全文获取类型
收费全文 | 4935篇 |
免费 | 744篇 |
国内免费 | 476篇 |
专业分类
电工技术 | 556篇 |
技术理论 | 1篇 |
综合类 | 705篇 |
化学工业 | 172篇 |
金属工艺 | 70篇 |
机械仪表 | 319篇 |
建筑科学 | 294篇 |
矿业工程 | 152篇 |
能源动力 | 103篇 |
轻工业 | 139篇 |
水利工程 | 143篇 |
石油天然气 | 342篇 |
武器工业 | 106篇 |
无线电 | 447篇 |
一般工业技术 | 562篇 |
冶金工业 | 294篇 |
原子能技术 | 43篇 |
自动化技术 | 1707篇 |
出版年
2024年 | 20篇 |
2023年 | 68篇 |
2022年 | 138篇 |
2021年 | 158篇 |
2020年 | 209篇 |
2019年 | 189篇 |
2018年 | 178篇 |
2017年 | 201篇 |
2016年 | 216篇 |
2015年 | 257篇 |
2014年 | 315篇 |
2013年 | 408篇 |
2012年 | 384篇 |
2011年 | 394篇 |
2010年 | 291篇 |
2009年 | 316篇 |
2008年 | 301篇 |
2007年 | 344篇 |
2006年 | 269篇 |
2005年 | 250篇 |
2004年 | 221篇 |
2003年 | 168篇 |
2002年 | 148篇 |
2001年 | 104篇 |
2000年 | 91篇 |
1999年 | 97篇 |
1998年 | 52篇 |
1997年 | 57篇 |
1996年 | 49篇 |
1995年 | 46篇 |
1994年 | 55篇 |
1993年 | 35篇 |
1992年 | 23篇 |
1991年 | 18篇 |
1990年 | 16篇 |
1989年 | 14篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1977年 | 2篇 |
1965年 | 2篇 |
1962年 | 4篇 |
1959年 | 3篇 |
1958年 | 2篇 |
1957年 | 5篇 |
1955年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有6155条查询结果,搜索用时 187 毫秒
1.
2.
In this paper, permanent magnet synchronous motors (PMSMs) are investigated. According to the feature of PMSMs, a novel state equation of PMSMs is obtained by choosing suitable state variables. Based on the state equation, robust controllers are designed via interval matrix and PI control idea. In terms of bilinear matrix inequations, sufficient conditions for the existence of the robust controller are derived. In order to reduce the conservation and the dependence on parameter, the control inputs of PMSMs are divided into two parts, a feedforward control input and a feedback control input, and relevant sufficient conditions for the existence of the controller are obtained. Because of the suitable choice of state variables, the proposed control strategies can cope with the load uncertainty and have robustness for disturbance. Finally, simulations are carried out via Matlab/Simulink soft to verify the effectiveness of the proposed control strategies. The performance of the proposed control strategies are demonstrated by the simulation results. 相似文献
3.
结合松辽盆地大庆长垣西侧扶余、杨大城子油层的勘探实践,从顶生下储的特殊成藏原理出发,详细地讨论了扶余、杨大城子油层的油水层形成机理,提出了2种形成模式。认为扶杨油层的油水同层是在以上覆烃源岩的超压为驱动力的成藏条件下形成,油水混合运移注入储层,由于储层的孔喉小,油水重力分异不好,造成孔隙存油,喉道存水。这种低渗透储层孔隙结构复杂,含油饱和度低,油水在孔隙中分布状况特殊,使得电阻率等曲线反映流体的信息变弱,造成油水层识别变难。为此提出多参数降维油气水层识别方法,经实际应用取得较好的效果。 相似文献
4.
中原油田岩石可钻性与声波时差关系研究 总被引:3,自引:0,他引:3
选取中原油田的大量岩心,采用常规岩石力学测试方法测定了岩石的可钻性、声波测试方法测定了岩石和岩屑声波时差,通过对测得的岩石可钻性级值和声波时差进行回归拟合,得出了中原油田岩石可钻性与声波时差的关系式。现场应用表明,该关系式较好地反映了中原油田地层岩石可钻性与声波时差的关系,可以在优选钻头时作为参考或直接应用。 相似文献
5.
1 IntroductionThestickingpointofassociationrulealgorithmsdependsoneffectivelyfindingallcorrelationpatternsthatsatisfyvaluerequirementinthemagnanimityofdata.Butthealgorithmsalsobringanegativeef fect:thenumberofassociationrulesisverylarge.Alsoinformation… 相似文献
6.
The Clopper-Pearson confidence interval has ever been documented as an exact approach in some statistics literature. More recently, such approach of interval estimation has been introduced to probabilistic control theory and has been referred as non-conservative in control community. In this note, we clarify the fact that the so-called exact approach is actually conservative. In particular, we derive analytic results demonstrating the extent of conservatism in the context of probabilistic robustness analysis. This investigation encourages seeking better methods of confidence interval construction for robust control purpose. 相似文献
7.
Drew Michael R.; Yang Cynthia; Ohyama Tatsuya; Balsam Peter D. 《Canadian Metallurgical Quarterly》2004,30(3):163
Three experiments investigated the effects of varying the conditioned stimulus (CS) duration between training and extinction. Ring doves (Streptopelia risoria) were autoshaped on a fixed CS-unconditioned stimulus (US) interval and extinguished with CS presentations that were longer, shorter, or the same as the training duration. During a subsequent test session, the training CS duration was reintroduced. Results suggest that the cessation of responding during an extinction session is controlled by generalization of excitation between the training and extinction CSs and by the number of nonreinforced CS presentations. Transfer of extinction to the training CS is controlled by the similarity between the extinction and training CSs. Extinction learning is temporally specific. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
8.
9.
线性时变系统的区间稳定性与鲁棒稳定性 总被引:7,自引:0,他引:7
本文应用向量比较定理研究线性时变系统的区间稳定性和具非线性时变摄动的线性时变系统的鲁棒稳定性,所得的新结果包含文献的一些主要结果作为特例,本文的研究方法说明向量比较方法是分析区间稳定性和鲁棒稳定性的一种自然而有力的工具。 相似文献
10.
One of the most frequently cited reasons for conducting a meta-analysis is the increase in statistical power that it affords a reviewer. This article demonstrates that fixed-effects meta-analysis increases statistical power by reducing the standard error of the weighted average effect size (T?.) and, in so doing, shrinks the confidence interval around T?.. Small confidence intervals make it more likely for reviewers to detect nonzero population effects, thereby increasing statistical power. Smaller confidence intervals also represent increased precision of the estimated population effect size. Computational examples are provided for 3 effect-size indices: d (standardized mean difference), Pearson's r, and odds ratios. Random-effects meta-analyses also may show increased statistical power and a smaller standard error of the weighted average effect size. However, the authors demonstrate that increasing the number of studies in a random-effects meta-analysis does not always increase statistical power. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献