全文获取类型
收费全文 | 43776篇 |
免费 | 1364篇 |
国内免费 | 1046篇 |
专业分类
电工技术 | 908篇 |
综合类 | 591篇 |
化学工业 | 6107篇 |
金属工艺 | 2754篇 |
机械仪表 | 1677篇 |
建筑科学 | 1316篇 |
矿业工程 | 224篇 |
能源动力 | 1421篇 |
轻工业 | 3194篇 |
水利工程 | 394篇 |
石油天然气 | 544篇 |
武器工业 | 32篇 |
无线电 | 5108篇 |
一般工业技术 | 9394篇 |
冶金工业 | 7503篇 |
原子能技术 | 478篇 |
自动化技术 | 4541篇 |
出版年
2023年 | 140篇 |
2022年 | 324篇 |
2021年 | 645篇 |
2020年 | 399篇 |
2019年 | 575篇 |
2018年 | 788篇 |
2017年 | 746篇 |
2016年 | 845篇 |
2015年 | 699篇 |
2014年 | 1083篇 |
2013年 | 2538篇 |
2012年 | 1683篇 |
2011年 | 2351篇 |
2010年 | 1826篇 |
2009年 | 2080篇 |
2008年 | 2073篇 |
2007年 | 2100篇 |
2006年 | 1830篇 |
2005年 | 1627篇 |
2004年 | 1529篇 |
2003年 | 1687篇 |
2002年 | 1940篇 |
2001年 | 1745篇 |
2000年 | 1289篇 |
1999年 | 1263篇 |
1998年 | 2786篇 |
1997年 | 1903篇 |
1996年 | 1538篇 |
1995年 | 987篇 |
1994年 | 768篇 |
1993年 | 714篇 |
1992年 | 431篇 |
1991年 | 396篇 |
1990年 | 301篇 |
1989年 | 302篇 |
1988年 | 249篇 |
1987年 | 195篇 |
1986年 | 170篇 |
1985年 | 208篇 |
1984年 | 122篇 |
1983年 | 121篇 |
1982年 | 108篇 |
1981年 | 131篇 |
1980年 | 114篇 |
1979年 | 69篇 |
1978年 | 57篇 |
1977年 | 108篇 |
1976年 | 211篇 |
1975年 | 62篇 |
1973年 | 62篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Graph determines the performance of graph-based semi-supervised classification. In this paper, we investigate how to construct a graph from multiple clusterings and propose a method called Semi-Supervised Classification using Multiple Clusterings (SSCMC in short). SSCMC firstly projects original samples into different random subspaces and performs clustering on the projected samples. Then, it constructs a graph by setting an edge between two samples if these two samples are clustered in the same cluster for each clustering. Next, it combines these graphs into a composite graph and incorporates the resulting composite graph with a graph-based semi-supervised classifier based on local and global consistency. Our experimental results on two publicly available facial images show that SSCMC not only achieves higher accuracy than other related methods, but also is robust to input parameters. 相似文献
992.
I. Dimbwadyo-Terrer F. Trincado-Alonso A. De los Reyes-Guzmán P. López-Monteagudo B. Polonio-López A. Gil-Agudo 《Virtual Reality》2016,20(1):17-26
The main objective of this study was to analyze the correlations between functional scales and kinematic data collected during the execution of upper limb (UL) basic activities of daily living in an immersive virtual reality (VR) environment. Fifteen people with tetraplegia participated in the study. Moreover, we also want to confirm if changes in UL functional performance detected by functional scales are also detected by the VR system Toyra®. Patients were assessed before and after 4 weeks of daily conventional rehabilitation treatment complemented with a training with the VR system. Significant positive correlations between kinematic and functional parameters were found in the post assessment, verifying that changes in UL functional performance detected by functional scales are also measured by the VR system Toyra®, concretely the related to shoulder movements. Additionally, a predefined Agility metric has been applied, showing inversely proportional results to the level of injury, as we expected. The self-care category of the Spinal Cord Independence Measure (SCIM III) and the ranges of motion (ROM) captured with the VR system were analyzed, showing statistical significance changes between pre-post evaluations, supporting the hypothesis that kinematic analysis complements clinical and functional assessments of patients with tetraplegia. 相似文献
993.
Simone Marras James F. Kelly Margarida Moragues Andreas Müller Michal A. Kopera Mariano Vázquez Francis X. Giraldo Guillaume Houzeaux Oriol Jorba 《Archives of Computational Methods in Engineering》2016,23(4):673-722
Numerical weather prediction (NWP) is in a period of transition. As resolutions increase, global models are moving towards fully nonhydrostatic dynamical cores, with the local and global models using the same governing equations; therefore we have reached a point where it will be necessary to use a single model for both applications. The new dynamical cores at the heart of these unified models are designed to scale efficiently on clusters with hundreds of thousands or even millions of CPU cores and GPUs. Operational and research NWP codes currently use a wide range of numerical methods: finite differences, spectral transform, finite volumes and, increasingly, finite/spectral elements and discontinuous Galerkin, which constitute element-based Galerkin (EBG) methods. Due to their important role in this transition, will EBGs be the dominant power behind NWP in the next 10 years, or will they just be one of many methods to choose from? One decade after the review of numerical methods for atmospheric modeling by Steppeler et al. (Meteorol Atmos Phys 82:287–301, 2003), this review discusses EBG methods as a viable numerical approach for the next-generation NWP models. One well-known weakness of EBG methods is the generation of unphysical oscillations in advection-dominated flows; special attention is hence devoted to dissipation-based stabilization methods. Since EBGs are geometrically flexible and allow both conforming and non-conforming meshes, as well as grid adaptivity, this review is concluded with a short overview of how mesh generation and dynamic mesh refinement are becoming as important for atmospheric modeling as they have been for engineering applications for many years. 相似文献
994.
Davide Rotta Marco De Michielis Elena Ferraro Marco Fanciulli Enrico Prati 《Quantum Information Processing》2016,15(6):2253-2274
Scalability from single-qubit operations to multi-qubit circuits for quantum information processing requires architecture-specific implementations. Semiconductor hybrid qubit architecture is a suitable candidate to realize large-scale quantum information processing, as it combines a universal set of logic gates with fast and all-electrical manipulation of qubits. We propose an implementation of hybrid qubits, based on Si metal-oxide-semiconductor (MOS) quantum dots, compatible with the CMOS industrial technological standards. We discuss the realization of multi-qubit circuits capable of fault-tolerant computation and quantum error correction, by evaluating the time and space resources needed for their implementation. As a result, the maximum density of quantum information is extracted from a circuit including eight logical qubits encoded by the [[7, 1, 3]] Steane code. The corresponding surface density of logical qubits is 2.6 Mqubit/cm\(^2\). 相似文献
995.
Beatriz Pariente-Martinez Martin Gonzalez-Rodriguez Daniel Fernandez-Lanvin Javier De Andres-Suarez 《Universal Access in the Information Society》2016,15(2):237-247
The influence of aging on computer interaction has been widely analyzed in human–computer interaction research literature. Despite this, there are no age-based user maps that could support the user-interface customization. Studying the specific needs and constraints of these groups is crucial in order to adapt a user interface to the user’s interaction requirements. This work studies the performance of a sample of participants on three different basic tasks (pointing, dragging and dropping, and text selection) and the influence of age for each of them. It is concluded that this influence differs between specific activities. A group profile map that can support automatic classification in the future has been obtained. 相似文献
996.
一种基于DTW的新型故事时间序列相似性度量方法 总被引:1,自引:0,他引:1
现有时间序列相似性度量方法在进行股市序列相似性分析时,通常忽略成交量等其他重要因素对股价的影响,从而导致序列聚类、分类不精确。针对这一问题,本文提出了新的股市时间序列相似性度量方法。该方法在动态时间弯曲算法的基础上,通过引进时间衰竭因子,并结合成交量因素,给出了股市序列的最终度量公式。为了证明提出方法的可行性和有效性,本文实验部分通过选取家电等三个行业中的股票数据进行测试。实验结果表明,基于动态时间弯曲(Dynamic time warping,DTW)的新型股市时间序列相似性度量方法能够在保持股票序列形态特征的基础上,较好地解决股市技术分析中量价关系问题,从而更有效地应用于股市技术分析里关于模式发现等领域。 相似文献
997.
提出了一种基于灰关联混合蛙跳算法的雷达波形设计方法,以混合蛙跳算法为主体,在局部更
新算子中引入遗传算法的遗传算子,并改进原始蛙跳算法的分组方法,丰富了种群的多样性,同时引入灰关联综合评价法则对适应度函数值加以关联度分析。文中以设计具有低自相关旁瓣和互相关特性的正交多相编码为例,将该算法用于雷达波形设计中。仿真结果表明使用本文算法产生
的波形具备较好的低自相关特性和互相关特性,表明了该算法是有效和可行的。 相似文献
998.
Probability‐weighted nonlinear stochastic optimal control strategy of quasi‐integrable Hamiltonian systems with uncertain parameters 下载免费PDF全文
The nonlinear stochastic optimal control problem of quasi‐integrable Hamiltonian systems with uncertain parameters is investigated. The uncertain parameters are described by using a random vector with λ probability density function. First, the partially averaged Itô stochastic differential equations are derived by using the stochastic averaging method for quasi‐integrable Hamiltonian systems. Then, the dynamical programming equation is established based on stochastic dynamical programming principle. By minimizing the dynamical programming equation with respect to control forces, the optimal control forces can be derived, which are functions of the uncertain parameters. The final optimal control forces are then determined by probability‐weighted average of the obtained control forces with the probability density of the uncertain parameters as weighting function. The mean control effectiveness and mean control efficiency are used to evaluate the proposed control strategy. The robustness of the proposed control is measured by using the ratios of the variation coefficients of mean control effectiveness and mean control efficiency to the variation coefficients of uncertain parameters. Finally, two examples are given to illustrate the proposed control strategy and its effectiveness and robustness. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
999.
1000.
Artificial neural networks modeling have recently acquired enormous importance in microwave community especially in analyzing and synthesizing of microstrip antennas (MSAs) due to their generalization and adaptability features. A trained neural model estimates response very fast, which is nearly equal to its measured and/or simulated counterpart. Thus, it completely bypasses the repetitive use of conventional models as these models need rediscretization for every minor changes in the geometry, which itself is a time‐consuming exercise. The purpose of this article is to review this emerging area comprehensively for both analyzing and synthesizing of the MSAs. During reviewing process, some untouched cases are also observed, which are essentially required to be resolved for antenna designers. Unique and efficient neural networks‐based solutions are suggested for these cases. The proposed neural approaches are validated by fabricating and characterizing of the prototypes too. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:747–757, 2015. 相似文献