全文获取类型
收费全文 | 36393篇 |
免费 | 3098篇 |
国内免费 | 2161篇 |
专业分类
电工技术 | 960篇 |
综合类 | 3708篇 |
化学工业 | 2699篇 |
金属工艺 | 3378篇 |
机械仪表 | 3276篇 |
建筑科学 | 8075篇 |
矿业工程 | 1362篇 |
能源动力 | 930篇 |
轻工业 | 1409篇 |
水利工程 | 1821篇 |
石油天然气 | 2985篇 |
武器工业 | 249篇 |
无线电 | 1473篇 |
一般工业技术 | 5695篇 |
冶金工业 | 1734篇 |
原子能技术 | 294篇 |
自动化技术 | 1604篇 |
出版年
2024年 | 110篇 |
2023年 | 284篇 |
2022年 | 728篇 |
2021年 | 847篇 |
2020年 | 969篇 |
2019年 | 900篇 |
2018年 | 755篇 |
2017年 | 1080篇 |
2016年 | 1180篇 |
2015年 | 1269篇 |
2014年 | 1948篇 |
2013年 | 1916篇 |
2012年 | 2346篇 |
2011年 | 2568篇 |
2010年 | 2056篇 |
2009年 | 2318篇 |
2008年 | 2121篇 |
2007年 | 2733篇 |
2006年 | 2383篇 |
2005年 | 2136篇 |
2004年 | 1716篇 |
2003年 | 1550篇 |
2002年 | 1373篇 |
2001年 | 1117篇 |
2000年 | 978篇 |
1999年 | 762篇 |
1998年 | 659篇 |
1997年 | 574篇 |
1996年 | 438篇 |
1995年 | 376篇 |
1994年 | 296篇 |
1993年 | 238篇 |
1992年 | 184篇 |
1991年 | 149篇 |
1990年 | 139篇 |
1989年 | 126篇 |
1988年 | 74篇 |
1987年 | 43篇 |
1986年 | 21篇 |
1985年 | 24篇 |
1984年 | 39篇 |
1983年 | 35篇 |
1982年 | 27篇 |
1981年 | 8篇 |
1980年 | 11篇 |
1979年 | 17篇 |
1978年 | 5篇 |
1964年 | 3篇 |
1962年 | 4篇 |
1959年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
991.
Hot Dip Aluminized Coatings with different thickness were prepared on Q235 steel in aluminum solutions with different temperature for certain time. Through tensile tests and in-situ SEM observations, the effect of the coating's microstructure on the tensile strength of the samples was studied. It was disclosed at certain aluminum solution temperature,transaction layers mainly composed of Fe2 Al5 phase got thicker with time prolonging, and this changed initial crack's extending direction from parallel with to vertical with stretching direction. The change in crack direction decreased tensile strength of samples, thus made the coating easy to break. It was concluded that the existence of thick Fe2 Al5 phase layer was the basic reason for the lowering of tensile strength of the coating. 相似文献
992.
Thermal barrier coatings generally consist of a metallic substrate which is the primary structural component, a metallic bond coat which serves as oxygen diffusion barrier, a very thin layer of thermally grown oxide and a ceramic top coat that provides the main thermal shielding. Homogeneous ceramic coatings as top coats appear to have certain undesirable features such as high residual and thermal stresses, generally low toughness and relatively poor bonding strength. The new concept of compositional grading of the top coat may help to overcome some of these shortcomings by eliminating the material property discontinuities. A common mode of failure in thermal barrier coatings seems to be the debonding of the top coat. In this study the related interface crack problem for a graded ceramic/metal top coat is considered. It is assumed that the thermophysical properties of the top coat continuously vary between that of the bond coat at the top coat-bond coat interface and that of the ceramic at and near the free surface. The main objective of the study is to examine the influence of the material nonhomogeneity parameters and relative dimensions on the stress intensity factors and the crack opening displacements. 相似文献
993.
通过金相检验分析了珠海发电厂700MW机组中压调门阀座裂纹产生的原因、机理,详细介绍了裂纹的处理工艺和过程,为进口机组大型铸件裂纹的处理提供了正确的方法. 相似文献
994.
采用对比试验方法,通过热疲劳裂纹扩展速率和氧化增重试验,研究了燃煤锅炉燃烧器喷嘴常用的两种材料的热疲劳性能和高温氧化性能,结果表明,铬、锰、硅等元素含量高的新材料ZG40Cr26Ni4Mn3NRe的热疲劳性能和抗高温氧化性能均明显优于原燃烧器喷嘴材料ZG40Cr20Ni5.材料的抗热疲劳性能在很大程度上取决于材料的抗高温氧化性能,热疲劳裂纹在表面缺陷处最易出现,热循环过程中氧化膜的形成和破裂加剧了热疲劳裂纹的萌生和扩展. 相似文献
995.
996.
2003年,太钢开发冶炼一种新的品种钢——车轮钢,这种钢是铁道部指定货车(客车)车轮使用的钢,它的各种质量参数指标较高,因此对参与炼钢生产工艺的铁路运输也提出了很高的要求。为此,通过实际调研和计算,提出了铁路运输的方案。 相似文献
997.
998.
Collier-Baker Emma; Davis Joanne M.; Suddendorf Thomas 《Canadian Metallurgical Quarterly》2004,118(4):421
Domestic dogs (Canis familiaris) perform above chance on invisible displacement tasks despite showing few other signs of possessing the necessary representational abilities. Four experiments investigated how dogs find an object that has been hidden in 1 of 3 opaque boxes. Dogs passed the task under a variety of control conditions, but only if the device used to displace the object ended up adjacent to the target box after the displacement. These results suggest that the search behavior of dogs was guided by simple associative rules rather than mental representation of the object's past trajectory. In contrast, Experiment 5 found that on the same task, 18- and 24-month-old children showed no disparity between trials in which the displacement device was adjacent or nonadjacent to the target box. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
999.
People's conceptions of different types of moral exemplarity were examined in an attempt to augment the current emphasis on moral rationality with a fuller understanding of moral personality. In Study 1 (with 805 adults), a free-listing procedure was used to generate the attributes of 3 types of moral exemplars (just, brave, and caring). In Study 2 (with 401 undergraduates), prototypicality- and personality-rating procedures were used to generate a personality profile for each type of moral exemplar and to examine the relations among them. In Study 3 (with 240 undergraduates), a similarity-sorting procedure was used to identify the typologies implicit in people's understanding of these different types of moral exemplarity. The findings indicate that moral excellence can be exemplified in rather divergent ways and that understanding of moral functioning would be enhanced by attention to this wider range of moral virtues. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
1000.
Review declaring pleasant surprise with this relatively short book on stalking. It contains 164 pages of text, and provides a thorough context for understanding and treating stalking behavior, including a focus on both victim and perpetrator. The book is divided into five chapters. The first of these defines the nature of stalking behavior. Stalking is defined as harmful conduct, which involves unwanted communication and repeated unwanted intrusion by one individual upon another. The review notes that stalking behavior has three defining characteristics--(a) relentless and persistent contact, which is (b) unwanted and (c) adverse to the recipient. It is further observed that there is no single motive for stalking, nor any specific psychological profile for the personality of stalkers. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献