全文获取类型
收费全文 | 1375篇 |
免费 | 48篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 7篇 |
综合类 | 3篇 |
化学工业 | 355篇 |
金属工艺 | 14篇 |
机械仪表 | 19篇 |
建筑科学 | 80篇 |
矿业工程 | 2篇 |
能源动力 | 31篇 |
轻工业 | 245篇 |
水利工程 | 6篇 |
石油天然气 | 4篇 |
无线电 | 78篇 |
一般工业技术 | 187篇 |
冶金工业 | 243篇 |
原子能技术 | 5篇 |
自动化技术 | 146篇 |
出版年
2023年 | 13篇 |
2022年 | 26篇 |
2021年 | 44篇 |
2020年 | 16篇 |
2019年 | 43篇 |
2018年 | 38篇 |
2017年 | 35篇 |
2016年 | 24篇 |
2015年 | 34篇 |
2014年 | 43篇 |
2013年 | 77篇 |
2012年 | 65篇 |
2011年 | 93篇 |
2010年 | 68篇 |
2009年 | 69篇 |
2008年 | 83篇 |
2007年 | 74篇 |
2006年 | 48篇 |
2005年 | 59篇 |
2004年 | 48篇 |
2003年 | 31篇 |
2002年 | 46篇 |
2001年 | 25篇 |
2000年 | 20篇 |
1999年 | 26篇 |
1998年 | 51篇 |
1997年 | 25篇 |
1996年 | 16篇 |
1995年 | 24篇 |
1994年 | 20篇 |
1993年 | 15篇 |
1992年 | 22篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 10篇 |
1985年 | 4篇 |
1984年 | 9篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1971年 | 3篇 |
1969年 | 2篇 |
1958年 | 1篇 |
排序方式: 共有1425条查询结果,搜索用时 15 毫秒
31.
Layered and homogeneous gelatin gels with controlled rheological properties were compared for their sensory characteristics, specifically sweetness, hardness, breakdown behaviour and frothing. All gels and layers had a gelatin/water concentration of 5%. The total sugar concentration was 9% in the layered samples and 0, 9, 15 or 22.5% in the homogeneous samples. These concentrations corresponded to the concentrations in the single layers.A seven-layered sample with different sugar concentrations in the layers gave a higher early sweetness intensity than a homogeneous gel with the same mean total sugar concentration. All layered gels were similar in hardness, breakdown behaviour and frothing; for the homogenous samples, sensory hardness was decreased in samples with much sugar. These gels also fell into smaller pieces than the sugarless sample. This study shows that it is possible by controlling the sugar distribution within a sample to produce sweeter gels while the sugar content is maintained. 相似文献
32.
An unconventional strategy of screening food microbes for biocontrol activity was used to develop biocontrol agents for controlling post-harvest peach brown rot caused by Monilinia fructicola. Forty-four microbial isolates were first screened for their biocontrol activity on apple fruit. Compared with the pathogen-only check, seven of the 44 isolates reduced brown rot incidence by >50%, including four bacteria: Bacillus sp. C06, Lactobacillus sp. C03-b and Bacillus sp. T03-c, Lactobacillus sp. P02 and three yeasts: Saccharomyces delbrueckii A50, S. cerevisiae YE-5 and S. cerevisiae A41. Eight microbial isolates were selected for testing on peaches by wound co-inoculation with mixtures of individual microbial cultures and conidial suspension of M. fructicola. Only two of them showed significant biocontrol activity after five days of incubation at 22 degrees C. Bacillus sp. C06 suppressed brown rot incidence by 92% and reduced lesion diameter by 88% compared to the pathogen-only check. Bacillus sp.T03-c reduced incidence and lesion diameter by 40% and 62%, respectively. The two isolates were compared with Pseudomonas syringae MA-4, a biocontrol agent for post-harvest peach diseases, by immersing peaches in an aliquot containing individual microbial isolates and the pathogen conidia. Treatments with isolates MA-4, C06 and T03-c significantly controlled brown rot by 91, 100, and 100% respectively. However, only isolates MA-4 and C06 significantly reduced brown rot by 80% and 15%, respectively when bacterial cells alone were applied. On naturally infected peaches, both the bacterial culture and its cell-free filtrate of the isolate C06 significantly controlled peach decay resulting in 77 and 90% reduction, respectively, whereas the treatment using only the bacterial cells generally had no effect. Isolate C06 is a single colony isolate obtained from a mesophilic cheese starter, and has been identified belonging to Bacillus amyloliquefaciens. The results have clearly demonstrated that isolate C06 has a great potential for being developed into a biocontrol agent. 相似文献
33.
Mixtures of sewage sludge, waste oil sludge, and metal oil sludge were prepared and carbonized at 950 degrees C in an inert atmosphere. Dynamic adsorption of H2S was measured on the materials obtained, and the breakthrough capacity was calculated. The initial and exhausted adsorbents after the breakthrough tests were characterized using sorption of nitrogen, thermal analysis, and XRF, XRD, and surface pH measurements. Mixing sludges leads to very high capacity adsorbents on which hydrogen sulfide is oxidized to elemental sulfur. Although the micropore volume of the adsorbents obtained is not high, their high volume of mesopores contributes significantly to reactive adsorption and provides space to store the oxidation products. The H2S breakthrough capacity on the new materials reaches 10 wt %. These adsorbents work until all active pores are filled and the catalytic centers are exhausted. The reason for such high capacity is in the formation of catalytically active mineral like phases during pyrolysis in the presence of nitrogen and carbon. This highly dispersed phase provides basicity and catalytic centers for hydrogen sulfide dissociation and its oxidation to sulfur. 相似文献
34.
Lea Melzener Karin E Verzijden A Jasmin Buijs Mark J Post Joshua E Flack 《Journal of the science of food and agriculture》2021,101(1):7-14
Cultured meat is an emerging technology with the potential to solve huge challenges related to the environmental, ethical, and health implications of conventional meat production. Establishing the basic science of cultured meat has been the primary focus of the last decade but it is now feasible that cultured meat products will enter the market within the next 3 to 4 years. This proximity to market introduction demands an evaluation of aspects of the cultured meat production process that have not yet been outlined or discussed in significant detail. For example, one technological approach for the production of cultured meat uses adult muscle stem cells, the limited proliferative capacity of which necessitates repeated collection of tissue samples via biopsies of living donor animals. The selection of donor animals and the details of biopsy processes must be optimized, as this is a key bottleneck in the cultured meat production process. The number of stem cells harvested from a biopsy, together with their proliferative capacity, determines a ‘multiplicity factor’ achieved by a cultured meat production process, thus dictating the reduction in number of animals required to produce a given quantity of meat. This article considers potential scenarios for these critical upstream steps, focusing on the production of cultured beef as an example. Considerations related to donor selection and details of the biopsy process are discussed in detail. The practicalities of various scenarios for cultured beef production, the health of donor animals, and regulatory issues associated with the safety of cultured meat for consumers are also considered. © 2020 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. 相似文献
35.
Recent evidence suggests that chronic nonparanoid schizophrenics show a narrowed range of cue utilization, especially when cues from more than 1 sensory modality are task relevant. In the present study with 20 male nonparanoid schizophrenic inpatients, it was hypothesized that this deficit can be ameliorated. All Ss were given premeasures of narrowed cue utilization on 2 dual modality tasks. Experimental Ss were then given contingent reinforcement and feedback on 2 tasks, while controls received nonreinforced practice on 1 task and no practice on the other. The major hypothesis was supported; experimental Ss improved (i.e., broadened) significantly more than controls on both tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
36.
37.
Joan E. Haysom Omid Jafarieh Hanan Anis Karin Hinzer David Wright 《Progress in Photovoltaics: Research and Applications》2015,23(11):1678-1686
Price declines and volume growth of concentrated photovoltaic (CPV) systems are analysed using the learning curve methodology and compared with other forms of solar electricity generation. Logarithmic regression analysis determines a learning rate of 18% for CPV systems with 90% confidence of that rate being between 14 and 22%, which is higher than the learning rates of other solar generation systems (11% for CSP and 12 to 14% for PV). Current CPV system prices are competitive with PV and CSP, which, when combined with the higher learning rate, indicates that CPV is likely to further improve its marketability. A target price of 1 $/W in 2020 could be achieved with a compound growth rate of 67% for the total deployed volume between 2014 and 2020, which would realize a cumulative deployed volume of 7900 MW. Other projections of deployment volumes from commercial sources are converted using the learning rate into future price scenarios, resulting in predicted prices in the range of 1.1 to 1.3 $/W in 2020. © 2014 The Authors. Progress in Photovoltaics: Research and Applications published by John Wiley & Sons Ltd. 相似文献
38.
Karin Schwarz Hedda Ernst Waldemar Ternes 《Journal of the science of food and agriculture》1996,70(2):217-223
The non-polar fraction of thyme was examined for the occurrence of phenolic components and their antioxidative activity. In addition to carvacrol ( II ) and thymol ( III ), p -cymene-2,3-diol (I ; 2,3-dihydroxy-4-isopropyl-1-methylbenzene) was isolated for the first time from thyme. The structure of I was elucidated using 1H nuclear magnetic resonance (NMR), 13C NMR, and mass spectrometry. Antioxidative activity was investigated with the Rancimat method (100°C) and the Schaal test (60°C). Compound I exhibited the strongest antioxidative activity which was greater than that of α-tocopherol and butylated hydroxyanisole. Five thyme species were analysed by means of HPLC with electrochemical detection for the concentration of compounds I – III . The highest amounts of I – III were found in Thymus vulgaris L. 相似文献
39.
The influence of extraction of reinforced fibres on surface properties and the curing reaction of epoxy resin matrix in composites were investigated. With increasing fibre surface polarity, as the result of the extraction, the resin wettability was improved and the reaction rate of curing of the epoxy resin matrix increased. The wettability and the reaction rate oppositely decreased with decreasing fibre surface polarity. 相似文献
40.
The reduction in the molecular weight distribution during acid hydrolysis of ordinary and waxy maize starch occured in two stages: first amylopectin degraded to intermediate high molecular weight polysac-charides, secondly, these were further hydrolyzed. The amylose moiety of ordinary and high-amylose starch was not affected very much by the hydrolysis conditions used (0.1–1 M HCI, 40°C, 0.3–4 h), but the gelling properties of starch weakened. The amylopectin degradation products, probably branched dextrins, were shown to hinder the gel formation of amylose in the starch pastes. 相似文献