全文获取类型
收费全文 | 113880篇 |
免费 | 3382篇 |
国内免费 | 1586篇 |
专业分类
电工技术 | 2320篇 |
技术理论 | 2篇 |
综合类 | 4067篇 |
化学工业 | 16709篇 |
金属工艺 | 6669篇 |
机械仪表 | 5032篇 |
建筑科学 | 4571篇 |
矿业工程 | 1577篇 |
能源动力 | 1909篇 |
轻工业 | 5329篇 |
水利工程 | 1820篇 |
石油天然气 | 2455篇 |
武器工业 | 217篇 |
无线电 | 12448篇 |
一般工业技术 | 19898篇 |
冶金工业 | 4231篇 |
原子能技术 | 610篇 |
自动化技术 | 28984篇 |
出版年
2024年 | 123篇 |
2023年 | 577篇 |
2022年 | 928篇 |
2021年 | 1278篇 |
2020年 | 1061篇 |
2019年 | 798篇 |
2018年 | 15261篇 |
2017年 | 14238篇 |
2016年 | 10802篇 |
2015年 | 1780篇 |
2014年 | 1705篇 |
2013年 | 2019篇 |
2012年 | 5047篇 |
2011年 | 11302篇 |
2010年 | 9981篇 |
2009年 | 7219篇 |
2008年 | 8347篇 |
2007年 | 9304篇 |
2006年 | 1801篇 |
2005年 | 2607篇 |
2004年 | 2039篇 |
2003年 | 2025篇 |
2002年 | 1300篇 |
2001年 | 743篇 |
2000年 | 878篇 |
1999年 | 906篇 |
1998年 | 778篇 |
1997年 | 692篇 |
1996年 | 610篇 |
1995年 | 491篇 |
1994年 | 387篇 |
1993年 | 286篇 |
1992年 | 220篇 |
1991年 | 184篇 |
1990年 | 120篇 |
1989年 | 105篇 |
1988年 | 101篇 |
1987年 | 53篇 |
1986年 | 53篇 |
1968年 | 43篇 |
1967年 | 33篇 |
1966年 | 43篇 |
1965年 | 44篇 |
1960年 | 30篇 |
1959年 | 35篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Ming Zhou Henry Hu Naiyi Li Jason Lo 《Journal of Materials Engineering and Performance》2005,14(4):539-545
High-pressure die cast magnesium alloy AM50 is currently used extensively in large and complex shaped thin-wall automotive
components. For further expansion of the alloy usage in automobiles, novelmanufacturing processes need to be developed. In
this study, squeeze casting of AM50 alloy with a relatively thick cross section was carried out using a hydraulic press with
an applied pressure of 70 MPa. Microstructure and mechanical properties of the squeeze cast AM50 with a cross-section thickness
of 10 mm were characterized in comparison with the die cast counterpart. The squeeze cast AM50 alloy exhibits virtually no
porosity in the microstructure as evaluated by both optical microscopy and the density measurement technique. The results
of tensile testing indicate the improved tensile properties, specifically ultimate tensile strength and elongation, for the
squeeze cast samples over the conventional high-pressure die cast parts. The analysis of tensile behavior show that the strain-hardening
rate during the plastic deformation of the squeeze cast specimens is constantly higher than that of the die cast specimens.
The scanning electron microscopy fractography evidently reveals the ductile fracture features of the squeeze cast alloy AM50. 相似文献
982.
983.
984.
Gang Liu Zhongqin Lin Youxia Bao J. Cao 《Journal of Materials Engineering and Performance》2002,11(1):64-70
Springback is the main concern in U-shaped part forming, which would adversely affect desired part geometries. The use of
variable blankholder force in the forming process is one effective method to reduce springback. However, there has not been
a systematic way to determine the blankholder force trajectory. In this article, a methodology of obtaining this blankholder
force trajectory in forming a U-shaped part that considers the wrinkling limit and fracture limit in the forming process was
proposed. The method was validated numerically by using the Finite Element Method to simulate the benchmark of a 2-D draw
bending problem in NUMISHEET’93. With the calculated blankholder force trajectory, higher forming quality was obtained and
compared with constant blankholder force cases. Springback was kept at a minimum while avoiding cracking. 相似文献
985.
简要叙述不锈钢板冷轧机(20辊森吉米尔轧机、四柱式2O辊轧机、12辊CR轧机等)的结构特点、发展概况及各自采用的先进控制系统。 相似文献
986.
Edward J. Daniels Joseph A. CarpenterJr. Claudia Duranceau Michael Fisher Candace Wheeler Gerald Winslow 《JOM Journal of the Minerals, Metals and Materials Society》2004,56(8):28-32
Approximately 15 million cars and trucks reach the end of their useful life in the United States each year. More than 75%
of the materials from end-of-life vehicles are profitably recovered and recycled by the private sector; automotive materials
recycling is a success story. To achieve greater fuel efficiency and safety, today’s cars incorporate an increasing share
of innovative light-weight materials. While these materials greatly enhance efficiency during vehicle use, they can present
special challenges for recycling. These challenges will persist as automotive designs and the mix of materials used in vehicles
continue evolving to further improve safety and performance. To meet the challenges of automotive materials recycling, the
U.S. Department of Energy has recently expanded its collaborative research with industry in this area. This article discusses
this collaborative government/industry approach to sustainable end-of-life vehicle recycling.
For more information, contact Edward J. Daniels, Argonne National Laboratory, 9700 S. Cass Avenue, Building 362, Room C393,
Argonne, IL 60439-4815; (630) 252-5279; fax (630) 252-1342; e-mail edaniels@anl.gov. 相似文献
987.
通过大量缓蚀、阻垢实验,着重介绍了钼磷系缓蚀阻垢剂SK-107在高碱度水且局部漏氨的合成氨循环水系统中的缓蚀、阻垢性能。 相似文献
988.
989.
本文阐述了热模钢的脆性与热疲劳测定方法,比较了常规热处理试样与渗猛处理试样的脆性行为和热疲劳特性。经金相观察、硬度测定、扫描电镜的电子探针和能谱分析、X射线衍射分析及声发射、热疲劳等试验,结果表明:渗锰试样的脆性低于常规处理试样,其耐热疲劳性则高于常规热处理试样。 相似文献
990.
本文结合专为哈尔滨制氧机厂开发的实用CAPP系统,对CAPP系统的研制进行了探索性的研究。以Windows作为开发平台,运用了面向对象程序设计语言与特征造型技术的输入方法。最后简单介绍了本系统的决策和输出模块。 相似文献