全文获取类型
收费全文 | 46232篇 |
免费 | 5011篇 |
国内免费 | 3376篇 |
专业分类
电工技术 | 3634篇 |
技术理论 | 1篇 |
综合类 | 4468篇 |
化学工业 | 6522篇 |
金属工艺 | 3223篇 |
机械仪表 | 2099篇 |
建筑科学 | 2944篇 |
矿业工程 | 2036篇 |
能源动力 | 2193篇 |
轻工业 | 3233篇 |
水利工程 | 1292篇 |
石油天然气 | 2619篇 |
武器工业 | 645篇 |
无线电 | 5191篇 |
一般工业技术 | 4580篇 |
冶金工业 | 3052篇 |
原子能技术 | 1051篇 |
自动化技术 | 5836篇 |
出版年
2024年 | 157篇 |
2023年 | 625篇 |
2022年 | 1189篇 |
2021年 | 1433篇 |
2020年 | 1619篇 |
2019年 | 1456篇 |
2018年 | 1377篇 |
2017年 | 1867篇 |
2016年 | 1989篇 |
2015年 | 2001篇 |
2014年 | 2952篇 |
2013年 | 3324篇 |
2012年 | 3585篇 |
2011年 | 3672篇 |
2010年 | 2748篇 |
2009年 | 2650篇 |
2008年 | 2451篇 |
2007年 | 2988篇 |
2006年 | 2494篇 |
2005年 | 2132篇 |
2004年 | 1877篇 |
2003年 | 1636篇 |
2002年 | 1368篇 |
2001年 | 1189篇 |
2000年 | 1011篇 |
1999年 | 821篇 |
1998年 | 687篇 |
1997年 | 611篇 |
1996年 | 539篇 |
1995年 | 453篇 |
1994年 | 360篇 |
1993年 | 267篇 |
1992年 | 258篇 |
1991年 | 188篇 |
1990年 | 158篇 |
1989年 | 106篇 |
1988年 | 77篇 |
1987年 | 50篇 |
1986年 | 44篇 |
1985年 | 39篇 |
1984年 | 38篇 |
1983年 | 20篇 |
1982年 | 18篇 |
1981年 | 17篇 |
1980年 | 18篇 |
1979年 | 4篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1975年 | 10篇 |
1959年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
131.
Yu. V. Balaban-Irmenin N. G. Fokina 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2007,41(5):306-312
The effect of internal-corrosion inhibitors on heating-system pipelines is investigated. Tests were conducted on a testing
device for polarization measurements under conditions corresponding to the Rostov Heat-Supply System. The concentration of
OEDP-zinc, which provides a high degree of protection from general corrosion, is determined. The reagent has been successfully
incorporated into the Rostov No. 2 TPP.
__________
Translated from élektricheskie Stantsii, No. 7, July 2007, pp. 37–43. 相似文献
132.
In various medium‐to‐large‐scale fire test equipments like the ISO room corner test (RC), and more recently, the single burning item test (SBI) the mass flow rate measurement of the combustion gases plays a key role in the determination of the heat‐release rate and smoke‐production rate. With the knowledge of the velocity profile and the temperature of the flow, the mass flow rate is obtained by measuring the velocity on the axis of the duct. This is done by means of a bi‐directional probe based on the pitot principle. However, due to the variation of the mean temperature and the temperature gradient in any cross section of the duct, introduced by ever changing combustion gas temperatures, the velocity nor the density profile are constant in time. This paper examines the resulting uncertainty on the mass flow rate. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
133.
134.
R. P. Okatov F. K. Nizametdinov B. N. Tsai T. T. Bondarenko 《Journal of Mining Science》2003,39(2):139-142
Using the synthesis of the kinetic concept on solid strength and the Coulomb - Mohr strength theory as the base, the failure conditions taking into account the time and temperature factors are obtained. 相似文献
135.
136.
This paper compares state-space and input–output realizations for nonlinear discrete-time dynamic models. For linear models, these two realizations are essentially equivalent and their structures are closely related, but these statements do not hold for nonlinear models. We illustrate this point with simple, realistic examples for which only one of the two realizations exists or for which both exist but their structures are profoundly different. Overall, the main point of this paper is the importance of the choice of realization in the development of nonlinear dynamic models. 相似文献
137.
The relation between the initial unbalance and the output signal of bridge circuits when acted upon simultaneously by the
physical factor being measured and the temperature of the surroundings when the bridge is supplied from a voltage or current
source is investigated. Analytic relations are obtained which explain the temperature dependence of the useful output voltage
under external physical action.
__________
Translated from Izmeritel’naya Tekhnika, No. 1, pp. 48–49, 2007. 相似文献
138.
A. Rizzo M.A. Signore M.F. De Riccardis L. Capodieci D. Dimaio T. Nocco 《Thin solid films》2007,515(17):6665-6671
The effect of the deposition rate on the structural and morphological properties of TiN and ZrN single layers and TiN/ZrN multilayers deposited by radiofrequency reactive magnetron sputtering has been studied. The total pressure was kept constant and the growth rate variation was obtained by small difference of nitrogen concentration in the fed gas. The decreasing deposition rate results in a structural change in the thin films from (111) orientation to (100) one. As consequence the surface morphology becomes smoother. Films roughness is strongly related with texture and it decreases with an increase in the (100) X-ray diffraction line intensity. In order to achieve a clear interpretation of our experimental results, the ratio between the N+ ions of the plasma and the atoms number reaching the substrate was considered. At high deposition rate with respect to the N+ concentration, the chemical potential of transition metal on (100) growth surface is higher than (111) one favouring the (111) orientation of the films. On the contrary, when the growth rate is low with respect to the nitrogen concentration, the chemical potential of transition metal on (111) growth surface is higher than the (100) one leading to a preferential growth in the (100) direction. 相似文献
139.
140.
Madden Gregory J.; Begotka Andrea M.; Raiff Bethany R.; Kastern Lana L. 《Canadian Metallurgical Quarterly》2003,11(2):139
The degree to which real and hypothetical rewards were discounted across delays ranging from 6 hr to 1 year was explored in a within-subjects design. An adjusting-amounts procedure was used to estimate the subjective value of real and hypothetical rewards at each delay. A hyperbolic discounting function provided a significantly better fit to individual participants' preferences than did an exponential function. No significant effect of reward type on degree of hyperbolic discounting or area under the discounting curves was detected. These findings offer some support for the validity of using hypothetical rewards to estimate discounting rates in substance-abusing and other populations, but caution is suggested because this support is gleaned from a failure to detect an effect of reward type. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献