全文获取类型
收费全文 | 723篇 |
免费 | 1篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 1篇 |
综合类 | 26篇 |
化学工业 | 4篇 |
金属工艺 | 176篇 |
机械仪表 | 285篇 |
建筑科学 | 4篇 |
矿业工程 | 8篇 |
能源动力 | 2篇 |
轻工业 | 3篇 |
石油天然气 | 3篇 |
武器工业 | 5篇 |
无线电 | 11篇 |
一般工业技术 | 17篇 |
冶金工业 | 36篇 |
原子能技术 | 1篇 |
自动化技术 | 149篇 |
出版年
2023年 | 12篇 |
2022年 | 13篇 |
2021年 | 25篇 |
2020年 | 17篇 |
2019年 | 24篇 |
2018年 | 8篇 |
2017年 | 17篇 |
2016年 | 20篇 |
2015年 | 25篇 |
2014年 | 35篇 |
2013年 | 28篇 |
2012年 | 43篇 |
2011年 | 51篇 |
2010年 | 38篇 |
2009年 | 42篇 |
2008年 | 37篇 |
2007年 | 35篇 |
2006年 | 34篇 |
2005年 | 34篇 |
2004年 | 30篇 |
2003年 | 35篇 |
2002年 | 21篇 |
2001年 | 17篇 |
2000年 | 13篇 |
1999年 | 15篇 |
1998年 | 22篇 |
1997年 | 6篇 |
1996年 | 11篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 1篇 |
1992年 | 8篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
排序方式: 共有731条查询结果,搜索用时 31 毫秒
11.
《Ergonomics》2012,55(7):938-951
Awkward upper extremity postures and repetitive wrist motions have been identified by some studies as risk factors for upper extremity musculoskeletal disorders during keyboard work. However, accurate body postures and joint motions of typists typing on standardized workstations are not known. A laboratory study was conducted to continuously measure wrist and forearm postures and motions of 25 subjects while they typed for 10 – 15 min at a standard computer workstation adjusted to the subjects' anthropometry. Electrogoniometers continuously recorded wrist and forearm angles. Joint angular velocities and accelerations were calculated from the postural data. The results indicate that wrist and forearm postures during typing were sustained at non-neutral angles; mean wrist extension angle was 23.4 ± 10.9 degrees on the left and 19.9 ± 8.6 degrees on the right. Mean ulnar deviation was 14.7 ± 10.1 degrees on the left and 18.6 ± 5.8 degrees on the right. More than 73% of subjects typed with the left or right wrist in greater than 15 degrees extension and more than 20% typed with the left or right wrist in greater than 20 degrees ulnar deviation. Joint angles and motions while typing on an adjusted computer workstation were not predictable based on anthropometry or typing speed and varied widely between subjects. Wrist motions are rapid and are similar in magnitude to wrist motions of industrial workers performing jobs having a high risk for developing cumulative trauma disorders. The magnitude of the dynamic components suggests that wrist joint motions may need to be evaluated as a risk factor for musculoskeletal disorders during typing. 相似文献
12.
13.
Min-Ho Kyung Author Vitae Author Vitae 《Computer aided design》2003,35(10):901-911
This paper presents a nonlinear kinematic tolerance analysis algorithm for planar mechanical systems comprised of higher kinematic pairs. The part profiles consist of line and circle segments. Each part translates along a planar axis or rotates around an orthogonal axis. The part shapes and motion axes are parameterized by a vector of tolerance parameters with range limits. A system is analyzed in two steps. The first step constructs generalized configuration spaces, called contact zones, that bound the worst-case kinematic variation of the pairs over the tolerance parameter range. The zones specify the variation of the pairs at every contact configuration and reveal failure modes, such as jamming, due to changes in kinematic function. The second step bounds the worst-case system variation at selected configurations by composing the zones. Case studies show that the algorithm is effective, fast, and more accurate than a prior algorithm that constructs and composes linear approximations of contact zones. 相似文献
14.
We discuss the following problem which arises in robot motion planning, NC machining and computer animation: Given are a fixed surface Ψ and N positions Φi of a moving surface Φ such that the Φi are in point contact with Ψ. Compute a smooth and fair Euclidean gliding motion Φ(t) of the surface Φ on the surface Ψ which interpolates (or approximates) the given positions Φi at time instances ti. First we generalize interpolatory variational subdivision algorithms for curves to curves on surfaces. Second we study an unconstraint motion design algorithm which we then extend to the main contribution of this paper, an algorithm for the design of a motion constraint by a contacting surface pair. Both motion design algorithms use a feature point representation of the moving surface, subdivision algorithms for curves, instantaneous kinematics, and ideas from line geometry. Geometric methods are used for the numerical solution of the arising optimization problems. 相似文献
15.
在凸轮的制造过程中,如果只知道凸轮的运动规律只是一些离散的点时,而要对凸轮进行理论分析和加工,可以从实现从动件工作过程的特殊位置点的要求出发,采用分段三次样条插值函数来确定凸轮的曲线方程,应用曲线方程对凸轮进行设计、制造,并对凸轮进行动力学和运动学分析。 相似文献
16.
用指数积公式法表示开链机器人的运动学方程,将吴消元法引入运动学逆问题的求解。通过吴消元法的特征列思想和符号运算的结合,实现了开链机器人运动学逆解的解析计算。结合实例说明了吴消元法在开链机器人运动学逆问题求解中的有效性。 相似文献
17.
本文以八杆压力机传动机构为研究对象,通过分析八杆机构的几何模型,研究各参数间的数学关系表达式,建立各关键点的坐标表达式即可观察任意时刻各个点及杆件的位置变化,从而实现机构的运动仿真,提高了设计效率。 相似文献
18.
Jaime Gallardo-Alvarado 《Robotics and Computer》2012,28(2):220-226
In this work the jerk analysis of a 3-RRPS parallel manipulator to realize six degrees of freedom is approached by means of the theory of screws. The input/output equations of velocity, acceleration and jerk of the moving platform with respect to the fixed platform are obtained systematically by resorting to reciprocal-screw theory. A numerical example is included in order to show the application of the method of kinematic analysis. Furthermore, the numerical results obtained via screw theory are satisfactorily compared with simulations generated with the aid of commercially available software. 相似文献
19.
20.
《Ergonomics》2012,55(9):1430-1445
Ergonomists need easy-to-use, quantitative job evaluation methods to assess risk factors for upper extremity work-related musculoskeletal disorders in field-based epidemiology studies. One device that may provide an objective measure of exposure to arm acceleration is a wrist-worn accelerometer or activity monitor. A field trial was conducted to evaluate the performance of a single-axis accelerometer using an industrial population (n= 158) known to have diverse upper limb motion characteristics. The second phase of the field trial involved an examination of the relationship between more traditional observation-based ergonomic exposure measures and the monitor output among a group of assembly-line production employees (n= 48) performing work tasks with highly stereotypic upper limb motion patterns. As expected, the linear acceleration data obtained from the activity monitor showed statistically significant differences between three occupational groups known observationally to have different upper limb motion requirements. Among the assembly-line production employees who performed different short-cycle assembly work tasks, statistically significant differences were also observed. Several observation-based ergonomic exposure measures were found to explain differences in the acceleration measure among the production employees who performed different jobs: hand and arm motion speed, use of the hand as a hammer, and, negatively, resisting forearm rotation from the torque of a power tool. The activity monitors were found to be easy to use and non-intrusive, and to be able to distinguish arm acceleration among groups with diverse upper limb motion characteristics as well as between different assembly job tasks where arm monitors were performed repeatedly at a fixed rate. 相似文献