全文获取类型
收费全文 | 2154篇 |
免费 | 32篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 160篇 |
综合类 | 1篇 |
化学工业 | 397篇 |
金属工艺 | 55篇 |
机械仪表 | 43篇 |
建筑科学 | 38篇 |
能源动力 | 76篇 |
轻工业 | 144篇 |
水利工程 | 11篇 |
石油天然气 | 4篇 |
无线电 | 173篇 |
一般工业技术 | 383篇 |
冶金工业 | 457篇 |
原子能技术 | 95篇 |
自动化技术 | 155篇 |
出版年
2023年 | 5篇 |
2022年 | 21篇 |
2021年 | 41篇 |
2020年 | 10篇 |
2019年 | 16篇 |
2018年 | 26篇 |
2017年 | 24篇 |
2016年 | 21篇 |
2015年 | 24篇 |
2014年 | 32篇 |
2013年 | 104篇 |
2012年 | 65篇 |
2011年 | 99篇 |
2010年 | 74篇 |
2009年 | 90篇 |
2008年 | 92篇 |
2007年 | 88篇 |
2006年 | 68篇 |
2005年 | 64篇 |
2004年 | 56篇 |
2003年 | 71篇 |
2002年 | 48篇 |
2001年 | 45篇 |
2000年 | 56篇 |
1999年 | 49篇 |
1998年 | 192篇 |
1997年 | 122篇 |
1996年 | 78篇 |
1995年 | 64篇 |
1994年 | 45篇 |
1993年 | 53篇 |
1992年 | 30篇 |
1991年 | 22篇 |
1990年 | 23篇 |
1989年 | 25篇 |
1988年 | 19篇 |
1987年 | 12篇 |
1986年 | 21篇 |
1985年 | 29篇 |
1984年 | 9篇 |
1983年 | 13篇 |
1982年 | 23篇 |
1981年 | 19篇 |
1980年 | 16篇 |
1979年 | 8篇 |
1978年 | 12篇 |
1977年 | 16篇 |
1976年 | 21篇 |
1975年 | 6篇 |
1974年 | 8篇 |
排序方式: 共有2192条查询结果,搜索用时 15 毫秒
51.
Tsuyoshi Asakawa Hidefumi Takeda Shigeyoshi Miyagishi Morie Nishida 《Journal of the American Oil Chemists' Society》1986,63(11):1479-1482
The qualitative and quantitative determination of anionic surfactants (sodium and lithium alkylsulfate, sodium dodecylbenzenesulfonate,
sodium di-2-ethylhexyl sulfosuccinate, sodium and lithium perfluoroalkylcarboxylate, and lithium perfluorooctanesulfonate)
were investigated by a capillary tube isotachophoresis using a potential gradient detector. The leading electrolyte solution
was the mixture of acetonitrile and aqueous solution of histidine buffer containing calcium chloride. The terminating electrolyte
solution was the aqueous solution of sodium octanoate. These electrolytes were effective for the analysis of the mixtures
of strongly acidic surfactants. 相似文献
52.
Kunihito Koumoto Shunji Takeda Chul Hoon Pai Takayori Sato Hiroaki Yanagida 《Journal of the American Ceramic Society》1989,72(10):1985-1987
Structural images of the stacking faults in β-SiC were obtained with a high-resolution electron microscope. Stacking faults initially present in β-SiC powder particles were eliminated as grain growth proceeded at elevated temperatures. 相似文献
53.
Antioxidant effects of chlorophyll and pheophytin on the autoxidation of oils in the dark. I. Comparison of the inhibitory effects 总被引:1,自引:0,他引:1
Yasushi Endo Richiro Usuki Takashi Kaneda 《Journal of the American Oil Chemists' Society》1985,62(9):1375-1378
The effects of chlorophyll and pheophytin on the autoxidation of oils in the dark were investigated by oven tests. The results
indicated that both chlorophyll and pheophytin show antioxidant activity when methyl linoleate is used as substrate. Furthermore,
chlorophyll retarded the oxidative deterioration of triglycerides in rapeseed and soybean oils at 30 C. Among the four chlorophyll
derivatives (chlorophylls a and b and pheophytins a and b), chlorophyll a showed the strongest antioxidant activity. The antioxidant
effects of chlorophyll and pheophytin depended on the storage temperature and the kinds of oil used as substrate. 相似文献
54.
Yasushi Endo Sanae Hoshizaki Kenshiro Fujimoto 《Journal of the American Oil Chemists' Society》1997,74(9):1041-1045
Thirteen synthetic triacylglycerols (TAG) containing eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) were oxidized
in the presence of 2,2′-azobis(2,4-dimethyl-valeronitrile) (AMVN) and 2,2′-azobis(2-amidinopropane)dihydrochloride (AAPH)
as aqueous and nonaqueous radical initiators to investigate the influence of TAG structure and oxidation system on the oxidative
stability of TAG that contain highly unsaturated fatty acids (HUFA). A 2:1 (mol/mol) mixture of trieicosapentaenoylglycerol
and tripalmitoylglycerol was most susceptible to the AMVN-initiated oxidation among three types of TAG that contained EPA
and palmitic acid (2:1, mol/mol). Compared with 1,2 (or 2,3)-dieicosapentaenoyl-3(or 1)-palmitoylglycerol (EEP) and 1,3-dieicosapentaenoyl-2-palmitoylglycerol
(EPE), the oxidative rate of EEP was somewhat higher. A similar result was obtained for DHA-containing TAG. The oxidative
rate of TAG that contained EPA and palmitic acid (1:2, mol/mol) showed a positive correlation with the amount of EPA in a
single TAG molecule. Moreover, in the nonaqueous system, the oxidative rate of EPA-containing TAG was affected by unsaturation
and carbon chainlength of constituent fatty acids. In the AAPH-initiated oxidation in the aqueous system, the oxidative rate
of TAG with EPA and palmitic acid was higher with the increased quantity of EPA in a single TAG molecule. Also, constituent
fatty acids modified the oxidative rate of EPA-containing TAG in an aqueous system. The glycerol position of EPA and DHA also
affected the oxidative rate of the TAG. EPA and DHA located at the 1,2 (or 2,3)-position of glycerol were more oxidizable
than those at the 1,3-position during AAPH-initiated oxidation. Thus, 1,2(or2,3)-dipalmitoyl-3(or 1)-eicosapentaenoylglycerol
was oxidized faster than 1,3-dipalmitoyl-2-eicosapentaenoylglycerol. These observations suggest that the oxidative stability
of TAG that contain HUFA could be modulated by the oxidation system and TAG structure. 相似文献
55.
Noboru Hashimoto Yasushi Sawada Takashi Bando Hiroyoshi Yoden Shigehito Deki 《Journal of the American Ceramic Society》1991,74(6):1282-1286
AIN powder was synthesized from aluminum polynuclear complexes. Basic aluminum chloride and basic aluminum lactate were used as the aluminum polynuclear complexes. These starting materials and glucose were dissolved in water and mixed homogeneously. AIN powder was obtained by calcining after drying and precalcining at 800°C under nitrogen gas flow. Then excess carbon was removed by firing in air. Nitridation in the system was investigated and compared with that in the alumina–carbon black system. It was found that in our reaction system nitridation began and proceeded at lower calcination temperatures above 1200°C than in the alumina–carbon black system. Using aluminum polynuclear complexes, AIN was synthesized through the nitridation of γ-alumina and produced in a very fine and sharp particle size distribution. 相似文献
56.
Tetsuto Kanzaki Yo Ishikawa Nobuhiro Morisaki Kohji Shirai Yasushi Saito Sho Yoshida 《Lipids》1987,22(10):704-710
Studies were done on changes in phospholipid content and fatty acid composition of phospholipids and on the role of the acylation
pathway in synthesis of phospholipids in the development of abnormal fatty acid composition in the glomeruli of rats 2 and
10 mo after induction of diabetes with streptozotocin. The proportions of individual phospholipids in the glomeruli of rats
were not changed 2 mo after induction of diabetes, but the proportion of phosphatidylethanolamine (PE) decreased and that
of sphingomyelin increased 10 mo after induction of diabetes. In contrast, in liver the proportion of PE was increased and
that of phosphatidylcholine was decreased. These results showed that changes of individual phospholipids in glomeruli were
time-dependent and tissue-specific. Two mo after induction of diabetes, the main change in the phospholipid fatty acid composition
of diabetic glomeruli was a decrease in arachidonic acid (AA); the main change in serum free fatty acids (FFA) was an increase
in linoleic acid (LA) and a decrease in AA. Ten mo after induction of diabetes, the main changes in the phospholipid fatty
acid composition of glomeruli were an increase in LA and a decrease in AA; the main change of the serum FFA composition was
a decrease in AA. Thus, the fatty acid composition of glomerular phospholipids was not directly correlated to that of the
serum in diabetic rats. Acyl-CoA synthetase and acyltransferase activities increased in diabetic glomeruli with either AA
or LA as substrate, but activity toward LA increased more at 2 mo after induction of diabetes. Acyl-CoA synthetase activity
increased in diabetic glomeruli with LA as substrate, but that did not change with AA as substrate at 10 mo after induction
of diabetes. Furthermore, acyltransferase activity decreased in diabetic glomeruli with AA as substrate, although that did
not change with LA as substrate at 10 mo after induction of diabetes. 相似文献
57.
Retardation of volatile aldehyde formation in the exhaust of frying oil by heating under low oxygen atmospheres 总被引:2,自引:0,他引:2
Mariko?Fujisaki Yasushi?Endo Kenshiro?FujimotoEmail author 《Journal of the American Oil Chemists' Society》2002,79(9):909-914
Volatile aldehydes were generated in the exhaust of high-oleic safflower oil during heating at 180°C by spraying water into
atmospheres with four levels of oxygen concentrations (2, 4, 10, and 20%). These aldehydes were quantitatively analyzed by
HPLC after the conversion to 2,4-dinitrophenyl hydrazones. Ten alkanals (C2 through C10), eight 2-alkenals (C3 through C10) and three 2,4-alkadienals (C7, C9, and C10) were found. These aldehyde levels were found to be positively correlated with both the heating time and the atmospheric
oxygen concentration. The total amounts of aldehydes were the lowest in the oil heated in an atmosphere with 2% O2, and corresponded to 1/10 of those in the atmosphere with 20% O2. Acrolein was not found in oils heated in the atmosphere with 2% oxygen. These results suggest that frying in atmospheres
with low oxygen levels can effectively decrease the generation of volatile aldehydes in the exhaust. 相似文献
58.
Bis-(monoacylglyceryl) phosphate and acyl phosphatidylglycerol were isolated from the liver of two patients with lipidosis
induced by 4,4′-diethylaminoethoxyhexesterol. Identification was based upon the results of alkaline hydrolysis, acetolysis,
IR spectrometry, and upon the determination of molar ratio of phosphorus-glycerol-ester. The contents of the bis-(monoacylglyceryl)
phosphate were 10 and 16% total phospholipid phosphorus in them. The bis-(monoacylglyceryl) phosphate contained mainly docosahexaenoic
(42%), oleic (29%), and linoleic acid (14%) and had the hemolytic activity of ca. one-eighth lysolecithin from egg yolk. Acidic
lipids from the liver also were found to contain a lipid which is less polar than bis-(monoacylglyceryl) phosphate. The results
of lipid analysis showed that the lipid possessed the structure of an acyl phosphatidylglycerol, and its content was ca. 2%
total phospholipid phosphorus. Accumulation of 4,4′-diethylaminoethoxyhexesterol and its derivatives was found in clinical
cases by thin layer chromatography and IR spectrometry. This fact suggested that human liver has an ability to metabolize
the drug. 相似文献
59.
Yujiro Watanabe Yusuke Moriyoshi Yasushi Suetsugu Toshiyuki Ikoma Takeshi Kasama Tadashi Hashimoto Hirohisa Yamada Junzo Tanaka 《Journal of the American Ceramic Society》2004,87(7):1395-1397
Type-A zeolite evenly covered with hydroxyapatite thin layers was prepared using hydrothermal treatment at 120°C for 8 h under autogenous pressure. The hydroxyapatite needlelike nanocrystals, 100–200 nm in diameter and 30 nm in thickness, were grown under the reaction between discharged Ca2+ ions from type-A zeolite and PO4 3− ions in (NH4 )3 PO4 solution. The preferential orientations of the c -axis of hydroxyapatite crystals perpendicular to a zeolite surface were observed using transmission electron microscopy. The crystal structure of type-A zeolite was not destroyed under the reaction, but the surface morphology was changed only with complete covering of scaly hydroxyapatite particles. 相似文献
60.
Yasushi Endo Riichiro Usuki Takashi Kaneda 《Journal of the American Oil Chemists' Society》1985,62(9):1387-1390
To understand the mechanism of the antioxidant effect of chlorophyll on the autoxidation of oils in the dark, antioxidant
activities of several derivatives of chlorophyll were compared. Antioxidant activities were observed in chlorophyll derivatives
such as protopor-phyrin methyl ester and its magnesium chelated compound. Porphyrin seems to be an essential chemical structure
for the antioxidant activity of chlorophyll. Chlorophyll did not decompose the hydroperoxides, but reduced free radicals such
as 1,1-diphenyl-2-picrylhydrazyl. Electron spin resonance spectrum of the π-cation radical was recorded during the oxidation
of chlorophyll in methyl linoleate solution. These observations suggest that chlorophyll may act as a hydrogen donor to break
the chain reaction. 相似文献