全文获取类型
收费全文 | 15339篇 |
免费 | 936篇 |
国内免费 | 28篇 |
专业分类
电工技术 | 167篇 |
综合类 | 43篇 |
化学工业 | 3244篇 |
金属工艺 | 307篇 |
机械仪表 | 315篇 |
建筑科学 | 690篇 |
矿业工程 | 45篇 |
能源动力 | 506篇 |
轻工业 | 1230篇 |
水利工程 | 123篇 |
石油天然气 | 51篇 |
无线电 | 1128篇 |
一般工业技术 | 2962篇 |
冶金工业 | 2244篇 |
原子能技术 | 117篇 |
自动化技术 | 3131篇 |
出版年
2023年 | 145篇 |
2022年 | 287篇 |
2021年 | 570篇 |
2020年 | 374篇 |
2019年 | 380篇 |
2018年 | 497篇 |
2017年 | 462篇 |
2016年 | 531篇 |
2015年 | 467篇 |
2014年 | 595篇 |
2013年 | 1062篇 |
2012年 | 975篇 |
2011年 | 1157篇 |
2010年 | 806篇 |
2009年 | 749篇 |
2008年 | 791篇 |
2007年 | 776篇 |
2006年 | 581篇 |
2005年 | 505篇 |
2004年 | 372篇 |
2003年 | 383篇 |
2002年 | 339篇 |
2001年 | 214篇 |
2000年 | 187篇 |
1999年 | 208篇 |
1998年 | 214篇 |
1997年 | 188篇 |
1996年 | 185篇 |
1995年 | 178篇 |
1994年 | 153篇 |
1993年 | 149篇 |
1992年 | 120篇 |
1991年 | 74篇 |
1990年 | 122篇 |
1989年 | 116篇 |
1988年 | 80篇 |
1987年 | 94篇 |
1986年 | 100篇 |
1985年 | 100篇 |
1984年 | 88篇 |
1983年 | 76篇 |
1982年 | 96篇 |
1981年 | 90篇 |
1980年 | 71篇 |
1979年 | 70篇 |
1978年 | 62篇 |
1977年 | 74篇 |
1976年 | 61篇 |
1975年 | 45篇 |
1974年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 734 毫秒
941.
942.
Shichao Ding Paul A. MeehanWilliam J.T. Daniel 《Journal of Materials Processing Technology》2011,211(3):376-381
Millipede forming, a novel sheet metal forming method, has been proposed and developed recently to overcome fundamental limitations in conventional roll forming. For this new method, there are two main aspects: use of an optimal transitional surface and implementation of a method to feed the strip through the transition surface. Achieving the optimal transitional surface involves defining the change of surface shape between a flat strip and a final shaped product conceptualised to the strip's mid-surface, regardless of the strip's thickness.In this paper, one method of implementing a transition surface, Millipede forming, is introduced. A prototype has been built to demonstrate the working principle and can be used to produce some simple profiles, within a short forming length of 200 mm. 相似文献
943.
This study aimed to investigate the rheology of two-mineral mixture systems as a function of pH and solid concentration. Single minerals (nickel oxide, quartz and hematite) and two-mineral systems (nickel oxide–quartz and nickel oxide–hematite) were studied. Rheology tests were conducted to investigate the effect of pH and solid concentration on shear yield stress of suspensions while zeta potential measurements of suspensions were used to explain the rheology results. Rheology results indicated that single mineral experiments showed that 5 and 10 vol.% of quartz and hematite had no shear yield stress whereas the one of nickel oxide was positive value. Shear yield stress of nickel oxide–quartz mixture and nickel oxide–hematite mixtures increased as increasing pH and solid concentration, and the value was higher than the one obtained with only nickel oxide. These results obtained with two-mineral mixture systems were explained by electrokinetic properties of the minerals, i.e. zeta potential of the minerals. 相似文献
944.
945.
946.
António J.R. Neves Armando J. Pinho Daniel A. Martins Bernardo Cunha 《Mechatronics》2011,21(2):399-410
Robotic soccer is nowadays a popular research domain in the area of multi-robot systems. In the context of RoboCup, the Middle Size League is one of the most challenging. This paper presents an efficient omnidirectional vision system for real-time object detection, developed for the robotic soccer team of the University of Aveiro, CAMBADA. The vision system is used to find the ball and white lines, which are used for self-localization, as well as to find the presence of obstacles. Algorithms for detecting these objects and also for calibrating most of the parameters of the vision system are presented in this paper. We also propose an efficient approach for detecting arbitrary FIFA balls, which is an important topic of research in the Middle Size League. The experimental results that we present show the effectiveness of our algorithms, both in terms of accuracy and processing time, as well as the results that the team has been achieving: 1st place in RoboCup 2008, 3rd place in 2009 and 1st place in the mandatory technical challenge in RoboCup 2009, where the robots have to play with an arbitrary standard FIFA ball. 相似文献
947.
Filipe Valente Alberto Vale Daniel Fonte Isabel Ribeiro 《Fusion Engineering and Design》2011,86(9-11):1967-1970
The transfer cask system (TCS) is one of the remote handling systems that will operate in ITER, transporting heavy and highly activated in-vessel components between the tokamak building and the hot cell building. A motion planning methodology for the TCS was developed, providing smooth paths that maximize the clearance to obstacles and that incorporate manoeuvres whenever necessary. This paper presents the results of the TCS planning algorithm with trajectories computed for nominal operations. The length of the journey, the velocity, the time duration, and the risk of collision were evaluated individually for each trajectory. A summary of all results, conclusions and future work are presented and discussed. 相似文献
948.
Demany Laurent; Semal Catherine; Pressnitzer Daniel 《Canadian Metallurgical Quarterly》2011,37(2):597
Listeners had to compare, with respect to pitch (frequency), a pure tone (T) to a combination of pure tones presented subsequently (C). The elements of C were either synchronous, and therefore difficult to hear out individually, or asynchronous and therefore easier to hear out individually. In the “present/absent” condition, listeners had to judge if T reappeared in C or not. In the “up/down” condition, the task was to judge if the element of C most similar to T was higher or lower than T. When the elements of C were synchronous, the up/down task was found to be easier than the present/absent task; the converse result was obtained when the elements of C were asynchronous. This provides evidence for a duality of auditory comparisons between tone frequencies: (1) implicit comparisons made by automatic and direction-sensitive “frequency-shift detectors”; (2) explicit comparisons more sensitive to the magnitude of a frequency change than to its direction. Another experiment suggests that although the frequency-shift detectors cannot compare effectively two tones separated by an interfering tone, they are largely insensitive to interfering noise bursts. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
949.
950.
Cultivation theory suggests that society holds very different body standards for men versus women, and research indicates that the consequences of defying these social norms may not be linear. To test these notions in the employment context, we examined the relationship between weight and income and the degree to which the relationship varies by gender. For women, we theorized a negative weight–income relationship that is steepest at the thin end of the distribution. For men, we predicted a positive weight–income relationship until obesity, where it becomes negative. To test these hypotheses, we utilized 2 longitudinal studies, 1 German and 1 American. In Study 1, weight was measured over 2 time periods, and earnings were averaged over the subsequent 5 years. Study 2 was a multilevel study in which weight and earnings were within-individual variables observed over time, and gender was a between-individual variable. Results from the 2 studies generally support the hypotheses, even when examining within-individual changes in weight over time. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献