全文获取类型
收费全文 | 1277篇 |
免费 | 21篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 47篇 |
综合类 | 3篇 |
化学工业 | 368篇 |
金属工艺 | 93篇 |
机械仪表 | 43篇 |
建筑科学 | 30篇 |
能源动力 | 73篇 |
轻工业 | 61篇 |
石油天然气 | 2篇 |
无线电 | 56篇 |
一般工业技术 | 237篇 |
冶金工业 | 113篇 |
原子能技术 | 59篇 |
自动化技术 | 118篇 |
出版年
2023年 | 4篇 |
2022年 | 9篇 |
2021年 | 22篇 |
2020年 | 11篇 |
2019年 | 10篇 |
2018年 | 25篇 |
2017年 | 17篇 |
2016年 | 30篇 |
2015年 | 6篇 |
2014年 | 28篇 |
2013年 | 78篇 |
2012年 | 55篇 |
2011年 | 70篇 |
2010年 | 80篇 |
2009年 | 65篇 |
2008年 | 59篇 |
2007年 | 51篇 |
2006年 | 63篇 |
2005年 | 38篇 |
2004年 | 41篇 |
2003年 | 39篇 |
2002年 | 41篇 |
2001年 | 37篇 |
2000年 | 20篇 |
1999年 | 27篇 |
1998年 | 52篇 |
1997年 | 31篇 |
1996年 | 29篇 |
1995年 | 27篇 |
1994年 | 15篇 |
1993年 | 16篇 |
1992年 | 12篇 |
1991年 | 16篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 14篇 |
1987年 | 8篇 |
1986年 | 11篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 11篇 |
1982年 | 14篇 |
1981年 | 10篇 |
1980年 | 16篇 |
1979年 | 12篇 |
1978年 | 8篇 |
1977年 | 11篇 |
1976年 | 4篇 |
1975年 | 7篇 |
1973年 | 4篇 |
排序方式: 共有1303条查询结果,搜索用时 0 毫秒
31.
Inside Cover: Onocerin Biosynthesis Requires Two Highly Dedicated Triterpene Cyclases in a Fern Lycopodium clavatum (ChemBioChem 4/2016) 下载免费PDF全文
32.
33.
WO3 films have been prepared on to IrO2-coated Ti substrate by cathodic deposition, and as-deposited and annealed films have been characterized using XRD, TEM, Raman and FT-IR spectroscopy. The as-deposited film consists of nanocrystalline, orthorhombic WO3·H2O and this phase transforms to amorphous WO3 by annealing at 250 °C and to monoclinic WO3 by annealing at and above 350 °C. The as-deposited and annealed films have been used as anodes for electrochemical decomposition of phenol in aqueous solutions with and without chloride ions. The monoclinic WO3 anodes prepared by annealing at 350 and 400 °C show relatively high electrochemical activity in the chloride-containing solution. In addition, the anodes possess high chemical and physical stabilities: very low dissolution rate of WO3 during the electrolysis and good adhesion to the substrate. Thus, WO3 anodes may be promising materials for anodic oxidation of bio-refractory organics in wastewater, although further improvement of electrochemical activity is needed for more effective decrease in total organic carbons in wastewater. 相似文献
34.
Selectivity and mechanism for skeletal isomerization of alkanes over typical solid acids and their Pt-promoted catalysts 总被引:2,自引:0,他引:2
Atsuyuki Miyaji Tsuneo Echizen Lianshun Li Tetsuo Suzuki Yusuke Yoshinaga Toshio Okuhara 《Catalysis Today》2002,74(3-4):291-297
Selectivities for skeletal isomerizations of n-butane and n-pentane catalyzed by typical solid acids such as Cs2.5H0.5PW12O40 (Cs2.5), SO42−/ZrO2, WO3/ZrO2, and H-ZSM-5 and their Pt-promoted catalysts were compared. High selectivities for n-butane and low selectivity for n-pentane were observed over Cs2.5 and SO42−/ZrO2, while H-ZSM-5 was much less selective, and WO3/ZrO2 was highly selective for both reactions. The Pt-promoted solid acids were usually selective for these reactions in the presence of H2 except for Pt-H-ZSM-5 for n-butane isomerization. Both the acid strength and pore structure would be factors influencing the selectivity. Mechanism of skeletal isomerization of n-butane was investigated by using 1,4-13C2-n-butane over Cs2.5 and Pt–Cs2.5. It was concluded that n-butane isomerization proceeded mainly via monomolecular pathway with intramolecular rearrangement on Pt–Cs2.5, while it occurred through bimolecular pathway with intermolecular rearrangement on Cs2.5. The higher selectivity on Pt–Cs2.5 would be brought about by the monomolecular mechanism. In the skeletal isomerization of cyclohexane, Pt–Cs2.5/SiO2 was highly active and selective, while Pt–Cs2.5 was less selective. Control in the acid strength of Cs2.5 by the supporting would be responsible for the high selectivity. 相似文献
35.
Fengqiu Tang Tetsuo Uchikoshi Yoshio Sakka 《Journal of the American Ceramic Society》2002,85(9):2161-2165
The rheological behavior and electrophoretic deposition (EPD) of ZnO nanopowder (nano-ZnO) in aqueous media have been described. A cationic polyelectrolyte (polyethylenimine, PEI) was used to disperse and modify the surfaces of the ZnO nanoparticles. The rheological properties of the ZnO aqueous suspension were investigated by measuring the viscosity versus the pH and amount of dispersant. The EPD processing was conducted via cathodic electrodeposition, using stable suspensions with low viscosity, and the depositional behavior was investigated. Bubble-free nano-ZnO deposits with uniform microstructures were successfully obtained, which was an indication of good sintering behavior. 相似文献
36.
Tetsuo Asakura Motohiro Kitaguchi Makoto Demura Harutoshi Sakai Keiichi Komatsu 《应用聚合物科学杂志》1992,46(1):49-53
The enzyme glucose oxidase (GOD) was immobilized on the nonwoven fabrics, which have excellent properties in diffusivity of substrates, mechanical strength, and handling, with Bombyx mori silk fibroin gel. The nonwoven fabrics of silk fibroin, viscose rayon, poly-ethyleneterephthalate, 6-nylon, and polypropylene with activated surface by fluoline treatment were used. The stabilities of GOD to heat or pH changes were much improved by the immobilization as well as the case of the GOD immobilized in the silk fibroin membrane. Among nonwoven fabrics, silk fibroin was the most excellent support material for the immobilization of GOD although all nonwoven fabrics used here are able to be used as the support materials. The increase of the sensitivity was observed when the glucose sensor was made with the GOD immobilized on nonwoven silk fabrics as four times compared with the case of the GOD immobilized in the silk fibroin membrane. 相似文献
37.
Kaoru Higaki Satoru Ueno Tetsuo Koyano Kiyotaka Sato 《Journal of the American Oil Chemists' Society》2001,78(5):513-518
Effects of application of ultrasonic power (20 kHz, 100 W) on the crystallization behavior of tripalmitoylglycerol (PPP) and
cocoa butter have been examined in terms of rate of nucleation and polymorphic control. High-purity PPP (>99%) and low-purity
PPP (>80%) samples were employed to mimic real fat systems, which usually have higher concentrations of minor components in
addition to the main component. For both the high-purity and low-purity PPP, the application of ultrasonic power accelerated
the rate of nucleation as measured by induction time for the occurrence of crystals and by the number of crystals nucleated.
As for the polymorphic influences, the nucleation of both the β′ and β forms was accelerated by the ultrasound, yet the β′
form nucleation was more accelerated when the low-purity PPP samples were employed. As for cocoa butter, sonication for a
short period accelerated the crystallization of Form V. The present results indicate that ultrasound irradiation is an efficient
tool for controlling polymorphic crystallization of fats. 相似文献
38.
Takuji Yamamoto Tomofumi Nishimura Tetsuo Suzuki Hajime Tamon 《Drying Technology》2001,19(7):1319-1333
Resorcinol-formaldehyde hydrogels were synthesized by sol-gel polycondensation of resorcinol with formaldehyde in a slightly basic aqueous solution. RF cryogels, RF xerogels, and RF xerogels (MW gels) were respectively prepared from RF hydrogels by freeze drying, hot air drying, and microwave drying. Carbon cryogels, carbon xerogels and carbon MW gels were subsequently obtained by pyrolyzing RF drygels in an inert atmosphere. Freeze drying and microwave drying were effective to prepare mesoporous RF drygels and carbon gels. RF cryogels and carbon cryogels showed high mesoporosity over wide ranges of the molar ratio of resorcinol to catalyst (R/C) and the ratio of resorcinol to water (R/W) used in sol-gel polycondensation. Although RF xerogels had a few mesopores, carbon xerogels had no mesopores. RF MW gels and carbon MW gels showed mesoporosity if appropriate values of R/C and R/W were selected. 相似文献
39.
Masahiro Nagae Tetsuo Yoshio Yoshito Takemoto Jun Takada 《Journal of the American Ceramic Society》2001,84(5):1175-1177
For pure molybdenum nitrided at 1373 K in NH3 gas, microstructural observations of a molybdenum nitride layer were conducted through a transmission electron microscope. The molybdenum nitride layer consisted of two molybdenum nitrides: an outer one of γ-Mo2 N and an inner one of β-Mo2 N. A great number of (011)[0 1] type twins were observed in the β-Mo2 N phase, whereas the microstructure of the γ-Mo2 N phase was almost free from lattice defects except for slightly observed {111}〈112〉 type twin. 相似文献
40.
Phase Relations and Volume Changes of Hafnia under High Pressure and High Temperature 总被引:1,自引:0,他引:1
Osamu Ohtaka Hiroshi Fukui Taichi Kunisada Tomoyuki Fujisawa Kenichi Funakoshi Wataru Utsumi Tetsuo Irifune Koji Kuroda Takumi Kikegawa 《Journal of the American Ceramic Society》2001,84(6):1369-1373
Using multi-anvil high-pressure devices and synchrotron radiation, X-ray in situ observations of HfO2 under high pressure and high temperature have been performed to investigate its phase relations and compression behavior. An orthorhombic phase (orthoI) is stable from 4 to 14.5 GPa below 1250°–1400°C and transforms to a tetragonal phase, which is one of the high-temperature forms of HfO2 , above these temperatures. Another orthorhombic phase (orthoII) with a cotunnite-type structure appears above 14.5 GPa. OrthoII is stable up to 1800°C at 21 GPa. OrthoII is quenchable to ambient conditions. The orthoI-to-orthoII transition is accompanied by ∼8 vol% decrease. The bulk moduli of orthoI and orthoII at room temperature are 220 and 312 GPa, respectively. This low compressibility of orthoII indicates that it is a potential candidate for very hard materials. 相似文献