全文获取类型
收费全文 | 387897篇 |
免费 | 4705篇 |
国内免费 | 1451篇 |
专业分类
电工技术 | 6620篇 |
综合类 | 2523篇 |
化学工业 | 54208篇 |
金属工艺 | 17789篇 |
机械仪表 | 15723篇 |
建筑科学 | 9769篇 |
矿业工程 | 1790篇 |
能源动力 | 8844篇 |
轻工业 | 32228篇 |
水利工程 | 4052篇 |
石油天然气 | 3681篇 |
武器工业 | 5篇 |
无线电 | 47320篇 |
一般工业技术 | 76752篇 |
冶金工业 | 53742篇 |
原子能技术 | 4642篇 |
自动化技术 | 54365篇 |
出版年
2021年 | 1802篇 |
2020年 | 1350篇 |
2019年 | 1672篇 |
2018年 | 22521篇 |
2017年 | 22236篇 |
2016年 | 15381篇 |
2015年 | 3163篇 |
2014年 | 3935篇 |
2013年 | 12167篇 |
2012年 | 11610篇 |
2011年 | 24979篇 |
2010年 | 21489篇 |
2009年 | 19374篇 |
2008年 | 20339篇 |
2007年 | 22915篇 |
2006年 | 8445篇 |
2005年 | 11948篇 |
2004年 | 9897篇 |
2003年 | 9463篇 |
2002年 | 7601篇 |
2001年 | 7163篇 |
2000年 | 6576篇 |
1999年 | 6881篇 |
1998年 | 16425篇 |
1997年 | 11394篇 |
1996年 | 8629篇 |
1995年 | 6560篇 |
1994年 | 5742篇 |
1993年 | 5597篇 |
1992年 | 4019篇 |
1991年 | 3818篇 |
1990年 | 3549篇 |
1989年 | 3369篇 |
1988年 | 3282篇 |
1987年 | 2591篇 |
1986年 | 2488篇 |
1985年 | 3160篇 |
1984年 | 2797篇 |
1983年 | 2561篇 |
1982年 | 2347篇 |
1981年 | 2390篇 |
1980年 | 2202篇 |
1979年 | 2049篇 |
1978年 | 1881篇 |
1977年 | 2177篇 |
1976年 | 2725篇 |
1975年 | 1585篇 |
1974年 | 1489篇 |
1973年 | 1558篇 |
1972年 | 1144篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Stability of the zero equilibrium state of a full electromagnetic suspension of a rotor under decentralized control of each bearing is proved. The obtained results may be used for selecting the structure of the system for control of electromagnetic bearings. 相似文献
992.
In the present study, oil palm wood flour (OPWF) particles with less than 250 μm sizes have been used as filler materials
in the woven-glass-fiber reinforced epoxy composite. The hybrid composites were fabricated using a hand lay-up method and
cured at room temperature under a compressive load of 196 N (20 kg). The OPWF of 2.5 to 10 parts per hundred (pph) by weight
was used to evaluate its effect on impact strength of the hybrid composites at a range of temperature from −50 to 50 °C. The
impact strength, evaluated using V-notch Charpy method, showed reduction with increasing filler content up to 5 pph and then
the strength increment in those composites containing more than 5 pph OPWF. More severe damages were found in specimens with
higher filler contents resulting higher energy absorption during impact. The composites with a large amount of OPWF particles
deflected crack propagation paths or created obstacles at the crack tips and increased toughness of the composites. The impact
strength was found to decrease when the samples fractured at subzero temperatures and this happened because of the reduction
of the matrix ductility at lower temperatures. 相似文献
993.
G. A. Shanshurov 《Russian Electrical Engineering》2007,78(9):467-473
A model of an induction motor with an asymmetric stator winding is developed; it may be represented as two phases connected in parallel or in series and displaced is space by some angle. 相似文献
994.
A. P. Petrova 《Polymer Science Series C》2007,49(3):219-219
Listed are the grades of heat-resistant adhesives developed under the Andrianov’s scientific guidance at the All-Russia Institute of Aviation Materials on the basis of organosilicon polymers. 相似文献
995.
On-body communications around the human torso are considered, using ultra-wideband transmissions. The velocity of the diffracted wave propagating around the body is extracted from frequency- domain spatial correlation analyses. 相似文献
996.
An adaptive alignment scheme for packaging two-dimensional (2D) arrays of optoelectronic systems interconnected by free-space optics is presented. A method of using three quadrant detectors to detect alignment errors in six degrees of freedom is described. However, the complexity of this system increases due to the interactions among the detected error signals. A novel control algorithm is presented to eliminate the interaction and simplify the design of the closed-loop feedback control. A computer simulation compares different algorithms and shows the effectiveness of the proposed algorithm. An experimental closed-loop feedback system demonstrated the principle of the error detection and correction of the proposed system with initial errors in multiple degrees of freedom 相似文献
997.
Narayanaswami C. Kamijoh N. Raghunath M. Inoue T. Cipolla T. Sanford J. Schlig E. Venkiteswaran S. Guniguntala D. Kulkarni V. Yamazaki K. 《Computer》2002,35(1):33-41
Nearly four years in development, the IBM Linux watch contains a complete computer system that runs Linux, displays X11 graphics, and has wireless connectivity. The system fits in a case that could pass as a slightly unusual analog timepiece with a somewhat odd shape and an extraordinarily brilliant face. The developers have created two versions of the watch, one with an organic light-emitting diode display and the other with a liquid crystal display. Still considered a research prototype, the watch already runs some personal information management applications, and it can communicate with PCs, PDAs, and other wireless-enabled devices, viewing condensed e-mail and directly receiving pager-like messages. Eventually, users will be able to access various Internet-based services, such as up-to-the-minute information about weather, traffic conditions, the stock market, and sports 相似文献
998.
Given a path of nonconstant curvature, local asymptotic stability can be proven for the general n trailer whenever the curvature can be considered as the output of an exogenous dynamical system. The controllers that provide convergence to zero of the tracking error chosen for the path-following problem are composed of a prefeedback that input-output linearizes the system, plus a linear controller. 相似文献
999.
Richardson C.H. Schafer R.W. 《IEEE transactions on pattern analysis and machine intelligence》1991,13(4):365-369
A theoretical lower bound on the number of points required in the decomposition of morphological structuring elements is described. It is shown that the decomposition of an arbitrary N -point structuring element will require at least [3 ln N /ln 3]points. Using this lower bound it is possible to find the optimal decompositions (in terms of the minimum number of unions or the minimum number of points) for all one-dimensional connected line segments. L -dimensional rectangles may be decomposed by optimally decomposing the L one-dimensional line segments that describe the rectangle 相似文献
1000.