全文获取类型
收费全文 | 28920篇 |
免费 | 3657篇 |
国内免费 | 2481篇 |
专业分类
电工技术 | 2410篇 |
综合类 | 2176篇 |
化学工业 | 5802篇 |
金属工艺 | 2725篇 |
机械仪表 | 2666篇 |
建筑科学 | 1017篇 |
矿业工程 | 1714篇 |
能源动力 | 1033篇 |
轻工业 | 954篇 |
水利工程 | 606篇 |
石油天然气 | 717篇 |
武器工业 | 434篇 |
无线电 | 1916篇 |
一般工业技术 | 4532篇 |
冶金工业 | 1109篇 |
原子能技术 | 628篇 |
自动化技术 | 4619篇 |
出版年
2024年 | 95篇 |
2023年 | 473篇 |
2022年 | 913篇 |
2021年 | 1052篇 |
2020年 | 1176篇 |
2019年 | 1024篇 |
2018年 | 1033篇 |
2017年 | 1315篇 |
2016年 | 1370篇 |
2015年 | 1410篇 |
2014年 | 1890篇 |
2013年 | 2122篇 |
2012年 | 2273篇 |
2011年 | 2562篇 |
2010年 | 1838篇 |
2009年 | 1889篇 |
2008年 | 1686篇 |
2007年 | 1832篇 |
2006年 | 1556篇 |
2005年 | 1295篇 |
2004年 | 1036篇 |
2003年 | 818篇 |
2002年 | 715篇 |
2001年 | 614篇 |
2000年 | 555篇 |
1999年 | 479篇 |
1998年 | 392篇 |
1997年 | 314篇 |
1996年 | 253篇 |
1995年 | 232篇 |
1994年 | 186篇 |
1993年 | 153篇 |
1992年 | 118篇 |
1991年 | 64篇 |
1990年 | 69篇 |
1989年 | 52篇 |
1988年 | 54篇 |
1987年 | 33篇 |
1986年 | 13篇 |
1985年 | 21篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 11篇 |
1981年 | 5篇 |
1980年 | 9篇 |
1979年 | 13篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1959年 | 9篇 |
1951年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
91.
用激光粒度分析仪测定二氧化锆粒度 总被引:3,自引:0,他引:3
介绍以六偏磷酸钠作为分散剂,采用激光粒度分析仪测量二氧化锆粒度的一种新方法。该方法的测量范围为0.05~300μm。 相似文献
92.
Heat transfer characteristics of a swirling impinging jet have been experimentally examined using a combined particle image velocimetry (PIV) and laser‐induced fluorescence (LIF) technique for simultaneous measurement of velocity and temperature fields. The present study shows that the radial width of the jet stretches with increasing swirl intensity, and that the stretching phenomenon contributes to the maximum local heat transfer coefficient. At the stagnation region, the flow near the heated surface is mixed intermittently by reverse flows toward upstream, and spatial distributions of temperature are correlated with instantaneous velocity vector maps. The dynamic behavior of recirculation zones, attributed to swirl number Sw and impinging distance, mainly determines the turbulent heat transfer at the stagnation region. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(8): 663–673, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10120 相似文献
93.
The exact magnetization pattern of magnetic films close to a spin-reorientation transition is difficult to analyze due to the intrinsically three-dimensional (3d) variation of the orientation of the local magnetization. We present a technique how this can be performed, based on the analysis of high quality 2d polarization maps from a single scanning electron microscope with polarization analysis (SEMPA) measurement with tilted sample. The key tool is the statistical distribution of all occurring polarization doublets, visualized in a 2d histogram plot. From the shape of the distribution the type of transition—canted-phase, or coexisting phases—can be inferred. For the canted-phase state, the canting angle can be accurately determined from geometrical considerations. With help of the histogram the image data can be analyzed and the three components of the magnetization can be calculated for most points of the image. For a Co/Pt multilayer film we found a cone state. The magnetization forms a complex pattern consisting of out-of-plane domains while the in-plane magnetization shows a maze pattern. 相似文献
94.
Hun Xue 《Materials Letters》2007,61(2):347-350
Macroporous nanocrystalline zinc ferrite with single spinel-phase was prepared by a facile self-propagating combustion method using zinc nitrate, iron nitrate and glycine. The as-prepared ZnFe2O4 were characterized by X-ray diffraction (XRD) analysis, N2 adsorption, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and energy dispersive X-ray spectrum (EDS). The magnetic properties of the prepared ZnFe2O4 were also studied. 相似文献
95.
本文在重点考虑TiNi合金高弹性变形量的前提下,采用等向强化模型,对不锈钢和超弹TiNi合金在法向接触载荷作用下的六种模型进行了有限元(FEM)分析。结果表明:在相同载荷条件下,超弹TiNi合金产生的von Mises弹性应变要高于不锈钢,但其von Mises应力和塑性应变却恰恰相反,在同一载荷下该合金发生塑性变形的区域要小于不锈钢;此外,超弹TiNi合金发生塑性变形要比不锈钢困难,所需的临界载荷值随其最大弹性变形量(屈服点处的应变值)的增加而增加。最后,基于本文的有限元计算结果对超弹TiNi合金的蘑粒磨损和疲劳磨损机制进行了讨论。 相似文献
96.
简述轴承工作性质,巴氏合金应用与相组成的基本情况。论述汽轮机转子在两个电厂长期运行后,由于轴颈发生的不正常摩擦损伤,在大修改造中由无损检查、机械加工揭示出轴颈存在严重的渗巴氏合金现象,低熔点金属Sn、Sb与Cu向转子材料晶界的深层渗入最终导致了3根大型在投转子的严重开裂与报废。图11表2 相似文献
97.
98.
Acid Green 25, which is a diazoic dye bearing two sulfonic groups, is efficiently sorbed on chitosan. The protonation of chitosan may explain the electrostatic attraction of this anionic dye and that its optimum pH is close to 3. Preliminary protonation of amine groups (obtained by contact with a sulfuric acid solution) reduced the variation of solution pH following sorbent addition but significantly reduced sorption performance: the maximum sorption capacity of raw chitosan, 525 mg dye/g (0.84 mmol dye/g), was halved by acidic preconditioning. The acidic conditioning also reduced the kinetic rate—the time necessary to reach equilibrium increased up to threefold depending on the experimental conditions. The size of sorbent particles influenced sorption kinetics and equilibrium because of resistance to intraparticle diffusion, but the sorption appeared to occur not only at the surface of the sorbent but also in the intraparticle network of the polymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1073–1080, 2003 相似文献
99.
100.