全文获取类型
收费全文 | 40207篇 |
免费 | 3460篇 |
国内免费 | 1579篇 |
专业分类
电工技术 | 3313篇 |
技术理论 | 2篇 |
综合类 | 3552篇 |
化学工业 | 3590篇 |
金属工艺 | 961篇 |
机械仪表 | 1953篇 |
建筑科学 | 7380篇 |
矿业工程 | 1465篇 |
能源动力 | 1460篇 |
轻工业 | 6380篇 |
水利工程 | 1810篇 |
石油天然气 | 1494篇 |
武器工业 | 313篇 |
无线电 | 1914篇 |
一般工业技术 | 3768篇 |
冶金工业 | 2426篇 |
原子能技术 | 496篇 |
自动化技术 | 2969篇 |
出版年
2024年 | 197篇 |
2023年 | 631篇 |
2022年 | 1463篇 |
2021年 | 1511篇 |
2020年 | 1582篇 |
2019年 | 1252篇 |
2018年 | 1203篇 |
2017年 | 1411篇 |
2016年 | 1578篇 |
2015年 | 1643篇 |
2014年 | 3278篇 |
2013年 | 2665篇 |
2012年 | 3327篇 |
2011年 | 3521篇 |
2010年 | 2559篇 |
2009年 | 2397篇 |
2008年 | 1928篇 |
2007年 | 2195篇 |
2006年 | 1910篇 |
2005年 | 1564篇 |
2004年 | 1274篇 |
2003年 | 1125篇 |
2002年 | 879篇 |
2001年 | 738篇 |
2000年 | 572篇 |
1999年 | 481篇 |
1998年 | 390篇 |
1997年 | 296篇 |
1996年 | 228篇 |
1995年 | 220篇 |
1994年 | 175篇 |
1993年 | 140篇 |
1992年 | 132篇 |
1991年 | 94篇 |
1990年 | 86篇 |
1989年 | 63篇 |
1988年 | 61篇 |
1987年 | 44篇 |
1986年 | 31篇 |
1985年 | 35篇 |
1984年 | 30篇 |
1983年 | 18篇 |
1982年 | 24篇 |
1980年 | 25篇 |
1979年 | 26篇 |
1965年 | 18篇 |
1964年 | 23篇 |
1963年 | 18篇 |
1958年 | 16篇 |
1957年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Udayan Nandkeolyar David P. Christy 《International Journal of Flexible Manufacturing Systems》1992,4(3-4):267-292
Evaluating the design of flexible manufacturing systems is complex. Developing a measure of performance useful for evaluating alternate designs continues to be interesting. Here, total productivity of the system is proposed as an appropriate measure. Specification of parameters based upon strategic considerations for this measure are discussed. Finally, the usefulness of the measure is demonstrated through an example. 相似文献
102.
J. Gegner Priv.‐Doz. Dr. W. Nierlich M. Brückner 《Materialwissenschaft und Werkstofftechnik》2007,38(8):613-623
Due to clearly distinguishable damage symptoms, it is differentiated between the surface and sub‐surface failure mode of rolling bearings. Material states red out by X‐ray diffraction (XRD) residual stress measurements point to a variety of loading conditions especially at raceway surfaces that are associated with several competing failure mechanisms. The corresponding lifetime reduction can range from the lower fatigue strength region to material ratcheting in extreme cases. Relevant position of the microstructural changes and nature of the failure mechanisms are characterized. The time alteration of the XRD material parameters measured at or near the surface and at the depth of the maximum equivalent stress correlates, in a different manner, with the statistical parameter of the 10 % bearing life. Both failure modes are illustrated by concrete examples. Contaminated lubricant and boundary lubrication, which represent practically important surface‐induced failures, are discussed in more detail. Gray staining, i.e. shallow pitting, often occurs without distinct indication of global material aging by means of XRD characteristics. Here, scanning electron microscopy observations and electron microprobe analyses point to corrosion fatigue as acting surface failure mechanism. The interaction between material and lubricant under complex loading regimes particularly of mixed friction and corrosion opens further failure research areas in the field of tribology. 相似文献
103.
Performance on antisaccade trials requires the inhibition of a prepotent response (i.e., don't look at the flashing cue) and the generation and execution of a correct saccade in the opposite direction. The authors attempted to further specify the role of working memory (WM) span differences in the antisaccade task. They tested high- and low-span individuals on variants of prosaccade and antisaccade trials in which an eye movement is the sole requirement. In 3 experiments, they demonstrated the importance of WM span differences in both suppression of a reflexive saccade and generation of a volitional eye movement. The results support the contention that individual differences in WM span are not exclusively due to differences in inhibition but also reflect differences in directing the focus of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
104.
Original studies on gust factor buffeting dealt with the alongwind displacement of structures. Research on this topic carried out since the nineties followed two distinct lines: the first determines the maximum effects due to the alongwind response; the second extends the original method from the alongwind response to crosswind and torsional responses. This paper represents the junction point of these research lines with reference to cantilever slender vertical structures. It derives the most relevant effects associated with the three-dimensional (3-D) wind-excited response of this structural type and shows that a suitable definition of one non-dimensional quantity, referred to as the 3-D gust effect factor, provides such effects at any level through a wide set of experimental, numerical and analytical procedures. A new definition of a 3-D equivalent static force consistent with this method is also introduced and critically compared with previous analogous statements. 相似文献
105.
本文分析日产车用PDG型柴油机的结构特点及其缸套穴蚀的形成原因、危害和检查与判断方法,并提出在使用中应采取的预防措施。 相似文献
106.
A centrifugal partition chromatograph (CPC) was used as a liquid-liquid catalytic reactor for the isomerisation of hexen-3-ol into ethylpropylketone with a water soluble rhodium catalyst. Global mass transfer coefficients were measured and shown to depend on both the nature of the solute and the flow rate. Liquid-liquid partition isotherms were also determined with the CPC using elution chromatography. Finally, a reactor model was derived to account for the experimental results obtained both under stationary and transient (pulse) conditions. A parameter sensitivity evaluation is also presented. 相似文献
107.
J. W. PARK R.F. TESTIN P. J. VERGANO H.J. PARK C.L. WELLER 《Journal of food science》1996,61(4):766-768
The effects of various stearic-palmitic acid blend concentrations in films, storage temperatures and storage times on potato chip quality were evaluated using Response Surface Methodology. Storage temperature and time affected the quality of potato chips. The maximum storage times for acceptable potato chip quality were: 30 to 43 days, 23 to 25 days, and 11 to 12 days for storage temperatures of 15, 25 and 35°C, respectively. Results were independent of stearic-palmitic acid blend concentrations. 相似文献
108.
螺丝湾水电站作为云南省电力局( 集团公司) 、迪庆州、省投资公司三方合资建设的电站,是迪庆藏族自治州自建国以来投资最大的一个建设项目,它的建成,开创了滇西北水电资源多方合资开发的先例,有其特殊的经济和政治意义。本文结合螺丝湾水电站建设的实际情况,论述了在市场经济条件下做好螺丝湾电站建设中“三控制”的几项措施 相似文献
109.
STN-LCD采用新的取向层,消除了残象;采用新的驱动波形,消除了串扰;采用二(口恶)烷、卤化物、链烯基、醚和二苯乙炔,改进了液晶料材的性能,使STN-LCD获得高的对比度、快的响应速度、低的驱动电压;采用有源矩阵驱动方法,消除了帧响应,使STN-LCD获得高的对比度、高的亮度及视频响应速度;使用温度跟踪电路,自动跟踪STN-LCD的阀值电压,使STN-LCD获得宽的工作温度。 相似文献
110.
根据面板堆石坝的结构特点和工作条件,采用动力非线性有限元法,对清平水库面板坝进行了空库和满库条件下地震反应分析与比较、混凝土面板地震抗滑稳定分析及坝基饱和细砂层的地震液化验算,综合评价大坝的安全性. 相似文献