全文获取类型
收费全文 | 266348篇 |
免费 | 24094篇 |
国内免费 | 12400篇 |
专业分类
电工技术 | 19520篇 |
技术理论 | 34篇 |
综合类 | 25141篇 |
化学工业 | 30517篇 |
金属工艺 | 10571篇 |
机械仪表 | 12374篇 |
建筑科学 | 32767篇 |
矿业工程 | 13501篇 |
能源动力 | 13924篇 |
轻工业 | 20638篇 |
水利工程 | 15004篇 |
石油天然气 | 26077篇 |
武器工业 | 3392篇 |
无线电 | 15850篇 |
一般工业技术 | 19003篇 |
冶金工业 | 12319篇 |
原子能技术 | 1879篇 |
自动化技术 | 30331篇 |
出版年
2024年 | 913篇 |
2023年 | 3872篇 |
2022年 | 6960篇 |
2021年 | 9478篇 |
2020年 | 8920篇 |
2019年 | 7048篇 |
2018年 | 6357篇 |
2017年 | 7857篇 |
2016年 | 9460篇 |
2015年 | 10073篇 |
2014年 | 17938篇 |
2013年 | 15845篇 |
2012年 | 19123篇 |
2011年 | 21322篇 |
2010年 | 15471篇 |
2009年 | 15576篇 |
2008年 | 14202篇 |
2007年 | 17283篇 |
2006年 | 15994篇 |
2005年 | 13841篇 |
2004年 | 11718篇 |
2003年 | 10224篇 |
2002年 | 8332篇 |
2001年 | 6828篇 |
2000年 | 5766篇 |
1999年 | 4547篇 |
1998年 | 3279篇 |
1997年 | 2859篇 |
1996年 | 2324篇 |
1995年 | 1955篇 |
1994年 | 1717篇 |
1993年 | 1170篇 |
1992年 | 965篇 |
1991年 | 680篇 |
1990年 | 571篇 |
1989年 | 529篇 |
1988年 | 304篇 |
1987年 | 234篇 |
1986年 | 195篇 |
1985年 | 234篇 |
1984年 | 160篇 |
1983年 | 137篇 |
1982年 | 80篇 |
1981年 | 95篇 |
1980年 | 99篇 |
1979年 | 45篇 |
1978年 | 25篇 |
1977年 | 29篇 |
1975年 | 25篇 |
1959年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
81.
82.
Controllability and observability of multi-agent systems with heterogeneous and switching topologies
ABSTRACTThis paper focuses on controllability and observability of multi-agent systems with heterogeneous and switching topologies, where the first- and the second-order information interaction topologies are different and switching. First, based on the controllable state set, a controllability criterion is obtained in terms of the controllability matrix corresponding to the switching sequence. Next, by virtue of the subspace sequence, two necessary and sufficient algebraic conditions are established for controllability in terms of the system matrices corresponding to all the possible topologies. Furthermore, controllability is considered from the graphic perspective. It is proved that the system is controllable if the union graph of all the possible topologies is controllable. With respect to observability, two sufficient and necessary conditions are derived by taking advantage of the system matrices and the corresponding invariant subspace, respectively. Finally, some simulation examples are worked out to illustrate the theoretical results. 相似文献
83.
ABSTRACTIn this paper, we review some algebraic control system. Precisely, linear and bilinear systems on Euclidean spaces and invariant and linear systems on Lie groups. The fourth classes of systems have a common issue: to any class, there exists an associated subgroup. From this object, we survey the controllability property. Especially, from those coming from our contribution to the theory. 相似文献
84.
为测试倾斜摄影测量技术路线,并通过实际项目的应用,解决传统古建筑建模过程中存在的时间成本高、难以还原复杂场景等问题。按照倾斜摄影技术的技术路线,进行朱氏宗祠建筑测绘试验,并通过基于altizure软件建立三维模型来展现倾斜摄影测量技术流程。验证无人机倾斜摄影应用于古建筑三维建模的可行性和可操作性。 相似文献
85.
川西彭州地区三叠系雷口坡组雷四上亚段潮坪相薄储层识别难度极大。围绕如何从复合地震强反射中区分并识别上、下两套储层面临的地球物理难题,采用先“分”后“合”的研究思路,基于实际地层结构及不同储层叠加样式建立正演模型,利用全波场波动方程正演模拟技术,剖析了不同主频条件下薄储层的地震响应特征,通过波形差异化分析,从复合地震响应中“剥离”出了两套储层所引起的地震响应特征及变化规律,明确了两套储层在不同频带下的地震识别标志和识别方法,为该区强反射界面干扰下两套薄互层储层辨识机理分析及精准预测奠定了基础。基于不同频带下薄储层辨识机理的分析结果,定性预测了薄储层平面展布,提出了深层潮坪相薄储层识别和预测难题的解决方案,为该区地震资料品质评价、面向薄储层的地震采集技术设计、地震资料处理及薄储层预测提供了依据和指导。 相似文献
86.
The Vehicle Routing Problem with Simultaneous Pickup and Delivery (VRPSPD) is an extension to the classical Vehicle Routing Problem (VRP), where customers may both receive and send goods simultaneously. The Vehicle Routing Problem with Mixed Pickup and Delivery (VRPMPD) differs from the VRPSPD in that the customers may have either pickup or delivery demand. However, the solution approaches proposed for the VRPSPD can be directly applied to the VRPMPD. In this study, an adaptive local search solution approach is developed for both the VRPSPD and the VRPMPD, which hybridizes a Simulated Annealing inspired algorithm with Variable Neighborhood Descent. The algorithm uses an adaptive threshold function that makes the algorithm self-tuning. The proposed approach is tested on well-known VRPSPD and VRPMPD benchmark instances derived from the literature. The computational results indicate that the proposed algorithm is effective in solving the problems in reasonable computation time. 相似文献
87.
Baofeng Hou Hong He Ruixiu Jia Meilong Fu Yanbin Cao Shaoqun He Liwen Luo Youqing Huang 《应用聚合物科学杂志》2019,136(10):47161
The synthesis and performance of a novel temperature-tolerant foamed resin for enhanced oil recovery were investigated using various methods, including infrared, NMR, scanning electron microscopy (SEM), and displacement experiments. Polycondensation of furfuryl alcohol prepolymers was confirmed by the infrared and NMR results. The poor temperature tolerance of furfuryl alcohol prepolymers after gelation at high temperatures is mainly due to the fracture of furan rings. The addition of ester additives is an effective method of increasing the temperature tolerance of the prepared foamed resins and can effectively reduce the weight-loss rate of the polycondensation products. The SEM results show that the skeleton structure of the foamed resin remains intact after high-temperature treatment. Thus, the novel plugging agent system has excellent thermal stability and still has a high strength (>0.8 MPa) after high-temperature aging treatment for 40 days, giving the prepared foamed resin a good plugging performance (plugging rate > 91%) at 250 °C. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47161. 相似文献
88.
89.
An antibacterial peptide (AMP), i.e., nisin, was covalently bound to gelatin through a protein–protein coupling. Various reaction conditions were tested to study and optimize parameters of grafting e.g., orientation and density of AMP, which could impact the final antibacterial activity of the modified biopolymer. Modification was investigated by Fourier transform infrared (FT‐IR) spectroscopy and zeta potential. The antibacterial activity of the nisin‐enriched gelatin was evaluated against two staphylococci bacterial strains, i.e., Staphylococus epidermidis and Staphylococcus aureus. A higher activity was found for gelatin modified at pH = 7.4 revealing an influence of the nisin orientation on the protein antibacterial property. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41825. 相似文献
90.
《Intermetallics》2015
An equiatomic CoCrFeNiMn high-entropy alloy was synthesized by mechanical alloying (MA) and spark plasma sintering (SPS). During MA, a solid solution with refined microstructure of 10 nm which consists of a FCC phase and a BCC phase was formed. After SPS consolidation, only one FCC phase can be detected in the HEA bulks. The as-sintered bulks exhibit high compressive strength of 1987 MPa. An interesting magnetic transition associated with the structure coarsening and phase transformation was observed during SPS process. 相似文献