全文获取类型
收费全文 | 84238篇 |
免费 | 7882篇 |
国内免费 | 4080篇 |
专业分类
电工技术 | 5127篇 |
技术理论 | 6篇 |
综合类 | 5887篇 |
化学工业 | 13721篇 |
金属工艺 | 4827篇 |
机械仪表 | 5462篇 |
建筑科学 | 6378篇 |
矿业工程 | 2861篇 |
能源动力 | 2405篇 |
轻工业 | 5438篇 |
水利工程 | 1593篇 |
石油天然气 | 4877篇 |
武器工业 | 733篇 |
无线电 | 10284篇 |
一般工业技术 | 10080篇 |
冶金工业 | 3989篇 |
原子能技术 | 844篇 |
自动化技术 | 11688篇 |
出版年
2024年 | 476篇 |
2023年 | 1540篇 |
2022年 | 2571篇 |
2021年 | 3590篇 |
2020年 | 2781篇 |
2019年 | 2377篇 |
2018年 | 2646篇 |
2017年 | 2896篇 |
2016年 | 2624篇 |
2015年 | 3393篇 |
2014年 | 4189篇 |
2013年 | 4931篇 |
2012年 | 5546篇 |
2011年 | 5986篇 |
2010年 | 5075篇 |
2009年 | 4704篇 |
2008年 | 4607篇 |
2007年 | 4330篇 |
2006年 | 4654篇 |
2005年 | 3825篇 |
2004年 | 2748篇 |
2003年 | 2503篇 |
2002年 | 2377篇 |
2001年 | 2130篇 |
2000年 | 2052篇 |
1999年 | 2076篇 |
1998年 | 1772篇 |
1997年 | 1471篇 |
1996年 | 1375篇 |
1995年 | 1121篇 |
1994年 | 949篇 |
1993年 | 652篇 |
1992年 | 506篇 |
1991年 | 425篇 |
1990年 | 311篇 |
1989年 | 252篇 |
1988年 | 216篇 |
1987年 | 138篇 |
1986年 | 110篇 |
1985年 | 67篇 |
1984年 | 34篇 |
1983年 | 23篇 |
1982年 | 37篇 |
1981年 | 21篇 |
1980年 | 22篇 |
1979年 | 11篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 14篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Study on Adsorption Behavior of Rare Earth Complexes on Nanometer-Size Titanium Dioxide with ICP-AES
Inrecentyears ,rareearthelements (REEs)havebeenwidelyusedinfunctionalmaterials ,cata lystsandotherproductsinindustry ,diagnosisreagentsofmagneticresonanceimaging (MRI)inmedicineandsomefertilizersinagricultureespeciallyinChina .However,asaresultoftheirusage ,moreandmoreREEsaregettingintotheenvironment,andalsointohumanbodyviafoodchain[1,2 ] .Itisnotclearwhetherrareearthelementsareessentialforman ,soitisveryurgenttostudythebiologicaleffectofrareearthelementsinhumanhealthandenvironment .Inthes… 相似文献
62.
基于高抗热震性能的陶瓷刀具材料的微观结构设计 总被引:1,自引:0,他引:1
本文以现有的抗热震断裂和抗热震损伤的评价理论为基础,通过对材料中微裂纹的长度进行预测,从而实现了对陶瓷刀具材料的抗热震性能的微观结构设计。根据此理论对现有材料的抗热震性能的进行预测,预测结果与实际的测量结果相符,验证了该理论的正确性。 相似文献
63.
Preparation of Compound Ultrafine CeO2 by Wet-Solid-Phase Mechanochemical Modification 总被引:1,自引:0,他引:1
To satisfy practical requirements from industrial applications, an alternate route for synthesis compound ultrafine CeO2 powders by wet-solid-phase mechanochemical modification using industrial grade hydrated cerium carbonate as raw material was proposed.The effect of modifier reaction percentage, reaction time, calcining temperature and modifier amount on particle size, density, suspensibility, and hardness of compound CeO2 powder was investigated.The phase evolutions of preparation process were characterized by XRD.SEM micrograph of the final product shows that compound CeO2 powders obtained are well-dispersed, spherically-shaped, uniformly-sized and submicron-sized particles.The method is readily available in raw material, low in cost, simple in process, and has great potential for industrialization.The compound CeO2 powders of different physical properties can be synthesized by controlling the above-mentioned influence factors in preparation process. 相似文献
64.
65.
66.
Yoon Carolyn; Feinberg Fred; Hu Ping; Gutchess Angela Hall; Hedden Trey; Chen Hiu-Ying Mary; Jing Qicheng; Cui Yao; Park Denise C. 《Canadian Metallurgical Quarterly》2004,19(3):379
Understanding how aging influences cognition across different cultures has been hindered by a lack of standardized, cross-referenced verbal stimuli. This study introduces a database of such item-level stimuli for both younger and older adults, in China and the United States, and makes 3 distinct contributions. First, the authors specify which item categories generalize across age and/or cultural groups, rigorously quantifying differences among them. Second, they introduce novel, powerful methods to measure between-group differences in freely generated ranked data, the rank-ordered logit model and Hellinger Affinity. Finally, a broad archive of tested, cross-linguistic stimuli is now freely available to researchers: data, similarity measures, and all stimulus materials for 105 categories and 4 culture-by-age groups, comprising over 10,000 fully translated unique item responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
67.
通过对现代海上电子战特点深刻探讨。分析了现代海战条件对舰船电子战对抗能力需求。并对现代舰船电子战综合对抗系统所采用的新技术情况进行探讨。 相似文献
68.
Xing Gu Shariar Sabuktagin Ali Teke Daniel Johnstone Hadis Morkoç Bill Nemeth Jeff Nause 《Journal of Materials Science: Materials in Electronics》2004,15(6):373-378
ZnO is a highly efficient photon emitter, and has optical and piezoelectric properties that are attractive for a variety of applications in sensors and potentially optoelectronic devices such as emitters. Due to its identical stacking order and close lattice match to GaN, it is also being developed as a substrate material for GaN epitaxy. However, the surface finish of the ZnO is such that much of the damage induced by sawing and follow up mechanical polishing remains. We developed a thermal treatment method to eliminate surface damage on the 0 face of ZnO (0 0 0 1) to prepare it for epitaxial growth. Atomic force microscopy images of ZnO (0 0 0 1) annealed at 1050 °C for 3 h etc. show that residual scratches from mechanical polishing are removed and atomically flat, terrace-like surfaces are attained. In addition, low-temperature photoluminescence and high-resolution X-ray diffraction measurements have been employed to investigate the effect of annealing on ZnO substrates. 相似文献
69.
Ultraviolet (UV) disinfection is becoming increasingly popular as an alternative disinfection technology to chlorination in recent years. In this study, we investigated the photoreactivation of Escherichia coli following medium-pressure (MP) UV disinfection of synthetic water by a bench-scale collimated beam apparatus. The UV doses ranged from 1.6 -19.7 mWs/cm2 and photoreactivation was investigated for 6 hours under fluorescent light. In addition, chloramination was applied after UV disinfection to investigate its ability to control photoreactivation. It was found that photoreactivation occurred for all UV doses tested and the increase in bacteria numbers ranged from 0.04 to 1.35 log10. However, the degree of photoreactivation decreased with increased UV doses. Chloramination experiments revealed that the addition of 0.5 mg/l of monochloramine resulted in suppression of photoreactivation for 1 hour only. An increased monochloramine dose of 1 mg/l was found to prevent photoreactivation for the entire duration of the experiment. The results of this study have shown that photoreactivation occurs even after MP UV disinfection, although it is of a lesser extent at higher UV doses. This study has also established that secondary chloramination can effectively suppress and eliminate photoreactivation with a chloramine dose of 1 mg/l. 相似文献
70.