全文获取类型
收费全文 | 260757篇 |
免费 | 4272篇 |
国内免费 | 1820篇 |
专业分类
电工技术 | 5413篇 |
技术理论 | 5篇 |
综合类 | 1164篇 |
化学工业 | 42036篇 |
金属工艺 | 11020篇 |
机械仪表 | 7741篇 |
建筑科学 | 6590篇 |
矿业工程 | 1660篇 |
能源动力 | 5591篇 |
轻工业 | 25795篇 |
水利工程 | 2889篇 |
石油天然气 | 5998篇 |
武器工业 | 243篇 |
无线电 | 27783篇 |
一般工业技术 | 49182篇 |
冶金工业 | 47216篇 |
原子能技术 | 5616篇 |
自动化技术 | 20907篇 |
出版年
2021年 | 2475篇 |
2019年 | 2120篇 |
2018年 | 3385篇 |
2017年 | 3357篇 |
2016年 | 3683篇 |
2015年 | 2798篇 |
2014年 | 4578篇 |
2013年 | 11351篇 |
2012年 | 7685篇 |
2011年 | 10190篇 |
2010年 | 8113篇 |
2009年 | 8666篇 |
2008年 | 9471篇 |
2007年 | 9585篇 |
2006年 | 8431篇 |
2005年 | 7385篇 |
2004年 | 6654篇 |
2003年 | 6200篇 |
2002年 | 6208篇 |
2001年 | 6318篇 |
2000年 | 5906篇 |
1999年 | 5875篇 |
1998年 | 12856篇 |
1997年 | 9535篇 |
1996年 | 7277篇 |
1995年 | 5526篇 |
1994年 | 5083篇 |
1993年 | 4948篇 |
1992年 | 3943篇 |
1991年 | 3751篇 |
1990年 | 3823篇 |
1989年 | 3770篇 |
1988年 | 3530篇 |
1987年 | 3021篇 |
1986年 | 3050篇 |
1985年 | 3408篇 |
1984年 | 3321篇 |
1983年 | 3074篇 |
1982年 | 2698篇 |
1981年 | 2902篇 |
1980年 | 2643篇 |
1979年 | 2839篇 |
1978年 | 2736篇 |
1977年 | 2842篇 |
1976年 | 3694篇 |
1975年 | 2457篇 |
1974年 | 2290篇 |
1973年 | 2320篇 |
1972年 | 1981篇 |
1971年 | 1785篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
J. T. DICKINSON L. C. JENSEN W. DAVID WILLIAMS 《Journal of the American Ceramic Society》1985,68(5):235-240
We present measurements of the electron, positive ion, and photon emission accompanying the fracture in vacuum of poly-crystalline 95/5 lead zirconate-titanate. The intensities of the charged-particle components of this fractoemission are shown to depend strongly on the direction (relative to the direction of fracture) and magnitude of polarization. The most intense emission is observed when the fracture surfaces are perpendicular to the polarization direction. The emission intensity increases monotonically with polarization. These results are interpreted in terms of a model involving charge separation on the fracture surfaces leading to a microdischarge during fracture. Implications to the interpretation of triboluminesence effects are discussed. 相似文献
172.
A. J. Hugo D. M. Jakelski G. Stanitsas G. R. Sullivan R. R. Hudgins P. L. Silveston 《加拿大化工杂志》1986,64(2):349-351
In the approach to a cycle-invariant state in the forced feed concentration cycling of the CO oxidation over a NiO catalyst, a very long transient has been observed lasting 80 ks or more. This transient appears to be associated only with CO pretreatment of the catalyst and is not a general phenomenon. The slow convergence to the cycle-invariant state reported in certain modelling calculations in the literature appears to have a different cause. 相似文献
173.
The comfort diagrams and the so-called PMV-PPD values are already used today directly and indirectly in a wide field in technical practice, even at a standard level. This theory is known also in Hungary, and the PMV-PPD values have been used by us for the solution of a design problem. The task was to elaborate a calculation method, an index number suitable for the determination of the thermal confort effect in the case of occasional underheating of residential and communal buildings in winter.The results of this work are presented in this paper. 相似文献
174.
Sarto M.S. Voti R.L. Sarto F. Larciprete M.C. 《Electromagnetic Compatibility, IEEE Transactions on》2005,47(3):602-611
New nanolayered coatings are designed and deposited on flexible plastic substrate having the thickness of 100 /spl mu/m, in order to realize lightweight ultrathin transparent shielding foils. The structure of the coating is optimized considering three figures of merit: the average transmittance in the visible range for normal incidence, the normalized average transmittance for oblique incidence at 550 nm, and the transmittance quality factor. The nanotechnology exploited for the deposition of the transparent metals is the dual ion beam sputtering. Tests of durability, optical transmission, and shielding effectiveness demonstrate that the film has a high adhesion under mechanical solicitation, high resistance against aging, peak transmittance in the visible range higher than 70%, omnidirectional properties in the range 0/spl deg/-60/spl deg/, and shielding effectiveness of 40 dB up to 6 GHz. 相似文献
175.
176.
Tested the ability of 4 adult male Sprague-Dawley rats to use odors in discrimination among littermates living as a group. Ss were trained in a Y-maze to discriminate the presence of a littermate from its absence. Results from transfer of training in 3 subsequent testing periods indicated that the animals were capable of distinguishing among individuals when relatedness and familiarity were held constant, that this ability was not due to training, and that performance was based solely on odor cues. Results suggest that laboratory rats exhibit odor sensitivities conmensurate with very complex social processes. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
177.
The composition of the Co-Cr-Mo alloy has been modified by additions of nickel and some trace elements aluminium, titanium and boron. In this paper, the first part of the present study, the effects of alloy additions on the microstructures and tensile properties of the as-cast Co-Cr-Mo alloy are discussed. The effects of alloy additions on the fatigue behaviour of the alloy will be discussed in the second part of the present study. It is found that alloy additions do not seem to result in changes in the nature of the casting structure. A directional, coarse dendritic cast structure is produced in the modified alloys as in the base alloY. However, the alloy additions affect the carbide precipitations and the formation of some fine details of the microstructure such as dislocations, stacking faults and twins produced during the solidification. A considerable improvement in the transient mechanical properties, especially in the tensile ductility, is achieved by modifying the base alloy with alloy additions. 相似文献
178.
L. Vandewalle 《Journal of Materials Science Letters》1989,8(2):147-149
179.
180.
L. B. Getsov A. Ya. Madorskii N. N. Mozzhukhina A. G. Tereshchenko E. E. Yushchenkov 《Strength of Materials》1989,21(1):92-98
Leningrad. Translated from Problemy Prochnosti, No. 1, pp. 71–76, January, 1989. 相似文献