全文获取类型
收费全文 | 6469篇 |
免费 | 653篇 |
国内免费 | 341篇 |
专业分类
电工技术 | 520篇 |
综合类 | 359篇 |
化学工业 | 1108篇 |
金属工艺 | 370篇 |
机械仪表 | 366篇 |
建筑科学 | 356篇 |
矿业工程 | 178篇 |
能源动力 | 226篇 |
轻工业 | 516篇 |
水利工程 | 96篇 |
石油天然气 | 172篇 |
武器工业 | 73篇 |
无线电 | 753篇 |
一般工业技术 | 820篇 |
冶金工业 | 450篇 |
原子能技术 | 67篇 |
自动化技术 | 1033篇 |
出版年
2024年 | 59篇 |
2023年 | 137篇 |
2022年 | 267篇 |
2021年 | 387篇 |
2020年 | 256篇 |
2019年 | 182篇 |
2018年 | 232篇 |
2017年 | 254篇 |
2016年 | 222篇 |
2015年 | 281篇 |
2014年 | 343篇 |
2013年 | 456篇 |
2012年 | 439篇 |
2011年 | 425篇 |
2010年 | 417篇 |
2009年 | 354篇 |
2008年 | 352篇 |
2007年 | 342篇 |
2006年 | 256篇 |
2005年 | 254篇 |
2004年 | 162篇 |
2003年 | 137篇 |
2002年 | 134篇 |
2001年 | 112篇 |
2000年 | 107篇 |
1999年 | 61篇 |
1998年 | 78篇 |
1997年 | 67篇 |
1996年 | 60篇 |
1995年 | 54篇 |
1994年 | 43篇 |
1993年 | 54篇 |
1992年 | 35篇 |
1991年 | 47篇 |
1990年 | 44篇 |
1989年 | 47篇 |
1988年 | 32篇 |
1987年 | 24篇 |
1986年 | 24篇 |
1985年 | 30篇 |
1984年 | 17篇 |
1983年 | 25篇 |
1982年 | 18篇 |
1981年 | 18篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1976年 | 15篇 |
1975年 | 11篇 |
排序方式: 共有7463条查询结果,搜索用时 15 毫秒
1.
2.
3.
Zhao Hongliang Lu Tingting Liu Fengqin Yin Pan Wang Sen 《JOM Journal of the Minerals, Metals and Materials Society》2019,71(5):1643-1649
JOM - The Isa/Ausmelt smelting technology with a top submerged lance (TSL) has been extensively used in copper smelting processes. However, the TSL is extremely vulnerable to damage and failure... 相似文献
4.
5.
In this paper we report the results of electrical resistivity (1.5≤ T ≤ 300K) and point contact spectroscopy (PCS) measurements on single crystals of metallic sodium tungsten bronze with varying sodium content. We have shown that the electron-phonon coupling function as measured through PCS can explain quantitatively the large temperature dependence of resistivity ρ seen in these materials over the entire temperature range. The electron-phonon coupling function shows predominately large peaks for phonon frequency range of 30 meV ≤ ω ≤ 100 meV which match well with the calculated optical phonons for WO6 octahedron. The integrated electron-phonon coupling constant λ from this data is ≈ 0.25-0.45, depending on the Na content. PACS numbers: 72.15.-v, 72.80.Ga 相似文献
6.
2008年29届奥运会在北京举行,使得有关奥运的话题成为热门中的热门,与运动有关或无关的众多品牌、厂商对北京奥运年均寄予厚望,为赢取更大的收获和提升品牌知名度作最大的努力。其实早在几年前,国内外运动鞋品牌企业就已经大张旗鼓,在产品研发与广告宣传等多方面投入重金,为在这次北京奥运年带来的难得契机中处于市场制高点或明或隐地博杀着。 相似文献
7.
8.
Koji Kamei Kunihiko Fujita Eva Jettmar Sen Yoshida Kazuhiro Kuwabara 《Interacting with computers》2002,14(6):438-759
In this paper, we present and discuss Community Organizer, a system designed to support network communities. The main characteristic of Community Organizer is the use of spatial representations for the relationships among community members including the communications exchanged among these members. These spatial representations reflect the degree of closeness of interests and concerns among the members, and are intended to provide users with clues on how to form network communities. In order to investigate the effectiveness of the proposed spatial representations, we conducted experiments with two different versions of the software. One version offered meaningful spatial representations while the other version did not. The subjects who used the former software version felt a greater sense of ‘community’, enjoyed using the software more, and actively used it longer than the subjects using the latter software version (control condition). These results indicated that the proposed spatial representations are effective in supporting network community formation. 相似文献
9.
10.
Predictions of the discharge and the associated sediment concentration are very useful ingredients in any water resources reservoir design, planning, maintenance, and operation. Although there are many empirical relationships between the discharge and sediment concentration amounts, they need estimation of model parameters. Generally, parameter estimations are achieved through the regression method (RM), which has several restrictive assumptions. Such models are locally valid and their structures and parameter values are questionable from region to others. This paper proposes a new approach for sediment concentration prediction provided that there are measurements of discharge and sediment concentration. The basis of the methodology is a dynamic transitional model between successive time instances based on two variables, namely, discharge and sediment concentration measurements. The transition matrix elements are estimated from the measurements through a special form of the artificial neural networks as perceptrons. The sediment concentration predictions from discharge measurements are achieved through a perceptron Kalman filtering (PKF) technique. In the meantime, this technique also provides temporal predictions. A certain portion of the measurement sequence is employed for the model parameter estimations through training and the remaining part is used for the model verification. Detailed comparisons between RM and PKF approaches are presented and, finally, it is shown that the latter model works dynamically by simulating the observation scatter diagram in the best possible manner with smaller prediction errors. The application of the methodology is performed for the discharge and sediment concentration measurements obtained from the Mississippi River basin at St. Louis, Missouri. It is found that the PKF methodology has smaller average relative, root-mean-square, and absolute errors than RM. Furthermore, graphical representation, such as the scatter and frequency diagrams, indicated that the PKF approach has superiority over the RM. 相似文献