全文获取类型
收费全文 | 2137篇 |
免费 | 254篇 |
国内免费 | 93篇 |
专业分类
电工技术 | 134篇 |
综合类 | 183篇 |
化学工业 | 298篇 |
金属工艺 | 109篇 |
机械仪表 | 159篇 |
建筑科学 | 159篇 |
矿业工程 | 110篇 |
能源动力 | 54篇 |
轻工业 | 93篇 |
水利工程 | 64篇 |
石油天然气 | 80篇 |
武器工业 | 8篇 |
无线电 | 240篇 |
一般工业技术 | 248篇 |
冶金工业 | 132篇 |
原子能技术 | 11篇 |
自动化技术 | 402篇 |
出版年
2024年 | 5篇 |
2023年 | 40篇 |
2022年 | 79篇 |
2021年 | 104篇 |
2020年 | 87篇 |
2019年 | 81篇 |
2018年 | 70篇 |
2017年 | 71篇 |
2016年 | 75篇 |
2015年 | 105篇 |
2014年 | 102篇 |
2013年 | 126篇 |
2012年 | 145篇 |
2011年 | 122篇 |
2010年 | 112篇 |
2009年 | 119篇 |
2008年 | 90篇 |
2007年 | 106篇 |
2006年 | 108篇 |
2005年 | 66篇 |
2004年 | 65篇 |
2003年 | 85篇 |
2002年 | 131篇 |
2001年 | 90篇 |
2000年 | 84篇 |
1999年 | 62篇 |
1998年 | 32篇 |
1997年 | 19篇 |
1996年 | 16篇 |
1995年 | 18篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1975年 | 2篇 |
排序方式: 共有2484条查询结果,搜索用时 15 毫秒
1.
2.
Fatigue testing of polymers has revealed significant differences between the fatigue response of polymers and metals. Generally, fatigue failure in metals is a process of crack initiation, propagation, and failure. Also, fatigue damage in metals is cumulative and cycle dependent, but remains essentially independent of test frequency. Unlike that of metals, the fatigue behavior of polymers is influenced by viscoelastic effects. At high frequencies, softening and melting occur, and fatigue failure depends largely on the test frequency. At lower frequencies, fatigue failure becomes less sensitive to test frequency and results from crack initiation and propagation. These polymer characteristics arise from the production of hysteresis energy during fatigue. A portion of this energy is released as heat, some of which is dissipated, but most is absorbed in the sample, raising its temperature. This temperature rise leads to degradation of the material and a short fatigue life. Experiments were conducted to measure hysteresis energy and temperature rise for a talc-filled polypropylene. A mathematical model was developed to calculate the energy and temperature distribution during fatigue. Correlation of the temperature rise predicted by the model with that observed experimentally provided values for the various energy terms that quantitatively defined the thermomechanical fatigue response of this polymer. 相似文献
3.
宫立刚 《中国水能及电气化》2017,(4)
水库下游临岸潜流带水流场响应规律可用于预测不同水库运行情景下临岸潜流带的水头与流量变化情况。本文以复州河东风水库为例,基于测量数据得到其下游某断面临岸潜流带的水头及流量响应过程,提出响应强度指标的概念,得到简单直观的响应规律经验公式,从而为该水库下游临岸系统的生态建设提供依据,并为水库运行方案的生态影响评价提供参考。 相似文献
4.
We propose a fast method for 3D shape segmentation and labeling via Extreme Learning Machine (ELM). Given a set of example shapes with labeled segmentation, we train an ELM classifier and use it to produce initial segmentation for test shapes. Based on the initial segmentation, we compute the final smooth segmentation through a graph‐cut optimization constrained by the super‐face boundaries obtained by over‐segmentation and the active contours computed from ELM segmentation. Experimental results show that our method achieves comparable results against the state‐of‐the‐arts, but reduces the training time by approximately two orders of magnitude, both for face‐level and super‐face‐level, making it scale well for large datasets. Based on such notable improvement, we demonstrate the application of our method for fast online sequential learning for 3D shape segmentation at face level, as well as realtime sequential learning at super‐face level. 相似文献
5.
Minh-Son Dao Duc-Tien Dang-Nguyen Francesco G. B. De Natale 《Multimedia Tools and Applications》2014,70(1):25-53
Analyzing personal photo albums for understanding the related events is an emerging trend. A reliable event recognition tool could suggest appropriate annotation of pictures, provide the context for single image classification and tagging, achieve automatic selection and summarization, ease organization and sharing of media among users. In this paper, a novel method for fast and reliable event-type classification of personal photo albums is presented. Differently from previous approaches, the proposed method does not process photos individually but as a whole, exploiting three main features, namely Saliency, Gist, and Time, to extract an event signature, which is characteristic for a specific event type. A highly challenging database containing more than 40.000 photos belonging to 19 diverse event-types was crawled from photo-sharing websites for the purpose of modeling and performance evaluation. Experimental results showed that the proposed approach meets superior classification accuracy with limited computational complexity. 相似文献
6.
Semi‐Markovian jump systems, due to the relaxed conditions on the stochastic process, and its transition rates are time varying, can be used to describe a larger class of dynamical systems than conventional full Markovian jump systems. In this paper, the problem of stochastic stability for a class of semi‐Markovian systems with mode‐dependent time‐variant delays is investigated. By Lyapunov function approach, together with a piecewise analysis method, a sufficient condition is proposed to guarantee the stochastic stability of the underlying systems. As more time‐delay information is used, our results are much less conservative than some existing ones in literature. Finally, two examples are given to show the effectiveness and advantages of the proposed techniques. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
7.
8.
Pham Phuc Hong Dinh Toan Khac Dang Lam Bao Nguyen Khoa Tuan Dao Dzung Viet 《Microsystem Technologies》2015,21(3):699-706
Microsystem Technologies - This paper reports a design and fabrication process of a micro cam system (MCS) with a flat-faced translating follower. The cam rim with cover diameter of 2.4 mm... 相似文献
9.
10.
安全协议是现代网络安全的基础,密码协议的安全性证明是一个挑战性的问题。事件逻辑是一种描述分布式系统中状态迁移的形式化方法,用于刻画安全协议的形式化描述,是定理证明的基础。用事件序语言、事件类和一个表示随机数、密钥、签名和密文的原子类,给出身份认证协议可以被形式化定义和强认证性证明理论。利用该理论对增加时间戳的Needham-Schroeder协议安全性进行证明,证明改进的Needham-Schroeder协议是安全的。此理论适用于类似复杂协议形式化分析与验证。 相似文献