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排序方式: 共有843条查询结果,搜索用时 0 毫秒
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Henrik Andersson Arild Hoff Marielle Christiansen Geir Hasle Arne Løkketangen 《Computers & Operations Research》2010,37(9):1515-1536
This paper describes industrial aspects of combined inventory management and routing in maritime and road-based transportation, and gives a classification and comprehensive literature review of the current state of the research.The literature is contrasted with aspects of industrial applications from a constructive, but critical, viewpoint. Based on the status and trends within the field, future research is suggested with regard to both further development of the research area and industrial needs. By highlighting the industrial aspects, practitioners will hopefully see the benefit of using advanced decision support systems in complex situations related to combined inventory management and routing in their business. In addition, a classification and presentation of the research should help and motivate researchers to further focus on inventory management and routing challenges. 相似文献
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Ove Wolfgang Arne Haugstad Birger Mo Anders Gjelsvik Ivar Wangensteen Gerard Doorman 《Energy》2009,34(10):1642
The Norwegian Energy Act that came into force in 1991 deregulated the electricity market and removed the former obligation power companies had to supply electricity to the geographical area they were responsible for. Hence producers can supply electricity on the basis of profitability. In 2007 the Energy Act was evaluated by the Government. As a part of this, a study concerning hydro reservoir handling before and after deregulation was carried out by SINTEF. Public statistics show that average hydro reservoir levels measured in per cent of reservoir capacity have been reduced after 1990. We have used the power-market model EMPS1 (EFI's Multi-area Power-market Simulator) to analyze if this reduction can be explained by natural variation in climatic variables or by structural changes that have occurred after 1990. Simulation results show that the reduced reservoir levels cannot be explained by natural variation in climatic variables. Structural changes such as increased transmission capacities can, however, explain some of the reduction. Our study does not indicate that the present reservoir handling gives reservoir levels that are too low. In this paper we also describe the stochastic dynamic optimization problem for long-term hydropower scheduling, and we explain how this problem actually is solved by the EMPS model. 相似文献
47.
Most lipid extraction procedures [Folch, J., Lees, M., and Sloane-Stanley, G.H., (1957) A Simple Method for the Isolation
and Purification of Total Lipids from Animal Tissues, J. Biol. Chem. 226, 497–509; Bligh, E.G., and Dyer, W.J. (1959) A Rapid Method of Total Lipid Extraction and Purification, Can. J. Biochem. Physiol. 37, 911–917] employ biphasic solvent mixtures designed to dissolve the lipids in an organic phase and remove impurities in an
aqueous phase. However, when applying these protocols to biological matrices such as that of the ocular lens, the formation
of an emulsion layer between the organic and aqueous phases causes poor reproducibility in extraction yields and gives only
a small amount of the lipid-containing chloroform phase. In this study, we quantified phospholipids at each step of the Folch
et al. extraction protocol and compared the yield of human and bovine lens phospholipids obtained by the Folch-based approach and
a novel monophasic methanol extraction method designed to circumvent the problems associated with biphasic extraction protocols.
A monophasic methanol extraction coupled with 31P NMR spectroscopy was found to be the simplest, quickest, and most effective method for quantifying the phospholipid content
of the lens. 相似文献
48.
The commercial software used for predicting fatigue strength for load‐carrying spot welds in sheet structures, like car bodies, is mainly developed for two‐sheet joints. The purpose of this work was to study the fatigue properties of three‐sheet spot welded joints with a dimensioning method used in the automotive industry and to compare such computational results to those obtained from a more accurate method and to experimental data. Eleven three‐sheet, single spot welded specimens were studied using a structural stress approach, followed by shell element simulations, similar to those used in commercial software. These results were compared to calculations based on fine meshed solid element models. Fracture mechanics was used to evaluate the loading conditions at the spot welds. Comparison between the results from the different methods and experimental results for three shear loaded specimens, consisting of triple sheets, found in literature showed good correlation. The shell element method in shear loaded cases gives stress intensities within +35% to ‐5% of the solid element method results. In peel loaded cases the results differ up to ‐60%, an under‐estimation that leads to an increase of estimated fatigue life up to 65 times. 相似文献
49.
The bandwidth minimization problem has a long history and a number of practical applications.
In this paper we introduce a natural extension of bandwidth to partially ordered layouts.
We consider this extension from three main viewpoints: graph searching,
tree decompositions, and elimination orderings.
The three graph parameters pathwidth, profile, and bandwidth related to linear layouts
can be defined by variants of graph searching using a standard fugitive.
Switching to an inert fugitive, the two former parameters are extended to
treewidth and fill-in, and our first viewpoint considers the
analogous tree-like extension that arises from the bandwidth variant.
Bandwidth also has a definition in terms of ordered path decompositions,
and our second viewpoint extends this in a natural way to ordered
tree decompositions.
In showing that both extensions are equivalent we employ the third viewpoint of
elimination trees, as used in the field of sparse matrix computations.
We call the resulting parameter the treespan of a graph and
prove some of its combinatorial and algorithmic properties. 相似文献
50.
Active centers, catalytic behavior, symbiosis and redox properties of MoV(Nb,Ta)TeO ammoxidation catalysts 总被引:1,自引:0,他引:1
Robert K. Grasselli Douglas J. Buttrey James D. Burrington Arne Andersson Johan Holmberg Wataru Ueda Jun Kubo Claus G. Lugmair Anthony F. Volpe Jr 《Topics in Catalysis》2006,38(1-3):7-16
Selective as well as waste forming active centers were defined for MoVNbTeO and MoVTaTeO catalysts in the ammoxidation of
propane to acrylonitrile and all catalytic functionalities were assigned to specific elements at the respective active centers.
Symbiosis between M1 and M2 phases of these catalysts was observed, with phase cooperation being more extensive in the Nb than Ta containing compositions.
The difference in catalytic effectiveness arises most likely because contact and surface area exposure of the two respective,
cooperating phase pairs are not equal. The M1 phase of the catalysts is reducible by propane and ammonia in the absence of dioxygen and is regenerable to its original,
fully oxidized state by dioxygen (air). No structural collapse is observed even after 120 C3H8 + NH3 reduction pulses. The so induced reduction of the catalyst extends up to 70 layers deep. The product distribution over the
first few pulses is very similar to that under catalytic conditions, supporting the concept that lattice oxygen is involved
in the catalytic ammoxidation process. Therefore, the ammoxidation of paraffins is a redox process, as is of course the well-known
olefin ammoxidation process. 相似文献