全文获取类型
收费全文 | 59862篇 |
免费 | 8787篇 |
国内免费 | 5280篇 |
专业分类
电工技术 | 7688篇 |
技术理论 | 2篇 |
综合类 | 6040篇 |
化学工业 | 5010篇 |
金属工艺 | 2140篇 |
机械仪表 | 5974篇 |
建筑科学 | 2757篇 |
矿业工程 | 2059篇 |
能源动力 | 3039篇 |
轻工业 | 3695篇 |
水利工程 | 1592篇 |
石油天然气 | 2594篇 |
武器工业 | 816篇 |
无线电 | 4693篇 |
一般工业技术 | 5271篇 |
冶金工业 | 1842篇 |
原子能技术 | 286篇 |
自动化技术 | 18431篇 |
出版年
2024年 | 598篇 |
2023年 | 1522篇 |
2022年 | 2596篇 |
2021年 | 2722篇 |
2020年 | 3021篇 |
2019年 | 2574篇 |
2018年 | 2299篇 |
2017年 | 2793篇 |
2016年 | 3052篇 |
2015年 | 3383篇 |
2014年 | 4718篇 |
2013年 | 4537篇 |
2012年 | 5103篇 |
2011年 | 5131篇 |
2010年 | 3524篇 |
2009年 | 3728篇 |
2008年 | 3274篇 |
2007年 | 3669篇 |
2006年 | 3016篇 |
2005年 | 2408篇 |
2004年 | 1953篇 |
2003年 | 1536篇 |
2002年 | 1300篇 |
2001年 | 1046篇 |
2000年 | 875篇 |
1999年 | 584篇 |
1998年 | 561篇 |
1997年 | 473篇 |
1996年 | 373篇 |
1995年 | 324篇 |
1994年 | 262篇 |
1993年 | 197篇 |
1992年 | 168篇 |
1991年 | 139篇 |
1990年 | 120篇 |
1989年 | 99篇 |
1988年 | 62篇 |
1987年 | 25篇 |
1986年 | 25篇 |
1985年 | 14篇 |
1984年 | 16篇 |
1983年 | 18篇 |
1982年 | 18篇 |
1981年 | 8篇 |
1980年 | 15篇 |
1979年 | 13篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1959年 | 4篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 168 毫秒
11.
Shear Bombs in Fibre Composites Despite an optimum external shape non‐load adapted internal fibre orientation can lead to the formation of shear cracks where crossing tension‐compression principal stress trajectories create localized shear peaks. Trees are subject to those failure because they cannot re‐arrange their fibres after wood formation. Bones can adjust their micro‐structure to changing load conditions and in this way can better control shear failure. The engineer working with fibre composites should be alert to avoid fibre arrangements not following the force flow. Localized shear zones may also form near notches similar to normal notch stresses, however they are not always situated at the contour line of the notch. 相似文献
12.
步进式加热炉炉温优化设定模型及软件开发 总被引:1,自引:0,他引:1
针对线材厂步进式加热炉实际工况,提出了基于经验规则的炉温优化设定模型和在线自学习获取知识的思想,并以炉温优化设定模型为核心,开发出加热炉计算机控制系统的优化运行软件。 相似文献
13.
14.
简单回顾了国内外在火电机组运行优化领域的研究历程,列举了目前国内外市场上针对火电机组的各种主流运行优化产品的功能特点和应用情况,分析了国外引进产品和国内自主研发产品在中国当前市场环境下各自的优势和劣势。介绍了当前运行优化系统在国内电站机组的应用现状,阐述了国内外运行优化系统在实际应用中存在的问题,并提出了相应的改进意见。对机组运行优化系统的未来发展进行了展望,指出机组运行优化系统将利用先进技术设备和信息平台,与电站管理紧密结合,在日益规范的市场中不断发展完善,为提高电站经济性发挥更大的作用。 相似文献
15.
Martijn Hendriks Barend van den Nieuwelaar Frits Vaandrager 《International Journal on Software Tools for Technology Transfer (STTT)》2006,8(6):633-647
For a case-study of a wafer scanner from the semiconductor industry it is shown how model checking techniques can be used
to compute (1) a simple yet optimal deadlock avoidance policy, and (2) an infinite schedule that optimizes throughput. in
the absence of errors. Deadlock avoidance is studied based on a simple finite state model using Smv, and for throughput analysis a more detailed timed automaton model has been constructed and analyzed using the Uppaal tool. The Smv and Uppaal models are formally related through the notion of a stuttering bisimulation. The results were obtained within 2 weeks, which
confirms once more that model checking techniques may help to improve the design process of realistic, industrial systems.
Methodologically, the case study is interesting since two models were used to obtain results that could not have been obtained
using only a single model.
Supported by the European Community Project IST-2001-35304 (Ametist), http://ametist.cs.utwente.nl/. 相似文献
16.
Combined shape and sizing optimization of truss structures 总被引:1,自引:0,他引:1
In this paper, an evolutionary optimization method is presented for weight minimum problem of a 3-dimensional truss structure
in terms of nodal coordinates and element cross-sectional areas. The structure is subject to stress, local buckling and displacement
constraints. Two types of design variables with different natures are optimized separately: (1) a fully stressed design (FSD)
and scaling techniques are applied to sizing variables and (2) the evolutionary node shift method is applied to shape variables.
Alternating procedure is utilized to couple the two types of variables and to combine the results. The optimum solution is
achieved gradually from the initial configuration design. Two typical truss structures are examined to illustrate the validity
of the method.
Received: 22 October 2001 / Accepted: 04 June 2002
This research work is supported by the National Natural Science Foundation of China under the guarantees no. 10072050 and
10172072, respectively. 相似文献
17.
18.
Optimizing of laminar viscous flow through a pipe by two dimensionless values is investigated analytically. Dimensionless entropy generation and pumping power to heat transfer rate ratio are used as basis for constant viscous and the temperature dependence on the viscosity. For this matter we calculate entropy generation and pumping power for a fully developed in a pipe subjected to constant wall temperature for either constant viscosity and the variable viscosity. The variation entropy generation increase along the pipe length for viscous fluid is drawn, either the variation summation dimensionless entropy generation and the pumping power to heat transfer rate ratio are varying the fluid inlet temperature for fixed pipe length and are varying pipe length for fixed fluid inlet temperature are drawn. For low heat transfer conditions the entropy generation due to viscosity friction becomes dominant and the dependence of viscosity with the temperature becomes essentially important to be considered. 相似文献
19.
Damiana Chinese Antonella Meneghetti Gioacchino Nardin Patrizia Simeoni 《国际能源研究杂志》2007,31(9):829-848
A mixed integer linear programming model combined with a more traditional design by scenarios is proposed to optimize facilities size and operation mode of a municipal energy system involving significant civil centres and a hospital. Moving from the need of a new heat and power station for the local hospital due to the construction of new pavilions, the opportunity of involving other centres in the neighbourhood in a distributed cogeneration system is analysed, increasing system complexity step by step. Smaller cogeneration units tailored to hospital needs are rewarding ventures with relatively low risks but, in a country whose traditional power generation systems heavily rely on fossil fuels and where energy policy and market conditions can make it profitable to sell surplus power, district heating systems foster the installation of larger cogenerators and lead thereby to higher profits and to better performance as for primary energy savings and greenhouse gases emission reduction. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
20.