全文获取类型
收费全文 | 7576篇 |
免费 | 359篇 |
国内免费 | 77篇 |
专业分类
电工技术 | 27篇 |
综合类 | 278篇 |
化学工业 | 5670篇 |
金属工艺 | 53篇 |
机械仪表 | 28篇 |
建筑科学 | 69篇 |
矿业工程 | 17篇 |
能源动力 | 87篇 |
轻工业 | 580篇 |
水利工程 | 3篇 |
石油天然气 | 375篇 |
武器工业 | 6篇 |
无线电 | 57篇 |
一般工业技术 | 643篇 |
冶金工业 | 57篇 |
原子能技术 | 25篇 |
自动化技术 | 37篇 |
出版年
2024年 | 24篇 |
2023年 | 45篇 |
2022年 | 82篇 |
2021年 | 121篇 |
2020年 | 152篇 |
2019年 | 113篇 |
2018年 | 135篇 |
2017年 | 156篇 |
2016年 | 195篇 |
2015年 | 182篇 |
2014年 | 304篇 |
2013年 | 438篇 |
2012年 | 492篇 |
2011年 | 485篇 |
2010年 | 379篇 |
2009年 | 378篇 |
2008年 | 308篇 |
2007年 | 457篇 |
2006年 | 464篇 |
2005年 | 399篇 |
2004年 | 389篇 |
2003年 | 319篇 |
2002年 | 309篇 |
2001年 | 270篇 |
2000年 | 214篇 |
1999年 | 192篇 |
1998年 | 151篇 |
1997年 | 126篇 |
1996年 | 100篇 |
1995年 | 63篇 |
1994年 | 84篇 |
1993年 | 69篇 |
1992年 | 47篇 |
1991年 | 43篇 |
1990年 | 36篇 |
1989年 | 41篇 |
1988年 | 22篇 |
1987年 | 25篇 |
1986年 | 18篇 |
1985年 | 38篇 |
1984年 | 38篇 |
1983年 | 18篇 |
1982年 | 35篇 |
1981年 | 12篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1978年 | 6篇 |
1977年 | 9篇 |
1976年 | 2篇 |
1975年 | 3篇 |
排序方式: 共有8012条查询结果,搜索用时 15 毫秒
1.
P(DBF-VA)型柴油低温流动性改进剂的研制 总被引:1,自引:1,他引:0
针对新疆地产柴油蜡含量较高的特点,以游离基聚合法合成了富马酸双链混合酯和醋酸乙烯酯共聚物型[P(DBF-VA)]柴油低温流动改进剂,利用正交实验研究了单体配比,引发剂用量,溶剂用量,聚合温度对聚合物降冷滤效果的影响。共聚物用IR进行表征,利用XRD初步探讨了该降凝剂的降凝机理。结果表明:该剂能使吐哈—10~#、0~#柴油冷滤点降低10℃和7℃;使独山子0~#柴油冷滤点下降12℃;使石化0~#柴油冷滤点下降8℃;使克拉玛依0~#柴油的冷滤点下降8℃。 相似文献
2.
G Garrote J
M Cruz H Domínguez J
C Paraj 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2003,78(4):392-398
Non‐isothermal processing of lignocellulosic materials in aqueous media (autohydrolysis reaction) under mild conditions leads to solutions containing valuable chemicals (oligosaccharides, sugars and acetic acid) and other, undesired, compounds (belonging to the extractive and acid‐soluble lignin fractions) which have to be removed in further purification treatments. Liquors obtained by non‐isothermal autohydrolysis of Eucalyptus globulus wood and corncobs under a variety of operational conditions were extracted with ethyl acetate in order to remove non‐saccharide components, and the suitability of the fraction dissolved in the organic phase was assayed for possible utilisation as an antioxidant. The yield and antioxidant activity of ethyl acetate extracts (measured by the α,α‐diphenyl‐β‐picrylhydrazyl (DPPH) radical scavenging capacity) showed a strong dependence on the autohydrolysis conditions. The antioxidant activity of extracts obtained under selected operational conditions compared well with synthetic antioxidants. © 2003 Society of Chemical Industry 相似文献
3.
Poly(vinyl alcohol) is crosslinked in dilute solution (c=0.1 wt%) with glutaraldehyde. The reaction product is characterized by viscometry and gel permeation chromatography (g.p.c.). The intrinsic viscosity decreases with increasing degree of crosslinking and does not depend on temperature. G.p.c. reveals that the reaction product is not homogeneous, but consists of a mixture of particles with different sizes, possibly both intra- and intermolecularly crosslinked molecules. The intramolecularly crosslinked molecules are smaller in size than the initial polymer molecules and their size depends on the degree of crosslinking. They possess a narrow particle size distribution even if the initial polymer sample had a broad molecular weight distribution. 相似文献
4.
医用聚氯乙烯材料的表面光接枝改性 总被引:6,自引:0,他引:6
研究了在不排氧氛围下 ,紫外光照射 ,以二苯甲酮 (BP)为光引发剂 ,甲基丙烯酸缩水甘油酯(GMA)在医用聚氯乙烯 (PVC)薄膜表面的气相接枝聚合。探讨了反应条件对接枝结果的影响 ,并用正交法指出了影响因素的显著性。用傅立叶红外 (FT- IR)、水接触角作为接枝改性结果的表征。FT- IR谱图表明 GMA已接枝到 PVC膜表面。水接触角由接枝前的 78°下降到 5 4° 相似文献
5.
6.
Temperature and pH‐responsive interpenetrating polymer network (IPN) hydrogels, constructed with poly(methacrylic acid) (PMAA) and poly(vinyl alcohol) (PVA), by a sequential IPN method, were studied. The characterization of IPN hydrogels was investigated by Fourier‐transform infrared spectroscopy, differential scanning calorimetry (DSC) and swelling under various conditions. The IPN hydrogels exhibited relatively high swelling ratios, in the range 230–380 %, at 25 °C. The swelling ratios of the PMAA/PVA IPN hydrogels were pH and temperature dependent. DSC was used for the quantitative determination of the amounts of freezing and non‐freezing water. The amount of free water increased with increasing PMAA content in the IPN hydrogels. Copyright © 2004 Society of Chemical Industry 相似文献
7.
Michalis Koutinas Ludmila G Peeva Andrew G Livingston 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(11):1252-1260
This study presents a comparison of the efficiency of a bioscrubber and a biotrickling filter (BTF) for the removal of ethyl acetate (EA) vapour from a waste gas stream, under the same operating conditions. The maximum EA elimination capacity achieved in the bioscrubber was 550 g m?3 h?1 with removal efficiency higher than 96%. For higher EA loadings the bioscrubber was oxygen limited, which caused incomplete EA biodegradation. When pure oxygen was fed to the bioscrubber at a rate of 0.02 L min?1, the bioscrubber recovered and could treat higher EA loadings without any oxygen limitation. The BTF achieved EA elimination capacity of 600 g m?3 h?1 with removal efficiency higher than 97% and the dissolved oxygen concentration remained substantially higher than in the bioscrubber. However, severe channelling and blockage of the spray nozzle occurred due to the excessive biomass growth. Overall, the bioscrubber system was easier to operate and control than the BTF, while an enhancement of the oxygen mass transfer in the bioscrubber could potentially increase its performance by up to three times. Copyright © 2005 Society of Chemical Industry 相似文献
8.
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
9.
10.
磷铝杂原子固体酸催化剂催化合成乙酸异丙酯 总被引:5,自引:0,他引:5
高文艺 《精细石油化工进展》2003,4(12):30-31
以丙烯和乙酸为原料 ,自制的磷铝杂原子固体酸作催化剂催化合成了乙酸异丙酯 ,考察了反应温度、反应压力、反应空速 (LHSV)及催化剂用量对酯化反应的影响 ,同时考察了固体酸催化剂的重复使用性。确定了最佳合成条件 :反应压力 1 5MPa,反应温度 1 60℃ ,反应空速2 0h-1,催化剂用量 2 0g。在此条件下 ,酯化率可达 91 5 % ,乙酸异丙酯选择性达 99 0 % ,且催化剂的重复使用性良好。 相似文献