全文获取类型
收费全文 | 1834篇 |
免费 | 214篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 27篇 |
综合类 | 1篇 |
化学工业 | 415篇 |
金属工艺 | 66篇 |
机械仪表 | 157篇 |
建筑科学 | 28篇 |
能源动力 | 98篇 |
轻工业 | 125篇 |
水利工程 | 2篇 |
石油天然气 | 2篇 |
无线电 | 396篇 |
一般工业技术 | 454篇 |
冶金工业 | 76篇 |
原子能技术 | 27篇 |
自动化技术 | 176篇 |
出版年
2024年 | 1篇 |
2023年 | 20篇 |
2022年 | 26篇 |
2021年 | 67篇 |
2020年 | 32篇 |
2019年 | 78篇 |
2018年 | 59篇 |
2017年 | 81篇 |
2016年 | 106篇 |
2015年 | 78篇 |
2014年 | 94篇 |
2013年 | 110篇 |
2012年 | 158篇 |
2011年 | 186篇 |
2010年 | 122篇 |
2009年 | 120篇 |
2008年 | 108篇 |
2007年 | 86篇 |
2006年 | 66篇 |
2005年 | 55篇 |
2004年 | 60篇 |
2003年 | 58篇 |
2002年 | 53篇 |
2001年 | 38篇 |
2000年 | 39篇 |
1999年 | 26篇 |
1998年 | 20篇 |
1997年 | 20篇 |
1996年 | 15篇 |
1995年 | 18篇 |
1994年 | 7篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 5篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有2050条查询结果,搜索用时 11 毫秒
51.
Woon Jin Chung Bong Je Park Hong Seok Seo Joon Tae Ahn Myung-Hyun Lee Yong Gyu Choi 《Journal of the American Ceramic Society》2005,88(5):1205-1208
Selenide glass optical fibers were fabricated for Ge30 Sb10 Se58 S2 and Ge20 Sb10 Se70 glasses. Their transmission loss has been measured and compared with the theoretical attenuation loss that was calculated taking into account the electronic transition absorption, Rayleigh scattering, and multiphonon absorption. A low attenuation loss of the Ge20 Sb10 Se70 glass composition in 1.2–1.7 μm range has been expected due to its high optical band gap energy compared with the Ge30 Sb10 Se58 S2 glass. However, the measured attenuation loss of the Ge30 Sb10 Se58 S2 glass fiber was ∼13 dB/m at 1.5 μm while Ge20 Sb10 Se70 glass showed ∼82 dB/m. An enhanced weak absorption tail due to the localized states of the Ge20 Sb10 Se70 glass was responsible for this behavior. Structural defects are related to the localized states and discussed for the present glass compositions. 相似文献
52.
Jung Joon Lee Heeyeon Kim Jae Hyun Koh Ara Jo Sang Heup Moon 《Applied catalysis. B, Environmental》2005,61(3-4):274-280
The performance of a new type of CoMoS/Al2O3 catalyst, with added fluorine and prepared by sonochemical and chemical vapor deposition (CVD) methods, was investigated in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). The catalyst, which was designed to contain optimum amounts of fluorine and cobalt, exhibited a higher activity, ca. 4.6 times higher activity particularly in the HDS of 4,6-DMDBT, than a fluorine-free catalyst prepared by a conventional impregnation method. The enhanced activity of the new catalyst can be attributed to the cumulative effects of individual factors involved in the catalyst preparation. That is, the use of a sonochemical synthesis led to a high dispersion of small MoS2 crystallites on the alumina, and the addition of the Co species to the catalyst by CVD caused a close interaction between the Co species and the MoS2 crystallites to produce numerous CoMoS species, which are the catalytically active species for HDS. The addition of fluorine increased the amounts of acidic sites in the catalyst, which promoted hydrogenation (HYD) route to a greater extent than the direct desulfurization (DDS) route in DBT HDS and both HYD and DDS routes to similar extents in the case of 4,6-DMDBT HDS. Accordingly, the addition of fluorine led to a greater increase in catalytic activity for 4,6-DMDBT HDS than for DBT HDS. 相似文献
53.
Jin Woo Bae Tae Uk Yang Gi Joon Nam Gun Joo Lee Byeong-Uk Nam Jae Young Jho 《Polymer Bulletin》2011,67(4):729-740
Ethylene vinylacetate (EVA) copolymer-based nanocomposites with maleic anhydride-grafted ethylene-vinylacetate (EVAgMA) and
organically modified clay (o-clay) were prepared in a twin screw extruder by following a two-step melt compounding method.
EVAgMA/o-clay masterbatches with various clay contents up to 50 wt% were examined, after which the masterbatch with the highest
clay content was melt compounded with EVA for the preparation of EVA/o-clay nanocomposites containing specific amounts of
clay. Further morphological dispersion of the clay particles by highly polar EVA and shearing was confirmed in the EVA/o-clay
nanocomposites by X-ray diffraction (XRD) and transmission electron microscopy (TEM). These morphologies led to increased
thermal properties in air as well as a considerable decrease in heat release rate (HRR). EVA/o-clay/MDH nanocomposites were
also prepared using a high clay-bearing masterbatch to confirm the synergistic flame retardancy of clay as a co-additive in
EVA/MDH composites. EVA/o-clay/MDH nanocomposites prepared by substituting o-clay for MDH showed significantly lower and wider
HRR during combustion compared to EVA/MDH composite. 相似文献
54.
A method is presented for significantly reducing the interfacial contact resistance of single-walled carbon nanotube (SWCNT) interconnects test-structures. Conventional lithographic cleaning steps are insufficient for complete removal of lithographic residues in SWCNT networks, leading to large interfacial contact resistance. Using improved purification procedures and controlled developing time, the interfacial contact resistance between SWCNTs and contact electrodes of Ti/Au were found to reach values below 2% of the overall resistance in two-probe test-structures of SWCNTs, demonstrating the importance of cleaning lithographic residues from the surface of SWCNTs before the fabrication of metal electrodes. These low-resistance contacts are quite stable over a large temperature range, and represent a step towards the implementation of SWCNTs as future interconnects. 相似文献
55.
Due to the numerous applications of nanofluids, investigating and understanding of thermophysical properties of nanofluids
has currently become one of the core issues. Although numerous theoretical and numerical models have been developed by previous
researchers to understand the mechanism of enhanced heat transfer in nanofluids; to the best of our knowledge these models
were limited to the study of either thermal conductivity or convective heat transfer of nanofluids. We have developed a numerical
model which can estimate the enhancement in both the thermal conductivity and convective heat transfer in nanofluids. It also
aids in understanding the mechanism of heat transfer enhancement. The study reveals that the nanoparticle dispersion in fluid
medium and nanoparticle heat transport phenomenon are equally important in enhancement of thermal conductivity. However, the
enhancement in convective heat transfer was caused mainly due to the nanoparticle heat transport mechanism. Ability of this
model to be able to understand the mechanism of convective heat transfer enhancement distinguishes the model from rest of
the available numerical models. 相似文献
56.
Joon‐Seop Kim Min‐Chul Hong Yeon Hwa Nah Yeonhee Lee Seunghee Han Hyun Eui Lim 《应用聚合物科学杂志》2002,83(11):2500-2504
The wetting properties of polystyrene‐based ionomers treated with plasma source ion implantation (PSII) were investigated by the measurement of water contact angles. When sulfonated ionomers were aged for a few days, the hydrophobic recovery for the ionomers became much slower than that for the nonionic polymers. However, when the samples were aged over 20 days, the water contact angle of the ionomers converged with that of the nonionic polymer. Thus, it was concluded that the ionic interaction between the ionic groups and the presence of ionic groups together resulted in the slow hydrophobic recovery and that the aging effect was significant for the ionomers. For the methacrylate ionomer of low ion content, on the other hand, it was found that the PSII treatment produced only a small change in hydrophobic recovery behavior. Thus, it was suggested that the low ionic content coupled with the small size of the ionic unit might cause changes only of a very insignificant degree in hydrophobic recovery behavior. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2500–2504, 2002 相似文献
57.
Polyurethane acrylate anionomer (PUAA)/silica composite gels were prepared by the sol‐gel reaction of tetraethoxysilane (TEOS) and methacryloxypropyl trimethoxysilane (MPTS) incorporated to PUAA gels by using a swelling method. The formation and structure of composites were confirmed by FTIR, X‐ray diffraction, and SEM. As a result, we found that silica components in composites are located within the ionic domains of their gels and interacted with PUAA via hydrogen bonding. This drastically enhanced the mechanical properties of the composites. Mechanical properties are also improved by MPTS, because MPTS improves the dispersibility and adhesion of silica components in PUAA/silica composite gels. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2327–2334, 2002 相似文献
58.
Won Seok Lyoo Han Do Ghim Hee‐Sam Kim Joon Ho Kim Sam Soo Kim Won Sik Yoon Jinwon Lee Sang‐Seob Lee 《应用聚合物科学杂志》2002,86(14):3667-3672
N‐Vinylcarbazole (VCZ) was solution‐polymerized in tetrahydrofuran (THF) at ?20, 0, and 20°C using the photoinitiation method; the effects of the amount of solvent, polymerization temperature, and photoinitiator concentration were investigated. On the whole, the experimental results corresponded to predicted ones. Low polymerization temperature using photoinitiation proved to be successful in obtaining poly(N‐vinylcarbazole) (PVCZ) of a high molecular weight with a smaller temperature rise during polymerization; nevertheless of free radical polymerization by 2,2′‐azobis(2,4‐dimethylvaleronitrile) (ADMVN). The photo‐solution polymerization rate of VCZ in THF was proportional to the 0.47 power of ADMVN concentration. The molecular weight was higher and the molecular weight distribution was narrower with PVCZ polymerized at lower temperatures. For PVCZ prepared in THF at ?20°C using a photoinitiator concentration of 0.00005 mol/mol of VCZ, a weight‐average molecular weight of 510,000 was obtained, with a polydispersity index of 1.73, and a degree of lightness converged to about 99%. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3667–3672, 2002 相似文献
59.
Young Joon Lee Takashi Miyahara Tatsuya Noike 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2002,77(6):694-698
The influence of initial pH of the culture medium on hydrogen production was studied using sucrose solution and a mixed microbial flora from a soybean‐meal silo. Hydrogen production was not observed at pH values of 3.0, 11.0 and 12.0 but low production was observed at pH values 5.0 and 5.5. The pH of the experimental mixture decreased rapidly and produced hydrogen gas within 30 h. Methane was not detected at initial pH values between 6.0 and 10.0. The sucrose degradation efficiency increased as the initial pH value increased from 3.0 to 9.0. The maximum sucrose degradation efficiency of 95% was observed at pH 9.0. The maximum specific production yields of hydrogen, VFAs and alcohols were 126.9 cm3 g?1 sucrose (pH of 9.0), 0.7 gCOD g?1 sucrose (pH of 8.0) and 128.7 mgCOD g?1 sucrose (pH of 9.0), respectively. The relationship between the hydrogen ion concentration and the specific hydrogen production rate has been mathematically described. The best kinetic parameters on the specific hydrogen production rate were KOH = 1.0 × 10?7 mol dm?3 and KH = 1.1 × 10?4 mol dm?3 (r2 = 0.86). The maximum specific hydrogen production rate was 37.0 cm3 g?1 VSS h?1. © 2002 Society of Chemical Industry 相似文献
60.
Measurements of non-methane hydrocarbons (NMHC) were performed at the entrance and exit of the Sangdo tunnel to estimate emission
factors (EF) of NMHC from vehicles in May 2000. About 50 species were analyzed by a combined GC/FID and GC/MS system. Ethylene
was the most abundant compound, followed by n-butane and acetylene, respectively. Based on the measurement data, the real
world vehicular EF in Seoul was estimated. The highest EF value was 89.8 mg (veh-mile)-1 for n-butane, followed by ethylene and toluene. 相似文献