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Mika Kemppainen Iikka Virkkunen Jorma Pitknen Raimo Paussu Hannu Hnninen 《Nuclear Engineering and Design》2003,224(1):105-117
One of the key issues in in-service inspection qualification is the representativeness of the defects used in qualification specimens. The best representativeness is achieved with realistic defects. However, present specimen production techniques have some significant weaknesses, such as unrealistic defects or additional alterations induced in the surrounding material. Specimens manufactured, for example, by weld implantation or with weld solidification defects always result in one or more extra weld interfaces. These interfaces can be detected by NDT. To overcome problems with the current specimens, a new defect manufacturing technique was developed. The new technique produces natural, representative defects without introducing additional weld metal or other unwanted alterations to the specimen.The new method enables artificial production of single, separate fatigue cracks by thermal loading. The method is based on a natural thermal fatigue damage mechanism and enables production of real cracks directly into the samples. Cracks are produced without welding or machining and without any preliminary surface treatment or artificial initiator such as a notch or a precrack. Single crack or a network of cracks can be induced into the base material, welded areas, HAZ, weld claddings, threaded areas, T-joints, etc. The location, orientation and size of produced cracks can be accurately controlled. Produced cracks can be used to simulate different types of service-induced cracks such as thermal fatigue, mechanical fatigue and stress corrosion cracks. It is shown that artificially produced thermal fatigue cracks correspond well with the real, service-induced cracks and overcome the problems of traditional qualification specimen manufacturing techniques. 相似文献
3.
An experimental study was carried out on the AIBN-initiated polymerization of styrene at 60°C. The kinetic rate constants were determined by the method of moments and the MWD method, which was proposed in a previous paper. The results compared favorably with the data in the literature and the MWD method was noted to yield more consistent results than the method of moments, which indicates the importance of considering the whole molecular weight distribution. The theoretical MWD was found to approximate the experimental MWD well. The chain-transfer constant to AIBN was found to be between 0.09 and 0.14. 相似文献
4.
We consider the load balancing problem in large wireless multi-hop networks by applying the continuum approximation. The task is to find routes, geometric curves, such that the maximal traffic load in the network is minimized. In finite fixed networks, multi-path routes generally yield a lower congestion and thus allow higher throughput. In contrast, we show that in dense wireless multi-hop networks, the optimal load balancing can be achieved by a destination based single-path routing referred to as field-line routing. This is because any routing can be transformed to the corresponding field-line routing with the same or better performance, by using as paths, the field lines of the so-called destination flow associated with the original routing. The concepts are illustrated with two examples. In the case of a unit disk with unit traffic, the maximal load of 0.389 of a multi-path routing system is reduced to 0.343 by using the field-line routing. Similar improvements are also demonstrated for the unit square. 相似文献
5.
The animation environment Jeliot automates visualization of algorithms over the Internet. The user can visualize algorithms of his own, not merely the selection supplied by a service provider. Jeliot is based on self-animating data types: the user selects the data objects of the source code to be visualized, and Jeliot produces the animation based on operations performed on those types. We present the design of Jeliot and the principles of its implementation. In addition, we discuss the educational applications of Jeliot. 相似文献
6.
Helmi Keskinen Jyrki M. Mäkelä Mikko Aromaa Jorma Keskinen Sami Areva Cilâine V. Teixeira Jarl B. Rosenholm Viljami Pore Mikko Ritala Markku Leskelä Mari Raulio Mirja S. Salkinoja-Salonen Erkki Levänen Tapio Mäntylä 《Catalysis Letters》2006,111(3-4):127-132
Titania and titania-silver nanoparticle deposits were made by Liquid Flame Spray technique, in which the liquid precursor
is injected into a high temperature flame, where it will evaporate and nucleate to nanosize particles. One-step and two-step
methods were used for preparation of titania-silver deposits. The amount of silver added was 1 wt%. The deposits were collected
in the flame zone on steel and glass surfaces and were analyzed by TEM, EDS, XPS and SAXS. The titania deposits consisted
of porous nanosized titania agglomerates of primary particles (~10 nm). With silver addition, small spherical silver metal
particles (~2 nm) were detected on the agglomerates. An increase in the photocatalytic activity was verified by stearic acid
decomposition and biofilm removal using Deinococcus geothermalis as the model organism. 相似文献
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Functional reliability of a service firearm is essential. A failure to fire at a critical moment could lead to disastrous consequences. The firing pin of a weapon must hit the primer hard enough to ascertain reliable detonation of the primer which then ignites the powder. Depths of firing pin created indent on an inert primer and on a copper cylinder are the two methods conventionally used to estimate this percussion energy. In this study the copper cylinder method was compared with piezoelectric measurement. It was found out that both systems give reliable readings. Eight pistols of calibre 9 mm were measured. Although the majority of the measured weapons seemed to provide sufficient percussion energy, there were some surprisingly low readings with seemingly perfect weapons. This discrepancy shows the necessity of an industrial standard and of using a reliable percussion energy measurement system for monitoring the condition of service weapons. Further research on firearm and ammunition primer compatibility is required. 相似文献
9.
Karvinen J Laitala V Mäkinen ML Mulari O Tamminen J Hermonen J Hurskainen P Hemmilä I 《Analytical chemistry》2004,76(5):1429-1436
We have developed assay technologies to measure hydrolyzing enzymes based on homogeneous time-resolved fluorescence quenching (TruPoint). High sensitivity was obtained using fluorescent europium chelates as labels, internally quenched by suitable quenchers and released upon enzymatic reaction. This approach allows robust and sensitive monitoring of low enzyme activities. The assay technology and the choice of donor-acceptor pairs were evaluated in three different enzymatic assays, a protease related to apoptosis, helicase involved in DNA unwinding, and phosphatase having an important role in cellular signaling cascades. All the assays produced an increasing signal, were sensitive, and had a good dynamic range. There were significant differences in optimized quenchers for each of the assays depending on the size, flexibility, and rigidity of the substrates. Also, clear differences in the energy-transfer reactions, their requirements for spectral overlapping, ionic interactions, and energy-transfer distances were found. Each of the enzymatic assays was briefly tested in a high-throughput screening environment by analyzing signal dynamics and statistical relevance as Z' factors. 相似文献
10.
Random waypoint mobility model in cellular networks 总被引:2,自引:0,他引:2
In this paper we study the so-called random waypoint (RWP) mobility model in the context of cellular networks. In the RWP model the nodes, i.e., mobile users, move along a zigzag path consisting of straight legs from one waypoint to the next. Each waypoint is assumed to be drawn from the uniform distribution over the given convex domain. In this paper we characterise the key performance measures, mean handover rate and mean sojourn time from the point of view of an arbitrary cell, as well as the mean handover rate in the network. To this end, we present an exact analytical formula for the mean arrival rate across an arbitrary curve. This result together with the pdf of the node location, allows us to compute all other interesting measures. The results are illustrated by several numerical examples. For instance, as a straightforward application of these results one can easily adjust the model parameters in a simulation so that the scenario matches well with, e.g., the measured sojourn times in a cell. 相似文献