全文获取类型
收费全文 | 2034篇 |
免费 | 39篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 91篇 |
综合类 | 6篇 |
化学工业 | 486篇 |
金属工艺 | 56篇 |
机械仪表 | 60篇 |
建筑科学 | 36篇 |
矿业工程 | 1篇 |
能源动力 | 86篇 |
轻工业 | 186篇 |
水利工程 | 2篇 |
无线电 | 142篇 |
一般工业技术 | 309篇 |
冶金工业 | 383篇 |
原子能技术 | 97篇 |
自动化技术 | 140篇 |
出版年
2023年 | 11篇 |
2022年 | 7篇 |
2021年 | 23篇 |
2020年 | 6篇 |
2019年 | 20篇 |
2018年 | 31篇 |
2017年 | 23篇 |
2016年 | 35篇 |
2015年 | 23篇 |
2014年 | 34篇 |
2013年 | 99篇 |
2012年 | 70篇 |
2011年 | 108篇 |
2010年 | 64篇 |
2009年 | 75篇 |
2008年 | 88篇 |
2007年 | 67篇 |
2006年 | 77篇 |
2005年 | 77篇 |
2004年 | 65篇 |
2003年 | 72篇 |
2002年 | 60篇 |
2001年 | 40篇 |
2000年 | 39篇 |
1999年 | 58篇 |
1998年 | 134篇 |
1997年 | 89篇 |
1996年 | 66篇 |
1995年 | 46篇 |
1994年 | 46篇 |
1993年 | 41篇 |
1992年 | 22篇 |
1991年 | 31篇 |
1990年 | 16篇 |
1989年 | 19篇 |
1988年 | 17篇 |
1987年 | 24篇 |
1986年 | 30篇 |
1985年 | 22篇 |
1984年 | 23篇 |
1983年 | 19篇 |
1982年 | 16篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 28篇 |
1978年 | 18篇 |
1977年 | 20篇 |
1976年 | 23篇 |
1974年 | 6篇 |
1972年 | 7篇 |
排序方式: 共有2081条查询结果,搜索用时 562 毫秒
101.
Zhen-Yan Deng Yoshiaki Inagaki Jihong She Yoshihisa Tanaka Yu-Fu Liu Masao Sakamoto Tatsuki Ohji 《Journal of the American Ceramic Society》2005,88(2):462-465
Long crack R -curve of a porous Si3 N4 with aligned fibrous grains was investigated, using a chevron-notched beam technique. A crack was constrained to propagate normal to the grain alignment. The crack growth resistance of aligned porous Si3 N4 was much larger compared with that of dense Si3 N4 ceramics. Microstructure observations showed that pullouts of fibrous grains in aligned porous Si3 N4 markedly increased during crack propagation relative to those of dense Si3 N4 , due to the existence of pores. The efficient grain pullouts in porous Si3 N4 increased the bridging stress at the crack wake. 相似文献
102.
The elastic and yield properties of drawn poly(methyl methacrylate) (PMMA) filled with ultrafine SiO2 are described as functions of filler content and size. The drawn PMMA composites were made by uniaxially drawing to x4.0 at 100°C and at a rate of 20 mm/min. Four compliance values, i.e., S33, S11, S13, and S44 were determined. These values decreased with filler content and decreasing filler size. The relative compliance values Sde/Sdo(Sde is the compliance of drawn PMMA composites and Sdo is that of drawn unfilled PMMA) are almost equivalently changed with changes in filler content. The elastic properties of drawn PMMA composites are thus reinforced isotopically. This is characteristic of PMMA which has a large side group. The yield behavior of drawn PMMA composites have similar filler size and content dependence to those of elastic properties except that the transverse yield stresses become more brittle with filler content. The anisotropy in yield stress is relatively larger than that of elastic properties. This is probably because the anti-reiforcing effect, such as fibrillation becomes prominent with increasing filler content in the perpendicular direction. 相似文献
103.
Tomotake Morita Emi Ito Hiroko K. Kitamoto Kaoru Takegawa Tokuma Fukuoka Tomohiro Imura Dai Kitamoto 《Yeast (Chichester, England)》2010,27(11):905-917
The yeast Pseudozyma antarctica produces a large amount of glycolipid biosurfactants known as mannosylerythritol lipids (MELs), which show not only excellent surface‐active properties but also versatile biochemical actions. To investigate the biosynthesis of MELs in the yeast, we recently reported expressed sequence tag (EST) analysis and estimated genes expressing under MEL production conditions. Among the genes, a contiguous sequence of 938 bp, PA_004, showed high sequence identity to the gene emt1, encoding an erythritol/mannose transferase of Ustilago maydis, which is essential for MEL biosynthesis. The predicted translation product of the extended PA_004 containing the two introns and a stop codon was aligned with Emt1 of U. maydis. The predicted amino acid sequence shared high identity (72%) with Emt1 of U. maydis, although the amino‐terminal was incomplete. To identify the gene as PaEMT1 encoding an erythritol/mannose transferase of P. antarctica, the gene‐disrupted strain was developed by the method for targeted gene disruption, using hygromycin B resistance as the selection marker. The obtained ΔPaEMT1 strain failed to produce MELs, while its growth was the same as that of the parental strain. The additional mannosylerythritol into culture allowed ΔPaEMT1 strain to form MELs regardless of the carbon source supplied, indicating a defect of the erythritol/mannose transferase activity. Furthermore, we found that MEL formation is associated with the morphology and low‐temperature tolerance of the yeast. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
104.
Toshiki Tsubota Masaki Morita Sunao Kamimura Teruhisa Ohno 《Journal of Porous Materials》2016,23(2):349-355
Unconventional pretreatment, that is, delignification and the addition of guanidine phosphate, was performed for the synthesis of activated carbon having a high specific surface area from bamboo by physical activation. The values of the specific surface area, total pore volume, and average pore size depended on the amount of added guanidine phosphate and the CO2 activation time. The amount of the added guanidine phosphate under the optimum conditions for the highest specific surface area was much lower than that of the phosphorous acid chemical activator under conventional conditions. The N2 adsorption isotherms of all the samples were type I, which means that micropores were dominant. The pore sizes of the samples in this study were similar to that of the physically-activated carbon. Therefore, the activation process was presumed to be essentially not chemical, but physical. The relation between the yield and the specific surface area improved with the addition of guanidine phosphate. The reason for the improvement may be the change in the reactivity of the carbon material generated during the heating process. The maximum specific surface area was ca. 2000 m2 g?1, which is a high value for a physically-activated carbon. 相似文献
105.
N‐Phenylmaleimide–N‐(p‐hydroxy)phenylmaleimide–styrene terpolymer (HPMS), carrying reactive p‐hydroxyphenyl groups, was prepared and used to improve the toughness of cyanate ester resins. Hybrid modifiers composed of N‐phenylmaleimide–styrene copolymer (PMS) and HPMS were also examined for further improvement in toughness. Balanced properties of the modified resins were obtained by using the hybrid modifiers. The morphology of the modified resins depends on HPMS structure, molecular weight and content, and hybrid modifier compositions. The most effective modification of the cyanate ester resin was attained because of the co‐continuous phase structure of the modified resin. Inclusion of the modifier composed of 10 wt% PMS (Mw 136 000 g mol?1) and 2.5 wt% HPMS (hydroxyphenyl unit 3 mol%, Mw 15 500 g mol?1) led to 135% increase in the fracture toughness (KIC) for the modified resin with a slight loss of flexural strength and retention of flexural modulus and glass transition temperature, compared with the values for the unmodified resin. Furthermore, the effect of the curing conditions on the mechanical and thermal properties of the modified resins was examined. The toughening mechanism is discussed in terms of the morphological and dynamic viscoelastic behaviour of the modified cyanate ester resin system. © 2001 Society of Chemical Industry 相似文献
106.
107.
Ill Yong Kim Ryota Iwatsuki Koichi Kikuta Yumi Morita Toshiki Miyazaki Chikara Ohtsuki 《Materials science & engineering. C, Materials for biological applications》2011,31(7):1472-1476
Osteoconductive materials with self-setting ability have received much attention because their properties allow developing injectable materials for bone defects. Thermosensitive hydrogel with ability of bone-like apatite formation in a body environment is a candidate of injectable bone fillers with osteoconductivity because the apatite formation on materials is an essential to show osteoconduction. The present study focused on the development of a thermosensitive hydrogel through modifications of the sulphonic groups of the polysaccharide, κ-carrageenan, with potassium chloride (KCl) and calcium chloride (CaCl2). We found that the gelation temperature of κ-carrageenan solutions increased with increasing amounts of K+ ions. Apatite formation was observed on the gel after exposure to simulated body fluid for 0.5 day when the gel was prepared with a molar ratio of Ca2+/sulfonic groups = 1.5. These results indicate that a thermosensitive κ-carrageenan hydrogel with apatite-forming ability was obtained through the incorporation of K+ and Ca2+ ions into the solution. 相似文献
108.
Satoshi Akamaru Masanori Hara Norio Nunomura Masao Matsuyama 《International Journal of Hydrogen Energy》2013
The magnetic susceptibility and the pressure-composition isotherm were measured simultaneously for Pd–Rh–H and Pd–Ag–H systems in order to clarify the effect of Rh or Ag substitution on the hydrogen uptake from viewpoint of the electronic band structure. The magnetic susceptibility of all Pd binary alloys prepared decreased monotonically with increasing hydrogen content. At high hydrogen contents, the magnetic susceptibility became approximately zero for Pd–Rh–H and Pd–Ag–H system, and the hydrogen content at which the magnetic susceptibility gives zero corresponded with the terminal of the plateau region in the isotherm curve. The results indicated that the magnetic susceptibility of hydride phase was almost zero for all Pd binary alloys. On the basis of the band structure of Pd metal, we concluded that atom substitution only affected shift of the energy at Fermi level, and the amount of the hydrogen uptake was dominated by the number of unoccupied d-band in the alloys. 相似文献
109.
Masao Doi Katsunori Takahashi Takashi Yonemoto Tatsuya Yamaue 《Reactive and Functional Polymers》2013,73(7):891-893
An ionic-polymer–metal-composite film shows electro-mechanical coupling. When the film is bent, electric current is induced. Measurement of the induced current indicates that the current depends on the speed of bending, but the total amount of the charge transferred across the film is independent of the speed, and depends only on the magnitude of the bending. The result indicates that in addition to previously proposed dynamical coupling effect, there is a static electro-mechanical coupling effect. Mathematical model is proposed to describe this phenomena. 相似文献
110.
Shin-ichi Morita Yasutaka Hayamizu Akihiko Horibe Naoto Haruki Hideo Inaba 《热科学学报(英文版)》2013,22(2):145-151
Recently, much attention has been paid to investigate the latent heat storage system. Using of ice heat storage system brings an equalization of electric power demand, because it will solved the electric -power-demand-concentration on day-time of summer by the air conditioning. The flowable latent heat storage material, Oil/Water type emulsion, microencapsulated latent heat material-water mixture or ice slurry, etc., is enable to transport the latent heat in a pipe. The flowable latent heat storage material can realize the pipe size reduction and system efficiency improvement. Supercooling phenomenon of the dispersed latent heat storage material in continuous phase brings the obstruction of latent heat storage. The latent heat storage rates of dispersed water drops in W/O (Water/Oil) emulsion are investigated experimentally in this study. The water drops in emulsion has the diameter within 3 ~ 25μm, the averaged water drop diameter is 7.3μm and the standard deviation is 2.9μm. The direct contact heat exchange method is chosen as the phase change rate evaluation of water drops in W/O emulsion. The supercooled temperature and the cooling rate are set as parameters of this study. The evaluation is performed by comparison between the results of this study and the past research. The obtained experimental result is shown that the 35K or more degree from melting point brings 100% latent heat storage rate of W/O emulsion. It was clarified that the supercooling rate of dispersed water particles in emulsion shows the larger value than that of the bulk water. 相似文献