全文获取类型
收费全文 | 495768篇 |
免费 | 49109篇 |
国内免费 | 22418篇 |
专业分类
电工技术 | 30362篇 |
技术理论 | 48篇 |
综合类 | 35190篇 |
化学工业 | 88564篇 |
金属工艺 | 28087篇 |
机械仪表 | 30579篇 |
建筑科学 | 36975篇 |
矿业工程 | 15046篇 |
能源动力 | 13534篇 |
轻工业 | 38604篇 |
水利工程 | 9891篇 |
石油天然气 | 28193篇 |
武器工业 | 4207篇 |
无线电 | 56029篇 |
一般工业技术 | 58451篇 |
冶金工业 | 23890篇 |
原子能技术 | 4973篇 |
自动化技术 | 64672篇 |
出版年
2024年 | 1830篇 |
2023年 | 6620篇 |
2022年 | 12407篇 |
2021年 | 17545篇 |
2020年 | 14185篇 |
2019年 | 13096篇 |
2018年 | 14740篇 |
2017年 | 16688篇 |
2016年 | 16046篇 |
2015年 | 21296篇 |
2014年 | 26101篇 |
2013年 | 31617篇 |
2012年 | 33047篇 |
2011年 | 35700篇 |
2010年 | 32776篇 |
2009年 | 31230篇 |
2008年 | 30626篇 |
2007年 | 29323篇 |
2006年 | 28737篇 |
2005年 | 24901篇 |
2004年 | 17767篇 |
2003年 | 15699篇 |
2002年 | 14905篇 |
2001年 | 13227篇 |
2000年 | 12035篇 |
1999年 | 11302篇 |
1998年 | 8083篇 |
1997年 | 6959篇 |
1996年 | 6472篇 |
1995年 | 5315篇 |
1994年 | 4364篇 |
1993年 | 2926篇 |
1992年 | 2308篇 |
1991年 | 1745篇 |
1990年 | 1370篇 |
1989年 | 1117篇 |
1988年 | 905篇 |
1987年 | 586篇 |
1986年 | 454篇 |
1985年 | 271篇 |
1984年 | 223篇 |
1983年 | 182篇 |
1982年 | 141篇 |
1981年 | 91篇 |
1980年 | 108篇 |
1979年 | 50篇 |
1978年 | 21篇 |
1977年 | 26篇 |
1976年 | 29篇 |
1959年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
43.
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
44.
45.
Reducing the complexity of distance measurement methods for circular turbo codes that use structured interleavers 下载免费PDF全文
Youssouf Ould‐Cheikh‐Mouhamedou 《International Journal of Communication Systems》2015,28(9):1572-1579
The knowledge of turbo code's minimum Hamming distance (dmin) and its corresponding codeword multiplicity (Amin) is of a great importance because the error correction capability of a code is strongly tied to the values of dmin and Amin. Unfortunately, the computational complexity associated with the search for dmin and Amin can be very high, especially for a turbo code that has high dmin value. This paper introduces some useful properties of turbo codes that use structured interleavers together with circular encoding. These properties allow for a significant reduction of search space and thus reduce significantly the computational complexity associated with the determination of dmin and Amin values. © 2014 The Authors. International Journal of Communication Systems published by John Wiley & Sons, Ltd. 相似文献
46.
Xiao-Guang Yue Guang Zhang Qu Wu Fei Li Xian-Feng Chen Gao-Feng Ren Mei Li 《稀有金属(英文版)》2015,(2):125-132
In order to predict the wearing of stellite alloys,the related methods of rare metals data processing were discussed. The method of opposite degree(OD) algorithm was put forward to predict the wearing of stellite alloys.OD algorithm is based on prior numerical data, posterior numerical data and the opposite degree between numerical forecast data. To compare the performance of predicted results based on different algorithms, the back propagation(BP) and radial basis function(RBF) neural network methods were introduced. Predicted results show that the relative error of OD algorithm is smaller than those of BP and RBF neural network methods. OD algorithm is an effective method to predict the wearing of stellite alloys and it can be applied in practice. 相似文献
47.
新汶矿业集团经过探索和实践,研究运用了差异互补式全掩护支护技术、掩护支架自牵引联动装置工艺、矿车运输、滑移运输多用轨道、自动找正装车平台、液控调整装置等新技术、新工艺,做到了液压支架综合流程快速回撤,实现了高效化、连贯化安全回撤,取得了良好的经济效益。 相似文献
48.
Lecture capture with real‐time rearrangement of visual elements: impact on student performance 下载免费PDF全文
The primary goal of this study is to create and test a lecture‐capture system that can rearrange visual elements while recording is still taking place, in such a way that student performance can be positively influenced. The system we have devised is capable of integrating and rearranging multimedia sources, including learning content, the instructor and students' images, into lecture videos that are embedded in a website for students to review after school. The present study employed a two‐group experimental design, with 153 participants (145 females and 8 males) making up an experimental group in which lecture courses were recorded using the new lecture‐capture system, and 149 participants (140 females and 9 males) forming a control group whose lectures were recorded by traditional means. All participants were in the freshman college and studying Introduction to Computer and Information Science in one of six classes, and were randomly assigned to one of the two groups. The participants' midterm examination and final examination scores were collected as indicators of their academic performance, with their mathematics entrance scores used as a pre‐test. The findings obtained from analysis of covariance (ANCOVA) suggest that appropriate rearrangement of visual elements in lecture videos can significantly impact students' learning performance. 相似文献
49.
50.
Correlation between instrumental texture and colour quality attributes with sensory analysis of selected cheeses as affected by fat contents 下载免费PDF全文
A. Półtorak J. Wyrwisz M. Moczkowska M. Marcinkowska‐Lesiak A. Stelmasiak U. Ulanicka M. Zalewska A. Wierzbicka Da‐Wen Sun 《International Journal of Food Science & Technology》2015,50(4):999-1008
This study evaluated several physical and sensory parameters of different types of cheese available in the Polish market. The measurements of textural properties were conducted in an Instron universal testing machine, while the colour properties of cheeses were measured using a Minolta chromameter. The chemical composition was determined by means of the near‐infrared spectroscopy (NIRs). Moreover, a trained sensory panel was invited to assess the cheese texture‐related properties. Generally, cheeses with reduced fat content were characterised by higher hardness, adhesiveness, cohesiveness and elasticity. Texture‐related parameters of cheese with canola oil were comparable to that of most of full‐fat cheeses. The correlation analysis between physical and sensory attributes related to cheese textural properties indicated the potential applications of TPA, shear and penetration tests (r = 0.766, r = 0.75 and r = 0.765, respectively) for the evaluation of sensory properties related to the hardness. Meanwhile, the elasticity of cheese obtained from sensory evaluation was strongly correlated with the elasticity determined from the shear test (r = 0.722) and moderately correlated with the elasticity from penetration test (r = 0.588), indicating a need to refine the method of penetration test. In addition, cheeses exhibited higher meltability during convection heating at 230 °C than microwave heating. The values of meltability for cheese with reduced fat content were lower than those of full‐fat cheese. 相似文献