全文获取类型
收费全文 | 12152篇 |
免费 | 1085篇 |
国内免费 | 624篇 |
专业分类
电工技术 | 674篇 |
综合类 | 1090篇 |
化学工业 | 2145篇 |
金属工艺 | 900篇 |
机械仪表 | 594篇 |
建筑科学 | 2070篇 |
矿业工程 | 344篇 |
能源动力 | 429篇 |
轻工业 | 254篇 |
水利工程 | 422篇 |
石油天然气 | 497篇 |
武器工业 | 108篇 |
无线电 | 759篇 |
一般工业技术 | 2049篇 |
冶金工业 | 341篇 |
原子能技术 | 128篇 |
自动化技术 | 1057篇 |
出版年
2024年 | 42篇 |
2023年 | 199篇 |
2022年 | 287篇 |
2021年 | 348篇 |
2020年 | 353篇 |
2019年 | 320篇 |
2018年 | 312篇 |
2017年 | 413篇 |
2016年 | 434篇 |
2015年 | 475篇 |
2014年 | 673篇 |
2013年 | 863篇 |
2012年 | 856篇 |
2011年 | 880篇 |
2010年 | 712篇 |
2009年 | 706篇 |
2008年 | 604篇 |
2007年 | 756篇 |
2006年 | 653篇 |
2005年 | 562篇 |
2004年 | 505篇 |
2003年 | 460篇 |
2002年 | 374篇 |
2001年 | 348篇 |
2000年 | 252篇 |
1999年 | 218篇 |
1998年 | 194篇 |
1997年 | 171篇 |
1996年 | 155篇 |
1995年 | 101篇 |
1994年 | 102篇 |
1993年 | 68篇 |
1992年 | 62篇 |
1991年 | 80篇 |
1990年 | 62篇 |
1989年 | 44篇 |
1988年 | 38篇 |
1987年 | 35篇 |
1986年 | 21篇 |
1985年 | 34篇 |
1984年 | 29篇 |
1983年 | 16篇 |
1982年 | 24篇 |
1981年 | 7篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1976年 | 2篇 |
1959年 | 1篇 |
1955年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
Although carbon fiber epoxy composite materials have excellent properties for structures, the joint in composite materials often reduces the efficiency of the composite structure because the joint is often the weakest area in the composite structure.
In this paper, the effects of the adhesive thickness and the adherend surface roughness on the static and fatigue strengths of adhesively-bonded tubular polygonal lap joints have been investigated by experimental methods. The dependencies of the static and fatigue strengths on the stacking sequences of the composite adherends were observed.
From the experimental investigations, it was found that the fatigue strength of the circular adhesively-bounded joints was quite dependent on the surface roughness of the adherends and that polygonal adhesively-bonded joints had better fatigue strength characteristics than circular adhesively-bonded joints. 相似文献
In this paper, the effects of the adhesive thickness and the adherend surface roughness on the static and fatigue strengths of adhesively-bonded tubular polygonal lap joints have been investigated by experimental methods. The dependencies of the static and fatigue strengths on the stacking sequences of the composite adherends were observed.
From the experimental investigations, it was found that the fatigue strength of the circular adhesively-bounded joints was quite dependent on the surface roughness of the adherends and that polygonal adhesively-bonded joints had better fatigue strength characteristics than circular adhesively-bonded joints. 相似文献
52.
准确测试陶瓷材料断裂韧性K1C的关键是预制具有原生裂纹的试样。本文以单边切口梁法测试K1C为基础,提出了一种简便而有效的陶瓷材料原生裂纹的预制方法-静态膨胀法。研究结果表明:静态膨胀法中裂纹的扩展是稳态的;通过调节影响微裂纹产生与扩展的多种因素,可以准确地控制裂纹扩展的深度,预制出合适的原生裂纹,为准确评价结构陶瓷的断裂韧性提供了一种有效可行的方法。 相似文献
53.
热膨胀硅橡胶在复合材料成型工艺中的应用 总被引:9,自引:0,他引:9
简要介绍了热膨胀硅橡胶的性能和特点,热膨胀模成型工艺的原理,并应用其研制了复合材料制件。热膨胀硅橡胶适于制造热膨胀芯模。 相似文献
54.
A study has been made of ‘combined’ joints consisting of mechanical fastening and adhesive bonding between rigid adherends. The mechanical characteristics of such ‘hybrid’ butt and lap shear joints have been derived by theoretical analysis. Results from experimental tests in combined joints giver reasonable agreement with the theoretical equations relating joint load to deformation. 相似文献
55.
56.
以TiO2 ZrO2 P2O5为复合成核剂,采用传统熔融冷却法获得了高ZnO含量的Li2O-A l2O3-SiO2系统的基础玻璃。通过差热分析确定了该玻璃的热处理条件、晶化性能,利用梯温炉实验、X射线衍射分析和扫描电镜对晶化试样的物相和微观结构进行了研究,讨论了热处理制度对玻璃的析晶及热膨胀系数的影响。研究结果表明:含10%(质量分数)ZnO的LAS系统样品玻璃最佳核化温度为(710±2)℃,玻璃的晶化活化能E为(275±2)kJ/mol,晶化指数n为3.11±0.2,样品玻璃在较低温度下失透,并且随着晶化温度升高,样品的热膨胀系数加大。 相似文献
57.
《Expert systems with applications》2014,41(16):7161-7170
The features extracted from the cardiac sound signals are commonly used for detection and identification of heart valve disorders. In this paper, we present a new method for classification of cardiac sound signals using constrained tunable-Q wavelet transform (TQWT). The proposed method begins with a constrained TQWT based segmentation of cardiac sound signals into heart beat cycles. The features obtained from heart beat cycles of separately reconstructed heart sounds and murmur can better represent the various types of cardiac sound signals than that from containing both. Therefore, heart sounds and murmur have been separated using constrained TQWT. Then the proposed novel raw feature set has been created by the parameters that have been optimized while constraining the output of TQWT together with that of extracted by using time-domain representation and Fourier–Bessel (FB) expansion of separated heart sounds and murmur. However, the adaptively selected features have been used to obtain the final feature set for subsequent classification of cardiac sound signals using least squares support vector machine (LS-SVM) with various kernel functions. The performance of the proposed method has been validated with publicly available datasets and the results have been compared with the existing short-time Fourier transform (STFT) based method. The proposed method shows higher percentage classification accuracy of 94.01 as compared to 93.53 of STFT based method. In comparison with STFT based method, it is noteworthy that the proposed method uses well defined and lower dimensionality of feature vector that can reduce the computational complexity. 相似文献
58.
59.
Walter Brockmann 《The Journal of Adhesion》1989,29(1):53-61
Adequate adhesion between metals and polymers is primarily the result of chemical bonds in the boundary layer. This region, however, is subject to degradation by moisture. Three modes of deterioration are observed. The first is a largely reversible weakening effect in the polymer layer near the metal oxide surface. The structure of this layer differs from that of the bulk and is influenced by the chemical and physical properties of the surface. The second is a slow transformation of the oxide by hydration and a diffusion of oxide constituents into the polymer. This process is irreversible and is influenced by the state of the surface and chemical properties of the polymer. The third is a fast deterioration of the oxide by primary corrosion usually initiating at an unprotected edge but occasionally arising within the body of a joint. 相似文献
60.