全文获取类型
收费全文 | 6221篇 |
免费 | 826篇 |
国内免费 | 474篇 |
专业分类
电工技术 | 667篇 |
综合类 | 773篇 |
化学工业 | 546篇 |
金属工艺 | 182篇 |
机械仪表 | 302篇 |
建筑科学 | 428篇 |
矿业工程 | 149篇 |
能源动力 | 213篇 |
轻工业 | 251篇 |
水利工程 | 196篇 |
石油天然气 | 220篇 |
武器工业 | 38篇 |
无线电 | 750篇 |
一般工业技术 | 975篇 |
冶金工业 | 236篇 |
原子能技术 | 56篇 |
自动化技术 | 1539篇 |
出版年
2024年 | 17篇 |
2023年 | 109篇 |
2022年 | 169篇 |
2021年 | 223篇 |
2020年 | 278篇 |
2019年 | 220篇 |
2018年 | 208篇 |
2017年 | 260篇 |
2016年 | 314篇 |
2015年 | 278篇 |
2014年 | 413篇 |
2013年 | 557篇 |
2012年 | 511篇 |
2011年 | 496篇 |
2010年 | 342篇 |
2009年 | 380篇 |
2008年 | 321篇 |
2007年 | 401篇 |
2006年 | 311篇 |
2005年 | 274篇 |
2004年 | 252篇 |
2003年 | 218篇 |
2002年 | 154篇 |
2001年 | 136篇 |
2000年 | 96篇 |
1999年 | 89篇 |
1998年 | 71篇 |
1997年 | 70篇 |
1996年 | 50篇 |
1995年 | 41篇 |
1994年 | 33篇 |
1993年 | 28篇 |
1992年 | 30篇 |
1991年 | 25篇 |
1990年 | 26篇 |
1989年 | 15篇 |
1988年 | 20篇 |
1987年 | 14篇 |
1986年 | 11篇 |
1985年 | 9篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1980年 | 4篇 |
1964年 | 4篇 |
1962年 | 2篇 |
1959年 | 2篇 |
1957年 | 3篇 |
1956年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有7521条查询结果,搜索用时 15 毫秒
1.
Jean-Claude Malela-Majika Sandile Charles Shongwe Olatunde Adebayo Adeoti 《Quality and Reliability Engineering International》2021,37(8):3314-3322
The sensitivity of a monitoring scheme depends on many factors including the variance of the charting statistic which is very important in the computation of the control limits. This paper discusses the computation of the variance of the recently proposed hybrid homogeneously weighted moving average (HHWMA) scheme which was based on an incorrect assumption. The correct variance is used to evaluate the run-length characteristics of the HHWMA scheme. It is observed that the incorrect variance has a significant impact on the sensitivity (or performance) of the HHWMA scheme. 相似文献
2.
提出一种适用于DS-CDMA无线通信系统的低计算量而性能良好的信道估计算法。在DS-CDMA系统中,当接收信号经过解扩或多用户检测等时域预处理后,可以认为干扰大大减弱、期望信号在处理后的信号中占主要地位。这样,用预处理后信号相关阵的最大特征值对应的特征矢量可以很好地近似期望信号的信道矢量。但是,直接特征分解需要很大的计算量,特征跟踪计算量较低,但瞬态性能较差。本文提出一种基于相关矩阵列矢量平均的信道估计算法,该算法不需要特征分解或跟踪。仿真结果表明:新算法在降低计算量的情况下可以获得同直接特征分解方法几乎相同的性能。 相似文献
3.
Seog Geun Kang 《ETRI Journal》2006,28(2):235-238
In this letter, a block code that minimizes the peak‐to‐average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals is proposed. It is shown that peak envelope power is invariant to cyclic shift and codeword inversion. The systematic encoding rule for the proposed code is composed of searching for a seed codeword, shifting the register elements, and determining codeword inversion. This eliminates the look‐up table for one‐to‐one correspondence between the source and the coded data. Computer simulation confirms that OFDM systems with the proposed code always have the minimum PAPR. 相似文献
4.
本文对多信道光纤环形网络结构进行了详细分析,推导出环网内平均路经长度和最大直径计算公式,并分析了最佳多信道光纤环网结构。 相似文献
5.
Comments on the article by K. T. Herbst-Damm and J. A. Kulik (see record 2005-02260-012) entitled Volunteer support, marital status, and the survival times of terminally ill patients. Can a simple and low-cost intervention, such as a visit by a volunteer, extend the life of terminally ill patients? The answer, according to a study by Herbst-Damm and Kulik (2005), is yes. When it comes to quality of life, however, the effects of volunteer visits remain murky. Thus, it is critical that we look beyond effects on longevity and assess how such a program would influence quality of life. Extending the life of terminally ill patients might not always a blessing. Prolonging their life might even cause harm, as it can extend unwanted physical and mental suffering. It may also go against some patients' desire to hasten their death. Despite Herbst-Damm and Kulik's important findings, the current author remains unconvinced as to the merits of implementing volunteer visits as an intervention policy. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
It is necessary to determine the accurate reflectance of painted surfaces for the review of paint finishes by computer graphics (CG) before actual painting of the exterior color of automobiles, and for quality control during production and inspection processes. We have optimized a method for measuring reflectance by using a statistical technique. We have found that the reflectance of a painted surface is best measured at an incident angle of 60° and at five aspecular angles of 10°, 18°, 28°, 40°, and 90°. Our method makes it possible to accurately reproduce reflection characteristics of paint finishes containing special flake pigments, such as pearl mica. Also it was proved that our method can apply not only to solid and metallic coatings but to all painted surfaces. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 275–282, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20125 相似文献
7.
8.
Standard Gibbs free energy of formation (ΔGf0), an important property needed in design calculations has been estimated using molar refraction, RM. The linear relationships derived between ΔGf0 and RM tested with the data on 8 series of hydrocarbons at 228 compounds yielded average deviations comparable to the methods cited in recent literature. The method can be used as an alternative to the existing ones, because of its simplicity combined with reasonable accuracy. 相似文献
9.
本文利用可控平均冷却速度的单向凝固实验炉测定了45号钢在不同平均冷却速度下的冷却曲线,由此得到其在凝固期间的平均冷却速度R,相应地测量了不同平均冷却速度下试样的二次枝晶臂间距S2,通过回归,得到了如下关系式:S2=727R-0.41,并将引式成功地应用于实际生产中。 相似文献
10.
首先对OFDM的发展以及应用做了简要的介绍,然后讨论了当前OFDM研究过程中的两个关键技术问题,最后展望了OFDM的未来发展。 相似文献