全文获取类型
收费全文 | 205832篇 |
免费 | 15758篇 |
国内免费 | 7793篇 |
专业分类
电工技术 | 11241篇 |
技术理论 | 14篇 |
综合类 | 11215篇 |
化学工业 | 35697篇 |
金属工艺 | 10544篇 |
机械仪表 | 11997篇 |
建筑科学 | 16407篇 |
矿业工程 | 4942篇 |
能源动力 | 5849篇 |
轻工业 | 12681篇 |
水利工程 | 3211篇 |
石油天然气 | 11073篇 |
武器工业 | 1345篇 |
无线电 | 25482篇 |
一般工业技术 | 26698篇 |
冶金工业 | 11424篇 |
原子能技术 | 2114篇 |
自动化技术 | 27449篇 |
出版年
2024年 | 881篇 |
2023年 | 3262篇 |
2022年 | 5827篇 |
2021年 | 7907篇 |
2020年 | 5794篇 |
2019年 | 5007篇 |
2018年 | 5414篇 |
2017年 | 6199篇 |
2016年 | 5692篇 |
2015年 | 7290篇 |
2014年 | 9520篇 |
2013年 | 12269篇 |
2012年 | 12224篇 |
2011年 | 13870篇 |
2010年 | 11610篇 |
2009年 | 11460篇 |
2008年 | 10872篇 |
2007年 | 10467篇 |
2006年 | 10857篇 |
2005年 | 9630篇 |
2004年 | 6563篇 |
2003年 | 5776篇 |
2002年 | 5251篇 |
2001年 | 4723篇 |
2000年 | 4870篇 |
1999年 | 5656篇 |
1998年 | 5461篇 |
1997年 | 4445篇 |
1996年 | 4026篇 |
1995年 | 3340篇 |
1994年 | 2795篇 |
1993年 | 2213篇 |
1992年 | 1703篇 |
1991年 | 1281篇 |
1990年 | 1022篇 |
1989年 | 885篇 |
1988年 | 689篇 |
1987年 | 501篇 |
1986年 | 399篇 |
1985年 | 335篇 |
1984年 | 212篇 |
1983年 | 198篇 |
1982年 | 163篇 |
1981年 | 147篇 |
1980年 | 134篇 |
1979年 | 97篇 |
1978年 | 63篇 |
1977年 | 67篇 |
1976年 | 86篇 |
1975年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
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
32.
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
33.
34.
35.
36.
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
37.
38.
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
39.
40.
Understanding semantic word shifts in scientific domains is essential for facilitating interdisciplinary communication. Using a data set of published papers in the field of information retrieval (IR), this paper studies the semantic shifts of words in IR based on mining per-word topic distribution over time. We propose that semantic word shifts not only occur over time, but also over topics. The shifts are examined from two perspectives, the topic-level and the context-level. According to the over-time word-topic distribution, stable words and unstable words are recognized. The diverging and converging trends in the unstable type reveal characteristics of the topic evolution process. The context-level shifts are further detected by similarities between word vectors. Our work associates semantic word shifts with the evolving of topics, which facilitates a better understanding of semantic word shifts from both topics and contexts. 相似文献