全文获取类型
收费全文 | 10058篇 |
免费 | 233篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 115篇 |
综合类 | 6篇 |
化学工业 | 1986篇 |
金属工艺 | 209篇 |
机械仪表 | 164篇 |
建筑科学 | 544篇 |
矿业工程 | 17篇 |
能源动力 | 279篇 |
轻工业 | 838篇 |
水利工程 | 70篇 |
石油天然气 | 22篇 |
武器工业 | 2篇 |
无线电 | 690篇 |
一般工业技术 | 1458篇 |
冶金工业 | 2358篇 |
原子能技术 | 81篇 |
自动化技术 | 1463篇 |
出版年
2021年 | 94篇 |
2020年 | 82篇 |
2019年 | 130篇 |
2018年 | 119篇 |
2017年 | 115篇 |
2016年 | 147篇 |
2015年 | 137篇 |
2014年 | 182篇 |
2013年 | 521篇 |
2012年 | 330篇 |
2011年 | 468篇 |
2010年 | 375篇 |
2009年 | 356篇 |
2008年 | 442篇 |
2007年 | 394篇 |
2006年 | 361篇 |
2005年 | 316篇 |
2004年 | 288篇 |
2003年 | 266篇 |
2002年 | 285篇 |
2001年 | 163篇 |
2000年 | 155篇 |
1999年 | 176篇 |
1998年 | 304篇 |
1997年 | 264篇 |
1996年 | 208篇 |
1995年 | 192篇 |
1994年 | 210篇 |
1993年 | 182篇 |
1992年 | 151篇 |
1991年 | 121篇 |
1990年 | 136篇 |
1989年 | 145篇 |
1988年 | 114篇 |
1987年 | 98篇 |
1986年 | 136篇 |
1985年 | 159篇 |
1984年 | 147篇 |
1983年 | 142篇 |
1982年 | 138篇 |
1981年 | 152篇 |
1980年 | 120篇 |
1979年 | 120篇 |
1978年 | 91篇 |
1977年 | 133篇 |
1976年 | 140篇 |
1975年 | 127篇 |
1974年 | 80篇 |
1973年 | 95篇 |
1972年 | 77篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Improvement of WAXD patterns from aligned glassy polymers by a numerical desmearing technique is reported. This gives a fibre type diffraction pattern that can be more easily interpreted than radial or cylindrical distribution functions. Application to atactic and quenched isotactic polystyrene shows that the molecular conformations that are found are in agreement with those deduced from i.r. and n.m.r. spectroscopy. For isotactic polystyrene there is significant agreement between the fibre pattern of the aligned glassy polymer and that of the drawn crystalline polymer. 相似文献
82.
A. Gordon Robertson David S. Wilkinson Carlos H. Cáceres 《Journal of the American Ceramic Society》1991,74(5):915-921
The creep and creep fracture behavior of two hot-pressed aluminas are presented, for both flexural and tensile testing. Steady-state power-law creep is observed with a stress exponent of about 2 for each material. Three distinct fracture regimes are found. At high stress in flexure, fracture occurs by slow crack growth with a high stress dependence of the failure time. At intermediate stresses, in both flexure and tension, creep fracture occurs by multiple microcracking after modest strains. Failure times exhibit a modest stress dependence (stress exponent of 2.5 in tension and 3 in flexure), with a constant failure strain equal to 0.09. The failure times are considerably longer in flexure than in tension, because of the constraint imposed on crack growth by the bending geometry. We conclude that flexure cannot be used for creep lifetime assessment, even in simple, single-phase materials such as Al2 O3 . At low stresses, in tension, failure also exhibits a modest stress dependence but with a much higher failure strain. The material shows the onset of super-plastic behavior. 相似文献
83.
Alan M. Lyons 《Polymer Engineering and Science》1991,31(6):445-450
The effects of particle composition and size distribution on the electrical properties of conductive adhesives were studied. Silver-plated glass and silver-plated nickel particles with both narrow (37-44 μm) and broad (< 44 μm) size distributions were dispersed in an epoxy matrix. In all cases, formulations incorporating narrow particle size distributions required greater concentrations of particles to exceed the percolation threshold for electrical conduction than when broad particle distributions were used. Differences between glass and nickel particles were observed and attributed to the higher density of nickel particles, as well as subtle variations in particle size distributions. 相似文献
84.
This study examines the effect of pitch concentration, rate of heating, soak temperature and time of soak upon the optical texture of cokes prepared from the co-carbonizations of a coal (Oxcroft-Clowne, NCB Rank 802) and three vitrains of NCB Rank 204, 801, 902 with Ashland A240 petroleum pitch. Using the coal (Rank 802) with 10 wt % and 25 wt % additions of pitch caused progressive penetration of the pitch into the coal with a resultant development of a mozaic anisotropy in the coke to replace partially the original coke isotropy. With 50 wt % addition of pitch almost all of the coal particles, 600 to 1100 μm in size, were modified during carbonization. Some pitch coke was formed. For the coal and three vitrains with increasing rates of co-carbonization from 0.5–10 K min?1 to 1200 K, using 25 wt % of A240 pitch, resultant cokes showed progressively increased extents of modification. For the two vitrains (Rank 801, 902) soaking at temperatures of 650–690 K caused a decrease in the extent of modification of isotropic coke when compared with the coke of HTT 1200 K. Evidently fast heating rates create the conditions of fluidity necessary for the pitch to modify the coal leading to growth of mesophase and anisotropic coke. 相似文献
85.
Chatterjee Abhishek Ghaednia Hamid Bowling Alan Brake Matthew 《Multibody System Dynamics》2021,51(1):45-90
Multibody System Dynamics - Collision between hard objects causes abrupt changes in the velocities of the system, which are characterized by very large contact forces over very small time... 相似文献
86.
The adoption of two-shifting in coal-fired power generation (switching from on-load to off-load conditions on a daily basis and off-load for the weekend) results in regular cycling of the solution chemistry of the condensed steam on the turbine discs. A first stage investigation has been made of the effect of such chemistry cycling on the corrosion potential of the disc steel. The corrosion potential is typically about +0.05 V (SCE) in off-load chemistry (aerated pure water) and below −0.6 V (SCE) in on-load chemistry (deaerated solution containing chloride or chloride and sulphate anions). The critical observation was the sluggish response of the corrosion potential upon restoration of deaerated on-load conditions with the implication of a likely increase in pit and stress corrosion crack development. 相似文献
87.
Gordon D. Gemmell Nicholas J. Grant 《JOM Journal of the Minerals, Metals and Materials Society》1957,9(4):417-423
The effects of solid solution alloying on the creep-rupture properties, deformation characteristics, ductility, and fracture of pure aluminum were studied by means of creep-rupture tests on polished specimens of three alloys each of Al-Cu (0.24, 0.79, and 2.05 pct Cu), Al-Zn (4.93, 9.89, and 19.78 pct Zn), and Al-Mg (0.94, 1.92, and 5.10 pct Mg) at 500°, 700°, and 900°F. 相似文献
88.
89.
90.
Abstract Previous research shows that although collaboration technology can improve the exchange of information during team decision making, one of the challenges is that this better discussion often does not lead to better decisions. In this paper, we investigate the impact of individual information processing on team decision making. We investigated the effects of two types of collaboration technology when participants were either the member of a team majority or a team minority. There was little impact due to the majority/minority, but the use of collaboration technology that required users to categorize the comments they received from others resulted in increased information processing, which in turn led to better decisions and more satisfied participants. 相似文献