全文获取类型
收费全文 | 2457篇 |
免费 | 190篇 |
国内免费 | 2篇 |
学科分类
工业技术 | 2649篇 |
出版年
2023年 | 22篇 |
2022年 | 18篇 |
2021年 | 94篇 |
2020年 | 69篇 |
2019年 | 81篇 |
2018年 | 95篇 |
2017年 | 85篇 |
2016年 | 90篇 |
2015年 | 101篇 |
2014年 | 128篇 |
2013年 | 289篇 |
2012年 | 123篇 |
2011年 | 116篇 |
2010年 | 130篇 |
2009年 | 116篇 |
2008年 | 73篇 |
2007年 | 56篇 |
2006年 | 53篇 |
2005年 | 47篇 |
2004年 | 51篇 |
2003年 | 41篇 |
2002年 | 40篇 |
2001年 | 32篇 |
2000年 | 43篇 |
1999年 | 32篇 |
1998年 | 70篇 |
1997年 | 63篇 |
1996年 | 45篇 |
1995年 | 27篇 |
1994年 | 32篇 |
1993年 | 29篇 |
1992年 | 24篇 |
1991年 | 21篇 |
1990年 | 10篇 |
1989年 | 12篇 |
1988年 | 12篇 |
1987年 | 15篇 |
1986年 | 17篇 |
1985年 | 22篇 |
1984年 | 21篇 |
1983年 | 24篇 |
1982年 | 14篇 |
1981年 | 28篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1977年 | 9篇 |
1976年 | 20篇 |
1975年 | 10篇 |
1974年 | 11篇 |
1973年 | 9篇 |
排序方式: 共有2649条查询结果,搜索用时 281 毫秒
51.
52.
53.
54.
55.
56.
57.
Branko Mitrović 《Nexus Network Journal》2013,15(1):51-62
Nelson Goodman’s highly influential book Languages of Art argued that that all visual experience is merely a cultural construct. In presenting his thesis Goodman relied on a series of geometrical arguments intended to show that the geometrical construction of perspective does not rely on the geometry of light rays. In this article I analyze the geometrical validity of Goodman’s arguments. 相似文献
58.
Taekeun Kim Tianyuan Xie Won Suk Jung Branko N. Popov 《International Journal of Hydrogen Energy》2017,42(17):12507-12520
A highly active and stable catalyst/support system is developed by using a two-step process. In the first step, activated carbon composite support (ACCS) is synthesized that retains its activity after accelerated stress test (AST). A 30% Pt/ACCS catalyst shows no loss of mass activity and power density after 5000 cycles at 1.0–1.5 V while the commercial Pt/C and Pt/290G catalysts show drastic mass activity losses (57.5% and 66.2%, respectively) and power density losses (88.7% and 84.0%, respectively). In the second step, Pt catalyst with a compressive Pt lattice (Pt1) is synthesized through a USC-developed annealing procedure in which Co atoms previously embedded in the support diffuse into Pt. The 30% Pt1/ACCS shows high initial power density (rated) of 0.174 gPt kW?1 and high stability of 24 mV loss at 0.8 A cm?2 with an electrochemical active surface area (ECSA) loss of 42% after 30,000 cycles (0.6–1.0 V). The support stability under 1.0–1.5 V potential cycling shows potential loss of 8 mV at 1.5 A cm?2 and ECSA loss of 22% after 5000 cycles. Improved stability and activity of Pt*/ACCS catalyst are due to synergistic effect of catalytic activity and stability of ACCS and formation of compressive Pt lattice catalyst. 相似文献
59.
D. Volochová P. Diko M. Radušovská S. Piovarči V. Antal K. Zmorayová M. Šefčiková 《Journal of Superconductivity and Novel Magnetism》2013,26(4):885-889
The TSMG process of YBCO bulk superconductors with Y1.5Ba2Cu3O x composition and 1 wt% CeO2 addition has been studied. It is shown that the window for isothermal growth of single-crystalline sample grown from Sm123 seed is between 988 °C and 1003 °C. At lower temperatures of this window, Y123 crystals grow with higher growth rate but the quality of crystals is worse due to the formation of steps at the growth front. During an isothermal dwell at the optimized temperature, the growth of Y123 single-crystal stops due to decreasing peritectic temperature with increasing CuO concentration in the melt. Additional slow cooling 1 °C/hour from the temperature of isothermal growth leads to epitaxial growth of Y123 crystal over the entire sample. Only very narrow part at the rim of the sample contains CuO phase and blocky Y123 crystals are formed there due to self-nucleation. 相似文献
60.
The paper deals with an experimental determination of the stretch zone dimensions in the notch tip in thin steel sheets. The stretch zone dimensions depend on steel grade, on the rolling direction as well as on the loading rate. Stretch zones were observed and measured on three steel grades. Fracture area and stretch zones were analysed by SEM. Stable crack growth was monitored by videoextensometry techniques on CT (Compact Tension) specimens. Specimens were loaded under two loading rates by eccentric tension, whereby the deformation in the notch surrounding area was recorded using a non-contact measurement–videoextensometry technique. Linear relation between the stretch zone dimensions was determined. 相似文献