全文获取类型
收费全文 | 1817篇 |
免费 | 81篇 |
专业分类
电工技术 | 8篇 |
综合类 | 2篇 |
化学工业 | 407篇 |
金属工艺 | 26篇 |
机械仪表 | 14篇 |
建筑科学 | 125篇 |
矿业工程 | 2篇 |
能源动力 | 48篇 |
轻工业 | 184篇 |
水利工程 | 13篇 |
石油天然气 | 11篇 |
无线电 | 77篇 |
一般工业技术 | 389篇 |
冶金工业 | 300篇 |
原子能技术 | 12篇 |
自动化技术 | 280篇 |
出版年
2023年 | 14篇 |
2022年 | 22篇 |
2021年 | 26篇 |
2020年 | 24篇 |
2019年 | 20篇 |
2018年 | 31篇 |
2017年 | 42篇 |
2016年 | 54篇 |
2015年 | 41篇 |
2014年 | 47篇 |
2013年 | 105篇 |
2012年 | 88篇 |
2011年 | 114篇 |
2010年 | 69篇 |
2009年 | 78篇 |
2008年 | 96篇 |
2007年 | 73篇 |
2006年 | 62篇 |
2005年 | 60篇 |
2004年 | 49篇 |
2003年 | 55篇 |
2002年 | 47篇 |
2001年 | 33篇 |
2000年 | 29篇 |
1999年 | 30篇 |
1998年 | 28篇 |
1997年 | 27篇 |
1996年 | 41篇 |
1995年 | 31篇 |
1994年 | 31篇 |
1993年 | 30篇 |
1992年 | 22篇 |
1991年 | 10篇 |
1990年 | 16篇 |
1989年 | 22篇 |
1988年 | 20篇 |
1987年 | 15篇 |
1986年 | 16篇 |
1985年 | 39篇 |
1984年 | 25篇 |
1983年 | 14篇 |
1982年 | 30篇 |
1981年 | 28篇 |
1980年 | 26篇 |
1979年 | 24篇 |
1978年 | 16篇 |
1977年 | 20篇 |
1975年 | 14篇 |
1974年 | 6篇 |
1973年 | 16篇 |
排序方式: 共有1898条查询结果,搜索用时 15 毫秒
11.
Michael Sonis Geoffrey J. D. Hewings Eduardo Haddad 《The Annals of Regional Science》1996,30(4):391-408
The effects of structural change in all sectors of some regions in multiregional input-output systems are explored in this paper. For each region, the changes in direct inputs are decomposed into a matrix of intraregional changes and a matrix of interregional backward linkage changes. This distinction provides for a decomposition of changes in the Leontief inverse into a sum of matrices representing the matrices of intraregional and interregional fields of influence of changes. In turn, this process facilitates the identification of changes in gross outputs that may be traced to changes in intra- and interregional structural changes. The analysis is applied to the European input-output tables for 1975 and 1985.This paper was presented at the 1996 annual meeting of the Western Regional Science Association 相似文献
12.
Two experiments examined the disruption of feature-based selection in triple-conjunction search at multiple target transfers. In Experiment 1, after 10 training sessions, a new target possessing previous distractor features was introduced. This produced disruption in RT and fixation number, but no disruption in feature-based selection. Specifically, there was a tendency to fixate objects sharing the target's contrast polarity and shape and this did not change even upon transfer to the new target. In Experiment 2, 30 training sessions were provided with three target transfers. At the first transfer, the results replicated Experiment 1. Subsequent transfers did not produce disruption on any measure. These findings are discussed in terms of strength theory, Guided Search, rule-based approaches to perceptual learning, and the area activation model. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
13.
Balfour Louise; White Donna Romano; Schiffrin Alicia; Dougherty Geoffrey; Dufresne Jackie 《Canadian Metallurgical Quarterly》1993,12(1):33
Examining the relationship of stress, dietary disinhibition, and blood glucose control in diabetic young women was the goal of this study. 65 diabetic girls and women, ranging in age from 12 to 26 yrs, completed eating behaviors and perceived stress scales during regular clinic visits. Blood glucose control was assessed by concurrent glycosylated hemoglobin measurements. Multiple regression analyses indicated that high levels of perceived stress predicted dietary disinhibition and that within the age range studied, young women were more likely than early adolescent girls to perceive their life as stressful. Contrary to previous findings that failed to show that stress can indirectly affect glucose control by interfering with compliance behaviors, the present work indicated a Stress?×?Dietary Disinhibition interaction in predicting glucose control. Blood glucose control was poorest in those diabetic women who both perceived their lives as stressful and reported medium to high disinhibition. Blood glucose control was unrelated to stress in young women who reported low levels of disinhibition. These results have implications for the development of specific interventions for young diabetic women who perceive their lives as stressful and who may respond to stress by eating. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
14.
Abstract. Regional scientists have had a long fascination with spatial economic interdependence, initially stimulated by the development of a suite of models in Isard (1960). In recent years there have been two major developments; first, a movement towards greater integration in model development not only with large-scale models, but also with careful attempts to make more components of the system endogenous. The second development has been the pursuit of greater integration than in earlier studies between theory and applied regional economic modelling, most notably in the area of trade and economic development. We explore some of the recent developments of this latter approach and provide an assessment of the current state-of-the art of some future opportunities. 相似文献
15.
16.
The relative reactivities of the lower alkanes in hydrogenolysis on a Pt/Al2O3 catalyst depend on the H2 pressure used, as do those of a Ru/Al2O3 catalyst, pretreated in various ways, for propane hydrogenolysis. Apparent activation energies also vary with H2 pressure. No single rate measurement adequately represents catalytic activity, which is properly defined as the rateconstant for the slow step. 相似文献
17.
The aziridinyl group has been introduced as a terminal substituent into a series of monoazo disperse dyes; the dyes absorb hypsochromically in comparison with their counterparts containing larger terminal ring systems. When applied from aqueous dyebaths the dyes exhibit higher wash fastness on nylon 6.6 and diacetate fibres than conventional dispersedyes of similar structure and relative molecular mass. On polyester and triacetate fibresthe aziridinyl dyes display similar wash fastness to conventional dyes. Dye polymerisation and/or covalent fixation may account for the observed high fastness of the dyes on diacetate and nylon fibres. With the exception of nylon 6.6, the aziridinyl dyes display lower light fastness than conventional disperse dyes on the fibres studied, this being attributable to the greater susceptibility of the aziridinyl dyes to oxidative rather than reductive photodegradation. 相似文献
18.
A novel method of gas sparging from a rotating cylinder is proposed, which prevents against formation of large attached gas cavities in cross‐flowing liquids including those flowing downwards. Experimental and theoretical results regarding critical rotation speed necessary to remove the attached cavity, bubble formation process and size distribution of the produced bubbles in a low viscosity system (air‐water) are presented in this study. 相似文献
19.
Cameron Allan Gunn Jennifer L. DicksonChristopher G. Pretty Jane M. AlsweilerAdrienne Lynn Geoffrey M. ShawJ. Geoffrey Chase 《Computer methods and programs in biomedicine》2014
Introduction
Hyperglycaemia is a common complication of stress and prematurity in extremely low-birth-weight infants. Model-based insulin therapy protocols have the ability to safely improve glycaemic control for this group. Estimating non-insulin-mediated brain glucose uptake by the central nervous system in these models is typically done using population-based body weight models, which may not be ideal.Method
A head circumference-based model that separately treats small-for-gestational-age (SGA) and appropriate-for-gestational-age (AGA) infants is compared to a body weight model in a retrospective analysis of 48 patients with a median birth weight of 750 g and median gestational age of 25 weeks. Estimated brain mass, model-based insulin sensitivity (SI) profiles, and projected glycaemic control outcomes are investigated. SGA infants (5) are also analyzed as a separate cohort.Results
Across the entire cohort, estimated brain mass deviated by a median 10% between models, with a per-patient median difference in SI of 3.5%. For the SGA group, brain mass deviation was 42%, and per-patient SI deviation 13.7%. In virtual trials, 87–93% of recommended insulin rates were equal or slightly reduced (Δ < 0.16 mU/h) under the head circumference method, while glycaemic control outcomes showed little change.Conclusion
The results suggest that body weight methods are not as accurate as head circumference methods. Head circumference-based estimates may offer improved modelling accuracy and a small reduction in insulin administration, particularly for SGA infants. 相似文献20.
Sayant Saengsuwan Sauvarop Bualek-Limcharoen Geoffrey R. MitchellRobert H. Olley 《Polymer》2003,44(11):3407-3415
In situ composite films were prepared by a two-step method. First, polypropylene and thermotropic liquid crystalline polymer (TLCP), Rodrun LC5000 (80 mol% p-hydroxy benzoic acid (HBA)/20 mol% polyethylene terephthalate (PET)), were melt blended in a twin-screw extruder and then fabricated by extrusion through a mini-extruder as cast film. Rheological behavior of the blends, morphology of the extruded strands and films, and tensile properties of the in situ composite films were investigated. Rheological behavior of the blends at 295 °C studied using a plate-and-plate rheometer revealed a substantial reduction of the complex viscosity with increasing TLCP content, and all specimens exhibited shear thinning behavior. Over the angular frequency range of 0.6-200 rad/s, the viscosity ratio (dispersed phase to matrix phase) was found to be very low, in the range of 0.03-0.07. Morphologies of the fracture surfaces of the blend extrudates and the film surfaces etched in permanganic solution were investigated by scanning electron microscope (SEM). The TLCP droplets in the extruded strands were seen with a progressive deformation into fibrillar structure when TLCP content was increased up to 30 wt%. In the extruded films, TLCP fibrils with increasing aspect ratio (length to width) were observed with increasing TLCP concentration. Orientation functions of each component were determined by X-ray diffraction using a novel separation technique. It was observed that the Young's modulus in machine direction of the extruded film was greatly improved with increasing TLCP loading, due to the increase in fiber aspect ratio and also molecular orientation. 相似文献