全文获取类型
收费全文 | 169181篇 |
免费 | 6863篇 |
国内免费 | 841篇 |
专业分类
电工技术 | 1931篇 |
综合类 | 2846篇 |
化学工业 | 27995篇 |
金属工艺 | 6589篇 |
机械仪表 | 5106篇 |
建筑科学 | 5180篇 |
矿业工程 | 895篇 |
能源动力 | 3129篇 |
轻工业 | 15936篇 |
水利工程 | 2116篇 |
石油天然气 | 1128篇 |
武器工业 | 70篇 |
无线电 | 14046篇 |
一般工业技术 | 30711篇 |
冶金工业 | 22571篇 |
原子能技术 | 736篇 |
自动化技术 | 35900篇 |
出版年
2023年 | 805篇 |
2022年 | 1007篇 |
2021年 | 2183篇 |
2020年 | 1858篇 |
2019年 | 1955篇 |
2018年 | 16974篇 |
2017年 | 15891篇 |
2016年 | 12860篇 |
2015年 | 3286篇 |
2014年 | 3670篇 |
2013年 | 6954篇 |
2012年 | 8249篇 |
2011年 | 13800篇 |
2010年 | 12005篇 |
2009年 | 8951篇 |
2008年 | 10325篇 |
2007年 | 10874篇 |
2006年 | 2823篇 |
2005年 | 3457篇 |
2004年 | 3122篇 |
2003年 | 3036篇 |
2002年 | 2289篇 |
2001年 | 1419篇 |
2000年 | 1396篇 |
1999年 | 1433篇 |
1998年 | 6310篇 |
1997年 | 4037篇 |
1996年 | 2636篇 |
1995年 | 1607篇 |
1994年 | 1299篇 |
1993年 | 1324篇 |
1992年 | 498篇 |
1991年 | 513篇 |
1990年 | 431篇 |
1989年 | 424篇 |
1988年 | 418篇 |
1987年 | 362篇 |
1986年 | 349篇 |
1985年 | 397篇 |
1984年 | 359篇 |
1983年 | 271篇 |
1982年 | 322篇 |
1981年 | 360篇 |
1980年 | 357篇 |
1979年 | 227篇 |
1978年 | 226篇 |
1977年 | 534篇 |
1976年 | 1096篇 |
1975年 | 176篇 |
1973年 | 182篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
991.
JaeHyunKim JounHoLee JiChulLim ChangHoonLee MooHyoungSong JuYeonYoon HeeDongChoi JeomJaeKim ChangHoOh SangDeogYeo 李路海 《现代显示》2004,31(5):31-33
薄膜晶体管液晶电视(TFT-LCD TV)因为具有薄、轻、紧凑和可随意放置的特点,已经占据了大部分电视机市场。除了这些物理特性以外,最重要的特性是已具有了良好像质的对比度。为了将对比度提高到1:600以上,对偏振片膜、背光源板、滤色片树脂、电极锥角和摩擦条件等都进行了研究。优化的背光板组合,光滑的电极锥角和摩擦方法的控制是提高对比度的主要控制因素。应用新开发的滤色片树脂,对获得高对比度最为有效。 相似文献
992.
P. Dubé F. Kerdouss F. Laplante P. Proulx L. Brossard H. Ménard 《Journal of Applied Electrochemistry》2003,33(6):541-547
The electrocatalytic hydrogenation of cyclohexanone has been investigated with catalytic powder particles made of metal nanoaggregates deposited on a nonconductive material such as activated carbon and alumina. The catalytic powder particles were suspended in the solution under vigorous stirring conditions. The brief contact of the powder particles with a porous carbon cathode was sufficient to form adsorbed hydrogen on the metallic nanoaggregates through water electrolysis and initiate the electrohydrogenation process. It is demonstrated that the key parameters of the electrohydrogenation process are both the nature of the metallic nanoaggregates and the nature of the non-conductive material. The hydrodynamics of the solution under vigorous stirring conditions have also been studied for the particular cell used in the present study. 相似文献
993.
Lime mortars are often used for repairs to historic buildings. This paper investigates two forms of lime binder: fat and feebly-hydraulic,
in order to predict their long-term behaviours and hence ascertain which of the two possesses greater durability, so that
they may be used more efficiently in restoration. Mortars were tested for properties governing moisture movement and also
subject to durability cycles. The resistance to damage under freezing conditions was evaluated with the saturation coefficient.
Thermal cycles had no effect on the mortars and gave no indication of the relative durabilities of the binders. Salt crystallization
cycles, though effective in distinguishing the more durable of the two, were too aggressive to gauge a clear profile of salt
weathering and succeeded in rapidly decomposing the samples. Tests on the properties governing moisture movement produced
good indications of the degree to which the mortars permit flow through their fabrics. According to the results obtained,
fat lime mortars are more durable than those made with feebly-hydraulic lime. The results also suggest that the feebly-hydraulic
lime mortars are at a higher risk of decomposition by granular disintegration whereas fat lime mortars are better suited to
damp, slightly exposed conditions. These results disagree with the general opinion that hydraulic limes are more durable than
fat limes due to the additional strength and water insolubility arising from their hydraulicity. 相似文献
994.
995.
Javier Lara-Romero Rafael Maya-Yescas José Luis Rico-Cerda José Luis Rivera-Rojas Fernando Chiñas Castillo Matey Kaltchev 《Thin solid films》2006,496(2):463-468
The thermal decomposition of model extreme-pressure lubricant additives on clean iron was studied in ultrahigh vacuum conditions using molecular beam strategies. Methylene chloride and chloroform react to deposit a solid film consisting of FeCl2 and carbon, and evolve only hydrogen into the gas phase. No gas-phase products and less carbon on the surface are detected in the case of carbon tetrachloride. Dimethyl and diethyl disulfide react on clean iron to deposit a saturated sulfur plus carbon layer at low temperatures (∼600 K) and an iron sulfide film onto a Fe + C underlayer at higher temperatures (∼950 K). Methane is the only gas-phase product when dimethyl disulfide reacts with iron. Ethylene and hydrogen are detected when diethyl disulfide is used. 相似文献
996.
De Fruyt Filip; Van Leeuwen Karla; Bagby R. Michael; Rolland Jean-Pierre; Rouillon Frédéric 《Canadian Metallurgical Quarterly》2006,18(1):71
Structural, mean- and individual-level, differential, and ipsative personality continuity were examined in 599 patients treated for major depression assigned to 1 of 6 forms of a 6-month pharmaco-psychotherapy program. Covariation among traits from the Five Factor model remained invariant across treatment, and patients described themselves as slightly more extraverted, open to experience, agreeable and conscientious, and substantially more emotional stable after treatment. Trait changes were only to a small extent explained by changes in depression severity. There was evidence for differential, individual-level, and ipsative stability, with stable personality profiles in terms of shape and to a lesser extent in terms of scatter and elevation. Traits remain relatively stable, except for emotional stability, despite the depressive state and the psychopharmacological interventions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
997.
Chr. Bargholtz L. Gerén V. N. Grebenev Yu. B. Gurov V. S. Karpukhin I. V. Laukhin B. V. Martem’yanov V. A. Matveev K. Lindberg V. S. Sopov P. -E. Tegnér B. A. Chernyshev R. R. Shafigullin I. Zartova 《Instruments and Experimental Techniques》2006,49(4):461-467
A zero-degree spectrometer for tagging η mesons on the CELSIUS/WASA facility is described, and its characteristics are presented. Tagging of η mesons is performed by detecting 3He ions produced by reaction pd → 3Heη close to the production threshold. The low background level (<2%) is in good agreement with the data obtained earlier on the SATURNE accelerator. 相似文献
998.
This research focused on the syllable as a processing unit in handwriting. Participants wrote, in uppercase letters, words that had been visually presented. The interletter intervals provide information on the timing of motor production. In Experiment 1, French participants wrote words that shared the initial letters but had different syllable boundaries. In Experiment 2, French- and Spanish-speaking participants wrote cognates and pseudowords with a letter sequence that was always intrasyllabic in French and intersyllabic in Spanish. In Experiment 3, French-Spanish bilinguals wrote the cognates and pseudowords with the same type of sequences. In the 3 experiments, the critical interletter intervals were longer between syllables than within syllables, indicating that word syllable structure constrains motor production both in French and Spanish. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
999.
Time dependent behavior of elements combining ultra-high performance fiber reinforced concretes (UHPFRC) and reinforced concrete 总被引:1,自引:1,他引:0
Structural elements combining Ultra-High Performance Fiber Reinforced Concretes (UHPFRC) and concrete offer a high potential
in view of rehabilitation and modification of existing structures. The investigation of the time-dependent behavior of composite
“UHPFRC-concrete” elements is a fundamental step in the determination of durability and serviceability. For this, an experimental
program was conducted on large composite “UHPFRC-concrete” beams and a numerical model was validated with the test results.
The experimental results and a parametric study performed with the numerical model showed that UHPFRC and normal strength
reinforced concrete are compatible in the long-term and that the critical period of composite “UHPFRC-concrete” elements are the first 90 days after the casting of the UHPFRC layer. Thus, the high potential
of such composite elements can be exploited also in the long term. 相似文献
1000.
Summary Polymer composites have recently received a considerable amount of scientific and technological interest, because their properties
can be properly controlled, choosing the adequate doped particles, their size and concentrations, and the synthesis conditions.
In this work we report the synthesis and characterization of a polystyrene (PS) matrix doped with different concentrations
of iron nanoparticles.
X-ray diffraction and transmission electron microscopy were used to characterize the structure of the samples. The behaviour
of the d.c. electrical conductivity (σdc) and the complex permittivity (ε*=ε′-iε′′) as a function of frequency (100 Hz–10 MHz) reflects the important effect of the iron nanoparticles concentration in the
sample properties. A percolation threshold in the conductivity was observed at a critical concentration of iron nanoparticles.
A noticeable increase in the saturation magnetization and coercivity is observed with the rise of the iron nanoparticles concentration,
being thisbehaviour also noticed in the remanent magnetization. A rise of the initial a.c. susceptibility with the iron concentration
is also observed. 相似文献