全文获取类型
收费全文 | 658篇 |
免费 | 12篇 |
国内免费 | 1篇 |
学科分类
工业技术 | 671篇 |
出版年
2022年 | 10篇 |
2021年 | 10篇 |
2020年 | 6篇 |
2019年 | 8篇 |
2018年 | 5篇 |
2017年 | 6篇 |
2016年 | 5篇 |
2015年 | 7篇 |
2014年 | 14篇 |
2013年 | 26篇 |
2012年 | 25篇 |
2011年 | 24篇 |
2010年 | 17篇 |
2009年 | 21篇 |
2008年 | 22篇 |
2007年 | 31篇 |
2006年 | 28篇 |
2005年 | 26篇 |
2004年 | 16篇 |
2003年 | 17篇 |
2002年 | 22篇 |
2001年 | 16篇 |
2000年 | 13篇 |
1999年 | 14篇 |
1998年 | 13篇 |
1997年 | 12篇 |
1996年 | 18篇 |
1995年 | 20篇 |
1994年 | 16篇 |
1993年 | 12篇 |
1992年 | 15篇 |
1991年 | 20篇 |
1990年 | 8篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 14篇 |
1976年 | 5篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1971年 | 8篇 |
排序方式: 共有671条查询结果,搜索用时 15 毫秒
101.
The hydration of layered double hydroxides (LDHs) was investigated by changing the interlayer anion species, the Mg/Al ratio of the LDH hosts and the relative humidity (RH). The anions were CO32−, Cl−, Br−, NO3−, I−, SO42−, and ClO4− (listed in the order of ion size, small to large) and LDHs with Mg/Al = 1.90 (LDH2) and 2.91 (LDH3) were used. Their XRD profiles were measured by an XRD diffractometer while controlling the RH in the range 0–95% at 25 °C. Only I−, SO42−, and ClO4− LDH2s and SO42− LDH3 showed a large step-wise basal-spacing expansion, 0.24–0.28 nm, under high RH conditions (> ca. 60%) probably due to the insertion of one water layer into the interlayer space. Such hydration occurred more favorably for the LDHs with larger anions and those with a higher layer charge (LDH2). Among them, I− and ClO4− LDH2s exhibited the second staging – alternate stacking of hydrated (H) and non-hydrated (NH) interlayers – in the intermediate RH region. 相似文献
102.
True constant strain rate tensile tests of polypropylene up to 2% initial strain were performed to investigate the strain rate dependency of the initial stress–strain gradient dσ/dε with the aid of “slack grip.” The experimental results fairly agree with even the simplest mechanical model analysis with three parameters, showing the conspicuous strain rate dependency on the initial stress–strain gradient dσ/dε. The limiting cases corresponding to zero strain rate and strain rate of infinite magnitude, both predicted by the analysis, were experimentally verified. 相似文献
103.
受到城市化和产业转型的影响,进入21世纪中国工业遗产面临严峻考验。10年后中国的城市规划进入增量规划向存量规划的转折期,土地的有效利用对象中工业用地首当其冲,这再次将工业遗产推向去与留的十字路口。如何在保护工业遗产价值的前提下有效利用工业用地是值得研究的课题。文章是关于存量规划时代如何保护工业遗产文化价值的思考。 相似文献
104.
A transmission electron microscope (TEM) sample for observing photocatalysis in a liquid was prepared by using N,N,N-trimetyl-N-propylammonium-bis(trifluoromethanesulfonyl)imide. The ionic liquid (IL) was used as a reaction solvent. Tetrachloroauric acid was dissolved in the IL as gold ion species. Rutile particles were added in the solution as a photocatalyst. The low vapor pressure of the IL enables a diffusing system in high vacuum of TEM. Rutile particles were UV irradiated in that liquid phase. After 3 h UV irradiation, a gold particle of 8 nm diameter was grown on the TiO2 surface. Photonucleation of Au/TiO2 system was discussed from the high-resolution TEM images. 相似文献
105.
Horie K Kimura H Ikegami T Iwatsuka A Saad N Fiehn O Tanaka N 《Analytical chemistry》2007,79(10):3764-3770
Theoretical calculations are presented to optimize modulation period for maximum total peak capacity in comprehensive two-dimensional HPLC (2D-HPLC) taking into account the effect of modulation on the apparent peak capacity of the first-dimension (1D) separation. Results indicate that modulation periods are most favorable when they are adjusted to approximately 2.2-4 times the standard deviation of a 1D peak in order to avoid excessively short run times at the second dimension (2D). Data are presented that effective peak capacities of several thousand in 60 min can be expected for practical 2D-HPLC conditions, utilizing 1D gradient elution followed by 2D isocratic elution, that remain at approximately 50-70% of the theoretical maximum peak capacity. This work suggests that lower modulation frequencies and longer 2D separation times than previously proposed are favorable under realistic chromatographic conditions, alleviating some practical problems associated with 2D-HPLC. 相似文献
106.
Shimoda H Tanaka J Seki A Honda H Akaogi S Komatsubara H Suzuki N Kameyama M Tamura S Murakami N 《Shokuhin eiseigaku zasshi. Journal of the Food Hygienic Society of Japan》2007,48(5):125-131
Alpha-Lipoic acid has recently been permitted for use in foodstuffs and is contained in tablets and capsules. Although alpha-lipoic acid is synthesized from adipic acid, the safety of polymers produced during the purification and drying processes has been an issue of concern. Hence, we examined the safety profiles of thermally denatured polymer (LAP-A) and ethanol-denatured polymer (LAP-B) produced in the manufacturing process of alpha-lipoic acid. Furthermore, we conducted structural analysis of these polymers by 1H-NMR and FAB-MS spectroscopy. In a consecutive ingestion test, male and female mice ingested diet containing 0.1 and 0.2% LAP-A and -B for 4 weeks. Blood uric acid, potassium and lactate dehydrogenase (LDH) tended to increase without dose-dependency. Relative liver weights were also increased. However, male dogs that were orally administered LAP-B (500 mg/kg) once did not show any abnormalities in blood parameters or general condition. These findings indicate that alpha-lipoic acid polymers are not acutely toxic; however, chronic ingestion of these polymers may affect liver and kidney functions. 相似文献
107.
Jun-Ichi Kodama Takefumi Tsuboi Nobuo Okamoto 《Journal of Electronic Materials》1999,28(12):1461-1465
We previously reported on an extremely small temperature coefficient of resistivity (TCR) of thin amorphous Ni-Si film resistors
fabricated by new flash evaporating method, which have a wide range of resistivity.1 In the present paper, we describe the structural and chemical properties of these films for the purpose of clarifying the
cause of resistive change of films resulting from heat treatment. X-ray diffraction patterns show that Ni-Si films with greater
than 20 wt.% Si remains predominantly amorphous after heat treatment. Changes in composition and binding energy of the films
resulting from heat treatment are measured by means of XPS. Electrical characteristics are also investigated as a function
of Si concentration and temperature. The resistance variations resulting from heat treatment are found to originate from a
structural change. The activation energy needed for this change is obtained by analyzing the extent of change during isothermal
heating and found to vary from 1 eV to 2.5 eV with increasing Si content from 20 wt.% to 80 wt.%. 相似文献
108.
109.
By means of gel permeation chromatography analysis, the molecular weights and molecular weight distributions of liquefied wood obtained under various liquefaction conditions and species of catalysts were investigated in order to trace the change in the structural characteristics of the liquefied wood. The results indicated that during the liquefaction reaction, wood components were subjected to decomposition, phenolation, and recondensation. The intensities of these reactions depended greatly on the reaction conditions and the species of catalysts, and their competing result determined the structural characteristics of the resulting liquefied wood. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 351–357, 1997 相似文献
110.
Superhydrophobic/superhydrophilic micropatterning on a carbon nanotube (CNT) film has been achieved using a laser plasma-type hyperthermal atom beam facility, which produces a small amount of damage and generates a highly anisotropic beam. Fluorination and oxidation on CNT films by exposure to fluorine-atom and oxygen-atom beams caused superhydrophobic and superhydrophilic surfaces, respectively, while maintaining the as-grown fibrous forms of the CNT films. Micropatterned oxidation on CNT films without using photoresists created superhydrophilic microdots and microchannels. 相似文献