全文获取类型
收费全文 | 4077篇 |
免费 | 318篇 |
国内免费 | 150篇 |
专业分类
电工技术 | 172篇 |
综合类 | 237篇 |
化学工业 | 590篇 |
金属工艺 | 251篇 |
机械仪表 | 234篇 |
建筑科学 | 397篇 |
矿业工程 | 70篇 |
能源动力 | 117篇 |
轻工业 | 267篇 |
水利工程 | 65篇 |
石油天然气 | 224篇 |
武器工业 | 27篇 |
无线电 | 550篇 |
一般工业技术 | 581篇 |
冶金工业 | 240篇 |
原子能技术 | 46篇 |
自动化技术 | 477篇 |
出版年
2024年 | 16篇 |
2023年 | 72篇 |
2022年 | 103篇 |
2021年 | 139篇 |
2020年 | 100篇 |
2019年 | 107篇 |
2018年 | 116篇 |
2017年 | 121篇 |
2016年 | 102篇 |
2015年 | 135篇 |
2014年 | 161篇 |
2013年 | 237篇 |
2012年 | 225篇 |
2011年 | 258篇 |
2010年 | 188篇 |
2009年 | 161篇 |
2008年 | 201篇 |
2007年 | 183篇 |
2006年 | 225篇 |
2005年 | 202篇 |
2004年 | 139篇 |
2003年 | 107篇 |
2002年 | 91篇 |
2001年 | 87篇 |
2000年 | 107篇 |
1999年 | 126篇 |
1998年 | 133篇 |
1997年 | 106篇 |
1996年 | 106篇 |
1995年 | 98篇 |
1994年 | 75篇 |
1993年 | 64篇 |
1992年 | 56篇 |
1991年 | 34篇 |
1990年 | 43篇 |
1989年 | 18篇 |
1988年 | 15篇 |
1987年 | 16篇 |
1986年 | 15篇 |
1985年 | 15篇 |
1984年 | 11篇 |
1983年 | 10篇 |
1982年 | 6篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有4545条查询结果,搜索用时 15 毫秒
51.
The structure evolution of silk fibroin (SF) in the nanocomposite films with graphene oxide (GO) was investigated and related to the enzymatic degradability and release property. The interaction with GO was found to induce conformation transition of SF from random coil to β-sheet. However, the surface binding constrained the rearrangement of the silk chains, leading to a decrease of β-sheet when GO content was more than 1.0%. The crystal structure of SF played a key role in the degradation of GO/SF composites. The preferential degradation of the hydrophilic blocks resulted in a faster degradation of SF films with higher β-sheet content. The addition of GO to SF matrix led to a slower release and a reduction of the burst release of RhB, the model compound. The release profile was well fitted to the Rigter–Peppas equation, from which the characteristic constant decreased and the diffusional exponent increased with increasing GO content but quickly leveled off when GO content was more than 1.0%. Degradation of the composites had little influence on the characteristic constant of RhB release, however, led to an increased diffusional exponent, which was more evident for the composites with higher β-sheet content. 相似文献
52.
EFFECTSOFNUCLEATIONAGENTSONEFFICIENCYOFBORONEXTRACTIONFROMMgO-B_2O_3-SiO_2SLAGS¥Zhang,Peixin;Lou,Hailing;Sui,Zhitong(Departmen?.. 相似文献
53.
Shigeji Taniguchi Toshio Shibata Naoyuki Asanuma Hanyi Lou Fuhui Wang Weitao Wu 《Oxidation of Metals》1993,39(5-6):457-473
The oxidation behavior of TiAl coupons coated with a fine-grain Co-30Cr-4Al (mass %) film of about 30-m thickness has been studied at 1100–1400 K in a flow of purified oxygen at atmospheric pressure for up to 500 ks. Three oxidation stages were recognized: initial transient, parabolic, and accelerated stages. However, at 1100 K a parabolic stage continues for more than 800 ks. The activation energy for parabolic oxidation agrees with reported values for the oxidation of alumina-former alloys, although the mass gains during the parabolic stages are relatively small at 1200 and 1300 K. Micropores developed mainly at the scale/coating and coating/substrate interfaces as oxidation proceeded. This is attributable to recrystallization of the coating during oxidation and a Kirkendall effect due to preferential diffusion of Co into the substrate. The accelerated oxidation can be explained in terms of the formation of rutile mounds on the scale. 相似文献
54.
55.
Suppression of carbon monoxide formation in oxide-coated TZM molybdenum X-ray rotating anodes 总被引:1,自引:0,他引:1
M. G. Benz M. R. Jackson K. A. Lou R. J. Zabala T. C. Tiearney Jr 《International Journal of Refractory Metals and Hard Materials》1995,13(6):327-336
Higher performance designs for rotating anode X-ray tubes have increased the average rotating anode temperature from below 1100 °C to well above 1300 °C. This temperature increase has accelerated the formation of carbon monoxide by reaction of carbon from the alloy substrate with oxygen from the emissive coating. The dominant carbon source is thought to be Mo2C grain boundary precipitates in the TZM molybdenum alloy substrate. The dominant oxygen source is thought to be TiO in the emissive coating. Placement of a monocarbide-forming reactive layer between the alloy substrate and the emissive coating has been demonstrated to lower the thermodynamic activity of the carbon source and dramatically reduce the rate of formation of carbon monoxide. 相似文献
56.
对工业纯铁、45钢和3Cr2W8V钢的低真空铬钛共渗进行了研究,探讨了共渗层的组织结构、生长过程以及温度、时间等工艺因素的影响。 相似文献
57.
In this work, we have put forth two different protocols to address a concrete secure multi-party computational (MPC) problem related to a triangle, of which the coordinates of the three vertices are confidentially kept by the three participants, respectively. The three parties wish to collaboratively compute the area of this triangle while preserving their own coordinate privacy. As one of the merits, our protocols employ weaker assumptions of the existence of pseudorandom generators. In particular, unlike massive secure MPC protocols that rely a lot on oblivious transfer, ours utilize a new computing idea called “pseudorandom-then-rounding” method to avoid this burdensome obstacle. The two protocols are based on different theorems, while they both make use of the same underlying idea. At last, we provide a detailed proof for the first protocol by a series of security reductions of our newly defined games, which seems somewhat stronger than the previous simulation-based proofs and a proof sketch for the second one. Analysis and discussion about the reasons are provided as well to round off our work. 相似文献
58.
59.
The MapReduce framework has become the de facto standard for big data processing due to its attractive features and abilities. One is that it automatically parallelizes a job into multiple tasks and transparently handles task execution on a large cluster of commodity machines. The increasing heterogeneity of distributed environments may result in a few straggling tasks, which prolong job completion. Speculative execution is proposed to mitigate stragglers. However, the existing speculative execution mechanism could not work efficiently as many speculative tasks are still slower than their original tasks. In this paper, we explore an approach to increase the efficiency of speculative execution, and further improve MapReduce performance. We propose the Partial Speculative Execution (PSE) strategy to make speculative tasks start from the checkpoint. By leveraging the checkpoint of original tasks, PSE can eliminate the costs of re-reading, re-copying, and re-computing the processed data. We implement PSE in Hadoop, and evaluate its performance in terms of job completion time and the efficiency of speculative execution under several kinds of classical workloads. Experimental results show that, in heterogeneous environments with stragglers, PSE completes jobs 56 % faster than that with no speculation and 12 % faster than that with LATE, an improved speculative execution algorithm. In addition, on average PSE can improve the efficiency of speculative execution by 24 % compared to LATE. 相似文献
60.