全文获取类型
收费全文 | 12072篇 |
免费 | 926篇 |
国内免费 | 542篇 |
专业分类
电工技术 | 714篇 |
技术理论 | 1篇 |
综合类 | 736篇 |
化学工业 | 1999篇 |
金属工艺 | 584篇 |
机械仪表 | 799篇 |
建筑科学 | 817篇 |
矿业工程 | 467篇 |
能源动力 | 318篇 |
轻工业 | 727篇 |
水利工程 | 204篇 |
石油天然气 | 907篇 |
武器工业 | 93篇 |
无线电 | 1328篇 |
一般工业技术 | 1469篇 |
冶金工业 | 643篇 |
原子能技术 | 128篇 |
自动化技术 | 1606篇 |
出版年
2024年 | 65篇 |
2023年 | 231篇 |
2022年 | 375篇 |
2021年 | 538篇 |
2020年 | 423篇 |
2019年 | 382篇 |
2018年 | 381篇 |
2017年 | 392篇 |
2016年 | 356篇 |
2015年 | 479篇 |
2014年 | 592篇 |
2013年 | 671篇 |
2012年 | 820篇 |
2011年 | 791篇 |
2010年 | 711篇 |
2009年 | 699篇 |
2008年 | 635篇 |
2007年 | 635篇 |
2006年 | 670篇 |
2005年 | 524篇 |
2004年 | 371篇 |
2003年 | 311篇 |
2002年 | 307篇 |
2001年 | 266篇 |
2000年 | 274篇 |
1999年 | 303篇 |
1998年 | 243篇 |
1997年 | 216篇 |
1996年 | 193篇 |
1995年 | 162篇 |
1994年 | 136篇 |
1993年 | 86篇 |
1992年 | 75篇 |
1991年 | 57篇 |
1990年 | 52篇 |
1989年 | 34篇 |
1988年 | 22篇 |
1987年 | 19篇 |
1986年 | 20篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
基于自适应蚁群优化的Ad Hoc网络路由算法 总被引:1,自引:1,他引:0
针对蚁群优化固有的搜索时间长、易陷入局部最优解的缺点,提出一种改进的基于蚁群优化的AdHoc网络路由算法.通过增加自适应因子提高路由搜索能力,充分考虑节点间的时延来改进信息的更新机制,同时对路由表做出修改,提高路由算法性能,增强算法的适应能力.经过与已有路由算法DSR和AODV的仿真比较,结果表明该算法在成功传输率和平均端到端延迟上表现了较好的性能. 相似文献
22.
超高速水下航行器在水下航行时,表面大部分被超空泡所包覆,其运动特性发生显著变化,使得其工况变得更为复杂、控制难度加大;通过分析它的运动特点,建立了系统模型方程,并提出把空化器作为控制面,通过操纵其舵角改变量来控制航行器航向;最后运用PI极限舵控制算法进行仿真分析,结果表明此控制方法简单易实现,产生的偏差小,同时还提高了系统的响应速度,较好地满足了系统要求,分析结论可为超高速水下航行器控制系统设计提供参考。 相似文献
23.
数码相机定位是计算机图形学中的一个重要课题,在图像处理等方面有着广泛的应用,对数码相机进行合理建模分析,并利用双目视觉原理对图像进行标定,最后例证了此方法的有效性和精确性。 相似文献
24.
Dongsheng Xie Yue Zhang Xiyue Yuan Youle Li Fei Huang Yong Cao Chunhui Duan 《Advanced functional materials》2023,33(11):2212601
Semitransparent organic solar cells (ST-OSCs) have attracted increasing attention due to their promising prospect in building-integrated photovoltaics. Generally, efficient ST-OSCs with good average visible transmittance (AVT) can be realized by developing active layer materials with light absorption far from the visible light range. Herein, the development of ultrawide bandgap polymer donors with near-ultraviolet absorption, paired with near-infrared acceptors, is proposed to achieve high-performance ST-OSCs. The key points for the design of ultrawide bandgap polymers include constructing donor–donor type conjugated skeleton, suppressing the quinoidal resonance effect, and minimizing the twist of conjugated skeleton via noncovalent conformational locks. As a proof of concept, a polymer named PBOF with an optical bandgap of 2.20 eV is synthesized, which exhibited largely reduced overlap with the human eye photopic response spectrum and afforded a power conversion efficiency (PCE) of 16.40% in opaque device. As a result, ST-OSCs with a PCE over 10% and an AVT over 30% are achieved without optical modulation. Moreover, colorful ST-OSCs with visual aesthetics can be achieved by tuning the donor/acceptor weight ratio in active layer benefiting from the ultrawide bandgap nature of PBOF. This study demonstrates the great potential of ultrawide bandgap polymers for efficient colorful ST-OSCs. 相似文献
25.
Ruiqi Li Lian Chen Qin Ji Qing Liang Ying Zhu Wei Fu Tianyou Chen Hongwei Duan Wenshan He Zushun Xu Xiaofang Dai Jinghua Ren 《Advanced functional materials》2023,33(37):2213292
Radiotherapy is identified as a crucial treatment for patients with glioblastoma, but recurrence is inevitable. The efficacy of radiotherapy is severely hampered partially due to the tumor evolution. Growing evidence suggests that proneural glioma stem cells can acquire mesenchymal features coupled with increased radioresistance. Thus, a better understanding of mechanisms underlying tumor subclonal evolution may develop new strategies. Herein, data highlighting a positive correlation between the accumulation of macrophage in the glioblastoma microenvironment after irradiation and mesenchymal transdifferentiation in glioblastoma are presented. Mechanistically, elevated production of inflammatory cytokines released by macrophages promotes mesenchymal transition in an NF-κB-dependent manner. Hence, rationally designed macrophage membrane-coated porous mesoporous silica nanoparticles (MMNs) in which therapeutic anti-NF-κB peptides are loaded for enhancing radiotherapy of glioblastoma are constructed. The combination of MMNs and fractionated irradiation results in the blockage of tumor evolution and therapy resistance in glioblastoma-bearing mice. Intriguingly, the macrophage invasion across the blood-brain barrier is inhibited competitively by MMNs, suggesting that these nanoparticles can fundamentally halt the evolution of radioresistant clones. Taken together, the biomimetic MMNs represent a promising strategy that prevents mesenchymal transition and improves therapeutic response to irradiation as well as overall survival in patients with glioblastoma. 相似文献
26.
27.
28.
Chun-Xia Dou Zhi-Sheng Duan Xing-Bei Jia Pei-Feng Niu 《International Journal of Control, Automation and Systems》2011,9(3):478-488
This study introduces delay independent decentralized guaranteed cost control design method based on two controller structures
for nonlinear uncertain interconnected large scale systems with time delays. First, a set of equivalent Takagi-Sugeno (T-S)
fuzzy models are extended to represent the systems. Then a decentralized state-feedback guaranteed cost performance controller
is proposed for the fuzzy systems. Based on delay independent Lyapunov functional approach, some sufficient conditions for
the existence of the controller can be cast into the feasible problem of LMIs irrespective of the sizes of the time delays
so that the system can be asymptotically stabilized for all considered uncertainties whose sizes are not larger than their
bounds. Finally, the minimizing approach is proposed to search the suboptimal upper bound value of guaranteed cost function.
Moreover, the corresponding conditions are extended into the generalized dynamic output-feedback close-loop system. Finally,
the better control performances of the proposed methods are shown by the simulation examples. 相似文献
29.
This paper studies the problem of stabilizing a linear system with delayed and saturating feedback. It is known that the eigenstructure assignment‐based low‐gain feedback law (globally) stabilizes a linear system in the presence of arbitrarily large delay in its input, and semi‐globally stabilizes it when the input is also subject to saturation, as long as all its open‐loop poles are located in the closed left‐half plane. Based on a recently developed parametric Lyapunov equation‐based low‐gain feedback design method, this paper presents alternative, but simpler and more elegant, feedback laws that solve these problems. The advantages of this new approach include its simplicity, the capability of giving explicit conditions to guarantee the stability of the closed‐loop system, and the ease in scheduling the low‐gain parameter on line to achieve global stabilization in the presence of actuator saturation. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
30.
Yi-Yan Liu Yong-Feng JuChen-Dong Duan Xue-Feng Zhao 《Engineering Applications of Artificial Intelligence》2011,24(1):87-92
A structure damage diagnosis method combining the wavelet packet decomposition, multi-sensor feature fusion theory and neural network pattern classification was presented. Firstly, vibration signals gathered from sensors were decomposed using orthogonal wavelet. Secondly, the relative energy of decomposed frequency band was calculated. Thirdly, the input feature vectors of neural network classifier were built by fusing wavelet packet relative energy distribution of these sensors. Finally, with the trained classifier, damage diagnosis and assessment was realized. The result indicates that, a much more precise and reliable diagnosis information is obtained and the diagnosis accuracy is improved as well. 相似文献