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排序方式: 共有93条查询结果,搜索用时 15 毫秒
51.
Mäkiranta MJ Jauhiainen JP Oikarinen JT Suominen K Tervonen O Alahuhta S Jäntti V 《Magma (New York, N.Y.)》2002,15(1-3):27-35
Deepening anesthesia produces well known changes in electroencephalogram (EEG) and evoked potentials, differing in pathological
and normal brain. Yet, it is not known how the T2*-weighted signal changes in the healthy brain during deepening anesthesia.
We studied the effect of thiopental bolus on functional magnetic resonance imaging (fMRI) in the healthy brain using porcine
model. In five pigs (2–3 months, 20–25 kg), the control bolus prior to fMRI resulted in a change into burst-suppression. After
the recovery of continuous EEG, fMRI (4 min) was performed with a single bolus of thiopental (11.4-17.1 mg/kg) administered
1 min after the onset of imaging. This was repeated in four of five pigs. Positive (6-8%) or negative (-3 to -8%) signal intensity
changes correlated to the thiopental bolus injection were seen in the group average fMRI response. Positive response was 1.6%
and negative response 2.3% of the total brain region of interest (ROI) voxels. Responding voxels were distributed more prominently
in the thalamic ROI (4.5%) than in the cortical ROI (2.2%). The group average of unthresholded voxel time courses showed that
the net effect of thiopental bolus was a small (0.5%) but a clear positive change in the thalamic region, while variance changed
in the global level. In conclusion, this study is the first to show that significant signal intensity changes occur in fMRI
response during the sudden deepening of thiopental anesthesia. However, these responses are neither anatomically constant
nor global in the healthy swine brain. 相似文献
52.
This paper presents a novel parallel memory architecture for multimedia computers. Applying a configurable or programmable addressing circuitry capable of parallel memory accesses, the memory management of multimedia applications can be enhanced. Necessary computer architecture changes to virtual address representation, paging, virtual memory, address computation circuitry and data permutation are discussed. These changes allow the memory to be partitioned for different access functions. In addition, the same memory area can be accessed by multiple access patterns. Therefore, a general-purpose computing system that is capable of exploiting the repeating memory access patterns in its applications can be built. Performance of the configurable parallel memory architecture (CPMA) is analyzed in the case of a selection of algorithms from a video encoder. These motion estimation algorithms and zigzag scanning benefit from the multiple memory access functions, which is apparent from the comparisons to the traditional sequential memory accesses. 相似文献
53.
A method for the calculation of the wavelength-dependent complex refractive index of absorbing liquid from reflectance in the vicinity of surface plasmon resonance (SPR) is presented. The calculation is based on the maximum entropy method (MEM). As an example, phase retrieval from a simulated SPR reflectance of a red colored liquid solution is carried out. It is proposed that MEM can be applied to wavelength-dependent complex refractive index assessment from reflectance of absorbing liquids in SPR measurement in wavelength scanning mode. 相似文献
54.
In future wireless networks, a mobile terminal will be able to communicate with a service provider using several network connections. These connections to networks will have different properties and they will be priced separately. In order to minimize the total communication time and the total transmission costs, an automatic method for selecting the network connections is needed. Here, we describe the network connection selection problem and formulate it mathematically. We discuss solving the problem and analyse different multiobjective optimization approaches for it. 相似文献
55.
Ruusunen M Puolanne E Sevon-Aimonen ML Partanen K Voutila L Niemi J 《Meat science》2012,90(3):543-547
The study compared properties of Finnish Landrace × Yorkshire crossbred sows mated with Finnish Landrace (FL), Norwegian Landrace (NL), Norwegian Duroc × Norwegian Landrace (NDL), or Swedish Hampshire (SH) boars. The focus was to study the cross-sectional area of loin, cross-sectional area and number of muscle fibres, loin colour and pH value as well as the ratio of water to protein in the loin.The four studied crosses were quite similar having only small differences in carcass and meat quality. The carcass lean content was the lowest in NDL. The loins of FL and NL were longer than the loins of NDL and of SH. The cross-sectional area of loin was the largest in SH. The loin of FL was lighter in colour and the loin of SH was redder than the loins of the other crosses studied. The protein content was lower and the ratio of water to protein higher in loin of SH than in the other crosses. 相似文献
56.
Thanh T. Nguyen Thanh N. Tran Tofan A. Willemsz Henderik W. Frijlink Tuomas Ervasti Jarkko Ketolainen Kees van der Voort Maarschalk 《Chemical engineering science》2011,(24):6385
The coordination number is an important parameter for understanding the particulate systems, especially when agglomerated particles are present. However, experimental determination of the coordination number is not trivial. In this study, we describe a 3D classification method, which is based on the revised DBSCAN (Density-Based Spatial Clustering of Applications with Noise) and its application to X-ray micro-tomographic (XMT) images to determine the coordination number distribution. Pellets of micro-crystalline cellulose were used as model particles. The validity of the segmentation was checked by comparing the particle size distribution (PSD) obtained by XMT-DBSCAN with PSD obtained by optical microscopy. The results were found to be in good agreement, demonstrating the suitability of the DBSCAN method. The means and standard deviations of coordination numbers were (8.2±1.7, n=994 particles), (8.1±1.5, n=904) and (6.2±1.2, n=159) for pellets with length based mean sizes of 157, 307 and 437 μm, respectively. The coordination number distribution was in line with previous finding in mono-sized acrylic beads. 相似文献
57.
Branislav Igic Kim Braganza Margaret M. Hyland Heather Silyn-Roberts Phillip Cassey Tomas Grim Jarkko Rutila Csaba Moskát Mark E. Hauber 《Journal of the Royal Society Interface》2011,8(64):1654-1664
Obligate brood parasitic birds lay their eggs in nests of other species and parasite eggs typically have evolved greater structural strength relative to host eggs. Increased mechanical strength of the parasite eggshell is an adaptation that can interfere with puncture ejection behaviours of discriminating hosts. We investigated whether hardness of eggshells is related to differences between physical and chemical traits from three different races of the parasitic common cuckoo Cuculus canorus, and their respective hosts. Using tools developed for materials science, we discovered a novel correlate of increased strength of parasite eggs: the common cuckoo''s egg exhibits a greater microhardness, especially in the inner region of the shell matrix, relative to its host and sympatric non-host species. We then tested predictions of four potential mechanisms of shell strength: (i) increased relative thickness overall, (ii) greater proportion of the structurally harder shell layers, (iii) higher concentration of inorganic components in the shell matrix, and (iv) elevated deposition of a high density compound, MgCO3, in the shell matrix. We confirmed support only for hypothesis (i). Eggshell characteristics did not differ between parasite eggs sampled from different host nests in distant geographical sites, suggesting an evolutionarily shared microstructural mechanism of stronger parasite eggshells across diverse host-races of brood parasitic cuckoos. 相似文献
58.
Jarkko Bamberg 《Planning Theory & Practice》2013,14(1):39-56
Online discussion with spatial annotations has been proposed as a method of facilitating public participation in spatial planning. It has been assumed that it will widen the knowledge base behind decisions by bringing local, first-hand knowledge into planning. However, what type of knowledge will be generated by such a geographically referenced public discussion in the planning process? This article addresses this question by tracing how an online discussion that allowed spatial annotations was implemented in a real-life land-use planning process in Tampere, Finland. The analysis focuses on two distinct phases of knowledge production. First, discussion focuses on how establishing this particular technology as a public forum impacts on the type of knowledge that is provided by the participants. The second part of the study addresses how planners assimilate information from geo-referenced public discussion. The article suggests that the interplay between (1) the site of knowledge production that was at the same time the arena of public discussion, (2) the issues that were deemed necessary to be cared for publicly, and (3) the people who were willing and able to enter the public arena and address issues in the way that the public arena afforded was crucial in shaping the type of knowledge that was generated. Furthermore, the results suggest that the constraints set by the local planning procedures and practical work of planners effectively guide the transformation of this knowledge into the domain of planning. The article starts to unravel contingencies of knowledge production related to public participation methods which use online discussion and spatial annotations. 相似文献
59.
The regression problem of modeling several response variables using the same set of input variables is considered. The model is linearly parameterized and the parameters are estimated by minimizing the error sum of squares subject to a sparsity constraint. The constraint has the effect of eliminating useless inputs and constraining the parameters of the remaining inputs in the model. Two algorithms for solving the resulting convex cone programming problem are proposed. The first algorithm gives a pointwise solution, while the second one computes the entire path of solutions as a function of the constraint parameter. Based on experiments with real data sets, the proposed method has a similar performance to existing methods. In simulation experiments, the proposed method is competitive both in terms of prediction accuracy and correctness of input selection. The advantages become more apparent when many correlated inputs are available for model construction. 相似文献
60.
Adriana Ferancová Maarit K. Hattuniemi Adama M. Sesay Jarkko P. Räty Vesa T. Virtanen 《Mine Water and the Environment》2017,36(2):273-282
The complexation of Ni(II) with dimethylglyoxime (DMG) entrapped within a Nafion membrane and a DMG–sol–gel matrix was studied and compared for different solutions. First and pseudo-second order kinetic models, Elovich, intra-particle, and liquid film diffusion models were applied to evaluate sorption kinetics. Complexation of Ni(II) by DMG entrapped in the polymeric materials followed a pseudo-second order kinetic model; moreover, DMG in Nafion also allowed diffusion-controlled uptake. The pseudo-second order rate constant was significantly higher for the free ligand in solution than for Ni(II) accumulation in the surface-attached DMG-Nafion. The DMG–sol–gel removal ability of Ni(II) was tested using actual mine water. The presence of interferences only insignificantly decreased the removal percentage of Ni(II), thus confirming the high selectivity of DMG towards Ni(II). Also, an electrochemical sensor modified with DMG in Nafion was investigated further for direct electrochemical determination of Ni(II) in untreated mine water. Determination errors and interference effects were low. Thus, this approach represents an effective potential solution for selective Ni(II) removal from mine water as well as a rapid and cheap sensor for on-site monitoring of Ni(II) in mine and environmental waters. 相似文献