全文获取类型
收费全文 | 45379篇 |
免费 | 4783篇 |
国内免费 | 3997篇 |
专业分类
电工技术 | 2196篇 |
技术理论 | 2篇 |
综合类 | 4847篇 |
化学工业 | 8166篇 |
金属工艺 | 4609篇 |
机械仪表 | 5499篇 |
建筑科学 | 3957篇 |
矿业工程 | 2287篇 |
能源动力 | 1148篇 |
轻工业 | 3045篇 |
水利工程 | 1046篇 |
石油天然气 | 2836篇 |
武器工业 | 644篇 |
无线电 | 2070篇 |
一般工业技术 | 4622篇 |
冶金工业 | 1653篇 |
原子能技术 | 269篇 |
自动化技术 | 5263篇 |
出版年
2024年 | 426篇 |
2023年 | 1328篇 |
2022年 | 2343篇 |
2021年 | 2377篇 |
2020年 | 1863篇 |
2019年 | 1446篇 |
2018年 | 1303篇 |
2017年 | 1468篇 |
2016年 | 1595篇 |
2015年 | 1625篇 |
2014年 | 2401篇 |
2013年 | 2197篇 |
2012年 | 2943篇 |
2011年 | 3179篇 |
2010年 | 2476篇 |
2009年 | 2693篇 |
2008年 | 2277篇 |
2007年 | 3052篇 |
2006年 | 2867篇 |
2005年 | 2391篇 |
2004年 | 1915篇 |
2003年 | 1785篇 |
2002年 | 1470篇 |
2001年 | 1175篇 |
2000年 | 1051篇 |
1999年 | 864篇 |
1998年 | 721篇 |
1997年 | 533篇 |
1996年 | 485篇 |
1995年 | 403篇 |
1994年 | 373篇 |
1993年 | 236篇 |
1992年 | 182篇 |
1991年 | 173篇 |
1990年 | 121篇 |
1989年 | 97篇 |
1988年 | 87篇 |
1987年 | 37篇 |
1986年 | 29篇 |
1985年 | 34篇 |
1984年 | 28篇 |
1983年 | 21篇 |
1982年 | 18篇 |
1981年 | 10篇 |
1980年 | 22篇 |
1979年 | 8篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1959年 | 4篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 484 毫秒
201.
虚拟企业模型并行仿真研究 总被引:4,自引:0,他引:4
随着各种全新的制造理念,特别是虚拟企业的出现,企业模型的规模不断扩大,使目前存在的大多数企业模型仿真系统的效率大大下降。该文针对此问题,通过深入分析虚拟企业模型结构,并在已有的构件化企业建模体系CEMS及其仿真系统的基础上,结合异步仿真技术和多线程技术提出了一种分层式企业模型仿真体系结构,为虚拟企业模型的快速高效的仿真提供了一种有效的方法。 相似文献
202.
203.
Failure analysis of hollow glasses The failure analysis is very important to clarify damages of hollow glasses. Damages of glass bottle through over pressure are very often linked with damages to persons. This is the reason why the causal research is from particular importance. Different surface characteristics of glass fragments as well as the fracture pattern give hints to the direction of the crack, the stress just before breakage and the reason of stress. A reconstruction of the bottle is a further helpful instrument for cause studies. The difference of the various characteristics of the surface will be explained. Further on there will be discussed different reasons and mechanism of fracture. 相似文献
204.
蜘蛛丝力学性能的多变性 总被引:8,自引:2,他引:6
为进一步探索蜘蛛丝的成丝机理,研究了不同个体大小,不同生存方式,不同环境湿度的大腹圆蛛牵引丝的拉伸性能。结果表明,蜘蛛对其丝纤维的结构和性能具有自我调控能力,随着环境,自身条件,生存方式等成丝条件的变化,蜘蛛牵引丝的力学性能也会发生相应的变化。 相似文献
205.
Eleonora M. Ungureanu Liviu Birzan George Buica Enache Cristian 《Electrochimica acta》2006,52(3):794-803
The cyclic voltammetry behavior of a series of five 1-substituted azulenes has been investigated as well as the electrochemical chlorination of these compounds. In the case of azulene compounds containing electron withdrawing groups which have higher oxidation potentials than that of the chloride ion, the electrochemical chlorination led usually to 3-chloro derivatives. The electrochemical chlorination fails for azulenes with lower oxidation potentials. Additionally some polyhalogenated compounds were obtained by controlled potential electrolyses. The paper also discusses the reaction mechanism of the electrochemical halogenation of 1-substituted azulenes. 相似文献
206.
马湘平 《石油化工安全环保技术》2006,22(3):22-24,34
通过持续不断的开展安全质量标准化建设,规范危险化学品的安全管理,建立以事故预防与风险控制管理为核心的安全质量标准化管理模式,建立安全生产的长效机制。 相似文献
207.
I. A. Chaban 《Journal of Superconductivity》1996,9(1):33-42
The impurity mechanism proposed earlier is used to interpret the magnetic properties of hightemperature superconductors. The appearance of superconductive granules and the existence of weak bonds in grains of ceramics and in single crystals is explained. The irreversibility line is obtained and its new interpretation as the line of thresholds of appearance of infinite nonsuperconductive cluster is given. The relaxation time of the magnetic susceptibility in alternating magnetic fields is calculated. The decrease of the Meissner fraction with increase in magnetic field and decrease in doping, and other magnetic properties are explained. 相似文献
208.
Philip Tipping 《International Journal of Pressure Vessels and Piping》1996,66(1-3):17-25
The susceptibility and tendency for nuclear power plant (NPP) components to undergo changes in their mechanical and physical properties in the course of the NPP lifetime is generally termed as “ageing”. The light water reactor (LWR) nuclear environment is not a begnign one; it is characterized not only by fast neutrons, which can degrade metallic structures, but also relatively high temperatures of coolant water (around 300°C) which may contain impurities (e.g. sulphate, chloride, peroxides) which can cause corrosion. The hydrodynamical conditions of the coolant in steam generators, for example, can cause thermal fatigue, erosion and corrosion; suspended particulate matter can accelerate erosion processes which can lead to wall thinning and lowering of safety margins. Ageing is, therefore, a very complex mixture of factors concerned with materials, temperatures, times of exposure to environments which vary with time and with respect to chemical composition and flow charactertistics.
The paper describes a few ageing phenomena which can be considered important due to their impact on nuclear safety issues; their influence on economic aspects (availability) of NPP is outlined. Mitigation measures for NPP component ageing problems are given together with recommendations for addressing such issues in NPP now and in the future. 相似文献
209.
转炉溅渣层与镁碳砖炉衬的结合机理 总被引:1,自引:0,他引:1
通过对生产现场带有溅渣层的转炉炉衬残砖和试验室小型坩埚溅渣试验结果进行矿相显微结构分析、研究,确定了溅渣层的矿相组成、溅渣层与MgO-C砖结合区域的矿相结构及坩埚溅渣层自上而下的矿相分布规律,并根据矿相结构分析中观察到的烧结层、结合层和溅渣层3个区域,提出了溅渣层与镁碳砖炉衬的结合机理为化学结合、机械镶嵌与化学烧结结合及冷凝结合3种形式。 相似文献
210.
The interactions of VOHPO4· 0.5H2O and (VO)2P2O7 with the ammoxidation feed and the single components such as ammonia, oxygen, water and component mixtures were studied in detail using XRD and temperature-programmed reaction spectroscopy. The aim of this work was to improve the knowledge of the formation of the active phases or active sites of the catalysts from their precursors under the condition of the ammoxidation reaction. Similar catalytic properties of various applied VPO materials were discussed in terms of the presence of similar structure elements (domains of adjacent edge-sharing VO6 octahedra-units and P-O-NH4 groups). 相似文献