全文获取类型
收费全文 | 254258篇 |
免费 | 34701篇 |
国内免费 | 11621篇 |
专业分类
电工技术 | 16919篇 |
技术理论 | 16篇 |
综合类 | 16282篇 |
化学工业 | 49476篇 |
金属工艺 | 13802篇 |
机械仪表 | 15731篇 |
建筑科学 | 19977篇 |
矿业工程 | 7124篇 |
能源动力 | 7289篇 |
轻工业 | 21333篇 |
水利工程 | 4944篇 |
石油天然气 | 12901篇 |
武器工业 | 2258篇 |
无线电 | 31385篇 |
一般工业技术 | 34544篇 |
冶金工业 | 9851篇 |
原子能技术 | 2664篇 |
自动化技术 | 34084篇 |
出版年
2024年 | 950篇 |
2023年 | 3680篇 |
2022年 | 7538篇 |
2021年 | 10461篇 |
2020年 | 8955篇 |
2019年 | 8744篇 |
2018年 | 9324篇 |
2017年 | 10484篇 |
2016年 | 10344篇 |
2015年 | 13263篇 |
2014年 | 15265篇 |
2013年 | 18432篇 |
2012年 | 18256篇 |
2011年 | 18816篇 |
2010年 | 16945篇 |
2009年 | 16197篇 |
2008年 | 15553篇 |
2007年 | 14340篇 |
2006年 | 13988篇 |
2005年 | 11700篇 |
2004年 | 8242篇 |
2003年 | 7273篇 |
2002年 | 7189篇 |
2001年 | 6319篇 |
2000年 | 5695篇 |
1999年 | 4898篇 |
1998年 | 3366篇 |
1997年 | 2786篇 |
1996年 | 2662篇 |
1995年 | 2119篇 |
1994年 | 1738篇 |
1993年 | 1155篇 |
1992年 | 1005篇 |
1991年 | 678篇 |
1990年 | 534篇 |
1989年 | 451篇 |
1988年 | 343篇 |
1987年 | 227篇 |
1986年 | 168篇 |
1985年 | 117篇 |
1984年 | 72篇 |
1983年 | 60篇 |
1982年 | 69篇 |
1981年 | 47篇 |
1980年 | 48篇 |
1979年 | 29篇 |
1977年 | 4篇 |
1976年 | 10篇 |
1959年 | 15篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
133.
Donghai Xu Peng Feng Yang Wang Wanpeng Yang Yu Wang Shaoyan Sun 《American Institute of Chemical Engineers》2022,68(2):e17472
Corrosion and salt deposition problems severely restrict the industrialization of supercritical water oxidation. Transpiring wall reactor can effectively weaken these two problems by a protective water film. In this work, methanol was selected as organic matter, and the influences of vital structural parameters on water film properties and organic matter removal were studied via numerical simulation. The results indicate that higher than 99% of methanol conversion could be obtained and hardly affected by transpiration water layer, transpiring wall porosity and inner diameter. Increasing layer and porosity reduced reactor center temperature, but inner diameter's influence was lower relatively. Water film temperature reduced but coverage rate raised as layer, porosity, and inner diameter increased. Notably, the whole reactor was in supercritical state and coverage rate was only approximately 85% in the case of one layer. Increasing reactor length affected slightly the volume of the upper supercritical zone but enlarged the subcritical zone. 相似文献
134.
Scientometrics - Due to the development of academic, more and more attentions are paid to citation recommendation. To solve the citation recommendation problem, researchers begin to focus on the... 相似文献
135.
Hefei Zhao Xiaoqing Xie Paul Read Benjamin Loseke Stephen Gamet Wenkuan Li Changmou Xu 《International Journal of Food Science & Technology》2021,56(2):825-837
Enriching the micronutrients, selenium (Se) and lithium (Li), in grapes to improve their nutraceutical properties were implemented by foliar application of organic fertiliser rich in Se and Li onto five grape cultivars. The effects of this biofortification on vine vigour, fruit quality, overall micronutrients and phenolic compounds also were investigated. Agronomic biofortification was found greatly increased the Se and Li content in the whole grape by multiple times, meanwhile it did not significantly affect the vine vigour and fruit quality of grapes. However, the biofortification did impact the Ionome (including all the mineral nutrients and trace elements) and phenolic compounds in grapes and this varied among cultivars. This study demonstrated foliar spray of organic Se/Li fertiliser was a very effective strategy to biofortify these micronutrients in grape berries, particularly in the skin, and therefore might be a promising strategy to increase the consumption and awareness of these grapes. 相似文献
136.
Genki Saito Yuji Kunisada Takumi Watanabe Xuemei Yi Takahiro Nomura Norihito Sakaguchi Tomohiro Akiyama 《Journal of the American Ceramic Society》2019,102(1):524-532
Carbon-and-oxygen-doped AlN specimens were prepared by combustion synthesis using Al, graphite, and AlN. Graphite addition changed the product color from white to blue. By XRD, the lattice constant increased slightly with increasing carbon content. Blue AlN powder was synthesized with a molar ratio of the diluent AlN of 0.2-0.5 with a fixed graphite content of 0.05. At an AlN molar ratio exceeding 0.6, carbon was not successfully incorporated due to the lower reaction temperature. Calcination at 800°C in air removed residual graphite without changing the crystal structure or product color. Oxygen, nitrogen, and carbon analyses revealed that blue AlN powders contained 0.45-0.54 mass% carbon and 1.4-1.6 mass% oxygen, while the undoped AlN contained 0.021 mass% carbon and 0.94 mass% oxygen. The origin of the white-to-blue color change was investigated via reflection measurements. Blue AlN exhibits an absorption peak at 634 nm (1.96 eV). From first-principles electronic structure calculations, the C-doped AlN and carbon-and-oxygen-doped AlN with a 1:1 ratio could be classified as p-type, whereas the O-doped AlN and 1:3 carbon-and-oxygen-doped AlN were n-type. One reason for the absorption peak at 634 nm may be a transition from the conduction band to an upper unoccupied state. These results suggest the possible control of optical and electronic properties of AlN via carbon-and-oxygen doping. 相似文献
137.
Tian Xie Haixia Zhao Zunhang Lv Guangwen Xie Yan He 《International Journal of Hydrogen Energy》2021,46(1):581-588
This work demonstrates a facile Nb2O5-decorated electrocatalyst to prepare cost-effective Ni–Fe–P–Nb2O5/NF and compared HER & OER performance in alkaline media. The prepared electrocatalyst presented an outstanding electrocatalytic performance towards hydrogen evolution reaction, which required a quite low overpotential of 39.05 mV at the current density of ?10 mA cm?2 in 1 M KOH electrolyte. Moreover, the Ni–Fe–P–Nb2O5/NF catalyst also has excellent oxygen evolution efficiency, which needs only 322 mV to reach the current density of 50 mA cm?2. Furthermore, its electrocatalytic performance towards overall water splitting worked as both cathode and anode achieved a quite low potential of 1.56 V (10 mA cm?2). 相似文献
138.
Junling Guo Huayu Pei Ying Dou Siyuan Zhao Guosheng Shao Jinping Liu 《Advanced functional materials》2021,31(18):2010499
Lithium-sulfur batteries (LSBs) are considered a promising next-generation energy storage device owing to their high theoretical energy density. However, their overall performance is limited by several critical issues such as lithium polysulfide (PS) shuttles, low sulfur utilization, and unstable Li metal anodes. Despite recent huge progress, the electrolyte/sulfur ratio (E/S) used is usually very high (≥20 µL mg−1), which greatly reduces the practical energy density of devices. To push forward LSBs from the lab to the industry, considerable attention is devoted to reducing E/S while ensuring the electrochemical performance. To date, however, few reviews have comprehensively elucidated the possible strategies to achieve that purpose. In this review, recent advances in low E/S cathodes and anodes based on the issues resulting from low E/S and the corresponding solutions are summarized. These will be beneficial for a systematic understanding of the rational design ideas and research trends of low E/S LSBs. In particular, three strategies are proposed for cathodes: preventing PS formation/aggregation to avoid inadequate dissolution, designing multifunctional macroporous networks to address incomplete infiltration, and utilizing an imprison strategy to relieve the adsorption dependence on specific surface area. Finally, the challenges and future prospects for low E/S LSBs are discussed. 相似文献
139.
The capture of particles by charged droplets was simulated by considering the electrostatic interactions of droplet-droplet and droplet-particle. The results indicate that the electrostatic repulsion between droplets leads to a dynamic accumulation mode of particles. However, the droplet spacing has an insignificant effect on the capture efficiency when the electrostatic deposition predominates. The increase of droplet charge remarkably improves the capture efficiency, in which the capture of fine particles accounts for the largest proportion. Compared to the droplet charge, the droplet size shows a limited improvement in the capture efficiency. Reducing the droplet velocity prolongs the capture time instead of enhancing the capture capacity per unit time, thereby improving capture efficiency. 相似文献
140.
Wu Ge Mu Yi Susilo Willy Guo Fuchun Zhang Futai 《International Journal of Information Security》2019,18(3):321-331
International Journal of Information Security - Data integrity is a critical security issue in cloud storage. The data integrity checking schemes by a third-party auditor (TPA) have attracted a lot... 相似文献