全文获取类型
收费全文 | 111174篇 |
免费 | 17817篇 |
国内免费 | 2784篇 |
专业分类
电工技术 | 4588篇 |
技术理论 | 6篇 |
综合类 | 4430篇 |
化学工业 | 29174篇 |
金属工艺 | 4269篇 |
机械仪表 | 5489篇 |
建筑科学 | 6861篇 |
矿业工程 | 2404篇 |
能源动力 | 3029篇 |
轻工业 | 11564篇 |
水利工程 | 1280篇 |
石油天然气 | 5321篇 |
武器工业 | 461篇 |
无线电 | 14240篇 |
一般工业技术 | 20321篇 |
冶金工业 | 4541篇 |
原子能技术 | 756篇 |
自动化技术 | 13041篇 |
出版年
2024年 | 301篇 |
2023年 | 1275篇 |
2022年 | 2119篇 |
2021年 | 3114篇 |
2020年 | 3563篇 |
2019年 | 4992篇 |
2018年 | 5224篇 |
2017年 | 5731篇 |
2016年 | 5798篇 |
2015年 | 6476篇 |
2014年 | 7169篇 |
2013年 | 9038篇 |
2012年 | 6933篇 |
2011年 | 7113篇 |
2010年 | 6718篇 |
2009年 | 6368篇 |
2008年 | 5818篇 |
2007年 | 5556篇 |
2006年 | 5393篇 |
2005年 | 4765篇 |
2004年 | 3589篇 |
2003年 | 3359篇 |
2002年 | 3094篇 |
2001年 | 2716篇 |
2000年 | 2850篇 |
1999年 | 2497篇 |
1998年 | 1817篇 |
1997年 | 1470篇 |
1996年 | 1432篇 |
1995年 | 1204篇 |
1994年 | 986篇 |
1993年 | 733篇 |
1992年 | 565篇 |
1991年 | 453篇 |
1990年 | 352篇 |
1989年 | 265篇 |
1988年 | 231篇 |
1987年 | 151篇 |
1986年 | 133篇 |
1985年 | 102篇 |
1984年 | 69篇 |
1983年 | 44篇 |
1982年 | 43篇 |
1981年 | 32篇 |
1980年 | 30篇 |
1979年 | 14篇 |
1977年 | 12篇 |
1976年 | 12篇 |
1975年 | 6篇 |
1970年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
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
102.
103.
管内覆丝网强化对流换热及阻力特性的实验研究 总被引:1,自引:1,他引:0
通过实验对管内覆丝网管进行了强迫对流换热和阻力特性研究。结果表明:管内覆丝网使换热明显增强,阻力也相应增长。菱形丝网对角线距离与平行边距离之比对换热效果有决定作用,丝网厚度对换热的影响比较小,而丝网网格的大小对换热几乎没有影响,在相同的泵功率和几何条件下,换热系数最大增加21%。 相似文献
104.
北京谱仪(BESⅡ)顶点探测器数据获取系统是北京谱仪数据获取系统的一部分,该子系统电子学采用快总线标准,本文描述了该系统的硬件结构和软件系统,软件包括快总线系统的微码软件和上层控制软件,该系统的死时间为1.5ns,对BESⅡ系统总死时间的贡献小于0.5ms。 相似文献
105.
Complements in serum and middle ear effusion were determined in 20 patients with secretory otitis media, and compared with those in the normal controls. The C5 and C1-INH in serum of the patients were significantly higher. On the contrary, C9 and B factor (Bf) were significantly lower, and the circulatory immunocomplex was also higher. In patients with secretory otitis media, the middle ear effusion levels of C3, C4 and C5 were significantly lower, and Bf and immunocomplex were significantly higher than those in serum. The results suggest that the ability of complements in clearing immunocomplex is low. Therefore, the immunocomplex may deposit in the mucosa of the middle ear. Thus the permeability of capillary will be increased, and the middle ear effusion occurs. 相似文献
106.
The purpose of this study was to analyze the symbolization of colors as cultural codes, based on costume colors. In order to study the significance of colors in cultural changes, we carried out a quantitative analysis and interpreted it from the perspective of cultural semiotics. The range of this study was focused on Korean costume colors, over diverse diachronic stages of Korean culture. For this study 1535 color samples were collected, measured with a spectrophotometer, and analyzed quantitatively according their diachronic stages of origin. As a result, red, blue, and yellow were found to be the most frequently used colors during the Chosun Dynasty, a period based on Confucianism. These colors acted as cultural codes with cultural significance. During the Modern times pink, light blue, and black increased in frequency and represented the reception of western culture, the changing sex role of women in society, and utilitarianism. In these days, neutral colors and grayish tones of all colors are the most significant colors of high frequency. The use of such colors is closely related to industrialization, mechanization, functionalism, and the changes of women's sex roles in the societies. They are used as cultural codes, especially to emphasize a rational and masculine image rather than a feminine image. © 2006 Wiley Periodicals, Inc. Col Res Appl, 32, 71–79, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20290 相似文献
107.
108.
A general model, based on double film theory, is developed to study absorption with chemical reactions. In the liquid film region, the model is a set of differential equations that describe the mass transfer accompanying several chemical reactions; the resolution of the system is achieved by the finite difference method using an implicit scheme combined with Newton's method. Continuity equations and equilibrium coefficients are exploited in the treatment of the bulk region, which is based on the Newton‐Raphson method; the results are used directly as boundary conditions in the liquid film equations. Maxwell‐Stefan equations have been used as a rigorous approach in this model. 相似文献
109.
110.
对不同能量、不同质量数、不同初始条件的入射束和有无空间电荷效应的离子束流在高梯度加速管中的传输进行了计算,并讨论了一些影响加速管聚焦作用的主要因素,计算结果与实际情况相符。 相似文献