全文获取类型
收费全文 | 62283篇 |
免费 | 5530篇 |
国内免费 | 2043篇 |
专业分类
电工技术 | 2701篇 |
技术理论 | 2篇 |
综合类 | 2517篇 |
化学工业 | 11785篇 |
金属工艺 | 3195篇 |
机械仪表 | 3756篇 |
建筑科学 | 3505篇 |
矿业工程 | 1308篇 |
能源动力 | 1951篇 |
轻工业 | 4542篇 |
水利工程 | 713篇 |
石油天然气 | 2495篇 |
武器工业 | 337篇 |
无线电 | 8359篇 |
一般工业技术 | 9683篇 |
冶金工业 | 4618篇 |
原子能技术 | 716篇 |
自动化技术 | 7673篇 |
出版年
2024年 | 236篇 |
2023年 | 1001篇 |
2022年 | 1774篇 |
2021年 | 2584篇 |
2020年 | 1890篇 |
2019年 | 1861篇 |
2018年 | 2013篇 |
2017年 | 2032篇 |
2016年 | 2073篇 |
2015年 | 2434篇 |
2014年 | 3027篇 |
2013年 | 3962篇 |
2012年 | 3795篇 |
2011年 | 4464篇 |
2010年 | 3458篇 |
2009年 | 3393篇 |
2008年 | 3405篇 |
2007年 | 2923篇 |
2006年 | 2929篇 |
2005年 | 2420篇 |
2004年 | 1881篇 |
2003年 | 1693篇 |
2002年 | 1577篇 |
2001年 | 1374篇 |
2000年 | 1302篇 |
1999年 | 1379篇 |
1998年 | 1598篇 |
1997年 | 1275篇 |
1996年 | 1003篇 |
1995年 | 809篇 |
1994年 | 675篇 |
1993年 | 516篇 |
1992年 | 396篇 |
1991年 | 346篇 |
1990年 | 314篇 |
1989年 | 293篇 |
1988年 | 195篇 |
1987年 | 182篇 |
1986年 | 154篇 |
1985年 | 152篇 |
1984年 | 125篇 |
1983年 | 107篇 |
1982年 | 79篇 |
1981年 | 85篇 |
1980年 | 86篇 |
1979年 | 66篇 |
1978年 | 60篇 |
1977年 | 76篇 |
1976年 | 117篇 |
1975年 | 59篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Ava Kwong Cecilia Y. S. Ho Vivian Y. Shin Chun Hang Au Tsun Leung Chan Edmond S. K. Ma 《International journal of molecular sciences》2021,22(2)
The germline carrier of the BRCA1 pathogenic mutation has been well proven to confer an increased risk of breast and ovarian cancer. Despite BRCA1 biallelic pathogenic mutations being extremely rare, they have been reported to be embryonically lethal or to cause Fanconi anemia (FA). Here we describe a patient who was a 48-year-old female identified with biallelic pathogenic mutations of the BRCA1 gene, with no or very subtle FA-features. She was diagnosed with ovarian cancer and breast cancer at the ages of 43 and 44 and had a strong family history of breast and gynecological cancers. 相似文献
22.
Amino acid modified polyaspartic acids were evaluated as calcium-scale inhibitors. Feasibility of scale inhibition experiments was analyzed by molecular dynamics simulation and Gaussian optimization, and the scale inhibition mechanism was theoretically analyzed. Scale inhibition performance was studied by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, static scale inhibition experiments, and electrochemical performance testing, which provided an experimental basis for the molecular dynamics simulation. The experimental results showed that Arg-SA-PASP has better scale inhibition and corrosion inhibition performance than His-SA-PASP. The scale inhibition effect increased with increasing concentration. Electrochemical tests indicated that Arg-SA-PASP is an excellent scale and corrosion inhibitor. 相似文献
23.
24.
Lauren Folk Kiara Gonzales John Gales Michael Kinsey Elisabetta Carattin Tim Young 《火与材料》2020,44(4):585-606
Practitioners are continuing to develop egress modelling software for the design of the built environment. These models require data about human behaviour and factors for calibration, validation and verification. This study aims to address the specific data and knowledge gap: emergency egress of the elderly. Such data are difficult to collect given privacy and consent concerns, with strong relationships generally being required between residences and researchers. Through the observation of nine fire drills at six Canadian long-term care (LTC) and retirement homes, specific evacuation actions and behaviour were observed for 37 staff members and information about the evacuation of 56 residents was collected. These drills demonstrated that emergency egress in LTC and retirement homes is highly staff dependent with 72% of residents recorded requiring full assistance at all stages of movement in evacuation, and that the type of announced/unannounced drill and level of resident care will affect the type of data collected. The development of travel speed and pre-movement is discussed subject to limitation with qualitative behavioural insights of residents that were observed. This study provides valuable methodological discussion on how to conduct behavioural studies in similar highly restricted research environments. Specific attention is given to understanding the considerations that must be made when using fire drills as data sources, and the impact that these can have on using such data for modelling. This study may inform the initial setup and programming of evacuation models from an actions and behavioural perspectives of staff members and residents. 相似文献
25.
Peer-to-Peer Networking and Applications - 相似文献
26.
27.
既有公共建筑能耗中,围护结构节能潜力巨大。以兰州某既有办公建筑为例,采用DeST-C软件模拟围护结构不同材料厚度、窗型,得出系列负荷,通过对数据分析、比较,得出如下结论:外墙外保温适宜材料为50mm的挤塑板,最大热负荷节能率为45.66%;屋面适宜保温材料为65mm的挤塑板,最大热负荷节能率为4.25%;外窗各个朝向全部更换玻璃,推荐选用内张膜中空玻璃(双膜),最大热负荷节能率为7.36%;单独更换南向外窗材料,推荐选用真空镀膜复合中空玻璃,最大热负荷节能率为1.78%。 相似文献
28.
Eui Dae Jung Amit Kumar Harit Do Hui Kim Chung Hyeon Jang Jong Hyun Park Shinuk Cho Myoung Hoon Song Han Young Woo 《Advanced materials (Deerfield Beach, Fla.)》2020,32(30):2002333
A series of anionic conjugated polyelectrolytes (CPEs) is synthesized based on poly(fluorene-co-phenylene) by varying the side-chain ionic density from two to six per repeat units (MPS2-TMA, MPS4-TMA, and MPS6-TMA). The effect of MPS2, 4, 6-TMA as interlayers on top of a hole-extraction layer of poly(bis(4-phenyl)-2,4,6-trimethylphenylamine (PTAA) is investigated in inverted perovskite solar cells (PeSCs). Owing to the improved wettability of perovskites on hydrophobic PTAA with the CPEs, the PeSCs with CPE interlayers demonstrate a significantly enhanced device performance, with negligible device-to-device dependence relative to the reference PeSC without CPEs. By increasing the ionic density in the MPS-TMA interlayers, the wetting, interfacial defect passivation, and crystal growth of the perovskites are significantly improved without increasing the series resistance of the PeSCs. In particular, the open-circuit voltage increases from 1.06 V for the PeSC with MPS2-TMA to 1.11 V for the PeSC with MPS6-TMA. The trap densities of the PeSCs with MPS2,4,6-TMA are further analyzed using frequency-dependent capacitance measurements. Finally, a large-area (1 cm2) PeSC is successfully fabricated with MPS6-TMA, showing a power conversion efficiency of 18.38% with negligible hysteresis and a stable power output under light soaking for 60 s. 相似文献
29.
30.