全文获取类型
收费全文 | 42659篇 |
免费 | 15038篇 |
国内免费 | 99篇 |
专业分类
电工技术 | 952篇 |
综合类 | 165篇 |
化学工业 | 18344篇 |
金属工艺 | 541篇 |
机械仪表 | 1038篇 |
建筑科学 | 1846篇 |
矿业工程 | 95篇 |
能源动力 | 1130篇 |
轻工业 | 7372篇 |
水利工程 | 326篇 |
石油天然气 | 110篇 |
武器工业 | 7篇 |
无线电 | 7615篇 |
一般工业技术 | 12363篇 |
冶金工业 | 886篇 |
原子能技术 | 110篇 |
自动化技术 | 4896篇 |
出版年
2024年 | 11篇 |
2023年 | 85篇 |
2022年 | 147篇 |
2021年 | 408篇 |
2020年 | 1552篇 |
2019年 | 3254篇 |
2018年 | 3231篇 |
2017年 | 3563篇 |
2016年 | 4014篇 |
2015年 | 4089篇 |
2014年 | 4106篇 |
2013年 | 5283篇 |
2012年 | 3068篇 |
2011年 | 2823篇 |
2010年 | 2959篇 |
2009年 | 2809篇 |
2008年 | 2336篇 |
2007年 | 2126篇 |
2006年 | 1902篇 |
2005年 | 1563篇 |
2004年 | 1488篇 |
2003年 | 1496篇 |
2002年 | 1439篇 |
2001年 | 1265篇 |
2000年 | 1182篇 |
1999年 | 567篇 |
1998年 | 164篇 |
1997年 | 139篇 |
1996年 | 103篇 |
1995年 | 86篇 |
1994年 | 78篇 |
1993年 | 50篇 |
1992年 | 50篇 |
1991年 | 64篇 |
1990年 | 38篇 |
1989年 | 35篇 |
1988年 | 29篇 |
1987年 | 21篇 |
1986年 | 33篇 |
1985年 | 15篇 |
1984年 | 19篇 |
1983年 | 15篇 |
1982年 | 9篇 |
1981年 | 11篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1977年 | 7篇 |
1976年 | 14篇 |
1975年 | 6篇 |
1970年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
From its foundation until 2004, ETRI has registered over 1,000 US patents. This letter analyzes the characteristics of these patents and addresses the explanatory factors affecting their citation counts. For explanatory variables, research team related variables, invention specific variables, and geographical domain related variables are suggested. Zero‐altered count data models are used to test the impact of independent variables. A key finding is that technological cumulativeness, the scale of invention, outputs in the electronic field, and the degree of dependence on the US technology domain positively affect the citation counts of ETRI‐invented US patents. The magnitude of international presence appears to negatively affect the citation counts of ETRI‐invented US patents. 相似文献
92.
93.
A route to synthesize ZSM‐5 crystals with a bimodal micro/mesoscopic pore system has been developed in this study; the successful incorporation of the mesopores within the ZSM‐5 structure was performed using tetrapropylammonium hydroxide (TPAOH)‐impregnated mesoporous materials containing carbon nanotubes in the pores, which were encapsulated in the ZSM‐5 crystals during a solid rearrangement process within the framework. Such mesoporous ZSM‐5 zeolites can be readily obtained as powders, thin films, or monoliths. 相似文献
94.
T. Choi J.‐H. Jang C.K. Ullal M.C. LeMieux V.V. Tsukruk E.L. Thomas 《Advanced functional materials》2006,16(10)
The probing of the micromechanical properties within a two‐dimensional polymer structure with sixfold symmetry fabricated via interference lithography reveals a nonuniform spatial distribution in the elastic modulus “imprinted” with an interference pattern in work reported by Tsukruk, Thomas, and co‐workers on p. 1324. The image prepared by M. Lemieux and T. Gorishnyy shows how the interference pattern is formed by three laser beams and is transferred to the solid polymer structure. The elastic and plastic properties within a two‐dimensional polymer (SU8) structure with sixfold symmetry fabricated via interference lithography are presented. There is a nonuniform spatial distribution in the elastic modulus, with a higher elastic modulus obtained for nodes (brightest regions in the laser interference pattern) and a lower elastic modulus for beams (darkest regions in the laser interference pattern) of the photopatterned films. We suggest that such a nonuniformity and unusual plastic behavior are related to the variable material properties “imprinted” by the interference pattern. 相似文献
95.
Woo‐Seok Cheong 《ETRI Journal》2003,25(6):503-509
Selective epitaxial growth (SEG) of silicon has attracted considerable attention for its good electrical properties and advantages in building microstructures in high‐density devices. However, SEG problems, such as an unclear process window, selectivity loss, and nonuniformity have often made application difficult. In our study, we derived processing diagrams for SEG from thermodynamics on gas‐phase reactions so that we could predict the SEG process zone for low pressure chemical vapor deposition. In addition, with the help of both the concept of the effective supersaturation ratio and three kinds of E‐beam patterns, we evaluated and controlled selectivity loss and nonuniformity in SEG, which is affected by the loading effect. To optimize the SEG process, we propose two practical methods: One deals with cleaning the wafer, and the other involves inserting dummy active patterns into the wide insulator to prevent the silicon from nucleating. 相似文献
96.
97.
Polyaryloxydiphenylsilanes were prepared from phosphorus‐containing diols and diphenydichlorolsilane through solution polymerization. With a stoichiometric imbalance in feed monomers, the resulting polymers exhibited moderate melting points and good processing properties. The polymers prepared showed initial decomposition temperatures above 340 °C, excellent thermal stability, high char yields at 850 °C and very high limited oxygen index values of 56–59. The polymers' char yields and their (P + Si) contents showed linear relationships. © 2003 Society of Chemical Industry 相似文献
98.
L. Sheeney‐Haj‐Ichia S. Pogorelova Y. Gofer I. Willner 《Advanced functional materials》2004,14(5):416-424
Three different configurations of Au‐nanoparticle/CdS‐nanoparticle arrays are organized on Au/quartz electrodes for enhanced photocurrent generation. In one configuration, Au‐nanoparticles are covalently linked to the electrode and the CdS‐nanoparticles are covalently linked to the bare Au‐nanoparticle assembly. The resulting photocurrent, φ = 7.5 %, is ca. 9‐fold higher than the photocurrent originating from a CdS‐nanoparticle layer that lacks the Au‐nanoparticles, φ = 0.8 %. The enhanced photocurrent in the Au/CdS nanoparticle array is attributed to effective charge separation of the electron–hole pair by the injection of conduction‐band electrons from the CdS‐ to the Au‐nanoparticles. Two other configurations involving electrostatically stabilized bipyridinium‐crosslinked Au/CdS or CdS/Au nanoparticle arrays were assembled on the Au/quartz crystal. The photocurrent quantum yields in the two systems are φ = 10 % and φ = 5 %, respectively. The photocurrents in control systems that include electrostatically bridged Au/CdS or CdS/Au nanoparticles by oligocationic units that lack electron‐acceptor units are substantially lower than the values observed in the analogous bipyridinium‐bridged systems. The enhanced photocurrents in the bipyridinium‐crosslinked systems is attributed to the stepwise electron transfer of conduction‐band electrons to the Au‐nanoparticles by the bipyridinium relay bridge, a process that stabilizes the electron–hole pair against recombination and leads to effective charge separation. 相似文献
99.
N. Jongen M. Donnet P. Bowen J. Lemaître H. Hofmann R. Schenk C. Hofmann M. Aoun‐Habbache S. Guillemet‐Fritsch J. Sarrias A. Rousset M. Viviani M.T. Buscaglia V. Buscaglia P. Nanni A. Testino J.R. Herguijuela 《化学工程与技术》2003,26(3):303-305
The synthesis of powders with controlled shape and narrow particle size distributions is still a major challenge for many industries. A continuous Segmented Flow Tubular Reactor (SFTR) has been developed to overcome homogeneity and scale‐up problems encountered when using batch reactors. Supersaturation is created by mixing the co‐reactants in a micromixer inducing precipitation; the suspension is then segmented into identical micro‐volumes by a non‐miscible fluid and sent through a tube. These micro‐volumes are more homogeneous when compared to large batch reactors leading to narrower size distributions, better particle morphology, polymorph selectivity and stoichiometry. All these features have been demonstrated on single tube SFTR for different chemical systems. To increase productivity for commercial application the SFTR is being “scaled‐out” by multiplying the number of tubes running in parallel instead of scaling‐up by increasing their size. The versatility of the multi‐tube unit will allow changes in type of precipitate with a minimum of new investment as new chemistry can be researched, developed and optimised in a single tube SFTR and then transferred to the multi‐tube unit for powder production. 相似文献
100.
M. Ganschow C. Hellriegel E. Kneuper M. Wark C. Thiel G. Schulz‐Ekloff C. Bruchle D. Whrle 《Advanced functional materials》2004,14(3):269-276
Dye‐loaded AlPO4‐5 single crystals were prepared by microwave‐assisted hydrothermal synthesis from a batch, containing a mixture of three chromophores (Coumarin 40, Rhodamine BE50, and Oxazine 1) differing in their absorption range, molecular dimensions, and solubilities. Confocal fluorescence images reveal a spatial separation effect of the dye molecules, where the slimmer, more‐soluble dye molecule (Coumarin 40) is uniformly distributed in the body of the single crystal, and the bulky and/or less‐soluble ones (Rhodamine BE50, Oxazine 1) are situated in distinct domains. Visible spectra show good panchromatic absorption of visible light. Fluorescence lifetime measurements indicate the presence of an energy transfer cascade of the entirely fixed dye molecules from Coumarin 40 to Oxazine 1. The transfer mechanism is predominantly radiative. 相似文献