全文获取类型
收费全文 | 3588篇 |
免费 | 391篇 |
国内免费 | 132篇 |
学科分类
工业技术 | 4111篇 |
出版年
2024年 | 8篇 |
2023年 | 53篇 |
2022年 | 97篇 |
2021年 | 146篇 |
2020年 | 103篇 |
2019年 | 66篇 |
2018年 | 94篇 |
2017年 | 100篇 |
2016年 | 128篇 |
2015年 | 161篇 |
2014年 | 204篇 |
2013年 | 251篇 |
2012年 | 224篇 |
2011年 | 234篇 |
2010年 | 223篇 |
2009年 | 179篇 |
2008年 | 229篇 |
2007年 | 163篇 |
2006年 | 192篇 |
2005年 | 131篇 |
2004年 | 104篇 |
2003年 | 116篇 |
2002年 | 137篇 |
2001年 | 110篇 |
2000年 | 78篇 |
1999年 | 79篇 |
1998年 | 71篇 |
1997年 | 69篇 |
1996年 | 50篇 |
1995年 | 45篇 |
1994年 | 31篇 |
1993年 | 26篇 |
1992年 | 22篇 |
1991年 | 35篇 |
1990年 | 11篇 |
1989年 | 12篇 |
1988年 | 13篇 |
1987年 | 6篇 |
1986年 | 11篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1982年 | 9篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1976年 | 12篇 |
1975年 | 5篇 |
1970年 | 4篇 |
1965年 | 3篇 |
1964年 | 3篇 |
排序方式: 共有4111条查询结果,搜索用时 281 毫秒
1.
Sangmin Lee Biao Che Meiling Tai Wanzhao Li Shin-Hyun Kim 《Advanced functional materials》2021,31(42):2105477
Hydrogel shells that compartmentalize the water core from the aqueous surrounding provide molecular selectivity on size and charge in transmembrane transport. It is highly demanding to produce thin hydrogel shells to minimize diffusion length and maximize core volume. Here, internal osmosis in water-in-oil-in-water-in-oil (W/O/W/O) triple-emulsion droplets is used to produce thin hydrogel shells enclosing a large water core. The triple-emulsion droplets are prepared to have an ultrathin middle oil layer using a capillary microfluidic device. The innermost water droplet has a higher osmolarity than the outer water layer containing photopolymerizable hydrogel precursors, which pumps water from the outer layer to the core through the ultrathin oil layer by the osmosis. Therefore, the outer layer gets thinner and hydrogel precursors are enriched while the size of the triple-emulsion droplets remains unchanged. Through photopolymerization of precursors and phase transfer from oil to water, hydrogel shells enclosing water core are produced in the water environment; the oil layer is ruptured for molecular exchange through the shells. The thickness and composition of the hydrogel shells are precisely controllable by the osmotic conditions. The shells show a high permeation rate due to the thinness as well as controlled cut-off threshold of permeation for neutral and charged molecules. 相似文献
2.
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
3.
4.
Yanlong Shi Xiaojuan Feng Haiyu Guan Jiahua Zhang Zhongai Hu 《International Journal of Hydrogen Energy》2021,46(12):8557-8566
Constructing high-efficient and nonprecious electrocatalysts is of primary importance for improving the efficiency of water splitting. Herein, a novel sunflower plate-like NiFe2O4/CoNi–S nanosheet heterostructure was fabricated via facile hydrothermal and electrodeposition methods. The as-fabricated NiFe2O4/CoNi–S heterostructure array exhibits remarkable bifunctional catalytic activity and stability toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline media. It presents a small overpotential of 219 mV and 149 mV for OER and HER, respectively, to produce a current density of 10 mA cm?2. More significantly, when the obtained electrodes are used as both the cathode and anode in an electrolyzer, a voltage of 1.57 V is gained at 10 mA cm?2, with superior stability for 72 h. Such outstanding properties are ascribed to: the 3D porous network structure, which exposes more active sites and accelerates mass transfer and gas bubble emission; the high conductivity of CoNi–S, which provides faster charge transport and thus promotes the electrocatalytic reaction of the composites; and the effective interface engineering between NiFe2O4 (excellent performance for OER) and CoNi–S (high activity for HER), which leads to a shorter transport pathway and thus expedites electron transfer. This work provides a new strategy for designing efficient and inexpensive electrocatalysts for water splitting. 相似文献
5.
6.
7.
8.
The photoelectrochemical behaviors of RuL2(NCS)2 dye-sensitized SnO2/TiO2 coupled solar cell was studied and compared with TiO2 single system. The coupled system shows higher incident photon-to-current conversion efficiency (IPCE) value than the single system. A maximum IPCE value in the coupled system with 3.5 μm-thick SnO2 and 7 μm-thick TiO2 attained 82.4% at 530 nm wavelength. The higher IPCE value in the coupled system is attributed to the charge separation by fast electron transfer process from the excited RuL2(NCS)2 dye to TiO2 to SnO2 in the system with different energy level. 相似文献
9.
阐述了企业人力资源投资财务评价应解决的两个重要问题:评价对象的分类和项目的财务现金流量的内容。 相似文献
10.