全文获取类型
收费全文 | 2773篇 |
免费 | 57篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 132篇 |
综合类 | 8篇 |
化学工业 | 667篇 |
金属工艺 | 88篇 |
机械仪表 | 45篇 |
建筑科学 | 32篇 |
能源动力 | 97篇 |
轻工业 | 227篇 |
水利工程 | 9篇 |
石油天然气 | 5篇 |
无线电 | 245篇 |
一般工业技术 | 560篇 |
冶金工业 | 496篇 |
原子能技术 | 80篇 |
自动化技术 | 147篇 |
出版年
2023年 | 11篇 |
2022年 | 27篇 |
2021年 | 35篇 |
2020年 | 21篇 |
2019年 | 20篇 |
2018年 | 29篇 |
2017年 | 29篇 |
2016年 | 39篇 |
2015年 | 31篇 |
2014年 | 50篇 |
2013年 | 117篇 |
2012年 | 64篇 |
2011年 | 148篇 |
2010年 | 100篇 |
2009年 | 109篇 |
2008年 | 135篇 |
2007年 | 108篇 |
2006年 | 76篇 |
2005年 | 84篇 |
2004年 | 69篇 |
2003年 | 66篇 |
2002年 | 65篇 |
2001年 | 55篇 |
2000年 | 63篇 |
1999年 | 57篇 |
1998年 | 178篇 |
1997年 | 133篇 |
1996年 | 109篇 |
1995年 | 68篇 |
1994年 | 63篇 |
1993年 | 54篇 |
1992年 | 43篇 |
1991年 | 45篇 |
1990年 | 34篇 |
1989年 | 50篇 |
1988年 | 25篇 |
1987年 | 34篇 |
1986年 | 43篇 |
1985年 | 25篇 |
1984年 | 38篇 |
1983年 | 45篇 |
1982年 | 33篇 |
1981年 | 28篇 |
1980年 | 28篇 |
1979年 | 34篇 |
1978年 | 24篇 |
1977年 | 28篇 |
1976年 | 28篇 |
1974年 | 9篇 |
1972年 | 6篇 |
排序方式: 共有2838条查询结果,搜索用时 15 毫秒
41.
Satoru Sano Noriko Saito Shin-ichi Matsuda Naoki Ohashi Hajime Haneda You Arita Minoru Takemoto 《Journal of the American Ceramic Society》2006,89(2):568-574
Forsterite (Mg2 SiO4 ) ceramics were prepared using Mg(OH)2 and SiO2 as precursors, and the effect of powder characteristics of Mg(OH)2 on calcination and sintering was investigated. The use of highly dispersed Mg(OH)2 powder (HD powder) resulted in a lower calcination temperature. Forsterite powder of high homogeneity and small particle size prepared from the HD powder enabled synthesis of high-density forsterite ceramics by ordinary sintering without applying external pressure. Moreover, transparent forsterite ceramics were successfully synthesized through addition of excess Mg to the precursors to compensate for Mg evaporated during the sintering process. Subsequent dielectric measurements revealed that the transparent forsterite ceramics had a very low dielectric loss (tan δ<10−4 ). 相似文献
42.
Two models have been proposed to explain the mechanical strength increase of abraded or indented soda–lime glasses upon aging, namely, crack tip blunting and the release of residual tensile stress near the crack tip. To clarify the mechanism, the time dependence of the strengthening of an abraded soda–lime glass was investigated. Effects of aging media, such as moist air, distilled water, 1 N HCI and 1 N NaOH solutions, as well as the abrasion flaw depth, were determined. The strength increase rate in water of abraded soda–lime glass was compared with those of borosilicate and high-silica glasses. The effect of stressing during aging was also investigated. It was found that the rate of strength increase was faster with decreasing abrasion flaw depth and with decreasing chemical durability. For a given flaw depth, an acidic solution produced the fastest strengthening. The strengthening rate was found to accelerate because of the "coaxing'effect of stressing during aging. From these observations, it was concluded that the strengthening rates relate to the diffusion process and chemical reactions, especially the alkali–hydrogen (or hydronium) ion-exchange reaction, near the crack tip. The role of the residual tensile stress appears to be similar to that of the applied tensile stress, helping the diffusion process near the crack tip. The observed strength increase of soda–lime glass by aging was thus attributed to the effective blunting of the crack tip geometry by the glass–water reaction. 相似文献
43.
Foam-breaking with a rotating disk mechanical foam-breaker (MFRD) was studied for a foaming system containing a diluted detergent solution in a laboratory sparged agitated vessel. The change of the foam-breaking capacity of the MFRD by varying the air sparge rate, the working volume and the impeller speed or the disk diameter was measured. Based on these measurements, empirical equations are presented for predicting the critical foam-breaking regions of the MFRD fitted with the agitated vessel. The operational range where foam-breaking with the MFRD can be carried out effectively and economically is also discussed. 相似文献
44.
Bronson D. Hausmann Emily M. Aaldenberg Minoru Tomozawa 《Journal of the American Ceramic Society》2021,104(7):3087-3096
Silica glass samples were given various heat treatments under stress at low temperatures and subsequently their residual stress distributions in terms of retardance were observed using a polarized light microscope, confirming previously reported fast surface stress relaxation while providing more detailed characterization. Retardance profiles of silica glass fibers heat-treated under a constant bending strain in the presence of atmospheric water vapor were measured and fit to a previously developed diffusion-based relaxation model. The retardance of a cross-section of a silica glass rod heat-treated at 650°C in lab air under applied torsional shear strain was also measured to confirm the presence of residual surface shear stress which was predicted by the decrease of torque with time for the rod. Together, these results confirm the low-temperature fast surface stress relaxation which occurs when water vapor is present for both bending and shear stresses. 相似文献
45.
46.
Copper was alloyed with small amounts of Al (0.2, 0.5, 1.0 and 2.0 mass%) to improve the oxidation resistance. Copper (6 N) and the Cu-Al alloys were oxidized at 773-1173 K in 0.1 MPa oxygen atmosphere after hydrogen annealing at 873 K. Continuous very thin Al2O3 layers were formed on the surface of all Cu-Al dilute alloys during the hydrogen annealing. Oxidation resistance of Cu-Al alloys was improved especially for Cu-2.0Al at 773-973 K, while it decreases on increasing the oxidation temperature. Cu-Al alloys followed the parabolic rate law at 1173 K, but most of other cases do not at and below 1073 K. Oxidation resistance for Cu-Al alloys was found relevant to the maintenance of the thin Al2O3 layer at the Cu2O/Cu-Al alloy interface. 相似文献
47.
Kenichi Yokoyama Toshio Ogawa Kenzo Asaoka Junichi Sakai 《Journal of Alloys and Compounds》2005,400(1-2):227-233
The hydrogen absorption properties of Ti–0.2 mass% Pd (Ti–0.2Pd) alloy in 2.0% and 0.2% acidulated phosphate fluoride (APF) and neutral 2.0% NaF solutions (25 °C) has been evaluated by hydrogen thermal desorption analysis. During the early stage of immersion (120 h) in the 2.0% APF solution, the amount of absorbed hydrogen was lower than 500 mass ppm. A thermal desorption of hydrogen primary appearing with a peak at 500–600 °C and a broad desorption ranging from 100 to 400 °C were observed. In the 0.2% APF solution, the amount of absorbed hydrogen saturated at 100–200 mass ppm; the thermal desorption of hydrogen appeared with a single peak at 550 °C. In the 2.0% NaF solution, hydrogen absorption was negligible even after 1000 h of immersion, although corrosion pits were observed. The results of the present study suggest that the hydrogen absorption of Ti–0.2Pd alloy, as compared with commercial pure titanium, is suppressed in fluoride solutions. 相似文献
48.
49.
A phenomenon was discovered wherein light scattering strength from cracks increases when tensile stress is applied to micro-cracks produced in the interlayer dielectric film by chemical mechanical polishing treatment. It is likely that the change in light scattering intensity occurs because a region of high stress concentration (region with high variation in index of refraction) is produced near the crack tip due to stress, thus forming a type of scatterer. With this method, it is possible to detect only scatterers which respond to stress, and thus, it is possible to classify and separately detect cracks and particles. 相似文献
50.
Hideaki Adachi Toshifumi Satoh Masahiro Sakai Koichi Mizuno Kentaro Setsune 《Journal of Superconductivity》1994,7(4):737-741
Epitaxial multilayer thin films of infinite-layer (Sr, Ca)CuO2 and perovskite (Sr, Ca)RuO3 have been prepared on (100) SrTiO3 substrates by multitarget rf magnetron sputtering. X-ray diffraction analyses revealed that the multilayer structure of (Sr, Ca)CuO3/(Sr, Ca)RuO3 was successfully fabricated with a minimum layer thickness of 20 Å. Transmission electron microscopy measurements of the multilayers indicated that there was no dislocation which normally exists in single-layer films with an infinite-layer structure. Resistivities of multilayer films at room temperature ranged from 1 to 10 m cm and showed semiconductor-like dependence against the temperature. 相似文献