全文获取类型
收费全文 | 2459篇 |
免费 | 199篇 |
国内免费 | 108篇 |
专业分类
电工技术 | 53篇 |
综合类 | 140篇 |
化学工业 | 304篇 |
金属工艺 | 251篇 |
机械仪表 | 248篇 |
建筑科学 | 67篇 |
矿业工程 | 111篇 |
能源动力 | 45篇 |
轻工业 | 136篇 |
水利工程 | 9篇 |
石油天然气 | 38篇 |
武器工业 | 26篇 |
无线电 | 525篇 |
一般工业技术 | 168篇 |
冶金工业 | 37篇 |
原子能技术 | 10篇 |
自动化技术 | 598篇 |
出版年
2024年 | 8篇 |
2023年 | 22篇 |
2022年 | 48篇 |
2021年 | 58篇 |
2020年 | 57篇 |
2019年 | 37篇 |
2018年 | 45篇 |
2017年 | 84篇 |
2016年 | 90篇 |
2015年 | 94篇 |
2014年 | 162篇 |
2013年 | 144篇 |
2012年 | 177篇 |
2011年 | 228篇 |
2010年 | 124篇 |
2009年 | 131篇 |
2008年 | 155篇 |
2007年 | 185篇 |
2006年 | 191篇 |
2005年 | 119篇 |
2004年 | 100篇 |
2003年 | 85篇 |
2002年 | 61篇 |
2001年 | 46篇 |
2000年 | 44篇 |
1999年 | 48篇 |
1998年 | 35篇 |
1997年 | 27篇 |
1996年 | 24篇 |
1995年 | 22篇 |
1994年 | 27篇 |
1993年 | 20篇 |
1992年 | 12篇 |
1991年 | 14篇 |
1990年 | 13篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有2766条查询结果,搜索用时 15 毫秒
1.
To realize ultimately efficient signal processing, it is necessary to replace electrical signal processing circuits with optical ones. The optical micro-resonator, which localizes light at a certain spot, is an essential component in optical signal processing. Single-crystal calcium fluoride (CaF2) is the most suitable material for a highly efficient optical micro-resonator. The CaF2 resonator can only be manufactured by ultra-precision machining processes, because its crystal anisotropy does not allow the application of chemical etching. However, the optical micro-resonator's performance depends definitely on the surface integrity.This study investigated the relationship between surface quality after ultra-precision machining and crystal anisotropy. Firstly, crack initiation was investigated on the (1 0 0), (1 1 0), and (1 1 1) planes using the micro-Vickers hardness test. Secondly, brittle-ductile transition was investigated by orthogonal cutting tests. Finally, cutting performance of cylindrical turning was evaluated, which could be a suitable method for manufacturing the CaF2 resonator. The most difficult point in cylindrical turning of CaF2 is that the crystalline plane and cutting direction vary continuously. In order to manufacture the CaF2 optical micro-resonator more efficiently, analysis was conducted on crack initiation and surface quality of all crystallographic orientations from the perspective of slip system and cleavage. 相似文献
2.
Lean philosophy: implementation in a forging company 总被引:2,自引:2,他引:0
Ajit Kumar Sahoo N. K. Singh Ravi Shankar M. K. Tiwari 《The International Journal of Advanced Manufacturing Technology》2008,36(5-6):451-462
This research addresses the implementation of lean philosophy in a forging company with a focus on radial forging production
flow lines. Here, the prime motive is to evolve and test several strategies to eliminate waste on the shop floor. In this
research, a systematic approach is suggested for the implementation of lean principles. This paper describes an application
of value stream mapping (VSM). Consequently, the present and future states of value stream maps are constructed to improve
the production process by identifying waste and its sources. Furthermore, Taguchi’s method of design of experiments is pursued
here to minimize the forging defects produced due to imperfect operating conditions. A noticeable reduction in set-up time
and work-in-process (WIP) inventory level is substantiated. Finally, we conclude with a discussion of managerial implications
and the future scope of research. 相似文献
3.
制冷系统的节能优化运行 总被引:4,自引:0,他引:4
本文通过对制冷系统耗电诸多因素的初步分析 ,采用正交试验、回归计算等手段 ,得出系统耗电与主要因素的函数关系 ,以便通过优化计算迅速找出最佳运行参数 ,指导操作 ,从而达到节能是目的。 相似文献
4.
The current distribution and overall polarization behavior of electrodeposition at a flow-through (packed bed or fluidized bed) electrode are modeled by means of a one-dimensional model involving a primary reacting species and a simultaneous side reaction. The model equations are solved by orthogonal collocation; the time and storage requirements compare favorably to those of finite-difference methods. Experimental data obtained using a packed-bed electrode are compared with the model predictions and various methods of fitting the data are compared. 相似文献
5.
6.
舞钢扁钢锭咬边参数的确定 总被引:1,自引:0,他引:1
本文根据我公司自产的11.7t及13.34t扁钢锭在4200mm轧机生产过程中,运用正交试验方法,合理应用咬边参数的轧制方案,以此降低金属消耗。此方案使“咬入返回轧制”及“留尾轧制”新技术进一步得到完善,板形更加矩形,使锭一材成材率提高2%左右。 相似文献
7.
8.
本文提出了适于三种序号的Chrestenson函数序列的复制方法,对其复制过程进行了数学分析,并指出当Chrestenson函数退化为Walsh函数时,此方法即为复制理论中的平移复制方法。 相似文献
9.
Andrzej Lingas 《Information Processing Letters》2007,104(6):220-227
In 1986, Keil provided an O(n2) time algorithm for the problem of covering monotone orthogonal polygons with the minimum number of r-star-shaped orthogonal polygons. This was later improved to O(n) time and space by Gewali et al. in [L. Gewali, M. Keil, S.C. Ntafos, On covering orthogonal polygons with star-shaped polygons, Information Sciences 65 (1992) 45-63]. In this paper we simplify the latter algorithm—we show that with a little modification, the first step Sweep1 of the discussed algorithm—which computes the top ceilings of horizontal grid segments—can be omitted.In addition, for the minimum orthogonal guard problem in the considered class of polygons, our approach provides a linear time algorithm which uses O(k) additional space, where k is the size of the optimal solution—the algorithm in [L. Gewali, M. Keil, S.C. Ntafos, On covering orthogonal polygons with star-shaped polygons, Information Sciences 65 (1992) 45-63] uses both O(n) time and O(n) additional space. 相似文献
10.