全文获取类型
收费全文 | 243740篇 |
免费 | 2670篇 |
国内免费 | 439篇 |
专业分类
电工技术 | 4333篇 |
综合类 | 259篇 |
化学工业 | 39858篇 |
金属工艺 | 9525篇 |
机械仪表 | 7460篇 |
建筑科学 | 5593篇 |
矿业工程 | 1398篇 |
能源动力 | 5236篇 |
轻工业 | 24999篇 |
水利工程 | 2500篇 |
石油天然气 | 5145篇 |
武器工业 | 33篇 |
无线电 | 25230篇 |
一般工业技术 | 45380篇 |
冶金工业 | 45541篇 |
原子能技术 | 6022篇 |
自动化技术 | 18337篇 |
出版年
2021年 | 2138篇 |
2019年 | 2037篇 |
2018年 | 3544篇 |
2017年 | 3466篇 |
2016年 | 3737篇 |
2015年 | 2275篇 |
2014年 | 3935篇 |
2013年 | 10285篇 |
2012年 | 6233篇 |
2011年 | 8436篇 |
2010年 | 6660篇 |
2009年 | 7347篇 |
2008年 | 7669篇 |
2007年 | 7809篇 |
2006年 | 6988篇 |
2005年 | 6104篇 |
2004年 | 5876篇 |
2003年 | 5674篇 |
2002年 | 5748篇 |
2001年 | 5645篇 |
2000年 | 5436篇 |
1999年 | 5345篇 |
1998年 | 12655篇 |
1997年 | 8982篇 |
1996年 | 6908篇 |
1995年 | 5369篇 |
1994年 | 4779篇 |
1993年 | 4677篇 |
1992年 | 3700篇 |
1991年 | 3422篇 |
1990年 | 3621篇 |
1989年 | 3507篇 |
1988年 | 3332篇 |
1987年 | 2930篇 |
1986年 | 2970篇 |
1985年 | 3398篇 |
1984年 | 3248篇 |
1983年 | 2904篇 |
1982年 | 2755篇 |
1981年 | 2845篇 |
1980年 | 2735篇 |
1979年 | 2638篇 |
1978年 | 2698篇 |
1977年 | 2966篇 |
1976年 | 3836篇 |
1975年 | 2384篇 |
1974年 | 2260篇 |
1973年 | 2393篇 |
1972年 | 1981篇 |
1971年 | 1870篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
231.
O. E. Aleksandrov 《Atomic Energy》2004,96(3):196-201
The theory of separation, based on radial averaging, in a Zippe centrifuge is developed. Certain aspects of the theory of the rotational potential and the errors in understanding the essence of the Helmholtz decomposition as it applies to a gas centrifuge are elucidated. It is shown that the Helmholtz decomposition method does not have cetain drawbacks of the classical theory of the radial averaging method and makes it possible to take account of the rotational flows due to the feed, find expicitly the transit flow distribution, take account of the radial nonuniformity, and take account of the radial convective transport of an isotope by the circulation and transit flows, and the method is not limited by the assumption that the feed flow is small. 相似文献
232.
Age assessment and control of the reliability of the coolant flow-rate measurement system of the RBMK-1500 reactor at the Ignalina nuclear power plant are examined. A statistical analysis is made of the data obtained from measurements of the techanical characteristics of SHADR-32M flow meters. A mathematical model of the aging of flow meters and reliability estimates is constructed. A strategy is developed for replacing SHADR; this strategy makes it possible to support the required relaibility of the entire coolant flow-rate measurement system. 相似文献
233.
Yanqing Ji Hao Ying John Yen Shizhuo Zhu Daniel C. Barth‐Jones Richard E. Miller R. Michael Massanari 《国际智能系统杂志》2007,22(8):827-845
Discovering unknown adverse drug reactions (ADRs) in postmarketing surveillance as early as possible is highly desirable. Nevertheless, current postmarketing surveillance methods largely rely on spontaneous reports that suffer from serious underreporting, latency, and inconsistent reporting. Thus these methods are not ideal for rapidly identifying rare ADRs. The multiagent systems paradigm is an emerging and effective approach to tackling distributed problems, especially when data sources and knowledge are geographically located in different places and coordination and collaboration are necessary for decision making. In this article, we propose an active, multiagent framework for early detection of ADRs by utilizing electronic patient data distributed across many different sources and locations. In this framework, intelligent agents assist a team of experts based on the well‐known human decision‐making model called Recognition‐Primed Decision (RPD). We generalize the RPD model to a fuzzy RPD model and utilize fuzzy logic technology to not only represent, interpret, and compute imprecise and subjective cues that are commonly encountered in the ADR problem but also to retrieve prior experiences by evaluating the extent of matching between the current situation and a past experience. We describe our preliminary multiagent system design and illustrate its potential benefits for assisting expert teams in early detection of previously unknown ADRs. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 827–845, 2007. 相似文献
234.
In this paper we show that by the analysis of 2D images collected with a laboratory X-ray microdiffractometer it is possible to non-destructively evaluate the structure, the microstructure, and the preferred orientation of films. In particular, the structural analysis of Co/Au multilayers on Si(1 0 0) deposited at different Ar pressures are reported and discussed. 相似文献
235.
Doratha E Drake 《Information Processing Letters》2003,85(4):211-213
We present a linear time approximation algorithm with a performance ratio of 1/2 for finding a maximum weight matching in an arbitrary graph. Such a result is already known and is due to Preis [STACS'99, Lecture Notes in Comput. Sci., Vol. 1563, 1999, pp. 259-269]. Our algorithm uses a new approach which is much simpler than the one given by Preis and needs no amortized analysis for its running time. 相似文献
236.
237.
The fabrication process of a low-temperature poly-Si thin-film transistor (TFT) with a storage capacitor was studied. The atmospheric-pressure chemical-vapour deposited SiO2 protected the buried indium tin oxide (ITO) from reduction by a pure H2 plasma treatment that was essential for the effective improvement of the poly-Si TFT characteristics. Thus, a storage capacitor with an ITO (picture electrode)-SiO2-ITO (buried common electrode) structure was successfully fabricated. The poly-Si TFT with a channel width/length W/L ratio of 5 drove a 3 pF storage capacitor in 2 μs, and it showed superior driverability for LCD use. The TFT also had good hold characteristics under illumination for the realization of grey-scale representation. 相似文献
238.
John E. Sohn 《The Journal of Adhesion》1985,19(1):15-27
Enhanced matrix-filler adhesion is realized after filler treatment with a surface treatment process. The hydrosol/coupling agent treatment was applied to a wide range of inorganic and organic fillers, and adhesion to a variety of matrix resins was improved. Scanning Electron Microscopy (SEM) was used to determine the locus of failure in the filled systems. The locus of failure shows the relative degree of adhesion between the filler and the polymer matrix. Significant improvement in adhesion in humid environments is also observed. 相似文献
239.
Industrial production of Si3 N4 from SiCI4 , is increasing. An element rivaling CI in abundance and cheapness with potentially suitable chemistry for this application is sulfur. Thus, Si–S–N chemistry was investigated to determine its usefulness in producing Si3 N4 . Bifunctionality in S, as opposed to mono-functionality in CI, may allow special routes via polymers to become important. 相似文献
240.
Enthalpies of segregation for isovalent impurities in magnesium and calcium oxide as a function of surface concentration were calculated by using an atomistic computer simulation method. We have considered Be2+ , Mg2+ , Ca2+ , Ba2+ , and Ni2+ , segregating to both (001) and (110) faces. The results obtained can be extrapolated to predict the behavior of other impurities including Mn2+ , Fe2+ , and Co2+ , We find, for example, that Fe2+ , Mn2+ , Ca2+ , Sr2+ , and Ba2+ will concentrate at the (001) surface of MgO, while Ni2+ will be depleted. The enthalpy of segregation is found to vary substantially with coverage particularly for the larger impurities. The enthalpy becomes less negative with increasing impurity concentration due to the increasing lattice strain until the surface is nearly saturated. Then additional stabilization is obtained by restructuring of the surface layer. We predict reconstructed surfaces for both the (001) and (110) faces, which contain a high concentration of a larger impurity ion. The enthalpy of segregation shows a maximum at around 50% surface coverage implying a bimodal surface distribution of segregant. The influence of segregation on surface energy suggests two unusual effects. The (001) surface energy of the impure crystal becomes negative for surface concentrations of impurity greater than 10% Ba2+ or 75% Sr2+ in MgO. This implies a thermodynamic barrier to sintering. At high coverages of Ba2+ in MgO the (110) surface becomes more stable than the (001) face suggesting that facetting may occur. 相似文献