全文获取类型
收费全文 | 5581篇 |
免费 | 461篇 |
国内免费 | 314篇 |
专业分类
电工技术 | 264篇 |
综合类 | 343篇 |
化学工业 | 891篇 |
金属工艺 | 443篇 |
机械仪表 | 443篇 |
建筑科学 | 459篇 |
矿业工程 | 190篇 |
能源动力 | 168篇 |
轻工业 | 256篇 |
水利工程 | 128篇 |
石油天然气 | 308篇 |
武器工业 | 27篇 |
无线电 | 568篇 |
一般工业技术 | 692篇 |
冶金工业 | 421篇 |
原子能技术 | 50篇 |
自动化技术 | 705篇 |
出版年
2024年 | 13篇 |
2023年 | 96篇 |
2022年 | 181篇 |
2021年 | 251篇 |
2020年 | 182篇 |
2019年 | 138篇 |
2018年 | 154篇 |
2017年 | 160篇 |
2016年 | 133篇 |
2015年 | 178篇 |
2014年 | 280篇 |
2013年 | 328篇 |
2012年 | 333篇 |
2011年 | 358篇 |
2010年 | 331篇 |
2009年 | 302篇 |
2008年 | 281篇 |
2007年 | 288篇 |
2006年 | 298篇 |
2005年 | 268篇 |
2004年 | 174篇 |
2003年 | 196篇 |
2002年 | 216篇 |
2001年 | 202篇 |
2000年 | 160篇 |
1999年 | 175篇 |
1998年 | 137篇 |
1997年 | 132篇 |
1996年 | 94篇 |
1995年 | 88篇 |
1994年 | 46篇 |
1993年 | 44篇 |
1992年 | 33篇 |
1991年 | 22篇 |
1990年 | 14篇 |
1989年 | 22篇 |
1988年 | 12篇 |
1987年 | 12篇 |
1986年 | 9篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1979年 | 1篇 |
排序方式: 共有6356条查询结果,搜索用时 15 毫秒
1.
The capture of particles by charged droplets was simulated by considering the electrostatic interactions of droplet-droplet and droplet-particle. The results indicate that the electrostatic repulsion between droplets leads to a dynamic accumulation mode of particles. However, the droplet spacing has an insignificant effect on the capture efficiency when the electrostatic deposition predominates. The increase of droplet charge remarkably improves the capture efficiency, in which the capture of fine particles accounts for the largest proportion. Compared to the droplet charge, the droplet size shows a limited improvement in the capture efficiency. Reducing the droplet velocity prolongs the capture time instead of enhancing the capture capacity per unit time, thereby improving capture efficiency. 相似文献
3.
4.
5.
6.
7.
对一台火花点火式两缸天然气发动机进行了缸内示功图、进气压力波、空燃比、缸盖及活塞温度场和排放等项目的测试。试验和分析表明,两缸进气道中存在着明显的压力波动,波动程度取决于发动机工况。两缸混合气的质和量都不均匀,一缸空燃比偏浓,燃烧不完全,后燃倾向大;二缸空燃比较合适,燃烧过程较完善。两缸的尾气排放量相差不大。据此,可应用稀燃、快燃技术,以提高燃烧速度,改善燃烧过程;同时调整进气系统特性,将两缸混合气的质和量的不均匀性降到最低限度。 相似文献
8.
The changes of nitric oxide synthase (NOS) activity and nitrite level in rat brain regions after spatial learning were investigated. NOS activity was assayed by conversion of [3H]L-arginine to [3H]L-citrulline, and a sensitive fluorometric assay for quantification of nitrite was used. Compared with sham-trained rats, NOS activity and nitrite level in hippocampus and cortex, and also the nitrite level in cerebellum, was elevated significantly one day after rats had learnt a water-rewarded spatial alteration task. These results suggest a spatial memory-related changes of endogenous NO in rat brain, and support the idea that NO participates in learning and memory processes. 相似文献
9.
介绍了替代进口梳棉机测厚传感器集成电路分立元件的电路图,工作原理及特点。一年多的实际运行证明,电路参数达到了设计要求。 相似文献
10.
The transmembrane proteoglycan NG2 is able to interact both with components of the extracellular matrix and with the actin cytoskeleton. An examination of the distribution of NG2 during cell spreading suggests that NG2 can associate with two distinct types of actin-containing cytoskeletal structures, depending on the nature of the stimulus derived from the substratum. On fibronectin-coated dishes, cell surface NG2 associates exclusively with stress fibers developing within the cell. On poly-L-lysine-coated dishes, cell surface NG2 is associated with radial processes extending from the cell periphery. Spreading on fibronectin/poly-L-lysine mixtures, as well as on matrix components such as laminin, tenascin, and type VI collagen, produces cells with mosaic characteristics, i.e., NG2 is associated with both types of structures. NG2-positive radial processes are distinct from a second population of radial structures that contain fascin. NG2-positive extensions appear to be individual self-contained units (filopodia), whereas fascin is associated with actin ribs within sheets of membrane (lamellipodia). NG2- and fascin-positive structures are often localized to opposite poles of spreading cells, suggesting a possible role for the two classes of cellular extensions in the establishment of cell polarity during morphogenesis or migration. Time lapse imaging confirms the presence of lamellipodia on the leading edges of migrating cells, while numerous filopodia are present on trailing edges. 相似文献