全文获取类型
收费全文 | 91497篇 |
免费 | 8979篇 |
国内免费 | 4780篇 |
专业分类
电工技术 | 5850篇 |
技术理论 | 11篇 |
综合类 | 6767篇 |
化学工业 | 15157篇 |
金属工艺 | 5026篇 |
机械仪表 | 5631篇 |
建筑科学 | 6690篇 |
矿业工程 | 2824篇 |
能源动力 | 2847篇 |
轻工业 | 6264篇 |
水利工程 | 1823篇 |
石油天然气 | 4394篇 |
武器工业 | 936篇 |
无线电 | 11067篇 |
一般工业技术 | 11071篇 |
冶金工业 | 4671篇 |
原子能技术 | 1150篇 |
自动化技术 | 13077篇 |
出版年
2024年 | 408篇 |
2023年 | 1483篇 |
2022年 | 2829篇 |
2021年 | 3894篇 |
2020年 | 2927篇 |
2019年 | 2499篇 |
2018年 | 2749篇 |
2017年 | 2974篇 |
2016年 | 2710篇 |
2015年 | 3756篇 |
2014年 | 4546篇 |
2013年 | 5710篇 |
2012年 | 5964篇 |
2011年 | 6189篇 |
2010年 | 5604篇 |
2009年 | 5301篇 |
2008年 | 5164篇 |
2007年 | 4854篇 |
2006年 | 4868篇 |
2005年 | 4109篇 |
2004年 | 3102篇 |
2003年 | 3104篇 |
2002年 | 3628篇 |
2001年 | 3251篇 |
2000年 | 2387篇 |
1999年 | 2169篇 |
1998年 | 1706篇 |
1997年 | 1435篇 |
1996年 | 1165篇 |
1995年 | 1009篇 |
1994年 | 760篇 |
1993年 | 601篇 |
1992年 | 493篇 |
1991年 | 408篇 |
1990年 | 273篇 |
1989年 | 256篇 |
1988年 | 206篇 |
1987年 | 120篇 |
1986年 | 116篇 |
1985年 | 98篇 |
1984年 | 46篇 |
1983年 | 33篇 |
1982年 | 51篇 |
1981年 | 43篇 |
1980年 | 45篇 |
1979年 | 30篇 |
1977年 | 22篇 |
1976年 | 23篇 |
1974年 | 17篇 |
1973年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Rapid synthesis of silver nanowires(Ag NWs) with high quality and a broad processing window is challenging because of the low selectivity of the formation of multiply twinned particles at the nucleation stage for subsequent Ag NWs growth.Herein we report a systematic study of the water-involved heterogeneous nucleation of Ag NWs with high rate(less than 20 min) in a simple and scalable preparation method.Using glycerol as a reducing agent and a solvent with a high boiling point,the reaction is rapidly heated to 210 ℃ in air to synthesize Ag NWs with a very high yield in gram level.It is noted that the addition of a small dose of water plays a key role for obtaining highly pure Ag NWs in high yield,and the optimal water/glycerol ratio is0.25%.After investigating a series of forming factors including reaction temperature and dose of catalysts,the formation kinetics and mechanism of the Ag NWs are proposed.Compared to other preparation methods,our strategy is simple and reproducible.These Ag NWs show a strong Raman enhancement effect for organic molecules on their surface. 相似文献
22.
23.
Ming-Puu Chen Asta Y. Z. Lord Yu-Yao Cheng Ku-Chou Tai Wen-Harn Pan 《Journal of Computer Assisted Learning》2020,36(3):383-396
Reflective judgement is crucial for medical-related practitioners in dealing with controversial issues. However, the conformity phenomenon is likely to occur and interfere with reflective judgement learning during interactive activities. Effective strategies are required to moderate the conformity behaviour tendency (CBT) and improve reflective judgement performance (RJP). This study demonstrates two significant results: (a) Compared with the guided self-reflection learning strategy, the online collective reflection (OCR) learning strategy effectively weakened the learners' general CBT while dealing with professional controversial issues; and (b) a significantly negative correlation between the RJP achieved and the change of CBT in online environment was detected in the OCR group. The implications and potential applications in higher education were discussed. Further studies are needed to confirm the long-term effects and the extending application to other professional studies. 相似文献
24.
Bo Wang Edison Huixiang Ang Yang Yang Yufei Zhang Hongbo Geng Minghui Ye Cheng Chao Li 《Advanced functional materials》2020,30(28)
Orthorhombic molybdenum trioxide (MoO3) is one of the most promising anode materials for sodium‐ion batteries because of its rich chemistry associated with multiple valence states and intriguing layered structure. However, MoO3 still suffers from the low rate capability and poor cycle induced by pulverization during de/sodiation. An ingenious two‐step synthesis strategy to fine tune the layer structure of MoO3 targeting stable and fast sodium ionic diffusion channels is reported here. By integrating partially reduction and organic molecule intercalation methodologies, the interlayer spacing of MoO3 is remarkably enlarged to 10.40 Å and the layer structural integration are reinforced by dimercapto groups of bismuththiol molecules. Comprehensive characterizations and density functional theory calculations prove that the intercalated bismuththiol (DMcT) molecules substantially enhanced electronic conductivity and effectively shield the electrostatic interaction between Na+ and the MoO3 host by conjugated double bond, resulting in improved Na+ insertion/extraction kinetics. Benefiting from these features, the newly devised layered MoO3 electrode achieves excellent long‐term cycling stability and outstanding rate performance. These achievements are of vital significance for the preparation of sodium‐ion battery anode materials with high‐rate capability and long cycling life using intercalation chemistry. 相似文献
25.
26.
Kang Zhang Rong‐rong Wang Kai‐rui Zhang Fei Cheng Yu Tian Yi Lin Mi Zhou Pu‐xin Zhu 《Polymer International》2020,69(3):274-279
A series of hyperbranched poly(citric polyethylene glycol) (PCPEG) materials with varied polyethylene glycol (PEG) chain lengths as plasticizers were mixed with maize starch (MS) via cooking and film‐forming. The structure, pasting property, plasticization, aging property, moisture absorption and compatibility of plasticized starches were studied by means of Fourier transform infrared spectroscopy, X‐ray diffraction, rapid viscosity analysis, tension testing, moisture absorption measurements and scanning electron microscopy. Compared with PEG and citric acid, PCPEG was more effective in promoting starch chain movement and inhibiting the retrogradation of starch film. Also, PCPEG/MS had smaller moisture content. The longer the plasticizer chain, the better were the aging resistance and moisture resistance of starch. But with an increase of PEG chain length, mechanical properties of PCPEG/MS deteriorated and the compatibility between PCPEG and MS decreased. The hyperbranched derivative of PEG with longer chain exhibited improved plasticization and compatibility with starch. © 2019 Society of Chemical Industry 相似文献
27.
28.
29.
【摘要】 目的 研究和探讨125I粒子条联合胆道支架植入治疗恶性梗阻性黄疸的临床疗效。方法 2011年6月—2013年9月收治恶性梗阻性黄疸患者40例。行胆道支架植入术治疗患者18例,为对照组;采用125I粒子条联合胆道支架植入患者22例,为观察组。两组均采用经皮肝穿刺胆道引流(PTCD)并胆道支架植入。结果 观察组与对照组的平均胆道开通时间分别为(8.7 ± 0.7)和(6.2 ± 0.4)个月,两组比较差异有统计学意义(P < 0.05)。观察组与对照组术后平均生存时间分别为(11.4 ± 0.8)和(8.7 ± 0.5)个月,生存时间的差异有统计学意义(P < 0.05)。术后近期疗效及并发症两组之间的比较无明显差异(P > 0.05),但是远期疗效有显著差异(P < 0.05)。结论 与对照组相比,观察组的术后生存时间及胆道开通时间明显延长,对于125I粒子条联合支架治疗恶性梗阻性黄疸值得进一步临床研究。
相似文献
相似文献
30.