全文获取类型
收费全文 | 292044篇 |
免费 | 22273篇 |
国内免费 | 11291篇 |
专业分类
电工技术 | 15644篇 |
技术理论 | 31篇 |
综合类 | 17632篇 |
化学工业 | 50663篇 |
金属工艺 | 17027篇 |
机械仪表 | 18667篇 |
建筑科学 | 23117篇 |
矿业工程 | 9593篇 |
能源动力 | 8008篇 |
轻工业 | 16877篇 |
水利工程 | 4856篇 |
石油天然气 | 20405篇 |
武器工业 | 2262篇 |
无线电 | 31885篇 |
一般工业技术 | 34670篇 |
冶金工业 | 15375篇 |
原子能技术 | 2912篇 |
自动化技术 | 35984篇 |
出版年
2024年 | 1228篇 |
2023年 | 4702篇 |
2022年 | 8035篇 |
2021年 | 11599篇 |
2020年 | 8613篇 |
2019年 | 7332篇 |
2018年 | 8254篇 |
2017年 | 9312篇 |
2016年 | 8100篇 |
2015年 | 11310篇 |
2014年 | 13931篇 |
2013年 | 16627篇 |
2012年 | 17969篇 |
2011年 | 19616篇 |
2010年 | 16947篇 |
2009年 | 16131篇 |
2008年 | 15645篇 |
2007年 | 15269篇 |
2006年 | 16190篇 |
2005年 | 14313篇 |
2004年 | 9145篇 |
2003年 | 8048篇 |
2002年 | 7400篇 |
2001年 | 6552篇 |
2000年 | 7160篇 |
1999年 | 8564篇 |
1998年 | 6885篇 |
1997年 | 5849篇 |
1996年 | 5481篇 |
1995年 | 4532篇 |
1994年 | 3776篇 |
1993年 | 2636篇 |
1992年 | 2153篇 |
1991年 | 1609篇 |
1990年 | 1180篇 |
1989年 | 939篇 |
1988年 | 766篇 |
1987年 | 528篇 |
1986年 | 392篇 |
1985年 | 268篇 |
1984年 | 185篇 |
1983年 | 121篇 |
1982年 | 130篇 |
1981年 | 87篇 |
1980年 | 71篇 |
1979年 | 24篇 |
1978年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
Process object is the instance of process. Vertexes and edges are in the graph of process object. There are different types of the object itself and the associations between object. For the large-scale data, there are many changes reflected. Recently, how to find appropriate real-time data for process object becomes a hot research topic. Data sampling is a kind of finding c hanges o f p rocess o bjects. There i s r equirements f or s ampling to be adaptive to underlying distribution of data stream. In this paper, we have proposed a adaptive data sampling mechanism to find a ppropriate d ata t o m odeling. F irst o f all, we use concept drift to make the partition of the life cycle of process object. Then, entity community detection is proposed to find changes. Finally, we propose stream-based real-time optimization of data sampling. Contributions of this paper are concept drift, community detection, and stream-based real-time computing. Experiments show the effectiveness and feasibility of our proposed adaptive data sampling mechanism for process object. 相似文献
52.
Scientometrics - Specialized academic social networking sites are gaining popularity in scientific communication. A huge volume of interdisciplinary information is generated when researchers from... 相似文献
53.
Journal of Computer Science and Technology - DOACROSS loops are significant parts in many important scientific and engineering applications, which are generally exploited pipeline/wave-front... 相似文献
54.
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
55.
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
56.
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
57.
Wei-Li Xie Xiao-Dong Zhang Wen-Hui Liu Qi Xie Guang-Wu Wen Xiao-Xiao Huang Jian-Dong Zhu Fei-Xiang Ma 《稀有金属(英文版)》2019,(3)
SiC nano wires were fabricated on the silicon substrate dipped with a layer of Ni catalyst at 900 ℃ by gas pressure annealing processing. The morphologies and crystal structures were determined by scanning electron microscopy(SEM), transmission electron microscopy(TEM)and X-ray diffraction(XRD). The results show that the assynthesized nanowires are β-SiC single crystalline with diameter range of 50-100 nm, and length of tens of micron by directly annealing at 900 ℃. The SiC nano wires grow along the [111] direction with highly uniform morphology. And the possible growth mechanism of SiC nano wires is proposed.The present work provides an efficient strategy for the production of high-quality SiC nano wires. 相似文献
58.
采用异佛尔酮二异氰酸酯(IPDI)、聚乙二醇200、400、600、800(PEG200、PEG400、PEG600、PEG800)、2,2-二羟甲基丙酸(DMPA)、1-苯基-1,2-乙二醇、中和剂三乙胺(TEA)、甲乙酮肟等为原料,制备了一种阴离子聚氨酯分散剂.通过FTIR、GPC、TG表征了分散剂的结构与性能.利用自制的分散剂采用研磨法制备了液体靛蓝分散液,以液体靛蓝分散液粒径、离心稳定性、储存稳定性为指标,探讨了分散剂链长、用量对分散液性能的影响.结果表明,研磨1 h后,以PEG400为软段合成的聚氨酯分散剂用量为染料质量的60%时制备的液体靛蓝粒径为277.1 nm,1000 r/min离心稳定性达到93.98%,3000 r/min离心稳定性为51.13%,常温放置7 d后粒径变化在20 nm以内,染色后织物的颜色深度(K/S)为10左右,约是粉状靛蓝染色K/S的2倍,染色织物的颜色性能并未改变,SEM显示分散体颗粒大小分布均匀,与分散剂甲基萘磺酸钠的甲醛缩合物(MF)和木质素85A相比,其分散体系稳定性差别不大. 相似文献
59.
Wang Hay Kan Chenxi Wei Dongchang Chen Tao Bo Bao‐Tian Wang Yan Zhang Yangchao Tian Jun‐Sik Lee Yijin Liu Guoying Chen 《Advanced functional materials》2019,29(17)
Lithium‐rich disordered rock‐salt oxides have attracted great interest owing to their promising performance as Li‐ion battery cathodes. While experimental and theoretical efforts are critical in advancing this class of materials, a fundamental understanding of key property changes upon Li extraction is largely missing. In the present study, single‐crystal synthesis of a new disordered rock‐salt cathode material, Li1.3Ta0.3Mn0.4O2 (LTMO), and its use as a model compound to investigate Li concentration–driven evolution of local cationic ordering, charge compensation, and chemical distribution are reported. Through the combined use of 2D and 3D X‐ray nanotomography, it is shown that Li removal accompanied by oxygen oxidation is correlated with the development of morphological defects such as particle cracking. Chemical heterogeneity, quantified by subparticle level distribution of Mn valence state, is minimal during Mn redox, which drastically increases upon the formation of cracks during oxygen redox. Density functional theory and bond valence sum mismatch calculations reveal the presence of local short‐range ordering in the pristine oxide, which gradually disappears along with the extraction of Li. The study suggests that with cycling the transformation into true cation–disordered state can be expected, which likely impacts the voltage profile and obtainable energy density of the oxide cathodes. 相似文献
60.
In this research, maleic anhydride-α-octadecene copolymer and its derivative with phenylethylamine was synthesized and its effect on the crystallization of paraffins was investigated. This derivative, when added into second cut of vacuum gas oil and forth cut of vacuum gas oil, increases the size and improves aggregation of paraffin crystals observed by polarizing light microscopy, increases onset temperature and enthalpy of paraffin crystallization determined by differential scanning calorimetry, improves the dewaxing efficiency with dosage of 100?ppm explored by MEK-toluene dewaxing. 相似文献