全文获取类型
收费全文 | 15529篇 |
免费 | 1482篇 |
国内免费 | 781篇 |
专业分类
电工技术 | 1038篇 |
综合类 | 2052篇 |
化学工业 | 491篇 |
金属工艺 | 478篇 |
机械仪表 | 1085篇 |
建筑科学 | 5122篇 |
矿业工程 | 379篇 |
能源动力 | 157篇 |
轻工业 | 574篇 |
水利工程 | 262篇 |
石油天然气 | 201篇 |
武器工业 | 146篇 |
无线电 | 1765篇 |
一般工业技术 | 1074篇 |
冶金工业 | 391篇 |
原子能技术 | 101篇 |
自动化技术 | 2476篇 |
出版年
2024年 | 41篇 |
2023年 | 115篇 |
2022年 | 273篇 |
2021年 | 354篇 |
2020年 | 373篇 |
2019年 | 294篇 |
2018年 | 294篇 |
2017年 | 403篇 |
2016年 | 475篇 |
2015年 | 505篇 |
2014年 | 1060篇 |
2013年 | 914篇 |
2012年 | 1243篇 |
2011年 | 1394篇 |
2010年 | 1013篇 |
2009年 | 1049篇 |
2008年 | 1011篇 |
2007年 | 1227篇 |
2006年 | 989篇 |
2005年 | 874篇 |
2004年 | 639篇 |
2003年 | 594篇 |
2002年 | 475篇 |
2001年 | 432篇 |
2000年 | 337篇 |
1999年 | 277篇 |
1998年 | 201篇 |
1997年 | 175篇 |
1996年 | 138篇 |
1995年 | 120篇 |
1994年 | 112篇 |
1993年 | 68篇 |
1992年 | 58篇 |
1991年 | 53篇 |
1990年 | 49篇 |
1989年 | 29篇 |
1988年 | 34篇 |
1987年 | 14篇 |
1986年 | 12篇 |
1985年 | 7篇 |
1984年 | 12篇 |
1983年 | 10篇 |
1982年 | 3篇 |
1980年 | 12篇 |
1978年 | 6篇 |
1976年 | 3篇 |
1963年 | 2篇 |
1959年 | 3篇 |
1957年 | 2篇 |
1956年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
1.
2.
3.
In this paper, an adaptive control approach is designed for compensating the faults in the actuators of chaotic systems and maintaining the acceptable system stability. We propose a state‐feedback model reference adaptive control scheme for unknown chaotic multi‐input systems. Only the dimensions of the chaotic systems are required to be known. Based on Lyapunov stability theory, new adaptive control laws are synthesized to accommodate actuator failures and system nonlinearities. An illustrative example is studied. The simulation results show the effectiveness of the design method. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
4.
Frequency band selection (FBS) in rotating machinery fault diagnosis aims to recognize frequency band location including a fault transient out of a full band spectrum, and thus fault diagnosis can suppress noise influence from other frequency components. Impulsiveness and cyclostationarity have been recently recognized as two distinctive signatures of a transient. Thus, many studies have focused on developing quantification metrics of the two signatures and using them as indicators to guide FBS. However, most previous studies almost ignore another aspect of FBS, i.e. health reference, which significantly affect FBS performance. To address this issue, this paper investigates importance of a health reference and recognize it as the third critical aspect in FBS. With help of the health reference, the frequency band where the fault transient exists could be located. A novel approach based on classification is proposed to integrate all three aspects (impulsiveness, cyclostationarity, and health reference) for FBS. Classification accuracy is developed as a novel indicator to select the most sensitive frequency band for rotating machinery fault diagnosis. The proposed method (coined by accugram) has been validated on benchmark and experiment datasets. Comparison results show its effectiveness and robustness over conventional envelope analysis, the kurtogram, and the infogram. 相似文献
5.
无源光网络(Passive Optical Network,PON)作为当今接入网的主要技术解决方案,具有带宽使用效率高、传输距离远、抗干扰能力强等特点.通过研究PON技术的发展动态,本文首先归纳了各种PON技术的产生背景和应用特点,整理出各技术间的连接关系及主要标准;其次介绍了PON技术的帧结构,并对带宽、波长、传输模式等PON技术的主要参数进行了汇总;然后将国内外研究热点进行划分,围绕媒体访问控制协议、帧结构、动态带宽分配算法、节能机制等关键技术,阐述了其研究现状及在PON中的重要作用;最后对PON技术的发展趋势进行了展望. 相似文献
6.
Avtar Singh Soottawat Benjakul Nurul Huda 《International Journal of Food Science & Technology》2020,55(12):3553-3562
Effect of debittered salmon frame hydrolysate (DSFH) at various levels (0, 5, 10, 15, 20 and 25 g/100 g) on physicochemical, textural, sensory and nutritional properties of biscuits was investigated. The highest thickness was obtained for the sample with 25 g/100 g DSFH (P < 0.05). There was no difference in diameter among all the biscuit samples (P > 0.05). The samples added with DSFH had lower weight, water activity and moisture content than the control (CONT, without DSFH) (P < 0.05). DSFH at 15 g/100 g showed no detrimental effect on sensory properties of resulting biscuits (DSFH-15). The DSFH-15 biscuit showed reduction in cutting force and fracturability. Scanning electron microscopic and cross-sectional images showed that DSFH-15 biscuit had more porous structure, compared to the CONT. The biscuits fortified with 15 g/100 g DSFH had higher protein but had lower energy value, fat and carbohydrate content than the CONT. 相似文献
7.
径向基函数网络(RBFN)已广泛应用于参考腾发量预测等领域,但常用的K均值聚类和自组织特征映射等方法在求取径向基函数网络隐层节点中心时存在较大不足。针对这一问题,本文引入投影寻踪方法,在投影降维的基础上实现对大量高维数据的聚类,建立了基于投影寻踪的径向基函数网络模型,并将该模型应用于山西潇河灌区参考腾发量的预测,研究了不同气象因子输入对参考腾发量预测精度的影响。结果表明,基于投影寻踪的径向基函数网络具有较强的适用性,只需使用最高温度、最低温度、日照时数和旬序数作为输入因子,就能以较高的精度预测参考腾发量。 相似文献
8.
Kruk Menno R.; Halász József; Meelis Wout; Haller József 《Canadian Metallurgical Quarterly》2004,118(5):1062
Aggressive behavior induces an adrenocortical stress response, and sudden stressors often precipitate violent behavior. Experiments in rats revealed a fast, mutual, positive feedback between the adrenocortical stress response and a brain mechanism controlling aggression. Stimulation of the aggressive area in the hypothalamus rapidly activated the adrenocortical response, even in the absence of an opponent and fighting. Hypothalamic aggression, in turn, was rapidly facilitated by a corticosterone injection in rats in which the natural adrenocortical stress response was prevented by adrenalectomy. The rapidity of both effects points to a fast, mutual, positive feedback of the controlling mechanisms within the time frame of a single conflict. Such a mutual facilitation may contribute to the precipitation and escalation of violent behavior under stressful conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
10.