全文获取类型
收费全文 | 398009篇 |
免费 | 6259篇 |
国内免费 | 1459篇 |
专业分类
电工技术 | 6665篇 |
综合类 | 2529篇 |
化学工业 | 58667篇 |
金属工艺 | 17884篇 |
机械仪表 | 15995篇 |
建筑科学 | 10184篇 |
矿业工程 | 1804篇 |
能源动力 | 9142篇 |
轻工业 | 34952篇 |
水利工程 | 4136篇 |
石油天然气 | 3744篇 |
武器工业 | 5篇 |
无线电 | 47703篇 |
一般工业技术 | 78104篇 |
冶金工业 | 54183篇 |
原子能技术 | 4672篇 |
自动化技术 | 55358篇 |
出版年
2022年 | 1877篇 |
2021年 | 2763篇 |
2020年 | 1725篇 |
2019年 | 2050篇 |
2018年 | 22825篇 |
2017年 | 22607篇 |
2016年 | 15793篇 |
2015年 | 3567篇 |
2014年 | 4458篇 |
2013年 | 12937篇 |
2012年 | 12301篇 |
2011年 | 25744篇 |
2010年 | 22071篇 |
2009年 | 19910篇 |
2008年 | 20838篇 |
2007年 | 23375篇 |
2006年 | 8853篇 |
2005年 | 12236篇 |
2004年 | 10136篇 |
2003年 | 9692篇 |
2002年 | 7804篇 |
2001年 | 7289篇 |
2000年 | 6661篇 |
1999年 | 6993篇 |
1998年 | 16515篇 |
1997年 | 11485篇 |
1996年 | 8714篇 |
1995年 | 6625篇 |
1994年 | 5795篇 |
1993年 | 5648篇 |
1992年 | 4077篇 |
1991年 | 3861篇 |
1990年 | 3583篇 |
1989年 | 3399篇 |
1988年 | 3312篇 |
1987年 | 2619篇 |
1986年 | 2525篇 |
1985年 | 3189篇 |
1984年 | 2822篇 |
1983年 | 2580篇 |
1982年 | 2358篇 |
1981年 | 2405篇 |
1980年 | 2220篇 |
1979年 | 2065篇 |
1978年 | 1899篇 |
1977年 | 2190篇 |
1976年 | 2731篇 |
1975年 | 1594篇 |
1974年 | 1490篇 |
1973年 | 1561篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Madhu H. C. Edachery Vimal Lijesh K. P. Perugu Chandra Shekhar Kailas Satish V. 《Metallurgical and Materials Transactions A》2020,51(8):4086-4099
Metallurgical and Materials Transactions A - Hybrid nanocomposites have potential as wear-resistant materials. However, synthesizing these nanocomposites by conventional molten state methods result... 相似文献
62.
63.
Marcela Stoia Cornelia Păcurariu Ciprian Mihali Iosif Mălăescu Cătălin Nicolae Marin Aylin Căpraru 《Ceramics International》2019,45(2):2725-2735
Magnetic MnFe2O4 nanopowders were synthesized by an original solvothermal method in the absence and in the presence of tetra-n-butylammonium bromide (TBAB) and Tween 80 (TW) as surfactants. Manganese ferrite/polyaniline (PANI) hybrid materials were synthesized by in situ polymerization of aniline on the surface of MnFe2O4 using ammonium persulfate as oxidant. The purpose of the study was to investigate the influence of the two surfactants on the properties of the MnFe2O4 powders and of their composites with PANI. The specific surface area, the cumulative surface area of pores and the cumulative volume of pores are influenced by the nature of surfactant in case of MnFe2O4 powders and are higher by comparison to those of the MnFe2O4/PANI hybrid materials. The values of saturation magnetization in case of MnFe2O4 powders are higher than those of the hybrid materials and are not influenced by the surfactant nature. These features revealed that MnFe2O4 powders can be efficiently used as adsorbents for the purification of wastewaters. The values of the electrical conductivity of the composites exhibit a significant increase in comparison to the MnFe2O4 powders and depend on the surfactant nature. The highest value of electrical conductivity was achieved by the composite obtained using Tween 80 as surfactant (σDC = 54.5·10?5S?m?1) which was close to that of PANI (σDC = 61.2·10?5 S?m?1). The fact that the magnetic and electric properties of the synthesized MnFe2O4/PANI composites can be changed by design, demonstrate the high potential of these materials to be used in magneto-electric applications. 相似文献
64.
Potential mGAT4 inhibitors derived from the lead substance (S)-SNAP-5114 have been synthesized and characterized for their inhibitory potency. Variations from the parent compound included the substitution of one of its aromatic 4-methoxy and 4-methoxyphenyl groups, respectively, with a more polar moiety, including a carboxylic acid, alcohol, nitrile, carboxamide, sulfonamide, aldehyde or ketone function, or amino acid partial structures. Furthermore, it was investigated how the substitution of more than one of the aromatic 4-methoxy groups affects the potency and selectivity of the resulting compounds. Among the synthesized test substances (S)-1-{2-[(4-formylphenyl)bis(4-methoxyphenyl)-methoxy]ethyl}piperidine-3-carboxylic acid, that features a carbaldehyde function in place of one of the aromatic 4-methoxy moieties of (S)-SNAP-5114, was found to have a pIC50 value of 5.89±0.07, hence constituting a slightly more potent mGAT4 inhibitor than the parent substance while showing comparable subtype selectivity. 相似文献
65.
66.
67.
68.
V. I. Zubkov O. V. Kucherova I. N. Yakovlev A. V. Solomonov 《Russian Microelectronics》2015,44(3):203-209
An automated system for integrated electrophysical and optical studies of semiconductor nanoheterostructures, which operates in a wide temperature range from 15 to 475 K, is designed. The setup is intended to measure the temperature and frequency admittance and electroluminescence spectra of light-emitting diode and laser chips formed on substrates of diameter up to 50.2 mm, and the distribution of parameters over the wafer. The setup includes the closed-cycle helium cryogenic station, LCR meter, and temperature controller. The characterization results of nanoheterostructures with InGaN/GaN multiple quantum wells, which are used for creating highly efficient white and blue light-emitting diodes, are presented. 相似文献
69.
I. N. Andronov Yu. I. Ryabkov N. P. Bogdanov N. A. Severova A. N. Danilov I. V. Churilina 《Russian Metallurgy (Metally)》2015,2015(10):778-784
The influence of the thermal cycling conditions on the thermal-cycling creep of a TN-1 alloy and the related irreversible deformations is studied. The conditions under which an anomalous increase in the irreversible deformations begins are determined. The structural mechanism of the irreversible deformations of an equiatomic alloy is shown to be analogous to the structural mechanism of metal creep at high temperatures: it predominantly has a dislocation character. It is proposed to use the effect of anomalous increase in the deformation of materials with reversible martensitic transformations for forming parts made of these materials at low temperatures. 相似文献
70.