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101.
Joseph L. Rose Aleksander Pilarski Yimei Huang 《Research in Nondestructive Evaluation》1990,1(4):247-265
A surface wave velocity measurement technique is used to supply supporting measurements in the computation of elastic constants for practical nondestructive evaluation of composite materials. Theoretical modeling work is carried out to illustrate the surface wave velocity changes as a function of angle with respect to the axes along the fibers of a unidirectional graphite epoxy composite material for a variety of different problems, including porosity (PC) changes, fiber volume fraction (FF) changes, and delamination. Experiments are conducted on two unidirectional reinforced composites and a (0–90)s cross ply graphite epoxy laminate to illustrate the surface wave velocity measurements and the inverse computation procedure for evaluation of the stiffness coefficients. Variations of the feature values in the stiffness matrix are also discussed for inhomogeneities, delaminations through cracking, and large defects.This paper was presented at the Symposium of Wave Propagation in Structural Composites at Berkeley, American Soceity of Mechanical Engineering AMD Volume 9D, June 20–22, 1988. 相似文献
102.
The tremendous success of the World Wide Web is countervailed by efforts needed to search and find relevant information. For tabular structures embedded in HTML documents, typical keyword or link-analysis based search fails. The Semantic Web relies on annotating resources such as documents by means of ontologies and aims to overcome the bottleneck of finding relevant information. Turning the current Web into a Semantic Web requires automatic approaches for annotation since manual approaches will not scale in general. Most efforts have been devoted to automatic generation of ontologies from text, but with quite limited success. However, tabular structures require additional efforts, mainly because understanding of table contents requires the comprehension of the logical structure of the table on the one hand, as well as its semantic interpretation on the other. The focus of this paper is on the automatic transformation and generation of semantic (F-Logic) frames from table-like structures. The presented work consists of a methodology, an accompanying implementation (called TARTAR) and a thorough evaluation. It is based on a grounded cognitive table model which is stepwise instantiated by the methodology. A typical application scenario is the automatic population of ontologies to enable query answering over arbitrary tables (e.g. HTML tables). 相似文献
103.
The fortran 77 code system elsepa for the calculation of elastic scattering of electrons and positrons by atoms, positive ions and molecules is presented. These codes perform relativistic (Dirac) partial-wave calculations for scattering by a local central interaction potential V(r). For atoms and ions, the static-field approximation is adopted, with the potential set equal to the electrostatic interaction energy between the projectile and the target, plus an approximate local exchange interaction when the projectile is an electron. For projectiles with kinetic energies up to 10 keV, the potential may optionally include a semiempirical correlation-polarization potential to describe the effect of the target charge polarizability. Also, for projectiles with energies less than 1 MeV, an imaginary absorptive potential can be introduced to account for the depletion of the projectile wave function caused by open inelastic channels. Molecular cross sections are calculated by means of a single-scattering independent-atom approximation in which the electron density of a bound atom is approximated by that of the free neutral atom. Elastic scattering by individual atoms in solids is described by means of a muffin-tin model potential. Partial-wave calculations are feasible on modest personal computers for energies up to about 5 MeV. The elsepa code also implements approximate factorization methods that allow the fast calculation of elastic cross sections for much higher energies. The interaction model adopted in the calculations is defined by the user by combining the different options offered by the code. The nuclear charge distribution can be selected among four analytical models (point nucleus, uniformly charged sphere, Fermi's distribution and Helm's uniform-uniform distribution). The atomic electron density is handled in numerical form. The distribution package includes data files with electronic densities of neutral atoms of the elements hydrogen to lawrencium (Z=1-103) obtained from multiconfiguration Dirac-Fock self-consistent calculations. For comparison purposes, three simple analytical approximations to the electron density of neutral atoms (corresponding to the Thomas-Fermi, the Thomas-Fermi-Dirac and the Dirac-Hartree-Fock-Slater models) are also included. For calculations of elastic scattering by ions, the electron density should be provided by the user. The exchange potential for electron scattering can be selected among three different analytical approximations (Thomas-Fermi, Furness-McCarthy, Riley-Truhlar). The offered options for the correlation-polarization potential are based on the empirical Buckingham potential. The imaginary absorption potential is calculated from the local-density approximation proposed by Salvat [Phys. Rev. A 68 (2003) 012708].
Program summary
Title of program:ELSEPACatalogue identifier: ADUSProgram summary URL:http://cpc.cs.qub.ac.uk/cpc/summaries/ADUSProgram obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandLicense provisions: noneComputer for which the program is designed and others in which it is operable: Any computer with a FORTRAN 77 compilerOperating systems under which the program has been tested: Windows XP, Windows 2000, Debian GNU/Linux 3.0r0 (sarge)Compilers:1Compaq Visual Fortran v6.5 (Windows); GNU FORTRAN, g77 (Windows and Linux)Programming language used: FORTRAN 77No. of bits in a word: 32Memory required to execute with typical data: 0.6 MbNo. of lines in distributed program, including test data, etc.:135 489No. of bytes in distributed program, including test data, etc.: 1 280 006Distribution format: tar.gzKeywords: Dirac partial-wave analysis, electron elastic scattering, positron elastic scattering, differential cross sections, momentum transfer cross sections, transport cross sections, scattering amplitudes, spin polarization, scattering by complex potentials, high-energy atomic screening functionsNature of the physical problem: The code calculates differential cross sections, total cross sections and transport cross sections for single elastic scattering of electrons and positrons by neutral atoms, positive ions and randomly oriented molecules. For projectiles with kinetic energies less than about 5 MeV, the programs can also compute scattering amplitudes and spin polarization functions.Method of solution: The effective interaction between the projectile and a target atom is represented by a local central potential that can optionally include an imaginary (absorptive) part to account approximately for the coupling with inelastic channels. For projectiles with kinetic energy less that about 5 MeV, the code performs a conventional relativistic Dirac partial-wave analysis. For higher kinetic energies, where the convergence of the partial-wave series is too slow, approximate factorization methods are used.Restrictions on the complexity of the program: The calculations are based on the static-field approximation. The optional correlation-polarization and inelastic absorption corrections are obtained from approximate, semiempirical models. Calculations for molecules are based on a single-scattering independent-atom approximation. To ensure accuracy of the results for scattering by ions, the electron density of the ion must be supplied by the user.Typical running time: on a 2.8 GHz Pentium 4,1 the calculation of elastic scattering by atoms and ions takes between a few seconds and about two minutes, depending on the atomic number of the target, the adopted potential model and the kinetic energy of the projectile.Unusual features of the program: The program calculates elastic cross sections for electrons and positrons with kinetic energies in a wide range, from a few tens of eV up to about 1 GeV. Calculations can be performed for neutral atoms of all elements, from hydrogen to lawrencium (Z=1-103), ions and simple molecules. 相似文献104.
105.
A simple transistor circuit suitable for adaptive-logic experiments is described. Its operation depends on the fusing of links in signal pathways, which are selected by subjecting the device to the correct logical operation. Its application to an adaptable two-bit code translator is described. 相似文献
106.
In this paper the optimal minimum-variance unbiased linear discrete estimate of the mean of a stationary, random process is derived. The behaviour of the estimate in case of increasing the number of samples is discussed. An attempt is presented to apply the technique developed to the recurrential algorithm for an on-line estimation. However, because of the difficulties of obtaining a globally optimal algorithm a suboptimal, one-step, minimum-variance algorithm is derived. 相似文献
107.
A ring structure made of 8 bit random-access memory (r.a.m.) elements is described. The r.a.m.s. are used as variable-function logic devices. Several results are presented relating the stored functions to the overall system function. These include the detection of unique, isolated `1? bits (uniqueness) and unique strings of `1? bits (connectedness) in a binary vector. 相似文献
108.
109.
The purpose of this study was to utilize the job demands-resources model to examine the direct and interactive effects of job demands and cross-training on cognitive, behavioral, and affective outcomes in teams. Results from 54 teams indicated that an increase in job demands reduced mental model accuracy and information allocation and increased tension among team members. Cross-training, on the other hand, increased mental model accuracy and decreased tension among team members. More importantly, the direct effects of cross-training were qualified by the interaction. When job demands were high, cross-trained teams evidenced higher mental model accuracy, more information allocation, and less tension than teams that were not cross-trained. Cross-training was less influential when job demands were low, indicating that cross-training acted as a resource to buffer the negative impact of job demands in teams. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
110.
The purpose of this study was to uncover compositional and emergent influences on unethical behavior by teams. Results from 126 teams indicated that the presence of a formalistic orientation within the team was negatively related to collective unethical decisions. Conversely, the presence of a utilitarian orientation within the team was positively related to both unethical decisions and behaviors. Results also indicated that the relationship between utilitarianism and unethical outcomes was moderated by the level of psychological safety within the team, such that teams with high levels of safety were more likely to engage in unethical behaviors. Implications are discussed, as well as potential directions for future research. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献