006年 | 117篇 |
2005年 | 80篇 |
2004年 | 68篇 |
2003年 | 50篇 |
2002年 | 31篇 |
2001年 | 32篇 |
2000年 | 38篇 |
1999年 | 32篇 |
1998年 | 41篇 |
1997年 | 24篇 |
1996年 | 23篇 |
1995年 | 15篇 |
1994年 | 19篇 |
1993年 | 8篇 |
1992年 | 11篇 |
1991年 | 12篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1986年 | 2篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1973年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有3835条查询结果,搜索用时 20 毫秒
41.
Superplastic deformation and crystallization behavior of a Cu54Ni6Zr22Ti18 metallic glass were investigated. A maximum elongation of 650% was obtained at 733 K at 1 × 10−2 s−1 from the sheet fabricated by squeeze copper-mold casting method. At low strain rates, the strain-rate-sensitivity exponent value was close to 1, suggesting that Newtonian-like behavior governed the plastic flow. At a high strain rate around 10−2 s−1, a transition from Newtonian to non-Newtonian behavior took place with decrease in m value. Large strain hardening by crystallization occurred during the course of deformation. The strain hardening was found to be caused by crystallization according to the analyses of the relation of true stress vs. testing time, T-T-T diagram and DSC characteristics. The time periods up to the strain before strain hardening at 733 K for the Cu54Ni6Zr22Ti18 metallic glass were similar to that of the Zr65Al10Ni10Cu15 metallic glass at 696 K as 180–300 s (3–5 min). This coincidence could be explained by comparison of their T-T-T diagrams showing that the incubation times for crystallization of the Cu BMG at 733 K and for Zr BMG at 696 K are similar. 相似文献
42.
β-Carotene–FSS organic semiconductor/n-type Si structure has been characterized by current–voltage and capacitance–voltage methods. A deviation in I–V characteristic of the diode is observed due to effect of series resistance and interfacial layer. Cheung's functions were used to calculate diode parameters. The ideality factor, series resistance and barrier height values of the diode are n = 1.77, Rs = 10.32 (10.39) kΩ and 0.78 eV. The obtained ideality factor suggests that Au/β-carotene–FSS/n-Si Schottky diode has a metal–SiO2 oxide layer plus organic layer–semiconductor (MIOS) configuration. The capacitance–voltage characterizations of Au/β-carotene–FSS/n-Si diode at different temperatures were performed. The capacitance of the diode changes with temperature. The barrier height and ideality factor obtained from C–V curves are 0.67 eV and 1.68. The interface density properties of the diode are analyzed and the shape of the density distribution of the interface states is in the range of Ec −0.49 to −0.62 eV. It is evaluated that the FSS organic layer controls electrical charge transport properties of Au/β-carotene/n-Si diode by excluding effects of the β-carotene and SiO2 residual oxides on the hybrid diode. 相似文献
43.
44.
研究了复合稀土氧化物-钼-铼金属陶瓷阴极的二次电子发射系数和抗暴露大气性能,对发射后的表面进行了表面分析,并与单元、复合稀土-钼金属陶瓷阴极进行了对比.研究结果表明:加入微量铼的复合稀土氧化物-钼金属陶瓷阴极的二次电子发射系数可提高8%,其最大次级发射系数δm为2.65,且具有较好的抗暴露大气性能. 相似文献
45.
Although the prominent concept of the last decade – user experience – maintains its significance in diverse disciplines, especially design, its focus has changed to eliciting positive user experiences by pursuing new possibilities for consumer products rather than by solely seeking solutions to existing problems. Designers continue to aim for rich user experiences with a variety of products, but have neglected self-service (interactive) kiosks. Hence, this paper, after giving a brief overview of the positive psychology literature, demonstrates the dimensions of positive user experiences with self-service kiosks through an empirical study conducted on coffee vending machines and automated tellers. 相似文献
46.
47.
48.
Rahul Raman Pankaj K. Sa Banshidhar Majhi 《Innovations in Systems and Software Engineering》2016,12(3):201-214
Occurrence of occlusion while providing visual surveillance leads to anarchy as the track of the subject under motion may be lost. This often results into the failure of the surveillance system. The approach of predicting motion of moving subjects and hence the chances of their mutual occlusion gives an upper hand to surveillance system to take in-time necessary action towards mitigation of loss of track during dynamic occlusion. Direction of motion of a moving subject plays a major role while studying its motion. Direction along with the velocity of a subject in a 3D plane completely describes the motion of any subject. This article proposes a model‘-based approach for direction prediction of a moving subject in a 3D global plane as acquired in a 2D camera plane. The proposed approach uses the eight discrete directions of motion as proposed in and models different directions. The proposed direction prediction method is experimentally verified with six different classifiers, i.e. regression analysis, simple logistic regression, MLP, k-NN, SVM and Bays classifier over existing as well as self-acquired databases. The initial simulation results are motivating as the overall accuracies achieved through different classifiers are of the range of 87–94 \(\%\), which advocates the suitability of the said approach. 相似文献
49.
Rotman lenses are used to obtain multiple beams from a single array. Although the beams produced by the feed antennas at focal points have no path length errors, the beams produced by feed antennas at off focal points may have large path length errors. These path length errors cause deterioration in the multiple beams. In this article, two novel methods are introduced to obtain feed curves which reduce the path length errors of off focal feed points significantly, compared with the commonly used circular and elliptical feed curves. The first method obtains feed curve points based on having zero path length error at three chosen points of the radiating array for each beam direction. The second method uses the particle swarm optimization method for obtaining optimum feed points for each beam direction. The results show that there is a very significant drop in the level of the maximum path length errors (in the order of about 1:4). © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 23: 634–638, 2013. 相似文献
50.
The vehicle routing problem with deliveries and pickups is one of the main problems within reverse logistics. This paper focuses on an important assumption that divides the literature on the topic, namely the restriction that all deliveries must be completed before pickups can be made. A generalised model is presented, together with a mathematical formulation and its resolution. The latter is carried out by adopting a suitable implementation of the reactive tabu search metaheuristic. Results show that significant savings can be achieved by allowing a mixture of delivery and pickup loads on-board and yet not incurring delays and driver inconvenience. 相似文献