全文获取类型
收费全文 | 5772篇 |
免费 | 117篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 323篇 |
综合类 | 12篇 |
化学工业 | 1147篇 |
金属工艺 | 128篇 |
机械仪表 | 111篇 |
建筑科学 | 92篇 |
矿业工程 | 1篇 |
能源动力 | 182篇 |
轻工业 | 426篇 |
水利工程 | 16篇 |
石油天然气 | 3篇 |
无线电 | 571篇 |
一般工业技术 | 936篇 |
冶金工业 | 1455篇 |
原子能技术 | 152篇 |
自动化技术 | 344篇 |
出版年
2023年 | 25篇 |
2022年 | 60篇 |
2021年 | 96篇 |
2020年 | 33篇 |
2019年 | 63篇 |
2018年 | 69篇 |
2017年 | 47篇 |
2016年 | 71篇 |
2015年 | 81篇 |
2014年 | 83篇 |
2013年 | 217篇 |
2012年 | 164篇 |
2011年 | 238篇 |
2010年 | 182篇 |
2009年 | 190篇 |
2008年 | 200篇 |
2007年 | 200篇 |
2006年 | 197篇 |
2005年 | 141篇 |
2004年 | 140篇 |
2003年 | 162篇 |
2002年 | 120篇 |
2001年 | 140篇 |
2000年 | 119篇 |
1999年 | 176篇 |
1998年 | 550篇 |
1997年 | 375篇 |
1996年 | 282篇 |
1995年 | 158篇 |
1994年 | 158篇 |
1993年 | 153篇 |
1992年 | 90篇 |
1991年 | 74篇 |
1990年 | 73篇 |
1989年 | 76篇 |
1988年 | 66篇 |
1987年 | 45篇 |
1986年 | 59篇 |
1985年 | 53篇 |
1984年 | 54篇 |
1983年 | 37篇 |
1982年 | 50篇 |
1981年 | 36篇 |
1980年 | 42篇 |
1979年 | 34篇 |
1978年 | 28篇 |
1977年 | 38篇 |
1976年 | 53篇 |
1975年 | 20篇 |
1973年 | 28篇 |
排序方式: 共有5899条查询结果,搜索用时 15 毫秒
91.
Silica-supported cobalt catalysts for the selective reduction of nitrogen monoxide with propene 总被引:1,自引:0,他引:1
Megumu Inaba Yoshiaki Kintaichi Masaaki Haneda Hideaki Hamada 《Catalysis Letters》1996,39(3-4):269-274
Catalytic behavior of silica-supported transition metals for NO reduction with propene in the presence of oxygen was investigated. While both silica and cobalt oxides did not show any activity for the selective NO reduction, impregnated CoO/SiO2 prepared from cobalt acetate showed good activity although the preparation conditions had significant effect on the activity. It was suggested that highly dispersed surface Co2+ ions on silica are responsible for the catalytic activity. 相似文献
92.
The matrix concept was used to characterize the chromatographic rules in the elution of molecular species of triglyceride.
To prove the hypothesis experimentally, cacao butter, palm oil, linseed oil, olive oil, rapeseed oil and triglyceride of “Ogonori”
(Gracilaria verrucosa) were examined. A matrix model was suggested to help determine the individual molecular species of naturally occurring triglycerides. 相似文献
93.
Hajime Arai Masayuki Tsuda Masahiko Hayashi Hideaki Ohtsuka Yoji Sakurai 《Electrochimica acta》2005,50(9):1821-1828
Several polymorphs of layered nickel dioxide were prepared by using the chemical insertion of alkaline ions into Li0.10NiO2. We used aqueous AOH (A = Li, Na, K) solutions as reducing agents. Sodium and potassium insertion resulted in hydrated layered compounds that can be classified as γ-NiOOH with high crystallinity, while lithium insertion occurred without hydration. We discuss the coordination environment around the A+ ions for these inserted compounds. The thermal behavior, analyzed using high temperature (HT) X-ray diffraction (XRD) and thermogravimetric (TG) measurements, indicated that heating the hydrate at 150 °C yielded its dehydrate. The electrode performance of the nickelate was studied in lithium cells. We discuss the effect of interlayer water on cell rechargeability and the similarity between these nickelate and hydrated manganese dioxide (birnessite). 相似文献
94.
Studies are reported of the effect of an essential fatty acid (EFA) deficiency on synthesis of triglycerides (TG) and phospholipids
(PL) and secretion of these compounds by livers of male Sprague-Dawley rats. Animals were fed a semipurified diet containing
corn oil or hydrogenated coconut oil (HCO) as the sole source of fat or no fat from weaning to 20 weeks of age. Liver function
of the animals in each group was compared by an isolated liver perfusion technique with perfusates containing erythrocytes
and linoleate, and in vivo experiments via tail vein injection of palmitate-3H. Perfusion experiments showed that an EFA deficiency reduced the ability of the liver to secrete TG and PL. Accumulation
of TG in the liver and its diminished secretion into the blood of EFA deficient animals were demonstrated by in vivo experiments
with palmitate-3H. The rate of conversion of linoleate to arachidonate and synthesis of PL was greater in livers of EFA deficient rats than
in the control, corn oil fed animals. The results suggest a relationship of EFA metabolism to lipid transport.
One of five papers to be published from the Symposium “Lipid Transport” presented at the AOCS Meeting, New Orleans, April
1970. 相似文献
95.
J. Kurashige N. Matsuzaki H. Takahashi 《Journal of the American Oil Chemists' Society》1993,70(9):849-852
The bioreactor system to interesterify edible oils and fats at an ultra-micro aqueous phase of 100 ppm and less was investigated.
The adsorption of lecithin, together with lipase onto a carrier, was effective for conducting the interesterifying reaction
efficiently for oils and fats in micro aqueous phase.
To improve the handling properties of palm oil at rather low temperature, palm oil was blended with canola or soybean oil,
and then these blended oils were modified by enzymatic selective interesterification in a solvent-free, ultra-micro aqueous
bioreactor system with an immobilized lipase that had 1,3-positional specificity. The effects of enzymatic interesterification
were confirmed by triglyceride determination, by solid fat content profiles and by cloud point profiles, which were also compared
to products of chemical interesterification. The improvement in the fluidity of blended oils with canola oil by the enzymatic
reaction was bigger than with soybean oil, and chemical interesterification had no effects on the fluidity of blended oils. 相似文献
96.
Masaru Takahashi Noriyuki Inoue Tatsuya Takeguchi Shinji Iwamoto Masashi Inoue Tsunenori Watanabe 《Journal of the American Ceramic Society》2006,89(7):2158-2166
The reaction of mixtures of aluminum isopropoxide and gallium acetylacetonate in 1,4-butanediol or 1,5-pentanediol at high temperatures (glycothermal reaction) directly gave the γ-Ga2 O3 –Al2 O3 solid solutions, which had high catalytic activities for selective reduction of NO using methane as the reducing agent. However, the reaction with a higher Al/(Ga+Al) charged ratio yielded the glycol derivative of boehmite as a by-product and the catalytic activity of the solid solution decreased. Therefore, synthesis of the solid solution using various glycols was examined and it was found that solid solutions with high Al contents without contamination of the glycol derivative of boehmite were obtained by using 1,6-hexanediol as a reaction medium. The solid solution exhibited a higher NO conversion than that synthesized in other glycols. 相似文献
97.
In order to examine the conduction behaviour in the sintered oxides of MoO3-doped Bi2O3, the electrical conductivity in air and the EMF of oxygen gas concentration cell were measured with respect to the phase relation determined by X-ray diffraction.The tetragonal single phase oxide containing 22 mol% MoO3 was found to be a high oxide ion conductor, the conductivity of which was comparable to those of stabilized zirconias. The partial electronic conduction in this phase was negligibly small at relatively high oxygen pressure. The oxide ion conduction was considered to be attributable to an appreciable amount of oxygen vacancies present in the crystal. In the monoclinic compound 3Bi2O3·2MoO3, the oxide ion conduction was also observed. Although the conductivity of this phase was somewhat lower than that of the tetragonal phase, the activation energy for conduction (53·5 kJ mol–1) was much lower than the values for usual oxide ion conductors. 相似文献
98.
Viscoelastic properties of poly(isoprene-b-styrene) in dioctylphthalate under steady shear flow were measured near the order—disorder transition temperature. In ordered states, first normal stress difference N1 is proportional to shear rate
at low
region, but becomes proportional to
at the high
region, similar to the N1 behaviour of polymer blends undergoing shear-induced homogenization. Because the existence of microdomains was confirmed at the high
region by the flow birefringence method, it is concluded that the above N1 behaviour is not caused by shear-induced homogenization, but is probably caused by the shear-induced alignment of the microdomain structure. 相似文献
99.
Kojiro Nakai Yasunori Oumi Haruyuki Horie Tsuneji Sano Hideaki Yoshitake 《Microporous and mesoporous materials》2007,100(1-3):328-339
Bromination and subsequent ethylenediamine substitution of the CC double bond in mesoporous ethylenesilica were carried out to explore the characteristics of this periodic mesoporous organosilica. The structures of the products (BrPMO and EDA–BrPMO, respectively) were analysed by IR, Br K-edge EXAFS and NMR spectroscopies, as well as X-ray diffraction and nitrogen adsorption. We showed (1) that the formulae of the two products that formed were [CHBrSiO1.5]0.45[CHSiO1.5]0.55 and [NH2CH2CH2NHCHSiO1.5]0.05 [CHBrSiO1.5]0.40[CHSiO1.5]0.55, respectively, (2) that the addition of Br2 at room temperature occurred on the CC double bonds with disturbing the framework structure, (3) that IR absorption band of CC bonds that reacted with Br2 is significantly different from that of inactive CC bond, (4) that the length of the C–Br bond was considerably longer than in conventional alkyl bromides, and (5) that a large proportion of the ν(C–Br) band remained at the same position in the IR absorption spectrum after the ethylenediamine (EDA) substitution, while a new ν(C–Br) absorption also appeared. The mechanisms of these reactions are discussed at both the micro and mesoscopic levels.
Arsenate adsorption on EDA–BrPMO, in which the EDA is directly bound to the “surface” of the mesopores, was compared with adsorption on EDA–Pr–PMO, which was prepared by the direct synthesis of 3-chloropropyl-functionalized mesoporous ethanesilica followed by the substitution of Cl with EDA. The strength of the adsorption, as measured with the distribution coefficient, was greater for the former adsorbent than the latter. The origin of this difference was attributed to the distance between amino group and the surface. 相似文献
100.
The selective detection of acetylene in gases extracted from isolation oils has been studied to develop an electrochemical
sensor for the diagnostic monitoring of the condition of in-service electrical instruments. Effects of coexisting gases (CH4, C2H6, C2H4, H2 and CO) on the oxidation current of C2H2 were tested using gas-permeable gold-coated and platinum-black electrodes as the sensor. The gold-coated electrode showed
good behaviour for the selective current detection of acetylene under potentiostatic conditions (−0.1 V/Pt-black reference
electrode) in 10m H2SO4 electrolyte solution. 相似文献