全文获取类型
收费全文 | 3693篇 |
免费 | 89篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 30篇 |
化学工业 | 367篇 |
金属工艺 | 64篇 |
机械仪表 | 51篇 |
建筑科学 | 34篇 |
矿业工程 | 3篇 |
能源动力 | 74篇 |
轻工业 | 247篇 |
水利工程 | 8篇 |
石油天然气 | 17篇 |
无线电 | 191篇 |
一般工业技术 | 408篇 |
冶金工业 | 2039篇 |
原子能技术 | 12篇 |
自动化技术 | 242篇 |
出版年
2023年 | 13篇 |
2022年 | 27篇 |
2021年 | 29篇 |
2020年 | 33篇 |
2019年 | 39篇 |
2018年 | 60篇 |
2017年 | 43篇 |
2016年 | 49篇 |
2015年 | 45篇 |
2014年 | 69篇 |
2013年 | 114篇 |
2012年 | 118篇 |
2011年 | 132篇 |
2010年 | 113篇 |
2009年 | 117篇 |
2008年 | 107篇 |
2007年 | 88篇 |
2006年 | 88篇 |
2005年 | 60篇 |
2004年 | 64篇 |
2003年 | 46篇 |
2002年 | 48篇 |
2001年 | 37篇 |
2000年 | 28篇 |
1999年 | 99篇 |
1998年 | 623篇 |
1997年 | 384篇 |
1996年 | 264篇 |
1995年 | 154篇 |
1994年 | 127篇 |
1993年 | 129篇 |
1992年 | 22篇 |
1991年 | 37篇 |
1990年 | 24篇 |
1989年 | 41篇 |
1988年 | 32篇 |
1987年 | 31篇 |
1986年 | 25篇 |
1985年 | 33篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 12篇 |
1981年 | 12篇 |
1980年 | 16篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1977年 | 32篇 |
1976年 | 96篇 |
1975年 | 3篇 |
1955年 | 3篇 |
排序方式: 共有3787条查询结果,搜索用时 0 毫秒
991.
FJ Hou SM Lang SJ Hoshaw DA Reimann DP Fyhrie 《Canadian Metallurgical Quarterly》1998,31(11):1009-1015
Cancellous bone apparent stiffness and strength are dependent upon material properties at the tissue level and trabecular architecture. Microstructurally accurate, large-scale finite element (LS-FE) models were used to predict the experimental apparent stiffness of human vertebral cancellous bone and to estimate the trabecular hard tissue stiffness. Twenty-eight LS-FE models of cylindrical human vertebral cancellous bone specimens (8 mm in diameter, 9.5 mm in height, one each from twenty-eight individuals) were generated directly from microcomputed tomography images and solved by a special purpose iterative finite element program. The experimental apparent stiffness and strength of the specimens were determined by mechanical testing to failure in the infero superior direction. Morphometric measurements including bone volume fraction (BV/TV), three eigenvalues of the fabric tensor and average P(L) were also calculated. The finite element estimate of apparent stiffness explained much of the variance in both experimental apparent stiffness (r2=0.89) and experimental apparent strength (r2=0.87). Stepwise linear regression analysis demonstrated that the LS-FE estimated apparent stiffness was the only significant predictor of experimental apparent stiffness and strength when it was included with all measured morphometric values. Hard tissue stiffness was quite variable between individuals (mean, 5.7 GPa; S.D. 1.6 GPa), but was not significantly related to age, sex, race, weight or morphometric measures for this sample. 相似文献
992.
993.
994.
995.
Gustavo González‐Neves Guzmán Favre Diego Piccardo Graciela Gil 《International Journal of Food Science & Technology》2016,51(1):260-267
Anthocyanins are the main pigments of young red wines. The aim of this work was to evaluate the anthocyanin composition of red wines produced by alternative procedures of winemaking and different grape varieties. For this purpose, wines of Tannat, Syrah and Merlot were made by traditional maceration (TM), addition of maceration enzymes (ENZ) and cold soak (CS). Syrah wines had the highest proportions of malvidin (86.0 ± 1.0) and peonidin (5.5 ± 0.4), while Tannat wines had the highest of delphinidin (6.9 ± 0.8), petunidin (13.2 ± 0.6) and nonacylated glucosides (73.6 ± 0.6). Cold soak increased the anthocyanins contents in Tannat and Merlot wines. In turn, maceration enzymes affect the anthocyanin profile and the stability of the colour of wines. Discriminant analysis of data showed significant separation of the wines of each variety as the anthocyanin profile showed the varietal fingerprint, despite the different winemaking procedures. 相似文献
996.
Structural (XRD) and spectroscopic (EPR, IR and Raman) investigations were performed to elucidate the influence of CeO2 content on the phase composition and surface chemistry of CexZr1−xO2 solid solutions (x = 0.10–0.85), interacting with NO and NO2 in the absence and presence of oxygen. Strong influence of ceria loading on the adsorption modes of both nitrogen oxides and the nature of the resultant surface species was revealed. Adsorption of NO led to formation of mononitrosyl complexes, dimers and N2O, whereas interaction of NO2 with the ceria–zirconia catalyst resulted in the adsorbate disproportionation or coupling, depending on the sample composition. 相似文献
997.
Porous magnesium was produced through the thermal decomposition of various additives in an effort to increase hydrogen storage capacity. Samples were characterized using SANS and different theoretical models were applied to the results and discussed. The polydisperse self-assembled (PSA) model was found to best represent the scattering from these materials as this model incorporates the polydispersity of the pores and allows for variations in structure factor. Pure magnesium produced using the same thermal method absorbed a negligible amount of hydrogen, and hydrogen uptake was found to increase with increasing porosity as determined using the PSA model. Maximum hydrogen uptake (1.3%) was found when 0.3% Cs2CO3 and 0.5% Ni were combined as an additive during thermal treatment. In addition, the development of porosity was found to promote hydrogen desorption at lower temperatures. SANS represents an indispensible method by which to characterize materials and the PSA model described in this work has the potential to be extremely useful in the characterisation of porous metallic systems. 相似文献
998.
María Pérez‐Juan Carolina E. Realini Marta Barahona Maria Victoria Sarriés Maria del Mar Campo María José Beriain Mauro Vitale Marta Gil Pere Albertí 《Journal of food science》2014,79(11):S2377-S2382
The effect of different animal diets supplemented with linseed (source of omega‐3 fatty acids: n‐3) and/or conjugated linoleic acid (CON: control, LIN: 10% linseed, CLA: 2% conjugated linoleic acid, LINCLA: 10% linseed plus 2% CLA) on consumer liking of beef aged for 7 or 21 d was assessed in 3 Spanish cities. Overall, tenderness, juiciness, and flavor liking of beef were evaluated by consumers (n = 720) using 9‐point scales. Hedonic scores assigned by consumers did not differ (P > 0.05) for beef from animals fed the different diets and aged for 7 or 21 d. Consumer scores showed an increasing trend in beef liking with aging time. Consumers from Pamplona assigned lower (P < 0.05) hedonic scores for beef liking than consumers from Barcelona and Zaragoza. Linseed and/or CLA can be fed to improve the fatty acid profile in beef with minimal impact on consumer liking. Consumer ratings seem to depend on regional tastes and preferences. 相似文献
999.
Elena Gil de Prado Eva‐María Rivas María‐Isabel de Silóniz Belén Diezma Pilar Barreiro José M. Peinado 《Yeast (Chichester, England)》2014,31(11):431-440
The colony shape of four yeast species growing on agar medium was measured for 116 days by image analysis. Initially, all the colonies are circular, with regular edges. The loss of circularity can be quantitatively estimated by the eccentricity index, Ei, calculated as the ratio between their orthogonal vertical and horizontal diameters. Ei can increase from 1 (complete circularity) to a maximum of 1.17–1.30, depending on the species. One colony inhibits its neighbour only when it has reached a threshold area. Then, Ei of the inhibited colony increases proportionally to the area of the inhibitory colony. The initial distance between colonies affects those threshold values but not the proportionality, Ei/area; this inhibition affects the shape but not the total surface of the colony. The appearance of irregularities in the edges is associated, in all the species, not with age but with nutrient exhaustion. The edge irregularity can be quantified by the Fourier index, Fi, calculated by the minimum number of Fourier coefficients that are needed to describe the colony contour with 99% fitness. An ad hoc function has been developed in Matlab v. 7.0 to automate the computation of the Fourier coefficients. In young colonies, Fi has a value between 2 (circumference) and 3 (ellipse). These values are maintained in mature colonies of Debaryomyces, but can reach values up to 14 in Saccharomyces. All the species studied showed the inhibition of growth in facing colony edges, but only three species showed edge irregularities associated with substrate exhaustion. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
1000.
Sergio Nogales‐Delgado María del Carmen Fuentes‐Pérez Concepción Ayuso‐Yuste Diego Bohoyo‐Gil 《International Journal of Food Science & Technology》2014,49(1):114-120
Nectarine [Prunus persica (L.) Batsch] is a sought‐after fruit due to its properties. In addition, minimally processed produces are more and more accepted by consumers. Four nectarine cultivars (‘Early Top’, ‘Nectaprima’, ‘Big Top’ and ‘Venus’) were selected to study their suitability for minimal processing. Samples were processed in a clean room at 8 °C, washed them in water (4 °C) and stored at 4 °C in modified atmosphere packaging. The samples were analysed at 0, 3, 6 and 9 days of storage, and quality parameters as well as functional compounds (polyphenols and polyphenol oxidase activity) were studied. Principal component analysis (PCA) was carried out to assess the relationship between nectarine cultivars and determined parameters. In conclusion, ‘Early Top’ and ‘Nectaprima’ cultivars showed the best quality results and therefore a promising suitability for fresh‐cut processing. Nevertheless, the remaining cultivars should not be ruled out due to their functional content, advising additional conservation treatments for them. 相似文献