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排序方式: 共有262条查询结果,搜索用时 11 毫秒
31.
Area decomposition for electromechanical models of power systems 总被引:1,自引:0,他引:1
Coherency and time scale properties of power system models are shown to be related by the dichotomic solution of a matrix Riccati equation. A grouping algorithm is proposed which reduces the area decomposition problem to obtaining a basis for the slow subsystem and performing a Gaussian elimination. Since the slow coherency measure allows for a lack of coherency in fast parts of machine transients, the resulting area decomposition is independent of fault locations. The procedure is illustrated by a 16-machine example. 相似文献
32.
Using singular perturbation techniques, a system with high frequency oscillations is decomposed into two lower order subsystems, one containing only the slowly varying part and the other containing only the fast oscillatory part. Eigenvalue and state approximations achieved by the subsystems are given. A mass-spring-damper example shows that a stiff spring can be regarded as a perturbation of a rigid rod and an interconnected power system example illustrates the occurrence of coherency and inter-machine oscillations. 相似文献
33.
This paper extends an electromagnetic model for time-harmonic analysis of grounding system in horizontally stratified multilayer medium which consists of air and arbitrary number of soil layers. Complete electromagnetic coupling between grounding system segments is taken into account. The model is based on applying the finite element technique to an integral equation formulation. Through an effective approximation of the attenuation and phase shift effects the computation of Sommerfeld integrals has been avoided, which considerably shortens the computational time. The treatment of non-horizontal segments of grounding grid conductors has been resolved by approximating the segment with five current point sources distributed along the segment length. An algorithm for scalar electric potential computation in any soil layers is presented and compared to published results. The effects of approximating a complex heterogeneous earth structure with a homogeneous earth is also analyzed and discussed. 相似文献
34.
In this article, we study the blocking probability in a wavelength division multiplexing (WDM) based asynchronous bufferless
optical burst switched (OBS) network, equipped with a bank of wavelength converters. Our analysis encloses two wavelength
reservation schemes JIT (just-in-time) and JET (just-enough-time), and two-class data rate. The contribution of our work includes:
(i) derivation of an accurate model for blocking probability of lower priority bursts in case of a non-preempted model; (ii) provision of the analytical model for blocking probability calculation in the OBS network, which includes these
variables: two signaling schemes, partial wavelength conversion, two-class data, traffic intensity, cross-connect speed, number
of wavelengths in WDM fiber, number of fibers in the node, number of wavelength converters, and number of nodes in the path;
(iii) simulation results, which show that partial wavelength conversion provide quite satisfactory quality of service. We
compare performance in a single OBS node, under various sets of parameter values. The OBS network shows great flexibility
in terms of used multiclass data, and there is no dependence on the used higher layer protocol. 相似文献
35.
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37.
Varbanov Petar Sabev Sikdar Subhas Lee Chew Tin 《Clean Technologies and Environmental Policy》2018,20(6):1121-1122
Clean Technologies and Environmental Policy - 相似文献
38.
In this paper, the problem of mining complex temporal patterns in the context of multivariate time series is considered. A new method called the Fast Temporal Pattern Mining with Extended Vertical Lists is introduced. The method is based on an extension of the level‐wise property, which requires a more complex pattern to start at positions within a record where all of the subpatterns of the pattern start. The approach is built around a novel data structure called the Extended Vertical List that tracks positions of the first state of the pattern inside records and links them to appropriate positions of a specific subpattern of the pattern called the prefix. Extensive computational results indicate that the new method performs significantly faster than the previous version of the algorithm for Temporal Pattern Mining; however, the increase in speed comes at the expense of increased memory usage. 相似文献
39.
Nanomotion Detection Method for Testing Antibiotic Resistance and Susceptibility of Slow‐Growing Bacteria 下载免费PDF全文
María Ines Villalba Petar Stupar Wojciech Chomicki Massimiliano Bertacchi Giovanni Dietler Laura Arnal María Elena Vela Osvaldo Yantorno Sandor Kasas 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(4)
Infectious diseases are caused by pathogenic microorganisms and are often severe. Time to fully characterize an infectious agent after sampling and to find the right antibiotic and dose are important factors in the overall success of a patient's treatment. Previous results suggest that a nanomotion detection method could be a convenient tool for reducing antibiotic sensitivity characterization time to several hours. Here, the application of the method for slow‐growing bacteria is demonstrated, taking Bordetella pertussis strains as a model. A low‐cost nanomotion device is able to characterize B. pertussis sensitivity against specific antibiotics within several hours, instead of days, as it is still the case with conventional growth‐based techniques. It can discriminate between resistant and susceptible B. pertussis strains, based on the changes of the sensor's signal before and after the antibiotic addition. Furthermore, minimum inhibitory and bactericidal concentrations of clinically applied antibiotics are compared using both techniques and the suggested similarity is discussed. 相似文献
40.
James Z. Fan Nigel T. Andersen Margherita Biondi Petar Todorovi Bin Sun Olivier Ouellette Jehad Abed Laxmi K. Sagar Min‐Jae Choi Sjoerd Hoogland F. Pelayo García de Arquer Edward H. Sargent 《Advanced materials (Deerfield Beach, Fla.)》2019,31(48)
Infrared‐absorbing colloidal quantum dots (IR CQDs) are materials of interest in tandem solar cells to augment perovskite and cSi photovoltaics (PV). Today's best IR CQD solar cells rely on the use of passivation strategies based on lead iodide; however, these fail to passivate the entire surface of IR CQDs. Lead chloride passivated CQDs show improved passivation, but worse charge transport. Lead bromide passivated CQDs have higher charge mobilities, but worse passivation. Here a mixed lead‐halide (MPbX) ligand exchange is introduced that enables thorough surface passivation without compromising transport. MPbX–PbS CQDs exhibit properties that exceed the best features of single lead‐halide PbS CQDs: they show improved passivation (43 ± 5 meV vs 44 ± 4 meV in Stokes shift) together with higher charge transport (4 × 10‐2 ± 3 × 10‐3 cm2 V‐1 s‐1 vs 3 × 10‐2 ± 3 × 10‐3 cm2 V‐1 s‐1 in mobility). This translates into PV devices having a record IR open‐circuit voltage (IR Voc) of 0.46 ± 0.01 V while simultaneously having an external quantum efficiency of 81 ± 1%. They provide a 1.7× improvement in the power conversion efficiency of IR photons (>1.1 µm) relative to the single lead‐halide controls reported herein. 相似文献