全文获取类型
收费全文 | 41291篇 |
免费 | 4066篇 |
国内免费 | 2888篇 |
专业分类
电工技术 | 1794篇 |
综合类 | 3678篇 |
化学工业 | 6205篇 |
金属工艺 | 2144篇 |
机械仪表 | 1698篇 |
建筑科学 | 4833篇 |
矿业工程 | 1757篇 |
能源动力 | 1609篇 |
轻工业 | 2975篇 |
水利工程 | 1371篇 |
石油天然气 | 2220篇 |
武器工业 | 445篇 |
无线电 | 5135篇 |
一般工业技术 | 6188篇 |
冶金工业 | 2074篇 |
原子能技术 | 942篇 |
自动化技术 | 3177篇 |
出版年
2024年 | 160篇 |
2023年 | 655篇 |
2022年 | 1164篇 |
2021年 | 1390篇 |
2020年 | 1406篇 |
2019年 | 1318篇 |
2018年 | 1128篇 |
2017年 | 1475篇 |
2016年 | 1460篇 |
2015年 | 1573篇 |
2014年 | 2333篇 |
2013年 | 2449篇 |
2012年 | 2792篇 |
2011年 | 3062篇 |
2010年 | 2345篇 |
2009年 | 2431篇 |
2008年 | 2278篇 |
2007年 | 2719篇 |
2006年 | 2450篇 |
2005年 | 2029篇 |
2004年 | 1757篇 |
2003年 | 1543篇 |
2002年 | 1358篇 |
2001年 | 1067篇 |
2000年 | 1008篇 |
1999年 | 793篇 |
1998年 | 634篇 |
1997年 | 592篇 |
1996年 | 492篇 |
1995年 | 419篇 |
1994年 | 361篇 |
1993年 | 316篇 |
1992年 | 237篇 |
1991年 | 200篇 |
1990年 | 172篇 |
1989年 | 145篇 |
1988年 | 105篇 |
1987年 | 70篇 |
1986年 | 50篇 |
1985年 | 47篇 |
1984年 | 40篇 |
1983年 | 33篇 |
1982年 | 32篇 |
1981年 | 22篇 |
1980年 | 23篇 |
1979年 | 25篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1959年 | 9篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
动态多目标决策问题的灰色分析方法 总被引:2,自引:0,他引:2
将用于固定时间截面下静态多目标决策的灰色关联理论推广到动态情形,引入局部理想最优效果和整体理想最优效果的概念,提出一种新型的动态多目标决策问题的灰色关联模型,并通过算例说明该方法的合理可行性。 相似文献
92.
The fracture toughness of brittle thermoset resins could be improved significantly by perfectly bonded tough, short fibers through both crack trapping and bridging effects. In this paper, the crack trapping effect was studied through the analysis of the change of strain energy associated with the crack propagation across a regular array of fibers, and the bridging effect was discussed based on the Andersson–Bergkvist model. The fracture resistance increases with the fiber volume fraction, and is independent of the elastic properties of the matrix, the crack length, and the cross-sectional diameter of the fibers. 相似文献
93.
An advanced learning system for interactive simulation of patient cases (ISP) is described. The system was designed to meet specific pedagogical needs where student activation and problem orientation were two of the key issues. The system includes features such as video based illness history-taking function using free text input, highly interactive physiological examination procedures, extensive laboratory tests and detailed user feedback. The system was constructed mainly in Authorware Professional, starting more than 10 years ago, and it is now available in refined versions in different languages. Twelve pedagogical and three technical features were initially defined for the project. All of these aims were fulfilled. The ISP system has been successfully used in education, and in international collaboration, including three applicability field tests. The system is also a powerful research tool for studying for instance medical decision-making. 相似文献
94.
Thecokesolutionlossreactionisoneofthemostimportanteffectsresultingincokepulverizinginblastfurnace .Thefactorswhichaffectreactionincludecokeporestructure ,micro crystalstructureonporewall ,thecontentandconstituentofminer als ,etc .Amongthesefactors ,theconstituentofmineralsisemphasizedallovertheworldinrecentyears .Buttheemphasisofmoststudieswasputontheeffectofalkalimetals (K ,Na)oncokesolutionlossreactionandtheeffectofotherelementswassel domreported[1-5] .Theeffectofthirteenmineralsoncokesolut… 相似文献
95.
T. YAMAMOTO M. IWATA M. SAKANE Y. TSUKADA H. NISHIMURA 《Fatigue & Fracture of Engineering Materials & Structures》2007,30(5):376-386
This paper describes the creep‐fatigue life of Sn–8Zn–3Bi under push–pull loading. Creep‐fatigue tests were carried out using Sn–8Zn–3Bi specimens in fast–fast, fast–slow, slow–fast, slow–slow and hold–time strain waveforms. Creep‐fatigue lives in the slow–slow and hold‐time waveforms showed a small reduction from the fast–fast lives but those in the slow–fast and fast–slow waveforms showed a significant reduction from the fast–fast lives. Conventional creep‐fatigue life prediction methods were applied to the experimental data and the applicability of the methods was discussed. Creep‐fatigue characteristics of Sn–8Zn–3Bi were compared with those of Sn–3.5Ag and Sn–37Pb. 相似文献
96.
This paper presents a semianalytical method for the prediction of interlaminar stresses and displacements near the free edges and ply cracks in general angle-ply laminates subjected to biaxial extensions and/or in plane shear deformation. The method is based on a state space representation of the three-dimensional equations of elasticity. Numerical solutions are obtained by using layer refinement in the through thickness direction and Fourier series expansion in the other directions. By this approach, an angle-ply laminate may be composed of an arbitrary number of monoclinic layers and each layer may have different material property and thickness. This method guarantees continuous fields of all interlaminar stresses across interfaces between material layers. Numerical results are compared with those obtained from other methods. It is found that the theory provides a satisfactory approximation to the stress singularities near the free edges and ply cracks. Numerical solutions for antisymmetric laminates under extension and general laminates under shearing are new in the literature and can be used as benchmarks for validating new models. 相似文献
97.
98.
99.
100.
新型保温材料—炭化稻壳在连铸生产中的应用效果 总被引:3,自引:0,他引:3
对新型保温材料──炭化稻壳的理化指标及其保温性能进行了阐述。在连铸生产中采用炭化稻壳做保温剂可取得显著的经济效益,是理想的保温材料。 相似文献