全文获取类型
收费全文 | 274627篇 |
免费 | 20940篇 |
国内免费 | 12012篇 |
专业分类
电工技术 | 16546篇 |
技术理论 | 8篇 |
综合类 | 18088篇 |
化学工业 | 38601篇 |
金属工艺 | 16597篇 |
机械仪表 | 16193篇 |
建筑科学 | 18372篇 |
矿业工程 | 6882篇 |
能源动力 | 6898篇 |
轻工业 | 18087篇 |
水利工程 | 5944篇 |
石油天然气 | 10312篇 |
武器工业 | 2211篇 |
无线电 | 32150篇 |
一般工业技术 | 35322篇 |
冶金工业 | 10201篇 |
原子能技术 | 2464篇 |
自动化技术 | 52703篇 |
出版年
2024年 | 832篇 |
2023年 | 3076篇 |
2022年 | 6232篇 |
2021年 | 8739篇 |
2020年 | 6572篇 |
2019年 | 5041篇 |
2018年 | 19524篇 |
2017年 | 19478篇 |
2016年 | 15287篇 |
2015年 | 9225篇 |
2014年 | 11022篇 |
2013年 | 13001篇 |
2012年 | 17917篇 |
2011年 | 24719篇 |
2010年 | 22366篇 |
2009年 | 18847篇 |
2008年 | 19971篇 |
2007年 | 20220篇 |
2006年 | 11701篇 |
2005年 | 10364篇 |
2004年 | 7421篇 |
2003年 | 6597篇 |
2002年 | 5854篇 |
2001年 | 4776篇 |
2000年 | 3949篇 |
1999年 | 3229篇 |
1998年 | 2123篇 |
1997年 | 1721篇 |
1996年 | 1610篇 |
1995年 | 1351篇 |
1994年 | 1101篇 |
1993年 | 698篇 |
1992年 | 568篇 |
1991年 | 410篇 |
1990年 | 326篇 |
1989年 | 269篇 |
1988年 | 191篇 |
1987年 | 130篇 |
1986年 | 107篇 |
1985年 | 52篇 |
1984年 | 45篇 |
1981年 | 48篇 |
1980年 | 47篇 |
1968年 | 50篇 |
1966年 | 47篇 |
1965年 | 45篇 |
1959年 | 46篇 |
1958年 | 38篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
52.
Chenxu Liu Shuguang Zhang Ruonan Ji Peng Wang Jin Zhang Yu Tian Yonggang Meng Yedong He 《Ceramics International》2019,45(4):4747-4755
Semiconductor particles doped Al2O3 coatings were prepared by cathode plasma electrolytic deposition in Al(NO3)3 electrolyte dispersed with SiC micro- and nano-particles (average particle sizes of 0.5–1.7?µm and 40?nm respectively). The effects of the concentrations and particle sizes of the SiC on the microstructures and tribological performances of the composite coatings were studied. In comparison with the case of dispersing with SiC microparticles, the dispersion of SiC nanoparticles in the coatings was more uniform. When the concentration of SiC nanoparticles was 5?g/L, the surface roughness of the composite coating was reduced by 63%, compared with that of the unmodified coating. Friction results demonstrated that the addition of 5?g/L SiC nanoparticles reduced the friction coefficient from 0.60 to 0.38 and decreased the wear volume under dry friction. The current density and bath voltage were measured to analyze the effects of SiC particles on the deposition process. The results showed that the SiC particles could alter the electrical behavior of the coatings during the deposition process, weaken the bombardment of the plasma, and improve the structures of the coatings. 相似文献
53.
济阳坳陷下古生界潜山油气藏特征及成藏模式 总被引:1,自引:1,他引:0
济阳坳陷下古生界潜山具有多样性、复杂性的特点,潜山差异性的形成演化、油气成藏主控因素和控藏模式不明确,严重制约了该区潜山油气勘探。在潜山分类的基础上,综合利用系统恢复、分类对比和典型解剖等方法,揭示了济阳坳陷下古生界不同类型潜山的形成演化过程和油气成藏主控因素差异性,分类建立了油气成藏模式。研究表明,济阳坳陷下古生界主要发育高位新盖侵蚀残丘潜山、中位古盖拉张断块潜山、中位新古盖拉张剪切断块潜山、中位中古盖挤压拉张断块潜山和低位古盖拉张滑脱断块潜山5种潜山类型。不同类型潜山的形成演化和油气成藏各具特色,其中,高位新盖侵蚀残丘潜山的发育受隆升、侵蚀作用控制,油气成藏主要受控于油源和盖层条件,表现为"单向供烃、砂体-不整合岩溶体联合输导、残丘控藏"的成藏模式;中位古盖拉张断块潜山的发育受掀斜、断裂作用控制,油气成藏主要受控于储集条件,表现为"单向供烃、顺向断层输导、反向断层控藏"的成藏模式;中位新古盖拉张剪切断块潜山的发育受反转、翘倾和走滑切割作用控制,油气成藏主要受控于输导条件,表现为"多源供烃、断溶体立体输导、断裂控藏"的成藏模式;中位中古盖挤压拉张断块潜山的形成受强烈挤压、拉张滑脱作用控制,油气成藏主要受控于储集条件,表现为"多源供烃、断缝体输导、断褶控藏"的成藏模式;低位古盖拉张滑脱断块潜山的形成受强烈拉张滑脱作用控制,油气成藏主要受控于输导条件,表现为"顶部供烃、断缝体输导、断裂控藏"的成藏模式。 相似文献
54.
Rui ZHAO Weikai LI Tian WANG Ke ZHAN Zheng YANG Ya YAN Bin ZHAO Junhe YANG 《材料科学前沿(英文版)》2020,14(2):188
Effective thermal management of electronic integrated devices with high powder density has become a serious issue, which requires materials with high thermal conductivity (TC). In order to solve the problem of weak bonding between graphite and Cu, a novel Cu/graphite film/Cu sandwich composite (Cu/GF/Cu composite) with ultrahigh TC was fabricated by electro-deposition. The micro-riveting structure was introduced to enhance the bonding strength between graphite film and deposited Cu layers by preparing a rectangular array of micro-holes on the graphite film before electro-deposition. TC and mechanical properties of the composites with different graphite volume fractions and current densities were investigated. The results showed that the TC enhancement generated by the micro-riveting structure for Cu/GF/Cu composites at low graphite content was more effective than that at high graphite content, and the strong texture orientation of deposited Cu resulted in high TC. Under the optimizing preparing condition, the highest in-plane TC reached 824.3 W·m−1·K−1, while the ultimate tensile strength of this composite was about four times higher than that of the graphite film. 相似文献
55.
文章主要研究用水浸法提取落葵浆果天然染料及研究浸提液对羊毛织物的染色性能。以水为提取剂提取落葵浆果天然染料,探讨提取工艺中料液比、提取温度及时间等因素对落葵浆果天然染料提取效果的影响。研究结果表明,落葵浆果水浸提法优化工艺为:料液比1∶20、提取温度70℃、提取时间30 min。落葵浆果天然染料可以对羊毛织物进行染色,媒染染色与直接染色相比,染色深度深且会呈现不同的颜色。由于媒染剂的络合作用,媒染染色色牢度比直接染色普遍高1~2级。 相似文献
56.
57.
58.
The fracture behaviour and morphologies of high-strength boron steel were investigated at different temperatures at a constant strain rate of 0.1 s-1 based on isothermal tensile tests. Fracture mechanisms were also analyzed based on the relationship between microstructure transformation and continuous cooling transformation(CCT) curves. It is found that 1) fractures of the investigated steel at high temperatures are dimple fractures; 2) the deformation of high-strength boron steel at high temperatures accelerates diffusion transformations; thus, to obtain full martensite, a higher cooling rate is needed; and 3) the investigated steel has the best plasticity when the deformation temperature is 750 °C. 相似文献
59.
A contact layer element for large deformations 总被引:1,自引:0,他引:1
60.
Lü Qing Xu Bin Yu Yang Zhan Wei Zhao Yu Zheng Jun Ji Jian 《Bulletin of Engineering Geology and the Environment》2021,80(8):6513-6525
Bulletin of Engineering Geology and the Environment - Many uncertainties exist in pile-stabilized slopes which make their design substantially complicated. In this paper, a first-order reliability... 相似文献