全文获取类型
收费全文 | 25722篇 |
免费 | 2137篇 |
国内免费 | 1257篇 |
专业分类
电工技术 | 1270篇 |
综合类 | 2669篇 |
化学工业 | 2675篇 |
金属工艺 | 2419篇 |
机械仪表 | 4855篇 |
建筑科学 | 2935篇 |
矿业工程 | 959篇 |
能源动力 | 466篇 |
轻工业 | 1024篇 |
水利工程 | 619篇 |
石油天然气 | 824篇 |
武器工业 | 336篇 |
无线电 | 1620篇 |
一般工业技术 | 3615篇 |
冶金工业 | 960篇 |
原子能技术 | 274篇 |
自动化技术 | 1596篇 |
出版年
2024年 | 104篇 |
2023年 | 322篇 |
2022年 | 536篇 |
2021年 | 688篇 |
2020年 | 750篇 |
2019年 | 675篇 |
2018年 | 639篇 |
2017年 | 895篇 |
2016年 | 935篇 |
2015年 | 1025篇 |
2014年 | 1360篇 |
2013年 | 1507篇 |
2012年 | 1647篇 |
2011年 | 1916篇 |
2010年 | 1362篇 |
2009年 | 1426篇 |
2008年 | 1389篇 |
2007年 | 1734篇 |
2006年 | 1623篇 |
2005年 | 1321篇 |
2004年 | 1124篇 |
2003年 | 1035篇 |
2002年 | 819篇 |
2001年 | 709篇 |
2000年 | 628篇 |
1999年 | 581篇 |
1998年 | 367篇 |
1997年 | 420篇 |
1996年 | 333篇 |
1995年 | 278篇 |
1994年 | 220篇 |
1993年 | 145篇 |
1992年 | 129篇 |
1991年 | 107篇 |
1990年 | 77篇 |
1989年 | 77篇 |
1988年 | 88篇 |
1987年 | 38篇 |
1986年 | 15篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 10篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 9篇 |
1959年 | 2篇 |
1958年 | 2篇 |
1957年 | 2篇 |
1956年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
81.
Cutting force estimation in sculptured surface milling 总被引:10,自引:5,他引:10
A. Lamikiz L. N. Lpez de Lacalle J. A. Snchez M. A. Salgado 《International Journal of Machine Tools and Manufacture》2004,44(14):1511-1526
Cutting force milling models developed up to now are mostly used for planar milling using end-mills. Only a reduced number of models applying ball-end mills have been developed. Furthermore these models usually only consider horizontal surface machining, even though the main application of ball-end mills is sculptured surface machining. This article proposes a model that is able to estimate the cutting forces in inclined surfaces machined both up-milling and down-milling. For this purpose a semi-mechanistic model has been developed that calculates the cutting forces based on a set of coefficients which depend on the material, the tool, the cutting conditions, the machining direction and the slope of the surface.A coordinate transformation has been included in order to consider the slope milling case with different cutting directions.The model has been tested on two materials, an aluminum alloy Al7075-T6 and a 52 HRC tool steel AISI H13. Validation tests have been carried out on inclined planes using different slopes and different machining directions.The results provide errors below 10% in most of the cases and both the value and shape of the predicted forces adjust the measured cutting force. 相似文献
82.
XIE Changsheng SUN Peizhen ZHAO Jiansheng CHEN Yuqiu Huazhong University of Science Technology Wuhan China XIE Changsheng Associate Professor Department of Mechanical Engineering No. Huazhong University of Science Technology Wuhan China 《金属学报(英文版)》1990,3(1):52-57
The microstructures of Fe-Mn-Ni-Cr steels with medium carbon and the effect of alloy ele-ments on them have been investigated by means of X-ray diffraction quantitative phase ana-lyses,metallography and hardness tests.The volume fraction of martensite in steels quenchedat 1100℃ can be expressed as:f_M~(1100)=162.643-15.482Mn-7.36Ni-4.286(Cr+Mo+V)Based on this expression,the quasi-equilibrium microstructure diagram has been obtained.Itis shown that the effect of Mn on the austenite stability is greater than that of Ni.The equiva-lent [Ni]=2.104Mn+Ni and equivalent [Cr]=Cr+Mo+V.The driving force for martensite transformation at M_s point has been calculated to hedrastically decreased by element Mn. 相似文献
83.
LI Yundong ZHANG Tianxiang ZHENG Zhi ZHU Yaoxiao Institute of Metal Research Academia Sinica Shenyang China Professor Institute of Metal Research Academia Sinica Shenyang China 《金属学报(英文版)》1990,3(6):393-397
The solid solubilities of 15 common alloying elements added to the Ll_2-type intermetalliccompound Ni_3Si at 900°C have been estimated,and their substitution modes have been de-duced from the direction of solubility lobe of the compound.It is shown that the alloyingbehaviours in Ni_3Si are determined by both size and electronic factors,i.e.,the substitutionmode is governed by electronic configuration and solubility by the both.An interactionparameter is presented to describe quantitatively the influence of electronic configuration onsubstitution mode and the solubility limit can be successfully explained together with atom radius. 相似文献
84.
本文利用X射线定量相分析及金相观察和硬度测试,考察了中碳Fe-Mn-Ni-Cr钢的组织及合金元素的作用。建立了经1100℃淬火后的马氏体体积分数与合金成分的定量关系式; f_M~(1100)=162.643-15.482Mn-7.36Ni-4.286(Cr+Mo+V)并在此基础上给出了亚平衡组织图。结果表明,Mn稳定奥氏体的作用大于Ni的作用。Ni和Cr当量分别以[Ni]=2.104Mn+Ni,[Cr]=Cr+Mo+V表示。计算了M_S点处的马氏体相变驱动力,指出Mn具有强烈降低相变驱动力的作用。 相似文献
85.
86.
Hiroyuki?Y.?SuzukiEmail author Hidenori?Kuroki 《Metals and Materials International》2004,10(2):185-191
A new compacting method for powder materials is presented. High-Speed Centrifugal Compaction Process (HCP) utilizes centrifugal
force of about 10,000 g for the compaction. HCP is suitable for net shape compaction of fine sub-micron and nano-powders.
HCP possesses a unique compacting mechanism that is different from other colloidal processes including Pressure Casting (PC),
and has a number of useful characteristics. HCP has a higher compacting speed than PC, wide applicability for net shape formation,
as well as a defect removing function. Because of homogeneous and flawless green microstructure, HCP alumina shows superior
sinterability and higher strength and hardness than most of other aluminas.
This article is based on a presentation made in the symposium “The 3rd KIM-JIM Joint Symposium on Advanced Powder Materials“,
held at Korea University, Seoul, Korea, October 26–27, 2001 under auspices of The Korean Institute of Metals and Materials
and The Japan Institute of Metals. 相似文献
87.
以一台振动筛的故障处理为例,说明振动机械的激振与运动特点、调整原理及其应用。介绍用计算机计算参振零部件及设备质心的方法。 相似文献
88.
89.
90.
针对单机架可逆式冷轧机生产过程中,由于不同热轧生产厂的热轧板形原料性能、板形差别较大、从而造成弯辊力预设定值和实际指标相差较大的问题,利用现场生产工艺数据丰富,采用人工智能BP神经网络的方法,通过大量数据输入进行训练,大大的提高了生产过程中弯辊力预设定值的准确性。 相似文献