全文获取类型
收费全文 | 70403篇 |
免费 | 10838篇 |
国内免费 | 8649篇 |
专业分类
电工技术 | 8226篇 |
技术理论 | 2篇 |
综合类 | 8666篇 |
化学工业 | 10098篇 |
金属工艺 | 2627篇 |
机械仪表 | 5777篇 |
建筑科学 | 5852篇 |
矿业工程 | 2106篇 |
能源动力 | 1829篇 |
轻工业 | 1453篇 |
水利工程 | 1973篇 |
石油天然气 | 1807篇 |
武器工业 | 2515篇 |
无线电 | 8032篇 |
一般工业技术 | 7343篇 |
冶金工业 | 1565篇 |
原子能技术 | 366篇 |
自动化技术 | 19653篇 |
出版年
2024年 | 517篇 |
2023年 | 1427篇 |
2022年 | 2199篇 |
2021年 | 2434篇 |
2020年 | 2780篇 |
2019年 | 2478篇 |
2018年 | 2440篇 |
2017年 | 2868篇 |
2016年 | 3203篇 |
2015年 | 3520篇 |
2014年 | 4786篇 |
2013年 | 4911篇 |
2012年 | 5884篇 |
2011年 | 5921篇 |
2010年 | 4706篇 |
2009年 | 4636篇 |
2008年 | 4514篇 |
2007年 | 5108篇 |
2006年 | 4429篇 |
2005年 | 3690篇 |
2004年 | 2964篇 |
2003年 | 2489篇 |
2002年 | 1929篇 |
2001年 | 1731篇 |
2000年 | 1549篇 |
1999年 | 1191篇 |
1998年 | 980篇 |
1997年 | 839篇 |
1996年 | 718篇 |
1995年 | 599篇 |
1994年 | 489篇 |
1993年 | 400篇 |
1992年 | 361篇 |
1991年 | 264篇 |
1990年 | 219篇 |
1989年 | 204篇 |
1988年 | 121篇 |
1987年 | 68篇 |
1986年 | 42篇 |
1985年 | 34篇 |
1984年 | 59篇 |
1983年 | 38篇 |
1982年 | 31篇 |
1981年 | 19篇 |
1980年 | 26篇 |
1979年 | 23篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1959年 | 7篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
N. A. Kochetov B. S. Seplyarskii S. G. Vadchenko 《International Journal of Self-Propagating High-Temperature Synthesis》2008,17(3):206-209
Combustion of bulk density Ti powder (containing 20 wt % TiN as a diluent) in a coflow of N2-Ar mixture was investigated upon variation in the nitrogen content of the gaseous mixture. The obtained data are believed
to open up new horizons for fabrication of layered and composite ceramics by infiltration-mediated combustion.
相似文献
22.
Epitaxial lamellar gallium selenide (GaSe) semiconductors have been grown on trench-patterned silicon (Si) substrates by molecular beam epitaxy. An intriguing star-like patterned morphology was identified by atomic force microscopy on these epilayers. This non-trivial feature can be correlated with the accumulation of stacking faults of two concurrent epitaxial domains around self-oriented triangular pits developed earlier on the Si(111) surface by the chemical etching. Crystallographic considerations show how the stars can be formed. 相似文献
23.
Ahmadreza Momeni Amir G. Aghdam 《International Journal of Adaptive Control and Signal Processing》2007,21(10):885-910
Most of the existing switching control techniques are developed specifically for finite-dimensional linear time-invariant (LTI) systems. In many practical applications, however, it is essential to take time delay into consideration in the modelling as the control system can be highly sensitive to delay. In this paper, a multi-model switching control algorithm is proposed for retarded time-delay systems. It is assumed that the plant is represented by a family of known multi-input multi-output, observable, LTI models with multiple delays in the states, and that corresponding to each model in the known family, there exists a high-performance finite-dimensional LTI controller. In addition, it is supposed that a bound on the magnitude of the external inputs and disturbances is available. It is then shown that the proposed switching controller can stabilize the uncertain system, and that under some mild conditions, output tracking can be achieved in the given problem setting. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
24.
25.
26.
Anumberoflanthanideternarycomplexescon tainingheterocyclicamineshavebeenreportedsince1960 [1] .Inrecentyearsmuchattentionhasbeenpaidtoquaternarycomplexesoflanthanidesbecauseofin terestingstructure ,coordinationmode ,competitionre actionandproperty[2~ 9] .ESRcane… 相似文献
27.
IR2520是自适应镇流器控制器与600V半桥驱动器单片IC ,可用来驱动半桥配置中的荧光灯。文中介绍了IR2520的主要特点和基本原理 ,给出了它的典型应用电路。 相似文献
28.
It is well recognized that performance changes over time. However, the effect of these changes on overall assessments of performance is largely unknown. In a laboratory experiment, we examined the influence of salient Gestalt characteristics of a dynamic performance profile on supervisory ratings. We manipulated performance trend (flat, linear-improving, linear-deteriorating, U-shaped, and ∩-shaped), performance variation (small, large), and performance mean (negative, zero, positive) within subjects and display format (graphic, tabular) between subjects. Participants received and evaluated information about the weekly performance of different employees over a simulated 26-week period. Results showed strong main effects on performance ratings of both performance mean and performance trend, as well as interactions with display format. Theoretical and practical implications of the results are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
29.
已往库存论中的决策模型,它是把现实过程用数学的方法进行分析,得到决策值,但不能看到决策的过程,不能反映出现实生活中的不确定性、动态性。运用Delphi 7.0和SQL server 2000对销售过程进行了动态仿真,利用Newsboy模型的推广(S,s)订购策略来监控库存并做出决策,这样就体现出此过程的不确定性、动态性;且举出了一个仿真商品销售的实例,对其中的一些关键技术,如何仿真、算法的实现等进行了阐述。 相似文献
30.
G. Bartolini A. Ferrara 《International Journal of Adaptive Control and Signal Processing》1992,6(3):237-246
In this paper we pursue a twofold aim. First we want to simplify the complexity of the classical Monopoli's scheme, the so-called ‘Augmented error signal control scheme’. Then we also wish to cope with the realistic situation in which the presence of unmodelled dynamics has to be taken into account. This latter problem has been faced in the literature by suitably modifying the adaptation mechanism in order to avoid undesired phenomena as well as to obtain an attractive stability region for the state trajectories starting from any point in a predefined initial condition set. In our case the necessity of introducing any sort of modification in the adaptation mechanism is completely avoided, but we still obtain asymptotic stability of the output error signal. 相似文献