全文获取类型
收费全文 | 3190篇 |
免费 | 191篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 37篇 |
化学工业 | 831篇 |
金属工艺 | 122篇 |
机械仪表 | 82篇 |
建筑科学 | 77篇 |
矿业工程 | 16篇 |
能源动力 | 124篇 |
轻工业 | 523篇 |
水利工程 | 24篇 |
石油天然气 | 8篇 |
无线电 | 160篇 |
一般工业技术 | 740篇 |
冶金工业 | 40篇 |
原子能技术 | 49篇 |
自动化技术 | 550篇 |
出版年
2024年 | 11篇 |
2023年 | 39篇 |
2022年 | 39篇 |
2021年 | 97篇 |
2020年 | 84篇 |
2019年 | 108篇 |
2018年 | 162篇 |
2017年 | 152篇 |
2016年 | 151篇 |
2015年 | 140篇 |
2014年 | 187篇 |
2013年 | 379篇 |
2012年 | 192篇 |
2011年 | 239篇 |
2010年 | 242篇 |
2009年 | 175篇 |
2008年 | 113篇 |
2007年 | 83篇 |
2006年 | 51篇 |
2005年 | 13篇 |
2004年 | 29篇 |
2003年 | 26篇 |
2002年 | 35篇 |
2001年 | 26篇 |
2000年 | 36篇 |
1999年 | 19篇 |
1998年 | 20篇 |
1997年 | 20篇 |
1996年 | 17篇 |
1995年 | 22篇 |
1994年 | 18篇 |
1993年 | 26篇 |
1992年 | 20篇 |
1991年 | 14篇 |
1990年 | 12篇 |
1989年 | 14篇 |
1988年 | 14篇 |
1985年 | 19篇 |
1984年 | 24篇 |
1983年 | 21篇 |
1982年 | 22篇 |
1981年 | 37篇 |
1980年 | 26篇 |
1979年 | 24篇 |
1978年 | 23篇 |
1977年 | 21篇 |
1976年 | 32篇 |
1975年 | 23篇 |
1974年 | 16篇 |
1973年 | 22篇 |
排序方式: 共有3383条查询结果,搜索用时 13 毫秒
21.
The specifics of business intelligence systems compared to operational IS motivate the necessity to research the business intelligence systems acceptance determinants separately. The authors followed an exploratory approach in order to conceptualize a business intelligence acceptance model. Their findings show that in the Business Intelligence Systems context, there is a significant emphasis on organizational factors, such as result demonstrability, social influence, and facilitating conditions with sufficient resources that help build an adequate information culture all substantially influencing the effective acceptance of business intelligence systems. 相似文献
22.
Knowing the estimation of a statistical process’s parameters for measured network traffic is very important as it can then be further used for the statistical analyses and modeling of network traffic in simulation tools. It is for this reason that different estimation methods are proposed that allow estimations of the statistical processes of network traffic. One of them is our own histograms comparison (EMHC) based method that can be used to estimate statistical data-length process parameters from measured packet traffic. The main part of EMHC method is Mapping Algorithm with Fragmentation Mimics (MAFM). 相似文献
23.
Andrew Morrison Geska Helena Andersson Robert Brečević Synne Skjulstad 《Digital Creativity》2013,24(1-2):3-20
The metaphor of plasma is taken up to present and discuss movement and engagement by participants in mixed reality installation arts. Two works involving full body video portraits exhibited through large plasma screens in a variety of public settings are covered. Machinic mediations of video realism are considered in terms of embodied interaction in which viewer-participants contribute to the ‘disquiet’ of gendered figuring. Processural, proximal and personal aspects of responsive engagement are discussed. This is extended to performativity that may lead us to critical reflection of our own actions and responses in mixed reality arts. 相似文献
24.
The flow stress of polycrystals is controlled by the processes occurring in the grain interior as well as in the mantle, i.e. at the grain boundary and its immediate vicinity. The early stages of evolution of dislocation substructure in these two regions with strain in 316L stainless steel polycrystals have been studied at 293 K, 673 K and 1123 K representing the low temperature thermal, the intermediate temperature athermal and the high temperature thermal regimes respectively. Specimens with grain sizes of 4 and 12 m were employed to determine the effect of grain size.Transmission electron microscopy studies on deformed specimens show the different roles of grain boundary and grain interior in different temperature regimes. In the low temperature regime grain boundaries act as obstacles to moving dislocations and as such high density of dislocation is found in the grain boundary vicinity. In the intermediate temperature regime the dislocations which are easily spread into the grain interior rearrange to form cell walls. In the high temperature regime grain boundaries transform to the equilibrium state and do not contain any grain boundary dislocations, and the distribution of dislocations within grains is homogeneous at all strains. Significantly higher values of dislocation densities in the vicinity as well as in the grain interior were found in the finer grain size material in the whole strain region employed. 相似文献
25.
26.
Copper–graphite composite materials in the range of 0–10 vol% of carbon phase were prepared from the mixture of copper and graphite powders by hot isostatic pressing. The microstructure, mechanical (tensile strength, elongation to fracture) and physical (electrical and thermal conductivity) properties of composite samples were investigated, and the cross-property connections were calculated. It was shown that electrical and thermal conductivity cross-property (Lorenz number) is almost constant and increases only slightly (no more than 10 % increase was observed). This implies that in the investigated composition range the Lorenz number of a copper–graphite composite system behaves according to Franz–Wiedemann law for pure metals at constant temperature. On the contrary, the conductivity to tensile strength cross-property connections showed significant linear increase (over 200 % in the investigated composition range) for both electrical conductivity and thermal conductivity of composite materials. The cross-property connections of conductivity to the elongation to fracture exhibit a nonlinear dependence on the volume fraction of graphite. 相似文献
27.
28.
This article represents the result of experimental research on transient heat transfer in a multilayered (heterogeneous) wall. Our non-steady thermal transmission simulation is based on a finite-difference calculation method. The value of a Fourier number shows the similarity of thermal variation in conditional layers of an enclosure. Most scientists recommend using no more than a value of 0.5 for the Fourier number when performing calculations on dynamic (transient) heat transfer. The value of the Fourier number is determined in order to acquire reliable calculation results with optimal accuracy. To compare the results of simulation with experimental research, a transient heat transfer calculation spreadsheet was created. Our research has shown that a Fourier number of around 0.5 or even 0.32 is not sufficient (\({\approx }17\,\%\) of oscillation amplitude) for calculations of transient heat transfer in a multilayered wall. The least distorted calculation results were obtained when the multilayered enclosure was divided into conditional layers with almost equal Fourier number values and when the value of the Fourier number was around 1/6, i.e., approximately 0.17. Statistical deviation analysis using the Statistical Analysis System was applied to assess the accuracy of the spreadsheet calculation and was developed on the basis of our established methodology. The mean and median absolute error as well as their confidence intervals has been estimated by the two methods with optimal accuracy (\({F}_{\mathrm{oMDF}}= 0.177\) and \(F_{\mathrm{oEPS}}= 0.1633\) values). 相似文献
29.
30.
In this paper we study a class of CQ Horn functions introduced in Boros et al. (Ann Math Artif Intell 57(3–4):249–291, 2010). We prove that given a CQ Horn function f, the maximal number of pairwise disjoint essential sets of implicates of f equals the minimum number of clauses in a CNF representing f. In other words, we prove that the maximum number of pairwise disjoint essential sets of implicates of f constitutes a tight lower bound on the size (the number of clauses) of any CNF representation of f. 相似文献