全文获取类型
收费全文 | 104751篇 |
免费 | 9741篇 |
国内免费 | 5235篇 |
专业分类
电工技术 | 7869篇 |
技术理论 | 22篇 |
综合类 | 15695篇 |
化学工业 | 13953篇 |
金属工艺 | 6392篇 |
机械仪表 | 5497篇 |
建筑科学 | 12866篇 |
矿业工程 | 4038篇 |
能源动力 | 2978篇 |
轻工业 | 5630篇 |
水利工程 | 4571篇 |
石油天然气 | 4258篇 |
武器工业 | 767篇 |
无线电 | 10886篇 |
一般工业技术 | 9011篇 |
冶金工业 | 5126篇 |
原子能技术 | 772篇 |
自动化技术 | 9396篇 |
出版年
2024年 | 394篇 |
2023年 | 1213篇 |
2022年 | 2063篇 |
2021年 | 2390篇 |
2020年 | 2540篇 |
2019年 | 2254篇 |
2018年 | 2133篇 |
2017年 | 2813篇 |
2016年 | 3087篇 |
2015年 | 3567篇 |
2014年 | 7037篇 |
2013年 | 5673篇 |
2012年 | 7117篇 |
2011年 | 7544篇 |
2010年 | 5884篇 |
2009年 | 6611篇 |
2008年 | 6004篇 |
2007年 | 7767篇 |
2006年 | 7257篇 |
2005年 | 6105篇 |
2004年 | 5044篇 |
2003年 | 4446篇 |
2002年 | 3626篇 |
2001年 | 3148篇 |
2000年 | 2763篇 |
1999年 | 2082篇 |
1998年 | 1535篇 |
1997年 | 1307篇 |
1996年 | 1117篇 |
1995年 | 996篇 |
1994年 | 861篇 |
1993年 | 621篇 |
1992年 | 592篇 |
1991年 | 408篇 |
1990年 | 378篇 |
1989年 | 373篇 |
1988年 | 218篇 |
1987年 | 137篇 |
1986年 | 123篇 |
1985年 | 79篇 |
1984年 | 85篇 |
1983年 | 54篇 |
1982年 | 45篇 |
1981年 | 63篇 |
1980年 | 44篇 |
1979年 | 24篇 |
1978年 | 16篇 |
1977年 | 12篇 |
1975年 | 17篇 |
1951年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
V. A. Kazakov 《Measurement Techniques》2004,47(5):494-499
A method of measuring the current–voltage characteristics of nonlinear components is proposed, which involves applying a sinusoidal voltage to the object being measured, finding the Fourier spectrum to read out the output current, and a calculation using the spectrum of the coefficients of the expansion of the measured characteristic in Chebyshev polynomials. The properties of the Hammerstein–Chebyshev model are considered, a block diagram of a measuring instrument is presented, and recommendations are made for minimizing the systematic errors due to approximating their characteristics by Chebyshev polynomials. 相似文献
102.
G. SAID 《Fatigue & Fracture of Engineering Materials & Structures》2006,29(8):606-614
Costs of ASTM E399 and ASTM E1921 tests, which were developed to determine the fracture toughness (KIc) and the ductile–brittle transition temperature of ferritic steels, respectively, are considered high and the procedures are also very complicated. In this study, a method, which is more cost‐effective and easier to carry out, is proposed. 相似文献
103.
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
104.
Low carbon steel was oxidized over the temperature range 1000‐1250°C in O2‐CO2‐H2O‐N2, O2‐H2O‐N2, and O2‐CO2‐N2 gas mixtures. Oxidation times were 12‐120 min. and the scales were 50‐2000 μm thick. The variations of these parameters were chosen to elucidate the phase composition of oxide scales under conditions similar to those of reheating furnaces in hot strip mills, using either thin slab casting or conventional casting and rolling technology. Two types of scales have been observed which are influenced by the furnace atmosphere, oxidation time, and temperature. The first type is a crystalline scale with an irregular outer surface, composed mostly of wustite (FeO), and a negligible amount of magnetite (Fe3O4). The second type is the classical three‐layer scale, composed of wustite (FeO), magnetite (Fe3O4), and hematite (Fe2O3). In general, the experiments showed that an increase in oxidation time decreased the percentage of wustite while the percentages of magnetite and hematite increased. A rise in oxygen concentration in the gas mixture increased the percentages of magnetite and hematite, confirming earlier experimental findings. In water vapour‐free atmospheres O2‐CO2‐N2, the oxide scales had a low percentage of wustite, and high percentage of magnetite and hematite. Carbon dioxide showed a small influence at 1100°C, and a negligible one at 1250°C. 相似文献
105.
The free energies of mixing of two networks in the interpenetrating polymer network based on crosslinked polyurethane and poly(ester acrylate) have been determined by the vapour sorption method. It was established that the constituent networks in the IPN are not miscible. The introduction of fillers of different chemical nature increases the compatibility. The thermodynamic affinity of the fillers to the individual networks and IPN was estimated. It was established that when the free energy of interaction of one or both components of the IPN with the filler is negative, reinforcement leads to the formation of a compatible and equilibrium system. For fillers having no affinity to the polymers, compatibilization is observed, which is connected with slowing down of phase separation in the system in the presence of filler. 相似文献
106.
107.
Undoped and Te-doped gallium antimonide (GaSb) layers have been grown on GaSb bulk substrates by the liquid phase epitaxial
technique from Ga-rich and Sb-rich melts. The nucleation morphology of the grown layers has been studied as a function of
growth temperature and substrate orientation. MOS structures have been fabricated on the epilayers to evaluate the native
defect content in the grown layers from theC-V characteristics. Layers grown from antimony rich melts always exhibitp-type conductivity. In contrast, a type conversion fromp- ton- was observed in layers grown from gallium rich melts below 400 C. The electron mobility of undopedn-type layers grown from Ga-rich melts and tellurium doped layers grown from Sb- and Ga-rich solutions has been evaluated.
Paper presented at the poster session of MRSI AGM VI. Kharagpur. 1995 相似文献
108.
Precusors to the YBa2 Cu3 O7-δ material were prepared by both the oxalate precipitation method and conventional ceramic processing. Second-phase grains were observed to develop on the exposed fracture surface during annealing at 500° to 600°C in an ambient atmosphere. The second-phase grains were identified to be BaCO3 using EDX and XRD. The liquid phase, which was formed because of local chemical inhomogeneity in the Y-Ba-Cu-O system, contributed to the formation of second-phase grains as a source of Ba. 相似文献
109.
全文围绕树立和落实科学发展观这一主题 ,研究和探索如何在新时期、新阶段进一步做好国土资源管理工作的新思路、新途径和新方法。提出要进一步加强国土资源宏观管理 ,更好地为甘肃省经济社会的协调、可持续发展提供保障服务。 相似文献
110.