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排序方式: 共有3127条查询结果,搜索用时 15 毫秒
1.
Felipe A. Perdomo Siti H. Khalit Claire S. Adjiman Amparo Galindo George Jackson 《American Institute of Chemical Engineers》2021,67(3):e17194
The SAFT-γ Mie group-contribution equation of state is used to represent the fluid-phase behavior of aqueous solutions of a variety of linear, branched, and cyclic amines. New group interactions are developed in order to model the mixtures of interest, including the like and unlike interactions between alkyl primary, secondary, and tertiary amine groups (NH2, NH, N), cyclic secondary and tertiary amine groups (cNH, cN), and cyclic methine-amine groups (cCHNH, cCHN) with water (H2O). The group-interaction parameters are estimated from appropriate experimental thermodynamic data for pure amines and selected mixtures. By taking advantage of the group-contribution nature of the method, one can describe the fluid-phase behavior of mixtures of molecules comprising those groups over broad ranges of temperature, pressure, and composition. A number of aqueous solutions of amines are studied including linear, branched aliphatic, and cyclic amines. Liquid–liquid equilibria (LLE) bounded by lower critical solution temperatures (LCSTs) have been reported experimentally and are reproduced here with the SAFT-γ Mie approach. The main feature of the approach is the ability not only to represent accurately the experimental data employed in the parameter estimation, but also to predict the vapor–liquid, liquid–liquid, and vapor–liquid–liquid equilibria, and LCSTs with the same set of parameters. Pure compound and binary phase diagrams of diverse types of amines and their aqueous solutions are assessed in order to demonstrate the main features of the thermodynamic and fluid-phase behavior. 相似文献
2.
van Dick Rolf; Wagner Ulrich; Pettigrew Thomas F.; Christ Oliver; Wolf Carina; Petzel Thomas; Castro Vanessa Smith; Jackson James S. 《Canadian Metallurgical Quarterly》2004,87(2):211
Furthering G. W. Allport's (1954) contentions for optimal contact, the authors introduce a new construct: the perceived importance of contact. They propose that perceived importance is the best proximal predictor of contact's reduction of prejudice. If individuals have opportunities for contact at work or in the neighborhood, their chances to have intergroup acquaintances and friends increase. Intergroup contact among acquaintances and friends can be perceived as more or less important, which in turn determines intergroup evaluations. A 1st study shows that the new measure of perceived importance is indeed distinct from established quantity and quality indicators. The results are cross-validated in a 2nd study that also sheds light on the meaning of importance. In 3rd and 4th studies, structural equation analyses and a meta-analysis support the hypotheses. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
3.
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Ethan Scarl 《Annals of Mathematics and Artificial Intelligence》1994,11(1-4):493-509
The concept of diagnostic accuracy is examined and redefined to support specific criteria for sensor placement. If the correctness of diagnoser operation is assumed, then any failure to diagnose accurately must be attributable to an inadequacy of sensor data. Inaccuracy in diagnoses can be expressed solely in terms of additional candidates whose faults cannot be ruled out. With ambiguity as the determiner of the quality of a diagnosis, user-defined diagnosability requirements can be expressed in terms of the types and instances of components which are permissible exceptions to perfect diagnosis. This requires a working diagnoser and a simulator, along with sets of system configurations, component fault modes, potentially measurable parameters, and uniqueness requirements for fault isolation. From these, the diagnosability of individual components can be determined for a particular attached subset of the available sensors. An optimum sensor assignment is one that satisfies the most requirements with a fixed number of sensors or, conversely, that minimizes the sensor requirements to achieve a given threshold of diagnosability. The considerable complexity of this search is reduced by exploiting sensor set minimality, structural knowledge, and diagnosis-free extension to the system level. Global optimization and sensor allocation do not add to the number of diagnoses required for diagnosability analysis. Finally, corrective measures are discussed for use when residual costs remain too high, or when redundancy is too low.In support of NASA's Marshall Space Flight Center and the Space Station Freedom Advanced Development Program under NASA contract number NAS 8-37200. 相似文献
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6.
We consider the dynamics of a dark soliton in an elongated harmonically trapped Bose-Einstein condensate. A central question
concerns the behavior at finite temperatures, where dissipation arises due to the presence of a thermal cloud. We study this
problem using coupled Gross-Pitaevskii and N-body simulations, which include the mean field coupling between the condensate and thermal cloud. We find that the soliton
decays relatively quickly even at very low temperatures, with the decay rate increasing with rising temperature. 相似文献
7.
Microscale wear of vitrified abrasive materials 总被引:2,自引:0,他引:2
The study of bonding hard materials such as aluminium oxide and cubic boron nitride (cBN) and the nature of interfacial cohesion between these materials and glass is very important from the perspective of high precision grinding. Vitrified grinding wheels are typically used to remove large volumes of metal and to produce components with very high tolerances. It is expected that the same grinding wheel be used for both rough and finish machining operations. Therefore, the grinding wheel, and in particular its bonding system, is expected to react differently to a variety of machining operations. In order to maintain the integrity of the grinding wheel, the bonding system that is used to hold abrasive grains in place will react differently to forces that are placed on individual bonding bridges. This paper examines the role of vitrification heat treatment on the development of strength between abrasive grains and bonding bridges, and the nature of fracture and wear in vitrified grinding wheels that are used for precision grinding applications. 相似文献
8.
High-speed air breathing propulsion systems have many attractive military and civil applications. The high propulsive efficiency of these systems allows the exploitation of speed, distance, and bigger payloads, or any combination of the three. The severe operating conditions of these systems require particular attention to overall thermal management of the engine/air-frame. Fuel-cooling the engine structure is a viable way of maintaining thermal balance over a range of flight conditions. Air Force applications have focused on using endothermic hydrocarbon fuels to address this issue because of their compatibility with the military operations. Recent ground tests of scramjet engines have demonstrated adequate performance utilizing state-of-the-art technology in materials. This progress has paved the way for an expendable flight test vehicle in the near future. In order to take full advantage of the capabilities of this propulsion system, advances in fuel-cooled structures, high temperature un-cooled materials, and increased heat capacity of hydrocarbon fuels will be needed to enable expendable systems to reach higher Mach numbers. An additional benefit would be realized in future reusable systems. 相似文献
9.
An asymptotic extraction process is developed which leads to an efficient method for the evaluation of the electric field from a Hertzian dipole in a layered geometry. This technique allows for a rapidly converging expression for the electric field which remains well behaved as the source and observation heightsz', z coincide. A useful application of this method is in the calculation of mutual impedance between printed dipoles. 相似文献
10.
Diane M. Hopkins Alan D. Jackson Kenneth Oates 《Microscopy research and technique》1991,18(2):176-182
The standardisation of frozen hydrated bulk biological specimens using gelatin standards is described. The relationship between corrected elemental X-ray counts and ionic concentration was found to be linear, and minimum detectable limits for each element are stated. Variations in uncorrected standard curves were found to be due to changes in aluminium coating thickness. There was an inverse relationship between coating thickness and elemental X-ray counts. The factors causing this are discussed. To avoid errors arising from inconsistent aluminium thickness, experimental material should only be compared with standards of similar aluminium net counts. This can be achieved most easily by mounting and analysing specimen and standard together. 相似文献