全文获取类型
收费全文 | 221552篇 |
免费 | 25875篇 |
国内免费 | 19540篇 |
专业分类
电工技术 | 14418篇 |
技术理论 | 9篇 |
综合类 | 22580篇 |
化学工业 | 34247篇 |
金属工艺 | 11646篇 |
机械仪表 | 14045篇 |
建筑科学 | 15756篇 |
矿业工程 | 6642篇 |
能源动力 | 8184篇 |
轻工业 | 9844篇 |
水利工程 | 9562篇 |
石油天然气 | 9941篇 |
武器工业 | 2661篇 |
无线电 | 21909篇 |
一般工业技术 | 27323篇 |
冶金工业 | 7971篇 |
原子能技术 | 2440篇 |
自动化技术 | 47789篇 |
出版年
2024年 | 1064篇 |
2023年 | 3836篇 |
2022年 | 6778篇 |
2021年 | 7946篇 |
2020年 | 7888篇 |
2019年 | 7017篇 |
2018年 | 6544篇 |
2017年 | 8066篇 |
2016年 | 9111篇 |
2015年 | 9511篇 |
2014年 | 12748篇 |
2013年 | 13653篇 |
2012年 | 15156篇 |
2011年 | 17765篇 |
2010年 | 13711篇 |
2009年 | 14719篇 |
2008年 | 13830篇 |
2007年 | 15566篇 |
2006年 | 13547篇 |
2005年 | 11939篇 |
2004年 | 9702篇 |
2003年 | 8599篇 |
2002年 | 7023篇 |
2001年 | 5313篇 |
2000年 | 4775篇 |
1999年 | 3754篇 |
1998年 | 3073篇 |
1997年 | 2509篇 |
1996年 | 2344篇 |
1995年 | 1954篇 |
1994年 | 1684篇 |
1993年 | 1220篇 |
1992年 | 984篇 |
1991年 | 790篇 |
1990年 | 602篇 |
1989年 | 519篇 |
1988年 | 325篇 |
1987年 | 237篇 |
1986年 | 218篇 |
1985年 | 163篇 |
1984年 | 148篇 |
1983年 | 94篇 |
1982年 | 118篇 |
1981年 | 66篇 |
1980年 | 89篇 |
1979年 | 79篇 |
1978年 | 28篇 |
1977年 | 25篇 |
1976年 | 20篇 |
1974年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
H. L. Du S. R. Rose Z. D. Xiang P. K. Datta X. Y. Li 《Materialwissenschaft und Werkstofftechnik》2003,34(4):421-426
The oxidation/sulphidation behaviour of a Ti‐46.7Al‐1.9W‐0.5Si alloy with a TiAl3 diffusion coating was studied in an environment of H2/H2S/H2O at 850oC. The kinetic results demonstrate that the TiAl3 coating significantly increased the high temperature corrosion resistance of Ti‐46.7Al‐1.9W‐0.5Si. The SEM, EDX, XRD and TEM analysis reveals that the formation of an Al2O3 scale on the surface of the TiAl3‐coated sample was responsible for the enhancement of the corroison resistance. The Ti‐46.7Al‐1.9W‐0.5Si alloy was also modified by Nb ion implantation. The Nb ion implanted and as received sampels were subjected to cyclic oxidation in an open air at 800oC. The Nb ion implantation not only increased the oxidation resistance but also substantially improved the adhesion of scale to the substrate. 相似文献
82.
为了提高非稳定渗流计算的计算精度 ,通过数学分析得到了水位传导系数随时间变化时 ,一类非稳定渗流井流模型的半解析解 ,并进行了计算比较 相似文献
83.
84.
Si3N4 ceramic was jointed to itself using a filler alloy of Cu76.5Pd8.5Ti15, and the mechanical properties of the jointwere measured and analyzed. By using a filler alloy of Cu76.5Pd8.5Ti15, the SisN4/SisN4 joints were obtained bybrazing at 1373~1473 K f 相似文献
85.
From its foundation until 2004, ETRI has registered over 1,000 US patents. This letter analyzes the characteristics of these patents and addresses the explanatory factors affecting their citation counts. For explanatory variables, research team related variables, invention specific variables, and geographical domain related variables are suggested. Zero‐altered count data models are used to test the impact of independent variables. A key finding is that technological cumulativeness, the scale of invention, outputs in the electronic field, and the degree of dependence on the US technology domain positively affect the citation counts of ETRI‐invented US patents. The magnitude of international presence appears to negatively affect the citation counts of ETRI‐invented US patents. 相似文献
86.
串行和并行接口模式是A/D转换器诸多分类中的一种,但却是应用中器件选择的一个重要指标.在同样的转换分辨率及转换速度的前提下,不同的接口方式不但影响了电路结构,更重要的是将在高速数据采集的过程中对采样周期产生较大影响.本文通过12位串行ADC ADS7822和并行ADC ADS774与AT89C51的接口电路,给出二者采样时间的差异性. 相似文献
87.
业务支撑系统作为3G运营的重要组成,它的建设情况直接决定了电信运营商今后3G运营的成败,文章简单介绍了如何构建面向3G时代的业务支撑系统,对建设今后的业务支撑系统提供建议。 相似文献
88.
89.
The Intellectual Development of Science and Engineering Students. Part 2: Teaching to Promote Growth
As college students experience the challenges of their classes and extracurricular activities, they undergo a developmental progression in which they gradually relinquish their belief in the certainty of knowledge and the omniscience of authorities and take increasing responsibility for their own learning. At the highest developmental level normally seen in college students (which few attain before graduation), they display attitudes and thinking patterns resembling those of expert scientists and engineers, including habitually and skillfully gathering and analyzing evidence to support their judgments. This paper proposes an instructional model designed to provide a suitable balance of challenge and support to advance students to that level. The model components are (1) variety and choice of learning tasks; (2) explicit communication and explanation of expectations; (3) modeling, practice, and constructive feedback on high‐level tasks; (4) a student‐centered instructional environment; and (5) respect for students at all levels of development. 相似文献
90.