全文获取类型
收费全文 | 11967篇 |
免费 | 910篇 |
国内免费 | 1224篇 |
专业分类
电工技术 | 1199篇 |
综合类 | 625篇 |
化学工业 | 5258篇 |
金属工艺 | 184篇 |
机械仪表 | 260篇 |
建筑科学 | 501篇 |
矿业工程 | 71篇 |
能源动力 | 1056篇 |
轻工业 | 224篇 |
水利工程 | 83篇 |
石油天然气 | 866篇 |
武器工业 | 14篇 |
无线电 | 82篇 |
一般工业技术 | 367篇 |
冶金工业 | 153篇 |
原子能技术 | 2863篇 |
自动化技术 | 295篇 |
出版年
2024年 | 11篇 |
2023年 | 102篇 |
2022年 | 196篇 |
2021年 | 304篇 |
2020年 | 339篇 |
2019年 | 342篇 |
2018年 | 317篇 |
2017年 | 386篇 |
2016年 | 452篇 |
2015年 | 369篇 |
2014年 | 688篇 |
2013年 | 1291篇 |
2012年 | 651篇 |
2011年 | 849篇 |
2010年 | 677篇 |
2009年 | 711篇 |
2008年 | 618篇 |
2007年 | 680篇 |
2006年 | 618篇 |
2005年 | 606篇 |
2004年 | 489篇 |
2003年 | 520篇 |
2002年 | 437篇 |
2001年 | 393篇 |
2000年 | 286篇 |
1999年 | 304篇 |
1998年 | 220篇 |
1997年 | 182篇 |
1996年 | 138篇 |
1995年 | 153篇 |
1994年 | 120篇 |
1993年 | 106篇 |
1992年 | 76篇 |
1991年 | 103篇 |
1990年 | 82篇 |
1989年 | 58篇 |
1988年 | 36篇 |
1987年 | 53篇 |
1986年 | 28篇 |
1985年 | 29篇 |
1984年 | 16篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1975年 | 1篇 |
1959年 | 32篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
61.
62.
S. M. Nikonov I. V. Elkin I. A. Lipatov A. V. Basov A. V. Kapustin A. A. Rovnov 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2007,41(6):351-354
Results of experiments conducted on a large-scale integral PSB-VVéR bench and directed toward investigation of the performance
of new passive safety systems for nuclear plants with a water-cooled power reactor, an additional system for passive flooding
of the active zone, and a system for the passive removal of heat from steam generators are presented.
__________
Translated from élektricheskie Stantsii, No. 9, September 2007, pp. 7–10. 相似文献
63.
Design for a high power-density Astron reactor 总被引:1,自引:0,他引:1
N. C. Christofilos 《Journal of Fusion Energy》1989,8(1-2):97-105
A liquid lithium blanket surrounding the plasma volume is described. The liquid lithium flows along magnetic flux tubes at a high speed. There is no vacuum wall between the blanket and the plasma. The E-layer of relativistic particles within which the plasma is confined serves as a vacuum wall protecting the plasma from the lithium vapor, which is continuously produced at the surface of the blanket, by ionizing the lithium atoms and ejecting the same along open magnetic lines. The heat load at the surface of the blanket generated by 14 MeV neutrons can be several hundred MW per square meter.Work performed under the auspices of the U.S. Atomic Energy Commission.Deceased September 24, 1972. 相似文献
64.
修正步冷温度曲线试验研究 总被引:3,自引:0,他引:3
按修正步冷温度曲线对经步冷脆化的 2 .2 5Cr 1Mo和在加氢反应器内运行 5a的 2 2 5Cr 1Mo试块进行了修正步冷试验 ,评定了材料的回火脆性。结果表明 ,按修正步冷曲线进行修正步冷试验能使已经脆化的材料进一步脆化 ,为加氢反应器材料损伤的研究提供了一条途径。 相似文献
65.
讨论了固定床反应器阻力降快速升高的原因,介绍了用轴径向技术解决这一问题的原理及优点,及其在铁铬系变换催化剂和钴钼系耐硫变换催化剂反应器中的实际应用。 相似文献
66.
67.
A novel annular reactor for kinetic studies at high temperature and flow conditions has been designed to keep eccentricity tolerances below 10%. In a previous work, we have shown that it is very important to keep such low eccentricity values in order to collect reliable kinetic data from this type of reactors. As proposed in this study, a modified reactor with the use of a spacer could guarantee an annular duct with low levels of eccentricity. Manufacturing tolerances or deformation effects giving rise to eccentricity can be significantly minimised when using this apparatus. The reactor has been both experimentally and theoretically characterised. Carbon monoxide oxidation was used as a model reaction under mass-transfer limited conditions revealing an eccentricity of ∼5%. With such small eccentricity levels, a concentric annular form can be assumed in the reactor analysis. Simple 1D or 2D models can therefore be inexpensively used in the evaluation of the kinetic data. Also, prior to the design of the annular reactor, a numerical investigation was carried out to clarify the effects of eccentricity, physical properties of the carrier gas and the annular aspect ratio on mass-transfer limitations. Contrary to expectations, a considerable increase in the fuel mass-diffusivity by carrier gas substitution did not change the mass-transfer rates for cases when eccentricity and aspect ratios were high. 相似文献
68.
With gradual shortage in the supply of crude oil, the importance of producing synthetic crude oil from oil sands and shale oil is increasing day by day. In the present paper, the effects of various process variables such as temperature, liquid hourly space velocity and hydrogen/heavy gas oil volumetric ratio on the removal of sulfur compounds from oil sands derived heavy gas oil has been studied. The experiments have been carried out in a micro scale trickle bed reactor over a commercial Ni-Mo catalyst. The temperature, liquid hourly space velocity and hydrogen/heavy gas oil volumetric ratio have been varied from 365 to 415°C, 0.5 to 1.9 h-1 and 400 to 1000 ml, respectively. Under optimum reaction conditions over 96% conversion of sulfur compounds was achieved. The kinetics of the rate of sulfur removal from the oil sands derived heavy gas oil has also been discussed in this article. 相似文献
69.
70.
通过数值计算和模拟研究,本文叙述了新型可控电抗器的广泛的无功调节功能,揭示了它所具有的大幅度限压的能力,并在理想数学模型的基础上分析了电抗器的限压机理。 相似文献