全文获取类型
收费全文 | 7798篇 |
免费 | 702篇 |
国内免费 | 525篇 |
专业分类
电工技术 | 555篇 |
技术理论 | 5篇 |
综合类 | 913篇 |
化学工业 | 593篇 |
金属工艺 | 153篇 |
机械仪表 | 499篇 |
建筑科学 | 788篇 |
矿业工程 | 146篇 |
能源动力 | 263篇 |
轻工业 | 192篇 |
水利工程 | 282篇 |
石油天然气 | 173篇 |
武器工业 | 62篇 |
无线电 | 885篇 |
一般工业技术 | 1028篇 |
冶金工业 | 384篇 |
原子能技术 | 64篇 |
自动化技术 | 2040篇 |
出版年
2024年 | 17篇 |
2023年 | 88篇 |
2022年 | 124篇 |
2021年 | 160篇 |
2020年 | 192篇 |
2019年 | 220篇 |
2018年 | 200篇 |
2017年 | 261篇 |
2016年 | 281篇 |
2015年 | 312篇 |
2014年 | 433篇 |
2013年 | 561篇 |
2012年 | 486篇 |
2011年 | 625篇 |
2010年 | 472篇 |
2009年 | 497篇 |
2008年 | 487篇 |
2007年 | 575篇 |
2006年 | 503篇 |
2005年 | 414篇 |
2004年 | 354篇 |
2003年 | 308篇 |
2002年 | 248篇 |
2001年 | 190篇 |
2000年 | 160篇 |
1999年 | 127篇 |
1998年 | 120篇 |
1997年 | 92篇 |
1996年 | 94篇 |
1995年 | 70篇 |
1994年 | 57篇 |
1993年 | 40篇 |
1992年 | 51篇 |
1991年 | 30篇 |
1990年 | 33篇 |
1989年 | 23篇 |
1988年 | 17篇 |
1987年 | 11篇 |
1986年 | 11篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1978年 | 3篇 |
1964年 | 3篇 |
1960年 | 3篇 |
1958年 | 3篇 |
1957年 | 6篇 |
1955年 | 4篇 |
1954年 | 3篇 |
排序方式: 共有9025条查询结果,搜索用时 15 毫秒
81.
82.
83.
Various problems are encountered when adopting ordinary vector space algorithms for high-order tensor data input. Namely, one must overcome the Small Sample Size (SSS) and overfitting problems. In addition, the structural information of the original tensor signal is lost during the vectorization process. Therefore, comparable methods using a direct tensor input are more appropriate. In the case of electrocardiograms (ECGs), another problem must be overcome; the manual diagnosis of ECG data is expensive and time consuming, rendering it difficult to acquire data with diagnosis labels. However, when effective features for classification in the original data are very sparse, we propose a semisupervised sparse multilinear discriminant analysis (SSSMDA) method. This method uses the distribution of both the labeled and the unlabeled data together with labels discovered through a label propagation Mgorithm. In practice, we use 12-lead ECGs collected from a remote diagnosis system and apply a short-time-fourier transformation (STFT) to obtain third-order tensors. The experimental results highlight the sparsity of the ECG data and the ability of our method to extract sparse and effective features that can be used for classification. 相似文献
84.
本文研究了一种以非离子表面活性剂吐温-20为介质,硫酸钡浊度法侧定水泥中三氧化硫的新方法。吐温-20的引入使硫酸钡颗粒分散均匀,体系稳定性提高。本文选420nm为测定波长,SO2-4含量在50~500μg/25ml范围内线性关系良好,可很好地适用于水泥样品的分析。 相似文献
85.
概述了研究定向结晶过程传递问题的分形方法,并对各类数学模型进行了分析,探讨了进一步研究的方向和途径。 相似文献
86.
J. Linares-Pérez R. Caballero-Águila I. García-Garrido 《International journal of systems science》2014,45(7):1548-1562
This paper addresses the optimal least-squares linear estimation problem for a class of discrete-time stochastic systems with random parameter matrices and correlated additive noises. The system presents the following main features: (1) one-step correlated and cross-correlated random parameter matrices in the observation equation are assumed; (2) the process and measurement noises are one-step autocorrelated and two-step cross-correlated. Using an innovation approach and these correlation assumptions, a recursive algorithm with a simple computational procedure is derived for the optimal linear filter. As a significant application of the proposed results, the optimal recursive filtering problem in multi-sensor systems with missing measurements and random delays can be addressed. Numerical simulation examples are used to demonstrate the feasibility of the proposed filtering algorithm, which is also compared with other filters that have been proposed. 相似文献
87.
北京市雨水收集利用蓄水池容积计算与分析 总被引:1,自引:0,他引:1
基于北京市1984—2013年的日降雨资料,以北京林业大学林业楼及其周边绿地为研究区,设置3种用水情景(冲厕、绿地灌溉及冲厕+绿地灌溉),采用连续模拟法,分别绘制3种用水情景下雨水收集利用工程的雨水截留率、自来水替代率、供水保证率以及效益费用比变化曲线,并通过综合分析这些曲线的变化特征确定雨水蓄水池最佳设计容积(60~82 m3)。同时采用设计暴雨法计算1~5年不同重现期的蓄水池设计容积(77~248 m3)。结果表明,连续模拟法计算过程相对复杂,但可用于综合衡量雨水收集利用工程的雨洪管理效益,以及缓解水资源短缺效益、供水可靠性及经济可行性分析。 相似文献
88.
针对数据校正中的非线性数据分类还比较困难的问题,提出表上作业法,结合遗传算法同时进行数据协调与过失误差侦破.并将模糊数据协调模型中的三角形约束引入遗传算法界定其变异上下限,还对交叉算子进行自适应改进,从而形成了基于模糊自适应的数据校正方法并用该方法对一个稳态多组分精馏过程进行大量仿真试验,结果表明了算法的有效性. 相似文献
89.
Three-dimensional simulation using fixed coarse-grid thermal-fluid scheme and conduction heat transfer scheme in distinct element method 总被引:1,自引:0,他引:1
Yoshiyuki Shimizu 《Powder Technology》2006,165(3):140-152
Three-dimensional simulation using particle-thermal-fluid coupling scheme with a mixed Lagrangian-Eulerian approach is presented and the scheme is described by extending author's previous research [Y. Shimizu, 2004. “Fluid Coupling in PFC2D and PFC3D”, numerical modeling in micromechanics via particle methods—2004, Proceeding of 2nd International PFC Conference, Balkema, 2004, pp. 281-287]. The scheme solves the continuity, Navier-Stokes (N-S) and thermal energy equations numerically in Eulerian Cartesian coordinates, then derives pressure, velocity vectors and temperature for each fixed cell by considering particle existence. On the other hand, driving forces and thermal energy from fluid are applied to the particles as external body forces and a source term in the force-displacement law and the heat transfer calculations, respectively. This paper describes the thermal scheme for both fluid and particles. Results of two- and three-dimensional simulations involving forced convective heat transfer by fluid and conduction heat transfer within particles are presented. 相似文献
90.
This work shows how to use a differential geometry tool to design a novel nonlinear active fault tolerant flight control system for aircraft. The proposed control scheme consists of two main subsystems: a controller, which is designed for the nominal plant, and a fault detection and diagnosis module, which provides fault estimation. A further feedback loop exploits the fault estimation to accommodate faults affecting the system. The estimate convergence and the stability of the active fault tolerant flight controller are theoretically proved. Finally, high fidelity simulations show the effectiveness of the scheme. 相似文献