全文获取类型
收费全文 | 74338篇 |
免费 | 8750篇 |
国内免费 | 4801篇 |
专业分类
电工技术 | 6680篇 |
技术理论 | 6篇 |
综合类 | 5438篇 |
化学工业 | 11157篇 |
金属工艺 | 6928篇 |
机械仪表 | 3851篇 |
建筑科学 | 6917篇 |
矿业工程 | 4455篇 |
能源动力 | 2070篇 |
轻工业 | 7333篇 |
水利工程 | 2299篇 |
石油天然气 | 4840篇 |
武器工业 | 779篇 |
无线电 | 7078篇 |
一般工业技术 | 7207篇 |
冶金工业 | 5796篇 |
原子能技术 | 1158篇 |
自动化技术 | 3897篇 |
出版年
2024年 | 364篇 |
2023年 | 1095篇 |
2022年 | 2098篇 |
2021年 | 2625篇 |
2020年 | 2887篇 |
2019年 | 2422篇 |
2018年 | 2340篇 |
2017年 | 2807篇 |
2016年 | 3077篇 |
2015年 | 3137篇 |
2014年 | 4778篇 |
2013年 | 4392篇 |
2012年 | 5593篇 |
2011年 | 5692篇 |
2010年 | 3926篇 |
2009年 | 4092篇 |
2008年 | 3709篇 |
2007年 | 4804篇 |
2006年 | 4394篇 |
2005年 | 3691篇 |
2004年 | 3148篇 |
2003年 | 2904篇 |
2002年 | 2498篇 |
2001年 | 2233篇 |
2000年 | 1854篇 |
1999年 | 1575篇 |
1998年 | 1113篇 |
1997年 | 860篇 |
1996年 | 791篇 |
1995年 | 625篇 |
1994年 | 509篇 |
1993年 | 350篇 |
1992年 | 325篇 |
1991年 | 234篇 |
1990年 | 204篇 |
1989年 | 149篇 |
1988年 | 124篇 |
1987年 | 81篇 |
1986年 | 61篇 |
1985年 | 68篇 |
1984年 | 51篇 |
1983年 | 22篇 |
1982年 | 30篇 |
1981年 | 26篇 |
1980年 | 30篇 |
1975年 | 7篇 |
1964年 | 10篇 |
1959年 | 14篇 |
1956年 | 6篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
多输入单输出逆高斯分布流域汇流模型 总被引:1,自引:0,他引:1
本文将逆高斯分布应用于由水库和区间组成的复杂的流域汇流系统,并建立了多输入单输出逆高斯单位线模型。讨论了模型参数的估计方法,并对沾益流域的雨洪资料进行了实例分析。 相似文献
42.
Xiang‐Dan Li Zhen‐Xin Zhong Sang‐Hoon Han Seung Hee Lee Myong‐Hoon Lee 《Polymer International》2005,54(2):406-411
From chloromethylated polyimide, a useful starting material for modification of aromatic polyimides, a thermocurable transparent polyimide having acrylate side groups was prepared. In the presence of 1,8‐diazabicyclo[5,4,0]undec‐7‐ene, chloromethylated polyimide was esterified with acrylic acid to synthesize poly(imide methylene acrylate). The polymer was soluble in organic solvent, which makes it possible to prepare a planar film by spin coating. The polymer film became insoluble after thermal treatment at 230 °C for 30 min. Optical transparency of the film at 400 nm (for 1 µm thickness) was higher than 98 % and not affected by further heating at 230 °C for 250 min. Adhesion properties measured by the ASTM D3359‐B method ranged from 4B to 5B. Preliminary results of planarization testing showed a high degree of planarization (DOP) value (>0.53). These properties demonstrate that poly(imide methylene acrylate) could be utilized as a thermocurable transparent material in fabricating display devices such as TFT‐LCD. Copyright © 2004 Society of Chemical Industry 相似文献
43.
Renjith Devasia CP Reghunadhan Nair P Sivadasan KN Ninan 《Polymer International》2005,54(8):1110-1118
Polyacrylonitrile terpolymers of various compositions consisting of acrylonitrile (AN), itaconic acid (IA) and methyl acrylate (MA) were synthesized by solution polymerization in dimethylsulfoxide. Increase in concentration of either IA or MA retarded the overall polymerization rate and the polymer molecular weight. The system consisting of AN + MA and varying IA concentration was more prone to retardation in comparison with the system composed of AN + IA with variable MA concentration. The retardation factors were quantified. Minor quantities of MA boost the reactivity of IA in the terpolymer system. The terpolymer was richer in MA vis‐à‐vis the feed. The thermal characteristics of the terpolymer were examined as a function of its composition. In contrast to the copolymer of AN and IA requiring 1–1.5 mol% IA, the terpolymer required an IA content of approximately 2.5 mol% for optimum thermal stability. The polymer with 90 mol% AN, 2.5 mol% IA and 7.5 mol% MA exhibited reasonably good char‐forming characteristics and thermal stability. The overall crystallinity and crystallite size of the polymers were found to decrease on incorporation of the comonomers. The ‘aromatization index’ of the copolymer increased with the temperature of pyrolysis through re‐organization of the tetrahydropyridine ladder structure. Copyright © 2005 Society of Chemical Industry 相似文献
44.
45.
Shuichi Yamamoto Teruaki Morihiro Koichi Ariyoshi Turkan Aktas 《Drying Technology》2005,23(6):1319-1330
As the surface properties of the drying materials are very important not only for the drying rate but also for the quality change during drying, the effects of surface concentration on the drying behavior of liquid foods (sugar solutions) were investigated by isothermal drying experiments and by numerical calculation experiments. The isothermal drying experiments with gelled sugar solution systems (sucrose and maltodextrin) were carried out at various relative humidity (RH) values (RH = 0 to 84%). Separate experiments were carried out for determination of the desorption isotherms.
The isothermal drying curves of sugar solutions at RH = 0 to 51% were very similar. Numerical simulations also showed that the drying curves of these sugars at the surface concentration = 0 and 0.1 are almost the same, although the concentration distributions are different.
When a small amount of gelatin was added to sugar solutions, the drying rate decreased remarkably as the gelatin might form a thin film (skin) near the surface, and consequently the retention of ethanol increased. 相似文献
The isothermal drying curves of sugar solutions at RH = 0 to 51% were very similar. Numerical simulations also showed that the drying curves of these sugars at the surface concentration = 0 and 0.1 are almost the same, although the concentration distributions are different.
When a small amount of gelatin was added to sugar solutions, the drying rate decreased remarkably as the gelatin might form a thin film (skin) near the surface, and consequently the retention of ethanol increased. 相似文献
46.
在由低压直流电源供电的电路中,往往电路的某些部位需要使用高于电源所供的电压,将电源所供的低压转换为较高的电压,常用的方法有3种:自举升压、电感升压、逆变升压。结合实际应用电路对各种升压方法从器件选择、升压原理、升压结果等诸方面进行分析、探讨,解决了总体供电电压不变时,局部高压产生的关键性问题。它对电子电器电路的设计人员有一定的启发作用,对优化电路、遴选器件有较强的参考价值。 相似文献
47.
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
48.
49.
蓄热式均热炉生产中存在问题的分析及解决方案 总被引:1,自引:0,他引:1
介绍了高温空气燃烧技术在均热炉上的应用情况,对应用中出现的问题进行了分析,并提出了解决方案。 相似文献
50.