全文获取类型
收费全文 | 154951篇 |
免费 | 10264篇 |
国内免费 | 4850篇 |
专业分类
电工技术 | 6804篇 |
技术理论 | 5篇 |
综合类 | 10811篇 |
化学工业 | 27644篇 |
金属工艺 | 9283篇 |
机械仪表 | 6013篇 |
建筑科学 | 18060篇 |
矿业工程 | 3962篇 |
能源动力 | 4022篇 |
轻工业 | 27963篇 |
水利工程 | 5196篇 |
石油天然气 | 22829篇 |
武器工业 | 431篇 |
无线电 | 4270篇 |
一般工业技术 | 7580篇 |
冶金工业 | 8780篇 |
原子能技术 | 486篇 |
自动化技术 | 5926篇 |
出版年
2024年 | 740篇 |
2023年 | 1876篇 |
2022年 | 3653篇 |
2021年 | 4566篇 |
2020年 | 4655篇 |
2019年 | 3993篇 |
2018年 | 3594篇 |
2017年 | 4502篇 |
2016年 | 4767篇 |
2015年 | 4930篇 |
2014年 | 9403篇 |
2013年 | 8773篇 |
2012年 | 10582篇 |
2011年 | 11181篇 |
2010年 | 8738篇 |
2009年 | 8927篇 |
2008年 | 7585篇 |
2007年 | 9648篇 |
2006年 | 9489篇 |
2005年 | 7999篇 |
2004年 | 6972篇 |
2003年 | 6414篇 |
2002年 | 5513篇 |
2001年 | 4313篇 |
2000年 | 3619篇 |
1999年 | 2891篇 |
1998年 | 2173篇 |
1997年 | 1775篇 |
1996年 | 1428篇 |
1995年 | 1199篇 |
1994年 | 889篇 |
1993年 | 631篇 |
1992年 | 579篇 |
1991年 | 442篇 |
1990年 | 288篇 |
1989年 | 283篇 |
1988年 | 174篇 |
1987年 | 164篇 |
1986年 | 96篇 |
1985年 | 136篇 |
1984年 | 123篇 |
1983年 | 89篇 |
1982年 | 61篇 |
1981年 | 21篇 |
1980年 | 39篇 |
1979年 | 11篇 |
1977年 | 10篇 |
1966年 | 12篇 |
1964年 | 12篇 |
1959年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
101.
Bleached and unbleached forms of a rosemary oleoresin (RO) in stripped and nonstripped soybean oil behave both as antioxidant
and prooxidant in a light-induced oxidative system. At 0.02 and 0.05% levels, RO had the greatest antioxidant activity, while
at 0.01 and 0.5% levels it had the highest prooxidant activity in both stripped and nonstripped soybean oil. Treatment of
both soybean oil systems with tertiary butylhydroquinone controlled light-induced oxidation of the oil better than did the
oleoresin treatments. The prooxidant activity of the 0.5% RO level was probably due to an excess of prooxidant components
being carried into the oil at that level, whereas the reduced antioxidant activity at 0.01% was probably due to the low initial
level of active antioxidant components being added to the oil.
Published as Journal Series No. 10072, Nebraska Agricultural Research Division, Department of Food Science and Technology,
University of Nebraska, Lincoln, NE 68583-0919. 相似文献
102.
A brown coal, peat and oil shale were subjected to a rapid pyrolysis process and medium-heat-value gases together with tar were collected. The char residue was of high activity and suitable for gasification to create a two-stage gasification system. The coal-tar is used for manufacturing liquid fuels and chemicals. 相似文献
103.
A monitoring program was performed to investigate heavy metal content alteration due to exploratory drilling for oil using non-aqueous fluids (NAFs) in Brazilian offshore, 900 m deep. Fourteen elements were monitored in 54 sites and it was verified that after drilling activities the average Ba concentration was remarkably increased with respect to background level, even 1 year after the activity. A minor increase in Mn and a moderate increase in Al concentrations were verified. The Cd, Cr, Ni, As, Co, Cu, Pb, V, and Zn concentrations were at the background levels, ca. 1 year after the NAFs drilling materials deposition on the seafloor. The Al, Ba, Cd, Cr, Cu, Ni and Zn mean concentrations were significantly different (P<0.05) between the three sampling operations (cruises) performed, while As, Cd, Fe and Pb presented different mean values according to the distance of the oil well, independent of the sampling operation. Interaction between sampling operation and distance was observed for Mn. In all sediment samples the Hg concentration was below the detection limit (0.07 μg g−1). 相似文献
104.
介绍了国外利用天然气生产油口的生产工艺,探讨了山西省利用丰富的煤层气资源发展合成油的可能性和优势,并提出了相应的发展建议。 相似文献
105.
J. F. Toro-Vazquez Alejandro Rocha-Uribe 《Journal of the American Oil Chemists' Society》1993,70(6):589-594
The adsorption of peroxides, unsaturated carbonyls, free fatty acids and carotenoids from unrefined sesame oil on vegetable
carbon (5%, w/w) in a miscella system was studied. Three different solvent conditions (hexane/ethanol, 100:0, 95:5 and 75:25,
vol/vol), combined in a factorial design with five levels of solvent (0, 10, 20, 30 and 40%, w/w), were used to develop the
miscella. Equilibrium adsorption was not achieved during the 100 min of adsorption, mainly because the oil components were
involved in oxidation reactions during the adsorption process. However, for a given solvent concentration, adsorption of the
oil components showed a significant linear regression on their respective initial concentration in the miscella (Ci). Peroxides and carbonyls showed, at all solvent levels investigated, an affinity for the carbon more independent of their
Ci than free fatty acids and carotenoids. In general, at the same Ci, a higher adsorption was achieved as solvent concentration increased. The results indicated that free fatty acid adsorption
may depend on competitive adsorption based on molecule hydrophobicity. However, in spite of the higher hydrophobicity of carotenoids,
compared with free fatty acids, they might not be competing for the same adsorbing sites. Ethanol showed a prooxidant effect
that increased peroxide production during adsorption but did not affect the reaction involved in carbonyl production. 相似文献
106.
When BaTiO3 ceramics were sintered at relatively low temperatures (≤1250°C), the grains with reentrant edges caused by a (111) double twin grew exclusively. As a result, a microstructure with a bimodal grain-size distribution composed of platelike large grains and fine matrix grains was obtained. In contrast, at the usual sintering temperature between 1250° and 1350°C, grains containing a (111) double twin did not exhibit any growth advantage. In this case, a coarse and uniform microstructure was obtained. When this coarse-grained specimen was further heat-treated at 1365°C, the grains possessing a double twin were observed to grow exclusively again. The results were explained in terms of a coarsening process controlled by two-dimensional nucleation. 相似文献
107.
R. M. Tubaileh M. M. Graciani Constante M. Léon Camacho A. López López E. Graciani Constante 《Journal of the American Oil Chemists' Society》2002,79(10):971-976
Changes in the content of aliphatic waxes during industrial deodorization and/or physical refining of bleached olive oil were
studied in an experimental discontinuous pilot plant of 250 kg deodorizer using nitrogen as stripping gas in place of steam.
The kinetic constants for the decomposition of waxes during the deodorization process were determined. The reaction orders
studied are zero (or can be considered zero) within the working interval. The values of rate constants, activation energy,
frequency factor, increment of activation Gibbs free energy, activation enthalpy, and activation entropy are established. 相似文献
108.
109.
介绍了快速高效隔膜压滤机的主要性能参数和特点 ;分析了压滤机在煤泥水处理系统中的应用情况和运行结果 ;应用快速高效隔膜压滤机对煤泥水处理系统进行改造后获得了较好的经济及社会效益 相似文献
110.