首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   483篇
  免费   35篇
电工技术   7篇
综合类   3篇
化学工业   110篇
金属工艺   1篇
机械仪表   4篇
建筑科学   23篇
矿业工程   3篇
能源动力   4篇
轻工业   207篇
石油天然气   1篇
无线电   14篇
一般工业技术   64篇
冶金工业   36篇
原子能技术   1篇
自动化技术   40篇
  2023年   9篇
  2022年   13篇
  2021年   24篇
  2020年   3篇
  2019年   11篇
  2018年   11篇
  2017年   8篇
  2016年   22篇
  2015年   18篇
  2014年   30篇
  2013年   21篇
  2012年   31篇
  2011年   34篇
  2010年   27篇
  2009年   29篇
  2008年   28篇
  2007年   21篇
  2006年   23篇
  2005年   26篇
  2004年   20篇
  2003年   19篇
  2002年   18篇
  2001年   8篇
  2000年   6篇
  1999年   4篇
  1998年   11篇
  1997年   9篇
  1996年   6篇
  1995年   7篇
  1994年   3篇
  1993年   1篇
  1992年   1篇
  1991年   1篇
  1990年   5篇
  1988年   1篇
  1987年   2篇
  1983年   1篇
  1982年   2篇
  1978年   1篇
  1977年   1篇
  1976年   2篇
排序方式: 共有518条查询结果,搜索用时 15 毫秒
71.
The effect of a controlled lactic fermentation on textural and ultrastructural properties of salmon fillets was evaluated. When compared with a non‐inoculated cured sample, fermented salmon had unique textural properties since it exhibited significantly higher force (p < 0.05) and work (p < 0.001) values in a penetration test on two sampling days but a consistently lower hardness (p < 0.05) in a Texture Profile Analysis (TPA) rheological test. Study of the myofibrillar ultrastructure showed that basic structures were drastically damaged during processing and storage of fermented and cured salmon. Nevertheless, Z‐lines were better preserved in fermented samples. It is suggested that the slight protective effect of lactic fermentation with the starter L sake may be the consequence of a lower pH, by putatively inhibiting neutral or alkaline proteolytic enzymes. © 2000 Society of Chemical Industry  相似文献   
72.
Six colour-flowering (Scirocco, Alfred, Carola, Condor, Tina and Herz Freya) and six white-flowering (Caspar, Albatros, Gloria, Tyrol, Vasco and Cresta) cultivars of Vicia faba were studied. The crude protein contents of colour- and white-flowering cultivars were 267±13·6 and 283±18·8 g kg−1, respectively, which did not differ significantly at P<0·05. The levels of lipids, crude fibre, starch and ash varied from 14 to 22 g kg−1, 88 to 143 g kg−1, 407 to 485 g kg−1 and 32 to 42 g kg−1, respectively. The calculated organic matter digestibility (OMD) and metabolisable energy (ME) of the white-flowering cultivars were significantly higher (P<0·001) than those of the colour-flowering cultivars (OMD: 889·1±26·6 g kg−1 vs 797·5±17·1 g kg−1; ME: 13·97±0·49 vs 12·30±0·34 MJ kg−1). In all cultivars, sulphur amino acids were lower than adequate concentration when compared with recommended amino acid pattern of FAO/WHO/UNO reference protein for a 2–5-year-old child. The in vitro rumen nitrogen degradability of colour-flowering cultivars was significantly lower (P<0·01) compared to that of white-flowering cultivars (71·4±9·3% vs 88·0±11·1%). Amongst colour-flowering varieties, the contents of total phenols (TP), tannins (T) and condensed tannins (CT) were highest in Alfred (28·3, 21·0 and 35·4 g kg−1, respectively). The contents of TP and T were similar (about 15 and 10 g kg−1, respectively) in Carola, Tina and Herz Freya, and the CT were in the order: Condor>Herz Freya>Carola. The CT were not detected in white-flowering varieties, T were virtually absent and TP were extremely low (4·0–4·9 g kg−1). The activities of other antinutritional factors (white- and colour-flowering cultivars, respectively: trypsin inhibitor activity 3·05±0·34 and 1·85±0·09 mg trypsin inhibited g−1; lectin 27·2±9·4 and 27·1±5·1 mg ml−1 assay medium producing haemagglutination; phytate 15·0±2·7 and 16·6±2·3 g kg−1) were very low. A strong negative correlation (r=-0·92, P<0·001) between tannins and in vitro rumen protein degradability was observed which suggested that tannins have adverse effect on protein degradability. Similarly negative correlations between tannin levels and metabolisable energy (r=-0·89; P<0·001) and organic matter digestibility (r=-0·89; P<0·001) were observed. The correlation coefficient between trypsin inhibitor activity and tannins was negative and highly significant (r=-0·88, P<0·001), whereas between tannins and saponins it was significantly positive (r=0·96, P<0·001). ©1997 SCI  相似文献   
73.

1 Scope

Ginger is reported to be used for the prevention and treatment of cardiovascular diseases (CVD). Cholesterol efflux from macrophage foam cells is an important process in reverse cholesterol transport, whose increase may help to prevent or treat CVD. In this study, we investigated the effects of 6‐dihydroparadol from ginger on macrophage cholesterol efflux.

2 Methods and results

We show that 6‐dihydroparadol concentration‐dependently enhances both apolipoprotein A1‐ and human plasma–mediated cholesterol efflux from cholesterol‐loaded THP‐1‐derived macrophages using macrophage cholesterol efflux assay. 6‐Dihydroparadol increases protein levels of both ATP‐binding cassette transporters A1 and G1 (ATP‐binding cassette transporter A1 [ABCA1] and ATP‐binding cassette transporter G1 [ABCG1]) according to Western blot analysis. The ABCA1 inhibitor probucol completely abolishes 6‐dihydroparadol‐enhanced cholesterol efflux. Furthermore, increased ABCA1 protein levels in the presence of 6‐dihydroparadol were associated with both increased ABCA1 mRNA levels and increased ABCA1 protein stability. Enhanced ABCG1 protein levels were only associated with increased protein stability. Increased ABCA1 protein stability appeared to be the result of a reduced proteasomal degradation of the transporter in the presence of 6‐dihydroparadol.

3 Conclusion

We identified 6‐dihydroparadol from ginger as a novel promoter of cholesterol efflux from macrophages that increases both ABCA1 and ABCG1 protein abundance. This newly identified bioactivity might contribute to the antiatherogenic effects of ginger.  相似文献   
74.
本研究的目的在于开发利用超声喷嘴浸渍纺织材料的新方法,使纺织品具有既定的功能性,并为进一步应用纳米技术以获得功能化产业用纺织品,以及服装用和装饰用纺织品打下技术基础。  相似文献   
75.
76.
Currently, comparison between countries in terms of their road safety performance is widely conducted in order to better understand one's own safety situation and to learn from those best-performing countries by indicating practical targets and formulating action programmes. In this respect, crash data such as the number of road fatalities and casualties are mostly investigated. However, the absolute numbers are not directly comparable between countries. Therefore, the concept of risk, which is defined as the ratio of road safety outcomes and some measure of exposure (e.g., the population size, the number of registered vehicles, or distance travelled), is often used in the context of benchmarking. Nevertheless, these risk indicators are not consistent in most cases. In other words, countries may have different evaluation results or ranking positions using different exposure information. In this study, data envelopment analysis (DEA) as a performance measurement technique is investigated to provide an overall perspective on a country's road safety situation, and further assess whether the road safety outcomes registered in a country correspond to the numbers that can be expected based on the level of exposure. In doing so, three model extensions are considered, which are the DEA based road safety model (DEA-RS), the cross-efficiency method, and the categorical DEA model. Using the measures of exposure to risk as the model's input and the number of road fatalities as output, an overall road safety efficiency score is computed for the 27 European Union (EU) countries based on the DEA-RS model, and the ranking of countries in accordance with their cross-efficiency scores is evaluated. Furthermore, after applying clustering analysis to group countries with inherent similarity in their practices, the categorical DEA-RS model is adopted to identify best-performing and underperforming countries in each cluster, as well as the reference sets or benchmarks for those underperforming ones. More importantly, the extent to which each reference set could be learned from is specified, and practical yet challenging targets are given for each underperforming country, which enables policymakers to recognize the gap with those best-performing countries and further develop their own road safety policy.  相似文献   
77.
Secondary protonated calcium phosphates such as brushite (CaHPO4·2H2O) or monetite (CaHPO4) have a higher resorption potential in bone defects than sintered ceramics, e.g. tricalcium phosphate or hydroxyapatite. However, processing of these phosphates to monolithic blocks or granules is not possible by sintering due to thermal decomposition of protonated phosphates at higher temperatures. In this study a low temperature technique for the preparation of spherical brushite granules in a cement setting reaction is presented. These granules were synthesized by dispersing a calcium phosphate cement paste composed of β-tricalcium phosphate and monocalcium phosphate together with a surfactant to an oil/water emulsion. The reaction products were characterized regarding their size distribution, morphology, and phase composition. Clinically relevant granule sizes ranging from 200?μm to 1?mm were obtained, whereas generally smaller granules were received with higher oil viscosity, increasing temperature or higher powder to liquid ratios of the cement paste. The hardened granules were microporous with a specific surface area of 0.7?m2/g and consisted of plate-like brushite (>95?% according to XRD) crystals of 0.5–7?μm size. Furthermore it was shown that the granules may be also used for drug delivery applications. This was demonstrated by adsorption of vancomycin from an aqueous solution, where a load of 1.45–1.88?mg drug per g granules and an almost complete release within 2?h was obtained.  相似文献   
78.
A combined experimental and theoretical study is presented revealing the influence of metal–molecule coupling on electronic transport through single‐molecule junctions. Transport experiments through tolane molecules attached to gold electrodes via thiol, nitro, and cyano anchoring groups are performed. By fitting the experimental current–voltage characteristics to a single‐level tunneling model, we extract both the position of the molecular orbital closest to the Fermi energy and the strength of the metal–molecule coupling. The values found for these parameters are rationalized with the help of density‐functional‐theory‐based transport calculations. In particular, these calculations show that the anchoring groups determine the junction conductance by controlling not only the strength of the coupling to the metal but also the position of the relevant molecular energy levels.  相似文献   
79.
80.
A systematic study on the comminution of amorphous glass particles with complex composition (seven constituents) to produce nanoparticles has been performed in a high-energy stirred media mill. The influence of solids loading, dispersion stabilisation via pH and addition of dispersants on particle size was investigated in aqueous suspensions. Further, the effect of using 2-propanol and benzyl alcohol as dispersion media on the particle size and morphology is presented and compared to the aqueous system. The specific surface area of the product powder was analysed by the BET method, the secondary particle size was determined by static light scattering and the morphology was investigated by SEM and TEM. Dispersion viscosity and stability was measured using rotational viscosimetry and zeta-potential measurements, respectively. The results show that the solids loading plays a central role in the comminution efficiency, where lower loadings lead to finer particles after a given milling time. Stabilisation of the aqueous powder dispersion by adjusting the pH or by adding a dispersant did not result in an enhanced milling efficiency in terms of fast reduction of the particle size. The smallest glass nanoparticles with a primary particle size were achieved by a two-step comminution process. The particles were irregularly shaped when milled in water, however, when processed in 2-propanol and benzyl alcohol, they had a plate-like geometry.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号