全文获取类型
收费全文 | 105817篇 |
免费 | 10464篇 |
国内免费 | 6070篇 |
专业分类
电工技术 | 7890篇 |
技术理论 | 5篇 |
综合类 | 7743篇 |
化学工业 | 16360篇 |
金属工艺 | 6305篇 |
机械仪表 | 7105篇 |
建筑科学 | 8310篇 |
矿业工程 | 2934篇 |
能源动力 | 3060篇 |
轻工业 | 7581篇 |
水利工程 | 2139篇 |
石油天然气 | 5113篇 |
武器工业 | 1030篇 |
无线电 | 12995篇 |
一般工业技术 | 12717篇 |
冶金工业 | 4620篇 |
原子能技术 | 1313篇 |
自动化技术 | 15131篇 |
出版年
2024年 | 608篇 |
2023年 | 1947篇 |
2022年 | 3640篇 |
2021年 | 5102篇 |
2020年 | 3785篇 |
2019年 | 3128篇 |
2018年 | 3237篇 |
2017年 | 3558篇 |
2016年 | 3322篇 |
2015年 | 4533篇 |
2014年 | 5546篇 |
2013年 | 6545篇 |
2012年 | 7443篇 |
2011年 | 7972篇 |
2010年 | 6855篇 |
2009年 | 6750篇 |
2008年 | 6793篇 |
2007年 | 6092篇 |
2006年 | 5963篇 |
2005年 | 4775篇 |
2004年 | 3455篇 |
2003年 | 3039篇 |
2002年 | 3265篇 |
2001年 | 2866篇 |
2000年 | 2363篇 |
1999年 | 1995篇 |
1998年 | 1473篇 |
1997年 | 1240篇 |
1996年 | 1058篇 |
1995年 | 872篇 |
1994年 | 671篇 |
1993年 | 470篇 |
1992年 | 398篇 |
1991年 | 326篇 |
1990年 | 253篇 |
1989年 | 233篇 |
1988年 | 158篇 |
1987年 | 129篇 |
1986年 | 79篇 |
1985年 | 73篇 |
1984年 | 52篇 |
1983年 | 45篇 |
1982年 | 44篇 |
1981年 | 33篇 |
1980年 | 39篇 |
1979年 | 23篇 |
1978年 | 15篇 |
1976年 | 19篇 |
1975年 | 10篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
基于DSP的电力数据采集平台的设计与研究 总被引:1,自引:0,他引:1
介绍了一种用于电力系统的数据采集系统.该系统采用数字信号处理器(DSP)和复杂可编程逻辑器件(CPLD)作为核心芯片,给出了主要部分的电路及其原理、功能,系统中使用CPLD实现基本逻辑,使系统有足够的冗余和灵活性,具有可靠性高、可升级等优点. 相似文献
73.
Toughening mechanism for a rubber-toughened epoxy resin with rubber/matrix interfacial modification 总被引:1,自引:0,他引:1
For a rubber-toughened piperidine-DGEBA epoxy resin, the interface between the rubber particle and the epoxy resin matrix was modified by an epoxide end-capped carboxyl terminated butadiene and acrylonitrile random copolymer (CTBN). The end-capping epoxides used were a rigid diglycidyl ether of bisphenol-A (Epon 828), a short-chain flexible diglycidyl ether of propylene glycol (DER 736), and a long-chain flexible diglycidyl ether of propylene glycol (DER 732). The microstructures and the fracture behaviour of these rubber-modified epoxy resins were studied by transmission electron microscopy and scanning electron microscopy. Their thermal and mechanical properties were also investigated. In the rubber-modified epoxy resins, if the added CTBNs were end-capped by a flexible diglycidyl ether of propylene glycol (DER 732 or DER 736) before curing, the interfacial zone of the undeformed rubber particle, the degree of cavitation of the cavitated rubber particle on the fracture surface and the fracture energy of the toughened epoxy resin were all significantly increased. The toughening mechanism based on cavitation and localized shear yielding was considered and a mechanism for the interaction between cavitation and localized shear yielding that accounts for all the observed characteristics is proposed. 相似文献
74.
Y.-Y. Won H.-C. Kwon S.-K. Han 《Optoelectronics, IET》2007,1(2):61-64
A new scheme for reducing optical beat interference (OBI) noise in optical network units is proposed for subcarrier multiplexing-based access network applications. The optical spectrum of the transmit lasers is broadened by using a radio frequency (RF) clipping tone with a modulation depth greater than one. This reduces the impact of the OBI noise. The distortions caused by an RF clipping tone are also suppressed by introducing a gain-saturated reflective optical amplifier, which shows the characteristics of high-pass filter. The proposed scheme has been verified by measuring the error vector magnitude of 16QAM signal with 20 Mbps. Error-free transmission has been achieved even when the light of OBI-noise-causing lasers is stronger than that of the signal laser by 7 dB 相似文献
75.
76.
Yi‐Hung Chen Ching‐Yuan Chang Wei‐Ling Su Chun‐Yu Chiu Yue‐Hwa Yu Pen‐Chi Chiang Chiung‐Fen Chang Je‐Lueng Shie Chyow‐San Chiou Sally IM Chiang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(1):68-75
This study investigates the ozonation of CI Reactive Black 5 (RB5) by using the rotating packed bed (RPB) and completely stirred tank reactor (CSTR) as ozone contactors. The RPB, which provides high gravitational force by adjusting the rotational speed, was employed as a novel ozone contactor. The same ozone dosage was separately introduced into either the RPB or the CSTR for the investigation, while the experimental solution was continuously circulated within the apparatus consisting of the RPB and CSTR. The decolorization and mineralization efficiencies of RB5 in the course of ozonation are compared for these two methods. Moreover, the dissolved and off‐gas ozone concentrations were simultaneously monitored for the further analysis. As a result, the ozone mass transfer rate per unit volume of the RPB was significantly higher because of its higher mass transfer coefficient and gas–liquid concentration driving force. Furthermore, ozonation kinetics was found to be independent of the gravitational magnitude of an ozone gas–liquid contactor. Therefore, the results suggest employing RPBs as ozone‐contacting devices with the advantage of volume reduction. The experimental results, which can be used for further modeling of the ozonation process in the RPB, also show the requirement of correct design for the RPB. Consequently, the present study is useful for the understanding of practical application of RPBs. Copyright © 2004 Society of Chemical Industry 相似文献
77.
Cu—Zn—Al系合金热弹性马氏体相变的热滞 总被引:3,自引:0,他引:3
韩明 《有色金属材料与工程》1997,18(2):53-55
本文通过热处理工艺及添加第四组元研究了Cu-Zn-Al系记忆合金的相变热滞。结果表明,淬火冷却速度影响合金的相变热滞大小,随着母相时效时间的延长,马氏体相变热滞变大.Mn元素的加入可以减小CU-Zn-Al合金相变热滞. 相似文献
78.
用保形样条方法求解非定常对流扩散方程 总被引:1,自引:0,他引:1
在欧拉-拉格朗日分裂方法的基础上,本文发展了一种固定网格上的欧拉-拉格朗日分裂方法.保形样条方法(SPSM)被用来解决倒特征线插值问题.通过求解几个有精确解的例子,说明SPSM方法的解是单调无振荡的,并且数值耗散也是比较小的. 相似文献
79.
80.
在一定实验条件下,屏蔽暂堵的反排解堵效率随压差、温度的增大而增大,反排解堵在很短的时间内就可完成。一般的反排解堵率都在60%以上,但反徘不能完全解堵。 相似文献