全文获取类型
收费全文 | 47510篇 |
免费 | 6700篇 |
国内免费 | 5078篇 |
专业分类
电工技术 | 7317篇 |
技术理论 | 4篇 |
综合类 | 7445篇 |
化学工业 | 3213篇 |
金属工艺 | 1260篇 |
机械仪表 | 3753篇 |
建筑科学 | 2324篇 |
矿业工程 | 1528篇 |
能源动力 | 1386篇 |
轻工业 | 1301篇 |
水利工程 | 1293篇 |
石油天然气 | 1128篇 |
武器工业 | 811篇 |
无线电 | 4414篇 |
一般工业技术 | 3700篇 |
冶金工业 | 1089篇 |
原子能技术 | 363篇 |
自动化技术 | 16959篇 |
出版年
2024年 | 198篇 |
2023年 | 712篇 |
2022年 | 1021篇 |
2021年 | 1242篇 |
2020年 | 1623篇 |
2019年 | 1641篇 |
2018年 | 1406篇 |
2017年 | 1693篇 |
2016年 | 1909篇 |
2015年 | 1997篇 |
2014年 | 2805篇 |
2013年 | 3170篇 |
2012年 | 3300篇 |
2011年 | 3727篇 |
2010年 | 2756篇 |
2009年 | 2912篇 |
2008年 | 3063篇 |
2007年 | 3602篇 |
2006年 | 3354篇 |
2005年 | 2804篇 |
2004年 | 2313篇 |
2003年 | 2001篇 |
2002年 | 1726篇 |
2001年 | 1469篇 |
2000年 | 1294篇 |
1999年 | 1104篇 |
1998年 | 819篇 |
1997年 | 670篇 |
1996年 | 558篇 |
1995年 | 483篇 |
1994年 | 402篇 |
1993年 | 333篇 |
1992年 | 264篇 |
1991年 | 178篇 |
1990年 | 160篇 |
1989年 | 131篇 |
1988年 | 98篇 |
1987年 | 54篇 |
1986年 | 39篇 |
1985年 | 25篇 |
1984年 | 37篇 |
1983年 | 36篇 |
1982年 | 29篇 |
1981年 | 17篇 |
1980年 | 15篇 |
1979年 | 20篇 |
1978年 | 8篇 |
1977年 | 12篇 |
1960年 | 5篇 |
1959年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
介绍了采用模糊控制技术解决真空冻干生产线控制中大超调量、大滞后等问题的方法 ,详述了模糊控制系统的构成、主要功能和实现方法 相似文献
102.
针对烧结炉温度控制问题提出了一种简单实用的 Fuzzy PID控制方案 ,对智能烧结炉温度控制系统的构成和控制策略进行了详细的论述。并着重介绍了软件实现方法。实际应用表明 ,此控制方案具有速度快、精确度高、稳定可靠等特点 相似文献
103.
Paul J. Flory 《Polymer International》1985,17(2):96-102
The earliest investigations on rubber elasticity, commencing in the 19th century, were necessarily limited to phenomenological interpretations. The realisation that polymers consist of very long molecular chains. commencing c. 1930, gave impetus to the molecular theory of rubber elasticity (1932-). according to which the high deformability of an elastomer, and the elastic force generated by deformation, stem from the configurations accessible to long molecular chains. Theories of rubber elasticity put forward from 1934-1946 relied on the assumption that the junctions of the rubber network undergo displacements that are affine in macroscopic strain. The theory of James and Guth (1947) dispensed with this premise, and demonstrated instead that the mean positions of the junctions of a ‘phantom’ network consisting of Gaussian chains devoid of material properties are affine in the strain. The vital significance of the distinction between the actual distribution of chain vectors in a network and their distribution if the junctions would be fixed at their mean positions went unnoticed for nearly 30 years. Experimental investigations, commencing with the incisive work of Gee in 1946. revealed large departures from the relationship of stress to strain predicted by the theories cited. This discrepancy prompted extensive studies, theoretical and experimental, during succeeding years. Inquiry into the fundamentals of polymer networks, formed for example by interlinking very long polymer molecules, exposed the need to take account of network imperfections, typically consisting of chains attached at only one end to a network junction. Various means were advocated to make corrections for these imperfections. The cycle rank ζ of the network has been shown (1976) to be the fundamental measure of its connectivity, regardless of the junction functionality and pattern of imperfections. Often overlooked is the copious interpenetration of the chains comprising typical elastomeric networks. Theories that attempt to represent such networks on a lattice are incompatible with this universal feature. Moreover, the dense interpenetration of chains may limit the ability of junctions in real networks to accommodate the fluctuations envisaged in the theory of phantom networks. It was suggested in 1975 that departures from the form predicted for the elastic equation of state are due to constraints on the fluctuations of junctions whose effect diminishes with deformation and with dilation. Formulation of a self-consistent theory based on this suggestion required recognition of the non-affine connection between the chain vector distribution function and the macroscopic strain in a real network, which may partake of characteristics of a phantom network in some degree. Implementation of the idea was achieved through postulation of domains of constraint affecting the equilibrium distribution of fluctuations of network junctions from their mean positions. This led in due course to a theory that accounts for the relationship of stress to strain virtually throughout the ranges of strain accessible to measurement. The theory establishes connections between structure and elastic properties. This is achieved with utmost frugality in arbitrary parameters. 相似文献
104.
105.
106.
Inaki Arrazola Agn s Plainfoss Henri Prade Claudette Testemale 《Information Systems》1989,14(6):487-492
This paper presents different approaches which enable a data base management system to obtain a plausible fuzzy estimate for an attribute value of an item for which the information is not explicitly stored in the data base. This can be made either by a kind of analogical reasoning from information about particular items or by means of expert rules which specify the (fuzzy) sets of possible values of the attribute under consideration, for various classes of items. Another kind of expert rules enables the system to compute an estimate from the attribute value of another item provided that, in other respects, this latter item sufficiently resembles the item, the value of which we are interested in; then these expert rules are used either for controlling the analogical reasoning process or for enlarging the scope of application of the first kind of expert rules. The different approaches are discussed in the framework of possibility theory. 相似文献
107.
A. Blazevic H. G. Bohlen W. von Oertzen 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2002,190(1-4):64-68
We report on measurements of charge changing cross-sections and energy losses in dependence on the initial and final charge state of Ne ions at an incident energy of 2 MeV/u penetrating thin carbon foils. Different initial charge states could be separated in energy by applying a high voltage in front of the carbon foils; the final charges and their energy loss were measured with a high-resolution magnetic spectrometer. We derived a consistent evolution of the charge state distribution solving the corresponding rate equations for the measured cross-sections. Including the charge state dependent energy losses, ΔE(qi,qf), stopping power values for frozen charge states, S(q), could be extracted. The experimental data are compared with different theoretical predictions. 相似文献
108.
原油中含有大量的高分子有机固相物质,因此,要准确地描述油气体系相平衡,必须对气液固三相相平衡进行研究,在对高分子有机烃类沥青沉降机理有了一定的认识的基础上,提出了大的交互作用系数,可以描述沥青与原油中轻质不相容性的程度。根据对油气烃类混合物体系的一般性认识与提出的沥青组分特征化方法,导出了与之相应的有其自身特殊性的气液沥青三相相平衡物料平衡方程组,用考虑沥青沉降三相闪蒸数值算法,对沥青沉降进行有效的理化模拟计算,此外,结合实例分析,给出了沥青质参考逸度的计算,饱和压力和沉降量的拟合方法。 相似文献
109.
采用BP神经网络记忆模糊规则的控制 总被引:28,自引:0,他引:28
本文提供了一种比模糊推理更为自然的方式使用人们的经验知识,通过一组神经元不同
程度的兴奋表达一个抽象的概念值,由此将抽象的经验规则转化成多层神经网络的输入一输
出样本.通过Back-Propagation学习算法使得网络记忆这些样本.控制器以"联想记忆"方
式使用这些经验.本文介绍了控制器的构造方法,给出了控制仿真结果,并讨论了这种控制器
的特点和发展前途. 相似文献
110.
化工软测量技术研究进展 总被引:2,自引:0,他引:2
详细说明了软测量技术的含义以及软测量系统的组成。在此基础上,介绍了软测量技术中基于机理分析建模、应用状态观测器建模、应用统计分析建模、神经元网络、模糊技术、以及支持向量机的智能建模等软测量建模理论方法和最新研究成果,之后介绍了小波分析、推断控制算法在软测量数据处理中的应用,最后介绍了基于虚拟仪器开发平台的软测量系统实现技术。 相似文献