全文获取类型
收费全文 | 98735篇 |
免费 | 9062篇 |
国内免费 | 4635篇 |
专业分类
电工技术 | 6007篇 |
技术理论 | 13篇 |
综合类 | 6917篇 |
化学工业 | 16893篇 |
金属工艺 | 5342篇 |
机械仪表 | 6437篇 |
建筑科学 | 7885篇 |
矿业工程 | 3186篇 |
能源动力 | 3086篇 |
轻工业 | 6462篇 |
水利工程 | 1832篇 |
石油天然气 | 6177篇 |
武器工业 | 975篇 |
无线电 | 11126篇 |
一般工业技术 | 11518篇 |
冶金工业 | 4459篇 |
原子能技术 | 1078篇 |
自动化技术 | 13039篇 |
出版年
2024年 | 406篇 |
2023年 | 1765篇 |
2022年 | 3221篇 |
2021年 | 4354篇 |
2020年 | 3227篇 |
2019年 | 2720篇 |
2018年 | 3024篇 |
2017年 | 3324篇 |
2016年 | 2963篇 |
2015年 | 4067篇 |
2014年 | 4995篇 |
2013年 | 6010篇 |
2012年 | 6443篇 |
2011年 | 6890篇 |
2010年 | 6173篇 |
2009年 | 5910篇 |
2008年 | 5895篇 |
2007年 | 5275篇 |
2006年 | 5332篇 |
2005年 | 4455篇 |
2004年 | 2998篇 |
2003年 | 2657篇 |
2002年 | 2624篇 |
2001年 | 2330篇 |
2000年 | 2304篇 |
1999年 | 2518篇 |
1998年 | 1930篇 |
1997年 | 1632篇 |
1996年 | 1489篇 |
1995年 | 1256篇 |
1994年 | 1073篇 |
1993年 | 770篇 |
1992年 | 623篇 |
1991年 | 444篇 |
1990年 | 356篇 |
1989年 | 274篇 |
1988年 | 207篇 |
1987年 | 134篇 |
1986年 | 97篇 |
1985年 | 57篇 |
1984年 | 46篇 |
1983年 | 40篇 |
1982年 | 39篇 |
1981年 | 26篇 |
1980年 | 28篇 |
1979年 | 11篇 |
1974年 | 2篇 |
1970年 | 2篇 |
1959年 | 3篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Xiaohu Ren Xilou Pu Hongfeng Yin Yun Tang Hudie Yuan Huiqing Fan 《Ceramics International》2021,47(9):12122-12129
Hexagonal barium ferries is a promising and efficient microwave (MW) absorbing material, but the low dielectric loss and poor conductivity have limited their extensive applications. In this work, a simple tactic of coating conductive polymer PANI on hexaferrite BaCo2Fe16O27 is presented, wherein the dielectric properties are customized, and more significantly, the electromagnetic loss is greatly enhanced. As displayed from structural characterizations, PANI were coated equably on the surface of hexaferrite grains by an in-situ polymerization process. The outcomes exhibit the as-prepared PANI@hexaferrite composite has remarkable electromagnetic wave absorption capacity. When the thickness is 6.0 mm, the minimal RL of ?40.4 dB was achieved at 2.9 GHz. The effective absorption bandwidth (RL < ?20 dB) of 0.65 GHz, 0.53 GHz, 0.65 GHz, 0.52 GHz, 0.46 GHz and 0.39 GHz was achieved separately when the thickness ranges from 4 to 9 mm. The highly efficient MW absorbing performance of PANI@hexaferrite composite were the consequence of multiple loss mechanisms and perfect impedance matching. It is demonstrated that the PANI@hexaferrite composite with excellent MW absorption performance is expected to be potential MW absorbers for extensive applications. 相似文献
42.
43.
For rechargeable wireless sensor networks, limited energy storage capacity, dynamic energy supply, low and dynamic duty cycles cause that it is unpractical to maintain a fixed routing path for packets delivery permanently from a source to destination in a distributed scenario. Therefore, before data delivery, a sensor has to update its waking schedule continuously and share them to its neighbors, which lead to high energy expenditure for reestablishing path links frequently and low efficiency of energy utilization for collecting packets. In this work, we propose the maximum data generation rate routing protocol based on data flow controlling technology. For a sensor, it does not share its waking schedule to its neighbors and cache any waking schedules of other sensors. Hence, the energy consumption for time synchronization, location information and waking schedule shared will be reduced significantly. The saving energy can be used for improving data collection rate. Simulation shows our scheme is efficient to improve packets generation rate in rechargeable wireless sensor networks. 相似文献
44.
Xiao-Ya Shangguan Bao-Lun Fang Chen-Xiao Xu Yuan Tan Yan-Gang Chen Zhi-Jun Xia Wei Chen 《Ceramics International》2021,47(5):6318-6328
A series of direct Z-scheme FeIn2S4/Bi2WO6 hierarchical heterostructures with intimate interface contacts were synthesized by in-situ growth route and characterized by systematical analyses. All as-prepared FeIn2S4/Bi2WO6 nanocomposites showed significantly enhanced photocatalytic activity towards photodegradation for the removal of tetracycline hydrochloride (TCH) in comparison with individual FeIn2S4 and Bi2WO6. Meanwhile, the highest photocatalytic degradation activity can be achieved by modulating adding amount of FeIn2S4 in FeIn2S4/Bi2WO6 nanocomposites and the optimized component ratio of FeIn2S4 to Bi2WO6 is determined to be 10 wt%. The enhanced photocatalytic activity could be ascribed to efficient separation between photogenerated holes and electrons based on the construction of direct Z-scheme system. The high photocatalytic stability of resultant 10 wt% FeIn2S4/Bi2WO6 nanocomposites was revealed through six successive recycling reactions. The main intermediate generated during TCH photodegradation was explored by HPLC-MS. Besides, the direct Z-scheme photocatalytic mechanism was confirmed by band position analysis, electron spin resonance (ESR) and active species capture experiment. 相似文献
45.
Wei LingNan Wang ZhenHua Zhang ZhiDong Liu Chieh-Wen Gao Xuan P. A. 《Nano Research》2020,13(5):1332-1338
Nano Research - We report the composition and back-gate voltage tuned transport properties of ternary compound Bi2(Te1−xSex)3 nanowires synthesized by chemical vapor deposition (CVD). It is... 相似文献
46.
Yue Gao Miao-miao Zhang Xiao-peng Guo Wen-jian Li Dong Lu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2020,95(5):1290-1297
Toxicity caused by the accumulation of butanol in fermentation media is an important factor limiting the concentration of butanol. There is currently no systematic research in place investigating the butanol tolerance mechanism of bacteria such as Clostridium acetobutylicum, which adapts to butanol stress and regulates its growth and metabolism. Here, research results related to the butanol tolerance of C. acetobutylicum are reviewed to understand the molecular basis of changes in butanol-tolerant strains. Organic solvent-tolerant bacteria play an important role in the fields of biofuel production, enzyme preparation and bioremediation. An analysis of limitations of the application of organic solvent-tolerant bacteria has revealed that future research should focus on combining the microbial tolerance phenotype with specific utilization to achieve an optimal balance between organic solvent tolerance and production. This review serves as a reference for the improvement and engineering of strains that tolerate organic solvents. © 2019 Society of Chemical Industry 相似文献
47.
48.
49.
Deep Integration of Innovation and Entrepreneurship (InE) Education in Chinese University Classrooms
Recently, InE has been regarded as a popular education strategy in Chinese universities. However, problems have been exposed in the adoption of InE, for example, in InE courses and competitions. The purpose of this paper is to provide a possible solution to the problems, which is to organize effective InE courses by integrating InE with Inter-Course-level Problem-Based Learning (ICPBL). A detailed case is demonstrated by an ICPBL elective course design with deep integration of InE in the teaching, learning, and assessments. This paper contributes to a new curriculum design for promoting InE education in practically for Chinese universities. 相似文献
50.
Chen Tang Tiehu Li Yuhang Bai Junjie Gao Wenbo Yang Shasha Jiao Tingkai Zhao 《Ceramics International》2018,44(10):11812-11819
Recently, ceramic matrix composites reinforced by short carbon fibers (CFs) attracted increasing attentions. To further improve mechanical properties and oxidation resistances, CFs were subjected to oxidation and acidification followed by sol-gel dip-coating to deposit ZrO2 on their surfaces. ZrO2-Cf/SiC composites were fabricated by joint hot compression molding and sintering, compared to Cf/SiC and SiC prepared by the same method. Microstructural analyses indicated that ZrO2 coatings were successfully deposited on CF surfaces, formed strong bonding and interfaces between CF and the matrix. Meanwhile, CFs were found uniformly distributed in SiC matrix with random orientations. Flexural curves of ZrO2-Cf/SiC and Cf/SiC revealed the presence of “false plasticity” regions after sharp drops, which were quite different from brittle flexural behavior of SiC ceramic. Compression strength of the three samples showed step-up growth. ZrO2-Cf/SiC exhibited the highest value, indicating the introduction of CFs and ZrO2 coatings do have great influence on mechanical performances. After heat treatment, ZrO2-Cf/SiC exhibited better oxidation resistance than Cf/SiC, with weight loss ratios estimated to ??3.76% and ??6.43%, respectively. These improved properties indicated that ZrO2-Cf/SiC would be excellent alternatives to other existence materials under ultra-high temperature environments. 相似文献