全文获取类型
收费全文 | 1555篇 |
免费 | 31篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 70篇 |
综合类 | 7篇 |
化学工业 | 383篇 |
金属工艺 | 30篇 |
机械仪表 | 33篇 |
建筑科学 | 28篇 |
能源动力 | 40篇 |
轻工业 | 157篇 |
水利工程 | 10篇 |
石油天然气 | 2篇 |
无线电 | 154篇 |
一般工业技术 | 321篇 |
冶金工业 | 214篇 |
原子能技术 | 55篇 |
自动化技术 | 95篇 |
出版年
2023年 | 5篇 |
2022年 | 9篇 |
2021年 | 21篇 |
2020年 | 14篇 |
2019年 | 16篇 |
2018年 | 21篇 |
2017年 | 17篇 |
2016年 | 27篇 |
2015年 | 26篇 |
2014年 | 36篇 |
2013年 | 72篇 |
2012年 | 62篇 |
2011年 | 74篇 |
2010年 | 60篇 |
2009年 | 66篇 |
2008年 | 93篇 |
2007年 | 72篇 |
2006年 | 60篇 |
2005年 | 47篇 |
2004年 | 43篇 |
2003年 | 50篇 |
2002年 | 41篇 |
2001年 | 50篇 |
2000年 | 31篇 |
1999年 | 29篇 |
1998年 | 95篇 |
1997年 | 66篇 |
1996年 | 48篇 |
1995年 | 35篇 |
1994年 | 33篇 |
1993年 | 32篇 |
1992年 | 25篇 |
1991年 | 23篇 |
1990年 | 19篇 |
1989年 | 14篇 |
1988年 | 12篇 |
1987年 | 14篇 |
1986年 | 15篇 |
1985年 | 13篇 |
1984年 | 19篇 |
1983年 | 10篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 16篇 |
1979年 | 12篇 |
1978年 | 4篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1969年 | 3篇 |
排序方式: 共有1599条查询结果,搜索用时 282 毫秒
11.
New integrated optical devices combining an InGaAsP/InP HPT and an inner-stripe LED are proposed and their fabrication processes are described. The device functions of light amplification, optical bistability, and optical switching are demonstrated in the 1-μm wavelength region. 相似文献
12.
Planned Leadtimes For Serial Production Systems 总被引:1,自引:0,他引:1
Candace Arai Yano 《IIE Transactions》1987,19(3):300-307
We investigate the problem of setting planned leadtimes in serial production systems when the actual leadtimes are stochastic. The objective is to minimize the sum of inventory holding costs, rescheduling costs arising from tardiness at intermediate stages of production, and tardiness of delivery to the customer.
A single-pass algorithm is developed which finds optimal solutions. The analytical models underlying the algorithm and extensive computational experience indicate that it is never optimal to have planned leadtimes of zero when there are rescheduling costs at intermediate stages of production. This also implies that unconditional immediate dispatching is not optimal under these conditions. 相似文献
A single-pass algorithm is developed which finds optimal solutions. The analytical models underlying the algorithm and extensive computational experience indicate that it is never optimal to have planned leadtimes of zero when there are rescheduling costs at intermediate stages of production. This also implies that unconditional immediate dispatching is not optimal under these conditions. 相似文献
13.
We developed a multichannel fiber ferrule for a stable laser-diode array module. To apply YAG laser welding to parallel butt couple between the laser-diode and the single-mode fiber arrays, hermetically sealed and precisely aligned equi-interval fibers are required. We describe a V-grooved ceramic ferrule for embedding fibers. Fibers are fixed by soldering, using a flat ceramic lid and aligned with a 250 μm pitch. Our ferrule allowed a metallic, stem mounting laser-diode, to be fixed by YAG laser welding. All 30 samples tested have a leak rate of less than 1×10-10 atm·cc/s. Optical coupling of fabricated modules was 9.7±0.2 dB and coupling loss change from 25°C to 115°C was within 0.5 dB 相似文献
14.
15.
Akihisa Inoue Nobuyoshi Yano Kunio Matsuzaki Tsuyoshi Masumoto 《Journal of Materials Science》1987,22(5):1827-1834
Copper-based superconducting alloys including finely dispersed f c c lead or h c p (Pb- Bi) particles in f c c copper matrix have been obtained by rapid quenching (Cu-M)100-x
Pbx and (Cu-M)100-x
(Pb0.6Bi0.4
x
(M = aluminium, silicon or tin;x < 10 at%) alloys containing immiscible elements such as lead and bismuth. The particle size and interparticle distance were about 30 to 130 nm and 20 to 200 nm for had particles and about 30 to 60 nm and 30 to 150 nm for (Pb- Bi) particles. The transition temperature,T
c, was in the range of 3.2 to 5.5 K for the Cu-M-Pb alloys and 6.2 to 6.3 K for the Cu-M-Pb-Bi alloys. Critical magnetic field,H
c2, and critical current density,J
c, for the later alloys were 0.47 to 0.93T at 4.2 K and 1.1 × 105 to 2.7 × 105 Am–2 at zero applied field and 4.21 K. The mechanism of the appearance of such a soft-type superconductivity for the rapidly quenched copper-based alloys was discussed, and inferred to be due to the formation of a percolation path of a superconducting lead or Pb-Bi phase along the grain boundaries, sub-boundaries and/or tangled dislocations where the lead or Pb-Bi phase precipitated preferentially, rather than the proximity effect based on lead or Pb-Bi particles. 相似文献
16.
17.
Masaaki Suzuki Yoshihisa Hasegawa Masayuki Aizawa Yoshinori Nakata Takeshi Okutani Kohei Uosaki 《Journal of the American Ceramic Society》1995,78(1):83-89
The structure of silicon carbide–silicon nitride (SiC–Si3 N4 ) composite particles synthesized using a CO2 laser was studied by magic angle spinning nuclear magnetic resonance (MAS-NMR) and electron spin resonance (ESR). The structure around Si atoms changed by introducing N. C atoms around Si were substituted by N atoms, and N-rich configurations around Si atoms increased stepwise as the N content increased. The low N content composite particles consisted of mainly SiC phase containing dissolved N. N atoms were partly present in β-SiC microcrystal and partly in the grain boundary layer in the particle. N atoms were tetrahedrally surrounded by four Si atoms in β-SiC microcrystal and were trivalent state bonded to three Si atoms in the grain boundary layer. The high N content particles consisted of SiC, Si3 N4 , and amorphous phases, whose amount depended on N content. 相似文献
18.
Atsushi Takahashi Isao Nakamura Masaaki Haneda Tadahiro Fujitani Hideaki Hamada 《Catalysis Letters》2006,106(3-4):133-138
Catalytic hydrogenation of naphthalene to decalin was studied over a carbon-supported rhodium catalyst in supercritical carbon
dioxide solvent at 333 K, and the results were compared with those in an organic solvent. cis-, trans-Decalin and tetralin were formed from the beginning of the reaction in supercritical carbon dioxide. Higher concentration
of hydrogen in carbon dioxide solvent and on the active site, and also the suppression of desorption of partially hydrogenated
tetralin molecules from the active site would be responsible for higher selectivity to cis-decalin in supercritical carbon dioxide than that in an organic solvent. 相似文献
19.
Hideto Matsuyama Kentarou Hayashi Taisuke Maki Masaaki Teramoto Noboru Kubota 《应用聚合物科学杂志》2004,93(1):471-474
Microporous high‐density polyethylene (HDPE) and low‐density polyethylene (LDPE) hollow fiber membranes were prepared from polyethylene–diisodecyl phthalate solution via thermally induced phase separation. Effect of the polyethylene density on the membrane structure and performance was investigated. The HDPE membrane showed about five times higher water permeability than the LDPE membrane because it had the larger pore and the higher porosity at the outer membrane surface. The formation of the larger pore was owing to both the initial larger structure formed by spinodal decomposition and the suppression of the diluent evaporation from the outer membrane surface due to the higher solution viscosity. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 471–474, 2004 相似文献
20.
Phase separation rate during porous membrane formation by immersion precipitation was investigated by light scattering in a polyimide/N‐Methylpyrrolidone (NMP)/water system. In the light scattering measurement, plots of scattered intensity against scattered angle showed maxima in all cases, which indicated that phase separation occurred by a spinodal decomposition (SD). Characteristic properties of the early stage of SD, such as an apparent diffusion coefficient Dapp and an interphase periodic distance Λ, were obtained. The growth process of Λ was also followed by light scattering. The growth rate had the same tendency as Dapp when water content in the nonsolvent bath and the polymer concentration in the cast solution were changed. The pore size of the final membrane increased with decreasing water content, which was opposite to the tendency of Λ growth rate. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 292–296, 2003 相似文献