全文获取类型
收费全文 | 11128篇 |
免费 | 1006篇 |
国内免费 | 551篇 |
专业分类
电工技术 | 1103篇 |
综合类 | 734篇 |
化学工业 | 1998篇 |
金属工艺 | 442篇 |
机械仪表 | 546篇 |
建筑科学 | 538篇 |
矿业工程 | 386篇 |
能源动力 | 1006篇 |
轻工业 | 320篇 |
水利工程 | 114篇 |
石油天然气 | 584篇 |
武器工业 | 91篇 |
无线电 | 2080篇 |
一般工业技术 | 995篇 |
冶金工业 | 307篇 |
原子能技术 | 165篇 |
自动化技术 | 1276篇 |
出版年
2024年 | 45篇 |
2023年 | 211篇 |
2022年 | 267篇 |
2021年 | 354篇 |
2020年 | 405篇 |
2019年 | 345篇 |
2018年 | 297篇 |
2017年 | 370篇 |
2016年 | 382篇 |
2015年 | 403篇 |
2014年 | 697篇 |
2013年 | 652篇 |
2012年 | 803篇 |
2011年 | 881篇 |
2010年 | 669篇 |
2009年 | 631篇 |
2008年 | 609篇 |
2007年 | 674篇 |
2006年 | 646篇 |
2005年 | 515篇 |
2004年 | 460篇 |
2003年 | 434篇 |
2002年 | 360篇 |
2001年 | 325篇 |
2000年 | 245篇 |
1999年 | 187篇 |
1998年 | 133篇 |
1997年 | 115篇 |
1996年 | 113篇 |
1995年 | 86篇 |
1994年 | 79篇 |
1993年 | 53篇 |
1992年 | 61篇 |
1991年 | 29篇 |
1990年 | 25篇 |
1989年 | 19篇 |
1988年 | 20篇 |
1987年 | 11篇 |
1986年 | 5篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
The effect of biochar substituted for anthracite as reductant on magnetizing-roasting pyrite cinder was investigated.The key of magnetizing-roasting is the gasification reaction between reductants and CO2.Since biochar could react with CO2 more rapidly at lower temperature,the reactivity of biochar is better than that of anthracite.The gasification of biochar could produce reducing condition ofφCO/(φCO+φCO2)about 10%-20% between 700-800 ℃,which is in accord with the atmosphere and temperature of Fe2O3 reduction.So it is beneficial to the reduction of iron mineral of pyrite cinder.Compared with anthracite,biochar could decrease the roasting temperature from825 to 750 ℃ and roasting time from 20 to 15min,which shows that a better effect of magnetization could be obtained in the condition of lower temperature and shorter time.Using biochar as reductant,iron concentrate extracted from pyrite cinder as about 64%iron grade could be produced,and the recovery is over 90% under the condition of above 90% grinding particle less than 0.045 mm and magnetic intensity of 0.124-0.194 T. 相似文献
2.
Korolev I. A. Alekseenko N. N. Porodnov B. T. Sapunov V. A. Savel'ev D. V. 《Measurement Techniques》2003,46(9):865-871
The design of a sylphon bellows sensor and the basic circuits of an LC-generator and of a microprocessor unit are presented. An analytical pressure–frequency conversion function and a special method of adjusting the sensor ensure an error of less than 0.05%. The dynamic range is up to 105. The instruments developed cover the ranges 103, 104, and 105 Pa. 相似文献
3.
串行和并行接口模式是A/D转换器诸多分类中的一种,但却是应用中器件选择的一个重要指标.在同样的转换分辨率及转换速度的前提下,不同的接口方式不但影响了电路结构,更重要的是将在高速数据采集的过程中对采样周期产生较大影响.本文通过12位串行ADC ADS7822和并行ADC ADS774与AT89C51的接口电路,给出二者采样时间的差异性. 相似文献
4.
5.
6.
Σ-ΔA/D转换技术及仿真 总被引:1,自引:0,他引:1
Σ-ΔA/D转换技术近年来颇受重视,因为基于该技术的A/D转换器能达到很高的分辨率(16bit以上),并另具一系列优点。本文对Σ-ΔA/D转换器的基本原理,包括过采样(Oversampling),噪声成形(NoiseShaping),以及数字抽取滤波(DigitalDecimationFiltering)等内容,均作了叙述。作者还对一个20bitΣ-Δ转换器的算法进行了计算机仿真。该转换器采用了高阶MASH噪声成形技术,而其数字抽取滤波部分则由梳状滤波器与级联的半带滤波器构成。文章中给出了仿真结果。 相似文献
7.
介绍了单端正向变换器基本电路,重点叙述带三路调节DC电压的100KHZ180W离线电源。它采用具有低导电阻RDS和低栅极电荷Qg的新型场效应管(QFET)作为变换电路的主开关器件,降低了电源开关损耗并提高了效率3%-5%。 相似文献
8.
A new method of studying the corrosion inhibition mechanism of rare earth metal(REM) on LC4 Al alloy with the spilt cell technique was studied. The principle and experimental method of the spilt cell technique were analyzed. By measuring the change of net-electric current between the two electrodes caused by the change of the amount of oxygen in the solution and the addition of CeCl3, the influence of corrosive performance of CeCl3 on LC4 super-power aluminum alloy in the 0.1 mol·L−1 NaCl solution was investigated. Meanwhile, the conditional changes of pH values, CeCl3 solution, additire and time of performance were also studied. Finally, the features of electrode surface were revealed by using SEM and X-ray energy-dispersive spectrometry (EDS). By combining these with other electric chemical techniques, such as potential-time curve, polarization curve et al. 相似文献
9.
采用先加入絮凝剂脱灰,再经减压蒸馏切割420~500℃馏分的方法,将辽河催化裂化澄清油预处理,考察了澄清油、加入絮凝剂脱灰后的澄清油以及脱灰后再减压蒸馏所得的中间馏分这3种原料在热转化过程中中间相的转化历程,并采用偏光显微镜观察热转化产物。结果表明,澄清油预处理效果明显,所得中间馏分具有较低的H/C原子比(nH/nC)和适宜的组成分布,是生产针状焦的理想原料。热转化产物的光学组织结构属于各向异性发达的广域-流线型结构。 相似文献
10.
The glass‐transition temperature as a function of curing conversion for a modified diallylbisphenol A/diaminodiphenylsulfone/bismaleimide (BMI) resin was investigated at different temperature regimes and modeled using a modified Di Benedetto equation. Although the relationship between the glass‐transition temperature and conversion of the BMI system conforms to the Di Benedetto equation for α < 0.6 and at lower cure temperatures, at higher cure temperatures the results deviated significantly from the equation; thus, it was an inadequate model for the system. Fourier transform IR analysis showed that the major crosslinking reactions did not occur during cure for the modified BMI at and below 150°C. However, as the cure temperature was increased, the crosslinking reactions responsible for 3‐dimensional network structures became more dominant. At 190°C the C? N? Cstretch vibration of the uncured maleimide ring converted into succinimide rings in the curing process. Simultaneously, a decrease was observed for the absorbance bands of ? C? Hbending (maleimide). The higher cure temperatures induced a significantly faster initial crosslinking rate and also resulted in a shorter period of time after which further crosslinking was retarded, because the increase in the crosslinks also physically slowed further crosslinking activity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 227–235, 2002 相似文献