全文获取类型
收费全文 | 953篇 |
免费 | 3篇 |
专业分类
电工技术 | 7篇 |
化学工业 | 9篇 |
金属工艺 | 3篇 |
机械仪表 | 6篇 |
轻工业 | 5篇 |
水利工程 | 5篇 |
石油天然气 | 8篇 |
无线电 | 6篇 |
一般工业技术 | 22篇 |
冶金工业 | 870篇 |
原子能技术 | 3篇 |
自动化技术 | 12篇 |
出版年
2021年 | 3篇 |
2020年 | 4篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2014年 | 5篇 |
2013年 | 7篇 |
2012年 | 4篇 |
2011年 | 4篇 |
2009年 | 3篇 |
2008年 | 3篇 |
2006年 | 3篇 |
2005年 | 2篇 |
2004年 | 2篇 |
2002年 | 1篇 |
2001年 | 1篇 |
1999年 | 10篇 |
1998年 | 177篇 |
1997年 | 118篇 |
1996年 | 94篇 |
1995年 | 54篇 |
1994年 | 58篇 |
1993年 | 49篇 |
1992年 | 13篇 |
1991年 | 5篇 |
1990年 | 10篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 17篇 |
1980年 | 19篇 |
1979年 | 1篇 |
1978年 | 9篇 |
1977年 | 98篇 |
1976年 | 129篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1962年 | 1篇 |
1954年 | 1篇 |
1899年 | 1篇 |
排序方式: 共有956条查询结果,搜索用时 484 毫秒
951.
952.
VR Ermolaev GM Shub EP Kusina GL Polianski? VI Sobolev 《Canadian Metallurgical Quarterly》1976,10(3):53-58
Recovery of spatial resolving capacity (acuity) of central vision after temporary blindness induced by prolonged (1.5, 3, 6 min) light adaptation to a sun or incandescence lamp (20, 40, 80 thous. lux) illuminated white screen was studied. The recovery time increased exponentially with an increase in energy light stimulation (product of brightness of the deadapting source by the time of action). A general formula describing the relationship between the time of recovery of acuity and brightness of the test table and energy of light stimulus was derived. 相似文献
953.
954.
We review a free parameter in the design of Fresnel zone plate lens antennas. Historically, zone plate antennas have been
designed with a specific choice for this parameter, which can be taken as a type of phase reference. Two methods of interpreting
the parameter have been identified, either in terms of a reference radius or equivalently a reference phase. Here, for simplicity, we treat this variable parameter as a reference phase. Importantly, the reference phase can be chosen
to have non-standard values which have been shown to improve important aspects of antenna performance and to add a new functionality
to zone plate antennas. 相似文献
955.
FJ. Guzmán-Osorio VI. Domínguez-Rodríguez RH. Adams CE. Lobato-García A. Guerrero-Peña JR. Barajas-Hernández 《Egyptian Journal of Petroleum》2021,30(2):63-67
A method was developed for classifying petroleum into four types according to their origin and integrity: marine, non-marine, degraded and thermally transformed. The method was based on the relative proportions of functional groups measured by FTIR spectroscopy. Twenty-one petroleum samples were used for model calibration and six for validation, which were pre-classified. Aliphatic functional group absorption maxima were used at 2919, 2856, 1457 and 1376 cm?1, as well as at 1700 and 811 cm?1 for aromatic groups, and at 1152 and 1030 cm?1 for polar groups (sulphonyl and ether, respectively). Using hierarchical cluster and discriminate analyses, three canonic functions were obtained that classified the samples according to their origin and integrity, with a prediction efficiency of 100%, for both calibration and validation. The canonic functions derived from the discriminate analysis had correlation coefficients of 0.994, 0.900, and 0.867, among the variables studied and the classification factor. The method is efficient for the proposed classifications and can be useful for a range of applications. 相似文献
956.
Registration of contractility of the upper urinary tracts (UUT) at multichannel impedance ureterography was conducted in 30 patients with concrements in the kidneys and ureters before extracorporeal lithotripsy. By defects in urodynamics, the patients were divided into 4 groups. The most severe affection of urodynamics (low amplitude of the peristalsis, high tonicity of UUT wall) occurred in group 4. From group 1 to 4 contraction arrhythmia, deformity of contraction complexes, retrograde contraction waves were increasing. The index has been calculated for estimation of UUT performance in transporting urine. 相似文献