全文获取类型
收费全文 | 27385篇 |
免费 | 1737篇 |
国内免费 | 28篇 |
专业分类
电工技术 | 168篇 |
综合类 | 11篇 |
化学工业 | 5722篇 |
金属工艺 | 430篇 |
机械仪表 | 566篇 |
建筑科学 | 827篇 |
矿业工程 | 55篇 |
能源动力 | 542篇 |
轻工业 | 5629篇 |
水利工程 | 309篇 |
石油天然气 | 124篇 |
武器工业 | 1篇 |
无线电 | 1107篇 |
一般工业技术 | 4442篇 |
冶金工业 | 5525篇 |
原子能技术 | 68篇 |
自动化技术 | 3624篇 |
出版年
2024年 | 66篇 |
2023年 | 282篇 |
2022年 | 299篇 |
2021年 | 744篇 |
2020年 | 665篇 |
2019年 | 683篇 |
2018年 | 1254篇 |
2017年 | 1220篇 |
2016年 | 1286篇 |
2015年 | 987篇 |
2014年 | 1128篇 |
2013年 | 2345篇 |
2012年 | 1805篇 |
2011年 | 1605篇 |
2010年 | 1298篇 |
2009年 | 1138篇 |
2008年 | 1177篇 |
2007年 | 1077篇 |
2006年 | 696篇 |
2005年 | 581篇 |
2004年 | 545篇 |
2003年 | 521篇 |
2002年 | 441篇 |
2001年 | 334篇 |
2000年 | 271篇 |
1999年 | 324篇 |
1998年 | 1941篇 |
1997年 | 1218篇 |
1996年 | 747篇 |
1995年 | 413篇 |
1994年 | 317篇 |
1993年 | 334篇 |
1992年 | 91篇 |
1991年 | 82篇 |
1990年 | 66篇 |
1989年 | 60篇 |
1988年 | 83篇 |
1987年 | 74篇 |
1986年 | 63篇 |
1985年 | 73篇 |
1984年 | 62篇 |
1983年 | 36篇 |
1982年 | 37篇 |
1981年 | 66篇 |
1980年 | 61篇 |
1977年 | 109篇 |
1976年 | 214篇 |
1975年 | 33篇 |
1974年 | 34篇 |
1973年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Clara G. Soubelet María P. Albano 《International Journal of Applied Ceramic Technology》2020,17(3):1141-1154
Well-dispersed concentrated aqueous suspensions of Al2O3-doped Y-TZP (AY-TZP), AY-TZP with 5.4 vol% of CaO–P2O5–SiO2 (CaPSi) glass (AY-TZP5) and 10.5 vol% CaPSi glass (AY-TZP10), with ammonium polyacrylate (NH4PA) dispersant were prepared to produce slip cast compacts. The rheological properties of 35 and 40 vol% slips were studied. The densification, microstructure as well as hardness and fracture toughness were investigated as a function of CaPSi glass content at 1300°C-1500°C. The optimum NH4PA concentration of 35 vol% AY-TZP5 and AY-TZP10 slips at pH ~9 was found to be about 43% and 67% greater than that of AY-TZP slips; this behavior was related to the greater amounts of Ca2+ ions leached out from the CaPSi glass surface. The viscosity of stabilized 40 vol% slips with NH4PA attained a minimum value at 5.4 vol% CaPSi glass addition, and resulted in a more dense packing of cast samples. AY-TZP5 can be sintered at a lower temperature (1300°C) compared to that of AY-TZP. AY-TZP5 exhibited a fine microstructure of tetragonal ZrO2 (grain sizes below 0.3 µm), and ZrSiO4–Ca2P2O7 particles homogeneously distributed within the zirconia matrix. It presented similar fracture toughness and a slightly lower hardness compared to those of AY-TZP. 相似文献
992.
The porosity dependence of Poisson's ratio of materials with random microstructure is investigated via analytical and numerical modeling. It is shown that all analytical models predict porosity independence if the solid Poisson ratio is 0.2 and for low porosities a converging trend toward this value with increasing porosity. From all theory-based relations, only power-law and exponential relations allow for auxetic behavior. Numerical calculations on computer-generated digital microstructures (overlapping and isolated spherical pores, pores between overlapping spherical grains, wall-based cellular materials/closed-cell foams, and strut-based cellular materials/open-cell foams) confirm the general qualitative trends of the analytical models, although a closer look reveals significant quantitative differences. Cellular materials and foams exhibit similar features as porous materials in general, but lack their converging trend toward values around 0.2. Comparison of our results with the classical Roberts-Garboczi results shows good agreement, with subtle differences due to the different microstructures generated. 相似文献
993.
Gabino A. Carriedo Francisco J. García Alonso Alejandro Presa Soto 《Journal of Inorganic and Organometallic Polymers and Materials》2007,17(2):399-406
The chiral phosphazene copolymers {[NP(O2C12H8)]0.9[NP(O2C20H12)]0.1} (1) and {[NP(O2C12H8)]0.9[NP(O2C20H10Br2)]0.1}
n
(2) [(O2C12H8) = 2,2′-dioxy-1,1′-biphenyl; (O2C20H12) = R-2,2′-dioxy-1,1′-binaphthyl and (O2C20H10Br2) = R-6,6′-dibromo-2,2′-dioxy-1,1′-binaphthyl] were prepared by sequential substitution from [NPCl2]
n
and the corresponding dihydroxy-biphenyl or binaphthyl reagents in the presence of Cs2CO3 and K2CO3. The reaction of (2) with tBuLi in THF, followed by addition of PPh2Cl and a treatment with SiHCl3/PPh3 to eliminate any oxidized OC6H4P(O)Ph2 groups, gave the phosphine containing copolymer {[NP(O2C12H8)]0.9[NP(O2C20H10[PPh2]2)]0.1}
n
(3), that was used as a chiral ligand to support [Ru(p-cymene)Cl] complexes. The resulting catalyst was active for hydrogen
transfer from isopropyl alcohol to acetophenone but the placement of the Ru centers in the 6,6′-positions of the binaphthoxyphosphazene
units induced no enantioselectivity.
Dedicated to Professor Christopher Allen. 相似文献
994.
Costa Rica is not an exception in the prevalence of ochratoxin A in human plasma, in this research the presence of the micotoxin was found in 95% of the 149 samples studied. The presence of ocratoxina A also was studied in 110 samples of toasted and grounded coffee from the most important 12 coffee factories of the country and from 7 supermarkets. With the exception of one negative sample the rest of them have concentrations of micotoxin below 4000 ng/kg. An association between the coffee consumption and the presence of ochratoxin A in plasma was attempted to be found as well as in the consumption of beer, but there were any statistically significant difference in the average level of mycotoxin between the coffee consumers and non coffee consumers neither between beer consumers and no beer consumers. 相似文献
995.
Extrusion flow experiments of linear and branched syndiotactic poly(propylene)s were carried out. The work was focused on flow instabilities. Ionized radiation was employed to induce long chain branching in linear samples. Sharkskin and melt fracture were postponed in the case of slightly long branched samples, which possess an enhanced melt elasticity compared to linear samples. For the most elastic samples the nature of the flow instability changed: sharkskin disappeared and melt fracture was observed instead. The correlation between sharkskin and melt strength results is discussed.
996.
Summary The dependence of viscosity of cellulose tricarbanilate in tetrahydrofuran on the velocity gradient D <2500 s–1 for molecular weights up to 1.2×106 was determined, and an empirical equation for the determination of the limiting viscosity number for zero velocity gradient was derived. Errors involved in the viscosity determination from a single concentration using an approximate formula were also ascertained. 相似文献
997.
K. Matias̆ovský P. Fellner M. Chrenková-Pauc̆írová G. Bräutigam H.-H. Emons 《Electrochimica acta》1980,25(2):195-200
The density and specific electrical conductivity were investigated for molten ternary NaCl-KCl-AlCl3 mixtures of interest to new industrial processes for electrolytic aluminium deposition. A method for the calculation of density and electrical conductivity of molten ternary mixtures on the basis of experimentally determined values for the binary systems NaCl-AlCl3, NaCl-KCl and KCl-AlCl3 has been proposed. The difference between the experimental and calculated density and electrical conductivity values of the ternary system was less than ± 1.5% for the density and ± 5% for the electrical conductivity, respectively. 相似文献
998.
999.
Mechanical properties and thermal shock in thin ZrO2–Y2O3–Al2O3 films obtained by the sol-gel method
Antonio Díaz-Parralejo M. Ángeles Díaz-Díez José Sánchez-González Antonio Macías-García Juan Pablo Carrasco-Amador 《Ceramics International》2021,47(1):80-86
Thin multilayer coatings of ZrO2–Y2O3–Al2O3 were prepared using the sol-gel method and dip-coating technique in order to advance in the study of what influence the incorporation of Al2O3 has on films of Y2O3-doped ZrO2, investigating its role in the synthesis of the solutions and in the characteristics and properties of the coatings. After the characterization of the solutions used in the process, the microstructure of the films was studied and their mechanical behaviour and resistance to thermal shock were determined so as to optimize the characteristics and functionality of these coatings. With increased alumina content, 3YSZ-Al2O3 (20 mol%), the cubic phase of the zirconia disappeared completely at the sintering temperature used (700 °C), resulting in the tetragonal phase with Al in solution. There was also a decrease in the coatings' hardness and Young's modulus, and an increase in toughness and resistance to thermal shock. These results allow guidelines to be established for the design of multilayer structures that are, tougher, more resistant, and have improved surface properties. 相似文献
1000.