全文获取类型
收费全文 | 27622篇 |
免费 | 2331篇 |
国内免费 | 931篇 |
专业分类
电工技术 | 1369篇 |
技术理论 | 1篇 |
综合类 | 2127篇 |
化学工业 | 2195篇 |
金属工艺 | 5291篇 |
机械仪表 | 5600篇 |
建筑科学 | 1747篇 |
矿业工程 | 769篇 |
能源动力 | 703篇 |
轻工业 | 1799篇 |
水利工程 | 243篇 |
石油天然气 | 856篇 |
武器工业 | 402篇 |
无线电 | 742篇 |
一般工业技术 | 3666篇 |
冶金工业 | 2253篇 |
原子能技术 | 129篇 |
自动化技术 | 992篇 |
出版年
2024年 | 229篇 |
2023年 | 548篇 |
2022年 | 769篇 |
2021年 | 871篇 |
2020年 | 952篇 |
2019年 | 783篇 |
2018年 | 855篇 |
2017年 | 1058篇 |
2016年 | 1066篇 |
2015年 | 1024篇 |
2014年 | 1419篇 |
2013年 | 1416篇 |
2012年 | 1486篇 |
2011年 | 1805篇 |
2010年 | 1378篇 |
2009年 | 1502篇 |
2008年 | 1289篇 |
2007年 | 1696篇 |
2006年 | 1685篇 |
2005年 | 1358篇 |
2004年 | 1256篇 |
2003年 | 1034篇 |
2002年 | 920篇 |
2001年 | 809篇 |
2000年 | 624篇 |
1999年 | 542篇 |
1998年 | 434篇 |
1997年 | 431篇 |
1996年 | 369篇 |
1995年 | 300篇 |
1994年 | 218篇 |
1993年 | 149篇 |
1992年 | 120篇 |
1991年 | 89篇 |
1990年 | 79篇 |
1989年 | 70篇 |
1988年 | 59篇 |
1987年 | 40篇 |
1986年 | 18篇 |
1985年 | 22篇 |
1984年 | 21篇 |
1983年 | 21篇 |
1982年 | 21篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 3篇 |
1965年 | 4篇 |
1964年 | 5篇 |
1963年 | 3篇 |
1959年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
M 2highspeedsteel (M 2steel)isamaterialwidelyusedintoolsanddies[1,2 ] .M 2steelischarac terizedbyalongsolidificationrangeandcomplexeu tecticreactions ,whichresultsinsegregationofalloy ingelementsandformationofseveraldifferenttypesofcarbidesduringsolidification[3,4 ] .Forconventionallyprocessedhigh speedsteels ,itisinevitablethatacoarsecarbidenetworkwillbeformedduringsolidifi cation .Coarseprimarycarbidestendtoresultinun evencarbidebandsdistributionafterasubstantialamountofhotprocessing[5] .Ma… 相似文献
72.
Haley William E.; Larson Dale G.; Kasl-Godley Julia; Neimeyer Robert A.; Kwilosz Donna M. 《Canadian Metallurgical Quarterly》2003,34(6):626
Professional psychologists are increasingly likely to encounter opportunities to work with patients and families facing end-of-life issues. Psychologists can provide psychological assessment, intervention for patients and families, consultation with and support of health care team members, grief therapy, and program development and evaluation. Psychological services are useful for healthy individuals who wish to make thoughtful plans about their own future care, patients with life-limiting illnesses, families stressed by providing end-of-life care, bereaved individuals, and health care providers who face issues of burnout and strain. Several challenges for psychologists working in end-of-life care are noted, including training, development of clear roles, and reimbursement. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
73.
74.
No authorship indicated 《Canadian Metallurgical Quarterly》2004,59(5):352
The 2004 Gold Medal Award for Life Achievement in the Application of Psychology was awarded to Edwin A. Fleishman, for his significant contributions to the science and applications of psychology, which he has sustained over his remarkable career. He is cited for his research, which has had a profound influence on our understanding of human capabilities, their measurement, their development, and their application in the world of work. Through his many influential leadership roles, as president of the International Association of Applied Psychology and three divisions of the American Psychological Association, and as editor of the Journal of Applied Psychology, he has helped shape our profession. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
75.
76.
W. J. PLUMBRIDGE Y. KARIYA 《Fatigue & Fracture of Engineering Materials & Structures》2004,27(8):723-734
With continuing miniaturisation, increased performance demands and the requirement to remove lead from solder alloys, the challenges to structural integrity and reliability of electronic equipment are substantial and increasing. This paper outlines typical features in electronic equipment of which the structural integrity community may be generally unaware. Potential failure modes in service are described, and the problems of scale and material characteristics are considered. Progress in the application of fracture mechanics to the life prediction of interconnections is reviewed. The limited evidence available suggests that the crack growth resistance of silver‐containing lead‐free solders is superior to that of the traditional Sn‐37Pb under cycle‐controlled conditions but there is no difference when time‐dependent conditions prevail. In several respects, it is contended that the electronics sector is faced with challenges at least equivalent to those encountered in gas turbines and nuclear power generation. 相似文献
77.
超动型长寿命铅蓄电池池的几点建议 总被引:1,自引:1,他引:0
报导了国内外起动用长寿命铅酸蓄电池的概况,根据笔多年积累的经验并针对这类电池的应用特点,具体介绍了起动型铅酸蓄电池在原辅材料,零部件,生产设备和制造工艺等方面如何采取有效措施以提高这类电池的使用寿命。 相似文献
78.
用扫描电子显微镜(SME)和X-射线能谱分析法(EDX)对铜纤维增强的半金属摩阻材料与灰铸铁对偶滑摩后的摩擦表面进行了分析,研究了摩阻材料中铜纤维的摩擦磨损行为.结果表明,在摩擦磨损过程中,摩阻材料摩擦表面上铜的分布更加弥散化,并且铜纤维具有集铁作用,因而摩阻材料摩擦表面上形成了富铁贫铜表面工作层;铜能从摩阻材料摩擦表面转移到对偶摩擦表面,故对偶摩擦面上分布一定量铜,这是摩擦副具有稳定摩擦系数和良好耐磨性的关键因素;铜纤维取向对摩阻材料摩擦磨损行为有显着影响. 相似文献
79.
本文采用挤压浸渗法 ,制得不同稀土含量的硅酸铝短纤维增强铝基复合材料。用光学显微镜观察了复合材料的铸造显微组织 ,分析了稀土含量对共晶硅组织形态的影响 ;用扫描电镜对复合材料基体中的稀土相进行了观察 ,探索了稀土相的分布位置及其形态 ;并对不同稀土含量的复合材料进行了摩擦磨损实验 ,结果表明稀土能增强复合材料的耐磨性 相似文献
80.
Experimental results of a low-power roadheader driving a gallery with different types of rock at the face 总被引:1,自引:0,他引:1
J. Torao lvarez M. Menndez lvarez R. Rodríguez Díez 《Tunnelling and Underground Space Technology incorporating Trenchless Technology Research》2003,18(4):395-404
In this paper, the experimental results of a 45-kW and 15-t roadheader excavating a gallery with two different types of rock at the face using two different cutting heads are shown. It is proved that the roadheader works properly with both cutting heads. In comparison with other results in the literature, the principal parameters, i.e. specific energy, cutting rate and tool wear, are at a level that can be considered satisfactory taking into account the low power of the roadheader. On the other hand, the influence of the number of picks, which is the main difference between the two cutting heads, on the operational parameters is shown. 相似文献