全文获取类型
收费全文 | 3610篇 |
免费 | 446篇 |
国内免费 | 289篇 |
专业分类
电工技术 | 268篇 |
技术理论 | 1篇 |
综合类 | 594篇 |
化学工业 | 220篇 |
金属工艺 | 52篇 |
机械仪表 | 230篇 |
建筑科学 | 298篇 |
矿业工程 | 65篇 |
能源动力 | 63篇 |
轻工业 | 109篇 |
水利工程 | 48篇 |
石油天然气 | 60篇 |
武器工业 | 29篇 |
无线电 | 619篇 |
一般工业技术 | 288篇 |
冶金工业 | 116篇 |
原子能技术 | 17篇 |
自动化技术 | 1268篇 |
出版年
2024年 | 12篇 |
2023年 | 36篇 |
2022年 | 73篇 |
2021年 | 72篇 |
2020年 | 92篇 |
2019年 | 79篇 |
2018年 | 71篇 |
2017年 | 109篇 |
2016年 | 124篇 |
2015年 | 154篇 |
2014年 | 285篇 |
2013年 | 263篇 |
2012年 | 309篇 |
2011年 | 348篇 |
2010年 | 289篇 |
2009年 | 309篇 |
2008年 | 269篇 |
2007年 | 329篇 |
2006年 | 225篇 |
2005年 | 192篇 |
2004年 | 166篇 |
2003年 | 109篇 |
2002年 | 78篇 |
2001年 | 76篇 |
2000年 | 55篇 |
1999年 | 34篇 |
1998年 | 34篇 |
1997年 | 37篇 |
1996年 | 16篇 |
1995年 | 15篇 |
1994年 | 14篇 |
1993年 | 7篇 |
1992年 | 12篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1987年 | 2篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 2篇 |
1980年 | 3篇 |
1964年 | 1篇 |
1962年 | 1篇 |
1961年 | 2篇 |
1960年 | 2篇 |
1959年 | 1篇 |
1958年 | 1篇 |
1956年 | 1篇 |
1955年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有4345条查询结果,搜索用时 15 毫秒
1.
中国电信企业经过多年的高速发展,逐渐步入成熟期,增长率下降、利润降低将是必然趋势,因此目前亟需探索新的运营模式,向综合型全业务电信运营商的方向发展。法国电信集团历史悠久,市场转型起步早.其发展经验有许多地方值得借鉴,包括法国电信集团具有特色的品牌战咯、灵活的经营模式、为企业提供全方位服务的经营手段。中国电信企业应积极开展全业务经营,加快发展企业网市场,完善合作运营模式,争取早日走向世界。 相似文献
2.
In recent years, constructing a virtual backbone by nodes in a connected dominating set (CDS) has been proposed to improve the performance of ad hoc wireless networks. In general, a dominating set satisfies that every vertex in the graph is either in the set or adjacent to a vertex in the set. A CDS is a dominating set that also induces a connected sub‐graph. However, finding the minimum connected dominating set (MCDS) is a well‐known NP‐hard problem in graph theory. Approximation algorithms for MCDS have been proposed in the literature. Most of these algorithms suffer from a poor approximation ratio, and from high time complexity and message complexity. In this paper, we present a new distributed approximation algorithm that constructs a MCDS for wireless ad hoc networks based on a maximal independent set (MIS). Our algorithm, which is fully localized, has a constant approximation ratio, and O(n) time and O(n) message complexity. In this algorithm, each node only requires the knowledge of its one‐hop neighbours and there is only one shortest path connecting two dominators that are at most three hops away. We not only give theoretical performance analysis for our algorithm, but also conduct extensive simulation to compare our algorithm with other algorithms in the literature. Simulation results and theoretical analysis show that our algorithm has better efficiency and performance than others. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
3.
4.
van Baaren Rick B.; Maddux William W.; Chartrand Tanya L.; de Bouter Cris; van Knippenberg Ad 《Canadian Metallurgical Quarterly》2003,84(5):1093
The present studies demonstrated the moderation of self-construal orientation on mimicry. Recent research has indicated that an interdependent self-construal is associated with assimilation of the other to the self whereas an independent self-construal is associated with minimizing the influence of others on the self (H. R. Markus & S. Kitayama, 1991; D. Stapel & W. Koomen, 2001). Therefore, the authors hypothesized that an interdependent self-construal would be associated with more mimicry than an independent self-construal. When self-construal orientations were experimentally primed. as in Studies 1 and 2, independent self-construals produced less nonconscious mimicry than interdependent self-construals. When self-construals were examined as cultural differences with either a chronically dominant independent (Americans) or interdependent (Japanese) construal of the self, these results were replicated. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
5.
According to the knowledge partitioning framework, people sometimes master complex tasks by creating multiple independent parcels of partial knowledge. Research has shown that knowledge parcels may contain mutually contradictory information, and that each parcel may be used without regard to knowledge that is demonstrably present in other parcels. This article reports 4 experiments that investigated knowledge partitioning in categorization. When component boundaries of a complex categorization were identified by a context cue, a significant proportion of participants learned partial and independent categorization strategies that were chosen on the basis of context. For those participants, a strategy used in one context was unaffected by knowledge demonstrably present in other contexts, suggesting that knowledge partitioning in categorization can be complete. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
7.
利用独立分量分析法去除地震噪声 总被引:2,自引:0,他引:2
独立分量分析(ICA)作为盲源分离(BSS)的一种新方法,是分解观测数据中独立信息的有力工具。以往的ICA算法一般假设噪声可以忽略不计,而实际的观测数据中又常常包含一些加性噪声。对于加性噪声的影响不能忽略的情况下,改进的ICA算法首先利用非零时间滞后协方差,应用两步特征值分解法(EVD)可成功地去除部分加性噪声的影响;再利用ICA算法就能更好地分离出原信号。本文通过对地震理论模型和实际资料的试验,说明改进的ICA算法能够有效地克服加性噪声对常规ICA算法的影响,能够分离出地震资料中的有效信号,从而实现利用独立分量分析压制地震资料噪声的目的。 相似文献
8.
金永杰 《核电子学与探测技术》1989,9(1):10-17
本文所提出的投影域重建——再投影迭代算法可以恢复不完整的扇形束投影数据,从而实现从有限的投影数据重建图象。这种算法把滤波——反投影图象重建过程和再投影的过程纳入一个公式,仅在投影域上估算未知的投影数据,因此避免了重建过程和反投影过程中的插值运算,改善了收敛性,提高了计算精度,缩短了运算时间。模拟实验表明:即使有70%的投影数据丢失,经过两次迭代就能以令人满意的精度恢复丢失的投影数据。 相似文献
9.
钕铁硼在低音扬声器磁路中的应用 总被引:1,自引:1,他引:0
介绍适用于低音扬声器的两种不同充磁方向磁体联合应用磁路。讨论了联合应用磁路所用钕铁硼磁体的压制成型、磁性能检验、装配和充磁。 相似文献
10.
Thomas J. R. Hughes Arif Masud Isaac Harari 《International journal for numerical methods in engineering》1995,38(19):3193-3210
Finite element methods for dynamic analysis employing elements with drilling degrees of freedom are presented. The formulation is based on a variational principle in which displacements and rotations are interpolated independently. The issue of zero masses corresponding to rotational degrees of freedom is addressed and techniques for defining consistent and lumped rotational mass matrices are presented. 相似文献