全文获取类型
收费全文 | 262篇 |
免费 | 16篇 |
专业分类
化学工业 | 94篇 |
金属工艺 | 2篇 |
机械仪表 | 6篇 |
建筑科学 | 8篇 |
能源动力 | 1篇 |
轻工业 | 77篇 |
无线电 | 11篇 |
一般工业技术 | 36篇 |
冶金工业 | 15篇 |
自动化技术 | 28篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 12篇 |
2021年 | 19篇 |
2020年 | 11篇 |
2019年 | 9篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 11篇 |
2015年 | 14篇 |
2014年 | 14篇 |
2013年 | 21篇 |
2012年 | 15篇 |
2011年 | 26篇 |
2010年 | 17篇 |
2009年 | 12篇 |
2008年 | 13篇 |
2007年 | 15篇 |
2006年 | 15篇 |
2005年 | 6篇 |
2004年 | 8篇 |
2003年 | 3篇 |
2002年 | 1篇 |
2001年 | 4篇 |
1999年 | 1篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1988年 | 3篇 |
1985年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有278条查询结果,搜索用时 15 毫秒
41.
Caroprese M Annicchiarico G Schena L Muscio A Migliore R Sevi A 《The Journal of dairy research》2009,76(1):66-73
The experiment used 45 Comisana ewes, divided into 3 groups of 15. The aim was to determine the effects of two different stocking densities and two different housing conditions on welfare, and on production performance of dairy ewes. The stocking densities tested were: high stocking density (1 x 5 m2/ewe, HD group) and low stocking density (3 m2/ewe, LD group); the two housing conditions tested were: ewes housed indoors (LD group, 3 m2/ewe) and ewes allowed to use an outdoor area (LDP group, 3 m2/ewe divided into 1 x 5 m2/ewe indoors and 1 x 5 m2/ewe outdoors). At the beginning of the experiment, and then every 2 months, the cell-mediated immune status of sheep was evaluated. One month after the beginning of the experiment, and 20 d later, the ewes were injected with chicken egg albumin (OVA) to assess their humoural immune responses. Starting from the beginning of the experiment and then monthly, behavioural activities of ewes were monitored using 15-min scans. After lamb weaning, milk yield from individual ewes was measured and milk composition analysed weekly. Housing conditions (low density reared ewes indoors v. low density reared ewes with free access to an outdoor area) affected cell-mediated response, which was higher in LDP than in LD ewes. Concentrations of anti-OVA IgG were mainly influenced by space allowance, with higher antibody titres in LD than in HD ewes throughout the experiment. Both housing conditions and space allowance affected sheep behavioural activities: a greater proportion of LDP ewes displayed standing and drinking behaviours than LD ewes, and a greater proportion of LD ewes was observed walking than HD ewes. Ewes allowed access to the outdoor area had a higher protein content and lower somatic cell count in their milk, whereas reduced space allowance led to a reduction in milk yield and an increase in somatic cell count of milk. Results indicate that both increased space allowance and availability of outdoor area can improve the welfare and production performance of the lactating ewe. 相似文献
42.
This paper reports evidence from a survey, aimed at testing whether and how Information and Communication Technologies (ICTs), which enable the adoption of product-service systems, can contribute to value creation. This analysis builds on previous contributions, according to which companies that are enriching their product offering through value-added services (the so-called servitisation strategy) often report lower levels of profitability, owing to the poor performance of their operating process. A wide stream of research claims that companies that invest in ICTs can enjoy valuable outcomes, since the adoption of such technologies results in processes that are more efficient and more responsive. Our hypothesis concerns the possibility of leveraging ICTs at operating process level so as to pursue a servitisation strategy. The in-field analysis presented in this paper concerns a sample of 109 companies located in Italy; data collected through the survey have been analysed using the structural equation modelling approach. The evidence presented demonstrates that ICTs can have a relevant impact on value creation because they lead to superior responsiveness of operating processes and to sound improvements in the product offering. In particular, companies that are able to embed such superior responsiveness into their product offering can further boost value creation. 相似文献
43.
Yogurt-like beverages made of a mixture of cereals, soy and grape must: microbiology, texture, nutritional and sensory properties 总被引:2,自引:0,他引:2
Coda R Lanera A Trani A Gobbetti M Di Cagno R 《International journal of food microbiology》2012,155(3):120-127
Cereal (rice, barley, emmer and oat) and soy flours and concentrated red grape must were used for making vegetable yogurt-like beverages (VYLB). Two selected strains of Lactobacillus plantarum were used for lactic acid fermentation, according to a process which included the flour gelatinization. All VLYB had values of pH lower than 4.0 and both selected starters remained viable at ca. 8.4 log cfu/g throughout storage. All VLYB showed high values of apparent viscosity and water holding capacity. During fermentation, lactic acid bacteria consumed glucose, fructose, and malic acid, which was supplied with grape must. Compared to control vegetable yogurt-like beverages (CVYLB), without bacterial inoculum, an increase of total free amino acids (FAA) was found during fermentation and storage. Also the concentration of polyphenolic compounds and ascorbic acid (ASC) was higher in VLYB compared to CVYLB. This was reflected on the antioxidant activity. As determined by Solid Phase Micro-Extraction/Gas-Chromatography/Mass-Spectrometry analysis, several volatile compounds were identified. Beverages made with the mixture of rice and barley or emmer flours seemed to possess the best combination textural, nutritional and sensory properties. 相似文献
44.
Francesco Todescato Ilaria Fortunati Samuele Gardin Eleonora Garbin Elisabetta Collini Renato Bozio Jacek J. Jasieniak Gioia Della Giustina Giovanna Brusatin Stefano Toffanin Raffaella Signorini 《Advanced functional materials》2012,22(2):337-344
The development of a solution‐deposited up‐converted distributed feedback laser prototype is presented. It employs a sol–gel silica/germania soft‐lithographed microcavity and CdSe–CdZnS–ZnS quantum dot/sol–gel zirconia composites as optical gain material. Characterization of the linear and nonlinear optical properties of quantum dots establishes their high absorption cross‐sections in the one‐ and two‐ photon absorption regimes to be 1 × 10?14 cm2 and 5 × 104 GM, respectively. In addition, ultrafast transient absorption dynamics measurements of the graded seal quantum dots reveal that the Auger recombination lifetime is 220 ps, a value two times higher than that of the corresponding CdSe core. These factors enable the use of such quantum dots as optically pumped gain media, operating in the one‐ and two‐photon absorption regime. The incorporation of CdSe–CdZnS–ZnS quantum dots within a zirconia host matrix affords a quantum‐dot ink that can be directly deposited on our soft‐lithographed distributed feedback grating to form an all‐solution‐processed microcavity laser. 相似文献
45.
Recently, giant carrier mobility μ (>10(5) cm(2) V(-1) s(-1)) and micrometer electron mean free path (l) have been measured in suspended graphene or in graphene encapsulated between inert and ultraflat BN layers. Much lower μ values (10000-20000 cm(2) V(-1) s(-1)) are typically reported in graphene on common substrates (SiO(2), SiC) used for device fabrication. The debate on the factors limiting graphene electron mean free path is still open with charged impurities (CI) and resonant scatterers (RS) indicated as the most probable candidates. As a matter of fact, the inhomogeneous distribution of such scattering sources in graphene is responsible of nanoscale lateral inhomogeneities in the electronic properties, which could affect the behavior of graphene nanodevices. Hence, high resolution two-dimensional (2D) mapping of their density is very important. Here, we used scanning capacitance microscopy/spectroscopy to obtain 2D maps of l in graphene on substrates with different dielectric permittivities, that is, SiO(2) (κ(SiO2) = 3.9), 4H-SiC (0001) (κ(SiC) = 9.7) and the very-high-κ perovskite strontium titanate, SrTiO(3) (001), briefly STO (κ(STO) = 330). After measuring l versus the gate bias V(g) on an array of points on graphene, maps of the CI density (N(CI)) have been determined by the neutrality point shift from V(g) = 0 V in each curve, whereas maps of the RS density (N(RS)) have been extracted by fitting the dependence of l on the carrier density (n). Laterally inhomogeneous densities of CI and RS have been found. The RS distribution exhibits an average value ~3 × 10(10) cm(-2) independently on the substrate. For the first time, a clear correlation between the minima in the l map and the maxima in the N(CI) map is obtained for graphene on SiO(2) and 4H-SiC, indicating that CI are the main source of the lateral inhomogeneity of l. On the contrary, the l and N(CI) maps are uncorrelated in graphene on STO, while a clear correlation is found between l and N(RS) maps. This demonstrates a very efficient dielectric screening of CI in graphene on STO and the role of RS as limiting factor for electron mean free path. 相似文献
46.
Gardin S Della Giustina G Brusatin G Signorini R 《Journal of nanoscience and nanotechnology》2011,11(1):195-199
Hybrid SiO2-TiO2 films are prepared starting from tetraisopropoxy titanate and 3-glycidoxipropyltrimethoxysilane, using the sol-gel process. During the sol synthesis titania clusters grow, conferring to the samples a photocatalytic activity. In this paper we exploit this property for the fabrication of surface-relief gratings. The realized structures are characterized by SEM, AFM and profilometric measurements, while the presence of titania clusters is confirmed by TEM analyses. 相似文献
47.
Coda R Di Cagno R Rizzello CG Nionelli L Edema MO Gobbetti M 《Journal of food science》2011,76(6):M329-M335
Abstract: Acha and Iburu flours were singly subjected to sourdough fermentation with previously selected autochthonous starters. Sourdoughs were used (30%, wt/wt) as aroma carriers and acidifiers during short time fermentation with the addition of baker's yeast. Acha and Iburu sourdough breads were compared to wheat sourdough bread started with the same strains and to breads made with the same formula but using baker's yeast alone. During Acha and Iburu sourdough fermentations, starter lactic acid bacteria reached almost the same cell density found in wheat sourdoughs. Acidification was more intense. Iburu sourdough bread had the highest total titratable acidity, the lowest pH, and contained the highest levels of free amino acids and phytase activity. The values of in vitro protein digestibility did not differ between Acha sourdough and wheat sourdough breads, while Iburu sourdough bread showed a slightly lower value. Acha and Iburu sourdough breads showed lower specific volume and higher density with respect to wheat sourdough breads. Nevertheless, Acha and Iburu sourdough breads were preferred for hardness and resilience. As shown by sensory analysis, Acha and especially Iburu sourdough breads were appreciated for color, acid taste and flavor, and overall acceptability. Practical Application: This study was aimed at evaluating the technological and nutritional properties of the African cereals Acha and Iburu. Sourdough fermentation and the use of selected starters increased the nutritional and sensory qualities and the potential application for bakery industry. 相似文献
48.
Sara Federici Floriana Ciarrocchi Raffaella Campana Eleonora Ciandrini Giuliana Blasi Wally Baffone 《Meat science》2014
Lactic acid bacteria (LAB) from Ciauscolo salami produced in Marche Region of Central Italy, and LAB strains belonging to our laboratory collection were examined for their capability to survive at low pH and bile, to adhere to Caco-2 cells, and for antibiotic resistance. LAB from Ciauscolo were identified by ARDRA and RAPD-PCR. Our study showed that all LAB strains had good adaptation to gastric juice and moderate tolerance to bile. The adhesiveness was variable among strains but significantly lower in LAB from food. Antibiotic resistance was broadly spread among food strains, with level of resistance exceeding 15% for all the antibiotics tested. The resistance determinants erm(B) and tet(M) were found in nine strains of food origin (21.4%) while tet(L) in one strain of our collection (5%). Our work suggests that fermented foods are valuable sources of bacterial strains with functional traits of intestinal lactobacilli. These bacteria may be further studied for their use in probiotic applications. 相似文献
49.
Margherita Durso Cristian Bettini Alberto Zanelli Massimo Gazzano M. Grazia Lobello Filippo De Angelis Viviana Biondo Denis Gentili Raffaella Capelli Massimiliano Cavallini Stefano Toffanin Michele Muccini Manuela Melucci 《Organic Electronics》2013,14(11):3089-3097
The synthesis of two new thieno(bis)imide (TBI, N) end functionalized oligothiophene semiconductors is reported. In particular, trimer (NT3N) and pentamer (NT5N) have been synthesized and characterized. Two different synthetic approaches for their preparation were tested and compared namely conventional Stille cross coupling and direct arylation reaction via C–H activation. Theoretical calculations, optical and electrochemical characterization allowed us to assess the role of the π-conjugation extent, i.e., of the oligomer size on the optoelectronic properties of these materials. In both TBI ended compounds, due to the strong localization of the LUMO orbital on the TBI unit, the LUMO energy is almost insensitive to the oligomer size, this being crucial for the fine-tailoring of the energy and the distribution of the frontier orbitals. Surprisingly, despite its short size and contrarily to comparable TBI-free analogues, NT3N shows electron charge transport with mobility up to μN = 10−4 cm2 V−1 s−1, while increasing the oligomer size to NT5N promotes ambipolar behavior and electroluminescence properties with mobility up to μN = 0.14 cm2 V−1 s−1 and to μP = 10−5 cm2 V−1 s−1. 相似文献
50.
Paola Zunin Raffaella Boggia Filippo Evangelisti 《Journal of the American Oil Chemists' Society》2001,78(10):1037-1040
Cholesterol oxidation in tuna canned in brine was studied. Gas chromatography-mass spectrometry was used for the detection
of the seven major cholesterol oxidation products originating from both direct and indirect oxidation. The total amount of
cholesterol oxidation products in the analyzed samples varied considerably, ranging between 40 and 350 μg/g lipids, with the
exception of an anomalous sample, that reached a 1600 μg/g level. The lipid content ranged between 0.5 and 1 g/100 g wet product.
As most samples did not exceed 100 μg/g lipids, it is possible to assume that the total content of cholesterol oxidation products
can be kept below this value if good manufacturing conditions are used, together with a careful choice of the best tuna cuts.
The application of principal component analysis to the detected variables confirmed that 7-ketocholesterol is a useful index
of the whole oxidation process. 相似文献