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2.
When materials such as Armco iron, titanium etc., are subject to impact it can be observed that two basic inelastic processes
take place – slip and deformation twinning. Of these processes, inelasticity associated with the slip mechanism has received
considerable attention. For example, Zerilli and Armstrong (1988) modeled the Taylor impact test for a variety of materials
using traditional plasticity theories. They found that there was a significant discrepancy between the theoretical and experimental
results for some materials. They attributed this to the fact that they had neglected deformation twinning in their models.
Subsequent metallurgical studies have indicated that twinning had indeed taken place in these materials.
In this study, we focus on the inelastic processes solely due to deformation twinning (i.e., neglecting slip). We model these
processes using the approach of Rajagopal and Srinivasa (1995, 1997) and Srinivasa et al., (1997), the results of which are
briefly summarized in section 2.1. In order to better understand the twinning process, we study the Taylor impact test for
a 2-D slab under the assumption that only deformation twinning takes place and solve the governing dynamical equations by
using the finite element method. The results show that the twinned zone is concentrated near the point of impact and indeed
it contributes significantly to the overall permanent shape change due to the impact. 相似文献
3.
4.
This article reports the effect of three cobalt carboxylates—cobalt stearate (CoSt3), cobalt palmitate (CoPal3), and cobalt laurate (CoLau3)—on the thermo‐oxidative degradation of low‐density polyethylene (LDPE) films prepared by sheeting process. The carboxylates were blended with LDPE in the concentration range of 0.05–0.2% (w/w). The degradation was monitored by techniques such as FTIR spectroscopy, change in the mechanical properties (tensile strength and elongation at break), viscometry, surface electron microscopy, melt flow index measurements, and apparent density measurements. Studies indicate that films containing these additives are highly susceptible to thermo‐oxidative degradation. Oxygen containing functionalities such as carbonyl and vinyl species are generated on the surface of polyethylene because of thermo‐oxidation, as indicated by FTIR studies. This oxidative process is accelerated in the presence of cobalt carboxylates. The degradation of LDPE was found to increase proportionally with concentration as well as with increasing chain length of the cobalt carboxylate, and follow the order CoSt3 > CoPal3 > CoLau3. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3758–3765, 2007 相似文献
5.
A. R. Usha Devi A. K. Rajagopal Sudha H. S. Karthik J. Prabhu Tej 《Quantum Information Processing》2013,12(12):3717-3723
Classical and quantum world views differ in peculiar ways. Understanding decisive quantum features—for which no classical explanation exist—and their interrelations is of foundational interest. Moreover, recognizing non-classical features carries practical significance in information processing tasks as it offers insights as to why quantum protocols work better than their classical counterparts. We focus here on two celebrated notions of non-classicality viz., negativity of P phase–space representation and entanglement in symmetric multiqubit systems. We prove that they imply each other. 相似文献
6.
Summary The mechanics of flowing granular materials such as coal, sand, metal ores, etc., and their flow characteristics have received considerable attention in recent years as it has relevance to several important technological problems. In a number of instances, these materials are also heated prior to processing, or cooled after processing. The governing equations for the flow of granular materials, taking into account the heat transfer mechanism by conduction, are derived using a continuum model (cf. Goodman and Cowin [1], [2], Rajagopal and Massoudi [3]). For a fully developed flow of these materials down an inclined plane, the equations reduce to a system of coupled non-linear ordinary differential equations. The resulting boundary value problem is solved numerically and the results are presented for cases where the viscosity and thermal conductivity are assumed to be functions of the volume fraction. It is shown that the equations admit multiple solutions for certain values of the parameters.List of symbols
D
Symmetric part of the velocity gradient
-
K
thermal conductivity
-
L
velocity gradient
-
T
Cauchy stress tensor
-
b
body force
-
h
characteristic height
-
q
heat flux
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r
radiating heat
-
u
velocity vector
-
angle of inclination of the inclined plane with the horizontal
-
specific internal energy
-
distributed mass density
-
temperature
-
volume fraction
-
bulk mass density 相似文献
7.
J. B. Mandal B. Bandyopadhyay B. Ghosh H. Rajagopal A. Sequeira J. V. Yakhmi 《Journal of Superconductivity》1996,9(2):253-257
Rietveld analysis of powder neutron diffraction pattern recorded on Sr-based 1201-phase superconductor (T
c
=53 K), (Hg0.7Cr0.3)Sr2CuO4+ shows that the oxygen atoms at O(3) site are disordered atx=y=0.3712. This fourfold split site has a total combined occupancy of 80% and is the only occupied site in the (Hg, Cr)O plane. 相似文献
8.
We explore tradeoffs between organization and number of ALUs and clock frequency in a stream processor. The tool provides candidate low-power configurations and estimates of their real-time performance. The tool relates instruction-level, subword, and data parallelism to functional units' organization and utilization. The exploration methodology is applicable to all embedded-processor designs in signal and media processing. 相似文献
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