全文获取类型
收费全文 | 28587篇 |
免费 | 3943篇 |
国内免费 | 2690篇 |
专业分类
电工技术 | 3144篇 |
综合类 | 3834篇 |
化学工业 | 2846篇 |
金属工艺 | 845篇 |
机械仪表 | 2282篇 |
建筑科学 | 1728篇 |
矿业工程 | 896篇 |
能源动力 | 979篇 |
轻工业 | 2071篇 |
水利工程 | 753篇 |
石油天然气 | 1013篇 |
武器工业 | 397篇 |
无线电 | 3046篇 |
一般工业技术 | 2575篇 |
冶金工业 | 658篇 |
原子能技术 | 172篇 |
自动化技术 | 7981篇 |
出版年
2024年 | 161篇 |
2023年 | 376篇 |
2022年 | 780篇 |
2021年 | 856篇 |
2020年 | 1017篇 |
2019年 | 883篇 |
2018年 | 892篇 |
2017年 | 1018篇 |
2016年 | 1175篇 |
2015年 | 1251篇 |
2014年 | 1775篇 |
2013年 | 1859篇 |
2012年 | 2342篇 |
2011年 | 2362篇 |
2010年 | 1800篇 |
2009年 | 1756篇 |
2008年 | 1762篇 |
2007年 | 2114篇 |
2006年 | 1711篇 |
2005年 | 1471篇 |
2004年 | 1219篇 |
2003年 | 1091篇 |
2002年 | 841篇 |
2001年 | 777篇 |
2000年 | 677篇 |
1999年 | 561篇 |
1998年 | 480篇 |
1997年 | 376篇 |
1996年 | 306篇 |
1995年 | 287篇 |
1994年 | 247篇 |
1993年 | 197篇 |
1992年 | 167篇 |
1991年 | 154篇 |
1990年 | 100篇 |
1989年 | 65篇 |
1988年 | 67篇 |
1987年 | 39篇 |
1986年 | 24篇 |
1985年 | 28篇 |
1984年 | 25篇 |
1983年 | 26篇 |
1982年 | 31篇 |
1981年 | 11篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1963年 | 3篇 |
1961年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
This paper presents an application of digital signal processing to data acquired by the radio imaging method (RIM) that was adopted to measure moisture distribution inside the human body. RIM was originally developed for the mining industry; we are applying the method to a biomedical measurement because of its simplicity, economy, and safety. When a two‐dimensional image was constructed from the measured data, the method provided insufficient resolution because the wavelength of the measurement medium, a weak electromagnetic wave in a VHF band, was longer than human tissues. We built and measured a phantom, a model simulating the human body, consisting of two water tanks representing large internal organs. A digital equalizer was applied to the measured values as a weight function, and images were reconstructed that corresponded to the original shape of the two water tanks. As a result, a two‐dimensional image containing two individual peaks corresponding to the original two small water tanks was constructed. The result suggests the method was applicable to biomedical measurement by the assistance of digital signal processing. This technique may be applicable to home‐based medical care and other situations in which safety, simplicity, and economy are important. 相似文献
72.
介绍了集团变分法的集团概率变量、配置熵等统计分析的理论基础及Helmholtz自由能的描述模型.提出了巨势及相对化学势的几何分析理论.讨论了应用集团变分法和巨势分析理论进行相平衡计算的过程,并分析了同结构平衡相图计算的若干实例. 相似文献
73.
74.
中国3G业务的市场需求有两个方面:一是迅猛增长、规模庞大的用户群对移动语音业务的需求;二是较高收入用户群对移动数据业务的需求。3G运营商的目标市场包括大众用户对移动语音的需求、大众用户对移动数据业务的需求、企业用户对移动数据业务的需求以及批发型用户的需求等。本结合国内外移动运营商的数据业务开展状况,初步探讨了中国3G运营商的移动数据业务模式和3G业务的收入模式。 相似文献
75.
The physical preconditions are considered for the temperature of a body to influence the force of gravity experienced by it. The results are given of experiments on weighing metal rods heated by ultrasound which confirm a dependence of the weight of the rods on their temperature. 相似文献
76.
A generalized equation was derived to calculate the melting temperatures of homopolymers and copolymers. The Gibbs‐Thomson equation for homopolymers and a modified application to copolymers were derived using the proposed equation. The melting temperature Tm0 in the Flory equation corresponds to the melting temperature TmC,∞ of copolymer crystals with stems of infinite length. Also, TmC,n*, the melting temperature for copolymer crystals with stems containing the maximum possible number of structural units, n*, should be used instead of Tm0 as the basis of supercooling in crystallization. The proposed equation shows good agreement with experimental data for α‐alkene‐ethylene homogeneous copolymers. 相似文献
77.
78.
This paper deals with the non-steady-state kinetics of direct thermal initiated polymerization. The initiation is assumed to be a bimolecular reaction of the monomer. The relationship between the radical concentration and the monomer conversion is rigorously derived. In further treatment a few very close approximations are introduced based on the fact that the number of monomer molecules reacting in the initiation step is much less than that consumed in the propagation step for a process producing high polymer, and the value of the rate constant for propagation or chain transfer is much lower than that for chain termination. Expressions for various molecular parameters, such as molecular weight distribution, number-average and weight-average degrees of polymerization, and dispersity, are given. Several numerical examples are provided. 相似文献
79.
本文仅利用输入输出数据给出了一种动态不确定多输入多输出系统的变结构控制器设计机制,控制系统的设计中引入了一个严格正实的模型.应用适当逻辑切换的状态变量滤波器实现变结构控制.证明了所提方案能保证全局输出有界稳定并能实现滑模控制和渐近跟踪参考模型的输出.该设计方案对结构不确定性具有一定的鲁棒性.仿真结果表明了所提方案的有效性. 相似文献
80.
本文综述我们对电脑气体选择性激发产生变色发光的理论研究和实验研究,并探讨这种类型变色发光的实际应用。 相似文献