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121.
122.
On-line decision support for take-off runway scheduling with uncertain taxi times at London Heathrow airport 总被引:2,自引:0,他引:2
Jason A. D. Atkin Edmund K. Burke John S. Greenwood Dale Reeson 《Journal of Scheduling》2008,11(5):323-346
This paper addresses the challenge of building an automated decision support methodology to tackle the complex problem faced
every day by runway controllers at London Heathrow Airport. Aircraft taxi from stands to holding areas at the end of the take-off
runway where they wait in queues for permission to take off. A runway controller attempts to find the best order for aircraft
to take off. Sequence-dependent separation rules that depend upon aircraft size, departure route and speed group ensure that
this is not a simple problem to solve. Take-off time slots on some aircraft and the need to avoid excessive delay for any
aircraft make this an even more complicated problem. Making this decision at the holding area helps to avoid the problems
of unpredictable push-back and taxi times, but introduces a number of complex spatial constraints that would not otherwise
exist. The holding area allows some flexibility for interchange of aircraft between queues, but this is limited by its physical
layout. These physical constraints are not usually included in academic models of the departure problem. However, any decision
support system to support the take-off runway controller must include them. We show, in this paper, that a decision support
system could help the controllers to significantly improve the departure sequence at busy times of the day, by considering
the taxiing aircraft in addition to those already at the holding area. However, undertaking this re-introduces the issue of
taxi time uncertainty, the effect of which we explicitly measure in these experiments. Empirical results are presented for
experiments using real data from different times of the day, showing how the performance of the system varies depending upon
the volume of traffic and the accuracy of the provided taxi time estimations. We conclude that the development of a good taxi
time prediction system is key to maximising the benefits, although benefits can be observed even without this. 相似文献
123.
Margaret Bruce 《Design Studies》1985,6(1):34-40
The competitive position of UK information technology (IT) manufacturers in the expanding markets for IT equipment is declining. A recent report published by the National Economic Development Council (NEDC)1 describes the situation facing the UK IT industry as one of ‘crisis’.This paper reports some of the findings of an investigation, conducted by the Design Innovation Group at the Open University, into the role of design in the competitiveness of manufacturers of IT equipment. The approach to design and development of four UK companies is examined in detail. It is argued that the supplier's lack of attention to design for user needs contributes to the ‘crisis’ situation expressed by the NEDC. 相似文献
124.
125.
Hooper Stephen R.; Roberts Joanne; Sideris John; Burchinal Margaret; Zeisel Susan 《Canadian Metallurgical Quarterly》2010,46(5):1018
This study's primary purpose was to examine the relative contribution of social-behavioral predictors to reading and math skills. The study expands on Duncan et al.'s (2007) work by using longitudinal methodology from the National Institute of Child Health and Human Development's Study of Child Care and Youth Development (SECCYD) and the Early Childhood Longitudinal Study, Kindergarten Class of 1998–1999 (ECLS-K) databases, and by focusing on potential differences in patterns of early predictors of later reading and math trajectories for African American versus Caucasian students. Predictor measures were selected at kindergarten, and the outcomes included standardized reading and math scores obtained from Grades 1, 3, 5, and 9 for the SECCYD sample, and Grades 3, 5, and 8 for the ECLS-K sample. Consistent with Duncan et al.'s findings, results reflect the relative contributions of early reading and math skills to later functioning in these respective academic domains for both samples, and there are indications for the importance of early expressive language skills to both reading and math in the SECCYD sample. Findings related to the power of social-behavioral predictors, however, are not consistent across samples. Although the SECCYD sample evidenced no such predictors, several interactions in the ECLS-K sample suggested the moderating effects of early ratings of aggressive behaviors and internalizing behaviors on later reading and math for African American students. The moderating effects of early teacher ratings of attention and internalizing behaviors for African American students as compared with Caucasian students in later math growth also were noted. The importance of early social-behavioral functions as related to later academic skills remains an important area of inquiry. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
126.
Frazier Patricia A.; Gavian Margaret; Hirai Reiko; Park Crystal; Tennen Howard; Tomich Patricia; Tashiro Ty 《Canadian Metallurgical Quarterly》2011,3(1):27
This study assessed the relations between pretrauma risk (neuroticism, negative affect, prior distress) and protective (self-esteem, optimism) factors and posttraumatic stress disorder (PTSD) symptoms and potential mediators (subjective event-related distress, unsupportive social interactions, perceived control) of those relations. Students (N = 1,528) at four U.S. universities completed online surveys assessing pretrauma risk and protective factors at Time 1 (T1); 84% (N = 1,281) completed a survey 2 months later (T2). PTSD symptoms and the three potential mediators were assessed among those who experienced potentially traumatic events between T1 and T2 (n = 264). PTSD symptoms related to prior traumas were controlled in all analyses. In structural equation modeling (SEM) analyses, the relation between risk factors and PTSD symptoms was mediated by unsupportive social interactions. Protective factors did not independently predict PTSD symptoms when risk factors also were included in the SEM models. Implications for research and practice are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
127.
The Mississippi and Missouri Rivers experienced flooding in 1993 that fell outside the annual predictable flood period of spring and early summer. Flooding began in late June, peaked in late July (25 232 m3/s on the upper Mississippi and 21 240 m3/s on the Missouri) and remained at or near flood stage into October 1993. This study was performed to determine if disturbance by an unpredicted flood event would alter trophic dynamics of river–floodplain systems by creating shifts in the composition of organic matter available to consumers. The Ohio River, which did not flood during the same period, was examined for comparison. Stable isotopic ratios of carbon and nitrogen from samples collected in 1993 and 1994 were used to characterize potential food sources and determine linkages between food sources and invertebrate and fish consumers. Pairwise contrasts, performed separately for each river, indicated there were few interannual differences in δ13C and δ15N of organic matter sources and consumers. Between sample period (flood year versus normal water year) trends in both flooded rivers were similar to between‐year trends observed for the Ohio River. Trophic structure of the Mississippi and Ohio Rivers was similar in both years, with fine and ultra‐fine transported organic matter and dissolved organic matter representing the major sources of organic matter. Overlapping isotopic signatures in the Missouri River made tracking of sources through the consumers difficult, but similarities in δ13C and δ15N between years indicated trophic structure did not change in response to the flood. The results suggest that consumers continued to rely on sources of organic matter that would be used in the absence of the unpredicted 1993 flood. It is proposed that trophic structure did not change in response to flooding in the Mississippi and Missouri Rivers because both rivers exhibited the same trends observed in the Ohio River. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
128.
Addresses recent research on social and nonverbal learning disabilities. Involvement of right hemispheric dysfunction in these disabilities has been hypothesized, as studies with adults have suggested that documented right hemisphere damage may lead to deficits in social skills, prosody, spatial orientation, problem solving, and recognition of nonverbal cues. Studies of children purported to evidence nonverbal learning disabilities are reviewed and compared with the results from studies of adults with right hemisphere damage. Specific subtypes of nonverbal learning disabilities are reviewed, including the nonverbal perceptual-organization-output subtype, Asperger's syndrome, Developmental Gerstmann syndrome, left hemisyndrome, right hemisphere syndrome, and right parietal lobe syndrome. Finally, implications and future research needs are addressed. The need for a diagnostic nosology and improved and validated intervention techniques is stressed as is early identification of these types of specific nonverbal learning disabilities. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
129.
Reynolds Chandra A.; Gatz Margaret; Pedersen Nancy L. 《Canadian Metallurgical Quarterly》2002,17(2):271
What are the best quantitative methods for studying cognitive decline? This question was investigated in a sample of 638 individuals aged 50 years and older from the Swedish Adoption/Twin Study of Aging. A battery of cognitive tests tapping multiple domains was administered to each individual from 2 to 7 times over a span of 10 years. Four methods of operationalizing cognitive decline were compared: change scores, a criterion-based method, least squares, and random effects regression (RER). The RER results were most consistent with a significant decline across measures and differences between demented and nondemented individuals. Predicted slopes from the RER model also showed the strongest interrelationships within and across cognitive domains as indicated by factor analysis results and stronger associations with demographic, health, and psychosocial predictors. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
130.
CS Butler HE Seward C Greenwood AJ Thomson 《Canadian Metallurgical Quarterly》1997,36(51):16259-16266
The reaction of nitric oxide (NO) with fast cytochrome bo from Escherichia coli has been studied by electronic absorption, MCD, and EPR spectroscopy. Titration of the enzyme with NO showed the formation of two distinct species, consistent with NO binding stoichiometries of 1:1 and 2:1 with observed dissociation constants at pH 7.5 of approximately 2.3 x 10(-)6 and 3.3 x 10(-)5 M. Monitoring the titration by EPR spectroscopy revealed that the broad EPR signals at g approximately 7.3, 3.7, and 2.8 due to magnetic interaction between high-spin heme o (S = 5/2) and CuBII (S = 1/2) are lost. A high-spin heme o signal at g = 6.0 appears as the 1:1 complex is formed but is lost again on formation of the 2:1 complex, which is EPR silent. The absorption spectrum shows that heme o remains in the high-spin FeIII state throughout the titration. These results are consistent with the binding of up to two NO molecules at CuBII. This has been confirmed by studies with the Cl- adduct of fast cytochrome bo. MCD evidence shows that heme o remains ligated by histidine and water. Addition of excess NO to the Cl- adduct leads to the appearance of a high-spin FeIII heme EPR signal. Hence chloride ion binds to CuB, blocking the binding of a second NO molecule. These results suggest a mechanism for the reduction of NO to nitrous oxide by cytochrome bo and cytochrome c oxidase in which the binding of two cis NO molecules at CuB permits the formation of an N-N bond and the abstraction of oxygen by the heme group. 相似文献