全文获取类型
收费全文 | 145068篇 |
免费 | 12717篇 |
国内免费 | 7478篇 |
专业分类
电工技术 | 8110篇 |
技术理论 | 4篇 |
综合类 | 12461篇 |
化学工业 | 29756篇 |
金属工艺 | 11073篇 |
机械仪表 | 6240篇 |
建筑科学 | 14540篇 |
矿业工程 | 5577篇 |
能源动力 | 9718篇 |
轻工业 | 10441篇 |
水利工程 | 4326篇 |
石油天然气 | 8744篇 |
武器工业 | 1116篇 |
无线电 | 9254篇 |
一般工业技术 | 14780篇 |
冶金工业 | 9099篇 |
原子能技术 | 2280篇 |
自动化技术 | 7744篇 |
出版年
2024年 | 596篇 |
2023年 | 2482篇 |
2022年 | 4135篇 |
2021年 | 4837篇 |
2020年 | 4924篇 |
2019年 | 4269篇 |
2018年 | 3886篇 |
2017年 | 4752篇 |
2016年 | 4998篇 |
2015年 | 5087篇 |
2014年 | 8083篇 |
2013年 | 8402篇 |
2012年 | 9769篇 |
2011年 | 10557篇 |
2010年 | 7711篇 |
2009年 | 8225篇 |
2008年 | 7285篇 |
2007年 | 9328篇 |
2006年 | 8539篇 |
2005年 | 7182篇 |
2004年 | 6316篇 |
2003年 | 5579篇 |
2002年 | 4651篇 |
2001年 | 4065篇 |
2000年 | 3436篇 |
1999年 | 2830篇 |
1998年 | 2204篇 |
1997年 | 1889篇 |
1996年 | 1693篇 |
1995年 | 1406篇 |
1994年 | 1196篇 |
1993年 | 896篇 |
1992年 | 788篇 |
1991年 | 603篇 |
1990年 | 526篇 |
1989年 | 390篇 |
1988年 | 310篇 |
1987年 | 242篇 |
1986年 | 176篇 |
1985年 | 181篇 |
1984年 | 160篇 |
1983年 | 119篇 |
1982年 | 76篇 |
1981年 | 60篇 |
1980年 | 70篇 |
1979年 | 51篇 |
1977年 | 27篇 |
1976年 | 22篇 |
1975年 | 26篇 |
1951年 | 33篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
周明 《徐州工程学院学报》2008,23(3):44-47
张仲谋教授的新著《宋词欣赏教程》,是南京大学出版社出版的“江苏省高等学校精品教材系列”中的一种。该书共8章,既构成一个严谨的教学体系,又多有创新出彩之处;对于词的艺术个性有深刻的把握和精当的阐发;又善于引导学生,循循善诱。该书既是教材,亦具有学术专著的品格。 相似文献
12.
13.
Iwao Shimizu Yuji Naito Iwao Yamaguchi Katsuyuki Kaiho Hitoshi Mizoguchi Satoru Yanabu 《Electrical Engineering in Japan》2008,164(1):52-61
Using conventional high‐temperature superconducting wire, a model superconducting fault current limiter (SFCL) is made and tested. Solenoid coil using Bi2223 silver sheath wire is so made that inductance is as small as possible and a vacuum interrupter is connected in series to it. A conventional reactor coil is connected in parallel. When the fault current flows in this equipment, superconducting wire is quenched and current is transferred into the parallel coil because of voltage drop of superconducting wire. This large current in parallel coil actuates magnetic repulsion mechanism of vacuum interrupter. Due to opening of vacuum interrupter, the current in superconducting wire is broken. By using this equipment, current flow time in superconducting wire can be easily minimized. On the other hand, the fault current is also easily limited by large reactance of parallel coil. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(1): 52–61, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20315 相似文献
14.
Mayank Kashyap 《Powder Technology》2008,183(3):441-453
The effect of electric field on the hydrodynamics of nanoparticles was studied in a fluidized rectangular bed, with electrodes attached to two parallel walls. It was shown that the electric field of the order of 3 times the gravity markedly decreased the bed expansion and increased the solids volume fraction of nanoparticles fluidized by air. In these experiments, a light diode assembly was utilized to infer the local solids volume fractions within a rectangular bed of 10 nm silica particles. These experimental measurements yielded a two dimensional solids volume fraction distribution within the rectangular bed. The experimental results provided some new insights into the distribution of solids within the bed. The agglomerate diameters were computed using a momentum balance with the drag given by the Ergun equation and the empirical Richardson-Zaki method. Both methods yielded agglomerate diameters of the order of 100 μm and showed dependence on the strength of the electric field. The electric field decreased the granular temperature of the nanoparticles. 相似文献
15.
A model is presented for drying of a single porous particle with superheated steam and humid air. Experimental data for spherical porous ceramic particle reported in the literature were used for the validation of the model. An inversion temperature at which the evaporation rates within superheated steam and humid air are equal was predicted. The effect of thermophysical properties of the particle (permeability 10-14 - 10-17 m2, diameter 3 × 10-3 - 10 × 10-3 m) and operating variables (gas mass flux 0.26 - 0.78 kg m-2 s-1, drying agent temperature 120-200°C) is tested. The inversion temperature is shown to be affected by the thermophysical properties of the porous particle and of the drying agent. 相似文献
16.
Mirna Suárez-Quiroz Béatrice De Louise Oscar Gonzalez-Rios Michel Barel Bernard Guyot Sabine Schorr-Galindo & Joseph-Pierre Guiraud 《International Journal of Food Science & Technology》2005,40(6):605-611
Roasting coffee led to a drop in the ochratoxin A (OTA) concentration, as measured by the reference method, especially for dark type roasts. The way the beverage was prepared also affected the OTA content, which could paradoxically be higher than that of the initial roasted coffee. Assays on the thermal stability of pure OTA showed that it ought to be found in larger quantities in roasted coffee. This suggested that OTA was masked by reactions with the substrate during roasting. The absence of OTA in green coffee is therefore the best guarantee of safety. 相似文献
17.
Calculations and detailed first principle and thermodynamic analyses have been performed to understand the formation mechanism of K2Ti6O13 nanowires (NWs) by a hydrothermal reaction between bulk Na2Ti3O7 crystals and a KOH solution. It is found that direct ion exchange between K+ and Na+ plus H+ interactions with [TiO6] octahedra in Na2Ti3O7 promote the formation of an intermediate H2K2Ti6O14 phase. The large lattice mismatch between this intermediate phase and the bulk Na2Ti3O7 structure, and the large energy reduction associated with the formation of this intermediate phase, drive the splitting of the bulk crystal into H2K2Ti6O14 NWs. However, these NWs are not stable because of large [TiO6] octahedra distortion and are subject to a dehydration process, which results in uniform K2Ti6O13 NWs with narrowly distributed diameters of around 10 nm. 相似文献
18.
19.
M. Jayasankar 《Materials Letters》2007,61(3):790-793
Formation of aluminium titanate (AT) has been achieved at low temperature through sol-gel process using boehmite and titanium hydroxide as precursors by controlling the particle size at nanoscale followed by in-situ peptisation. The formations of AT phase, particle size distributions, sintering and thermal expansion characteristics, and microstructural features have been reported. DTA and XRD analysis have been performed to confirm the formation of AT. A 94% relative density was obtained for aluminium titanate sintered at 1550 °C with controlled grain size in the range of 2-3 μm. 相似文献
20.
在各糖厂现用连续离心机原有生产实践基础上,对其机械吸震、加温、布温、机索结构、物料密封、机座等部件做了进一步改进,并取得可观的实效。 相似文献