全文获取类型
收费全文 | 4766篇 |
免费 | 144篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 69篇 |
综合类 | 35篇 |
化学工业 | 1452篇 |
金属工艺 | 126篇 |
机械仪表 | 91篇 |
建筑科学 | 273篇 |
矿业工程 | 8篇 |
能源动力 | 81篇 |
轻工业 | 366篇 |
水利工程 | 27篇 |
石油天然气 | 2篇 |
无线电 | 283篇 |
一般工业技术 | 899篇 |
冶金工业 | 648篇 |
原子能技术 | 40篇 |
自动化技术 | 521篇 |
出版年
2022年 | 57篇 |
2021年 | 65篇 |
2020年 | 54篇 |
2019年 | 69篇 |
2018年 | 73篇 |
2017年 | 58篇 |
2016年 | 101篇 |
2015年 | 87篇 |
2014年 | 119篇 |
2013年 | 224篇 |
2012年 | 184篇 |
2011年 | 286篇 |
2010年 | 196篇 |
2009年 | 178篇 |
2008年 | 210篇 |
2007年 | 195篇 |
2006年 | 148篇 |
2005年 | 167篇 |
2004年 | 140篇 |
2003年 | 112篇 |
2002年 | 93篇 |
2001年 | 100篇 |
2000年 | 96篇 |
1999年 | 100篇 |
1998年 | 128篇 |
1997年 | 93篇 |
1996年 | 80篇 |
1995年 | 81篇 |
1994年 | 74篇 |
1993年 | 81篇 |
1992年 | 75篇 |
1991年 | 52篇 |
1990年 | 78篇 |
1989年 | 48篇 |
1988年 | 49篇 |
1987年 | 57篇 |
1986年 | 43篇 |
1985年 | 64篇 |
1984年 | 55篇 |
1983年 | 48篇 |
1982年 | 52篇 |
1981年 | 48篇 |
1979年 | 45篇 |
1978年 | 44篇 |
1977年 | 67篇 |
1976年 | 46篇 |
1975年 | 43篇 |
1974年 | 58篇 |
1972年 | 45篇 |
1970年 | 41篇 |
排序方式: 共有4921条查询结果,搜索用时 0 毫秒
31.
Alexandre N. Tuch Eva E. Presslaber Markus Stöcklin Klaus Opwis Javier A. Bargas-Avila 《International journal of human-computer studies》2012,70(11):794-811
This paper experimentally investigates the role of visual complexity (VC) and prototypicality (PT) as design factors of websites, shaping users' first impressions by means of two studies. In the first study, 119 screenshots of real websites varying in VC (low vs. medium vs. high) and PT (low vs. high) were rated on perceived aesthetics. Screenshot presentation time was varied as a between-subject factor (50 ms vs. 500 ms vs. 1000 ms). Results reveal that VC and PT affect participants' aesthetics ratings within the first 50 ms of exposure. In the second study presentation times were shortened to 17, 33 and 50 ms. Results suggest that VC and PT affect aesthetic perception even within 17 ms, though the effect of PT is less pronounced than the one of VC. With increasing presentation time the effect of PT becomes as influential as the VC effect. This supports the reasoning of the information-processing stage model of aesthetic processing (Leder et al., 2004), where VC is processed at an earlier stage than PT. Overall, websites with low VC and high PT were perceived as highly appealing. 相似文献
32.
33.
This paper reports on experimental results of aqueous heterophase polymerizations with monomers of quite different solubility in water ranging from the water-soluble 2-hydroxyethyl methacrylate to lauryl methacrylate with solubility in water of only about 10−4 mM. A calorimetric study revealed the strong influence of both the hydrophilicity of the monomer and the stirrer speed on the rate of polymerization in the absence of surfactants. In order to obtain maximum latex yield and high efficiency (which is a measure considering colloidal properties, polymerization recipe, and polymerization parameters) the initiator-surfactant combination must be properly chosen in dependence on the hydrophilicity of the monomer. Results are presented for sodium alkyl sulfates or disodium-N-stearoyl-l-glutamate as surfactant and potassium peroxodisulfate, or poly(ethylene glycol)-azo- compounds, or 2,2′-azobis(N-2′-methylpropanoyl-2-amino-alkyl-1)-sulfonates as initiators. 相似文献
34.
35.
The removal of soluble components from an ovine hepatic microsomal preparation decreased the ω-hydroxylation of dodecanoic
and hexadecanoic acids. The results suggest that one or more soluble components play a role in the microsomal ω-hydroxylation
of fatty acids. The possible roles in the reaction of catalase (known to stimulate the microsomal desaturations of fatty acids
and alkylglycerols) and superoxide dismutase were investigated. The addition of these enzymes to the complete (but not the
washed) microsomal preparation stimulated both the initial ω-hydroxylation reaction and the subsequent dehydrogenation reactions
of the ω-oxidation pathway. The similarity of the effects of catalase and superoxide dismutase and stimulation of two different
steps of the ω-oxidation pathway suggest that these agents are acting indirectly by removing active oxygen species rather
than directly on the enzymes of microsomal fatty acid ω-hydroxylation. 相似文献
36.
The heterogeneous bulk polymerization of acrylonitrile initiated by AIBN has been studied by means of an improved dilatometric technique and a new method of analysis, where the initial reaction rate (vw)0 results from the intercept of a straight line in a \documentclass{article}\pagestyle{empty}\begin{document}$ \frac {\ln \left( 1 \hbox{---} {\rm U} \right)} {{\rm e}^{{- 0,5} {\rm k}_{\rm s}{\rm t} \hbox{---} 1}}$\end{document} versus t plot. It has been found that the initial reaction rate is proportional to the square root of the initial catalyst concentration S0. The ratio of the rate coefficients of propagation and termination\documentclass{article}\pagestyle{empty}\begin{document}$\frac { {\rm k}_{\rm a} } { {\rm k}_{ {\rm w}^{2} } } $\end{document} could be calculated from the slope of a straight line passing through the origin in a plot of (vw)0 versus \documentclass{article}\pagestyle{empty}\begin{document}$\sqrt { {\rm S}_{0} }$\end{document} and yielded a value of 280 mol 1?1. 相似文献
37.
38.
Summary Novel organic nanoparticles functionalized with nucleophilic polypropyleneoxide (PPO) chains on their surfaces for supporting metallocene catalysts in heterogeneous olefin polymerization are presented. The nanoparticles (60–100 nm) were obtained by miniemulsion polymerization of styrene, divinylbenzene and PPO functionalized styrene. It is demonstrated that Me2Si(2MeBenzlnd)2ZrCl2/MAO supported on these nanoparticles is suitable for the homopolymerization of ethylene, resulting in excellent product morphologies and high activities. lt is shown that by varying the MAO/Zr ratios and Zr concentrations the activities and productivities of the catalysts as well as the qualities of the polyethylene products can be tuned. These new supported catalysts are also suitable for the copolymerization of ethylene with several comonomers (1-hexene, 1-octene, 1-decene or norbornene). As the obtained product properties like crystallinity, melting temperature or bulk density match the results of silica supported systems, these organic nanoparticles can be considered as alternative carriers in comparison to the established inorganic ones. 相似文献
39.
Klaus Trangbaek 《Asian journal of control》2014,16(1):40-49
This paper deals with system identification for control of linear parameter varying systems. In practical applications, it is often important to be able to identify small plant changes in an incremental manner without shutting down the system and/or disconnecting the controller; unfortunately, closed‐loop system identification is more difficult than open‐loop identification. In this paper we prove that the so‐called Hansen scheme, a technique known from linear time‐invariant systems theory for transforming closed‐loop system identification problems into open‐loop‐like problems, can be extended to accommodate linear parameter varying systems as well. We investigate the identified subsystem's parameter dependency and observe that, under mild assumptions, the identified subsystem is affine in the parameter vector. Various identification methods are compared in direct and Hansen Scheme setups in simulation studies, and the application of the Hansen Scheme is seen to improve the identification performance. 相似文献
40.