全文获取类型
收费全文 | 341426篇 |
免费 | 25086篇 |
国内免费 | 13212篇 |
专业分类
电工技术 | 18610篇 |
技术理论 | 56篇 |
综合类 | 20646篇 |
化学工业 | 57508篇 |
金属工艺 | 19158篇 |
机械仪表 | 21780篇 |
建筑科学 | 26342篇 |
矿业工程 | 11316篇 |
能源动力 | 9985篇 |
轻工业 | 19776篇 |
水利工程 | 5645篇 |
石油天然气 | 23156篇 |
武器工业 | 2676篇 |
无线电 | 37454篇 |
一般工业技术 | 40481篇 |
冶金工业 | 18727篇 |
原子能技术 | 3355篇 |
自动化技术 | 43053篇 |
出版年
2024年 | 1338篇 |
2023年 | 5347篇 |
2022年 | 9195篇 |
2021年 | 12984篇 |
2020年 | 10121篇 |
2019年 | 8226篇 |
2018年 | 9406篇 |
2017年 | 10631篇 |
2016年 | 9494篇 |
2015年 | 12592篇 |
2014年 | 16323篇 |
2013年 | 19754篇 |
2012年 | 20844篇 |
2011年 | 23214篇 |
2010年 | 19938篇 |
2009年 | 19047篇 |
2008年 | 18696篇 |
2007年 | 18090篇 |
2006年 | 18881篇 |
2005年 | 16597篇 |
2004年 | 10691篇 |
2003年 | 9334篇 |
2002年 | 8326篇 |
2001年 | 7665篇 |
2000年 | 8168篇 |
1999年 | 9707篇 |
1998年 | 8166篇 |
1997年 | 6776篇 |
1996年 | 6365篇 |
1995年 | 5339篇 |
1994年 | 4381篇 |
1993年 | 3095篇 |
1992年 | 2495篇 |
1991年 | 1962篇 |
1990年 | 1504篇 |
1989年 | 1234篇 |
1988年 | 1021篇 |
1987年 | 684篇 |
1986年 | 538篇 |
1985年 | 348篇 |
1984年 | 246篇 |
1983年 | 205篇 |
1982年 | 196篇 |
1981年 | 130篇 |
1980年 | 132篇 |
1979年 | 68篇 |
1978年 | 33篇 |
1977年 | 38篇 |
1976年 | 55篇 |
1975年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A refined beam theory based on the refined plate theory 总被引:5,自引:0,他引:5
Summary Based on the refined plate theory, a refined theory of rectangular beams is derived by using the Papkovich-Neuber solution and Lur’e method without ad hoc assumptions. It is shown that the displacements and stresses of the beam can be represented by the angle of rotation and the deflection of the neutral surface. The solutions based on the new theory are the same as the exact solutions of elasticity theory. In three examples it is shown that the new theory provides as good or better results than Levinson’s beam theory when compared to those obtained from the linear theory of elasticity. 相似文献
992.
993.
This paper describes an experimental investigation into the performance and lubrication failure mechanism of precise angular-contact ball bearings treated with MoS2-sputtered film, etc. As an important executive component of various spacecrafts, there are some strict requirements on the lubrication performance of angular-contact ball bearing, but the related experimental data are rare to see in literatures. In this experiment, the lubrication performances of MoS2-sputtered ball bearing pairs were evaluated by using lifetime test as a main method, and the topographies and compositions of working surfaces were investigated through SEM, AES and EDS. The systematical experiment results reveal that the degradation and failure process of solid lubrication for such ball bearing is divided into three stages with different characters. A supposed failure mechanism has been proposed. An improved lubrication treatment based on above mechanism was conducted for the precise ball bearings, and a later test showed that long endurance life with more than 108 revolutions has been reached. 相似文献
994.
995.
996.
997.
Yufeng Su Hong Wang Guifu Ding Feng Cui Weiping Zhang Wenyuan Chen 《IEEE transactions on magnetics》2005,41(12):4380-4383
We describe the preparation of CoNiMnP-based permanent-magnet material using several sulfate and chloride solutions. We studied eight samples, and all the samples show vertical magnetic anisotropy. Sample8, which was electroplated from a low-concentration chloride solution and under external magnetic field, demonstrates the best magnetic properties with coercivity 2632 Oe, remanence 0.20 T, and maximum magnetic energy 10.185 kJ/m/sup 3/. An array structure can avoid the stress between the electroplated layer and the seed layer. The electroplated Co/sub 0.8/Ni/sub 0.1174/Mn/sub 0.0062/P/sub 0.0762/ permanent magnet has potential for bidirectional actuators in micro-electromechanical systems. 相似文献
998.
分析构建学习型组织与推动企业信息化的关系,提出企业通过构建学习型组织以推动企业信息化的措施。 相似文献
999.
从理想的英语测试体系及英语测试现状谈英语测试改革的必要性,从我校英语测试改革实践及成效论在英语测试中增加口试的可行性. 相似文献
1000.
Trace elements including REE (Rare Earth Elements) in fluid inclusions in Iherzolite, olivine, orthopyroxene, and clinopyroxene have been determined by heating-decrepitation and ICP-MS (Element Type Inductively Coupled Plasma-Mass Spectrometry) method. Normalized CO2 fluid/chondrite data show that mantle fluids are rich in REEs, especially LREEs (Light Rare Earth Elements), several times or dozen times higher than mantle rocks and mantle minerals. There are close relationships among the REE data of olivine, orthopyroxene, clinopyroxene and 1herzolite. Compared to the data of chemical dissolution method, it is believed that REE data obtained from heating-decrepitation and ICP-MS technique are contributed by CO2 fluid inclusions. About 60% (mass fraction) of tiny inclusions are observed not to be decrepitated above 1000℃, so REE data obtained are only contributed by decrepitated inclusions. Mantle fluids rich in LREE play an important role in mantle metasomatism, partial melting and mineralization. 相似文献