全文获取类型
收费全文 | 1268篇 |
免费 | 25篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 39篇 |
综合类 | 1篇 |
化学工业 | 181篇 |
金属工艺 | 20篇 |
机械仪表 | 24篇 |
建筑科学 | 24篇 |
矿业工程 | 2篇 |
能源动力 | 14篇 |
轻工业 | 119篇 |
水利工程 | 8篇 |
石油天然气 | 6篇 |
武器工业 | 2篇 |
无线电 | 237篇 |
一般工业技术 | 167篇 |
冶金工业 | 284篇 |
原子能技术 | 3篇 |
自动化技术 | 163篇 |
出版年
2022年 | 10篇 |
2021年 | 9篇 |
2020年 | 9篇 |
2019年 | 8篇 |
2018年 | 8篇 |
2017年 | 12篇 |
2016年 | 15篇 |
2015年 | 18篇 |
2014年 | 25篇 |
2013年 | 37篇 |
2012年 | 37篇 |
2011年 | 33篇 |
2010年 | 16篇 |
2009年 | 29篇 |
2008年 | 44篇 |
2007年 | 54篇 |
2006年 | 36篇 |
2005年 | 45篇 |
2004年 | 31篇 |
2003年 | 46篇 |
2002年 | 44篇 |
2001年 | 43篇 |
2000年 | 34篇 |
1999年 | 42篇 |
1998年 | 126篇 |
1997年 | 72篇 |
1996年 | 45篇 |
1995年 | 42篇 |
1994年 | 37篇 |
1993年 | 40篇 |
1992年 | 27篇 |
1991年 | 16篇 |
1990年 | 14篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 13篇 |
1986年 | 10篇 |
1985年 | 17篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1980年 | 14篇 |
1979年 | 5篇 |
1977年 | 10篇 |
1976年 | 16篇 |
1975年 | 8篇 |
1974年 | 6篇 |
1973年 | 6篇 |
1972年 | 5篇 |
排序方式: 共有1294条查询结果,搜索用时 15 毫秒
51.
D S Lough L D Muller R S Kensinger T F Sweeney L C Griel 《Journal of dairy science》1988,71(5):1161-1169
Four early lactation Holstein cows (44 to 105 d postpartum) were used in a 4 X 4 Latin square experiment in a 2 X 2 factorial arrangement of treatments to study effects of added dietary fat and/or bovine somatotropin on performance and metabolism. Treatments were: 1) control diet plus placebo injection; 2) 5% added dietary fat (hydrolyzed blend of animal and vegetable fat) + placebo injection; 3) control diet + 50 IU bovine somatotropin/d; and 4) 5% added dietary fat + 50 IU bovine somatotropin/d. Dietary fat reduced dry matter intake (21.6 vs. 22.7 kg/d) and elevated plasma triglycerides (34.7 vs. 29.2 mg/100 ml). Injection of somatotropin lowered blood urea nitrogen, increased plasma free fatty acids, and increased plasma somatotropin. Milk production, milk fat percent, and 4% FCM production were increased by the injection of somatotropin. Milk protein percent was decreased (3.30 vs. 3.44%) with added fat and tended to be lower with somatotropin. The percentage of short-chain fatty acids (C6 to C14) in milk fat decreased with added fat while the percentage of stearic and oleic acids in milk fat increased. Production responses for fat plus somatotropin and somatotropin treatments were similar. Under the conditions of this study, the addition of dietary fat with injection of somatotropin had little effect on production parameters compared with that found with somatotropin alone. 相似文献
52.
Milk response to concentrate supplementation of high producing dairy cows grazing at two pasture allowances 总被引:4,自引:0,他引:4
Twenty multiparous Holstein cows (four ruminally cannulated) in five 4 x 4 Latin squares with 21-d periods were used to study the effect of concentrate supplementation when grazed at two pasture allowances. The four dietary treatments resulted from the combination of two pasture allowance targets (low, 25 vs. high, 40 kg of dry matter/cow per day) and two concentrate supplementation levels (zero vs. 1 kg of concentrate/4 kg of milk). Concentrate supplementation decreased pasture dry matter intake 2.0 kg/d at the low pasture allowance (17.5 vs. 15.5 kg/d) and 4.4 kg/d at the high pasture allowance (20.5 vs. 16.1 kg/d). Substitution rate was lower at the low pasture allowance (0.26 kg pasture/kg concentrate) than at the high pasture allowance (0.55 kg of pasture/kg of concentrate). Total dry matter intake of both supplemented treatments averaged 24.4 kg/d. Milk production of both supplemented treatments averaged 29.8 kg/d, but was increased with higher pasture allowance in the unsupplemented treatments (19.1 vs. 22.2 kg/d). Milk response to concentrate supplementation was 1.36 and 0.96 kg of milk/kg of concentrate for the low and high pasture allowances, respectively. Concentrate supplementation reduced milk fat percentage but increased milk protein percentage. Rumen pH and NH3-N concentration were decreased with concentrate supplementation. Substitution rate was likely related to both negative associative effects in the rumen (reductions in rumen pH, rate of pasture digestion, and NDF digestibility) and reductions in grazing time. The latter was more important, quantitatively explaining at least 80% of the reduction in pasture dry matter intake observed. 相似文献
53.
54.
Kamikawachi RC Collere Possetti GR Falate R Muller M Fabris JL 《Applied optics》2007,46(15):2831-2837
A detailed study of the thermal and strain sensitivities of a long-period grating when the device is immersed in different external media is presented. The range of refractive indices analyzed are within 1.000 to 1.447, corresponding to samples of air, water, ethanol, naphtha, thinner, turpentine, and kerosene. Within the same range of refractive indices, the strain sensitivity is between (-0.24 +/- 0.03) and (-0.94 +/- 0.11) pm/microepsilon. For the grating immersed in these fluids, the refractive index sensitivity ranges from -3 to -1035.6 nm per refractive index units. The coupling thermo-optic coefficients and the strain-optic coefficients are also measured, resulting in the range from (2.45 +/- 0.04)x10(-5) to (15.89 +/- 0.82)x10(-5) deg C(-1) and (-1.15 +/- 0.04) to (-1.61 +/- 0.04) microepsilon(-1), respectively. A noticeable nonlinear behavior of the thermal sensitivity is found for external media with refractive indices higher than 1.430. 相似文献
55.
Evaluation of nonthermal effects of electricity on inactivation kinetics of Staphylococcus aureus and Escherichia coli during ohmic heating of infant formula 下载免费PDF全文
56.
低雾化低挥发性汽车用新型聚氨酯泡沫塑料助剂 总被引:1,自引:1,他引:1
康普顿公司开发了一系列适用于消除或减少汽车内饰件中胺扩散或雾化的添加剂,其中包括快速、有效的生产用零扩散催化剂和低雾化表面活性剂。该系列添加剂能大大降低泡沫制品中的胺扩散,与异氰酸酯和多元醇原料能组成最佳组合,以保持良好的泡沫物理性能。 相似文献
57.
Sbastien Muller Philippe Burg Julien Starck Denise Cagniant Pierre Magri Ren Gruber Jean-Michel Trichard 《Catalysis Today》2007,119(1-4):291
Several samples of exhaust diesel soot are investigated by inverse gas chromatography and linear solvation energy relationship (LSER) modelling according to their soluble organic fraction content and their time of exposure in oxidative conditions. The results demonstrate the evolution of the adsorptive properties of the studied materials towards volatile compounds during the oxidation under NO2. 相似文献
58.
Danielle F.M. OliveiraPaulo S. Batista Paulo S. Muller Jr.Valdemir Velani Marcela D. FrançaDanilo R. de Souza Antonio E.H. Machado 《Dyes and Pigments》2012,92(1):563-572
The performance of different titanium dioxide (TiO2) catalysts and a composite based on the association between TiO2 P25 and Zinc Phthalocyanine (TiO2/ZnPc 1.6%) was evaluated in the photocatalytic degradation of the dye Ponceau 4R (C.I. 16255). The results show that the composite presents a better performance than the other, reaching about 50% mineralization of the dye in 120 min of reaction, around three times higher than that observed under the action of pure TiO2 P25, although this catalyst presents a quantum yield of hydroxyl radical generation about three times higher than that estimated for the composite. This result seems to be a consequence of the synergism between the electronically excited ZnPc aggregates and the TiO2 surface.A parallel study, based on methods from quantum mechanics also suggested the most feasible routes for the photodegradation of the dye in the absence of the catalyst. 相似文献
59.
Amédée Djemai Etienne Balan Guillaume Morin Giancarlo Hernandez Jean Claude Labbe Jean Pierre Muller 《Journal of the American Ceramic Society》2001,84(5):1017-1024
Kaolinites with various degrees of structural order and iron content were heated and subsequently analyzed via electron paramagnetic resonance. Iron was present in two different states in the heated materials, either as dilute structural Fe3+ ions or in concentrated Fe3+ phases. During metakaolinization, the environment of dilute Fe3+ ions changed, following modifications of the Al3+ coordination, and the Fe3+ concentration increased. With the breakdown of metakaolinite, the diffusion of Fe3+ ions induced their exsolution in superparamagnetic iron-rich domains (Fe3+ clusters in γ-Al2 O3 and/or Fe3+ oxide nanophases), which produced a decrease in the dilute Fe3+ concentration. The subsequent breakdown of γ-Al2 O3 and the formation of mullite made the dilute Fe3+ concentration increase again, because of the incorporation of Fe3+ ions in the mullite structure. 相似文献
60.
A computer-implemented model for predicting ECM work piece geometry has been developed and experimentally verified with a commercial ECM machine for cavity sinking in copper and 302-stainless steel with 2N K NO3 electrolyte. Constant tool piece feed rates of 7–10 × 10?4 cm/s, and applied voltages of 11–25 V were used. The model predicts the dependence of work piece geometry on operating conditions and on the electrochemical and physical properties of the metal—electrolyte pair. Comparison of eight equilibrium and six unsteady state experimental cavity profiles in copper showed satisfactory agreement with predictions, as did five equilibrium profiles for cavity sinking in 302-stainless steel. 相似文献