全文获取类型
收费全文 | 10828篇 |
免费 | 946篇 |
国内免费 | 202篇 |
专业分类
电工技术 | 411篇 |
技术理论 | 1篇 |
综合类 | 276篇 |
化学工业 | 2473篇 |
金属工艺 | 442篇 |
机械仪表 | 416篇 |
建筑科学 | 482篇 |
矿业工程 | 116篇 |
能源动力 | 348篇 |
轻工业 | 1393篇 |
水利工程 | 94篇 |
石油天然气 | 258篇 |
武器工业 | 47篇 |
无线电 | 881篇 |
一般工业技术 | 2202篇 |
冶金工业 | 471篇 |
原子能技术 | 110篇 |
自动化技术 | 1555篇 |
出版年
2024年 | 32篇 |
2023年 | 155篇 |
2022年 | 237篇 |
2021年 | 436篇 |
2020年 | 346篇 |
2019年 | 313篇 |
2018年 | 431篇 |
2017年 | 458篇 |
2016年 | 484篇 |
2015年 | 434篇 |
2014年 | 590篇 |
2013年 | 994篇 |
2012年 | 697篇 |
2011年 | 798篇 |
2010年 | 689篇 |
2009年 | 603篇 |
2008年 | 515篇 |
2007年 | 419篇 |
2006年 | 392篇 |
2005年 | 276篇 |
2004年 | 209篇 |
2003年 | 184篇 |
2002年 | 190篇 |
2001年 | 154篇 |
2000年 | 133篇 |
1999年 | 139篇 |
1998年 | 189篇 |
1997年 | 135篇 |
1996年 | 118篇 |
1995年 | 97篇 |
1994年 | 87篇 |
1993年 | 81篇 |
1992年 | 50篇 |
1991年 | 45篇 |
1990年 | 41篇 |
1989年 | 42篇 |
1988年 | 30篇 |
1987年 | 34篇 |
1986年 | 32篇 |
1985年 | 63篇 |
1984年 | 63篇 |
1983年 | 52篇 |
1982年 | 52篇 |
1981年 | 55篇 |
1980年 | 56篇 |
1979年 | 44篇 |
1978年 | 38篇 |
1977年 | 38篇 |
1976年 | 40篇 |
1975年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Anna Hać 《Journal of Network and Systems Management》1994,2(1):49-62
This paper analyzes the performance of a switching architecture. The performance measures include the elapsed time of packet transfer and the waiting time to begin transfer. The architecture is partitioned depending on the type of network used and the expected traffic in the network. Every partition has a switch with a buffer that can absorb surges of bursty traffic within the network partition. The buffer size depends on the type of the network and incoming traffic. The partition size depends on the network bandwidth, network traffic, packet size and buffer size. Examples of different networks are used to show the applications of the model. The results show that the elapsed time of packet switch transfer depends exponentially on the number of partitions in the network. 相似文献
22.
Summary Both preferential adsorption coefficient λ and intrinsic viscosity [η] for poly (di-o-alkylphenyl methacrylates) /Tetrahydrofuran
(THF)/water have been determined. The results are discussed in relation to the steric effect of the ortho-substituent groups
on the aromatic ring. 相似文献
23.
共晶碳化物团球化对铸铁激光熔敷层抗裂性的影响 总被引:1,自引:1,他引:0
为提高铸铁表面大面积激光熔敷层抗裂性问题,通过冶金因元素控制熔敷层组织形态在熔敷材料中加入碱金属元素钾,研究了在激光快速加热条件下钾对铸铁激光熔敷层组织团球化的影响,进而分析了该球状组织对熔敷层抗裂性的影响,结果表明随熔敷金属内钾含量增多熔敷层内共晶碳化物组织呈球状及孤岛状,这种组织明显提高了熔敷层抗裂性,此外大量的渗碳体组织确保了熔敷层具有较高的耐磨性;获得了无裂纹的大面积搭接熔敷层,其对应合金系统为Fe-C-Si-Ni-K。 相似文献
24.
25.
26.
Dongming Peng Mi Lu 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2005,13(1):106-125
Although the notion of the parallelism in multidimensional applications has existed for a long time, it is so far unknown what the bound (if any) of inter-iteration parallelism in multirate multidimensional digital signal processing (DSP) algorithms is, and whether the maximum inter-iteration parallelism can be achieved for arbitrary multirate data flow algorithms. This paper explores the bound of inter-iteration parallelism within rate-balanced multirate multidimensional DSP algorithms and proves that this parallelism can always be achieved in hardware system given the availability of a large number of processors and the interconnections between them. 相似文献
27.
Ivan Fortelný Monika Lapčíková František Lednický Zdeněk Starý Zdeněk Kruliš 《Polymer Engineering and Science》2008,48(3):564-571
This article is focused on the phase structure development in immiscible polymer blends during melt mixing. Nonuniformity of the phase structure, i.e., the coexistence of areas containing particles with markedly different size distribution, was detected in quenched and compression molded samples of a number of various blends prepared by long and intensive mixing in the chamber of a Plasticorder. The same effect was found also for polystyrene/polyamide blends prepared in a twin‐screw extruder. It was shown that neglecting nonuniformity of the phase structure can lead to considerable error in evaluation of the effect of system parameters on the blend morphology. The reasons for the effect were discussed and it was found that inhomogeneous flow field in mixers is a plausible explanation of the nonuniform phase structure. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers 相似文献
28.
Pulkki-R?back Laura; Elovainio Marko; Kivim?ki Mika; Raitakari Olli T.; Keltikangas-J?rvinen Liisa 《Canadian Metallurgical Quarterly》2005,24(3):307
This study examined associations of temperament at ages 6 to 12 with body-mass index (BMI) and waist circumference (WC) at ages 24 to 30 years. The participants were 619 men and women derived from the population-based Cardiovascular Risk in Young Finns Study. Temperament was operationalized as (negative) emotionality, sociability, and activity. High emotionality predicted increased BMI, independently of WC, and independently of childhood and adulthood risk factors for adult obesity. None of the temperament dimensions had any associations with WC after controlling for BMI. The findings suggest that temperamental difficulty in childhood may be a useful risk indicator for general body mass in adulthood, and the mechanisms relating temperament with body mass should be further explored. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
29.
ZnO-based varistor samples were prepared by the direct mixing of the constituent phases (DMCP) and sintering at 1100 °C for 2 h. The influence of the starting powder mixture's composition – the amounts of the pre-reacted varistor compounds and their composition – and its preparation, either with or without mechano-chemical activation (MCA), on the microstructure, phase composition and electrical characteristics of the varistor samples was studied. It showed that MCA improved the density and microstructural homogeneity of the varistor samples. MCA strongly affected the grain growth: it enhanced the nucleation of inversion boundaries (IBs) in the ZnO grains and the IBs-induced grain-growth mechanism resulted in uniform grain growth and hence a microstructure with smaller ZnO grains and a narrower grain size distribution. The final phase composition of the samples prepared by the DMCP method mainly depended on the presence of varistor dopants that can prevent the formation of the pyrochlore phase, especially Cr2O3, while MCA can affect it mostly by providing a homogeneous distribution of those dopants. The DMCP varistor samples prepared with MCA had much better current–voltage characteristics than the samples of the same composition prepared from unactivated powders. 相似文献
30.