全文获取类型
收费全文 | 19497篇 |
免费 | 2702篇 |
国内免费 | 1825篇 |
专业分类
电工技术 | 3013篇 |
技术理论 | 3篇 |
综合类 | 2346篇 |
化学工业 | 2593篇 |
金属工艺 | 733篇 |
机械仪表 | 982篇 |
建筑科学 | 1103篇 |
矿业工程 | 520篇 |
能源动力 | 663篇 |
轻工业 | 630篇 |
水利工程 | 351篇 |
石油天然气 | 585篇 |
武器工业 | 240篇 |
无线电 | 2411篇 |
一般工业技术 | 2223篇 |
冶金工业 | 650篇 |
原子能技术 | 299篇 |
自动化技术 | 4679篇 |
出版年
2024年 | 93篇 |
2023年 | 335篇 |
2022年 | 450篇 |
2021年 | 579篇 |
2020年 | 743篇 |
2019年 | 756篇 |
2018年 | 630篇 |
2017年 | 764篇 |
2016年 | 821篇 |
2015年 | 810篇 |
2014年 | 1129篇 |
2013年 | 1276篇 |
2012年 | 1217篇 |
2011年 | 1336篇 |
2010年 | 993篇 |
2009年 | 982篇 |
2008年 | 1085篇 |
2007年 | 1180篇 |
2006年 | 1190篇 |
2005年 | 1014篇 |
2004年 | 903篇 |
2003年 | 782篇 |
2002年 | 743篇 |
2001年 | 624篇 |
2000年 | 552篇 |
1999年 | 519篇 |
1998年 | 354篇 |
1997年 | 352篇 |
1996年 | 298篇 |
1995年 | 260篇 |
1994年 | 243篇 |
1993年 | 218篇 |
1992年 | 163篇 |
1991年 | 114篇 |
1990年 | 108篇 |
1989年 | 67篇 |
1988年 | 65篇 |
1987年 | 35篇 |
1986年 | 34篇 |
1985年 | 20篇 |
1984年 | 31篇 |
1983年 | 25篇 |
1982年 | 24篇 |
1981年 | 13篇 |
1980年 | 12篇 |
1979年 | 17篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1960年 | 5篇 |
1959年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
入侵检测系统技术现状及其发展趋势 总被引:21,自引:0,他引:21
阐述了入侵检测系统(IDS)的起源、发展和分类,介绍了它的结构和标准化工作,对入侵检测系统存在的问题及发展趋势作了概述。 相似文献
103.
M. M. Rashid 《International journal for numerical methods in engineering》2002,55(4):431-450
A computational procedure for remapping material state information from one finite element mesh to another is described. The procedure is useful in connection with evolving meshes for inelastic problems, as for example occur in the context of fracture simulation and adaptive mesh refinement. The proposed method is based on weak enforcement of equality between corresponding fields on the two meshes, where piecewise‐constant fields on both meshes are generalized from the quadrature‐point values. The essential algorithmic problem is that of calculating the volume partition of an arbitrary convex region with respect to a covering set of disjoint convex regions. Instead of geometrically resolving the associated intersections, the problem is herein approximated by a constrained optimization problem, which may be readily and efficiently solved computationally. This formulation is a main contribution of the paper. Computational examples are given that illustrate the effectiveness of the proposed procedure. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
104.
采用了一个既能提高立方型状态方程比体积计算精度,又不影响气液平衡条件的简单摩尔修正项来改进PR方程比体积的计算。本文对19种低温流体给出其修正项的值,计算饱和蒸气和液体比体积,并与未修正的PR方程的计算值比较,结果表明这种修正能显著提高低温流体(包括量子流体氢、氦和强极性的氨气)饱和液体比体积的计算精度,并对蒸气比体积的计算也略有改进。 相似文献
105.
106.
V. V. Tcherdyntsev S. D. Kaloshkin A. I. Salimon E. A. Leonova I. A. Tomilin J. Eckert F. Schurack V. D. Rogozin S. P. Pisarev Yu. P. Trykov 《Materials and Manufacturing Processes》2002,17(6):825-841
Al-Cu-Fe alloys were prepared from elemental powders in a high-energy planetary ball mill. A sequence of solid state reactions resulting in quasicrystal (QC) phase formation takes place during heating of the as-milled powder. These reactions were studied by both differential scanning calorimetry and x-ray diffraction methods. Mechanically alloyed powders were consolidated by cold and hot pressing, as well as by explosive compaction. After annealing at sufficiently high temperatures, the consolidated samples are single-phase QC, except the ones consolidated by explosion. The high reactivity of the as-milled alloys causes the appearance of high porosity of the consolidated samples after the annealing. 相似文献
107.
108.
109.
The problem of managing water scarcity by resorting to complex interconnected multi-source water systems needs to utilize
management optimization techniques analyzing aspects of water quantity and quality in a common strategy. In the southern regions
of Mediterranean Europe, the greater part of water resources for supply systems are derived from artificial reservoirs and
water systems can become quite complex since they interconnect several sources and demand centers, as indeed occurs in the
Region of Sardinia (Italy). A simplified approach to the requirement to insert water quality aspects in the mathematical optimization
model can be achieved by examining the trophic conditions of reservoirs. Trophic State Indexes (TSI) based on Carlson’s (1977) make it possible to insert quality constraints in the water management optimization model also considering complex multi-reservoir
and multi-user systems. Model formalization and implementation by the optimization toolkit WARGI (Water Resource system optimization
aided by Graphical Interface) (Sechi and Zuddas 2000; Manca et al. 2004; Salis et al. 2005) is illustrated in this paper. The usefulness of a mixed quantity–quality optimization approach has been confirmed by WARGI
application to a real multi-reservoir water resources system in southern Sardinia. The optimization model remains computationally
efficient dealing with this complex multi-reservoir system and the obtained results can be seen as a reference target in a
subsequent simulation phase. 相似文献
110.
在搜集国内外有关资料的基础上,通过对混凝土在多轴应力作用下的徐变与强度关系分析,说明在多轴应力状态下不能简单地采用叠加原理。展示了新的三轴徐变量测仪器及其徐变试验成果以及2组多轴与单轴应力状态下的徐变恢复试验成果,并对试验数据进行比较分析,得到多轴应力状态下徐变恢复与应力大小以及持荷时间之间的规律,证实了多轴应力状态下的徐变恢复与已经产生的压缩徐变有密切的关系。 相似文献