全文获取类型
收费全文 | 2355篇 |
免费 | 71篇 |
国内免费 | 46篇 |
专业分类
电工技术 | 421篇 |
综合类 | 67篇 |
化学工业 | 252篇 |
金属工艺 | 73篇 |
机械仪表 | 225篇 |
建筑科学 | 70篇 |
矿业工程 | 35篇 |
能源动力 | 395篇 |
轻工业 | 12篇 |
水利工程 | 14篇 |
石油天然气 | 37篇 |
武器工业 | 26篇 |
无线电 | 254篇 |
一般工业技术 | 239篇 |
冶金工业 | 68篇 |
原子能技术 | 117篇 |
自动化技术 | 167篇 |
出版年
2024年 | 2篇 |
2023年 | 25篇 |
2022年 | 24篇 |
2021年 | 36篇 |
2020年 | 46篇 |
2019年 | 26篇 |
2018年 | 24篇 |
2017年 | 63篇 |
2016年 | 62篇 |
2015年 | 72篇 |
2014年 | 78篇 |
2013年 | 143篇 |
2012年 | 104篇 |
2011年 | 156篇 |
2010年 | 123篇 |
2009年 | 134篇 |
2008年 | 123篇 |
2007年 | 139篇 |
2006年 | 110篇 |
2005年 | 157篇 |
2004年 | 127篇 |
2003年 | 97篇 |
2002年 | 73篇 |
2001年 | 55篇 |
2000年 | 36篇 |
1999年 | 53篇 |
1998年 | 52篇 |
1997年 | 38篇 |
1996年 | 43篇 |
1995年 | 48篇 |
1994年 | 31篇 |
1993年 | 42篇 |
1992年 | 29篇 |
1991年 | 20篇 |
1990年 | 20篇 |
1989年 | 10篇 |
1988年 | 17篇 |
1987年 | 5篇 |
1986年 | 10篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1980年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有2472条查询结果,搜索用时 15 毫秒
91.
内建自测试(BIST)是一种有效降低测试开销的技术,在瞬态电流测试中得到了应用。本文给出了一种新型的瞬态电流测试BIST测试生成器设计方案,该设计可以产生所需要的测试向量对,同时具有硬件开销小的优点。 相似文献
92.
瞬变电磁法在探测煤矿采空区中的应用 总被引:17,自引:3,他引:14
瞬变电磁法是目前工程勘察中应用较广的物探工作方法之一。该方法观测纯二次场,故分辨率高,可分辨出地下规模较小的不均匀体,尤其对低阻地质体反应灵敏。采空区地层有其独特的地电特征,可以利用瞬变电磁法进行探测。笔者将瞬变电磁法用于新汶某煤矿边界老窑采空区探测及河北某城镇采空区圈定,均取得良好的效果。 相似文献
93.
High pressure pipeline transportation has been an established technology for economically transporting large amounts of CO_2. However, there are still issues and associated risks that have to be effectively addressed and adequately understood. It is well known that a strong Joule-Thomson Cooling effect can occur when pressurized CO_2 flows through a choke valve. Thus, to investigate the choking characteristics especially the temperature drop of high pressure CO_2, a new laboratory scale experimental setup(total length of 14.85 m and the inner diameter of 15 mm) was constructed. Steady choked flow and transient choked flow tests were carried out respectively for pressurized CO_2 in various initial phases. The phase transitions and temperature drop characteristics were then studied following the choked flow and the results show that the phase transitions in steady choked flow differs significantly from that in transient choked flow. For transient choked flow of various initial phases, all the flows downstream would transfer from single phase to gas–liquid two-phase flow. Furthermore, the effect of water on transient choked flow of supercritical CO_2 pipeline was investigated, and the phenomena of solid particles deposition was captured which was paramount importance of ensuring the safety operation of CO_2 pipelines when throttling by the choke valves. 相似文献
94.
在还原性气氛流场瞬变温度测量中,过去一般采用全铠装式或接壳式热电偶,很难实现毫秒级的时间常数,新研制的大温变率流场中特种变送器,由镍铬-镍硅的偶丝裸露式极微细热电偶,及放大电路、冷端补偿电路和超量程限幅电路等组成的仪表放大器2部分构成,首次应用在还原性气氛流场温度测量中,获得了满足试验要求的毫秒级时间常数,其中,以精密电压基准LM385为核心器件的热电偶冷端补偿电路,在0℃-40℃环境温度范围内补偿,温度附加误差为0.2%,提高了系统测量精度。 相似文献
95.
96.
为研究狭缝节流空气静压轴承-转子系统在阶跃载荷作用下的稳定性,结合流体力学和转子动力学方程,利用动网格技术,充分考虑转子在流场作用下的非线性运动,建立轴承-转子动态耦合计算模型。利用流固耦合方法得到系统在瞬态和稳态下的轴心轨迹和流场分布。通过分析计算得到载荷作用下系统的轴心轨迹和轴承内部流场分布云图,并引入时域参数对系统的稳定性进行分析。通过改变空气轴承结构参数,研究特定转速下不同轴承参数对系统瞬态响应阶段快速性和稳定性的影响规律。结果表明:通过控制轴承的狭缝间距、深度和宽度等参数,能够改善系统的动态稳定性。 相似文献
97.
98.
采用电力系统综合程序不同精度的同步电机数学模型,基于潮流进行暂态稳定仿真计算。通过对仿真实例计算得到暂态稳定结果,分析和比较电机数学模型对暂态稳定性研究的影响。 相似文献
99.
《Ceramics International》2020,46(8):11854-11860
Wustite (FeO)-centered multicomponent oxides play an important role in the ironmaking process, and a complete understanding of their high temperature behaviors is of great importance for process optimization to achieve high efficiency and low emissions during industrial production. In this work, the transient shrinkages of FeO-centered multicomponent oxide packed beds are quantitatively determined in a reducing atmosphere up to 1773 K, and the effects of the interactions between the oxides on the shrinkage rate (SR) are qualitatively evaluated. The results show that although mixing CaO with FeO increases the SR to 0.42%/K below 1173 K, further mixing with SiO2 or Al2O3 significantly limits this enhancement effect due to the formation of an olivine or spinel phase. However, in the subsequent stage, the SR increases to as high as 0.44%/K after CO is injected. The interaction between FeO and MgO leads to an SR of greater than 0.20%/K at lower temperatures, but it causes a decrease in the SR from 0.33%/K to 0.16%/K between 1173 K and 1273 K. Meanwhile, adding SiO2 slows the reduction reaction, and the SR correspondingly decreases further to 0.04%/K. On the other hand, the interaction between CaO and Al2O3 takes precedence over the interaction between SiO2 and MgO and dominates the shrinkage process in the quinary-component case, and the preferentially formed CaAl2O4 spinel phase hinders the formation of the Mg2SiO4 olivine phase. 相似文献
100.
Mohsen Izadi 《中国化学工程学报》2020,28(5):1203-1213
This study numerically investigates the impact of porous materials, nano-particle types, and their concentrations on transient natural convection heat transfer of nano-fluid inside a porous chamber with a triangular section. The governing equations of the two-phase mixture model are separated on the computational domain and solved using the Finite Volume Method, taking into account the Darcy–Brinkman model for porous medium. It was observed that convection heat transfer inside the triangular chamber consists of three stages named initial, transient, and semi-steady. The features of each step are provided in detail. The results suggested that the use of a hybrid nano-fluid(water/aluminum oxide-cooper) inside a porous glass material and an increase in volume fraction of nano-particles have adverse effects on heat transfer rate. In contrast, as the nano-particle volume fraction of the single nano-fluid(water/aluminum oxide) inside the chamber increased, convection heat transfer rate improved. At the same time, it was observed that the use of both nano-fluids(single and hybrid) in the porous environment of the aluminum foam could improve convection. 相似文献