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21.
Comparative repeatability of guide-pin axis positioning in computer-assisted and manual femoral head resurfacing arthroplasty 总被引:1,自引:0,他引:1
Hodgson A Helmy N Masri BA Greidanus NV Inkpen KB Duncan CP Garbuz DS Anglin C 《Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine》2007,221(7):713-724
The orientation of the femoral component in hip resurfacing arthroplasty affects the likelihood of loosening and fracture. Computer-assisted surgery has been shown to improve significantly the surgeon's ability to achieve a desired position and orientation; nevertheless, both bias and variability in positioning remain and can potentially be improved. The authors recently developed a computer-assisted surgical (CAS) technique to guide the placement of the pin used in femoral head resurfacing arthroplasty and showed that it produced significantly less variation than a typical manual technique in varus/valgus placement relative to a preoperatively determined surgical plan while taking a comparable amount of time. In the present study, the repeatability of both the CAS and manual techniques is evaluated in order to estimate the relative contributions to overall variability of surgical technique (CAS versus manual), surgeon experience (novice versus experienced), and other sources of variability (e.g. across specimens and across surgeons). This will enable further improvements in the accuracy of CAS techniques. Three residents/fellows new to femoral head resurfacing and three experienced hip arthroplasty surgeons performed 20-30 repetitions of each of the CAS and manual techniques on at least one of four cadaveric femur specimens. The CAS system had markedly better repeatability (1.2 degrees) in varus/valgus placement relative to the manual technique (2.8 degrees), slightly worse repeatability in version (4.4 degrees versus 3.2 degrees), markedly better repeatability in mid-neck placement (0.7 mm versus 2.5 mm), no significant dependence on surgeon skill level (in contrast to the manual technique), and took significantly less time (50 s versus 123 s). Proposed improvements to the version measurement process showed potential for reducing the standard deviation by almost two thirds. This study supports the use of CAS for femoral head resurfacing as it is quicker than the manual technique, independent of surgeon experience, and demonstrates improved repeatability. 相似文献
22.
This paper reports on a pilot investigation into web conferencing in a distance learning module. It focuses on the perceptions and experiences of the tutors, all of whom were new to the web conferencing environment, but were experienced in online teaching. A number of web conferencing tutorials were studied through the collection of various datasets, mostly qualitative. The data were analysed by a team of researchers, informed by key literature in this area.The main findings from the pilot indicated that tutors experienced challenges in creating social presence and in managing cognitive load when dealing with multiple tasks online. There were also technical obstacles to improvisation in response to students’ emerging needs. The findings of the pilot informed the training and support provided when web tutorials were subsequently rolled out to all tutorial groups (approximately 140) in the module. Overall, experiences from the web tutorials indicate that tutors and students reacted positively to the opportunities web conferencing provides for interactive learning and teaching. 相似文献
23.
Witnessing in merging biological, social and algorithmic realities is crucial to trust, as modelled in the YUTPA framework.
Being witness and bearing witness is fundamental to human interaction. System participation in human communities of practice
challenges the notion of witnessing and therefore the ability to build trust. Nevertheless, through trial and error, people
in a variety of practices have found ways to establish the presence and develop trust in merging realities. This paper presents
the results of 20 in-depth interviews with professionals from a variety of disciplines and nations. The conclusion of cumulative
analysis is that systems do not witness themselves, but their output deeply affects the mental maps that human beings make
of each other, the world around them and their own self. Essential qualities human beings seek when being involved with other
beings are defined by granularity and reciprocity in the design of time (duration of engagement, synchronizing performance,
integrating rhythms and moments to signify), place (body sense, material interaction, emotional space and situated agency),
relation (shared meaning, engagement, reputation and use) and action (tuning, reciprocity, negotiation and quality of deeds).
By designing granular interaction in 4 dimensions, reciprocity in witnessing obtains significance and the basis for establishing
trust in a variety of presences emerges while human agency acquires potential. 相似文献
24.
Jonathan Keller Damian Carr Frances Love Paul Grabill Hieu Ngo Perumal Shanthakumaran 《Journal of Intelligent Manufacturing》2012,23(2):205-211
The US Army has launched an aggressive program to implement condition based maintenance on its rotary wing assets. Condition
Based Maintenance takes advantage of technology developments in the areas of machinery monitoring, signal processing and fault
modeling to reduce the cost of ownership through improved maintenance procedures. Documenting the reduction in maintenance
burden, cost savings and increased safety through early detection of helicopter faults is an important step in justifying
the program. This paper describes a novel technique used to detect a serious fault in the accessory section of the AH-64D
Apache main transmission. The technique determines if the primary or secondary clutch system is driving the aircraft accessories
through a tachometer speed ratio. The method has identified three aircraft operating on the secondary system allowing Army
maintenance crews to replace the affected transmissions and quickly restore the aircraft to operational status. 相似文献
25.
Thin ZnO films were deposited by radio frequency (r.f.) and direct current (d.c.) magnetron sputtering techniques onto glass substrates. Microstructural and electrical properties of ZnO films were studied using X-ray diffractometer (XRD), scanning electron microscope (SEM) and resistivity measurements. It was found that the size of the crystallites in the d.c. deposited films increased with increasing film thickness, while the crystallite size of r.f. deposited films remained unchanged. The d.c. deposited grains also had much stronger orientation related to the substrate than the r.f. films. XRD data indicated that the thin films with d<350 nm for r.f. and <750 nm for d.c. films have a very high degree of ZnO nonstoichiometry. This agreed well with the conductivity measurements and R(T) behaviour of the films with different resistance R. It was also found that the electrical resistivity of the samples increased exponentially with the thickness of films. 相似文献
26.
Effect of microstructure on the stability of retained austenite in transformation-induced-plasticity steels 总被引:2,自引:0,他引:2
I. B. Timokhina P. D. Hodgson E. V. Pereloma 《Metallurgical and Materials Transactions A》2004,35(8):2331-2341
Two Fe-0.2C-1.55Mn-1.5Si (in wt pct) steels, with and without the addition of 0.039Nb (in wt pct), were studied using laboratory
rolling-mill simulations of controlled thermomechanical processing. The microstructures of all samples were characterized
by optical metallography, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The microstructural behavior
of phases under applied strain was studied using a heat-tinting technique. Despite the similarity in the microstructures of
the two steels (equal amounts of polygonal ferrite, carbide-free bainite, and retained austenite), the mechanical properties
were different. The mechanical properties of these transformation-induced-plasticity (TRIP) steels depended not only on the
individual behavior of all these phases, but also on the interaction between the phases during deformation. The polygonal
ferrite and bainite of the C-Mn-Si steel contributed to the elongation more than these phases in the C-Mn-Si-Nb-steel. The
stability of retained austenite depends on its location within the microstructure, the morphology of the bainite, and its
interaction with other phases during straining. Granular bainite was the bainite morphology that provided the optimum stability
of the retained austenite. 相似文献
27.
Silk Jennifer S.; Sessa Frances M.; Sheffield Morris Amanda; Steinberg Laurence; Avenevoli Shelli 《Canadian Metallurgical Quarterly》2004,18(1):135
This study explored the moderating effects of children's neighborhoods on the link between hostile parenting and externalizing behavior. Participants were 1st- or 2nd-grade children in an urban northeastern community. Children were administered the Parenting and Neighborhood scales of the Child Puppet Interview, and mothers completed questionnaires on neighborhood quality and parenting practices. Census tract measures of neighborhood quality and teachers' reports of children's externalizing behavior also were obtained. Results indicated that children's and mothers' perceptions of neighborhood involvement-cohesion buffered the link between hostile parenting and externalizing problems. Children's externalizing behavior was unrelated to census tract variables. Findings highlight the protective effect of neighborhood social cohesion and the utility of including young children's perspectives in research on neighborhoods and families. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
28.
The academic literature in 2000 presented a procedure for solving the job-shop-scheduling problem of minimizing L max. The iterative-adaptive simulation-based procedure is shown here to perform well on large-scale problems. However, there is potential for improvement in closing the gap between best-known solutions and the lower bound. In the present paper, a simulated annealing post-processing procedure is presented and evaluated on large-scale problems. A new neighbourhood structure for local searches in the job-shop scheduling problem is developed. The procedure is also evaluated using benchmark problems and new upper bounds are established. 相似文献
29.
ABSTRACTTotal quality management (TQM) has been increasingly accepted as a management philosophy. Criteria such as those contained in the Malcolm Baldrige National Quality Award (MBNQA) often guide TQM implementation. However, reports indicate that fully assessing TQM efforts is difficult and hiring experts to help with this task is expensive. Using survey instruments is an attractive alternative to full-scale assessment. Despite the availability of many papers covering organizational performance assessment, few instruments specifically address TQM evaluation. Furthermore, none of the TQM assessment instruments has been subjected to rigorous validation; thus, only modest confidence can be placed in results obtained from their use. This article proposes a quick and cost-effective instrument that is a simple questionnaire designed to assist organizations in conducting self-evaluations of their TQM programs. The proposed instrument is based on the seven categories of the MBNQA criteria and was developed in cooperation with the Excellence in Missouri Foundation, which administers the Missouri Quality Award (MQA). This article highlights how questionnaire results can be used to guide further TQM implementation efforts. 相似文献
30.
Frances Richards 《Journal of Failure Analysis and Prevention》2013,13(6):653-657
From aviation accidents to pipeline explosions, the National Transportation Safety Board is often called to determine probable cause and make safety recommendations, as they did in the aftermath of the 2010 San Bruno pipeline explosion. 相似文献