全文获取类型
收费全文 | 148459篇 |
免费 | 13176篇 |
国内免费 | 7630篇 |
专业分类
电工技术 | 10429篇 |
技术理论 | 12篇 |
综合类 | 12892篇 |
化学工业 | 22660篇 |
金属工艺 | 8715篇 |
机械仪表 | 9574篇 |
建筑科学 | 11748篇 |
矿业工程 | 4185篇 |
能源动力 | 3980篇 |
轻工业 | 14522篇 |
水利工程 | 3064篇 |
石油天然气 | 7499篇 |
武器工业 | 1454篇 |
无线电 | 15391篇 |
一般工业技术 | 14978篇 |
冶金工业 | 6177篇 |
原子能技术 | 1571篇 |
自动化技术 | 20414篇 |
出版年
2024年 | 557篇 |
2023年 | 2053篇 |
2022年 | 4319篇 |
2021年 | 5634篇 |
2020年 | 4322篇 |
2019年 | 3416篇 |
2018年 | 3733篇 |
2017年 | 4411篇 |
2016年 | 3934篇 |
2015年 | 5908篇 |
2014年 | 7668篇 |
2013年 | 8980篇 |
2012年 | 10604篇 |
2011年 | 12411篇 |
2010年 | 10764篇 |
2009年 | 10205篇 |
2008年 | 10081篇 |
2007年 | 9543篇 |
2006年 | 9186篇 |
2005年 | 7432篇 |
2004年 | 5900篇 |
2003年 | 4760篇 |
2002年 | 4752篇 |
2001年 | 4006篇 |
2000年 | 3093篇 |
1999年 | 2798篇 |
1998年 | 1909篇 |
1997年 | 1477篇 |
1996年 | 1257篇 |
1995年 | 939篇 |
1994年 | 788篇 |
1993年 | 560篇 |
1992年 | 444篇 |
1991年 | 352篇 |
1990年 | 227篇 |
1989年 | 216篇 |
1988年 | 139篇 |
1987年 | 102篇 |
1986年 | 80篇 |
1985年 | 50篇 |
1984年 | 34篇 |
1983年 | 35篇 |
1982年 | 31篇 |
1981年 | 35篇 |
1980年 | 48篇 |
1979年 | 14篇 |
1976年 | 6篇 |
1972年 | 7篇 |
1971年 | 7篇 |
1959年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
与传统比例-积分-微分(PID)控制方法相比,滑模控制(SMC)方法可以比较容易地将不确定性纳入控制器设计中,从而增强系统的鲁棒性。探索了SMC技术在运载器主动段姿态控制中的工程应用,首先通过分析基于趋近律的SMC系统,提出了降低不连续切换项系数的需求,然后研究了基于干扰上界的SMC方法。三通道小偏差仿真结果验证了两种方法的控制效果,表明第2种控制器的鲁棒性更好,稳态误差小,同时发动机喷管摆角需求较小。 相似文献
33.
34.
Weikang Dong Ruishi Qi Tiansheng Liu Yi Li Ning Li Ze Hua Zirui Gao Shuyuan Zhang Kaihui Liu Jiandong Guo Peng Gao 《Advanced materials (Deerfield Beach, Fla.)》2020,32(46):2002014
Hyperbolic phonon polaritons (HPhPs) in orthorhombic-phase molybdenum trioxide (α-MoO3) show in-plane hyperbolicity, great wavelength compression, and ultralong lifetime, therefore holding great potential in nanophotonic applications. However, its polaritonic response in the far-infrared (FIR) range remains unexplored due to challenges in experimental characterization. Here, monochromated electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) is used to probe HPhPs in α-MoO3 in both mid-infrared (MIR) and FIR frequencies and correlate their behaviors with microstructures and orientations. It is found that low structural symmetry leads to various phonon modes and multiple Reststrahlen bands (RBs) over a broad spectral range (over 70 meV) and in different directions (55–63 meV and 119–125 meV along the b-axis, 68–106 meV along the c-axis, and 101–121 meV along the a-axis). These HPhPs can be selectively excited by controlling the direction of swift electrons. These findings provide new opportunities in nanophotonic and optoelectronic applications, such as directed light propagation, hyperlenses, and heat transfer. 相似文献
35.
Ionomics is a novel multidisciplinary field that uses advanced techniques to investigate the composition and distribution of all minerals and trace elements in a living organism and their variations under diverse physiological and pathological conditions. It involves both high-throughput elemental profiling technologies and bioinformatic methods, providing opportunities to study the molecular mechanism underlying the metabolism, homeostasis, and cross-talk of these elements. While much effort has been made in exploring the ionomic traits relating to plant physiology and nutrition, the use of ionomics in the research of serious diseases is still in progress. In recent years, a number of ionomic studies have been carried out for a variety of complex diseases, which offer theoretical and practical insights into the etiology, early diagnosis, prognosis, and therapy of them. This review aims to give an overview of recent applications of ionomics in the study of complex diseases and discuss the latest advances and future trends in this area. Overall, disease ionomics may provide substantial information for systematic understanding of the properties of the elements and the dynamic network of elements involved in the onset and development of diseases. 相似文献
36.
37.
38.
目前网络上的服装图像数量增长迅猛,对于大量服装图像实现智能分类的需求日益增加。将基于区域的全卷积网络(Region-Based Fully Convolutional Networks,R-FCN)引入到服装图像识别中,针对服装图像分类中网络训练时间长、形变服装图像识别率低的问题,提出一种新颖的改进框架HSR-FCN。新框架将R-FCN中的区域建议网络和HyperNet网络相融合,改变图片特征学习方式,使得HSR-FCN可以在更短的训练时间内达到更高的准确率。在模型中引入了空间转换网络,对输入服装图像和特征图进行了空间变换及对齐,加强了对多角度服装和形变服装的特征学习。实验结果表明,改进后的HSR-FCN模型有效地加强了对形变服装图像的学习,且在训练时间更短的情况下,比原来的网络模型R-FCN平均准确率提高了大约3个百分点,达到96.69%。 相似文献
39.
40.
Lei He Yan Xuan Feng Zhang Xue Wang Huaqing Pan Junfeng Ren Meina Chen 《International Journal of Hydrogen Energy》2021,46(1):1096-1105
Bulk and surface properties of proton stability and transportation in Y and Nd co-doped BaCeO3 (BCYN), especially the effect of Nd segregation, were investigated by first-principles calculations. Since the structure of doped BaCeO3 at the operating temperature of proton-conducting has been unclear for a long time, we have summarized the latest experimental results and calculated the structure of the asymmetric BCYN for the first time. The results show that compared with Y, Nd doping promotes oxygen vacancy formation, however reduces proton stability. Our calculation can also provide a possible explanation for the formation of space charge layer at the grain boundary of doped BaCeO3 in experiment. Unlike the stable Y in BCYN, Nd is calculated to be easily segregated, which can facilitate both proton hydration and proton transportation near the surface. Moreover, Nd segregation at the grain boundary is predicted to be beneficial for proton transportation between grains. 相似文献