全文获取类型
收费全文 | 452353篇 |
免费 | 4978篇 |
国内免费 | 1311篇 |
专业分类
电工技术 | 7913篇 |
综合类 | 297篇 |
化学工业 | 70235篇 |
金属工艺 | 19927篇 |
机械仪表 | 14177篇 |
建筑科学 | 10180篇 |
矿业工程 | 3517篇 |
能源动力 | 10577篇 |
轻工业 | 36309篇 |
水利工程 | 5492篇 |
石油天然气 | 12609篇 |
武器工业 | 36篇 |
无线电 | 48920篇 |
一般工业技术 | 92715篇 |
冶金工业 | 79948篇 |
原子能技术 | 12116篇 |
自动化技术 | 33674篇 |
出版年
2021年 | 3796篇 |
2019年 | 3609篇 |
2018年 | 6586篇 |
2017年 | 6583篇 |
2016年 | 7076篇 |
2015年 | 4319篇 |
2014年 | 7277篇 |
2013年 | 19244篇 |
2012年 | 11443篇 |
2011年 | 15100篇 |
2010年 | 12262篇 |
2009年 | 13887篇 |
2008年 | 14234篇 |
2007年 | 14048篇 |
2006年 | 12273篇 |
2005年 | 11334篇 |
2004年 | 10503篇 |
2003年 | 10144篇 |
2002年 | 10069篇 |
2001年 | 10061篇 |
2000年 | 9543篇 |
1999年 | 9667篇 |
1998年 | 23504篇 |
1997年 | 17118篇 |
1996年 | 13218篇 |
1995年 | 10006篇 |
1994年 | 8848篇 |
1993年 | 8971篇 |
1992年 | 6854篇 |
1991年 | 6806篇 |
1990年 | 6514篇 |
1989年 | 6511篇 |
1988年 | 6438篇 |
1987年 | 5514篇 |
1986年 | 5580篇 |
1985年 | 6357篇 |
1984年 | 6026篇 |
1983年 | 5616篇 |
1982年 | 5215篇 |
1981年 | 5299篇 |
1980年 | 5205篇 |
1979年 | 5139篇 |
1978年 | 5251篇 |
1977年 | 5826篇 |
1976年 | 7277篇 |
1975年 | 4770篇 |
1974年 | 4536篇 |
1973年 | 4641篇 |
1972年 | 4056篇 |
1971年 | 3703篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
V. N. Tsygankov V. V. Safonov A. I. Kozlov V. P. Gavrilov 《Inorganic Materials》2003,39(10):1076-1078
The GeO2–NiO system is studied in the stability range of Ni2GeO4 by temperature-dependent resistivity measurements, in combination with x-ray diffraction, differential thermal analysis, and thermogravimetry. The resistivity of the starting mixtures and heat-treated samples is measured in the composition range 55–90 mol % NiO. The effect of air humidity on the resistivity of the samples is examined. 相似文献
33.
A cell vertex finite volume method for the solution of steady compressible turbulent flow problems on unstructured hybrid
meshes of tetrahedra, prisms, pyramids and hexahedra is described. These hybrid meshes are constructed by firstly discretising
the computational domain using tetrahedral elements and then by merging certain tetrahedra. A one equation turbulence model
is employed and the solution of the steady flow equations is obtained by explicit relaxation. The solution process is accelerated
by the addition of a multigrid method, in which the coarse meshes are generated by agglomeration, and by parallelisation.
The approach is shown to be effective for the simulation of a number of 3D flows of current practical interest.
Sponsored by The Research Council of Norway, project number 125676/410
Dedicated to the memory of Prof. Mike Crisfield, a respected colleague 相似文献
34.
In this letter, we introduce and investigate a new problem referred to as the All Hops Shortest Paths (AHSP) problem. The AHSP problem involves selecting, for all hop counts, the shortest paths from a given source to any other node in a network. We derive a tight lower bound on the worst-case computational complexities of the optimal comparison-based solutions to AHSP. 相似文献
35.
Open Shortest Path First (OSPF) traffic engineering (TE) is intended to bring long-awaited traffic management capabilities into IP networks, which still rely on today's prevailing routing protocols: OSPF or IS-IS. In OSPF, traffic is forwarded along, and split equally between, equal cost shortest paths. In this letter, we formulate the basic requirements placed on a practical TE architecture built on top of OSPF and present a theoretical framework meeting these requirements of practicality. The main contribution of our work comes from the recognition that coupled with an instance of the maximum throughput problem there exists a related inverse shortest-path problem yielding optimal OSPF link weights. 相似文献
36.
This paper describes techniques for the on-chip measurement of high-frequency and/or high-bandwidth electrical phenomena in ultra large-scale integration environments. The techniques rely on the integration of multiple compact and robust electronic test devices, or cores, at various locations within an integrated circuit. The cores consist primarily of signal generators that approximate the output of a sigma-delta modulator using finite repetitious bit patterns and a small set of highly robust analog components. They are capable of digitizing on-chip signals at gigahertz rates even using low-cost manufacturing processes. Simple communication between the multiple cores enables the migration of many "board-level" type measurements down to the chip level. 相似文献
37.
38.
39.
40.
High-efficiency LEDs of 1.6–2.4 µm spectral range for medical diagnostics and environment monitoring
N. D. Stoyanov B. E. Zhurtanov A. P. Astakhova A. N. Imenkov Yu. P. Yakovlev 《Semiconductors》2003,37(8):971-984
High efficient LED structures covering the spectral range of 1.6–2.4 μm have been developed on the basis of GaSb and its solid
solutions. The electroluminescent characteristics and their temperature and current dependences have been studied. The radiative
and nonradiative recombination mechanisms and their effect on the quantum efficiency have been investigated. A quantum efficiency
of 40–60% has been obtained in the quasi-steady mode at room temperature. A short-pulse optical power of 170 mW was reached.
__________
Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 37, No. 8, 2003, pp. 996–1009.
Original Russian Text Copyright ? 2003 by Stoyanov, Zhurtanov, Astakhova, Imenkov, Yakovlev. 相似文献