全文获取类型
收费全文 | 3501篇 |
免费 | 89篇 |
专业分类
电工技术 | 31篇 |
综合类 | 8篇 |
化学工业 | 574篇 |
金属工艺 | 54篇 |
机械仪表 | 75篇 |
建筑科学 | 96篇 |
矿业工程 | 14篇 |
能源动力 | 63篇 |
轻工业 | 462篇 |
水利工程 | 30篇 |
石油天然气 | 8篇 |
无线电 | 243篇 |
一般工业技术 | 478篇 |
冶金工业 | 1012篇 |
原子能技术 | 36篇 |
自动化技术 | 406篇 |
出版年
2022年 | 39篇 |
2021年 | 59篇 |
2020年 | 27篇 |
2019年 | 46篇 |
2018年 | 25篇 |
2017年 | 51篇 |
2016年 | 71篇 |
2015年 | 55篇 |
2014年 | 74篇 |
2013年 | 125篇 |
2012年 | 86篇 |
2011年 | 143篇 |
2010年 | 121篇 |
2009年 | 120篇 |
2008年 | 135篇 |
2007年 | 128篇 |
2006年 | 79篇 |
2005年 | 101篇 |
2004年 | 75篇 |
2003年 | 82篇 |
2002年 | 78篇 |
2001年 | 62篇 |
2000年 | 67篇 |
1999年 | 85篇 |
1998年 | 210篇 |
1997年 | 145篇 |
1996年 | 133篇 |
1995年 | 102篇 |
1994年 | 84篇 |
1993年 | 86篇 |
1992年 | 49篇 |
1991年 | 36篇 |
1990年 | 38篇 |
1989年 | 38篇 |
1988年 | 30篇 |
1987年 | 29篇 |
1986年 | 35篇 |
1985年 | 45篇 |
1984年 | 34篇 |
1983年 | 27篇 |
1980年 | 21篇 |
1978年 | 26篇 |
1977年 | 46篇 |
1976年 | 48篇 |
1975年 | 30篇 |
1974年 | 19篇 |
1972年 | 28篇 |
1971年 | 20篇 |
1970年 | 25篇 |
1969年 | 19篇 |
排序方式: 共有3590条查询结果,搜索用时 15 毫秒
51.
52.
53.
M A Rossi S Zucoloto J E Dutra de Oliveira P F Becker J S Oliveira 《Archivos latinoamericanos de nutrición》1978,28(1):29-40
A study of the effect of long-term alcohol consumption on the liver of well-nourished rats is described. Rats fed for 16 weeks on a semipurified diet supplemented with high levels of vitamins and lipotropic factors and alcohol corresponding to 35% of the total caloric intake developed marked fatty changes of the liver. Mild fatty changes were observed in pair-fed controls receiving as isoenergetic equivalent of sucrose instead of alcohol. Intracellular hyaline bodies, corresponding ultrastructurally to giant mitochondria were abundantly found in the hepatocytes of alcoholic rats, while in the controls they were not seen. Te findings in this investigation are postulated to provide further evidence that the long-term intake of alcohol exerts a direct causative role in the pathogenesis of liver damage. 相似文献
54.
H. R. Spiegel J. Juilfs U. Neubert K. J. Euler J. W. Beck D. Besdo H. Winter H. Becker W. Neuberger R. Jung K. Herfort H. Bühler H. Göppl H. W. Hahnemann W. Siegel 《Forschung im Ingenieurwesen》1970,36(2):64-68
Ohne Zusammenfassung
VDI 相似文献
55.
The effects of oxidation/reduction regeneration treatments, with and without 1,2-dichloropropane present as a chlorinating agent, on the structure of Pt(3%)–Sn(4.5%)/Al2O3 catalysts have been correlated with selectivities for butane/H2 reactions. Particles of Pt0 fin Cl-free catalysts were partly covered by Sn0, but retained exposed ensembles of Pt atoms which were active for isomerisation, hydrogenolysis and dehydrogenation reactions, the latter becoming dominant at high reaction temperatures. Coking reduced Pt ensemble size and, hence, also favoured high selectivities for dehydrogenation as hydrogenolysis and isomerisation sites became poisoned. In contrast, the addition of 1,2-dichloropropane in an oxychlorination step before reduction promoted 1:1 Pt0–Sn0 alloy formation after reduction, the proportion of the total Pt in alloy being enhanced by increasing 1,2-dichloropropane concentration and oxychlorination temperature. The alloy surfaces were inactive for isomerisation and hydrogenolysis reactions, giving dehydrogenation as the sole catalytic reaction. 相似文献
56.
Alveolar Type II cells in the rat respond to severe, acute ozone injury (3 ppm ozone for eight hours) by increasing their
intracellular pool of surfactant; however, the newly stored surfactant is abnormal in composition. Lamellar bodies isolated
between 24 and 96 hours after ozone exposure contained significantly more cholesterol in relation to phosphatidylcholine than
did controls. By contrast, the cholesterol content of surfactant isolated from alveolar lavage remained unchanged throughout
an 8-day post-ozone period. The total protein content of lamellar bodies in relation to phosphatidylcholine was significantly
decreased at 24 and 48 hours post-ozone. Analysis of lamellar body proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis
revealed that the amount of a 14 kDa proteolipid was greatly reduced at the end of the eight-hour ozone exposure and remained
low for at least 48 hours. This proteolipid appeared to be a specific lamellar body component since it was not detected in
extracellular surfactant. The findings indicate that oxidative alveolar stress initiates characteristic alterations in both
lipid and protein constituents of stored surfactant, without perturbation in the composition of extracellular surfactant. 相似文献
57.
Becker A. V. Polianczyk E. V. Volkova N. N. Manelis G. B. 《Theoretical Foundations of Chemical Engineering》2004,38(5):510-515
The kinetics of the overall reactions of carbon gasification at temperatures up to 1600 K is studied. The kinetic characteristics of the reactions are taken into account in a distributed mathematical model of filtration combustion of carbon. By computational experiment at different values of process control parameters (the gas flow rate, the fraction of the oxidant in the gas, and the mass ratio of carbon to the inert material in the combustible mixture), it is found that, in the wave of filtration combustion of carbon under superadiabatic conditions, carbon gasification can predominately yield either CO2 or CO. 相似文献
58.
Morphology and fracture mechanisms in two nanoclay‐filled epoxy systems were investigated using both microscopy and spectroscopy tools. Clay exfoliation was achieved using a series of sample preparation steps, and confirmed using wide angle X‐ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Significant improvement in modulus was obtained when clay exfoliation was achieved. Incorporation of core‐shell rubber (CSR) in both caly‐filled epoxy systems leads to greatly enhanced fracture toughness. Optical microscopy and TEM observations of the CSR‐modified nanocomposites suggest that CSR cavitation. shear yielding of the matrix, clay layer delamination. CSR bridging, crack bifurcation. and crack deflection are among the operative toughening mechanisms observed, depending on the nature of the epoxy matrix utilized. 相似文献
59.
The internal, copper-catalysed, addition of keto-carbenes (generated from a diazoketone group) to a double bond conjugated either to a ketone or carboxylic ester function has been found to be a feasible preparative reaction in selected cases. This, together with the facile and regiospecific hydrogenolysis of the resulting 1,2-dicarbonyl cyclopropane intermediate, appear to constitute a convenient route to multifunctional bridged-ring systems. 相似文献
60.
A good way of achieving compatibility in polymer blends of poly(styrene‐co‐acrylonitrile) (S/AN) and bisphenol A polycarbonate (PC) is the chemical modification of S/AN in the melt. A catalyzed reaction of the nitrile groups with a substituted 2‐amino alcohol or 2‐amino phenol resulted in a conversion of nitrile groups of 55–75% in 60 min. The introduced heterocyclic structures were ethyl hydroxymethyl oxazoline (EHMOXA) and benzoxazole (BenzOXA), respectively. The use of dibutyltin oxide as a catalyst led to the highest efficiency. The modified polymer was characterized by Fourier transform infrared and NMR spectroscopy, elemental analysis, and reactions with organic acids and anhydrides. The modified S/AN showed good technical compatibility (single glass‐transition temperature) with PC in blends made from solution and from the melt. All blends were characterized with oscillating rheometry and differential scanning calorimetry. Rheological measurements showed that EHMOXA–S/AN reacted with PC and had crosslinked structures, whereas BenzOXA–S/AN showed compatibilization without any (crosslinking) reaction. The melt blends of BenzOXA–S/AN and PC showed a downward shift in the complex viscosity due to the influence of the BenzOXA group. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2322–2332, 2003 相似文献