全文获取类型
收费全文 | 3314篇 |
免费 | 67篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 60篇 |
综合类 | 1篇 |
化学工业 | 489篇 |
金属工艺 | 60篇 |
机械仪表 | 62篇 |
建筑科学 | 126篇 |
矿业工程 | 7篇 |
能源动力 | 53篇 |
轻工业 | 232篇 |
水利工程 | 36篇 |
石油天然气 | 1篇 |
无线电 | 336篇 |
一般工业技术 | 438篇 |
冶金工业 | 986篇 |
原子能技术 | 27篇 |
自动化技术 | 473篇 |
出版年
2021年 | 25篇 |
2020年 | 22篇 |
2019年 | 29篇 |
2018年 | 34篇 |
2017年 | 35篇 |
2016年 | 57篇 |
2015年 | 29篇 |
2014年 | 53篇 |
2013年 | 148篇 |
2012年 | 87篇 |
2011年 | 156篇 |
2010年 | 93篇 |
2009年 | 94篇 |
2008年 | 120篇 |
2007年 | 124篇 |
2006年 | 121篇 |
2005年 | 127篇 |
2004年 | 91篇 |
2003年 | 76篇 |
2002年 | 83篇 |
2001年 | 65篇 |
2000年 | 69篇 |
1999年 | 77篇 |
1998年 | 189篇 |
1997年 | 130篇 |
1996年 | 124篇 |
1995年 | 82篇 |
1994年 | 76篇 |
1993年 | 61篇 |
1992年 | 48篇 |
1991年 | 40篇 |
1990年 | 47篇 |
1989年 | 58篇 |
1988年 | 54篇 |
1987年 | 59篇 |
1986年 | 49篇 |
1985年 | 62篇 |
1984年 | 44篇 |
1983年 | 46篇 |
1982年 | 37篇 |
1981年 | 33篇 |
1980年 | 30篇 |
1979年 | 25篇 |
1978年 | 35篇 |
1977年 | 30篇 |
1976年 | 45篇 |
1975年 | 28篇 |
1974年 | 25篇 |
1973年 | 23篇 |
1971年 | 16篇 |
排序方式: 共有3387条查询结果,搜索用时 46 毫秒
1.
Journal of Materials Science - 相似文献
2.
Predicting Forest Age Classes from High Spatial Resolution Remotely Sensed Imagery Using Voronoi Polygon Aggregation 总被引:1,自引:0,他引:1
Efficient identification of forest age is useful for forest management and ecological applications. Here we propose a user-assisted method for determining forest age using high spatial resolution remotely sensed imagery. This method requires individual trees to be extracted from imagery and represented as points. We use a local maximum filter to generate points that are converted to Voronoi polygons. Properties of the Voronoi polygons are correlated with forest age and used to aggregate points (trees) into areas (stands) based on three forest age classes. Accuracy of the aggregation ranges from approximately 68% to 78% and identification of the mature class is more consistent and accurate than the younger classes. 相似文献
3.
Ching-Te Chuang Bernstein K. Joshi R.V. Puri R. Kim K. Nowak E.J. Ludwig T. Aller I. 《Circuits and Devices Magazine, IEEE》2004,20(1):6-19
The generation-over-generation scaling of critical CMOS technology parameters is ultimately bound by nonscalable limitations, such as the thermal voltage and the elementary electronic charge. Sustained improvement in performance and density has required the introduction of new device structures and materials. Partially depleted SOI, a most recent MOSFET innovation, has extended VLSI performance while introducing unique idiosyncrasies. Fully depleted SOI is one logical extension of this device design direction. Gate dielectric tunneling, device self-heating, and single-event upsets present developers of these next-generation devices with new challenges. Strained silicon and high-permittivity gate dielectric are examples of new materials that will enable CMOS developers to continue to deliver device performance enhancements in the sub-100 nm regime. 相似文献
4.
5.
6.
The mechanical fracture strength and toughness of short-fibre composites, injection moulded from compounds of poly(ethylene terephthalate) (PET) containing 10 and 30% (by weight) (w/o) glass, have been investigated and the dependence upon matrix hydrolytic stability determined. Mouldings have been characterised by several physical techniques to evaluate molecular weight, degradation rates, crystallinity and morphology, whilst time-dependent gravimetric data were derived to quantify sorption kinetics and allow comparisons with theoretical reaction rates to be made. During melt processing, PET is hydrolysed extremely rapidly by traces of moisture (<0.02w/o). yet the inherent strength of moulded composites declines significantly only below an apparently critical molecular weight. However, on long-term humid ageing in hot water, impact behaviour especially is rendered more complex by simultaneous crystallisation, molecular reorder and losses of interfacial bond strength. 相似文献
7.
W. S. Walston I. M. Bernstein A. W. Thompson 《Metallurgical and Materials Transactions A》1991,22(6):1443-1451
The microstructure of a single-crystal nickel-base superalloy, PWA 1480, has been varied by heat treatment and hot isostatic
pressing in order to study the role of the γ/yγ′ eutectic and porosity on subsequent tensile behavior. The level of porosity
was found not to affect any of the tensile properties, while the γ/γ′ eutectic strongly influenced ductility. Eliminating
the γ/γ′ eutectic increased ductility which was attributed to the cleavage fracture of this constituent. It is proposed that
such cleavage of the γ/γ′ eutectic is initiated by the stress created from impinging slip bands, promoting shear localization,
and final fracture along {111} slip planes. The precise nature of this fracture process is discussed with emphasis on the
role of the γ/′ micro-structure. The deformation structure of PWA 1480 was also studied, and while different in some respects
from many other single-crystal superalloys, its fracture process appears to be similar.
Formerly Graduate Student, Department of Metallurgical Engineering and Materials Science, Carnegie Mellon University. 相似文献
8.
9.
We present a new algorithm,
called MCS-M,
for computing minimal triangulations of graphs.
Lex-BFS, a seminal algorithm for recognizing chordal graphs,
was the genesis for two other classical algorithms:
LEX M and MCS.
LEX M extends the fundamental concept used in Lex-BFS,
resulting in an algorithm that not only recognizes chordality,
but also computes a minimal triangulation of an arbitrary graph.
MCS simplifies the fundamental concept used in Lex-BFS,
resulting in a simpler algorithm for recognizing chordal graphs.
The new algorithm MCS-M combines
the extension of LEX M with the simplification of MCS,
achieving all the results of LEX M in the same time complexity. 相似文献
10.
Formaldehyde is used in ruminant feeding for different purposes including the protection of dietary proteins from ruminal degradation. The formaldehyde content of milk of goats fed various levels of formaldehyde-treated soybean oil-meal has been determined by using a sensitive HPLC method. Results showed a significant linear correlation between ingested formaldehyde and formaldehyde concentration in milk. About 0.02% of ingested formaldehyde was excreted in milk, as free formaldehyde. 相似文献