全文获取类型
收费全文 | 250496篇 |
免费 | 1702篇 |
国内免费 | 270篇 |
专业分类
电工技术 | 4061篇 |
综合类 | 91篇 |
化学工业 | 40605篇 |
金属工艺 | 15216篇 |
机械仪表 | 10085篇 |
建筑科学 | 4196篇 |
矿业工程 | 3759篇 |
能源动力 | 3936篇 |
轻工业 | 9730篇 |
水利工程 | 4092篇 |
石油天然气 | 13013篇 |
武器工业 | 28篇 |
无线电 | 20409篇 |
一般工业技术 | 63072篇 |
冶金工业 | 32401篇 |
原子能技术 | 11141篇 |
自动化技术 | 16633篇 |
出版年
2021年 | 2787篇 |
2019年 | 2761篇 |
2018年 | 5475篇 |
2017年 | 5738篇 |
2016年 | 6085篇 |
2015年 | 3083篇 |
2014年 | 5349篇 |
2013年 | 10178篇 |
2012年 | 7362篇 |
2011年 | 9006篇 |
2010年 | 7341篇 |
2009年 | 8162篇 |
2008年 | 8245篇 |
2007年 | 7933篇 |
2006年 | 6401篇 |
2005年 | 5602篇 |
2004年 | 5505篇 |
2003年 | 5324篇 |
2002年 | 5159篇 |
2001年 | 4963篇 |
2000年 | 4958篇 |
1999年 | 4284篇 |
1998年 | 7230篇 |
1997年 | 5885篇 |
1996年 | 4461篇 |
1995年 | 3684篇 |
1994年 | 3459篇 |
1993年 | 3653篇 |
1992年 | 3228篇 |
1991年 | 3380篇 |
1990年 | 3498篇 |
1989年 | 3381篇 |
1988年 | 3286篇 |
1987年 | 3276篇 |
1986年 | 3170篇 |
1985年 | 3336篇 |
1984年 | 3271篇 |
1983年 | 3158篇 |
1982年 | 3005篇 |
1981年 | 3061篇 |
1980年 | 3088篇 |
1979年 | 3266篇 |
1978年 | 3503篇 |
1977年 | 3471篇 |
1976年 | 3927篇 |
1975年 | 3213篇 |
1974年 | 3303篇 |
1973年 | 3343篇 |
1972年 | 2989篇 |
1971年 | 2756篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
The Metaflow architecture, a unified approach to maximizing the performance of superscalar microprocessors, is introduced. The Metaflow architecture exploits inherent instruction-level parallelism in conventional sequential programs by hardware means, without relying on optimizing compilers. It is based on a unified structure, the DRIS (deferred-scheduling, register-renaming instruction shelf), that manages out-of-order execution and most of the attendant problems. Coupling the DRIS with a speculative-execution mechanism that avoids conditional branch stalls results in performance limited only be inherent instruction-level parallelism and available execution resources. Although presented in the context of superscalar machines, the technique is equally applicable to a superpipelined implementation. Lightning, the first implementation of the Metaflow architecture, which executes the Sparc RISC instruction set is described 相似文献
132.
V. Kasyanov 《Theoretical computer science》1991,90(1):37-46
This paper focuses on the problem of program concretization by applying correctness-preserving transformations of annotated programs. According to the approach presented, a general-purpose program can be annotated by known information about a specific context of its applications and correctly transformed into a specialized program which is equivalent to the original one on the context-defined ranges of inputs and outputs and is better than it by quality criteria given by the context. Tools for program concretizations via annotated program transformations are considered. 相似文献
133.
134.
135.
Ion-beam sputter-deposited alloy films of Co/sub 74/Fe/sub 6/B/sub 15/Si/sub 5/ and Fe/sub 75/Ni/sub 5/B/sub 15/Si/sub 5/ were examined for their magnetic and structural properties. Films were characterized by ferromagnetic resonance, vibrating sample magnetometry, and extended X-ray absorption fine structure (EXAFS) analysis. Using atomic parameters deduced from EXAFS modeling and fitting procedures, magnetic properties were calculated with no adjustable parameters. Correlation between perpendicular FMR measurements and EXAFS first-shell modeling suggests a low-temperature formation of cobalt-borides in the Co/sub 74/Fe/sub 6/B/sub 15/Si/sub 5/ alloy. Annealed Fe/sub 75/Ni/sub 5/B/sub 15/Si/sub 5/ samples did not display evidence of structural and/or magnetic instabilities until the onset of long-range crystallization near T/sub ann/=400 degrees C.<> 相似文献
136.
I. S. Panidi V. A. Trofimov N. S. Lepikhina 《Chemistry and Technology of Fuels and Oils》2006,42(6):440-445
Equations are proposed for calculating the molar volume of liquid hydrocarbons used in production of surfactants. With such
data, it will be possible to calculate most of the physicochemical properties of these hydrocarbons to solve many process
problems.
__________
Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 6, pp. 39–41, Novemmber–December, 2006. 相似文献
137.
Velocity profiles for the inner and outer flow regions of annuli are proposed for the turbulent flow of drag reducing fluids. Theoretical expressions for friction factors are developed. From the shear stress equations and the velocity profiles, estimates for the entrance lengths are given. 相似文献
138.
139.
The manifestation of elastic effects during the filtration of polymer solutions is analyzed theoretically.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 3, pp. 390–397, September, 1985. 相似文献
140.
C. A. Pineda P. Wenzl J. Mayer J. Mesjasz-Przybylowicz W. J. Przybylowicz V. M. Prozesky 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》1997,130(1-4):362-367
A Brachiaria breeding project is being conducted at CIAT, Colombia to combine acid soil adaptation of B. decumbens with other favourable traits of Brachiaria species that are less adapted to acid soils. Micro-PIXE was applied to investigate nutrient uptake and distribution in root tips of different species grown in hydroponic culture under control and simulated acid soil stress conditions. Different sample measurement approaches were evaluated, including: (1) linear scans with single point measurements along the root axis; (2) mapping of whole root tips; and (3) mapping of root cross sections. Different tissue types could be distinguished on the base of differences in nutrient concentrations and/or Al stress. Al, if supplied under nutrient stress conditions, increased P accumulation in the central vascular tissue of the meristematic and elongation zone of B. decumbens and B. brizantha. Furthermore, a negative correlation was found between Al and Cl accumulation in the root cap of B. decumbens. 相似文献