全文获取类型
收费全文 | 7158篇 |
免费 | 558篇 |
国内免费 | 301篇 |
专业分类
电工技术 | 448篇 |
技术理论 | 1篇 |
综合类 | 575篇 |
化学工业 | 231篇 |
金属工艺 | 554篇 |
机械仪表 | 526篇 |
建筑科学 | 1589篇 |
矿业工程 | 385篇 |
能源动力 | 162篇 |
轻工业 | 79篇 |
水利工程 | 812篇 |
石油天然气 | 235篇 |
武器工业 | 42篇 |
无线电 | 611篇 |
一般工业技术 | 461篇 |
冶金工业 | 154篇 |
原子能技术 | 43篇 |
自动化技术 | 1109篇 |
出版年
2024年 | 14篇 |
2023年 | 62篇 |
2022年 | 157篇 |
2021年 | 178篇 |
2020年 | 186篇 |
2019年 | 152篇 |
2018年 | 126篇 |
2017年 | 171篇 |
2016年 | 198篇 |
2015年 | 229篇 |
2014年 | 572篇 |
2013年 | 483篇 |
2012年 | 607篇 |
2011年 | 605篇 |
2010年 | 462篇 |
2009年 | 467篇 |
2008年 | 442篇 |
2007年 | 481篇 |
2006年 | 411篇 |
2005年 | 336篇 |
2004年 | 262篇 |
2003年 | 266篇 |
2002年 | 229篇 |
2001年 | 182篇 |
2000年 | 146篇 |
1999年 | 111篇 |
1998年 | 105篇 |
1997年 | 76篇 |
1996年 | 66篇 |
1995年 | 42篇 |
1994年 | 43篇 |
1993年 | 36篇 |
1992年 | 25篇 |
1991年 | 13篇 |
1990年 | 12篇 |
1989年 | 15篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 1篇 |
排序方式: 共有8017条查询结果,搜索用时 15 毫秒
1.
Madhab Chandra Tripathy Debasmita Mondal Karabi Biswas Siddhartha Sen 《International Journal of Circuit Theory and Applications》2015,43(6):776-792
The present work reports the realization of an analog fractional‐order phase‐locked loop (FPLL) using a fractional capacitor. The expressions for bandwidth, capture range, and lock range of the FPLL have been derived analytically and then compared with the experimental observations using LM565 IC. It has been observed that bandwidth and capture range can be extended by using FPLL. It has also been found that FPLL can provide faster response and lower phase error at the time of switching compared to its integer‐order counterpart. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
2.
Hai Huang Haichao An Haibo Ma Shenyan Chen 《International journal for numerical methods in engineering》2019,117(3):291-315
This work presents an engineering method for optimizing structures made of bars, beams, plates, or a combination of those components. Corresponding problems involve both continuous (size) and discrete (topology) variables. Using a branched multipoint approximate function, which involves such mixed variables, a series of sequential approximate problems are constructed to make the primal problem explicit. To solve the approximate problems, genetic algorithm (GA) is utilized to optimize discrete variables, and when calculating individual fitness values in GA, a second-level approximate problem only involving retained continuous variables is built to optimize continuous variables. The solution to the second-level approximate problem can be easily obtained with dual methods. Structural analyses are only needed before improving the branched approximate functions in the iteration cycles. The method aims at optimal design of discrete structures consisting of bars, beams, plates, or other components. Numerical examples are given to illustrate its effectiveness, including frame topology optimization, layout optimization of stiffeners modeled with beams or shells, concurrent layout optimization of beam and shell components, and an application in a microsatellite structure. Optimization results show that the number of structural analyses is dramatically decreased when compared with pure GA while even comparable to pure sizing optimization. 相似文献
3.
With the advent of future vehicles, passengers expect to travel in comfort, and the free leg space between facing-seats could be an issue due to the unsuitability for all people, according to their anthropometric variability. A previous investigation survey showed the need to increase the leg-space between facing seats and, if installed, to improve the surface of the table placed in between. So, four different distances between seat-pans front edges of facing seats have been set-up and tested (44 cm, 51 cm, 58 cm, 65 cm) with a table in between. 13 couples of participants with different heights took part to experiments. The aim was to investigate the relationship between facing-seat distances and passenger wellbeing in terms of postural comfort and social interaction. Postural comfort has been analysed through optical tracking (for postural angles overtime) and questionnaires (perceived comfort). Social interaction feelings have been investigated with questionnaires. Experiment results showed the suitable distance could be 51 cm keeping the same table surface; otherwise, the 65 cm one could be ideal changing the table surface.Relevance to industryWith the advent of autonomous driving, vehicle manufacturers and designers are working hard to define new paradigms of public transportation in terms of seat layout, passenger wellbeing and interiors’ design. This paper contributes to increasing the general knowledge on the effects of distance between facing seats on postural comfort and social interaction. 相似文献
4.
5.
对静态随机存储器(SRAM)全定制设计过程中的版图设计工作量大、重复性强的问题进行了分析,并在此基础上提出了一种新的应用于SRAM设计的快速综合技术。这种技术充分利用SRAM电路重复单元多的特点,在设计过程中尽可能把电路版图的硬件设计转换为使用软件来实现,节省了大量的版图设计和验证的时间,从而提高了工作效率。这种技术在龙芯Ⅱ号CPU的SRAM设计中得到了应用;芯片采用的是中芯国际0.18μm CM O S工艺。流片验证表明,该技术对于大容量的SRAM设计是较为准确而且有效的。 相似文献
6.
大型往复式压缩机功率大、占地面积大,管道振动问题也更为突出。笔者结合实践经验,对大型往复式压缩机的配管设计进行探讨,说明了平面布置与管道防振设计的密切关系,并介绍了管道防振设计的方法和步骤,以及相对简单的复杂管系气柱固有频率的转移矩阵计算方法。 相似文献
7.
介绍了当前国际上流行的用半导体可饱和吸收镜来对固体激光器、光纤激光器和半导体激光器进行被动锁模的方法,阐述了半导体可饱和吸收镜用来作为被动锁模吸收体的原理,并介绍了如何利用金属有机气相淀积(MOCVD)技术生长各种波长激光器所需要的半导体可饱和吸收镜. 相似文献
8.
9.
微波中继的应用非常广泛 ,目前在二维、三维施工中跨越障碍物时 ,一般都使用微波中继站来传输命令和数据。文章就微波中继及I/OIMAGESYSTEM“蛇形排列”先进功能的实际应用进行了详细的阐述 ,同时提出了使用微波中继站应注意的问题。 相似文献
10.