全文获取类型
收费全文 | 1813篇 |
免费 | 62篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 24篇 |
综合类 | 1篇 |
化学工业 | 288篇 |
金属工艺 | 24篇 |
机械仪表 | 33篇 |
建筑科学 | 57篇 |
矿业工程 | 4篇 |
能源动力 | 44篇 |
轻工业 | 180篇 |
水利工程 | 9篇 |
石油天然气 | 8篇 |
无线电 | 123篇 |
一般工业技术 | 298篇 |
冶金工业 | 516篇 |
原子能技术 | 20篇 |
自动化技术 | 247篇 |
出版年
2022年 | 15篇 |
2021年 | 17篇 |
2019年 | 10篇 |
2018年 | 20篇 |
2017年 | 34篇 |
2016年 | 34篇 |
2015年 | 34篇 |
2014年 | 40篇 |
2013年 | 95篇 |
2012年 | 60篇 |
2011年 | 75篇 |
2010年 | 80篇 |
2009年 | 57篇 |
2008年 | 64篇 |
2007年 | 50篇 |
2006年 | 52篇 |
2005年 | 34篇 |
2004年 | 51篇 |
2003年 | 64篇 |
2002年 | 49篇 |
2001年 | 33篇 |
2000年 | 43篇 |
1999年 | 36篇 |
1998年 | 125篇 |
1997年 | 70篇 |
1996年 | 58篇 |
1995年 | 39篇 |
1994年 | 36篇 |
1993年 | 29篇 |
1992年 | 28篇 |
1991年 | 19篇 |
1990年 | 12篇 |
1989年 | 14篇 |
1988年 | 16篇 |
1987年 | 18篇 |
1986年 | 21篇 |
1985年 | 28篇 |
1984年 | 17篇 |
1983年 | 21篇 |
1982年 | 17篇 |
1981年 | 23篇 |
1980年 | 20篇 |
1979年 | 10篇 |
1978年 | 16篇 |
1977年 | 34篇 |
1976年 | 28篇 |
1975年 | 20篇 |
1974年 | 22篇 |
1973年 | 22篇 |
1972年 | 14篇 |
排序方式: 共有1876条查询结果,搜索用时 218 毫秒
111.
A. J. Owen J. S. Colbourne C. R. I. Clayton C. Fife-Schaw 《Water and Environment Journal》1999,13(4):241-244
This study uses the psychological framework of 'mental modelling' to compare what experts and laypeople think about the hardness of drinking water. A drinking-water quality mental model was developed using influence-directed network procedures. This was evaluated in qualitative studies in Oxfordshire and the findings revealed gaps in laypeople's knowledge about the water-supply process. 相似文献
112.
Barbara J. Meyer Brin F. S. Grenyer Trevor Crowe Alice J. Owen Elizabeth M. Grigonis-Deane Peter R. C. Howe 《Lipids》2013,48(9):863-868
The aim of this study was to determine if changes in omega‐3 polyunsaturated fatty acid status following tuna oil supplementation correlated with changes in scores of depression. A total of 95 volunteers receiving treatment for major depression were randomised to consume 8 × 1 g capsules per day of HiDHA (2 g DHA, 0.6 g EPA and 10 mg Vitamin E) or olive oil (placebo) for 16 weeks, whilst undergoing weekly counseling sessions by trained clinical psychologists using a standard empirically validated psychotherapy. Depression status was assessed using the 17 item Hamilton rating scale for depression and the Beck Depression Inventory by a psychodiagnostician who was blind to the treatment. Blood was taken at baseline and 16 weeks (n = 48) for measurement of erythrocyte fatty acids. With HiDHA supplementation, erythrocyte DHA content rose from 4.1 ± 0.2 to 7.9 ± 0.4 % (mean ± SEM, p < 0.001) of total fatty acids but did not change (4.0 ± 0.2 to 4.1 ± 0.2 %) in the olive oil group. The mean changes in scores of depression did not differ significantly between the two groups (?12.2 ± 2.1 for tuna oil and ?14.4 ± 2.3 for olive oil). However, analysis of covariance showed that in the fish oil group there was a significant correlation (r = ?0.51) between the change in erythrocyte DHA and the change in scores of depression (p < 0.05). Further study of the relationship between DHA and depression is warranted. 相似文献
113.
Within the general objective of analyzing and modeling the processability of polypropylene and of its short fiber composites, a statistical analysis of the relationship between processing conditions and final properties has been performed applying modern experimental design concepts. In order to gather the largest amount of information with a manageable quantity of experiments, Taguchi methods were used for the design of injection molding tests and for the analysis of experimental fiber orientation and impact strength results. Two levels of each variable of interest were selected, and the results of the analysis not only show which of the processing variables are predominant but also show that interactions between variables must be taken into account. The approach presented here offers a viable route to the scaling-up of the injection molding process through the reduction of the number of variables in the prediction of the processing behavior of semicrystalline polymers and of their composites. 相似文献
114.
115.
Abstract Proper classification and terminology comprise an essential basis for avoiding confusion or imprecision. Classification will assist in recording available data, setting up a global database and developing predictive relationships. In this paper, an attempt to develop a well‐accepted classification of and terminology for food properties is made. The proposed four classes of food properties are: physical and physico‐chemical properties, kinetic properties, sensory properties, and health properties. 相似文献
116.
The concatenation of an equalizer and a Viterbi (1967) decoder is a powerful means for improving receiver performance in wireless communication systems. A soft-output equalizer increases the impact of this combination by enabling the use of soft-decision Viterbi decoding. It is well known that the maximum a posteriori (MAP) algorithm provides optimal reliability information, but at the cost of substantial complexity. This paper contains the results of an investigation into the design and performance of soft-output adaptive equalization techniques based on suboptimum trellis-based soft-output decoding algorithms. It is shown that the performance improvement relative to hard output equalizers is substantial, while the cost in terms of complexity is modest. A time-division multiple-access (TDMA) cellular system is used as the basis for comparisons. Simulation results and a complexity analysis are presented 相似文献
117.
Wade Shari L.; Taylor H. Gerry; Walz Nicolay Chertkoff; Salisbury Shelia; Stancin Terry; Bernard Lori A.; Oberjohn Karen; Yeates Keith Owen 《Canadian Metallurgical Quarterly》2008,53(2):180
Objective: To understand how traumatic brain injury (TBI) affects parent-child interactions acutely following injury. Participants: Young children hospitalized for TBI (n = 80) and orthopedic injuries (OI; n = 113). Method: Raters coded videotaped interactions during free play and structured tasks for parental warmth/responsiveness and negativity and child warmth, behavior regulation, and cooperation. Raters also counted parental directives, critical/restricting statements, and scaffolds. Results: Parents of children with TBI exhibited less warm responsiveness and made more directive statements during a structured task than parents in the OI group. Children with TBI displayed less behavior regulation than children with OI. Parental warm responsiveness was more strongly related to child cooperativeness in the OI group than in the TBI group. Child behavior also mediated group differences in parental responsiveness and directiveness. TBI accounted for as much variance in parental behaviors as or more than did sociodemographic factors. Conclusion: TBI-related changes in child behavior may negatively influence parent-child interactions and disrupt the reciprocity between parent and child. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
118.
Kenny M.J. Netterfield R.P. Wielunski L.S. Beaglehole D. 《IEEE transactions on instrumentation and measurement》1999,48(2):233-237
The Avogadro constant is required to be determined with an uncertainty of less than 1×10-8 in order to allow an atomic definition of the kilogram. A single-crystal silicon sphere 93.6 mm diameter is used for this determination. A thin surface layer (typically 2 nm to 5 nm thick on flats and 10 nm or more on spheres) of contaminants such as oxide, water and hydrocarbons on the sphere can significantly affect the measurements due to corrections for density changes and to phase change on reflection in the diameter measurement by optical interferometry. The stability of this surface layer as a function of time is also of importance because of ongoing measurements. The nature of this contamination has been investigated using optical ellipsometry and ion beam analysis. It is concluded that the composition and structure of the surface layer are affected by a number of parameters and that the most appropriate method of achieving the desired accuracy is to remove the surface layer by etching and to form a hard stable coating of controlled thickness and composition. This coating may be either silicon dioxide or silicon nitride 相似文献
119.
ABET Engineering Criteria 2000 require a selection of outcomes and outcome indicators for each educational objective adopted by an engineering program. This paper describes a database created using Microsoft Access 97 © linking choices of program outcomes and choices of program outcome indicators for all of the accredited engineering programs in an academic institution. With this database, benchmarking searches can be conducted by type of engineering program, by choice of outcome, or by choice of outcome indicator. Several example searches are presented using data describing the engineering programs at Clemson University. A web-site address is given where copies of the Clemson database can be downloaded. 相似文献
120.