全文获取类型
收费全文 | 262141篇 |
免费 | 21970篇 |
国内免费 | 11668篇 |
专业分类
电工技术 | 16401篇 |
技术理论 | 18篇 |
综合类 | 15991篇 |
化学工业 | 42834篇 |
金属工艺 | 14038篇 |
机械仪表 | 16287篇 |
建筑科学 | 20908篇 |
矿业工程 | 6825篇 |
能源动力 | 7583篇 |
轻工业 | 17139篇 |
水利工程 | 4964篇 |
石油天然气 | 13837篇 |
武器工业 | 2152篇 |
无线电 | 32395篇 |
一般工业技术 | 31808篇 |
冶金工业 | 13133篇 |
原子能技术 | 2923篇 |
自动化技术 | 36543篇 |
出版年
2024年 | 1171篇 |
2023年 | 4139篇 |
2022年 | 7676篇 |
2021年 | 10462篇 |
2020年 | 7712篇 |
2019年 | 6440篇 |
2018年 | 7121篇 |
2017年 | 8168篇 |
2016年 | 7474篇 |
2015年 | 10013篇 |
2014年 | 12898篇 |
2013年 | 16153篇 |
2012年 | 16861篇 |
2011年 | 18915篇 |
2010年 | 16155篇 |
2009年 | 15649篇 |
2008年 | 15250篇 |
2007年 | 14670篇 |
2006年 | 14464篇 |
2005年 | 12506篇 |
2004年 | 8567篇 |
2003年 | 7178篇 |
2002年 | 6543篇 |
2001年 | 5831篇 |
2000年 | 5771篇 |
1999年 | 6271篇 |
1998年 | 5653篇 |
1997年 | 4633篇 |
1996年 | 4198篇 |
1995年 | 3528篇 |
1994年 | 2931篇 |
1993年 | 2294篇 |
1992年 | 1787篇 |
1991年 | 1327篇 |
1990年 | 1058篇 |
1989年 | 908篇 |
1988年 | 707篇 |
1987年 | 516篇 |
1986年 | 404篇 |
1985年 | 341篇 |
1984年 | 215篇 |
1983年 | 201篇 |
1982年 | 166篇 |
1981年 | 152篇 |
1980年 | 147篇 |
1979年 | 107篇 |
1978年 | 63篇 |
1977年 | 64篇 |
1976年 | 77篇 |
1975年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
Pyrochlore-type WO_3 powder was synthesized via hydrothermal method using aqueous sodium tungstate solution and oxalic acid as raw materials. The as-prepared powder was made into a soliquoid,from which films were made by dip coating process with indium-tin oxide(ITO).The obtained films were characterized by thermogravimetric and differential thermal analysis(TG-DTA), X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM), cyclic voltammetry(CV), chronoamperometry(CA) and ultravioletvisible(UV-Vis) absorption. Results show that the crystal of the pyrochlore-type WO_3 powder is perfect. When the calcination temperature rises from room temperature to500 ℃,the pyrochlore-type structure first becomes deformed, then it is destroyed and turns into amorphous phase,finally it will completely convert to WO_3 with a monoclinic structure. Electrochemical and optical tests demonstrate that the film calcined at 300 ℃ exhibits the best electrochromic performance and has a coloration efficiency of up to 68.5 cm~2 C~(-1) at 884 nm. 相似文献
52.
Ying Chen HuiLi Zhang YuNing Liang YanHua Gao Yongchao Li 《Petroleum Science and Technology》2019,37(7):787-795
In this study, a simple hydrothermal synthesis method was adapted for the preparation of Co-doping Co2+/F-/TiO2 nanotubes photocatalyst, and the micro-nano structure of catalysts prepared by biomimetic technology which makes the catalyst have super-oleophilicity property. Co2+/F-/TiO2 revealed improved photocatalytic performance for denitrification of light oil compared to single TiO2 photocatalysts. The enhance of photocatalytic activity can be attributed to narrowing the band gap, increasing the light response wavelength and exposing more highly active crystal surfaces due to synergistic effects of Co2+ and F? in the photocatalyst. 相似文献
53.
Baizhan Li Chenqiu Du Hong Liu Wei Yu Jie Zheng Meilan Tan Zhenxing Jin Wenjie Li Jing Wu Lu Chen Runming Yao 《Indoor air》2019,29(2):308-319
The extensive research interests in environmental temperature can be linked to human productivity / performance as well as comfort and health; while the mechanisms of physiological indices responding to temperature variations remain incompletely understood. This study adopted a physiological sensory nerve conduction velocity (SCV) as a temperature‐sensitive biomarker to explore the thermoregulatory mechanisms of human responding to annual temperatures. The measurements of subjects’ SCV (over 600 samples) were conducted in a naturally ventilated environment over all four seasons. The results showed a positive correlation between SCV and annual temperatures and a Boltzmann model was adopted to depict the S‐shaped trend of SCV with operative temperatures from 5°C to 40°C. The SCV increased linearly with operative temperatures from 14.28°C to 20.5°C and responded sensitively for 10.19°C‐24.59°C, while tended to be stable beyond that. The subjects’ thermal sensations were linearly related to SCV, elaborating the relation between human physiological regulations and subjective thermal perception variations. The findings reveal the body SCV regulatory characteristics in different operative temperature intervals, thereby giving a deeper insight into human autonomic thermoregulation and benefiting for built environment designs, meantime minimizing the temperature‐invoked risks to human health and well‐being. 相似文献
54.
55.
56.
57.
Multifunctional 3D Patternable Drug‐Embedded Nanocarrier‐Based Interfaces to Enhance Signal Recording and Reduce Neuron Degeneration in Neural Implantation
下载免费PDF全文
![点击此处可从《Advanced materials (Deerfield Beach, Fla.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
58.
59.
60.
The design of a microstrip‐fed annular‐ring slot antenna (ARSA) with circular polarization (CP) radiation is initially studied. To obtain CP radiation with broad 3‐dB axial ratio (AR) bandwidth that can cover the WiMAX 2.3 GHz (2305–2320 MHz, 2345–2360 MHz) and WLAN 2.4 GHz (2400–2480 MHz) bands, a novel technique of extending an inverted L‐shaped slot from the bottom section of the annular‐ring is proposed. To suppress the harmonic modes induced by the CP ARSA, the technique of integrating a defected ground structure into the annular‐ring slot is further introduced. From the measured results, 10‐dB impedance bandwidth and 3‐dB AR bandwidth of 44.86 and 9.68% were achieved by the proposed harmonic suppressed CP ARSA. Furthermore, average gain and radiation efficiency of ~4.7 dBic and 71%, respectively, were also exhibited across the bands of interest. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:337–345, 2015. 相似文献