全文获取类型
收费全文 | 490篇 |
免费 | 12篇 |
专业分类
电工技术 | 3篇 |
综合类 | 1篇 |
化学工业 | 56篇 |
金属工艺 | 10篇 |
机械仪表 | 6篇 |
建筑科学 | 8篇 |
矿业工程 | 1篇 |
能源动力 | 11篇 |
轻工业 | 66篇 |
水利工程 | 1篇 |
石油天然气 | 2篇 |
无线电 | 54篇 |
一般工业技术 | 59篇 |
冶金工业 | 176篇 |
原子能技术 | 1篇 |
自动化技术 | 47篇 |
出版年
2023年 | 3篇 |
2021年 | 7篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 8篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 5篇 |
2014年 | 6篇 |
2013年 | 18篇 |
2012年 | 17篇 |
2011年 | 28篇 |
2010年 | 18篇 |
2009年 | 27篇 |
2008年 | 24篇 |
2007年 | 12篇 |
2006年 | 27篇 |
2005年 | 14篇 |
2004年 | 16篇 |
2003年 | 16篇 |
2002年 | 13篇 |
2001年 | 16篇 |
2000年 | 18篇 |
1999年 | 13篇 |
1998年 | 17篇 |
1997年 | 19篇 |
1996年 | 7篇 |
1995年 | 4篇 |
1994年 | 14篇 |
1993年 | 8篇 |
1992年 | 3篇 |
1991年 | 7篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 6篇 |
1973年 | 3篇 |
1972年 | 4篇 |
1970年 | 5篇 |
1963年 | 5篇 |
排序方式: 共有502条查询结果,搜索用时 15 毫秒
1.
This paper analyses the HIPERLAN channel access mechanism. Both a purely mathematical and a simulation model are built in order to evaluate the two successive phases of the contention scheme. Several optimisations, based on the choice of parametric values, are proposed, evaluated and compared. 相似文献
2.
3.
4.
Conventional random access memories are capable only of writing data into and reading data from the storage location corresponding to a given address. The availability of VLSI circuits containing hundreds of thousands of switching devices, however, has recently made practical the implementation of active memory chips capable of performing a range of complex operations on their stored data. Such designs are characterized by the extensive intermingling of processing and memory resources within a single chip to achieve the rapid and cost-effective parallel execution of operations relevant to such tasks as image processing, computer graphics, artificial intelligence, and database management.This paper presents a brief survey of a number of active memory chips that have been implemented or proposed, along with a more detailed examination of a particular active memory circuit, the NON-VON 3 primary processing subsystem chip.This research was supported in part by the Defense Advanced Research Projects Agency, under contract N00039-84-C-0165, in part by the New York Center for Advanced Technology in Computers and Information Systems at Columbia University, and in part by an IBM Faculty Development Award. 相似文献
5.
Elastomer materials are used in a wide application range and subjected to different loading from which failure of the material results. Because this failure is caused by initiation and propagation of cracks, the application of fracture mechanics methods for the assessment of the material is obvious. A short summary of the methods of technical fracture mechanics including possibilities of determination of crack resistance curves is given. Vulcanizates on the basis of SBR 1500 with various sulfur and carbon black contents were investigated. For describing the crack initiation and crack propagation behavior, several fracture mechanics examination methods were applied. Tear‐analyzer results were used to assess the crack propagation behavior under fatigue‐like loading conditions. Furthermore, for the characterization of the crack resistance of the materials under impact‐like loading conditions, instrumented tensile‐impact tests were performed. To obtain information about the initiation and propagation of a stable crack, quasi‐static fracture mechanics tests were applied. The results of the several tests are discussed in dependence on sulfur and carbon black contents. We found a non‐monotonous behavior of the toughness as a function of carbon black loading. An explanation is given in connection with a percolation‐like transition in filler morphology on larger length scales.
6.
The electrochemistry of VS2 in molten NaAlCl4 has been investigated in relation to its usefulness as a reversible positive electrode for sodium batteries operating in the moderate temperature range of 160–200°C. VS2 reacted with NaAlCl4 during early stages of cell cycling, and became VS2Cl showing a reversible capacity of 2.8 electrons/vanadium. The electrochemistry of mixtures of VCl3 and S in molten NaAlCl4 showed similarities to that of VS2Cl. The VSxCly cathodes obtained via the two different routes exhibited excellent rechargeability as evidenced by the long-term cycling behavior of cells of the configuration, Na(l)/β″-Al2O3/NaAlCl4(l), cathode material. When NbS2Cl2 was used as the cathode material it underwent a structural change in the first cycle to form what appeared to be NbS2Cl2, the Nb analog of VSxCly. The structurally modified niobium sulfur chloride cathode exhibited excellent rechargeability. 相似文献
7.
Roberto J. de Antueno Richard C. Cantrill Yung-Sheng Huang Michele Elliot David F. Horrobin 《Lipids》1993,28(4):285-290
This study was undertaken to investigate the total plasma fatty acid composition and the relationship between plasma triacylglycerol
(TG) levels and liver Δ9 desaturase activity in mice fed n−3 and/or n−6 fatty acid or hydrogenated coconut oil (HCO) (maximum
25 mg/g) supplemented diets. Generally, plasma TG levels and Δ9 desaturase activity were inversely correlated with the ratio
of the sum of long chain n−3 fatty acids to 18∶2n−6 and to the ratio of the sum of long chain n−3 fatty acids to 18∶n−3, but
they were positively correlated with the ratio of products and substrates (18∶1/18∶0) of the enzyme in plasma total lipids.
The n−3 fatty acid (mainly 20∶5n−3) enriched diet, when compared to the HCO diet at 21 d, caused a significant reduction in
plasma TG levels but not in Δ9 desaturase activity. However, a marked reduction in plasma TG content (50–60%) and Δ9 desaturase
activity (55–70%) was observed when both 20∶5n−3 and 18∶3n−6 were supplemented in the diet. The plasma TG levels and Δ9 desaturase
activity rose again when the animals were fed the HCO diet or chow. The results suggest that low dose supplementation of a
mixture of n−3 (mainly 20∶5n−3) and n−6 (18∶3n−6) fatty acids modified both plasma TG content and liver Δ9 desaturase activity,
in parallel. 相似文献
8.
Assignment Games with Conflicts: Robust Price of Anarchy and Convergence Results via Semi-Smoothness
We study assignment games in which jobs select machines, and in which certain pairs of jobs may conflict, which is to say they may incur an additional cost when they are both assigned to the same machine, beyond that associated with the increase in load. Questions regarding such interactions apply beyond allocating jobs to machines: when people in a social network choose to align themselves with a group or party, they typically do so based upon not only the inherent quality of that group, but also who amongst their friends (or enemies) chooses that group as well. We show how semi-smoothness, a recently introduced generalization of smoothness, is necessary to find tight bounds on the robust price of anarchy, and thus on the quality of correlated and Nash equilibria, for several natural job-assignment games with interacting jobs. For most cases, our bounds on the robust price of anarchy are either exactly 2 or approach 2. We also prove new convergence results implied by semi-smoothness for our games. Finally we consider coalitional deviations, and prove results about the existence and quality of strong equilibrium. 相似文献
9.
'Grid cells' in the dorsocaudal medial entorhinal cortex (dMEC) are activated when a rat is located at any of the vertices of a grid of equilateral triangles covering the environment. dMEC grid cells have different frequencies and phase offsets. However, cells in the dentate gyrus (DG) and hippocampal area CA3 of the rodent typically display place fields, where individual cells are active over only a single portion of the space. In a model of the hippocampus, we have shown that the connectivity from the entorhinal cortex to the dentate granule cells could allow the dentate granule cells to operate as a competitive network to recode their inputs to produce sparse orthogonal representations, and this includes spatial pattern separation. In this paper we show that the same computational hypothesis can account for the mapping of EC grid cells to dentate place cells. We show that the learning in the competitive network is an important part of the way in which the mapping can be achieved. We further show that incorporation of a short term memory trace into the associative learning can help to produce the relatively broad place fields found in the hippocampus. 相似文献
10.
In this study, the complex hygrothermal behavior of two epoxy systems used for strengthening applications was studied. In these systems, property loss by plasticization simultaneously occurred with property gain during additional curing. A comparison of the changes in the glass-transition temperature (Tg) and crosslink density with water immersion at different temperatures clearly showed that the two effects of additional curing by a postcuring reaction and plasticization by water absorption were in competition with each other during the exposure. The changes in the conversion with different exposure conditions suggested that water accelerated the postcuring reaction, even at low temperatures; this resulted in a significant difference in the postcuring reaction between unexposed and exposed epoxies. The construction of the plot of Tg versus conversion for the unexposed system and the placement of the Tg for exposed systems onto this master plot provided a method for evaluating the plasticization effect while excluding the influence of additional curing. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献