全文获取类型
收费全文 | 14278篇 |
免费 | 1154篇 |
国内免费 | 613篇 |
学科分类
工业技术 | 16045篇 |
出版年
2024年 | 63篇 |
2023年 | 256篇 |
2022年 | 354篇 |
2021年 | 543篇 |
2020年 | 456篇 |
2019年 | 369篇 |
2018年 | 433篇 |
2017年 | 476篇 |
2016年 | 402篇 |
2015年 | 542篇 |
2014年 | 676篇 |
2013年 | 879篇 |
2012年 | 835篇 |
2011年 | 839篇 |
2010年 | 810篇 |
2009年 | 721篇 |
2008年 | 700篇 |
2007年 | 759篇 |
2006年 | 756篇 |
2005年 | 627篇 |
2004年 | 444篇 |
2003年 | 485篇 |
2002年 | 581篇 |
2001年 | 463篇 |
2000年 | 374篇 |
1999年 | 379篇 |
1998年 | 326篇 |
1997年 | 284篇 |
1996年 | 246篇 |
1995年 | 196篇 |
1994年 | 166篇 |
1993年 | 114篇 |
1992年 | 102篇 |
1991年 | 82篇 |
1990年 | 66篇 |
1989年 | 48篇 |
1988年 | 41篇 |
1987年 | 24篇 |
1986年 | 31篇 |
1985年 | 10篇 |
1984年 | 16篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 11篇 |
1980年 | 13篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 8篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
通过研究基片种类、加热温度、保温时间、冷却速度及是否加入催化剂等不同工艺参数对低维Ga2O3,纳米材料形貌的影响,确定出合成5种不同形貌β-Ga2O3纳米材料的工艺条件。场发射扫描电镜(FE-SEM)表明5种不同形貌α-Ga2O3纳米材料分别为纳米线、纳米棒、纳米带、纳米环及纳米片。X射线衍射(X-ray)分析结果表明不同形貌纳米材料均为晶格常数日=1.223nm,b=0.304nm,c=0.58nm,a=90°,β=103.7°,γ=90°的单斜晶系β-Ga2O3晶体。 相似文献
72.
不等厚板经过渡削薄处理后的对接焊缝,由于厚度的不均匀,射线穿透时的衰减不一样,对射线检测带来很大的麻烦。常用的超声波探伤方法在定位和定级方面比较困难,本文给出利用现在先进的数字式超声波探伤仪进行准确探伤的方法。 相似文献
73.
粉煤灰填充尼龙6浇铸制品的研究 总被引:5,自引:0,他引:5
将粉煤灰用硅烷偶联剂处理后填充到尼龙6浇铸制品(MC尼龙)中,可以改善制品的吸水性、收缩率及热稳定性等,还可以降低成本。该项研究结果有很大的实用价值。 相似文献
74.
Xiangming He Weihua Pu Li Wang Jianguo Ren Changyin Jiang Chunrong Wan 《Electrochimica acta》2007,52(11):3651-3653
A novel process was proposed to synthesize nano Sb-encapsulated pyrolytic polyacrylonitrile composite for anode material in lithium secondary batteries. The preparation started with the dissolution of SbCl3 and polyacrylonitrile (PAN) in dimethylformamide (DMF) solution, followed by the addition of KBH4 to reduce Sb3+ in the solution. The Sb composite was obtained by pyrolysis of the Sb/PAN mixture that precipitated out when the DMF solution was added by plentiful water. The TEM analysis showed that about 100-200 nm Sb particles were embedded by the pyrolyzed PAN, which provided a conductive matrix to relieve the morphological change of Sb during electrochemical cycling. As-prepared composite presented good cycleability for lithium storage. The proposed process paves an effective way to prepare high performance alloy based composite anode materials for high performance lithium-ion batteries. 相似文献
75.
The discharge performance of a tubular electrode of the lead-acid battery based on a pseudo steadystate approach was simulated. It was found that the discharge reaction started from the central interior region instead of from the outer surface as in the usual plate-type electrodes. This is due to the fact that the central region has a smaller reaction surface than the outer region of the tubular electrode. This consequently causes a higher current density near the center. A comparison of the theoretical prediction and experimental result shows that the model is fairly accurate except for very high rate discharge conditions. 相似文献
76.
Rapid Reactive Synthesis and Sintering of Submicron TiC/SiC Composites through Spark Plasma Sintering 总被引:1,自引:0,他引:1
Lianjun Wang Wan Jiang Lidong Chen Shengqiang Bai 《Journal of the American Ceramic Society》2004,87(6):1157-1160
Submicrometer TiC/SiC composites were fabricated by a rapid reactive sintering process through spark plasma sintering (SPS) technique using the carbon, titanium, and nanosized-SiC powders without any additive. It was found that the composite could be sintered in a relatively short time (8 min at 1480°C) to 97.9% of theoretical density. After sintering, the phase constituents and microstructures of the samples were analyzed by X-ray diffraction techniques and observed by scanning electron microscopy. The effect of nanosized and microsized SiC additives on the microstructure of TiC/SiC composites was investigated. 相似文献
77.
78.
Alternative hydrocarbon solvents for cottonseed extraction 总被引:3,自引:0,他引:3
P. J. Wan D. R. Pakarinen R. J. Hron Sr. O. L. Richard E. J. Conkerton 《Journal of the American Oil Chemists' Society》1995,72(6):653-659
Hexane has been used for decades to extract edible oil from cottonseed. However, due to increased regulations affecting hexane
because of the 1990 Clean Air Act and potential health risks, the oil-extraction industry urgently needs alternative hydrocarbon
solvents to replace hexane. Five solvents,n-heptane, isohexane, neohexane, cyclohexane, and cylopentane, were compared with commercial hexane using a benchscale extractor.
The extractions were done with a solvent to cottonseed flake ratio of 5.5 to 1 (w/w) and a miscella recycle flow rate of 36
mL/min/sq cm (9 gal/min/sq ft) at a temperature of 10 to 45°C below the boiling point of the solvent. After a 10-min single-stage
extraction, commercial hexane removed 100% of the oil from the flakes at 55°C; heptane extracted 100% at 75°C and 95.9% at
55°C; isohexane extracted 93.1% at 45°C; while cyclopentane, cyclohexane, and neohexane removed 93.3, 89.4, and 89.6% at 35,
55, and 35°C, respectively. Each solvent removed gossypol from cottonseed flakes at a different rate, with cyclopentane being
most and neohexane least effective. Based on the bench-scale extraction results and the availability of these candidate solvents,
heptane and isohexane are the alternative hydrocarbon solvents most likely to replace hexane.
Presented in part at the AOCS Annual Meeting & Expo, Atlanta, Georgia, May 1994. 相似文献
79.
80.
聚乙烯转光棚膜的加工及应用研究 总被引:8,自引:3,他引:8
本文对聚乙烯转光棚膜的加工和光转换剂的作用、配比关系及物理性能进行了讨论。 相似文献