全文获取类型
收费全文 | 3725篇 |
免费 | 246篇 |
国内免费 | 238篇 |
专业分类
电工技术 | 213篇 |
综合类 | 427篇 |
化学工业 | 495篇 |
金属工艺 | 317篇 |
机械仪表 | 42篇 |
建筑科学 | 349篇 |
矿业工程 | 240篇 |
能源动力 | 67篇 |
轻工业 | 45篇 |
水利工程 | 75篇 |
石油天然气 | 817篇 |
武器工业 | 11篇 |
无线电 | 336篇 |
一般工业技术 | 600篇 |
冶金工业 | 107篇 |
原子能技术 | 31篇 |
自动化技术 | 37篇 |
出版年
2024年 | 6篇 |
2023年 | 41篇 |
2022年 | 58篇 |
2021年 | 91篇 |
2020年 | 99篇 |
2019年 | 86篇 |
2018年 | 74篇 |
2017年 | 120篇 |
2016年 | 113篇 |
2015年 | 122篇 |
2014年 | 170篇 |
2013年 | 196篇 |
2012年 | 248篇 |
2011年 | 257篇 |
2010年 | 205篇 |
2009年 | 211篇 |
2008年 | 219篇 |
2007年 | 256篇 |
2006年 | 246篇 |
2005年 | 202篇 |
2004年 | 185篇 |
2003年 | 170篇 |
2002年 | 141篇 |
2001年 | 89篇 |
2000年 | 81篇 |
1999年 | 92篇 |
1998年 | 70篇 |
1997年 | 54篇 |
1996年 | 53篇 |
1995年 | 39篇 |
1994年 | 46篇 |
1993年 | 29篇 |
1992年 | 25篇 |
1991年 | 20篇 |
1990年 | 23篇 |
1989年 | 16篇 |
1988年 | 7篇 |
1987年 | 10篇 |
1986年 | 9篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1974年 | 1篇 |
排序方式: 共有4209条查询结果,搜索用时 15 毫秒
1.
2.
Wire-shaped zinc samples were resistively volume heated as part of a fast-capacitor discharge circuit. Time-resolved measurements with submicrosecond resolution of the current through the specimen, the voltage drop across it, and the thermal expansion of the specimen as a function of time allow determination of the enthalpy, electrical resistivity, and density at different temperatures up to superheated liquid states of zinc far above the normal boiling point. High static pressures, up to 3800 bar of the ambient medium water, were used. An estimate of the critical pressure for zinc is given by investigations of the stability of the sample with a framing CCD camera, taking pictures of different samples varying the ambient static pressure. The critical volume and the critical temperature are obtained by means of an extrapolation of measured data at different pressures.Paper presented at the Fourth International Workshop on Subsecond Thermophysics, June 27–29, 1995, Köln, Germany. 相似文献
3.
Y. Kraftmakher 《International Journal of Thermophysics》1994,15(5):983-991
Relaxation phenomena due to equilibration of point defects in metals are reviewed. The relaxation effect in specific heat observed in tungsten and platinum confirms that in both cases the nonlinear increase in the high-temperature specific heat has to be attributed to point-defect formation. Relaxation phenomena observed by measurements of electrical resistivity and positron annihilation are also considered. The comparison of the data seems to be favorable for the conclusion that all the phenomena are of one origin. 相似文献
4.
当HDPE含量46%(质量分数,以下同)、其它添加剂(如抗氧剂、阻燃剂、交联剂和润滑剂等辅助填料)的含量11%,两种导电填料石墨(GP)和碳黑(CB)的总含量为43%时,研究结果表明石墨含量的变化对HDPE/CB-GP复合材料室温电阻率、阴C强度和后NTC强度有显著的影响.HDPE/CB-GP复合材料中GP的含量〈8.6%时,样品的室温电阻率〈30Ω·m,PTC强度〉7、后NTC强度〈1.3;电阻率.温度曲线经过17次冷热循环后重现性好,复合材料具有实际应用价值;GP在复合材料中为层片状结构。 相似文献
5.
6.
7.
介绍了高频等参数感应的基本原理。以胜利油田比较典型的 3口井为例 ,详细分析了高频感应资料在划分薄夹层、确定储层流体饱和类型、评价储层电阻率空间分布等方面的应用。研究结果表明 ,高频感应具有极高的纵向分辨率和较好的径向探测特性 ,能够准确计算地层真电阻率、侵入带电阻率及侵入半径 ,通过与常规感应及薄层测井资料的对比 ,论证了高频等参数感应在测井技术应用上的优越性 相似文献
8.
Rui Morimoto Chisato Yokomori Akiko Kikkawa Akira Izumi Hideki Matsumura 《Thin solid films》2003,430(1-2):230-235
In this paper, bulk-Si metal–oxide–semiconductor field effect transistors (MOSFETs) are fabricated using the catalytic chemical vapor deposition (Cat-CVD) method as an alternative technology to the conventional high-temperature thermal chemical vapor deposition. Particularly, formation of low-resistivity phosphorus (P)-doped poly-Si films is attempted by using Cat-CVD-deposited amorphous silicon (a-Si) films and successive rapid thermal annealing (RTA) of them. Even after RTA processes, neither peeling nor bubbling are observed, since hydrogen contents in Cat-CVD a-Si films can be as low as 1.1%. Both the crystallization and low resistivity of 0.004 Ω·cm are realized by RTA at 1000 °C for only 5 s. It is also revealed that Cat-CVD SiNx films prepared at 250 °C show excellent oxidation resistance, when the thickness of films is larger than approximately 10 nm for wet O2 oxidation at 1100 °C. It is found that the thickness required to stop oxygen penetration is equivalent to that for thermal CVD SiNx prepared at 750 °C. Finally, complementary MOSFETs (CMOSs) of single-crystalline Si were fabricated by using Cat-CVD poly-Si for gate electrodes and SiNx films for masks of local oxidation of silicon (LOCOS). At 3.3 V operation, less than 1.0 pA μm−1 of OFF leakage current and ON/OFF ratio of 107–108 are realized, i.e. the devices can operate similarly to conventional thermal CVD process. 相似文献
9.
In keeping with the advance of more compact and more power-saving electronic equipment, the demand is increasing for smaller and more efficient switching power supply. Therefore, it is necessary to provide the adequate magnetic power ferrite materials to satisfy the demand. Such ferrite materials have to meet the following main requirement: 1) high initial permeability (μ i ); 2) high saturation magnetic induction (Bs); 3) high Curie temperature (Tc); 4) high electrical resistivity (ρ ); 5)… 相似文献
10.
N. I. Bobyr’ A. P. Grabovskii A. V. Timoshenko A. P. Khalimon 《Strength of Materials》2006,38(1):92-98
Within framework of the continual fracture mechanics, we describe the engineering approach to the assessment of scattered
microdamage accumulation kinetics in metallic materials under elastoplastic loading conditions in case of plane stressed state.
Automatized experimental stand and the respective investigation technique are discussed. The stand has been developed based
on modification of the UMé-10T electromechanic test machine. State-of-the-art computer technologies and microprocessing hardware
are incorporated in the stand automation. We present the technique of experimental assessment of damage accumulation kinetics
in metallic structural materials under complex elastoplastic loading conditions with account of two different fracture (cleavage
and shear) processes, which technique is based on measuring the specific electric resistance of the specimen.
__________
Translated from Problemy Prochnosti, No. 1, pp. 128–137, January–February, 2006. 相似文献