全文获取类型
收费全文 | 1416914篇 |
免费 | 23969篇 |
国内免费 | 6909篇 |
专业分类
电工技术 | 33853篇 |
综合类 | 6329篇 |
化学工业 | 266229篇 |
金属工艺 | 62866篇 |
机械仪表 | 39247篇 |
建筑科学 | 44037篇 |
矿业工程 | 11223篇 |
能源动力 | 50047篇 |
轻工业 | 100266篇 |
水利工程 | 14108篇 |
石油天然气 | 37296篇 |
武器工业 | 128篇 |
无线电 | 193553篇 |
一般工业技术 | 268454篇 |
冶金工业 | 121840篇 |
原子能技术 | 33662篇 |
自动化技术 | 164654篇 |
出版年
2021年 | 15405篇 |
2020年 | 11691篇 |
2019年 | 14441篇 |
2018年 | 13944篇 |
2017年 | 13121篇 |
2016年 | 20266篇 |
2015年 | 17100篇 |
2014年 | 28438篇 |
2013年 | 87309篇 |
2012年 | 32734篇 |
2011年 | 43614篇 |
2010年 | 40331篇 |
2009年 | 49355篇 |
2008年 | 41268篇 |
2007年 | 37998篇 |
2006年 | 42422篇 |
2005年 | 36729篇 |
2004年 | 39388篇 |
2003年 | 39502篇 |
2002年 | 38864篇 |
2001年 | 35213篇 |
2000年 | 34015篇 |
1999年 | 32370篇 |
1998年 | 31318篇 |
1997年 | 31142篇 |
1996年 | 30180篇 |
1995年 | 27696篇 |
1994年 | 26327篇 |
1993年 | 26228篇 |
1992年 | 25364篇 |
1991年 | 22316篇 |
1990年 | 22757篇 |
1989年 | 21841篇 |
1988年 | 20257篇 |
1987年 | 18673篇 |
1986年 | 17940篇 |
1985年 | 21289篇 |
1984年 | 21845篇 |
1983年 | 19830篇 |
1982年 | 18957篇 |
1981年 | 19022篇 |
1980年 | 17595篇 |
1979年 | 18186篇 |
1978年 | 17456篇 |
1977年 | 16664篇 |
1976年 | 16693篇 |
1975年 | 15777篇 |
1974年 | 15312篇 |
1973年 | 15378篇 |
1972年 | 12858篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Dell'Amico M. Maffioli F. Merani M.L. 《Wireless Communications, IEEE Transactions on》2004,3(4):1013-1017
This paper proposes some novel techniques to accommodate users with different rate requirements in a wideband code-division multiple-access system employing orthogonal variable spreading factor codes. Two simple static code assignment strategies are first considered, and an improvement based on multicode assignment. Then the new idea of tree partitioning is introduced and used to devise a dynamic code reassignment algorithm. The behavior of these different techniques is experimentally investigated, in terms of call blocking probability and number of required reassignments. The tree partitioning method exhibits very good performances. 相似文献
102.
本部分将讲述PortletConfig对象及其PortletContext对象的概念及应用。 相似文献
103.
Quasi-static stress fields for a crack inclined to the property gradation in functionally graded materials 总被引:3,自引:0,他引:3
Summary. Quasi-static stress fields for a crack inclined to the direction of property gradation in functionally graded materials (FGMs)
are obtained through an asymptotic analysis coupled with Westergaard's stress function approach. The elastic modulus of the
FGM is assumed to vary exponentially along the gradation direction. The mode mixity due to the inclination of the property
gradient is accommodated in the analysis through superposition of opening and shear modes. The first four terms in the expansion
of the stress field are derived to explicitly bring out the influence of nonhomogeneity on the structure of the stress field.
Using these stress field contours of constant maximum shear stress, constant maximum principal stress, constant first stress
invariant and constant out of plane displacement are generated, and the effect of inclination of the property gradation direction
on these contours is discussed.
Received September 22, 2002
Published online: May 20, 2003
The financial support of National Science Foundation (NSF) under grant no. CMS 99000138 is gratefully acknowledged. 相似文献
104.
105.
106.
107.
108.
109.
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
110.
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