全文获取类型
收费全文 | 18381篇 |
免费 | 1832篇 |
国内免费 | 945篇 |
专业分类
电工技术 | 615篇 |
技术理论 | 1篇 |
综合类 | 1827篇 |
化学工业 | 1617篇 |
金属工艺 | 794篇 |
机械仪表 | 1577篇 |
建筑科学 | 4484篇 |
矿业工程 | 711篇 |
能源动力 | 398篇 |
轻工业 | 951篇 |
水利工程 | 539篇 |
石油天然气 | 1558篇 |
武器工业 | 178篇 |
无线电 | 707篇 |
一般工业技术 | 2566篇 |
冶金工业 | 737篇 |
原子能技术 | 114篇 |
自动化技术 | 1784篇 |
出版年
2024年 | 94篇 |
2023年 | 338篇 |
2022年 | 545篇 |
2021年 | 643篇 |
2020年 | 665篇 |
2019年 | 553篇 |
2018年 | 504篇 |
2017年 | 574篇 |
2016年 | 586篇 |
2015年 | 659篇 |
2014年 | 1034篇 |
2013年 | 1131篇 |
2012年 | 1304篇 |
2011年 | 1338篇 |
2010年 | 1072篇 |
2009年 | 1055篇 |
2008年 | 950篇 |
2007年 | 1206篇 |
2006年 | 1046篇 |
2005年 | 904篇 |
2004年 | 822篇 |
2003年 | 638篇 |
2002年 | 491篇 |
2001年 | 506篇 |
2000年 | 431篇 |
1999年 | 337篇 |
1998年 | 282篇 |
1997年 | 277篇 |
1996年 | 218篇 |
1995年 | 193篇 |
1994年 | 126篇 |
1993年 | 116篇 |
1992年 | 92篇 |
1991年 | 71篇 |
1990年 | 70篇 |
1989年 | 67篇 |
1988年 | 38篇 |
1987年 | 35篇 |
1986年 | 20篇 |
1985年 | 31篇 |
1984年 | 21篇 |
1983年 | 20篇 |
1982年 | 13篇 |
1981年 | 6篇 |
1980年 | 20篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1964年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
41.
Toshihiko Hoshide Junpei Fujita 《Journal of Materials Engineering and Performance》2008,17(5):627-632
Strength of ground ceramics may be affected by residual stress as well as surface flaws induced by grinding. Strength prediction
for ground ceramics is convenient for mechanical design of ceramic components. In this article, a numerical procedure based
on fracture mechanics was proposed to estimate strength distribution of ground ceramics by considering grinding-induced residual
stress. Bending strength and residual stress of ground ceramics were measured for three grinding-conditions. By comparison
of simulated results with experimental ones, it was revealed that strength characteristics in experiments were well simulated
by using the proposed procedure. 相似文献
42.
A. Vahid Shahidi I. Shih T. Araki C. H. Champness 《Journal of Electronic Materials》1985,14(3):297-310
Structural investigation on monocrystalline CuInSe2 samples has been made. From the single crystal results, the space group of CuInSe2 was confirmed to be Iˉ42d and the crystal solidification direction was investigated. Compositional uniformity of the ingots
was established by EPMA and it was found that the indium concentration was greater than that for copper. Systematic annealing
experiments were carried out in vacuum at different temperatures (as low as 160° C) and for different times. Large variation
in resistivity was observed after the annealing treatment. P-type samples were found to convert to n-type after the heat-treatments. 相似文献
43.
44.
45.
裂齿矩形翅片板翅式换热器优化设计的分析 总被引:2,自引:0,他引:2
对裂齿矩形翅片板翅式换热器中的裂齿矩形翅片的传热效率作了分析,并以单位质量材耗的换热能力最大为目标函数,分析研究了在不同雷诺数(Re)的操作条件下裂齿矩形翅片间角度、翅片厚、长度、宽度及极厚之间的关系。结果表明:在气体换热的场合下,当Re在某一范围时翅片可有效地起到强化传热的作用。当板厚为5mm,翅片厚为3mm,翅片间夹角为45°~70°,Re为2×10~3~8×10~3,最佳翅片纵向间距与翅片长度和翅片厚度乘积的平方根的比为1.5~2.5,最佳翅片尺寸系数为3~5时,传热强化效果较好。 相似文献
46.
Fe100-xPtx(x=30at.%-60at.% ) nanocomposite films were deposited on natural-oxidized Si(100) substrates by magnetron sputtering. The as-deposited films were annealed between 373 and 1073 K. In situ X-ray diffraction shows that the FePt nanocomposite films undergo a phase transformation from a disordered FCC phase to an ordered L10 phase between 673 and 773 K. The coercivity is 306 kA·m-1 whiles the average grain sizes is about 10 nm in the optimized FePt alloy film sample annealed at 673K. The adjustable coercivity and fine grain size suggest that this FePt nanocomposites system is suitable as recording media at extremely high areal density. 相似文献
47.
郭广海 《青岛科技大学学报(自然科学版)》2008,29(3)
采用多项式函数代替乌龟坐标的方法,给出静态球对称时空中黑洞事件视界和宇宙视界区域内标量场方程的解,并对事件视界附近势垒的性质进行了讨论。发现对带电量不同的时空,标量场辐射的形式亦有所不同;势垒随宇宙学常数的减小而变窄、变高。 相似文献
48.
This paper presents the result of a study on the effect of pounding at expansion joints on concrete bridge response to earthquake ground motions. An engineering approach, rather than continuum mechanics approach, is emphasized. First, the dynamic behavior of a damped multidegree-of-freedom bridge system separated by an expansion joint involving an impact is examined by means of the finite element method. Second, the sensitivity analysis of the stiffness in gap elements is performed. Third, usefulness of the analysis method for simulation of pounding phenomena is demonstrated and the effect of pounding on the ductility demands measured in terms of the rotation of column ends is investigated. Two-dimensional finite element analysis using a bilinear hysterestic model for bridge substructure joints and a nonlinear gap element for the expansion joint is performed on a realistic bridge with an expansion joint. The effects of the primary factors on the ductility demand such as gap sizes and characteristics of earthquake ground motion are investigated through a parametric study. The major conclusions are (1) the effect of impact most directly depends on the size of momentum (or pounding magnitude); and (2) the pounding effect is generally found to be negligible on the ductility demand for wide practical ranges of gap size and peak ground acceleration, but is potentially significant at the locations of impact. 相似文献
49.
50.