全文获取类型
收费全文 | 11933篇 |
免费 | 1731篇 |
国内免费 | 957篇 |
专业分类
电工技术 | 1116篇 |
综合类 | 1330篇 |
化学工业 | 2258篇 |
金属工艺 | 352篇 |
机械仪表 | 714篇 |
建筑科学 | 754篇 |
矿业工程 | 424篇 |
能源动力 | 343篇 |
轻工业 | 1634篇 |
水利工程 | 428篇 |
石油天然气 | 518篇 |
武器工业 | 185篇 |
无线电 | 681篇 |
一般工业技术 | 986篇 |
冶金工业 | 370篇 |
原子能技术 | 99篇 |
自动化技术 | 2429篇 |
出版年
2024年 | 96篇 |
2023年 | 212篇 |
2022年 | 435篇 |
2021年 | 446篇 |
2020年 | 498篇 |
2019年 | 414篇 |
2018年 | 432篇 |
2017年 | 472篇 |
2016年 | 525篇 |
2015年 | 500篇 |
2014年 | 756篇 |
2013年 | 780篇 |
2012年 | 974篇 |
2011年 | 946篇 |
2010年 | 717篇 |
2009年 | 675篇 |
2008年 | 614篇 |
2007年 | 790篇 |
2006年 | 661篇 |
2005年 | 560篇 |
2004年 | 476篇 |
2003年 | 400篇 |
2002年 | 319篇 |
2001年 | 336篇 |
2000年 | 253篇 |
1999年 | 228篇 |
1998年 | 200篇 |
1997年 | 157篇 |
1996年 | 131篇 |
1995年 | 105篇 |
1994年 | 98篇 |
1993年 | 81篇 |
1992年 | 56篇 |
1991年 | 63篇 |
1990年 | 39篇 |
1989年 | 27篇 |
1988年 | 28篇 |
1987年 | 19篇 |
1986年 | 17篇 |
1985年 | 17篇 |
1984年 | 16篇 |
1983年 | 13篇 |
1982年 | 19篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1976年 | 3篇 |
1973年 | 2篇 |
1964年 | 3篇 |
1957年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
复杂不规则刚体转动惯量的测试原理和方法 总被引:6,自引:0,他引:6
为了测量复杂不规则刚体转动惯量,采用时间常数法,通过A/D卡PS2129的定时/计数器8253高精度测速、计时,能较好地应用于测量转动惯量。 相似文献
32.
A generalized equation was derived to calculate the melting temperatures of homopolymers and copolymers. The Gibbs‐Thomson equation for homopolymers and a modified application to copolymers were derived using the proposed equation. The melting temperature Tm0 in the Flory equation corresponds to the melting temperature TmC,∞ of copolymer crystals with stems of infinite length. Also, TmC,n*, the melting temperature for copolymer crystals with stems containing the maximum possible number of structural units, n*, should be used instead of Tm0 as the basis of supercooling in crystallization. The proposed equation shows good agreement with experimental data for α‐alkene‐ethylene homogeneous copolymers. 相似文献
33.
This paper deals with the non-steady-state kinetics of direct thermal initiated polymerization. The initiation is assumed to be a bimolecular reaction of the monomer. The relationship between the radical concentration and the monomer conversion is rigorously derived. In further treatment a few very close approximations are introduced based on the fact that the number of monomer molecules reacting in the initiation step is much less than that consumed in the propagation step for a process producing high polymer, and the value of the rate constant for propagation or chain transfer is much lower than that for chain termination. Expressions for various molecular parameters, such as molecular weight distribution, number-average and weight-average degrees of polymerization, and dispersity, are given. Several numerical examples are provided. 相似文献
34.
分子结构对增塑聚氯乙烯性能的影响 总被引:2,自引:0,他引:2
研究了聚合度、分子量分布和支化结构对增塑聚氯乙烯加工流变性能和物理力学性能的影响。结果表明,增塑PVC的加工流变性能随聚合度的增加而恶化;拓宽分子量分布和引入支化结构均有利于加工流变性能的提高;增塑PVC的拉伸强度随聚合度的增加而提高,而压缩永久变形却随之减小;分子量分布对物理力学性能的影响不大;支化PVC的拉伸强度略有下降。 相似文献
35.
36.
Yu. S. Gorbunov A. G. Ageev R. V. Vasil’eva B. M. Korol’kov 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2007,41(3):166-170
A system for the direct measurement of steam flow in steam lines after a steam generator, which utilizes a special design
of pneumometric tubes and a computing unit that accounts for variation in steam pressure, has been developed to improve the
quality of water-level regulation in the steam generators of VVéR-1000 power-generating units in the stationary and transitional
modes. The advantage of the pneumometric tubes consists in their structural simplicity, high erosion resistance, and absence
of irrevocable losses during measurement of steam flow. A similar measurement system is used at foreign NPP. The measurement
system in question has been placed in experimental service at the No. 3 unit of the Balakovo NPP, and has demonstrated its
worthiness. This measurement system can also be used to determine steam flow in the steam lines of NPP units with VVéR-1000
and VVéR-440 reactors, and PBMK-1000 power-generating units.
__________
Translated from élektricheskie Stantsii, No. 3, March 2007, pp. 23–26. 相似文献
37.
Polyurethanes were prepared from pure 4,4′-diphenylmethane diisocyanate (MDI), 1,4-butane diol (BDO) or 1,2-ethane diol (EDO) and α,ω-hydroxyl poly(propylene oxide) (PPO) by reaction injection moulding (RIM). Hard segment (MDI + BDO or EDO) level was 45–50 wt%. The PPO had about 20% ethylene oxide copolymerized in at the chain ends to provide 80% primary OH end groups. Mn was varied from 2000 to 4000. Dibutyl tin dilaurate catalyst and mould temperature were varied. Dynamic mechanical, wide-angle X-ray, differential scanning calorimeter, molecular weight and tensile elongation measurements were made on the RIM polyurethanes. At low reaction rates (low catalyst or temperature) highly crystalline, well phase separated but low molecular weight polymers were produced. At high catalyst or temperature levels more poorly phase separated but high molecular weight, tough polymers resulted. Higher Mn PPO gave better phase separation and EDO gave higher melting temperatures. Preventing hard segment crystallinity by substituting asymmetric MDI or glycols resulted in phase compatibility. 相似文献
38.
超高分子量聚乙烯衬板在煤仓中的应用 总被引:2,自引:0,他引:2
介绍了井底煤仓溜煤斜面采用超高分子量聚乙烯衬板安装及应用情况 ,对井底煤仓棚煤原因及解决办法进行了探讨 相似文献
39.
热带城市垃圾典型组分的热解特性研究 总被引:7,自引:0,他引:7
对热带城市垃圾的几种典型组分进行了热解实验,得到了它们的失重曲线,通过对失重曲线进行分析,得到了这几种典型组分的热解规律,并通过建立热解动力学模型,求出了其中两种组分的活化能E和频率因子A。 相似文献
40.