全文获取类型
收费全文 | 1825篇 |
免费 | 82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 | 390篇 |
冶金工业 | 307篇 |
原子能技术 | 12篇 |
自动化技术 | 281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 | 43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 | 31篇 |
1997年 | 28篇 |
1996年 | 41篇 |
1995年 | 32篇 |
1994年 | 31篇 |
1993年 | 30篇 |
1992年 | 22篇 |
1991年 | 11篇 |
1990年 | 17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 | 31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1907条查询结果,搜索用时 15 毫秒
991.
Wang J Zhu Y Bawa HK Ng G Wu Y Libera M van der Mei HC Busscher HJ Yu X 《ACS applied materials & interfaces》2011,3(1):67-73
Many next-generation biomaterials will need the ability to not only promote healthy tissue integration but to simultaneously resist bacterial colonization and resulting biomaterials-associated infection. For this purpose, antimicrobial nanofibers of polycaprolactone (PCL) were fabricated by incorporating calcium peroxide. PCL nanofibers containing different ratios of calcium peroxide (1%, 5% and 10% (w/w)) with or without ascorbic acid were fabricated using an electrospinning technique. Antimicrobial evaluations confirmed the inhibitory properties of the nanofibers on the growth of E. coli and S. epidemidis because of a significant burst release of calcium peroxide from the nanofibers. Analysis of tissue cell response showed that despite an initial toxic effect over the first 24 h, after 4 days of culture, osteoblast viability and morphology were both healthy. These results demonstrate that oxygen-generating nanofibers can be designed and developed to provide a short-term peroxide-based antimicrobial response while still maintaining attractive tissue-integration properties. 相似文献
992.
993.
Lavis Yvonna; Kadib Raja; Mitchell Chris; Hall Geoffrey 《Canadian Metallurgical Quarterly》2011,37(2):211
In two experiments, participants received exposure to complex checkerboards (e.g., AX and BX) that consisted of small distinctive features (A and B) superimposed on a larger common background (X). Subsequent discrimination between AX and BX, assessed by a same-different task, was facilitated when the stimuli were presented on alternate trials in preexposure—a perceptual learning effect (Experiment 1). The hypothesis that this form of exposure results in more accurate representations of the unique features was supported in Experiment 1, which showed that participants were well able to match the color of the feature with its shape. Experiment 2 showed that exposure to A and B in isolation, intermixed with presentations of AX and BX, enhanced the perceptual learning effect, which confirmed that the better encoding of the unique features during intermixed preexposure is a direct cause of the enhanced discrimination observed following preexposure on this schedule. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
994.
Maddox Geoffrey B.; Balota David A.; Coane Jennifer H.; Duchek Janet M. 《Canadian Metallurgical Quarterly》2011,26(3):661
The current study examined the effects of two manipulations on equal and expanded spaced retrieval schedules in young and older adults. First, we examined the role that the type of expansion (systematic vs. nonsystematic) has in producing a benefit of expanded retrieval. Second, we examined the influence of an immediate retrieval attempt to minimize forgetting after the original encoding event. It was predicted that including multiple retrieval attempts with minimal intervening spacing (best accomplished in a nonsystematic retrieval schedule) would be necessary to produce a benefit of expanded retrieval over equal spaced retrieval for older adults but not young adults due to age differences in working memory capacity. Results from two experiments revealed that the presence of an expanded over equal spaced retrieval benefit is modulated by the extent to which the spacing conditions minimize forgetting in the early retrieval attempts in the spaced conditions. As predicted, these conditions differ substantially across young and older adults. In particular, in older adults two intervening items between early retrieval attempts produce dramatic rates of forgetting compared to one intervening item, whereas younger adults can maintain performance up to five intervening events in comparable conditions. Discussion focuses on age differences in short term forgetting, working memory capacity, and the relation between forgetting rates and spaced retrieval schedules. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
995.
Reinitz Mark Tippens; Peria William J.; Séguin Julie Anne; Loftus Geoffrey R. 《Canadian Metallurgical Quarterly》2011,37(2):507
Participants studied naturalistic pictures presented for varying brief durations and then received a recognition test on which they indicated whether each picture was old or new and rated their confidence. In 1 experiment they indicated whether each “old”/“new” response was based on memory for a specific feature in the picture or instead on the picture's general familiarity; in another experiment, we defined pictures that tended to elicit feature versus familiarity responses. Thus, feature/familiarity was a dependent variable in 1 experiment and an independent variable in the other. In both experiments feature-based responses were more accurate than those that were familiarity based, and confidence and accuracy increased with duration for both response types. However, when confidence was controlled for, mean accuracy was higher for familiarity-based than for feature-based responses. The theoretical implication is that confidence and accuracy arise from different underlying information. The applied implication is that confidence differences should not be taken as implying accuracy differences when the phenomenal basis of the memory reports differ. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
996.
William R. Ashton Martin Jefferies Robert G. Morley Geoffrey Pass Glyn O. Phillips David M. Power 《Journal of the science of food and agriculture》1975,26(5):697-704
Some physical properties of aqueous solutions of African Albizia zygia (D.C.) Macbride have been evaluated. Approximately 80% of the gum is soluble in the cold with the remainder dispersed as fine particles of gel. pH titration of the gum indicates one acid group, pKa = 3.8, for every three monosaccharide units. Solutions of the gum exhibit typical polyelectrolyte behaviour. The viscosity of the solutions increases with concentration but above 1.5% the solutions exhibit shear-thinning. The viscosity of an ice cream mix containing the gum and the properties of the resultant ice cream are compared with standard mixes. 相似文献
997.
Attia M. Elfak Geoffrey Pass Robert G. Morley 《Journal of the science of food and agriculture》1977,28(10):895-899
The apparent viscosities of dilute solutions of guar and locust bean gums have been measured. The intrinsic viscosity [n] of guar gum solution is greater than that of locust bean gum solution, but the interaction coefficient k of guar gum solutions is less than that of locust bean gum. Addition of glucose, sucrose, or glucose syrup increases the apparent viscosity of the gum solution. The intrinsic viscosity of the gum solution is decreased but the interaction coefficient is increased. 相似文献
998.
Martin L Shaw Jane E Lancaster Geoffrey A Lane 《Journal of the science of food and agriculture》1989,48(4):459-467
Quantitative analysis of the major γ glutamyl peptides present in cultivars of onion (Allium cepa L) bulbs representing brown, white and red varieties was achieved by ion exchange and electrophoretic separations and by quantitation involving integration of ninhydrin-developed spots on thin layer chromatography. γ Glutamyl trans-prop(I)enyl cysteine sulphoxide was found to be the major γ glutamyl peptide in each of the three cultivars at levels between 1.24 and 2.18 mg g?1 fresh weight, followed by S-2-carboxypropyl glutathione (0.45-0.60 mg g?1 fresh weight) and γ glutamyl phenylalanine (0.09-0.16 mg g?1 fresh weight). Conclusive identification of each of the compounds was achieved by NMR spectroscopy and by GC-MS of the n-butyl, trifluoroacetyl derivatives of the hydrolysis products. 相似文献
999.
Attia M. Elfak Geoffrey Pass Glyn O. Phillips 《Journal of the science of food and agriculture》1979,30(4):439-444
The apparent viscosities of aqueous solutions of guar gum and locust bean gum have been measured over a range of shear rates from 14 to 1142 s?1. Comparable measurements were also made on gum solutions to which glucose, sucrose or glucose syrup had been added. For all the solutions the variation of relative viscosity with shear rate fits a power law equation. Addition of sugar has no effect on the non-Newtonian behaviour of the gum solutions. The relative viscosity of the gum in the sugar solutions is lower than in water. The ratios of the relative viscosities closely correspond with the ratios of the intrinsic viscosities. This is interpreted in terms of a smaller extension of the gum molecule in the sugar solution. 相似文献
1000.
Pilot-scale demonstration of cyclodextrin as a solubility-enhancement agent for remediation of a tetrachloroethene-contaminated aquifer 总被引:1,自引:0,他引:1
The limitations associated with conventional pump and treat technology have generated interest in using enhanced in-situ flushing as an alternative for remediating source zones contaminated with immiscible liquid. This research investigates the effectiveness of cyclodextrin as a solubility-enhancement agent to enhance the removal of tetrachloroethene (PCE) from a physically isolated section of an aquifer. An important component of this project was the implementation of reagent recovery and reuse. This field experiment presented the rare opportunity, under strict regulatory guidance, to inject PCE into the surficial aquifer cell created with two sets of sheet piles driven into an underlying clay unit. The well-controlled conditions specific to this experiment allowed quantification of mass balances, which is problematic for many contaminated field sites. The fact that mass balances can be obtained provides the ability to determine remediation effectiveness with unusual accuracy for a field project. The saturated zone within the test cell was flushed with a 15 wt % cyclodextrin solution. The cyclodextrin solution increased the aqueous concentration of PCE in the extraction-well effluent to as much as 22 times the concentrations obtained during the water flush conducted prior to the complexing sugar flush (CSF). The seven pore-volume CSF removed the equivalent of approximately 33 L of PCE from the subsurface. This equates to 48% of the total initial mass, based on the volume of PCE present prior to the CSF (68.6 L). Conversely, the seven pore-volume water flush conducted prior to the CSF removed the equivalent of 2.7 L of PCE. The use of cyclodextrin as a flushing agent, especially in a recycling configuration, appears to hold promise for successful remediation of chlorinated-solvent-contaminated source zones. 相似文献