全文获取类型
收费全文 | 907篇 |
免费 | 17篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 41篇 |
化学工业 | 126篇 |
金属工艺 | 43篇 |
机械仪表 | 3篇 |
建筑科学 | 10篇 |
能源动力 | 26篇 |
轻工业 | 13篇 |
水利工程 | 3篇 |
石油天然气 | 2篇 |
无线电 | 232篇 |
一般工业技术 | 211篇 |
冶金工业 | 102篇 |
原子能技术 | 3篇 |
自动化技术 | 111篇 |
出版年
2022年 | 7篇 |
2021年 | 11篇 |
2020年 | 15篇 |
2019年 | 16篇 |
2018年 | 19篇 |
2017年 | 15篇 |
2016年 | 16篇 |
2015年 | 11篇 |
2014年 | 13篇 |
2013年 | 39篇 |
2012年 | 18篇 |
2011年 | 39篇 |
2010年 | 23篇 |
2009年 | 43篇 |
2008年 | 29篇 |
2007年 | 33篇 |
2006年 | 36篇 |
2005年 | 27篇 |
2004年 | 21篇 |
2003年 | 30篇 |
2002年 | 26篇 |
2001年 | 26篇 |
2000年 | 17篇 |
1999年 | 16篇 |
1998年 | 30篇 |
1997年 | 28篇 |
1996年 | 25篇 |
1995年 | 36篇 |
1994年 | 25篇 |
1993年 | 17篇 |
1992年 | 20篇 |
1991年 | 23篇 |
1990年 | 19篇 |
1989年 | 10篇 |
1988年 | 22篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 5篇 |
1983年 | 13篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1974年 | 6篇 |
1971年 | 4篇 |
1970年 | 4篇 |
排序方式: 共有926条查询结果,搜索用时 609 毫秒
11.
Tamal Bose M. -Q. Chen David A. Trautman 《Circuits, Systems, and Signal Processing》1994,13(5):601-614
A special class of complex biquad digital filters called orthogonal filters are investigated for stability under two's complement
quantization. A sufficient condition is derived for the asymptotic stability of the nonlinear filter. Bounds on the possible
limit cycles are also obtained. Using these bounds, any given filter can be tested for stability. The stability triangle is
then scanned using a dense grid, and each point on the grid is tested for stability/limit cycles. By this method, the stability
region given by the sufficient condition is extended. Regions within the linear stability triangle where various types of
limit cycles are possible are also identified. 相似文献
12.
13.
Two-dimensional (2-D) state-space digital filters are investigated for stability with and without quantization. A sufficient condition is obtained for the stability of the linear Fornasini-Marchesini (1976) state-space model. The same model is then studied for stability when implemented using two's complement truncation quantization, and a sufficient condition for asymptotic stability of the nonlinear filter is obtained. In the process, a theorem is proved which gives a sufficient condition for the stability of a one-dimensional (1-D) state-space digital filter under the same type of quantization 相似文献
14.
A polyhedron P is castable if its boundary can be partitioned by a plane into two polyhedral terrains. Castable polyhedra can be manufactured
easily using two cast parts, where each cast part can be removed from the object without breaking the cast part or the object.
If we assume that the cast parts are each removed by a single translation, it is shown that for a simple polyhedron with n vertices, castability can be decided in time and linear space using a simple algorithm. A more complicated algorithm solves the problem in time and space, for any fixed ε > 0. In the case where the cast parts are to be removed in opposite directions, a simple O(n
2
)-time algorithm is presented. Finally, if the object is a convex polyhedron and the cast parts are to be removed in opposite
directions, a simple algorithm is presented.
Received June 1, 1994; revised May 25, 1995. 相似文献
15.
J. R. Tarpani W. W. Bose Filho D. Spinelli 《Journal of Materials Engineering and Performance》2002,11(5):563-570
The elastic-plastic fracture toughness and crack extension behavior under the quasi-static loading regimen of several thermally
embrittled conditions of a nuclear reactor pressure vessel (RPV) steel were assessed on the basis of microstructural parameters.
It was discovered that the bainite packet size is the fracture properties controlling parameter of single-phase quenched and
tempered microstructures. Results were found in close agreement to those obtained in a parallel study with dual-phase annealed
microstructures derived from the same low alloy steel. Similarly, it was concluded that a Hall-Petch type relationship correlates
J-fracture mechanics criteria to the grain size. 相似文献
16.
E. Di Todaro C. T. O. F. Ruckert M. T. Milan W. W. Bose Filho J. R. Tarpani D. Spinelli 《Journal of Materials Engineering and Performance》2006,15(5):608-613
The main goal of this work was to evaluate the effectiveness of Walker’s equation in collapsing the fatigue crack propagation
data of a SAE AMS 7475-T7351 aluminum alloy loaded either longitudinally (L-T) or transversely (T-L) to the rolling direction.
T-L orientation testpieces presented lower ductility and fracture toughness values than L-T orientation. As a consequence,
during the fatigue crack propagation tests, T-L testpieces exhibited a stronger influence of monotonic modes of fracture,
resulting in higher Paris exponent values,m. Walker’s model was able to collapse fatigue crack propagation data of L-T test pieces at different applied stress ratios,R. However, for the T-L orientation, due to theR ratio dependency onm andC, simply averaging ofm values for the calculations of Walker’s exponent proved to be inefficient. A simple analytical procedure was proposed by
the authors to modify Walker’s model to take into account such effect. For T-L test pieces, when Walker’s model is modified
by considering both Paris’s exponent as well the coefficient as a function of theR ratio, the fatigue crack growth data collapses within a narrow band, thus allowing predictions to be made satisfactorily.
The collapsed band is even narrower if the empirical relationm=a+blogC is used instead of simple polynomial equations due to a better correlation coefficient. 相似文献
17.
Prosenjit Bose Paz Carmi Mirela Damian Robin Flatland Matthew J. Katz Anil Maheshwari 《Algorithmica》2014,69(2):397-409
For any angle α<2π, we show that any connected communication graph that is induced by a set P of n transceivers using omni-directional antennas of radius 1, can be replaced by a strongly connected communication graph, in which each transceiver in P is equipped with a directional antenna of angle α and radius r dir, for some constant r dir=r dir(α). Moreover, the new communication graph is a c-spanner of the original graph, for some constant c=c(α), with respect to number of hops. 相似文献
18.
Flexural properties, impact energy, heat deflection temperature, and resistance to thermal and hydrothermal degradation of composites based on E-glass and N-glass fibers as the reinforcing agents, and epoxy, unsaturated polyester, phenolic, and epoxy-phenolic resin systems as the matrix materials were studied and compared. As a reinforcing agent E-glass fiber is superior to N-glass fiber, particularly with respect to development of flexural strength and modulus, impact strength, and thermal resistance; N-glass fiber, however, imparts to the composites substantially higher resistance to hydrothermal degradation under boiling conditions in different chemical environments. For use of both E-glass and N-glass fibers as reinforcing agents, the general order of resistance to hydrothermal degradation for the composites based on different matrix resins is epoxy > phenolic > unsaturated polyester resin. Incorporation of a low dose of a rubbery polymer, such as styrene butadiene rubber (0.1–0.2%) and liquid polybutadiene (0.5–0.75%), in unsaturated polyester resin as the matrix resin measurably enhances impact energy of the composite. © 1995 John Wiley & Sons, Inc. 相似文献
19.
Weichang Xue Amit Bandyopadhyay Susmita Bose Chuanxian Ding K.M.C. Cheung 《Surface & coatings technology》2007,201(8):4685-4693
The use of strontium-containing hydroxyapatite (Sr-HA) as a biomaterial has been reported recently. In vitro and in vivo studies have shown that Sr-HA promotes osteoblast response and stimulates new bone formation. In order to extend its usage to major load-bearing applications, such as artificial hip replacement, it has been proposed that the material could be used in the form of a coating on implant surfaces. This paper reports a preliminary study of biocompatibility of plasma sprayed Sr-HA coatings on a metallic substrate. Coatings of Sr-HA containing 10 mol% Sr2+ was produced on titanium alloy substrates. The coating exhibited good bonding with the substrate. The bioactivity of Sr-HA coating was evaluated in vitro by immersion in simulated body fluid (SBF). After immersion in SBF, Sr-HA coating exhibited great ability to induce apatite precipitation on its surface. The possible effects of cell-materials interactions of Sr-HA coating were examined by culturing osteoprecursor cells (OPC1) on coating surfaces. The effect of Sr-HA was also compared to a hydroxyapatite (HA) coating, which is widely used in orthopedics and dentistry. The results indicated that Sr-HA coating had good biocompatibility with human osteoblasts. OPC1 cells survived and proliferated well on the surface of coating. Sr-HA coating promoted OPC1 cells attachment, and more local contacts were produced on the surface. The presence of Sr stimulated OPC1 cell differentiation and ALP expression. No deleterious effect on ECM formation and mineralization was found with Sr-HA coating. The results indicated that Sr-HA coating had good mechanical properties and bioactivity in vitro. 相似文献
20.
The effect of a higher-valent dopant like Sb on the iodination rate of lead under normal and short-circuit conditions in iodine pressure of 0.615–6.578 kPa and in the temperature range of 423–523 K has been investigated. Like pure Pb, Sb-doped Pb also follows the parabolic law of film growth. The isothermal parabolic rate constants are found to be enhanced due to the presence of Sb. The iodine-vapor-pressure dependence of the isothermal parabolic rate constant has been observed to be kppI
2
1/2
. This has been explained on the consideration of electron-hole migration across the film as the rate-limiting step. The activation energy for iodination of Sb-doped Pb under normal condition is estimated to be 64 kJ · mol–1 in an iodine pressure of 0.615 kPa. The rate of iodide-film growth has been found to increase considerably under a short-circuit mode of experiments. Such observations have been explained with the concept of ion migration as the rate-limiting step for the film-growth process. The iodine pressure dependence of rate constants under short-circuit conditions is observed to be kpI
2
1/3
, associated with an activation energy value of 51 kJ mol–1. The effect of putting additional resistances in series to the short-circuit Pt path during iodination of Sb-doped Pb is found to be similar to that observed for pure Pb. Results of the present study have been explained considering the prevalence of Schottky-Wagner type of point defects in the lead-iodide film. Wagner's electrochemical potential gradient has been confirmed to be the main driving force for the film-growth process. Iodide films have been characterized by SEM, EDS, EPMA, XRD, and AES analyses to substantiate the kinetics results. 相似文献