全文获取类型
收费全文 | 20243篇 |
免费 | 1775篇 |
国内免费 | 839篇 |
专业分类
电工技术 | 935篇 |
综合类 | 1001篇 |
化学工业 | 3777篇 |
金属工艺 | 902篇 |
机械仪表 | 1038篇 |
建筑科学 | 1508篇 |
矿业工程 | 431篇 |
能源动力 | 690篇 |
轻工业 | 2037篇 |
水利工程 | 244篇 |
石油天然气 | 736篇 |
武器工业 | 88篇 |
无线电 | 2033篇 |
一般工业技术 | 2959篇 |
冶金工业 | 768篇 |
原子能技术 | 324篇 |
自动化技术 | 3386篇 |
出版年
2024年 | 94篇 |
2023年 | 337篇 |
2022年 | 561篇 |
2021年 | 837篇 |
2020年 | 683篇 |
2019年 | 549篇 |
2018年 | 720篇 |
2017年 | 794篇 |
2016年 | 776篇 |
2015年 | 808篇 |
2014年 | 1017篇 |
2013年 | 1584篇 |
2012年 | 1178篇 |
2011年 | 1379篇 |
2010年 | 1214篇 |
2009年 | 1148篇 |
2008年 | 1094篇 |
2007年 | 1077篇 |
2006年 | 1033篇 |
2005年 | 849篇 |
2004年 | 620篇 |
2003年 | 508篇 |
2002年 | 552篇 |
2001年 | 432篇 |
2000年 | 490篇 |
1999年 | 428篇 |
1998年 | 335篇 |
1997年 | 287篇 |
1996年 | 283篇 |
1995年 | 204篇 |
1994年 | 176篇 |
1993年 | 117篇 |
1992年 | 97篇 |
1991年 | 90篇 |
1990年 | 52篇 |
1989年 | 62篇 |
1988年 | 46篇 |
1987年 | 26篇 |
1986年 | 30篇 |
1985年 | 39篇 |
1984年 | 16篇 |
1983年 | 20篇 |
1982年 | 26篇 |
1981年 | 22篇 |
1980年 | 18篇 |
1979年 | 17篇 |
1978年 | 16篇 |
1977年 | 10篇 |
1976年 | 13篇 |
1974年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
Bican Osman Bayça Salih Uğur Kuleyin Hamdi Gümrük Recep 《Metal Science and Heat Treatment》2021,63(3-4):156-162
Metal Science and Heat Treatment - The effect of solid boronizing at 950°C for 2 and 4 h on the phase composition, microstructure, hardness and abrasive wear of steel AISI 304L is studied... 相似文献
22.
23.
24.
25.
26.
Hassan Hajjaj Gerard Goma Jean M. François 《International Journal of Food Science & Technology》2015,50(8):1731-1736
In submerged cultures performed in chemically defined fermentation medium containing glucose and glutamate, the growth and production of water‐soluble red pigments and citrinin by the filamentous fungus Monascus ruber were studied under various carbon/nitrogen (C/N) ratios. The specific production of the red pigments was optimal at a glucose/glutamate ratio of about 10 and then steadily decreased at higher C/N ratio. In contrast, the production of the mycotoxin increased with increased C/N with an optimum in the range of 30–45. In a fed‐batch mode, it was also found that the production of pigments was not favoured in fed‐batch mode by feeding the medium with glucose while keeping the C/N ratio lower than 10. This low production likely resulted from concurrent high accumulation of L‐malic acid that was reported to inhibit this production. In contrast, this mode of cultivation was rather favourable for the production of the mycotoxin. 相似文献
27.
Andrea Mariela Araya-Sibaja Valdir Soldi Carlos Eduardo Maduro Campos Simone Gonçalves Cardoso 《Drug development and industrial pharmacy》2015,41(5):851-858
Progesterone is a natural hormone steroid used in humans for several treatments and in livestock for artificial insemination, which exhibits two polymorphic forms at ambient conditions: form 1 and form 2. Form 2 is metastable and more soluble than form 1; however, it is not suitable to use as powder raw material because it transforms into form 1 by the effects of grinding. A polymorphic screening of progesterone based on polymer-induced heteronucleation method was performed as an alternative to prepare the metastable form. Polyvinyl alcohol, hydroxypropyl methylcellulose (HPMC), dextran, gelatin, polyisoprene (PI) and acrylonitrile-butadiene (NBR) copolymer were used. Crystals were prepared from 0.5, 10 and 40?mg/mL solutions in acetone at room temperature by solvent evaporation. The samples were characterized by X-ray powder diffraction, differential scanning calorimetry (DSC), scanning electron microcopy and attenuated total reflectance infrared Fourier transform spectroscopy. Form 1 was nucleated from 40?mg/mL solutions on the six polymers and from 10?mg/mL solutions on PI and NBR. The mixture of form 1 and form 2 was obtained from 10?mg/mL solution on HPMC, dextran and gelatin and from 0.5?mg/mL solution crystallizations. Therefore, the polymeric devices, which crystallized the metastable and more soluble polymorph (2) of progesterone, would be a promissory alternative for the pharmaceutical applications. 相似文献
28.
29.
Machine Intelligence Research - This paper proposes an image encryption algorithm LQBPNN (logistic quantum and back propagation neural network) based on chaotic sequences incorporating quantum... 相似文献
30.