全文获取类型
收费全文 | 903篇 |
免费 | 3篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 1篇 |
综合类 | 1篇 |
化学工业 | 40篇 |
金属工艺 | 2篇 |
机械仪表 | 42篇 |
建筑科学 | 25篇 |
矿业工程 | 20篇 |
轻工业 | 278篇 |
水利工程 | 4篇 |
石油天然气 | 1篇 |
武器工业 | 2篇 |
无线电 | 36篇 |
一般工业技术 | 423篇 |
冶金工业 | 11篇 |
原子能技术 | 2篇 |
自动化技术 | 19篇 |
出版年
2024年 | 1篇 |
2019年 | 1篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2013年 | 1篇 |
2012年 | 93篇 |
2011年 | 130篇 |
2010年 | 30篇 |
2009年 | 2篇 |
2008年 | 97篇 |
2007年 | 96篇 |
2006年 | 62篇 |
2005年 | 50篇 |
2004年 | 54篇 |
2003年 | 57篇 |
2002年 | 51篇 |
2001年 | 27篇 |
2000年 | 29篇 |
1999年 | 12篇 |
1998年 | 19篇 |
1997年 | 14篇 |
1996年 | 14篇 |
1995年 | 15篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1987年 | 2篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1978年 | 1篇 |
1967年 | 1篇 |
1958年 | 3篇 |
1957年 | 4篇 |
1956年 | 2篇 |
1955年 | 3篇 |
1954年 | 1篇 |
1948年 | 1篇 |
排序方式: 共有907条查询结果,搜索用时 0 毫秒
901.
Effects of fatty acids on meat quality: a review 总被引:14,自引:0,他引:14
Wood JD Richardson RI Nute GR Fisher AV Campo MM Kasapidou E Sheard PR Enser M 《Meat science》2004,66(1):21-32
Interest in meat fatty acid composition stems mainly from the need to find ways to produce healthier meat, i.e. with a higher ratio of polyunsaturated (PUFA) to saturated fatty acids and a more favourable balance between n-6 and n-3 PUFA. In pigs, the drive has been to increase n-3 PUFA in meat and this can be achieved by feeding sources such as linseed in the diet. Only when concentrations of α-linolenic acid (18:3) approach 3% of neutral lipids or phospholipids are there any adverse effects on meat quality, defined in terms of shelf life (lipid and myoglobin oxidation) and flavour. Ruminant meats are a relatively good source of n-3 PUFA due to the presence of 18:3 in grass. Further increases can be achieved with animals fed grain-based diets by including whole linseed or linseed oil, especially if this is "protected" from rumen biohydrogenation. Long-chain (C20-C22) n-3 PUFA are synthesised from 18:3 in the animal although docosahexaenoic acid (DHA, 22:6) is not increased when diets are supplemented with 18:3. DHA can be increased by feeding sources such as fish oil although too-high levels cause adverse flavour and colour changes. Grass-fed beef and lamb have naturally high levels of 18:3 and long chain n-3 PUFA. These impact on flavour to produce a 'grass fed' taste in which other components of grass are also involved. Grazing also provides antioxidants including vitamin E which maintain PUFA levels in meat and prevent quality deterioration during processing and display. In pork, beef and lamb the melting point of lipid and the firmness/hardness of carcass fat is closely related to the concentration of stearic acid (18:0). 相似文献
902.
A novel application of single particle scanning transmission X-ray microscopy (STXM) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy is presented for quantitative analysis of hygroscopic properties and phase transitions of individual submicrometer particles. The approach utilizes the exposure of substrate-deposited individual particles to water vapor at different relative humidity followed by STXM/NEXAFS spectromicroscopy analysis. The hygroscopic properties of atmospherically relevant NaCl, NaBr, NaI, and NaNO(3) submicrometer particles were measured to evaluate the utility of the approach. An analytical approach for quantification of a water-to-solute ratio within an individual submicrometer particle during hydration and dehydration cycles is presented. The results for the deliquescence and efflorescence phase transitions and quantitative measurements of water-to-solute ratios are found in excellent agreement with available literature data. Oxygen K-edge NEXAFS spectra of submicrometer sodium halide droplets are reported along with a unique experimental observation of the formation of the halide-water anionic complex in NaBr and NaI microdimensional droplets. The analytical approach provides a unique opportunity for spectromicroscopy studies of water uptake on environmental particles collected in both laboratory and field studies. 相似文献
903.
The temperature dependence of laser-induced NO A (2)?(+)-X (2)? fluorescence in the hot gases of natural gas-air flames, seeded with known quantities of NO, has been determined experimentally by means of a difference method. The flame temperature at three fixed equivalence ratios was changed when the mixture velocity was varied through a water-cooled, flat-flame burner and was measured by coherent anti-Stokes Raman spectroscopy. When the possible reburning of part of the seeded NO is allowed for, the results in the range 1700-2150 K are best described by the temperature dependence obtained from a model in which quenching corrections are neglected, as in the case of a saturated two-level system, when millijoule pulse energies are used. Measurements of the fluorescence intensity at constant seed concentration as a function of equivalence ratio between 0.75 and 1.3 also indicate that quenching corrections are unnecessary under these excitation conditions. Using the measured intensities of the seeded flame as a calibration factor, we determined the absolute NO concentrations as functions of the equivalence ratio at 1 cm above the burner. The results indicate that, with the calibration method presented here, a relative accuracy of 5% should be obtainable. 相似文献
904.
Krishnamoorthy AV Ford JE Goossen KW Walker JA Lentine AL Hui SP Tseng B Chirovsky LM Leibenguth R Kossives D Dahringer D D'Asaro LA Kiamilev FE Aplin GF Rozier RG Miller DA 《Applied optics》1996,35(23):4637-4640
Owing to printing errors, [Appl. Opt. 35, 2439 (1996)] several figures were illegible. The figures are reprinted and briefly reviewed. 相似文献
905.
Pearce RC Vasenkov AV Hensley DK Simpson ML McKnight TE Melechko AV 《ACS applied materials & interfaces》2011,3(9):3501-3507
A key factor to the implementation of devices with vertically aligned carbon nanofibers (VACNFs) is fundamental understanding of how to control fluctuations in the growth direction of the fibers. Here we demonstrate synthesis of VACNF on transparent and insulating substrates by continuous direct current (DC) plasma for realization of cellular interface suitable for transmission optical microscopy. To maintain continuous glow discharge above the substrate, a metal grid electrode layer (Cr) was deposited over silica with windows of exposed silica ranging in size from 200 μm to 1 mm. This electrode geometry allows for synthesis of VACNFs even within an insulating window. This observation and the observed trends in the alignment of nanofibers in the vicinity of grid electrodes have indicated that the alignment does not correspond to the direction of the electric field at the substrate level, contrary to previously proposed alignment mechanism. Computational modeling of the plasma with this grid cathode geometry has shown that nanofiber alignment trends follow calculated ion flux direction rather than electrical field. The new proposed alignment mechanism is that ion sputtering of the carbon film on a catalyst particle defines the growth direction of the nanofibers. With this development, fiber growth direction can be better manipulated through changes in ionic flux direction, opening the possibility for growth of nanofibers on substrates with unique geometries. 相似文献
906.
Kronast F Friedenberger N Ollefs K Gliga S Tati-Bismaths L Thies R Ney A Weber R Hassel C Römer FM Trunova AV Wirtz C Hertel R Dürr HA Farle M 《Nano letters》2011,11(4):1710-1715
Correlating the electronic structure and magnetic response with the morphology and crystal structure of the same single ferromagnetic nanoparticle has been up to now an unresolved challenge. Here, we present measurements of the element-specific electronic structure and magnetic response as a function of magnetic field amplitude and orientation for chemically synthesized single Fe nanocubes with 18 nm edge length. Magnetic states and interactions of monomers, dimers, and trimers are analyzed by X-ray photoemission electron microscopy for different particle arrangements. The element-specific electronic structure can be probed and correlated with the changes of magnetic properties. This approach opens new possibilities for a deeper understanding of the collective response of magnetic nanohybrids in multifunctional materials and in nanomagnetic colloidal suspensions used in biomedical and engineering technologies. 相似文献
907.