全文获取类型
收费全文 | 3792篇 |
免费 | 119篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 44篇 |
综合类 | 4篇 |
化学工业 | 818篇 |
金属工艺 | 109篇 |
机械仪表 | 76篇 |
建筑科学 | 108篇 |
矿业工程 | 9篇 |
能源动力 | 115篇 |
轻工业 | 177篇 |
水利工程 | 28篇 |
石油天然气 | 10篇 |
无线电 | 334篇 |
一般工业技术 | 747篇 |
冶金工业 | 834篇 |
原子能技术 | 31篇 |
自动化技术 | 484篇 |
出版年
2023年 | 20篇 |
2022年 | 37篇 |
2021年 | 71篇 |
2020年 | 57篇 |
2019年 | 52篇 |
2018年 | 74篇 |
2017年 | 65篇 |
2016年 | 81篇 |
2015年 | 55篇 |
2014年 | 79篇 |
2013年 | 211篇 |
2012年 | 120篇 |
2011年 | 167篇 |
2010年 | 151篇 |
2009年 | 168篇 |
2008年 | 139篇 |
2007年 | 135篇 |
2006年 | 121篇 |
2005年 | 113篇 |
2004年 | 125篇 |
2003年 | 95篇 |
2002年 | 95篇 |
2001年 | 92篇 |
2000年 | 73篇 |
1999年 | 81篇 |
1998年 | 183篇 |
1997年 | 112篇 |
1996年 | 89篇 |
1995年 | 66篇 |
1994年 | 73篇 |
1993年 | 84篇 |
1992年 | 66篇 |
1991年 | 53篇 |
1990年 | 51篇 |
1989年 | 64篇 |
1988年 | 46篇 |
1987年 | 35篇 |
1986年 | 41篇 |
1985年 | 48篇 |
1984年 | 46篇 |
1983年 | 44篇 |
1982年 | 25篇 |
1981年 | 28篇 |
1980年 | 35篇 |
1979年 | 25篇 |
1978年 | 23篇 |
1977年 | 34篇 |
1976年 | 36篇 |
1974年 | 19篇 |
1973年 | 26篇 |
排序方式: 共有3928条查询结果,搜索用时 0 毫秒
21.
The ability of rotorcraft to fly at low altitude is hindered by the high pilot workload required to avoid obstacles. The development of automation tools that can detect obstacles in the rotorcraft flight path, warn the crew, and interact with the guidance system to avoid detected obstacles would significantly reduce pilot workload and increase safety. This article describes an obstacle detection approach based on feature tracking and recursive range estimation that takes into account the characteristics of rotorcraft flight. The merits and weaknesses of the approach are discussed using image sequences from the laboratory and from flight. © 1992 John Wiley & Sons, Inc. 相似文献
22.
Ray P. S. Han Kai-Yuan Yeh Guoli Liu Diankui Liu 《International Journal of Engineering Science》1992,30(12):1773-1787
The scattering and diffraction of plane SH-waves, by an arbitrary-shaped cylindrical canyon in anisotropic media is formulated here. Analytical solutions are obtained via the complex function theory, using the orthogonal property of the Hermite functions to solve the resulting set of infinite algebraic equations. Expressions for scattered displacements and scattered stresses are given. Three cross-sectional profile types are used in the numerical simulation of the two-dimensional canyon topography: (a) a semi-circular profile, (b) a semi-elliptical profile and (c) a triangular profile. The results obtained in (a) and (b) are consistent with known solutions computed by Trifunac and his co-workers [1,3] using a different method. As the exact solution for (c) is not known to exist, the result given here is believed to be new and would therefore serve as a useful check for numerical analysts working in this area. 相似文献
23.
The deformation behavior of several single- and two-phase coarse microstructures has been examined using microhardness measurements.
It has been found that the strength response of a coarse phase in isolation is distinctly different from its response when
it exists in a two-phase system. The second phase alters the mechanical state of the first one andvice versa even in the plastically undeformed condition. This phenomenon is explained in terms of the existence of an appreciable amount
of residual stresses in two-phase coarse microstructures. These stresses primarily arise due to the difference in thermal
expansion coefficients of the phases. The in- fluence of elastic stress field on microhardness response is shown with a new
type of experiment to support the proposed explanation. The present results question the existing expressions for deformation
modeling of multiphase materials because of the uncertainties in the estimation of the average strength of the phases in a
two-phase system. 相似文献
24.
S. P. Ray 《Metallurgical and Materials Transactions A》1992,23(9):2381-2385
25.
The simultaneous contrast effect is investigated in this article. A total of 174 and 154 test/induction combinations were studied for CRT and surface colours respectively. Each combination was assessed by nine observers using a matching technique. The test and induction colours used for CRT colours were similar to surface colours using fabric samples. The results indicated a strong lightness contrast effect for both CRT and surface media; that is, the lightness of a test colour surrounded by a lighter induction colour was reduced for both CRT and surface colours. However, the effect in CRT medium was more pronounced than in the surface medium. © 2004 Wiley Periodicals, Inc. Col Res Appl, 30, 13–20, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20074 相似文献
26.
Combinations of EDTA-Tris and two aminoglycoside antibiotics (amikacin and neomycin) were tested for synergistic activities against the microorganisms associated with otitis externa in dogs and for the solutions' stability over time. Synergistic activity was observed when EDTA-Tris plus amikacin and EDTA-Tris plus neomycin were tested against Staphylococcus intermedius, Proteus mirabilis, Pseudomonas aeruginosa, and Escherichia coli, but not against Candida albicans. Stability studies over a 3-month period indicated that the test solutions were stable at room temperature and that their antimicrobial activity was maintained. 相似文献
27.
28.
A necessary and sufficient condition for the union of an arbitrary family of fuzzy subgroups of a group to be a fuzzy group has been proposed. The criterion which gives a cut of the unit interval is called the Schnittaxiom. It has been applied successfully to investigate fuzzy subgroupness of arbitrary unions of homomorphic images and preimages. 相似文献
29.
W. Harmon Ray 《加拿大化工杂志》1991,69(3):626-629
A brief review of addition polymerization processes is presented with a summary of the key characteristics classified by kinetic mechanism (free-radical, anionic, cationic, group transfer, or Ziegler–Natta), phase behavior, and reactor type. A practical approach to modelling in the industrial R & D environment is discussed in terms of a CAD package for polymerization processes. 相似文献
30.