全文获取类型
收费全文 | 261600篇 |
免费 | 20066篇 |
国内免费 | 13307篇 |
专业分类
电工技术 | 16765篇 |
技术理论 | 52篇 |
综合类 | 36380篇 |
化学工业 | 28368篇 |
金属工艺 | 9661篇 |
机械仪表 | 14053篇 |
建筑科学 | 37626篇 |
矿业工程 | 14899篇 |
能源动力 | 7856篇 |
轻工业 | 14517篇 |
水利工程 | 13941篇 |
石油天然气 | 11156篇 |
武器工业 | 2496篇 |
无线电 | 16868篇 |
一般工业技术 | 18375篇 |
冶金工业 | 15440篇 |
原子能技术 | 2611篇 |
自动化技术 | 33909篇 |
出版年
2024年 | 805篇 |
2023年 | 2470篇 |
2022年 | 4757篇 |
2021年 | 5722篇 |
2020年 | 6076篇 |
2019年 | 5126篇 |
2018年 | 4808篇 |
2017年 | 5862篇 |
2016年 | 6962篇 |
2015年 | 7807篇 |
2014年 | 14484篇 |
2013年 | 13121篇 |
2012年 | 17210篇 |
2011年 | 18321篇 |
2010年 | 14596篇 |
2009年 | 15259篇 |
2008年 | 14283篇 |
2007年 | 18764篇 |
2006年 | 17819篇 |
2005年 | 15614篇 |
2004年 | 13289篇 |
2003年 | 12005篇 |
2002年 | 9883篇 |
2001年 | 8358篇 |
2000年 | 7047篇 |
1999年 | 5763篇 |
1998年 | 4348篇 |
1997年 | 3817篇 |
1996年 | 3544篇 |
1995年 | 3000篇 |
1994年 | 2678篇 |
1993年 | 2001篇 |
1992年 | 1779篇 |
1991年 | 1324篇 |
1990年 | 1156篇 |
1989年 | 1019篇 |
1988年 | 819篇 |
1987年 | 564篇 |
1986年 | 423篇 |
1985年 | 350篇 |
1984年 | 330篇 |
1983年 | 241篇 |
1982年 | 214篇 |
1981年 | 166篇 |
1980年 | 130篇 |
1979年 | 110篇 |
1978年 | 62篇 |
1977年 | 73篇 |
1976年 | 55篇 |
1975年 | 56篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
化工企业环境因素的评价 总被引:1,自引:0,他引:1
化工企业环境因素评价是建立环境管理体系的核心任务,化工企业生产过程的特点决定了其环境因素数量多、环境影响大、识别评价难、控制难度大。本文介绍了化工企业环境因素评价的技术方法和过程,可以为提高环境因素评价的科学性、客观性和充分性提供参考。 相似文献
62.
63.
We analyze the wear resistance of plasma coatings for a constant work of friction. The dependences of the wear resistance
of the coatings are obtained for a broad range of loading conditions. It is shown that the minimum sensitivity to loading
conditions is exhibited by the molybdenum coatings. It is also established that the wear resistance of the coatings decreases
as the amplitude of displacements increases and the cyclic frequency of the tests decreases due to the intensification of
fatigue processes on the surfaces. The comparative characteristics of coatings are presented.
__________
Translated from Problemy Prochnosti, No. 5, pp. 94–100, September–October, 2007. 相似文献
64.
《Drying Technology》2007,25(10):1621-1632
A study was performed to determine the drying characteristics and quality of barley grain dried in a laboratory scale spouted-bed dryer at 30, 35, 40, and 45°C and an inlet air velocity of 23 m/s-1, and in an IR-convection dryer under an infrared radiation intensity of 0.048, 0.061, 0.073, and 0.107 W cm-2 at an air velocity of 0.5 m/s-1. The results show that the first, relatively short, phase of a sharp decrease in the drying rate was followed by the phase of a slow decrease. The time of barley drying depended on temperature of inlet air in a spouted-bed dryer and on radiation intensities in an IR-convection dryer. Barley drying at 45°C in a spouted-bed dryer was accompanied by the lowest total energy consumption. The average specific energy consumption was lower and the average efficiency of drying was higher for drying in a spouted-bed dryer. The effective diffusivities were in the range 2.20-4.52 × 10-11 m2 s-1 and 3.04-4.79 × 10-11 m2/s-1 for barley dried in a spouted-bed and in an IR-convection dryer, respectively. There were no significant differences in kernel germination energy and capacity between the two drying methods tested. 相似文献
65.
Power devices with high capability have been developed. 8‐kV/3.5‐kA‐class light‐triggered thyristors have the highest capability among power devices. These devices are used in the Kii Channel HVDC transmission system in Japan. In this paper, we report the extracted problems of conventional testing methods of 8‐kV/3.5‐kA‐class light‐triggered thyristors among manufacturers, and the proposed unified testing methods on the basis of element characteristics and operating conditions in the Kii Channel HVDC system. Furthermore, we propose a figure of merit for power devices for the practical use, and try to extract elements used at the Kii Channel HVDC system with small margins and low withstand capabilities. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(3): 61–70, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10024 相似文献
66.
Distilled fractions of a coal-derived liquid from the H-Coal process were upgraded to diesel fuel by catalytic hydrotreatment. The total hydrotreated products were distilled into naphtha (<180°C) and diesel fuel fractions (>180°C) and the diesel fractions were analysed for hydrocarbon-type composition, hydrogen content and some diesel fuel properties. GC—MS-analyses were carried out on the hydrocarbon-type fractions to identify individual chemical compounds. To investigate the effect of different distillation cut points on diesel fuel yield and properties, cut points for one hydrotreated product were varied. The diesel fuel cetane numbers were correlated with percentage hydrogen, total aromatics and saturates. Cetane numbers above 40 were obtained for diesel fuels containing (i) more than 75% saturates, (ii) less than 15% total aromatics and (iii) a hydrogen content above 12.8%. Compounds identified by GC—MS-analyses (in the diesel fractions) were typical aromatic and cycloparaffin compounds. Normal-and iso-paraffin compounds were not detected. By varying the distillation cut point from 135 to 180°C, the cetane number of the residual diesel fraction improved from 37 to 44. This increase is ascribed to the removal of aromatic compounds in the 135–180°C boiling point range. 相似文献
67.
HHD型核子秤电离室已成功地使用于HCS型核子秤.对它的各种物理性能指标进行了检测,各项性能指标都达到了设计要求。 相似文献
68.
S. Gratch 《International Journal of Thermophysics》1985,6(6):541-544
Historical developments regarding the realization of the importance of reliable thermophysical properties data in engineering applications are presented. The events leading to the establishment of the Symposium on Thermophysical Properties in 1959 and the accomplishments of the symposia series since then are discussed. Contributions of the National Bureau of Standards to the thermophysical properties field are described.Welcoming address presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A. 相似文献
69.
我国建筑涂料技术进步简评 总被引:1,自引:1,他引:0
从以下诸方面简述我国建筑涂料的技术进步:⑴新品种涂料的研制开发;⑵加强对配套材料及施工技术的研究;⑶超细填料在涂料中的应用;⑷计算机自动配色技术;⑸产品标准的修订;⑹建筑涂料的实用范围扩大。 相似文献
70.
凸轮进给式双管平头倒棱机 总被引:3,自引:0,他引:3
研制的凸轮进给式双管平头倒棱机可自动完成上料→夹紧→平头倒棱→松开→退料动作循环,同步准确,可靠性高,平头倒棱质量好。介绍了该装置的工作原理、工作程序、技术性能、设备组成以及刀具和夹具的特点。 相似文献