全文获取类型
收费全文 | 3001篇 |
免费 | 365篇 |
国内免费 | 178篇 |
专业分类
电工技术 | 226篇 |
综合类 | 313篇 |
化学工业 | 256篇 |
金属工艺 | 200篇 |
机械仪表 | 178篇 |
建筑科学 | 306篇 |
矿业工程 | 112篇 |
能源动力 | 102篇 |
轻工业 | 546篇 |
水利工程 | 145篇 |
石油天然气 | 69篇 |
武器工业 | 37篇 |
无线电 | 158篇 |
一般工业技术 | 285篇 |
冶金工业 | 233篇 |
原子能技术 | 28篇 |
自动化技术 | 350篇 |
出版年
2024年 | 26篇 |
2023年 | 56篇 |
2022年 | 97篇 |
2021年 | 117篇 |
2020年 | 127篇 |
2019年 | 127篇 |
2018年 | 103篇 |
2017年 | 100篇 |
2016年 | 133篇 |
2015年 | 142篇 |
2014年 | 181篇 |
2013年 | 190篇 |
2012年 | 216篇 |
2011年 | 216篇 |
2010年 | 167篇 |
2009年 | 166篇 |
2008年 | 160篇 |
2007年 | 215篇 |
2006年 | 162篇 |
2005年 | 142篇 |
2004年 | 129篇 |
2003年 | 86篇 |
2002年 | 65篇 |
2001年 | 51篇 |
2000年 | 72篇 |
1999年 | 32篇 |
1998年 | 22篇 |
1997年 | 18篇 |
1996年 | 18篇 |
1995年 | 27篇 |
1994年 | 14篇 |
1993年 | 13篇 |
1992年 | 15篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1984年 | 8篇 |
1982年 | 6篇 |
1978年 | 5篇 |
1967年 | 5篇 |
1966年 | 4篇 |
1965年 | 7篇 |
1964年 | 5篇 |
1963年 | 4篇 |
1962年 | 5篇 |
1961年 | 5篇 |
1960年 | 6篇 |
1957年 | 5篇 |
排序方式: 共有3544条查询结果,搜索用时 15 毫秒
201.
202.
203.
Study of magnetite film formation at metal-scale interface during cooling of steel products 总被引:2,自引:0,他引:2
A thin layer of magnetite is sometimes observed in the scales of hot-rolled sheets and wire rod at the scale-metal interface. The results of this study show that this layer of magnetite is produced, during the cooling of the products, by the wustite decomposition. The time/temperature field in which it appears has been defined. This inner layer is composed of pure magnetite, in epitaxy with the neighboring wustite, and the metal surface is not essential to its nucleation. The proeutectod reaction which, during cooling, produces an increase in the oxygen concentration of the wustite in contact with the metal favors the subsequent growth of the magnetite layer.This work was conducted with the technical collaboration of M. Malleret. 相似文献
204.
Intercorrelations between 19 response set scales, based upon the scores of 110 students, were factor analyzed and the factors rotated orthogonally. Edwards' SD scale and 6 experimental social desirability scales had their highest loadings on the 1st factor. 3 scales containing neutral items in which the probability of a True response to the items varied between scales were found to have their highest loadings on 3 different factors. Scales designed to measure the tendency to give deviant True responses to items with socially undesirable scale values, to items with socially desirable scale values, and to items with neural scale values were found to have their highest loadings on 3 different factors. The tendency to give deviant True responses to items with socially undesirable scale values was found to be related to the tendency to give deviant False responses to items with socially desirable scale values. The tendency to mark items as doubtful and the tendency to answer items marked doubtful as True were identified as 2 factors unrelated to social desirability tendencies. (31 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
205.
Reinforcement learning on explicitly specified time scales 总被引:1,自引:0,他引:1
In recent years hierarchical concepts of temporal abstraction have been integrated in the reinforcement learning framework to improve scalability. However, existing approaches are limited to domains where a decomposition into subtasks is known a priori. In this article we propose the concept of explicitly selecting time scale related abstract actions if no subgoal related abstract actions are available. This concept is realised with multi-step actions on different time scales that are combined in one single action set. We exploit the special structure of the action set in the MSA-Q-learning algorithm. This approach is suited for learning optimal policies in unstructured domains where a decomposition into subtasks is not known in advance or does not exist at all. By learning different explicitly specified time scales simultaneously, we achieve a considerable improvement of learning speed, which we demonstrate on several benchmark problems. 相似文献
206.
207.
FAT和NTFS文件系统的特点与应用 总被引:1,自引:0,他引:1
王洪彪 《数字社区&智能家居》2007,1(6):1563
对Windows 98操作系统可以同时支持FATl6、FAT32两种文件系统和Windows 2000/XP操作系统则支持FATl6、FAT32、NTFS三种文件系统进行了研究,探讨了几个问题1.什么是文件系统;2.基本文件系统(FAT16);3.NTFS文件系统;4.增强的文件系统(FAT32);5.DOS下访问NTFS分区的数据方法。 相似文献
208.
Sellbom Martin; Ben-Porath Yossef S.; Stafford Kathleen P. 《Canadian Metallurgical Quarterly》2007,19(4):430
We examined the convergent and discriminant validity of the Minnesota Multiphasic Personality Inventory--2 (MMPI--2) measures of psychopathy, including the Clinical Scale 4, Restructured Clinical Scale 4 (RC4), Content Scale Antisocial Practices (ASP), and Personality Psychopathology Five Scale Disconstraint (DISC). Comparisons of the empirical correlates of these scales were conducted with 2 samples of participants evaluated at a criminal court clinic. The 2 samples included 59 men and 19 women and 913 men and 327 women, respectively. Two types of criteria (clinician ratings and archival record review) were utilized in the analyses. Relative to Clinical Scale 4, RC4 had significantly greater convergent validity in predicting psychopathy as measured by the Psychopathy Checklist--Screening Version (S. D. Hart, D. N. Cox, & R. D. Hare, 1995) and behavioral criteria associated with this construct. RC4 also showed substantially improved discriminant validity when compared with its Clinical Scale counterpart. Among all the MMPI-2 scales studied, RC4 was the best measure of the social deviance traits of psychopathy. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
209.
Gray Nicola S.; Fitzgerald Suzanne; Taylor John; MacCulloch Malcolm J.; Snowden Robert J. 《Canadian Metallurgical Quarterly》2007,19(4):474
Accurate predictions of future reconviction, including those for violent crimes, have been shown to be greatly aided by the use of formal risk assessment instruments. However, it is unclear as to whether these instruments would also be predictive in a sample of offenders with intellectual disabilities. In this study, the authors have shown that the Violence Risk Appraisal Guide (V. L. Quinsey, G. T. Harris, M. E. Rice, & C. Cormier, 1998); the Psychopathy Checklist--Screening Version (S. D. Hart, D. N. Cox, & R. D. Hare, 1995); and the History, Clinical, Risk Management--20 (C. D. Webster, K. S. Douglas, D. Eaves, & S. D. Hart, 1997) were all significant predictors of violent and general reconviction in this sample, and in many cases, their efficacy was greater than in a control sample of mentally disordered offenders without an intellectual disability. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
210.
研究机械力作用下金属/陶瓷功能梯度薄板3次超谐共振问题.按照功能梯度薄板的非线性动力学方程,得到金属/陶瓷功能梯度薄板受横向机械力作用的非线性振动方程。应用非线性振动的多尺度法得到系统3次超谐共振近似解并进行数值计算。分析阻尼、激励、几何尺寸等参数对系统3次超谐共振幅频响应曲线的影响. 相似文献