全文获取类型
收费全文 | 40679篇 |
免费 | 4564篇 |
国内免费 | 2893篇 |
专业分类
电工技术 | 6367篇 |
综合类 | 3557篇 |
化学工业 | 2511篇 |
金属工艺 | 1338篇 |
机械仪表 | 5597篇 |
建筑科学 | 2409篇 |
矿业工程 | 1147篇 |
能源动力 | 1120篇 |
轻工业 | 1430篇 |
水利工程 | 853篇 |
石油天然气 | 1014篇 |
武器工业 | 669篇 |
无线电 | 6097篇 |
一般工业技术 | 4831篇 |
冶金工业 | 1415篇 |
原子能技术 | 870篇 |
自动化技术 | 6911篇 |
出版年
2024年 | 102篇 |
2023年 | 485篇 |
2022年 | 882篇 |
2021年 | 1035篇 |
2020年 | 1162篇 |
2019年 | 888篇 |
2018年 | 889篇 |
2017年 | 1367篇 |
2016年 | 1595篇 |
2015年 | 1750篇 |
2014年 | 2565篇 |
2013年 | 2325篇 |
2012年 | 3079篇 |
2011年 | 3131篇 |
2010年 | 2277篇 |
2009年 | 2347篇 |
2008年 | 2479篇 |
2007年 | 2929篇 |
2006年 | 2622篇 |
2005年 | 2161篇 |
2004年 | 1940篇 |
2003年 | 1619篇 |
2002年 | 1345篇 |
2001年 | 1196篇 |
2000年 | 995篇 |
1999年 | 844篇 |
1998年 | 637篇 |
1997年 | 713篇 |
1996年 | 513篇 |
1995年 | 414篇 |
1994年 | 391篇 |
1993年 | 315篇 |
1992年 | 226篇 |
1991年 | 163篇 |
1990年 | 151篇 |
1989年 | 100篇 |
1988年 | 86篇 |
1987年 | 66篇 |
1986年 | 42篇 |
1985年 | 42篇 |
1984年 | 46篇 |
1983年 | 25篇 |
1982年 | 35篇 |
1981年 | 17篇 |
1980年 | 13篇 |
1979年 | 9篇 |
1977年 | 14篇 |
1973年 | 8篇 |
1964年 | 8篇 |
1959年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Burcu Selen alayan Ahmet K. Avc Z. lsen
nsan A. Erhan Aksoylu 《Applied Catalysis A: General》2005,280(2):181-188
Indirect partial oxidation (IPOX) of propane was studied over bimetallic 0.2 wt.% Pt–15 wt.% Ni/δ-Al2O3 catalyst in the 623–743 K temperature range. The unreduced and reduced forms of the catalyst were characterized by ESEM–EDAX and X-ray diffraction (XRD). In the IPOX tests, the effects of steam to carbon ratio (S/C), carbon to oxygen ratio (C/O2) and residence time (W/F (gcat h/mol HC)) on the hydrogen production activity, selectivity and product distribution were studied in detail. The effect of temperature program applied (increasing from 623 to 743 K, ITP; decreasing from 743 to 623 K, DTP) during reaction was also tested. The results showed that the Pt–Ni bimetallic system has superior performance characteristics compared to the monometallic catalysts reported in literature. The reason is thought to be the utilization of the catalyst particles as micro heat exchangers during IPOX; the heat generated by Pt sites during exothermic total oxidation (TOX) being readily transferred through the catalyst particles acting as micro heat exchangers to the Ni sites, which promote endothermic steam reforming (SR). The optimal conditions were found as S/C = 3, C/O2 = 2.70 and W/F = 0.51 gcat h/mol HC for IPOX of propane on the basis of high hydrogen productivity and selectivity between 623 and 748 K for the experimental conditions tested. The thermo-neutral points obtained showed the sustainability of reaction in terms of energy. 相似文献
92.
Scale selection using three different representations for images 总被引:1,自引:0,他引:1
J. Martinez-Baena J. A. García J. Fdez-Valdivia Rosa Rodriguez-Sanchez 《Pattern recognition letters》1997,18(14):1453-1467
93.
报道了一种新型毫米波天线—衍射天线的测量结果.经分析讨论说明,这种天线具有良好的电性能. 相似文献
94.
95.
96.
This paper reviews the current state of industry with regard to the introduction of software metrics. It discusses the benefits that organizations have derived from metrication, it looks at why organizations have sought to introduce metrics programmes, how they have gone about introducing those programmes and the problems that they have encountered during implementation. The review found that, on the whole, only the sanitized aspects of metrics experiences have actually been published. This seems to be especially the case with respect to practitioner resistance. Very few organizations admit to having encountered resistance during the introduction of a metrics programme. The paper also includes the results of a pilot study, conducted by the first author, which examines the attitudes that developers hold towards the introduction of software metrics. The key findings of this pilot study are that positive attitudes to metrics correlate highly with levels of education and to job satisfaction. 相似文献
97.
正交双频光栅CCD系统剪切干涉测量二维温度场 总被引:1,自引:1,他引:0
以半导体激光器为光源,利用正交双频光栅(ODFG)CCD系统剪切干涉对带平板边界的半圆柱体热源的二维温度场进行实时诊断,分析剪切干涉图时,用柱函数系作为拟合基底,给出二维自然对流温度场的定量分布。 相似文献
98.
介绍了替代进口梳棉机测厚传感器集成电路分立元件的电路图,工作原理及特点。一年多的实际运行证明,电路参数达到了设计要求。 相似文献
99.
结合实时法全息干涉计量和数字图象处理技术,提出了一种溶液扩散系数的自动测量系统。在干涉图的处理中,采用了相位检测和曲线拟合技术,得到了亚象素的测量精度。 相似文献
100.
S. Matsuo Y. Mizuguchi Y. Tanaka H. Kubota R. Yamamoto 《International Journal of Thermophysics》1996,17(2):441-454
Densities of aqueous of 1,4-dioxane have been measured at temperatures from 298 to 348 K and at pressures up to 40 MPa by a vibrating-tube method. Molar volumes obtained with an estimated uncertainty of ±0.2°,% are correlated with pressure by the Tait equation within the experimental uncertainty. Pressure and composition dependences of the excess molar volume, partial molar volume, and isothermal compressibility are determined and they are compared with those of other aqueous solutions. 相似文献