全文获取类型
收费全文 | 130383篇 |
免费 | 10956篇 |
国内免费 | 5673篇 |
专业分类
电工技术 | 7407篇 |
技术理论 | 16篇 |
综合类 | 8656篇 |
化学工业 | 22018篇 |
金属工艺 | 6981篇 |
机械仪表 | 7739篇 |
建筑科学 | 10703篇 |
矿业工程 | 3633篇 |
能源动力 | 3721篇 |
轻工业 | 9222篇 |
水利工程 | 2427篇 |
石油天然气 | 8019篇 |
武器工业 | 964篇 |
无线电 | 14981篇 |
一般工业技术 | 16110篇 |
冶金工业 | 6443篇 |
原子能技术 | 1389篇 |
自动化技术 | 16583篇 |
出版年
2024年 | 521篇 |
2023年 | 2145篇 |
2022年 | 3719篇 |
2021年 | 5167篇 |
2020年 | 4028篇 |
2019年 | 3305篇 |
2018年 | 3817篇 |
2017年 | 4130篇 |
2016年 | 3895篇 |
2015年 | 4932篇 |
2014年 | 6414篇 |
2013年 | 7450篇 |
2012年 | 8258篇 |
2011年 | 8987篇 |
2010年 | 7652篇 |
2009年 | 7275篇 |
2008年 | 7184篇 |
2007年 | 6877篇 |
2006年 | 6741篇 |
2005年 | 5875篇 |
2004年 | 4170篇 |
2003年 | 3713篇 |
2002年 | 3340篇 |
2001年 | 3106篇 |
2000年 | 3300篇 |
1999年 | 3728篇 |
1998年 | 3044篇 |
1997年 | 2532篇 |
1996年 | 2385篇 |
1995年 | 2043篇 |
1994年 | 1737篇 |
1993年 | 1232篇 |
1992年 | 965篇 |
1991年 | 723篇 |
1990年 | 638篇 |
1989年 | 528篇 |
1988年 | 388篇 |
1987年 | 258篇 |
1986年 | 211篇 |
1985年 | 139篇 |
1984年 | 102篇 |
1983年 | 66篇 |
1982年 | 83篇 |
1981年 | 55篇 |
1980年 | 46篇 |
1979年 | 16篇 |
1977年 | 9篇 |
1976年 | 14篇 |
1974年 | 11篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
介绍了北营公司X70配套埋弧焊丝用H08D盘条的开发研制情况.其生产工艺的关键点为:转炉采用“双渣法除磷”,脱氧合金化在转炉和LF炉两个阶段完成,连铸采用结晶器电磁搅拌及末端电磁搅拌、恒定拉速;盘条采用控冷控轧及轧后延迟型斯太尔摩冷却工艺等措施.生产的成品盘条成分、力学性能、金相组织等指标均满足客户拉拔工艺要求. 相似文献
82.
83.
Shuang Shao Yong Liu Chun-Shui Xu Ying-Xuan Xu Bin Wu Xiao-Shu Zeng Xian-Feng Lu Xiang-Jie Yang 《金属学报(英文版)》2015,(1):7-14
The microstructure and mechanical properties of Mg–6Zn–1Y and Mg–6Zn–3Y(wt%) alloys under different cooling rates were investigated. The results show that the second dendrite arm spacing(SDAS) of Mg–6Zn–1Y and Mg–6Zn–3Y is reduced by 32 and 30% with increasing cooling rates(Rc) from 10.2 to 23 K/s, which can be predicted using a empirical model of SDAS=68 R 0:45:45cand SDAS=73 R 0c, respectively. The compressive strength of both alloys increases with increasing the cooling rate, which is attributed to the increase of volume fraction(Vf) of secondary phases under high cooling rate. The interaction of the cooling rate and component with SDAS has been theoretically analyzed using interdependence theory. 相似文献
84.
Multicellular tumor spheroid models (MCTS) are often coined as 3D in vitro models that can mimic the microenvironment of tissues. MCTS have gained increasing interest in the nano‐biotechnology field as they can provide easily accessible information on the performance of nanoparticles without using animal models. Considering that many countries have put restrictions on animals testing, which will only tighten in the future as seen by the recent developments in the Netherlands, 3D models will become an even more valuable tool. Here, an overview on MCTS is provided, focusing on their use in cancer research as most nanoparticles are tested in MCTS for treatment of primary tumors. Thereafter, various types of nanoparticles—from self‐assembled block copolymers to inorganic nanoparticles, are discussed. A range of physicochemical parameters including the size, shape, surface chemistry, ligands attachment, stability, and stiffness are found to influence nanoparticles in MCTS. Some of these studies are complemented by animal studies confirming that lessons from MCTS can in part predict the behaviour in vivo. In summary, MCTS are suitable models to gain additional information on nanoparticles. While not being able to replace in vivo studies, they can bridge the gap between traditional 2D in vitro studies and in vivo models. 相似文献
85.
Jianmou Lu Yanli Huang Shunyan Ren 《International Journal of Control, Automation and Systems》2020,18(5):1250-1263
This paper investigates the general decay synchronization and general decay H∞ synchronization problems of multi-weighted coupled reaction-diffusion 相似文献
86.
为了给海面溢油污染识别检测提供理论基础,根据菲涅尔反射公式的偏振反射系数,结合偏振双向反射率因子和粗糙海面的概率密度分布函数,建立了完善的pBRDF模型,仿真在不同太阳入射角度、不同探测器观测角度以及不同海面风速风向等条件下海水和油膜的偏振反射分布函数。结果表明:海水和油膜太阳天顶角为53°和56°时P偏振反射率分别为1.0×10^-5和2.5×10^-5,S偏振反射率随着太阳天顶角的增加而增加;海面风速越大偏振反射率峰值越小;海面风向只改变pBRDF的空间位置;海水和油膜线偏振度空间分布有明显差异。搭建实验平台相机以40°拍摄时,得出海水和油膜的线偏振度分别在0.2~0.4, 0.5~0.7之间,同时表明利用偏振探测获取目标场景的偏振度和偏振角图可提高图像质量。 相似文献
87.
88.
Yu Zhang Xiaofei Dai Haonan Jin Chaoxin Man Yujun Jiang 《Journal of dairy science》2021,104(4):4023-4032
This study aimed to predict the optimal carbon source for higher production of exopolysaccharides (EPS) by Lactobacillus paracasei TD 062, and to evaluate the effect of this carbon source on the production and monosaccharide composition of EPS. We evaluated the EPS production capacity of 20 strains of L. paracasei under the same conditions. We further investigated L. paracasei TD 062, which showed the highest EPS-producing activity (0.609 g/L), by examining the associated biosynthesis pathways for EPS. Genomics revealed that fructose, mannose, trehalose, glucose, galactose, and lactose were carbon sources that L. paracasei TD 062 could use to produce EPS. We identified an EPS synthesis gene cluster that could participate in transport, export, and sugar chain synthesis, and generate 6 sugar nucleotides. Experimental results showed that the sugar content of the EPS produced using fermentation with the optimized carbon source (fructose, mannose, trehalose, glucose, galactose, and lactose) increased by 115%. Furthermore, use of the optimized carbon source changed the monosaccharide content of the associated EPS. The results of enzyme activity measurements showed significant increases in the activity of 2 key enzymes involved in the glycoside synthesis pathway. Our study revealed that optimizing the carbon source provided for fermentation not only increased the production of EPS, but also affected the composition of the monosaccharides by increasing enzyme activity in the underlying synthesis pathways, suggesting an important role for carbon source in the production of EPS by L. paracasei TD 062. 相似文献
89.
Jialong Tian M. Babar Shahzad Wei Wang Lichang Yin Zhouhua Jiang Ke Yang 《材料科学技术学报》2018,34(9):1671-1675
The effect of Co addition on the formation of Ni-Ti clusters in maraging stainless steel was studied by three dimensional atom probe (3DAP) and first-principles calculation. The cluster analysis based on the maximum separation approach showed an increase in size but a decrease in density of Ni-Ti clusters with increasing the Co content. The first-principles calculation indicated weaker Co-Ni (Co-Ti) interactions than Co-Ti (Fe-Ti) interactions, which should be the essential reason for the change of distribution characteristics of Ni-Ti clusters in bcc Fe caused by Co addition. 相似文献
90.