全文获取类型
收费全文 | 54510篇 |
免费 | 5198篇 |
国内免费 | 3178篇 |
专业分类
电工技术 | 3721篇 |
技术理论 | 1篇 |
综合类 | 4630篇 |
化学工业 | 7854篇 |
金属工艺 | 4594篇 |
机械仪表 | 2626篇 |
建筑科学 | 4291篇 |
矿业工程 | 2169篇 |
能源动力 | 3548篇 |
轻工业 | 3712篇 |
水利工程 | 1482篇 |
石油天然气 | 2743篇 |
武器工业 | 650篇 |
无线电 | 4573篇 |
一般工业技术 | 5742篇 |
冶金工业 | 5259篇 |
原子能技术 | 1297篇 |
自动化技术 | 3994篇 |
出版年
2024年 | 205篇 |
2023年 | 699篇 |
2022年 | 1363篇 |
2021年 | 1643篇 |
2020年 | 1894篇 |
2019年 | 1528篇 |
2018年 | 1469篇 |
2017年 | 1945篇 |
2016年 | 2126篇 |
2015年 | 2161篇 |
2014年 | 3494篇 |
2013年 | 3631篇 |
2012年 | 4208篇 |
2011年 | 4376篇 |
2010年 | 3234篇 |
2009年 | 3224篇 |
2008年 | 2775篇 |
2007年 | 3514篇 |
2006年 | 3067篇 |
2005年 | 2577篇 |
2004年 | 2220篇 |
2003年 | 1949篇 |
2002年 | 1639篇 |
2001年 | 1375篇 |
2000年 | 1199篇 |
1999年 | 968篇 |
1998年 | 789篇 |
1997年 | 668篇 |
1996年 | 601篇 |
1995年 | 503篇 |
1994年 | 376篇 |
1993年 | 287篇 |
1992年 | 249篇 |
1991年 | 195篇 |
1990年 | 174篇 |
1989年 | 125篇 |
1988年 | 75篇 |
1987年 | 57篇 |
1986年 | 49篇 |
1985年 | 47篇 |
1984年 | 51篇 |
1983年 | 35篇 |
1982年 | 32篇 |
1981年 | 15篇 |
1980年 | 22篇 |
1978年 | 7篇 |
1977年 | 3篇 |
1975年 | 9篇 |
1959年 | 10篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
通过有限元数值模拟方法得出滚珠旋压中薄壁管在不同凹模旋转速度条件下轴向进给比的变化规律及工件的成形规律,并对模拟结果的等效应变分布做了分析,并与实验结果进行比较,给出薄壁管滚珠旋压时进给比的选取范围.结果表明,进给比对滚珠旋压中薄壁管直径的胀缩和工件的质量有着显著的影响.另外,从计算的模具所受的三向载荷变化情况分析了模具的使用寿命. 相似文献
73.
姚新荣 《河南纺织高等专科学校学报》2007,19(3):24-27
2006年2月15日财政部颁布的《企业会计准则》中有多处要求采用实际利率法计算摊余成本和利息,而会计职称考试用书等资料则采用列表形式。本文在分析实际利率法内涵的基础上,通过若干实例解析了利用账簿记录计算各期摊余成本。 相似文献
74.
Yu. V. Balaban-Irmenin N. G. Fokina 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2007,41(5):306-312
The effect of internal-corrosion inhibitors on heating-system pipelines is investigated. Tests were conducted on a testing
device for polarization measurements under conditions corresponding to the Rostov Heat-Supply System. The concentration of
OEDP-zinc, which provides a high degree of protection from general corrosion, is determined. The reagent has been successfully
incorporated into the Rostov No. 2 TPP.
__________
Translated from élektricheskie Stantsii, No. 7, July 2007, pp. 37–43. 相似文献
75.
In various medium‐to‐large‐scale fire test equipments like the ISO room corner test (RC), and more recently, the single burning item test (SBI) the mass flow rate measurement of the combustion gases plays a key role in the determination of the heat‐release rate and smoke‐production rate. With the knowledge of the velocity profile and the temperature of the flow, the mass flow rate is obtained by measuring the velocity on the axis of the duct. This is done by means of a bi‐directional probe based on the pitot principle. However, due to the variation of the mean temperature and the temperature gradient in any cross section of the duct, introduced by ever changing combustion gas temperatures, the velocity nor the density profile are constant in time. This paper examines the resulting uncertainty on the mass flow rate. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
76.
77.
78.
Madden Gregory J.; Begotka Andrea M.; Raiff Bethany R.; Kastern Lana L. 《Canadian Metallurgical Quarterly》2003,11(2):139
The degree to which real and hypothetical rewards were discounted across delays ranging from 6 hr to 1 year was explored in a within-subjects design. An adjusting-amounts procedure was used to estimate the subjective value of real and hypothetical rewards at each delay. A hyperbolic discounting function provided a significantly better fit to individual participants' preferences than did an exponential function. No significant effect of reward type on degree of hyperbolic discounting or area under the discounting curves was detected. These findings offer some support for the validity of using hypothetical rewards to estimate discounting rates in substance-abusing and other populations, but caution is suggested because this support is gleaned from a failure to detect an effect of reward type. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
79.
A. G. ATKINS Z. CHEN B. COTTERELL 《Fatigue & Fracture of Engineering Materials & Structures》2003,26(1):67-77
In this paper, energy dissipation rate D vs. Δa curves in ductile fracture are predicted using a ‘conversion’ between loads, load‐point displacements and crack lengths predicted by NLEFM and those found in real ELPL propagation. The NLEFM/ELPL link was recently discovered for the DCB testpiece, and we believe it applies to other cracked geometries. The predictions for D agree with experimental results. The model permits a crack tip toughness R(Δa) which rises from Jc and saturates out when (if) steady state propagation is reached after a transient stage in which all tunnelling, crack tip necking and shear lip formation is established. JR is always greater than the crack tip R(Δa) and continues to rise even after R(Δa) levels off. The analysis is capable of predicting the usual D vs. Δa curves in the literature which have high initial values and fall monotonically to a plateau at large Δa. It also predicts that D curves for CCT testpieces should be higher than those for SENB/CT, as found in practice. The possibility that D curves at some intermediate Δa may dip to a minimum below the levelled‐off value at large Δa is predicted and confirmed by experiment. Recently reported D curves that have smaller initial D than the D‐values after extensive propagation can also be predicted. The testpiece geometry and crack tip R(Δa) conditions required to produce these different‐shaped D vs. Δa curves are established and confirmed by comparison with experiment. The energy dissipation rate D vs. Δa is not a transferable property as it depends on geometry. The material characteristic R(Δa) may be the ‘transferable property’ for scaling problems in ELPL fracture. How it can be deduced from D vs. Δa curves (and by implication, JR vs. Δa curves) is established. 相似文献
80.
针对加热炉汽化冷却系统所产饱和蒸汽在非采暖期大量放散的现状,通过实例提出可用这类蒸汽制冷,作为夏季某些单位空调之用。这样就可以用较少的投资解决非采暖期的汽冷余热浪费问题,合理利用热能,降低轧钢成本。 相似文献