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21.
A new equation is developed in this paper which is further used to divide sorption isotherms into classes which are connected to surface water effects and/or solution water effects and their combinations. It is shown that sorption isotherms can be successfully classified using the new equation into three basic classes I, II (most frequent) and III which roughly correspond to the original Brunauer’s classes. The equation is also used for further division of class II into three subclasses. Criteria for these classifications are presented. 相似文献
22.
23.
This paper compares several interface evaluation methods applied in the case of a computer based learning (CBL) environment, during a longitudinal study performed in three European countries, Greece, Germany, and Holland, and within the framework of an EC funded Leonardo da Vinci program. The paper firstly considers the particularities of the CBL environments presented in comparison to Distance Learning environments, as well as other educational pieces. Subsequently, the software under evaluation is described, as well as the underlying educational theories and the proposed instructional methodology regarding its effective application. In the case under study, a combination of expert-based and empirical (user-based) approaches are dealt with, and the “ideal” combination, for the consumption of the fewest possible resources in order to achieve the maximum outcome for the assessment of the software is investigated. A combinatory evaluation approach is argued for the provision of the best results in the case of complex environments such as educational ones. The results of this study show that both approaches, expert-based and empirical, have been found to perform adequately, although the empirical methodologies are always preferable. Therefore, this study concludes by proposing a combination of an expert-based approach during the early stages of the design cycle with an observational evaluation, performed by the instructors and/or the designers, which has to provide the best cost/performance factor. 相似文献
24.
This paper describes OPC-SMS gateway, a platform that integrates IP networks with the Short Message Service (SMS), in order to deliver an integrated service for access to data sources conforming to Object Linking and Embedding for Process Control (OPC) standard specifications, through SMS-enabled mobile devices. The gateway supports pull and push services in order to support both request-based and alarm/scheduled-based notifications, respectively. The proposed architecture is based entirely on the ubiquitous HyperText Transport Protocol (HTTP), Simple Object Access Protocol (SOAP), Extensible Markup Language (XML) protocols, and the Global System for Mobile communication (GSM) network and thus exploits the network infrastructure already in place. The capability of accessing different types of OPC data sources (real-time and historical) by any SMS-enabled device consists of a highly flexible service, supporting mobility and event-based notification. A pilot implementation of our approach has been tested in a large-scale installation for accessing OPC data sources of several automation subsystems in a hospital. 相似文献
25.
We introduce a problem of module composition. Modules are seen as “black boxes” with input and output ports. A compatibility relation models which input ports can connected to which output ports. We are given a set of available modules and a target module. We want to connect available modules into a chain that implements the target module. Constraints may be given on how many copies of each module can or should appear in the solution chain. Costs may be given on modules or ports or connections, so that an optimal solution with respect to these costs is found. We derive an algorithm to solve the above problem automatically. The algorithm transforms the problem into a shortest-path problem in a graph. 相似文献
26.
A method is proposed for constructing salient features from a set of features that are given as input to a feedforward neural network used for supervised learning. Combinations of the original features are formed that maximize the sensitivity of the network's outputs with respect to variations of its inputs. The method exhibits some similarity to Principal Component Analysis, but also takes into account supervised character of the learning task. It is applied to classification problems leading to improved generalization ability originating from the alleviation of the curse of dimensionality problem. 相似文献
27.
In this paper a mathematical model is presented to predict the macroexothermic phenomena occurring when exothermic additions in lump form are assimilated in ferrous metals. The macroexothermic phenomena take place during the free assimilation period of exothermic additions in ferrous metals. These phenomena are characterized by unique coupled heat, mass and momentum transport phenomena. The presence of a moving boundary complicates further these phenomena. The model uses the Simpler algorithm to solve numerically the pertinent partial differential equations. The extensive verification of the model was carried out in two contexts. The first was, in a low temperature physical model consisting of ice immersion in different sulfuric acid solutions. The melting of ice in these solutions is extremely exothermic. In this physical model, both temperature and velocity measurements were carried out. The model results were compared with experimental measurements and they were found to be in excellent agreement. The second context employed high temperatures, involving the assimilation of silicon in high carbon liquid iron. The model was also applied to predict the position of the moving boundary for these high temperature experiments and a good agreement was obtained. In addition new dimensionless convective heat transfer correlations that quantify these complex phenomena are presented. 相似文献
28.
29.
A generalized temperature boundary condition coupling strategy for the modeling of conventional casting processes was implemented
via experiments and numerical simulations with commercial purity aluminum, aluminum alloy, and tin specimens in copper, graphite,
and sand molds. This novel strategy related the heat transfer coefficient at the metal-mold interface to the following process
variables: the size of the air gap that forms at the metal-mold interface, the roughness of the mold surface, the conductivity
of the gas in the gap, and the thermophysical properties of both the metal and mold. The objective of this study was to obtain,
apply, and evaluate the effect of incorporating an experimentally derived relationship for specifying transient heat transfer
coefficients in a general conventional casting process. The results are presented in two parts. Part I details the implementation
of a systematic experimental approach not limited to a specific process to determine the heat transfer coefficient and characterize
the formation of the air gap at the metal-mold interface. The heat transfer mechanisms at the interface were identified, and
seen to vary in magnitude during four distinct stages, as the air gap formed and grew. A semiempirical inverse equation was
used to characterize the heat transfer coefficient-air gap relationship, across the various stages, for experimental data
from the literature and this study. 相似文献
30.
Carlos R Langezaal Amitabh Chandra Stavros T Katsiotis Johannes J C Scheffer Andre B De Haan 《Journal of the science of food and agriculture》1990,53(4):455-463
Extracts obtained by supercritical carbon dioxide extraction of cones and leaves of hop (Humulus lupulus L) at different combinations of temperature and pressure were analysed for their α- and β-acids and volatiles, using HPLC and GC respectively. The yield and composition of the mixtures of bitter compounds from the cones were largely influenced by the temperature and pressure applied during the extraction. Bitter compounds could not be detected in the extracts from the leaves. The most important volatile components identified were β-myrcene, β-caryophyllene and α-humulene. The extraction parameters also influenced the composition of the mixture of volatiles from the cones and leaves, 40°C and 20.0 MPa being optimum for the extraction of both bitter compounds and volatiles, which are thought to be important for the aroma of beer. 相似文献