全文获取类型
收费全文 | 1242篇 |
免费 | 35篇 |
国内免费 | 28篇 |
专业分类
电工技术 | 24篇 |
综合类 | 78篇 |
化学工业 | 74篇 |
金属工艺 | 135篇 |
机械仪表 | 305篇 |
建筑科学 | 34篇 |
矿业工程 | 19篇 |
能源动力 | 260篇 |
轻工业 | 30篇 |
水利工程 | 9篇 |
石油天然气 | 16篇 |
武器工业 | 10篇 |
无线电 | 69篇 |
一般工业技术 | 109篇 |
冶金工业 | 25篇 |
原子能技术 | 3篇 |
自动化技术 | 105篇 |
出版年
2024年 | 1篇 |
2023年 | 16篇 |
2022年 | 7篇 |
2021年 | 13篇 |
2020年 | 22篇 |
2019年 | 8篇 |
2018年 | 17篇 |
2017年 | 22篇 |
2016年 | 27篇 |
2015年 | 19篇 |
2014年 | 62篇 |
2013年 | 66篇 |
2012年 | 88篇 |
2011年 | 98篇 |
2010年 | 42篇 |
2009年 | 41篇 |
2008年 | 40篇 |
2007年 | 77篇 |
2006年 | 79篇 |
2005年 | 71篇 |
2004年 | 81篇 |
2003年 | 55篇 |
2002年 | 48篇 |
2001年 | 37篇 |
2000年 | 28篇 |
1999年 | 42篇 |
1998年 | 28篇 |
1997年 | 32篇 |
1996年 | 22篇 |
1995年 | 17篇 |
1994年 | 18篇 |
1993年 | 14篇 |
1992年 | 9篇 |
1991年 | 11篇 |
1990年 | 8篇 |
1989年 | 12篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1976年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有1305条查询结果,搜索用时 15 毫秒
1.
《Ceramics International》2021,47(23):32963-32968
Effects of carbon source in single-source ZrC-based liquid precursors on the properties of the precursors and precursor-derived nano ZrC powders were investigated. The liquid precursors were prepared by directly blending and heating zirconium n-butoxide with either 2,4-pentanedione, benzoyl acetone or 1,3-diphenyl-1,3-propanedione additives which have the same chemical composition and structure except for the number of benzene rings (0, 1 and 2, respectively) in order to control the carbon content in the precursors. The ceramic yield of the precursor decreased as the number of benzene rings in the precursors increased. The stability of the precursors in air and the carbon content of the ceramic powder increased when using 1,3-diphenyl-1,3-propanedione additive. X-ray pure nano zirconium carbide powders with ultra-fine size (30 nm), isotropic shape and homogeneous particle size distribution were synthesized from the liquid precursors containing two benzene rings in the structure. Compared with ZrC powders derived from the precursors containing zero or one benzene ring, the powder from the precursor containing two benzene rings was finer and more homogeneous in size distribution. 相似文献
2.
Leakage flow rate is one of the most important contributions to the measurement uncertainty when measuring small gas flow rates with a clearance-sealed piston prover. Our previous study has shown that the systematic effects related to the change of the gas viscosity can be successfully corrected, whereas the effects related to the reproducibility of the leakage flow rate are poorly understood. This paper focuses on the interpretation and correction of the reproducibility related effects by analysing experimentally identified variations of the leakage flow rate and the gas pressure in the inclined piston prover. Small changes of the leakage flow in the inclined piston prover indicate that the position of the piston relative to the cylinder remains approximately the same. The obtained relationship between the leakage flow rate and the gas pressure below the piston led to the pressure-based correction of the leakage flow rate. 相似文献
3.
Kenichiro Masaoka Fu Jiang Mark D. Fairchild Rodney L. Heckaman 《Journal of the Society for Information Display》2020,28(3):273-286
There are claims that multi‐chromatic displays can achieve a wider color gamut by the use of additional highly saturated secondary color channels. However, there are other claims that these displays lose lightness and/or color saturation at brighter levels. These apparently divergent views have led to some controversy in the display industry and at standard setting organizations. This study examines the color gamut volume for a variety of simulated and measured multi‐chromatic (sometimes incorrectly referred to as “multi‐primary”) displays using combinations of white and/or secondary color channels, such as cyan, magenta, and yellow. Furthermore, a two‐dimensional gamut representation, referred to as “gamut rings,” is introduced to illustrate that the addition of nonprimary optical color channels to a trichromatic (RGB) display can result in a significant decrease in the chroma at higher lightness levels. The additional saturated color channels can increase the gamut volume only around their hues at darker levels. The results also confirm the validity of comparing the color light output and white light output for revealing the design trade‐offs between the high‐peak white and the color‐image brightness for multi‐chromatic displays. 相似文献
4.
在开展结冰试验时,结冰风洞风扇叶片前缘有结冰风险,影响风洞安全运行。针对大型旋转叶片结冰问题,提出了旋转叶片电加热防冰系统设计方法,研制了大型结冰风洞旋转叶片电加热防冰系统。首先,研制了内置电加热单元和温度反馈的防冰叶片。针对叶片复杂的工作环境,提出一种新的旋转叶片电加热防冰功率计算方法,通过精确测量和方案优化,设计了基于特殊环境的分半式、大尺寸、高线速度、碳刷自动移开/压紧的导电滑环。最后,采用变结构分级温度闭环和试验参数连锁防冰控制策略解决了旋转叶片结冰问题。该系统已应用于大型结冰风洞,运行中加热电流和叶片温度反馈信号传输连续,所有旋转叶片前缘快速加热且温度分布均匀,防冰效果好。 相似文献
5.
《Journal of Industrial and Engineering Chemistry》2014,20(2):372-378
A series of new bis (imidazolium) cation-based ionic liquids, wherein two imidazole rings are tethered by alkyl ether chains (oxygen numbers) of different lengths, were prepared, and their coal dissolution and dispersion properties were studied. It was found these ionic liquids can be used to fragment, disperse, and partially dissolve micrometer-size coal particles by simply mixing ionic liquid/coal dispersions. Dissolution performances and light hydrocarbon production were found to be sensitively increased by increasing the lengths of alkyl ether chains between imidazolium rings. 相似文献
6.
为提高消防车发动机活塞的耐磨性,延长其使用寿命,通过采用脉冲电源放电的方法,对普通汽车发动机活塞(ZL108)基体进行了微弧氧化处理,并对获得涂层的耐磨性进行了分析,给出了活塞装车运行的试验结果.这些结果表明:本试验为微弧氧化技术在消防车发动机活塞上的应用提供了理论依据及实践经验,具有很大的可行性. 相似文献
7.
8.
AbstractCryptographic attacks are typically constructed by black-box methods and combinations of simpler properties, for example in [Generalised] Linear Cryptanalysis. In this article, we work with a more recent white-box algebraic-constructive methodology. Polynomial invariant attacks on a block cipher are constructed explicitly through the study of the space of Boolean polynomials which does not have a unique factorisation and solving the so-called Fundamental Equation (FE). Some recent invariant attacks are quite symmetric and exhibit some sort of clear structure, or work only when the Boolean function is degenerate. As a proof of concept, we construct an attack where a highly irregular product of seven polynomials is an invariant for any number of rounds for T-310 under certain conditions on the long term key and for any key and any IV. A key feature of our attack is that it works for any Boolean function which satisfies a specific annihilation property. We evaluate very precisely the probability that our attack works when the Boolean function is chosen uniformly at random. 相似文献
9.
10.
Ü. Kotta 《International journal of control》2017,90(9):1951-1956
In this paper, the realisation problem of linear multi-input multi-output, time-varying systems is studied. The approach, based on the theory of non-commutative polynomial rings, yields explicit and simple formulas for computation of the state coordinates as well as for state equations in observable canonical form. The formulas are based on (left) Euclidean polynomial division. 相似文献