全文获取类型
收费全文 | 3135篇 |
免费 | 105篇 |
国内免费 | 40篇 |
专业分类
电工技术 | 105篇 |
综合类 | 39篇 |
化学工业 | 795篇 |
金属工艺 | 67篇 |
机械仪表 | 139篇 |
建筑科学 | 113篇 |
矿业工程 | 23篇 |
能源动力 | 99篇 |
轻工业 | 273篇 |
水利工程 | 26篇 |
石油天然气 | 11篇 |
武器工业 | 2篇 |
无线电 | 276篇 |
一般工业技术 | 446篇 |
冶金工业 | 300篇 |
原子能技术 | 45篇 |
自动化技术 | 521篇 |
出版年
2024年 | 2篇 |
2023年 | 13篇 |
2022年 | 53篇 |
2021年 | 68篇 |
2020年 | 28篇 |
2019年 | 55篇 |
2018年 | 68篇 |
2017年 | 45篇 |
2016年 | 60篇 |
2015年 | 63篇 |
2014年 | 85篇 |
2013年 | 169篇 |
2012年 | 144篇 |
2011年 | 218篇 |
2010年 | 199篇 |
2009年 | 206篇 |
2008年 | 219篇 |
2007年 | 186篇 |
2006年 | 145篇 |
2005年 | 166篇 |
2004年 | 100篇 |
2003年 | 107篇 |
2002年 | 105篇 |
2001年 | 68篇 |
2000年 | 57篇 |
1999年 | 47篇 |
1998年 | 76篇 |
1997年 | 61篇 |
1996年 | 51篇 |
1995年 | 37篇 |
1994年 | 37篇 |
1993年 | 47篇 |
1992年 | 36篇 |
1991年 | 25篇 |
1990年 | 24篇 |
1989年 | 17篇 |
1988年 | 25篇 |
1987年 | 24篇 |
1986年 | 11篇 |
1985年 | 24篇 |
1984年 | 18篇 |
1983年 | 19篇 |
1982年 | 11篇 |
1981年 | 20篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1974年 | 4篇 |
1973年 | 3篇 |
排序方式: 共有3280条查询结果,搜索用时 15 毫秒
21.
Lee J. Hatcher G. Vandenberghe L. Chih-Kong Ken Yang 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2007,15(9):1017-1027
This paper presents a feasible study of fully-integrated switching voltage regulators for power-optimized systems-on-chip (SoCs). In order to evaluate the power efficiency across a number of design variables, a compact macro-model of a regulator is created and validated. A key focus of the study is on the characteristics of the active and passive devices that are needed in order to maximize the efficiency of an on-chip regulator. With the macro-model, geometric programming is used to find the optimal characteristics for a given set of constraints such as load condition, process technology, and area. The achievable efficiencies for various current loads and across a range of technologies from 0.35-mum to 90-nm CMOS process are analyzed. The power efficiency is found to be strongly dependent on the inductor technology and over 70% efficiency is possible with advanced inductor technologies. 相似文献
22.
Hydrothermal synthesis and in situ surface modification of boehmite nanoparticles in supercritical water 总被引:2,自引:1,他引:1
T. Mousavand S. Ohara M. Umetsu J. Zhang S. Takami T. Naka T. Adschiri 《The Journal of Supercritical Fluids》2007,40(3):397-401
In situ surface modification of boehmite (AlOOH) nanoparticles during hydrothermal synthesis in supercritical water was examined by adding CH3(CH2)4CHO and CH3(CH2)5NH2 as modifier reagents to the reactants. Changes in surface properties of the nanoparticles by surface modification was observed by FTIR, dispersion in solvents and TEM analyses, which demonstrated that reagents chemically binded onto the surface of the AlOOH nanoparticles. The results of SEM and TEM pictures show that the surface modification affects crystal growth and reduces the particle size and changes the morphology of the particles. 相似文献
23.
Ming-Ching Lee Chan-Ji Lai Jan-Mou Leu William J. Plant William C. Keller Ken Hayes 《Flow Measurement and Instrumentation》2002,13(5-6):265-270
This article describes a non-contact method for measuring surface velocity and discharge in a natural channel. The X-band pulse (9.36 GHz) radar, developed by the Applied Physics Laboratory of the University of Washington, was used to scan instantaneously the lateral distribution of surface velocity across a river section, according to Bragg scattering from short waves produced by turbulent boils on the surface of the river. Based on the assumption that the vertical velocity distribution follows a universal power or logarithmic law, the discharges were estimated. 相似文献
24.
25.
The interaction of alkali metal with surfaces has been of great interest to the community of catalysis since alkali metal can play an important role as a promoter. On alkali-doped MoS2, such a promotion effect of alkali metal has been exemplified in the direct synthesis of linear alcohols from CO and H2, where the alkali-doping switches the catalyst selectivity from methanation to alcohol synthesis. This paper reviews recent high-resolution X-ray photoelectron spectroscopy experiments that have provided direct
observation of electron transfer from alkali metals to a model single crystal MoS2 and the capture of the supra-valence electrons in the subsequent oxidation reactions. 相似文献
26.
Ken Kato Yasuhiro Kasuga Masanori Fujiwara Kazuo Onda 《Electrical Engineering in Japan》1996,116(4):94-108
Laboratory-scale and parametric experiments of SO2 and NOx removal from the simulated combustion gas by pulsed corona discharge have been performed by changing the combustion gas composition and temperature, the electrode configuration of plasma reactor, and the polarity of high-voltage electrode. The following results are obtained: 1) the higher the concentration of H2O and O2, the higher the efficiency of desulfurization and denitrification at the same specific input; 2) the pulsed corona discharge with a voltage pulsewidth as short as 200 ns of negative polarity shows the possibility to attain almost 90 percent deSOx and deNOx efficiency at the specific discharge input of 20 J/g, which is almost the same as the specific input in the electron-beam process; 3) the deNOx characteristics show a little temperature dependence in the range of 70 to 130°C, but the deSOx efficiency increases rapidly in the temperature region below 100°C suggesting the thermochemical dependence of deSOx reaction; 4) when desulfurization and denitrification proceed, the white dendritic powder deposits on the plasma reactor whose composition is identified to be 49 mol% (NH4)2SO4 and 47 mol% of 2NH4NO3 · (NH4)2SO4, and the ratio of SO2, NO and NH3 of the deposit is almost equal to that of supplied gas. 相似文献
27.
Birds' use of landmarks to identify spatial locations was examined. Black-capped chickadees (Parus atricapillus) and pigeons (Columba livia) searched for hidden food on a 120-cm–2 tray. In each task the target was near an edge with a nearby landmark. On occasional unrewarded tests the landmark was either left in its usual position, shifted parallel to the edge, shifted perpendicular to the edge, or shifted diagonally. On diagonal landmark shifts the birds shifted their searching more in the parallel direction than in the perpendicular, which violates the predictions of the vector sum model (K. Cheng, 1989). In some cases the birds maintained their searching at a constant perpendicular distance under all landmark shifts. This suggests that perpendicular distance to an edge forms an element in determining where to search on the basis of landmarks. Chickadees and pigeons performed similarly, which suggests similarity in the way they encode locations. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
28.
典型开关式电容器充电泵不需要电感器,因此容易设计.且能将正电压加倍及将正电压转换成一个等效负电压。但在某些应用中.只有正电源可用.且电源系统必须产生一个幅度比正电源电压幅度更大的负电压。图1所示电路可将其输入电压反相的同时将所得负电压加倍。 相似文献
29.
Ken Mattsson 《Journal of scientific computing》2003,18(1):133-153
Four different methods of imposing boundary conditions for the linear advection-diffusion equation and a linear hyperbolic system are considered. The methods are analyzed using the energy method and the Laplace transform technique. Numerical calculations are done, considering in particular the case when the initial data and boundary data are inconsistent. 相似文献
30.