全文获取类型
收费全文 | 39610篇 |
免费 | 4848篇 |
国内免费 | 3026篇 |
专业分类
电工技术 | 4586篇 |
技术理论 | 2篇 |
综合类 | 4153篇 |
化学工业 | 5524篇 |
金属工艺 | 1309篇 |
机械仪表 | 2267篇 |
建筑科学 | 3529篇 |
矿业工程 | 1221篇 |
能源动力 | 1812篇 |
轻工业 | 2012篇 |
水利工程 | 1291篇 |
石油天然气 | 2939篇 |
武器工业 | 583篇 |
无线电 | 3535篇 |
一般工业技术 | 4396篇 |
冶金工业 | 1559篇 |
原子能技术 | 752篇 |
自动化技术 | 6014篇 |
出版年
2024年 | 189篇 |
2023年 | 613篇 |
2022年 | 1286篇 |
2021年 | 1566篇 |
2020年 | 1511篇 |
2019年 | 1184篇 |
2018年 | 1149篇 |
2017年 | 1417篇 |
2016年 | 1622篇 |
2015年 | 1705篇 |
2014年 | 2407篇 |
2013年 | 2659篇 |
2012年 | 2874篇 |
2011年 | 3254篇 |
2010年 | 2381篇 |
2009年 | 2494篇 |
2008年 | 2237篇 |
2007年 | 2650篇 |
2006年 | 2316篇 |
2005年 | 1939篇 |
2004年 | 1561篇 |
2003年 | 1390篇 |
2002年 | 1215篇 |
2001年 | 990篇 |
2000年 | 838篇 |
1999年 | 693篇 |
1998年 | 581篇 |
1997年 | 480篇 |
1996年 | 430篇 |
1995年 | 344篇 |
1994年 | 309篇 |
1993年 | 186篇 |
1992年 | 184篇 |
1991年 | 132篇 |
1990年 | 133篇 |
1989年 | 109篇 |
1988年 | 101篇 |
1987年 | 60篇 |
1986年 | 37篇 |
1985年 | 32篇 |
1984年 | 47篇 |
1983年 | 21篇 |
1982年 | 26篇 |
1981年 | 19篇 |
1980年 | 13篇 |
1964年 | 10篇 |
1961年 | 8篇 |
1960年 | 9篇 |
1959年 | 8篇 |
1955年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
Christopher Higgins 《Canadian Metallurgical Quarterly》2004,9(6):599-605
Concrete filled grid bridge decks exhibit orthogonal elastic properties and significant two-way bending action enabling orthotropic plate theory to determine structural response for these elements. Current American Association of State Highway and Transportation Officials load and resistance factor design (LRFD) specifications employ an orthotropic plate model to predict live load moment in concrete filled grid bridge decks but provide no guidance for computing displacement, a potentially important serviceability consideration. This paper presents equations to approximate the maximum deflection in concrete filled grid bridge decks based on orthotropic plate theory, multiple patch loads, LRFD design truck and tandem load cases, the influence of multiple spans, and the two most common deck orientations. 相似文献
133.
134.
135.
136.
We report improvement of emission efficiency in polymer light-emitting devices (PLEDs) employing phosphorescent polymers. A hole-blocking layer was inserted between the emissive layer and the cathode to enhance recombination efficiency for the injected holes and electrons. Aluminum(III)bis(2-methyl-8-quinolinato)4-phenylphenolato (BAlq) was used for the hole-blocking layer. The resultant PLEDs exhibited significant improvement of emission efficiency. The respective external quantum efficiencies for red, green and blue PLEDs were 6.6, 11 and 6.9%. These values are very high compared with those based on conventional fluorescent polymers. 相似文献
137.
We present a fictitious domain decomposition method for the fast solution of acoustic scattering problems characterized by a partially axisymmetric sound‐hard scatterer. We apply this method to the solution of a mock‐up submarine problem, and highlight its computational advantages and intrinsic parallelism. A key component of our method is an original idea for addressing a Neumann boundary condition in the general framework of a fictitious domain method. This idea is applicable to many other linear partial differential equations besides the Helmholtz equation. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
138.
脆断事故的原因分析和预防措施 总被引:1,自引:0,他引:1
戚国胜 《南方冶金学院学报》2002,23(1):28-33
分析高强度材料和大型工程结构元件发生低应力脆性断裂的原因及条件,指出传统强度设计理论的局限性,从设计和工艺上提出防止发生低应力脆断事故的具体措施,给使用高强度材料和设计大型工程结构元件时提供参考。 相似文献
139.
Beck J. Gayle; Novy Diane M.; Diefenbach Gretchen J.; Stanley Melinda A.; Averill Patricia M.; Swann Alan C. 《Canadian Metallurgical Quarterly》2003,15(2):184
To examine affect and cognition in differentiating anxiety and depression, 83 older participants with generalized anxiety disorder completed the Cognitive Checklist (CCL) and the Positive and Negative Affect Schedule (PANAS). A 3-factor solution was found for the PANAS: positive affect (PA), anxiety and anger (Negative Affect 1 [NA-1]), and guilt and shame (Negative Affect 2 [NA-2]). A 2-factor structure was noted for the CCL. Correlations with anxiety and depression measures suggested that the CCL Depression (CCL-D) subscale showed stronger correlations with depression, whereas the CCL Anxiety subscale did not uniquely correlate with anxiety. The NA-1 subscale correlated positively with measures of depression and anxiety, whereas the PA subscale showed negative correlations. Hierarchical regression suggested that the CCL-D subscale was a significant predictor of self-reported depression. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
140.