全文获取类型
收费全文 | 2807篇 |
免费 | 71篇 |
国内免费 | 57篇 |
专业分类
电工技术 | 21篇 |
综合类 | 79篇 |
化学工业 | 931篇 |
金属工艺 | 114篇 |
机械仪表 | 35篇 |
建筑科学 | 39篇 |
矿业工程 | 166篇 |
能源动力 | 461篇 |
轻工业 | 486篇 |
水利工程 | 8篇 |
石油天然气 | 107篇 |
武器工业 | 3篇 |
无线电 | 12篇 |
一般工业技术 | 242篇 |
冶金工业 | 118篇 |
原子能技术 | 94篇 |
自动化技术 | 19篇 |
出版年
2024年 | 4篇 |
2023年 | 31篇 |
2022年 | 65篇 |
2021年 | 85篇 |
2020年 | 92篇 |
2019年 | 76篇 |
2018年 | 72篇 |
2017年 | 81篇 |
2016年 | 92篇 |
2015年 | 55篇 |
2014年 | 119篇 |
2013年 | 191篇 |
2012年 | 145篇 |
2011年 | 248篇 |
2010年 | 167篇 |
2009年 | 167篇 |
2008年 | 141篇 |
2007年 | 144篇 |
2006年 | 113篇 |
2005年 | 85篇 |
2004年 | 86篇 |
2003年 | 78篇 |
2002年 | 74篇 |
2001年 | 64篇 |
2000年 | 79篇 |
1999年 | 61篇 |
1998年 | 62篇 |
1997年 | 41篇 |
1996年 | 42篇 |
1995年 | 37篇 |
1994年 | 31篇 |
1993年 | 29篇 |
1992年 | 18篇 |
1991年 | 16篇 |
1990年 | 8篇 |
1989年 | 10篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有2935条查询结果,搜索用时 0 毫秒
1.
Preference for saltiness is learned by oral exposure to salt taste; however, some data suggest a role for bodily sodium and potassium levels on salt taste preferences as well. The objective was to investigate whether encapsulated sodium and potassium supplementation lead to altered salt taste responses among adults with high blood pressure on a low sodium and low potassium diet. Twenty-six participants with untreated upper-range prehypertension or stage 1 hypertension were on a fully controlled low sodium and low potassium diet (both targeted at 2 g/day) for 13 weeks. Participants received capsules with sodium (3 g/d), potassium (3 g/d), or placebo, for 4 weeks each, in randomized order in a double blind crossover design. Sensory evaluation was done before and after each supplementation period and involved ratings of pleasantness and intensity in different salt (NaCl) concentrations in food and water, desire-to-eat salty food, and detection threshold for NaCl. Neither sodium supplementation nor potassium supplementation led to alterations in salt taste responses in food and water, and did not affect detection threshold (P = 0.59). There was no clear role for sodium or potassium supplementation on desire-to-eat salty food. In addition, we did not find effects of reduced oral exposure to salt over weeks, through the sodium-reduced diet, on salt taste preferences, in contrast to earlier studies. In conclusion, the results of this study suggest preference for saltiness is independent of changes in bodily sodium or potassium levels. 相似文献
2.
3.
In this work, we examine the effect of small additions of cationic quaternary ammonium salts (QAS) of different molecular weight on the rheology of an industrial ceramic suspension deflocculated with sodium polyacrylate and sodium metasilicate. The observed shear thinning behaviors obey the typical power law of fluid rheology. In order to characterize the rheological behavior of these slurries, three new parameters are introduced: a low shear rate consistency index and two transient viscosities, distant from the equilibrium, after increasing and decreasing the shear rates. These parameters vary with polyacrylate molecular weight and on additions of small quantities of QAS, which we found to be useful for decreasing the slurry viscosity. 相似文献
4.
Vjacheslav V. Zuev 《Journal of Polymer Research》2008,15(5):351-356
Functionalized polyanilines containing biphenyl, terphenyl, carbazole, anthracene, and 4-n-hexylphenyl moieties were synthesized though the reaction of polyaniline in emeraldine base form with sodium salt of corresponding
vinylketoaromatics with quantitative yields. Polymers were characterized with Fourier transform infrared spectroscopy, proton
nuclear magnetic resonance spectroscopy, and thermogravimetry. The emission characteristics of these polymers in N-methyl-2-pyrrolidone solution were examined. The functionalized polyanilines exhibited an intense green emission. 相似文献
5.
Valentina I. Simagina Pavel A. Storozhenko Olga V. Netskina Oksana V. Komova Galina V. Odegova Yury V. Larichev Arcady V. Ishchenko Anna M. Ozerova 《Catalysis Today》2008,138(3-4):253
Catalytic hydrolysis of NaBH4 and NH3BH3 has been studied. It was shown that the nature of the support and the active component of the catalyst affect the H2 generation rate. Despite similar sizes of rhodium particles formed on the surface of different supports (γ-Al2O3, TiO2, carbon), their reactivity is different. Rh/TiO2 with low rhodium concentration (1 wt.%) is the most active catalyst both in the hydrolysis of NaBH4 and NH3BH3. The obtained results show that the rhodium chloride interaction with titania determines the reactivity of rhodium particles formed under action of NaBH4 medium. TEM, DRS UV–vis and XPS were used to characterize the catalysts. 相似文献
6.
7.
Nourh ne Boudhrioua Bertrand Broyart Catherine Bonazzi Jean-Dominique Daudin 《Drying Technology》2005,23(12):2313-2335
A method is presented for computing the values of apparent diffusivity in solids with respect to the concentration of the diffusing substance (water or sodium chloride). This method does not require any assumption upon the mathematical relationship between diffusivity and concentration. It can be applied to experimental measurements of local concentration versus position within the solid (profiles) with relatively few measurements (circa 10) and a mathematical smoothing of the experimental data by using an artificial neural network model. The method was first validated on simulated data obtained by using a constant diffusivity value and on experimental profiles when the relation between diffusivity and concentration was given. It was then applied to original experimental moisture profiles obtained by putting gelatin gels with different initial moisture contents into contact for up to 14 days. The method was also successfully applied to five sets of experimental moisture and sodium chloride profiles taken from the literature and obtained from different food products. Apparent diffusivities calculated by our method were found in agreement with those obtained by authors using different numerical methods to compute the diffusivity values. 相似文献
8.
用流动微量量热法研究了十二烷基硫酸钠(SDDS)和十二碳羧酸钠(SL)在克拉玛依油田九区和乌尔禾区油砂上的吸附,简要地计论了吸附机理。所得实验结果表明,SL 在油砂上的吸附强度比 SDDS 的要大,在相当低的浓度下即可迟到饱和吸附。 相似文献
9.
Iron(III) oxide tablets were electrolytically reduced to iron in molten sodium hydroxide at 530 °C and recovered to produce
iron with 2 wt.% oxygen suitable for re-melting. The cell was operated at 1.7 V and an inert nickel anode was used. The thermodynamics
and mechanism of the process was also investigated. By controlling the activity of sodium oxide in the melt, the cell could
be operated below the decomposition voltage of the electrolyte with the net sequence of events being the ionization of oxygen,
its subsequent transport to the anode and discharge leaving behind iron at the cathode. A reduction time of 1 h was achieved
for a 1 g oxide tablet (close to the theoretical reduction time predicted by Faraday’s laws) at a current density of 520 mA cm−2 with iron phase yields of ∼90 wt.%. The energy consumption was 2.8 kWh kg−1. 相似文献
10.
Maw-Ling Wang Venugopal Rajendran 《Journal of the Chinese Institute of Chemical Engineers》2008,39(5):533-537
Propenylbenzenes and cinnamic acid derivatives yield correspondingly substituted benzaldehydes when oxidized by lead-ruthenium pyrochlore oxide in the presence of sodium hydrochlorite as a co-oxidant at pH 11 under heterogeneous conditions. The reaction of terminal and internal aliphatic alkenes under similar conditions affords no aldehydes. 相似文献