全文获取类型
收费全文 | 1296篇 |
免费 | 72篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 22篇 |
综合类 | 4篇 |
化学工业 | 257篇 |
金属工艺 | 14篇 |
机械仪表 | 41篇 |
建筑科学 | 89篇 |
矿业工程 | 2篇 |
能源动力 | 54篇 |
轻工业 | 187篇 |
水利工程 | 12篇 |
石油天然气 | 12篇 |
武器工业 | 3篇 |
无线电 | 130篇 |
一般工业技术 | 221篇 |
冶金工业 | 100篇 |
原子能技术 | 8篇 |
自动化技术 | 219篇 |
出版年
2024年 | 4篇 |
2023年 | 14篇 |
2022年 | 48篇 |
2021年 | 61篇 |
2020年 | 50篇 |
2019年 | 58篇 |
2018年 | 64篇 |
2017年 | 54篇 |
2016年 | 68篇 |
2015年 | 39篇 |
2014年 | 58篇 |
2013年 | 100篇 |
2012年 | 76篇 |
2011年 | 82篇 |
2010年 | 71篇 |
2009年 | 62篇 |
2008年 | 46篇 |
2007年 | 57篇 |
2006年 | 33篇 |
2005年 | 28篇 |
2004年 | 30篇 |
2003年 | 24篇 |
2002年 | 15篇 |
2001年 | 14篇 |
2000年 | 18篇 |
1999年 | 27篇 |
1998年 | 25篇 |
1997年 | 34篇 |
1996年 | 19篇 |
1995年 | 8篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 11篇 |
1988年 | 10篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1976年 | 2篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有1375条查询结果,搜索用时 15 毫秒
101.
102.
The effects of hydrogen (protium) or deuterium absorption∕desorption cycling on the strength and hardness of well-annealed palladium have been evaluated in this study. The results indicate that absorption followed by complete desorption of hydrogen or deuterium increases the strength and hardness characteristics of the palladium matrix while decreasing the metal's ductility. Increasing the amount of hydrogen or deuterium during absorption leads to more pronounced effects on the strength, hardness, and ductility of palladium. The effects of hydrogen absorption∕desorption are more pronounced than those of deuterium absorption∕desorption. The observed results have been explained in terms of the generation of dislocations during hydrogen or deuterium cycling. 相似文献
103.
Molecular quantum-dot cellular automaton (QCA) offers an alternative paradigm for computing at the nano-scale. QCA circuits
require an external clock which can be generated using a network of submerged electrodes to synchronize information flow and
provide the required power to drive the computation. In this paper, the effect of electrode separation and applied potential
on the likelihood of different QCA cell states of molecular cells located above and in between two adjacent electrodes is
analyzed. Using this analysis, estimates of operational ranges are developed for the placement, applied potential, and relative
phase between adjacent clocking electrodes to ensure that only those states that are used in the computation are energetically
favorable. Conclusions on the trade-off between cell size, cell-to-cell distance, and applied clocking potential are drawn
and the temperature dependence of the operation of fundamental QCA building blocks is considered. 相似文献
104.
105.
Ordered mesoporous materials such as MCM-41 and SBA-15, which exhibit cylindrical pores open at both ends and SBA-16 with spherical pores, show a strong influence on adsorption and catalytic processes, basically due to their defined pore sizes. In general, the textural characteristics of these materials are obtained by N2 adsorption?Cdesorption isotherms at 77 K where, for the calculus of the mesopores size, the ??Kelvin equation?? is used. Thus, several authors have conducted studies on the pore size distribution (PSD) for these materials, applying diverse methods such as: Barret, Joyner and Halenda (BJH); Dollimore and Heal (DH); and Kruk, Jaroniec and Sayari (BJH-KJS) methods. To obtain the PSD, the BJH and DH methods were proposed for cylindrical pores, using the desorption branch data of the isotherm, meanwhile the BJH-KJS method uses the adsorption branch data, but assumes the mechanism corresponding to the desorption branch for cylindrical pores. Due to the diversity of methods to evaluate the PSD, all of them with different considerations, it is difficult to determine the most suitable. In this work, with the aim to improve the analysis, the PSD was evaluated from the N2 adsorption?Cdesorption isotherms at 77 K for a series of materials, MCM-41, SBA-15 and SBA-16 type, synthesized in our laboratory. By a modification in the Kelvin equation with the addition of a correction term (f c ) and assuming appropriate mechanisms of capillary condensation and capillary evaporation, an improved method is proposed to be used for cylindrical as well as spherical pore geometries based on the BJH algorithm. This term was obtained adjusting simulated isotherms with different values of f c to the experimental isotherm. The results were compared to those obtained by traditional methods and by the Non-Local Density Functional Theory (NLDFT) model. 相似文献
106.
Approximate analytical expressions are derived for the mean gain and the excess noise factor of avalanche photodiodes including the effect of dead space. The analysis is based on undertaking a characteristic-equation approach to obtain an approximate analytical solution to the existing system of recurrence equations which characterize the statistics of the random multiplication gain. The analytical expressions for the excess noise factor and the mean gain are shown to be in good agreement with the exact results obtained from numerical solutions of the recurrence equations for values of the dead space reaching up to 20% of the width of the multiplication region 相似文献
107.
Improvement of the corrosion fatigue behavior of steels by paint-coating Paint-coatings have been used extensively to prevent corrosion of steel. In order to investigate the influence of an anticorrosive paint on the corrosion fatigue strength of steel, specimens of SAE 4135 in a quenched and tempered state, and in salt bath nitrocarburized state, on the one hand, and specimens of the steel SAE 5115 in a salt bath carburized state, on the other hand, were subjected to comparative rotating bending fatigue tests in inert media and in aqueous 5 pct NaCl. The results demonstrate that the 5 pct NaCl environment is reducing fatigue life drastically, but the painting treatment, however, was found to improve significantly the corrosion fatigue life. Regarding the beneficial effect of the painting treatment on the corrosion fatigue behavior, a superiority of the nitrocarburized variant in contrast to the other variants was ascertained. 相似文献
108.
109.
110.
Karim A. Black K.A. Abraham P. Lofgreen D. Chiu Y.J. Piprek J. Bowers J.E. 《Photonics Technology Letters, IEEE》2000,12(11):1438-1440
We report 85/spl deg/C continuous-wave electrically pumped operation of a 1528-nm vertical-cavity laser. An InP-InGaAsP active region was wafer bonded to the GaAs-AlGaAs mirrors, with a superlattice barrier to reduce the defect density in the active region. 相似文献