全文获取类型
收费全文 | 17973篇 |
免费 | 2855篇 |
国内免费 | 1071篇 |
专业分类
电工技术 | 121篇 |
综合类 | 1416篇 |
化学工业 | 10108篇 |
金属工艺 | 845篇 |
机械仪表 | 213篇 |
建筑科学 | 640篇 |
矿业工程 | 980篇 |
能源动力 | 872篇 |
轻工业 | 1435篇 |
水利工程 | 195篇 |
石油天然气 | 1361篇 |
武器工业 | 44篇 |
无线电 | 214篇 |
一般工业技术 | 1915篇 |
冶金工业 | 960篇 |
原子能技术 | 379篇 |
自动化技术 | 201篇 |
出版年
2024年 | 97篇 |
2023年 | 301篇 |
2022年 | 604篇 |
2021年 | 768篇 |
2020年 | 825篇 |
2019年 | 721篇 |
2018年 | 737篇 |
2017年 | 794篇 |
2016年 | 880篇 |
2015年 | 827篇 |
2014年 | 1065篇 |
2013年 | 1351篇 |
2012年 | 1681篇 |
2011年 | 1259篇 |
2010年 | 948篇 |
2009年 | 1020篇 |
2008年 | 768篇 |
2007年 | 1025篇 |
2006年 | 1017篇 |
2005年 | 714篇 |
2004年 | 651篇 |
2003年 | 566篇 |
2002年 | 472篇 |
2001年 | 393篇 |
2000年 | 378篇 |
1999年 | 277篇 |
1998年 | 248篇 |
1997年 | 234篇 |
1996年 | 199篇 |
1995年 | 148篇 |
1994年 | 177篇 |
1993年 | 133篇 |
1992年 | 117篇 |
1991年 | 93篇 |
1990年 | 64篇 |
1989年 | 60篇 |
1988年 | 52篇 |
1987年 | 50篇 |
1986年 | 28篇 |
1985年 | 34篇 |
1984年 | 30篇 |
1983年 | 21篇 |
1982年 | 15篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 4篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1959年 | 4篇 |
1951年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
采用吸附材料进行油水分离是经济且非常有效的方法。吸附材料主要有无机材料、合成高分子材料和天然有机纤维材料等。相比较而言,天然有机纤维材料为可再生生物质资源,来源广泛、生物降解性好,可有效防止二次污染,具有良好的发展潜力,备受关注。本文首先简要介绍了油水乳液稳定性的影响因素,然后综述了油水分离材料的分离原理、构建方法和分离性能等研究进展,并总结了油水乳液分离材料的表征及其分离性能的评价指标。特别地,重点总结了天然有机纤维基吸附材料分离油水乳液的研究进展。最后指出研究智能响应型天然有机纤维基油水乳液分离吸附材料是重要的发展方向。 相似文献
162.
163.
M.H. El-Naas F. Abu Al-Rub I. Ashour M. Al Marzouqi 《Chemical Engineering and Processing: Process Intensification》2007,46(12):1391-1399
Batch experiments were carried out to asses the effect of Cu(II) and Zn(II) on the biosorption of lead(II) ions by non-living Chlorella vulgaris. The uptake of Pb(II) was examined for single, binary and ternary solutions at different initial concentrations and different pH values. The experimental results showed that the uptake increased with increasing pH from 3.0 to an optimum value of 5.0. The biosorption of Pb(II) was found to be adversely affected by the presence of Cu(II) ions, while Zn(II) ions seemed to have negligible effect on the process. The equilibrium data were fitted to four isotherm models: Langmuir, Freundlich, Sips and Dubinin–Radushkevich; the Sips isotherm gave the best fit for the data. Modeling of the controlling mechanisms indicated that both intrinsic kinetics and mass transfer played major roles in controlling the process. A new dimensionless parameter, Ψ, was defined to asses the relative contributions of the two mechanisms to the biosorption of lead(II). Mass transfer seemed to be the dominant mechanism at low initial lead(II) concentrations, while intrinsic kinetics dominates at high concentrations. 相似文献
164.
Nabel?A.?NegmEmail author Salwa?M.?I.?Morsy 《Journal of surfactants and detergents》2005,8(3):283-287
A weight loss technique was used to determine the corrosion inhibition efficiency of synthesized alkyl mono-and dibenzoate
triethanolammonium bromide derivatives (TEAMB, TEADB) in an acidic medium (2 N HCl) at different doses (50, 100, and 200 ppm).
The results showed that monoderivatives had a higher corrosion inhibition efficiency than diderivatives. The results were
correlated with several factors, including the alkyl chain length of the hydrophobic chains, interfacial tension (IT), critical
micelle concentration (CMC), and adsorption free energy of these inhibitors. Increasing the geometric length of the alkyl
chains in the synthesized inhibitors had an increasing effect on their corrosion inhibition efficiency, whereas decreasing
the CMC and IT had an increasing effect on their tendency toward corrosion inhibition. The number of hydrophobic chains attached
to the inhibitor molecules had a vital influence on their efficiency as corrosion inhibitors. 相似文献
165.
166.
The surface and mechanical properties of copolymers of hydroxyalkyl acrylates and methacrylates have been examined by a variety of techniques. This work is complementary to earlier parts of this series which describe the effect of copolymer structure on water binding properties. Water structure has been demonstrated to exert a profound effect upon mechanical properties whether measured in compression or in tension. In particular, water that is characterized by differential scanning calorimetry as ‘freezing’ water is observed to have a marked plasticizing effect upon the gel, whereas ‘non-freezing’ water has little such effect. Similarly, the ‘freezing’ water produces a more marked effect on thermally induced transitions. Two distinct transition points are observed as a result of its presence. One corresponds to the freezing point of water and the other to a glass transition temperature, whose value depends upon the proportion of ‘freezing’ or ‘plasticizing’ water in the gel. Several predictive and direct measurement techniques have been used to study the surface properties of the copolymers in both hydrated and dehydrated states. Taken together they have established a sound understanding of the way in which polar and dispersive components of surface free energy vary as a function of copolymer composition and water content. Use of protein adsorption and fibroblast cell interaction techniques demonstrate that biological phenomena respond to changes at a molecular level which current macroscopic surface energy techniques are unable to discern. 相似文献
167.
A. Zecchina F. Geobaldo C. Lamberti S. Bordiga G. Turnes Palomino C. Otero Areán 《Catalysis Letters》1996,42(1-2):25-33
Fourier transform IR spectroscopy of CO and N2, adsorbed at liquid nitrogen temperature, was used to characterize an MFI-type H-FeZSM-5 ferrisilicate which was synthesized with a Si/Fe ratio of 50. Thermal treatment of this material at 773 and 973 K was performed in order to follow formation of extraframework species. On samples fired at 773 K Brønsted acid sites were present which gave an O-H stretching band at 3630 cm–1. These hydroxyl groups formed adducts with both probe molecules, which were monitored by the corresponding bathochromic shift, . Corresponding values for adsorbed CO and N2 were = –270 and = – 100, respectively. Increasing the firing temperature up to 973 K led to complete removal of iron from the zeolite framework, and consequent disappearance of Brønsted acidity. In this process, extraframework iron oxide species were formed which were also characterized by IR spectroscopy of the adsorbed probe molecules. Both CO and N2 gave Lewis-type adducts with coordinatively unsaturated Fe3+ ions present in the extraframework material. A comparison is made with results of a previous study on the H-GaZSM-5 isomorph. 相似文献
168.
169.
170.
The synthesis of super-microporous aluminosilicate with a pore diameter of 14.6 Å has been achieved, by means of synthesis under specified conditions with a skeletal material comprising TMOS and a small quantity of sodium aluminate, and a conventional alkyl-trimethylammonium halide (C10TMABr) as a template. This super-microporous aluminosilicate has an adsorption capacity of 0.2 ml/g at a relative water vapor pressure of 0.2, and thus is promising as an adsorbent for an adsorption heat-pump. 相似文献