全文获取类型
收费全文 | 141744篇 |
免费 | 16810篇 |
国内免费 | 12163篇 |
专业分类
电工技术 | 13938篇 |
综合类 | 14950篇 |
化学工业 | 17001篇 |
金属工艺 | 10116篇 |
机械仪表 | 9662篇 |
建筑科学 | 11358篇 |
矿业工程 | 5419篇 |
能源动力 | 3847篇 |
轻工业 | 15656篇 |
水利工程 | 5213篇 |
石油天然气 | 4290篇 |
武器工业 | 2055篇 |
无线电 | 15420篇 |
一般工业技术 | 12196篇 |
冶金工业 | 5553篇 |
原子能技术 | 2479篇 |
自动化技术 | 21564篇 |
出版年
2024年 | 921篇 |
2023年 | 2349篇 |
2022年 | 5325篇 |
2021年 | 6825篇 |
2020年 | 4939篇 |
2019年 | 3582篇 |
2018年 | 3749篇 |
2017年 | 4449篇 |
2016年 | 3792篇 |
2015年 | 6071篇 |
2014年 | 7683篇 |
2013年 | 9030篇 |
2012年 | 11396篇 |
2011年 | 12161篇 |
2010年 | 11476篇 |
2009年 | 11390篇 |
2008年 | 11558篇 |
2007年 | 11512篇 |
2006年 | 10087篇 |
2005年 | 8136篇 |
2004年 | 6106篇 |
2003年 | 4148篇 |
2002年 | 3930篇 |
2001年 | 3676篇 |
2000年 | 2809篇 |
1999年 | 1109篇 |
1998年 | 456篇 |
1997年 | 324篇 |
1996年 | 287篇 |
1995年 | 223篇 |
1994年 | 182篇 |
1993年 | 182篇 |
1992年 | 145篇 |
1991年 | 130篇 |
1990年 | 96篇 |
1989年 | 106篇 |
1988年 | 71篇 |
1987年 | 48篇 |
1986年 | 48篇 |
1985年 | 25篇 |
1984年 | 20篇 |
1983年 | 15篇 |
1982年 | 14篇 |
1981年 | 15篇 |
1980年 | 37篇 |
1979年 | 36篇 |
1973年 | 1篇 |
1959年 | 24篇 |
1958年 | 2篇 |
1951年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
For multi-step heterogeneous consecutive reactions affected entirely by interphase diffusion under isothermal condition, the
equations for the effectiveness factors, the surface concentrations and the point yields were derived in terms of the Damkoehler
numbers or the measurables from the mass balances set up on the assumption that the mass-transfer rate balances the surface-reaction
rate at steady state.
From the analyses of the equations derived, the effectiveness factors for the intermediate steps and the surface concentrations
of intermediates were understood to be enhanced by the measurables inclusive of the concentrations and the mass-transfer coefficients.
Then the effect of the concentrations was concluded to be most significant. The effects of these measurables to the effectiveness
factors and the surface concentrations were qualitatively discussed for simple consecutive reactions and also for additive
consecutive reactions. Especially, as for two-step additive consecutive reactions, the effects of measurables η Da and the
concentrations to the effectiveness factors were examined with graphical presentations.
Finally, the brief discussion of the dependency of the Damkoehler number upon reaction time and the effect of the Renolds
number and diffusivity to the extent of the mass-transfer resistance were presented. 相似文献
84.
85.
大黑汀大坝安全监测应用分析软件的开发与应用 总被引:1,自引:1,他引:0
周世虎 《水电自动化与大坝监测》2007,31(4):48-50,63
在大坝安全监测工作中,结合实际工程情况和工作需要,利用Visual Basic 6.0编程语言,开发出一套实用的安全监测应用分析软件,解决了数据共享、监测成果检查、自动化与人工测值比较、各种数据报表输出、历史数据提取、过程线分布图绘制等许多实际应用问题,极大地提高了工作效率,实现了大坝安全监测自动化。 相似文献
86.
87.
ZHANG Hui-juan HUI Shi-en ZHOU Qu-lan 《国际设备工程与管理》2007,12(1):36-41
The purpose of this paper is to present the flow field in the 300MW tangential firing utility boiler that used the Low NOx Concentric Firing System (LNCFS). Using the method of cold isothermal simulation ensures the geometric and boundary condition similarity. At the same time the condition of self-modeling is met. The experimental results show that the mixture of primary air and secondary air becomes slower, the average turbulence magnitude the relative diameter of the tangential firing enlarges of the main combustion zone becomes less and when the secondary air deflection angle increases When the velocity pressure ratio of the secondary air to the primary air (p2/p1) enlarges, the mixture of the secondary air and the primary air becomes stronger, the average turbulence magnitude of the main combustion zone increases, and the relative diameter of the tangential firing becomes larger. Because the over fire air (OFA) laid out near the wall has a powerful penetration, the relative diameter of the tangential firing on the section of the OFA is very little, but the average turbulence magnitude is great. When the velocity pressure ratio of the OFA to the primary air POFA/p1 increases, the relative diameter of the tangential firing on the section of the OFA grows little, the average turbulence magnitude becomes larger and the penetration of the OFA becomes more powerful. 相似文献
88.
本文在浅埋地下建筑风冷热泵空调系统围护结构传热动态模拟的基础上,通过对南京市太园地下旅社围护结构传热的实时测试,验证动态传热模型及计算机模拟方法的可行性和正确性,为浅埋地下建筑风冷热泵空调系统的装机容量、节能指标和设计计算提供一定的理论依据。 相似文献
89.
ZHOU Yuzhu 《中国标准化(英文版)》2007,23(5)
Constructive research of a market-oriented industry's system of technical standardization by redefining those technical standards is the basis of innovation. Through considering and implementing innovation of the industry's standards,rapid development and standardization of the industry can be achieved. 相似文献
90.