全文获取类型
收费全文 | 20580篇 |
免费 | 1613篇 |
国内免费 | 772篇 |
专业分类
电工技术 | 333篇 |
技术理论 | 1篇 |
综合类 | 956篇 |
化学工业 | 10076篇 |
金属工艺 | 341篇 |
机械仪表 | 332篇 |
建筑科学 | 929篇 |
矿业工程 | 135篇 |
能源动力 | 463篇 |
轻工业 | 643篇 |
水利工程 | 69篇 |
石油天然气 | 2176篇 |
武器工业 | 243篇 |
无线电 | 1557篇 |
一般工业技术 | 4156篇 |
冶金工业 | 255篇 |
原子能技术 | 70篇 |
自动化技术 | 230篇 |
出版年
2024年 | 99篇 |
2023年 | 327篇 |
2022年 | 324篇 |
2021年 | 506篇 |
2020年 | 552篇 |
2019年 | 560篇 |
2018年 | 504篇 |
2017年 | 681篇 |
2016年 | 677篇 |
2015年 | 668篇 |
2014年 | 1023篇 |
2013年 | 1139篇 |
2012年 | 1265篇 |
2011年 | 1431篇 |
2010年 | 1056篇 |
2009年 | 1122篇 |
2008年 | 1004篇 |
2007年 | 1284篇 |
2006年 | 1338篇 |
2005年 | 1055篇 |
2004年 | 943篇 |
2003年 | 872篇 |
2002年 | 790篇 |
2001年 | 708篇 |
2000年 | 577篇 |
1999年 | 487篇 |
1998年 | 445篇 |
1997年 | 300篇 |
1996年 | 213篇 |
1995年 | 169篇 |
1994年 | 180篇 |
1993年 | 152篇 |
1992年 | 117篇 |
1991年 | 87篇 |
1990年 | 42篇 |
1989年 | 36篇 |
1988年 | 31篇 |
1987年 | 20篇 |
1986年 | 20篇 |
1985年 | 51篇 |
1984年 | 41篇 |
1983年 | 31篇 |
1982年 | 28篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Paul J. Flory 《Polymer International》1985,17(2):96-102
The earliest investigations on rubber elasticity, commencing in the 19th century, were necessarily limited to phenomenological interpretations. The realisation that polymers consist of very long molecular chains. commencing c. 1930, gave impetus to the molecular theory of rubber elasticity (1932-). according to which the high deformability of an elastomer, and the elastic force generated by deformation, stem from the configurations accessible to long molecular chains. Theories of rubber elasticity put forward from 1934-1946 relied on the assumption that the junctions of the rubber network undergo displacements that are affine in macroscopic strain. The theory of James and Guth (1947) dispensed with this premise, and demonstrated instead that the mean positions of the junctions of a ‘phantom’ network consisting of Gaussian chains devoid of material properties are affine in the strain. The vital significance of the distinction between the actual distribution of chain vectors in a network and their distribution if the junctions would be fixed at their mean positions went unnoticed for nearly 30 years. Experimental investigations, commencing with the incisive work of Gee in 1946. revealed large departures from the relationship of stress to strain predicted by the theories cited. This discrepancy prompted extensive studies, theoretical and experimental, during succeeding years. Inquiry into the fundamentals of polymer networks, formed for example by interlinking very long polymer molecules, exposed the need to take account of network imperfections, typically consisting of chains attached at only one end to a network junction. Various means were advocated to make corrections for these imperfections. The cycle rank ζ of the network has been shown (1976) to be the fundamental measure of its connectivity, regardless of the junction functionality and pattern of imperfections. Often overlooked is the copious interpenetration of the chains comprising typical elastomeric networks. Theories that attempt to represent such networks on a lattice are incompatible with this universal feature. Moreover, the dense interpenetration of chains may limit the ability of junctions in real networks to accommodate the fluctuations envisaged in the theory of phantom networks. It was suggested in 1975 that departures from the form predicted for the elastic equation of state are due to constraints on the fluctuations of junctions whose effect diminishes with deformation and with dilation. Formulation of a self-consistent theory based on this suggestion required recognition of the non-affine connection between the chain vector distribution function and the macroscopic strain in a real network, which may partake of characteristics of a phantom network in some degree. Implementation of the idea was achieved through postulation of domains of constraint affecting the equilibrium distribution of fluctuations of network junctions from their mean positions. This led in due course to a theory that accounts for the relationship of stress to strain virtually throughout the ranges of strain accessible to measurement. The theory establishes connections between structure and elastic properties. This is achieved with utmost frugality in arbitrary parameters. 相似文献
12.
13.
Jiang Minhong Gu Zhengfei Cheng Gang 《中国稀土学报(英文版)》2005,23(6):723-723
Polymer matrix RE-Fe giant magnetostrictire composite (GMPC) was prepared using bonding and magnetic field forming technique, and magnetostriction of samples was measured for different compressive stress. The experimental results show thai there is certain compressive effect in GMPC. And the influence of compressive stress on magnetostriction of sample was investigated. It offers essential reference for application and device design of GMPC. 相似文献
14.
15.
注聚采出水分离用动态水力旋流器特性研究 总被引:6,自引:1,他引:5
原有的地面工艺和设备已不能满足聚合物驱采出水分离的要求。采用自行研制的动态水力旋流器,在增压与不增压两种工艺流程下,分别进行了流量和转数对分离效率的影响、转数与压力降的关系,以及入口压力与处理量的关系等项试验研究。试验结果表明,与静态水力旋流器相比,动态水力旋流器的分离效率明显提高,一般可提高10%左右;压力损失显著降低,约可减少0.1MPa,足见可在低压下工作,易于实现无泵运行;无泵运行明显比有泵增压运行的分离效率高,但处理量会有所降低。将动态水力旋流器应用于聚合物驱产出水的油-水分离处理是完全可行的。 相似文献
16.
二元复合驱采出液矿场处理试验 总被引:1,自引:0,他引:1
利用研制的二元复合驱采出液矿场处理装置,对辽河油田兴28块兴191井采出液进行了矿场处理试验。结果表明,采用适宜的破乳剂及处理工艺技术,可以使矿场采出液处理达到净化油含水≤0.5%的指标。 相似文献
17.
18.
研究了HIPS/PC共混物的相容性及HIPS-MA对HIPS(30)/PC(70)共混物的相容性、形态和拉伸性能的影响。DSC研究结果表明,HIPS/PC共混物中PS的玻璃化转变温度(Tg)不随组成而变化,而PC的Tg随其质量分数的降低逐渐向低温移动,说明HIPS/PC是部分相容体系。通过DSC、扫描电镜形态观察和拉伸性能测试结果发现,当HIPS-g-MA的含量低于7.5%时,共混物的相容性改善不明显,当其含量达到7.5%时,对共混物有明显的乳化作用,说明饱和的界面浓度在7.5%左右。HIPS-g-MA接枝共聚物在HIPS(30)/PC(70)共混物中的增容作用可能是酯交换反应原位生成的嵌段共聚物所致。 相似文献
19.
90年代以来,国外钻井液和完井液用聚合物添加剂的发展取得长足进步。本文介绍了国外目前用于钻井液和完井液的聚合物添加剂的类型及作用。 相似文献
20.
氮化硅的性能及其聚合物材料 总被引:1,自引:0,他引:1
陈继兰 《高分子材料科学与工程》1996,12(6):144-147
叙述了氮化硅(Si3N4)的性能并制备了含Si3N4的聚合物材料,这种材料在医学上具有重要价值,对改变医学方面的概念、和对促进人类健康长寿具有重要意义。 相似文献