全文获取类型
收费全文 | 29197篇 |
免费 | 2698篇 |
国内免费 | 2249篇 |
专业分类
电工技术 | 2183篇 |
技术理论 | 2篇 |
综合类 | 2113篇 |
化学工业 | 2364篇 |
金属工艺 | 737篇 |
机械仪表 | 2233篇 |
建筑科学 | 2387篇 |
矿业工程 | 848篇 |
能源动力 | 836篇 |
轻工业 | 1009篇 |
水利工程 | 910篇 |
石油天然气 | 1001篇 |
武器工业 | 194篇 |
无线电 | 2639篇 |
一般工业技术 | 1596篇 |
冶金工业 | 1033篇 |
原子能技术 | 162篇 |
自动化技术 | 11897篇 |
出版年
2024年 | 112篇 |
2023年 | 345篇 |
2022年 | 668篇 |
2021年 | 750篇 |
2020年 | 771篇 |
2019年 | 701篇 |
2018年 | 679篇 |
2017年 | 834篇 |
2016年 | 980篇 |
2015年 | 1125篇 |
2014年 | 1974篇 |
2013年 | 1823篇 |
2012年 | 2146篇 |
2011年 | 2570篇 |
2010年 | 1870篇 |
2009年 | 1839篇 |
2008年 | 1864篇 |
2007年 | 2085篇 |
2006年 | 1811篇 |
2005年 | 1532篇 |
2004年 | 1327篇 |
2003年 | 1252篇 |
2002年 | 1002篇 |
2001年 | 785篇 |
2000年 | 572篇 |
1999年 | 503篇 |
1998年 | 404篇 |
1997年 | 338篇 |
1996年 | 280篇 |
1995年 | 236篇 |
1994年 | 184篇 |
1993年 | 127篇 |
1992年 | 113篇 |
1991年 | 78篇 |
1990年 | 61篇 |
1989年 | 64篇 |
1988年 | 47篇 |
1987年 | 20篇 |
1986年 | 26篇 |
1985年 | 41篇 |
1984年 | 25篇 |
1983年 | 22篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1980年 | 13篇 |
1979年 | 8篇 |
1976年 | 7篇 |
1965年 | 13篇 |
1963年 | 9篇 |
1955年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
动筛跳汰系统设计中若干环节的探讨 总被引:1,自引:0,他引:1
论述了动筛跳汰机的选型原则及技术要求,提出了4m2动筛跳汰机分选系统设计中各环节技术参数及所用设备的选择条件,同时对动筛跳汰系统各环节的布置进行了探讨。 相似文献
32.
Ozone transfer to water or wastewater is necessary before desirable, effective ozone reactions occur. Several factors affect ozone transfer efficiency, including water quality characteristics, contactor configuration, and applied ozone characteristics. The design model presented in this paper addresses all factors affecting ozone transfer. The model was used to compare measured transfer efficiency with predicted transfer efficiency at four full-scale wastewater ozone disinfection facilities. A relatively good prediction was obtained at each plant.
The paper presents an example calculation of ozone transfer efficiency. Also, the effect of changes to some of the factors affecting transfer efficiency is presented, such as changes in diffuser depth, plant elevation, ozone concentration, water quality (i.e., ozone demand), pH, detention time, temperature, and acombination of factors. The design model may be used to evaluate the effect of changes in plant design on transfer efficiency, but cannot provide an absolute value for transfer efficiency until difficult-to-measure parameters, such as bubble diameter, are known. 相似文献
33.
Summary Elastomeric networks of polydimethylsiloxane prepared by end-linking chains having molecular weights in the range 18,500 to
220 g mol-1 were studied from -128 to 50°C using a Rheovibron DDV III Viscoelastometer. In the case of the unimodal networks, the glass
transition temperature Tg was generally insensitive to degree of cross-linking. The intensity of the tan δ relaxation, however, increased by over an
order of magnitude over the range of cross-link densities investigated. Bimodal networks prepared from mixtures of relatively
long and very short PDMS chains also had values of Tg which were insensitive to degree of cross-linking. Finally, as expected, the intensities of the tan δ peak for the bimodal
networks could not be explained on the basis of simple additivity of contributions from the relatively long and the very short
network chains. 相似文献
34.
To overcome the limitations of traditional monitoring methods, based on vibration parameter image of rotating machinery, this paper presents an abnormality online monitoring method suitable for rotating machinery using the negative selection mechanism of biology immune system. This method uses techniques of biology clone and learning mechanism to improve the negative selection algorithm to generate detectors possessing different monitoring radius, covers the abnormality space effectively, and avoids such problems as the low efficiency of generating detectors, etc. The result of an example applying the presented monitoring method shows that this method can solve the difficulty of obtaining fault samples preferably and extract the turbine state character effectively, it also can detect abnormality by causing various fault of the turbine and obtain the degree of abnormality accurately. The exact monitoring precision of abnormality indicates that this method is feasible and has better on-line quality, accuracy and robustness. 相似文献
35.
模糊综合评价方法在桥型多方案选择中的应用 总被引:1,自引:1,他引:0
为了解决现阶段桥型多方案选择中过多依赖设计者经验,而不可避免的带来主观性与片面性的问题.针对桥型方案选择的多因素与模糊性特征,提出了模糊综合评价方法在桥型多方案选择中的应用,确定了影响桥梁选型的指标体系,介绍了该方法的应用模型与步骤,并结合实例详细介绍了这种方法的应用过程.结果验证了这一方法的简明性和实用性.有利于减少桥梁型式选择的失误,提高其客观性与合理性,以得出最佳方案. 相似文献
36.
混合匹配规则的否定选择算法 总被引:1,自引:0,他引:1
针对目前基于免疫的检测器生成算法中,匹配规则单一造成的检测器质量低下的问题,提出一种基于混合匹配规则的否定选择算法,采用海明距离整体匹配的各段内R连续比特匹配的否定选择算法,即混合匹配否定选择算法,对算法的性能进行了分析.实验结果表明,该算法能够高效地产生所需要的检测器,提高了检测率,且降低了误报率. 相似文献
37.
38.
通过对我国维纶和腈纶建设模式(统一工艺技术、分散布点、同步建设)的回顾,认为化纤工业技术密集、投资风险大,国家应进行强有力的宏观调控,优先发展性能优良、节省资源、能源,并对环境污染较轻、有发展潜力的品种。选用引进技术设备要可靠、先进,并适合国情。对没有十足把握的技术设备,应试点后,再进行大规模建设。为减少损失,对国产化设备要通过实践考核后再推广使用。 相似文献
39.
Shaohui Mei Genliang Guan Zhiyong Wang Shuai Wan Mingyi He David Dagan Feng 《Pattern recognition》2015
The rapid growth of video data demands both effective and efficient video summarization methods so that users are empowered to quickly browse and comprehend a large amount of video content. In this paper, we formulate the video summarization task with a novel minimum sparse reconstruction (MSR) problem. That is, the original video sequence can be best reconstructed with as few selected keyframes as possible. Different from the recently proposed convex relaxation based sparse dictionary selection method, our proposed method utilizes the true sparse constraint L0 norm, instead of the relaxed constraint L2,1 norm, such that keyframes are directly selected as a sparse dictionary that can well reconstruct all the video frames. An on-line version is further developed owing to the real-time efficiency of the proposed MSR principle. In addition, a percentage of reconstruction (POR) criterion is proposed to intuitively guide users in obtaining a summary with an appropriate length. Experimental results on two benchmark datasets with various types of videos demonstrate that the proposed methods outperform the state of the art. 相似文献
40.
Response time (RT) of Networked Automation Systems (NAS) is affected by timing imperfections induced due to the network, computing and hardware components. Guaranteeing RT in the presence of such timing imperfections is essential for building dependable NAS, and to avoid costly upgrades after deployment in industries.This investigation proposes a methodology and work-flow that combines modelling, simulation, verification, experiments, and software tools to verify the RT of the NAS during the design, rather than after deployment. The RT evaluation work-flow has three phases: model building, modelling and verification. During the model building phase component reaction times are specified and their timing performance is measured by combining experiments with simulation. During the modelling phase, component based mathematical models that capture the network architecture and inter-connection are proposed. Composition of the component models gives the NAS model required for studying the RT performance on system level. Finally, in the verification step, the NAS formal models are abstracted as UPPAAL timed automata with their timing interfaces. To model timing interfaces, the action patterns, and their timing wrapper are proposed. The formal model of high level of abstraction is used to verify the total response time of the NAS where the reactions to be verified are specified using a subset of timed computation tree logic (TCTL) in UPPAAL model checker. The proposed approach is illustrated on an industrial steam boiler deployment. 相似文献