全文获取类型
收费全文 | 30186篇 |
免费 | 1021篇 |
国内免费 | 278篇 |
专业分类
电工技术 | 481篇 |
综合类 | 33篇 |
化学工业 | 4759篇 |
金属工艺 | 1061篇 |
机械仪表 | 708篇 |
建筑科学 | 447篇 |
矿业工程 | 48篇 |
能源动力 | 1492篇 |
轻工业 | 1212篇 |
水利工程 | 166篇 |
石油天然气 | 100篇 |
武器工业 | 1篇 |
无线电 | 2777篇 |
一般工业技术 | 4684篇 |
冶金工业 | 1671篇 |
原子能技术 | 276篇 |
自动化技术 | 11569篇 |
出版年
2024年 | 77篇 |
2023年 | 427篇 |
2022年 | 998篇 |
2021年 | 1178篇 |
2020年 | 927篇 |
2019年 | 978篇 |
2018年 | 1253篇 |
2017年 | 996篇 |
2016年 | 965篇 |
2015年 | 628篇 |
2014年 | 1080篇 |
2013年 | 1768篇 |
2012年 | 1695篇 |
2011年 | 4180篇 |
2010年 | 2036篇 |
2009年 | 1875篇 |
2008年 | 1434篇 |
2007年 | 1191篇 |
2006年 | 943篇 |
2005年 | 955篇 |
2004年 | 822篇 |
2003年 | 830篇 |
2002年 | 494篇 |
2001年 | 199篇 |
2000年 | 192篇 |
1999年 | 211篇 |
1998年 | 422篇 |
1997年 | 287篇 |
1996年 | 263篇 |
1995年 | 199篇 |
1994年 | 180篇 |
1993年 | 169篇 |
1992年 | 127篇 |
1991年 | 158篇 |
1990年 | 125篇 |
1989年 | 113篇 |
1988年 | 103篇 |
1987年 | 109篇 |
1986年 | 101篇 |
1985年 | 102篇 |
1984年 | 110篇 |
1983年 | 93篇 |
1982年 | 74篇 |
1981年 | 81篇 |
1980年 | 56篇 |
1979年 | 46篇 |
1978年 | 39篇 |
1977年 | 36篇 |
1976年 | 45篇 |
1975年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
Decentralized adaptive coordinated control of multiple robot arms without using a force sensor 总被引:1,自引:0,他引:1
Haruhisa Kawasaki Author Vitae Satoshi Ueki Author Vitae Author Vitae 《Automatica》2006,42(3):481-488
This paper presents a distributed adaptive coordinated control method for multiple robot arms grasping a common object. The cases of rigid contact and rolling contact are analyzed. In the proposed controller, the dynamic parameters of both object and robot arms are estimated adaptively. The desired motions of the robot arms are generated by an estimated object reference model. The control method requires only the measurements of the positions and velocities of the object and robot arms, but not the measurements of forces and moments at contact points. The asymptotic convergence of trajectory is proven by the Lyapunov-like Lemma. Experiments involving two robot arms handling a common object are shown. 相似文献
93.
Effect of process parameters on impact strength of Al-7% Si alloy castings produced by VAEPC process 总被引:2,自引:2,他引:0
Sudhir Kumar Pradeep Kumar H. S. Shan 《The International Journal of Advanced Manufacturing Technology》2008,38(5-6):586-593
The castings produced by the evaporative pattern casting (EPC) process have blow holes. The blow holes in EPC castings are because of the non-escape of the gas produced as a result of burning of polystyrene pattern in the sand mold. To overcome the problem of blow holes, the EPC process is combined with the vacuum (V)- process. The vacuum applied to EPC mold draws the decomposed gases and improves the casting quality produced by the EPC process. The developed hybrid process has been termed as the vacuum assisted evaporative pattern casting (VAEPC) process. The objective of this paper to investigates the effect of process parameters, i.e, degree of vacuum, pouring temperature, grainfineness number, amplitude of vibration and time of vibration on the impact strength of Al-7% Si alloy castings in VAEPC process. In order to evaluate the effect of selected process parameters, the response surface methodology (RSM) is used to formulate a mathematical model which correlates the independent process parameters with the desired impact strength. The central composite rotatable design has been used to conduct the experiments. The results indicate that the impact strength decreases with increases in the grainfineness number and pouring temperature. Whereas, it has an inverse relationship with amplitude of vibration, time of vibration and degree of vacuum. The best value of impact strength (2.34 N/mm2) has been obtained at 400 mm Hg degree of vacuum imposed, 650°C as pouring temperature, 60 as sand grainfineness number, 460 μm as amplitude of vibration, and 70 s as time of vibration. 相似文献
94.
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
95.
The paper is devoted to the first order delayed linear system with relay output controlled by the proportional-integral (PI) regulator. The deterministic system exhibits stable oscillations, and, since the system itself is stable, it can be suitable to switch off the controller if there are no disturbances during a long time interval. In the present work, the random disturbances are modelled by a Poisson stream of impulses, and the goal is to determine the instants of switching on (off) of the PI controller. After several assumptions and quantization of the time axis, we construct the new optimal control problem which is successfully solved with the help of the dynamic programming approach. 相似文献
96.
The goal of face recognition is to distinguish persons via their facial images. Each person's images form a cluster, and a new image is recognized by assigning it to the correct cluster. Since the images are very high-dimensional, it is necessary to reduce their dimension. Linear discriminant analysis (LDA) has been shown to be effective at dimension reduction while preserving the cluster structure of the data. It is classically defined as an optimization problem involving covariance matrices that represent the scatter within and between clusters. The requirement that one of these matrices be nonsingular restricts its application to datasets in which the dimension of the data does not exceed the sample size. For face recognition, however, the dimension typically exceeds the number of images in the database, resulting in what is referred to as the small sample size problem. Recently, the applicability of LDA has been extended by using the generalized singular value decomposition (GSVD) to circumvent the nonsingularity requirement, thus making LDA directly applicable to face recognition data. Our experiments confirm that LDA/GSVD solves the small sample size problem very effectively as compared with other current methods. 相似文献
97.
98.
A stochastic realization problem of a stationary stochastic process is re-visited, and a new stochastically balanced realization algorithm is derived in a Hilbert space generated by second-order stationary processes. The present algorithm computes a stochastically balanced realization by means of the singular value decomposition of a weighted block Hankel matrix derived by a “block LQ decomposition”. Extension to a stochastic subspace identification method explains how the proposed abstract algorithm is implemented in system identification. 相似文献
99.
Reset controllers are linear controllers that reset some of their states to zero when their input is zero. We are interested in their feedback connection with linear plants, and in this paper we establish fundamental closed-loop properties including stability and asymptotic tracking. This paper considers more general reset structures than previously considered, allowing for higher-order controllers and partial-state resetting. It gives a testable necessary and sufficient condition for quadratic stability and links it to both uniform bounded-input bounded-state stability and steady-state performance. Unlike previous related research, which includes the study of impulsive differential equations, our stability results require no assumptions on the evolution of reset times. 相似文献
100.