全文获取类型
收费全文 | 11042篇 |
免费 | 1775篇 |
国内免费 | 138篇 |
专业分类
电工技术 | 31篇 |
综合类 | 479篇 |
化学工业 | 5338篇 |
金属工艺 | 64篇 |
机械仪表 | 84篇 |
建筑科学 | 115篇 |
矿业工程 | 24篇 |
能源动力 | 147篇 |
轻工业 | 5103篇 |
水利工程 | 20篇 |
石油天然气 | 128篇 |
武器工业 | 22篇 |
无线电 | 199篇 |
一般工业技术 | 1096篇 |
冶金工业 | 33篇 |
原子能技术 | 27篇 |
自动化技术 | 45篇 |
出版年
2024年 | 100篇 |
2023年 | 264篇 |
2022年 | 286篇 |
2021年 | 596篇 |
2020年 | 530篇 |
2019年 | 473篇 |
2018年 | 479篇 |
2017年 | 484篇 |
2016年 | 463篇 |
2015年 | 538篇 |
2014年 | 603篇 |
2013年 | 705篇 |
2012年 | 769篇 |
2011年 | 746篇 |
2010年 | 543篇 |
2009年 | 514篇 |
2008年 | 468篇 |
2007年 | 660篇 |
2006年 | 649篇 |
2005年 | 539篇 |
2004年 | 451篇 |
2003年 | 371篇 |
2002年 | 318篇 |
2001年 | 241篇 |
2000年 | 211篇 |
1999年 | 174篇 |
1998年 | 157篇 |
1997年 | 109篇 |
1996年 | 86篇 |
1995年 | 59篇 |
1994年 | 73篇 |
1993年 | 73篇 |
1992年 | 71篇 |
1991年 | 36篇 |
1990年 | 34篇 |
1989年 | 9篇 |
1988年 | 8篇 |
1987年 | 13篇 |
1986年 | 3篇 |
1985年 | 12篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 14篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Cellulose can be totally liquefied by heating to 350 °C in the presence of an aqueous phenolic solvent containing a catalyst. The main products are light aromatic hydrocarbons, benzofurans, heavier aromatic hydrocarbons such as substituted indanes and tetralin, and xanthenes. The variation of product distribution with catalyst was examined and it was found that in aqueous phenol, xanthene formation was enhanced by acidity. By substituting guaiacol for phenol, it was determined that most benzofuran formation involved the phenol solvent molecules, although a small proportion did not. This benzofuran may have arises from phenol generated from cellulose, the incorporation of phenol in the products being enhanced through a cage effect. 相似文献
32.
33.
环氧大豆油增塑剂的合成 总被引:14,自引:0,他引:14
本合成采用无溶剂一步法环氧化工艺,取消了苯作溶剂,用新型催化剂代替硫酸,在稳定剂上用30%双氧水合成的环氧大豆油,环氧值达95%以上。 相似文献
34.
P. Meenakshi S. E. Noorjahan R. Rajini U. Venkateswarlu C. Rose T. P. Sastry 《Bulletin of Materials Science》2002,25(1):25-29
DriedMusa paradiciaca (banana) stem and veins of the leaves, which were hitherto discarded as a waste, were collected and used as starting material
for the preparation of cellulose and cellulose acetate. This cellulose acetate was mixed with polystyrene to form blend of
cellulose acetate-polystyrene in order to provide enhanced stability and extended utility to the end products. The films of
these composites or their individual partners were made separately and studied for their mechanical properties, chemical modification
and morphological changes. We report here that banana stem is good source of cellulose and that cellulose completely undergoes
modification upon esterification. 相似文献
35.
纤维素经高能射线辐照,能产生一系列的化学和物理性质的变化。本文报道在不同剂量的~(60)Coγ射线辐照下,稻草中的水溶性糖、易水解糖、难水解糖,以及氨基酸、蛋白质等物质的化学变化;用辐射与加泡涨剂相结合的方法处理稻草,可以降低剂量、提高效应。 相似文献
36.
大豆蛋白纤维的性能及产品开发 总被引:11,自引:4,他引:7
主要描述了大豆蛋白纤维的性能,介绍了大豆蛋白纤维的生产以及大豆蛋白纺织新产品的开发。 相似文献
37.
38.
39.
B. E. Elizalde M. Dalla Rosa C. R. Lerici 《Journal of the American Oil Chemists' Society》1991,68(10):758-762
Maillard reaction volatile compounds (MRV), prepared by heating a glucose-glycine solution, were tested as antioxidants in
soybean oil (SBO) thermoxidation. The volatiles were transferred into the oil by stripping with a stream of Nitrogen and substituting
the atmosphere above the oil with air containing MRV. Standard accelerated oxidation was performed by heating the SBO. Peroxide
value measurement and headspace gas Chromatographic analysis were carried out on all the samples. The MRV antioxidant activity
was evaluated by determining the effect of the induction period and the kinetic rate constant of peroxide and oxidation volatiles
formation. The MRV showed a significant antioxidant activity. The effectiveness was variable depending on MRV transfer method
to the oil, and the Maillard reaction extent was related to the browning level of glucose/glycine solution. It was found that
the maximum effect of MRV prolonged about three times the induction period and reduced the kinetic rate constant by half in
relation to the control sample. MRV affects oxidative stability of soybean oil by lengthening the induction period as well
as by decreasing the rate of oxidation at the propagation state and reducing the formation of hexanal. 相似文献
40.
Carboxymethyl-2-diethylaminoethylcellulose (CM-DEAE cellulose) was prepared by etherification of carboxymethylcellulose with diethylaminoethyl chloride in a NaOH solution. The behaviour of CM-DEAE cellulose in aqueous solution was studied by viscosity and GPC measurements. The degree of substitution (DS) and existing states of DEAE substituents were examined by the use of proton NMR, and those of the CM substituents were observed with FT-IR. The results reveal that the reduced viscosity and apparent molecular size of CM-DEAE cellulose vary with the concentration of sodium chloride and changes in pH and DS. These phenomena can be explained in terms of inter- and intra-molecular ionic interactions. 相似文献