全文获取类型
收费全文 | 6966篇 |
免费 | 665篇 |
国内免费 | 475篇 |
专业分类
电工技术 | 505篇 |
综合类 | 406篇 |
化学工业 | 1127篇 |
金属工艺 | 525篇 |
机械仪表 | 542篇 |
建筑科学 | 636篇 |
矿业工程 | 229篇 |
能源动力 | 219篇 |
轻工业 | 318篇 |
水利工程 | 171篇 |
石油天然气 | 477篇 |
武器工业 | 43篇 |
无线电 | 734篇 |
一般工业技术 | 920篇 |
冶金工业 | 363篇 |
原子能技术 | 63篇 |
自动化技术 | 828篇 |
出版年
2024年 | 28篇 |
2023年 | 121篇 |
2022年 | 261篇 |
2021年 | 354篇 |
2020年 | 256篇 |
2019年 | 201篇 |
2018年 | 212篇 |
2017年 | 214篇 |
2016年 | 181篇 |
2015年 | 246篇 |
2014年 | 362篇 |
2013年 | 423篇 |
2012年 | 428篇 |
2011年 | 472篇 |
2010年 | 456篇 |
2009年 | 405篇 |
2008年 | 383篇 |
2007年 | 365篇 |
2006年 | 374篇 |
2005年 | 322篇 |
2004年 | 217篇 |
2003年 | 227篇 |
2002年 | 256篇 |
2001年 | 232篇 |
2000年 | 188篇 |
1999年 | 219篇 |
1998年 | 132篇 |
1997年 | 124篇 |
1996年 | 91篇 |
1995年 | 96篇 |
1994年 | 48篇 |
1993年 | 47篇 |
1992年 | 36篇 |
1991年 | 30篇 |
1990年 | 17篇 |
1989年 | 24篇 |
1988年 | 19篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有8106条查询结果,搜索用时 15 毫秒
11.
利用理想的地质体积模型和电阻率测井的供电电流流过模型的导电机理,推导出一种不需要含水饱和度参数即能定量计算含水饱和度的方法,即岩性类比解释法。经过初步实践,该方法应用于砂泥岩地层的测井分析,效果良好。 相似文献
12.
13.
Sungwon Kim Zuo Wang Hagan D.J. Van Stryland E.W. Kobyakov A. Lederer F. Assanto G. 《Quantum Electronics, IEEE Journal of》1998,34(4):666-672
We demonstrate and compare two phase-insensitive all-optical transistors (AOT's) based on frequency-degenerate quadratic three-wave interactions. In particular, we demonstrate gain using KTP in a type II geometry. Both AOT's exploit the phase insensitivity inherent to three-wave parametric processes when only two fields are input, providing amplification of a small signal at the operating frequency via the interaction with a second-harmonic wave. The first scheme is based on successive up- and down-conversion (i.e., cascading) while the second relies on parametric down-conversion. We obtain gains of 5 and 160 in the two configurations, respectively, with a significant background and output coherent to the pump in the first case, no background and coherence between output and signal in the second 相似文献
14.
15.
16.
论述了可重复高压灌浆锚杆的结构构造以及其独特的灌浆工艺,探讨了该类锚杆的承载能力特性。文中还给出了该类锚杆在不同地层中应用的几个实例。 相似文献
17.
Qing YangKaibin Tang Chunrui WangJian Zuo Daoyuan ZhangYitai Qian 《Thin solid films》2003,436(2):203-207
SnS2 films have been deposited on glass and alumina plate substrates by the reactions between an organotin precursor [tetrabuyltin, (CH2CH2CH2CH3)4Sn] and carbon disulfide in n-hexane at the temperature range 180-200 °C for 10-40 h. The reaction system was oxygen free and applied at a moderate temperature. The films so prepared were characterized by techniques of X-ray diffraction, Scanning electron microscopy, Raman and Mössbauer spectroscopies. The films deposited on glass as well as on alumina plate have an average thickness of 30 μm, but have different rose-like morphologies, which are influenced by both the anisotropic growths of crystals and the different substrate structures. Photoluminescence measurements show that the films have an emission peak at approximately 590 nm. 相似文献
18.
The stability of five major phenolics, namely (−)-epicatechin (EC), procyanidin B2 (PC-B2), chlorogenic acid (ChA), hyperoside (HP) and isoquercitrin (IQ), in hawthorn fruits and a canned hawthorn drink were evaluated during 6 months of storage in the dark at three different temperatures (4, 23 and 40 °C). HPLC with a diode-array detector was used to determine the contents of the individual compounds. The results showed that the studied phenolics in the hawthorn fruits and the drink were both stable at 4 °C and relatively unstable at 23 and 40 °C with varied extents of degradation. At room temperature (23 °C), marked degradations of EC and PC-B2 were observed in both the fruits and the drink with around 50% and 30% decrease after a 6-month storage, respectively. A more significant decrease of the phenolics was observed at 40 °C, especially for EC and PC-B2, which were almost completely degraded after a 6-month storage. HP, IQ and ChA were relatively stable at 23 °C, but unstable at 40 °C. Therefore, low-temperature storage is recommended for maintaining the quality and efficacy of hawthorn fruits and its preparations. 相似文献
19.
Mei Xuan Xu Wen Guang Liu Yun Lin Guan Zuo Peng Bi Kang De Yao 《Polymer International》1995,38(2):205-209
The phase behavior of a hybrid polymer network (HPN) composed of poly[(propylene glycol maleate)-co-(propylene glycol phthalate)] crosslinked with styrene and polyester–urethane crosslinked with methylene-bis-ortho-chloroaniline was examined. The correlation between phase separation and impact strength of the HPNs is discussed. The composition of HPNs has an effect on their properties. 相似文献
20.