全文获取类型
收费全文 | 33830篇 |
免费 | 3240篇 |
国内免费 | 2044篇 |
专业分类
电工技术 | 2655篇 |
综合类 | 3716篇 |
化学工业 | 3557篇 |
金属工艺 | 1666篇 |
机械仪表 | 2250篇 |
建筑科学 | 4373篇 |
矿业工程 | 2158篇 |
能源动力 | 1117篇 |
轻工业 | 1605篇 |
水利工程 | 2751篇 |
石油天然气 | 1791篇 |
武器工业 | 288篇 |
无线电 | 3052篇 |
一般工业技术 | 2227篇 |
冶金工业 | 1937篇 |
原子能技术 | 290篇 |
自动化技术 | 3681篇 |
出版年
2024年 | 112篇 |
2023年 | 357篇 |
2022年 | 672篇 |
2021年 | 735篇 |
2020年 | 809篇 |
2019年 | 744篇 |
2018年 | 670篇 |
2017年 | 934篇 |
2016年 | 1084篇 |
2015年 | 1266篇 |
2014年 | 2040篇 |
2013年 | 1755篇 |
2012年 | 2391篇 |
2011年 | 2631篇 |
2010年 | 1999篇 |
2009年 | 2171篇 |
2008年 | 1881篇 |
2007年 | 2425篇 |
2006年 | 2212篇 |
2005年 | 1987篇 |
2004年 | 1665篇 |
2003年 | 1505篇 |
2002年 | 1272篇 |
2001年 | 1125篇 |
2000年 | 890篇 |
1999年 | 752篇 |
1998年 | 578篇 |
1997年 | 489篇 |
1996年 | 413篇 |
1995年 | 366篇 |
1994年 | 285篇 |
1993年 | 191篇 |
1992年 | 154篇 |
1991年 | 111篇 |
1990年 | 88篇 |
1989年 | 80篇 |
1988年 | 56篇 |
1987年 | 69篇 |
1986年 | 23篇 |
1985年 | 14篇 |
1984年 | 31篇 |
1983年 | 17篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 15篇 |
1979年 | 8篇 |
1977年 | 4篇 |
1975年 | 3篇 |
1959年 | 2篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
介绍了为攀钢“501”滑动水口研制的专用液压驱动系统,对该系统的工作原理,性能特点,主要元件(设备)的选择原则等作了较为详细的说明介绍。 相似文献
22.
G. Dong 《Annals of Mathematics and Artificial Intelligence》1993,7(1-4):107-127
LDL is one of the recently proposed logical query languages, which incorporate set, for data and knowledge base systems. Since LDL programs can simulate negation, they are not monotonic in general. On the other hand, there are monotonic LDL programs. This paper addresses the natural question of “When are the generally nonmonotonic LDL programs monotonic?” and investigates related topics such as useful applications for monotonicity. We discuss four kinds of monotonicity, and examine two of them in depth. The first of the two, called “ω-monotonicity”, is shown to be undecidable even when limited to single-stratum programs. The second, called “uniform monotonicity”, is shown to implyω-monotonicity. We characterize the uniform monotonicity of a program (i) by a relationship between its Bancilhon-Khoshafian semantics and its LDL semantics, and (ii) with a useful property called subset completion independence. Characterization (ii) implies that uniformly monotonie programs can be evaluated more efficiently by discarding dominated facts. Finally, we provide some necessary and/or sufficient, syntactic conditions for uniform monotonicity. The conditions pinpoint (a) enumerated set terms, (b) negations of membership and inclusion, and (c) sharing of set terms as the main source for nonuniform monotonicity. 相似文献
23.
Eiichi Haginomori Kenji Yoshimura Shunichi Kobayashi Sadanori Kaneko Takeshi Yokota Masayuki Ishikawa 《Electrical Engineering in Japan》1994,114(4):50-61
To cope with the high rate of increase of power demand in the main industrialized districts in Japan, 550-kV transmission systems covering the districts have been reinforced, with most of the main power plants connected directly to these systems. Through 550-/300-kV substations, the majority of power to the districts is supplied by 300-kV systems. To limit the excess short-circuit capacity in the 300-kV systems, they tend to be reconstructed as so-called radial networks. In radial networks with high short-circuit capacity and relatively small number of transmission lines connected to the substation busbars, the rate of rise of TRV can be far higher than standard value. This paper analyzes the transient recovery voltages (TRV) in such extra-high-voltage radial networks in Japan, together with the relevant stresses to circuit-breakers during fault clearings. Future system conditions have also been introduced. As the typical rate of rise of the TRV values, more than twice that of today's standard ones are probable. 相似文献
24.
李青唐 《浙江工业大学学报》2005,(2)
岳飞《满江红》词在中国诗歌史上享誉千古,其豪迈壮烈的艺术张力和悲壮的魅力,震撼并感染了无数国人,铸就了一代代中华儿女的爱国情怀。作为爱国诗篇,其爱国情结与忠君理念相伴共生,今天我们对之作当代审视和解读,应突破狭隘的爱国范畴,将其升华为中华复兴的精神动力。 相似文献
26.
转炉负能炼钢攻关对策 总被引:1,自引:0,他引:1
通过介绍转炉炼钢工艺流程及工序能耗分析,为提高转炉煤气回收量及降低电耗采取了一系列攻关措施,实现了转炉负能炼钢,取得了一定经济效益。 相似文献
27.
Flooding phenomenon limits the stability and the flow of a liquid film falling along the walls of a channel in which a gas is flowing upwards.As known, the entrainment effect can completely prevent the liquid to fall from its natural flow. The present work proposes a new mechanistic model for the prediction of the onset of flooding in vertical and inclined pipes in the presence of obstructions, as well as taking into account the viscosity effect. The good performance of the model in the different geometrical conditions and for variable viscosities of the liquid component assesses the validity of the hypothesis that the instability of a wavelike disturbance limits the countercurrent flow in a channel. 相似文献
28.
赵惠琴 《有色冶金设计与研究》2004,25(4):4-8
根据所使用的低水泥浇注料的性能,对中铝山西分公司检修厂4号焙烧炉制定了合理的烘烤曲线,提高了耐火内衬的质量,延长了内衬的使用寿命。 相似文献
29.
Burns G. Leonard; Gomez Rapson; Walsh James A.; de Moura Marcela Alves 《Canadian Metallurgical Quarterly》2003,15(1):118
G. J. DuPaul (see record 2003-02033-012) offered two suggestions for additional research to understand the strong source effects reported by R. Gomez, G. L Burns, J. A. Walsh, and M. A. de Moura (see record 2003-02033-001) in attention-deficit/ hyperactivity disorder (ADHD) rating scales. The first suggestion was to determine whether the source effects represent mostly bias or accuracy. The second suggestion was to minimize source effects through the development of better ADHD rating scales. Because source effects can represent bias or accuracy, it is important to minimize the bias aspect through content validation procedures prior to attempts to determine whether source effects better reflect bias or accuracy. This comment offers various suggestions to reduce the bias in ADHD rating scales. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
30.