全文获取类型
收费全文 | 15822篇 |
免费 | 1199篇 |
国内免费 | 667篇 |
专业分类
电工技术 | 725篇 |
技术理论 | 1篇 |
综合类 | 1116篇 |
化学工业 | 2741篇 |
金属工艺 | 818篇 |
机械仪表 | 1040篇 |
建筑科学 | 1369篇 |
矿业工程 | 466篇 |
能源动力 | 404篇 |
轻工业 | 1036篇 |
水利工程 | 310篇 |
石油天然气 | 997篇 |
武器工业 | 192篇 |
无线电 | 1741篇 |
一般工业技术 | 1792篇 |
冶金工业 | 743篇 |
原子能技术 | 199篇 |
自动化技术 | 1998篇 |
出版年
2024年 | 76篇 |
2023年 | 271篇 |
2022年 | 444篇 |
2021年 | 592篇 |
2020年 | 465篇 |
2019年 | 394篇 |
2018年 | 434篇 |
2017年 | 518篇 |
2016年 | 446篇 |
2015年 | 622篇 |
2014年 | 775篇 |
2013年 | 896篇 |
2012年 | 940篇 |
2011年 | 1066篇 |
2010年 | 872篇 |
2009年 | 872篇 |
2008年 | 788篇 |
2007年 | 785篇 |
2006年 | 870篇 |
2005年 | 747篇 |
2004年 | 482篇 |
2003年 | 468篇 |
2002年 | 465篇 |
2001年 | 448篇 |
2000年 | 424篇 |
1999年 | 453篇 |
1998年 | 412篇 |
1997年 | 289篇 |
1996年 | 281篇 |
1995年 | 249篇 |
1994年 | 200篇 |
1993年 | 127篇 |
1992年 | 118篇 |
1991年 | 86篇 |
1990年 | 60篇 |
1989年 | 53篇 |
1988年 | 44篇 |
1987年 | 34篇 |
1986年 | 25篇 |
1985年 | 18篇 |
1984年 | 12篇 |
1983年 | 13篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
粒子群优化算法的发展趋势 总被引:3,自引:1,他引:2
分析优化算法的发展历程,指出粒子群优化算法(PSO)是基于群体智能的一种算法,简单易行,可调参数少,研究广泛且发展迅速.结合图形给出算法的个体极值和整体极值的搜优运动过程.研究总结算法的研究现状及特点,认为PSO还需要完善和继续研究.提出将算法应用于复杂的约束优化、随机优化与最优控制问题是算法应用研究的方向,并指出对该算法完整的收敛性分析是算法成熟的标志. 相似文献
83.
基于TMS320F2812的液晶显示模块接口设计 总被引:3,自引:0,他引:3
为适应工业应用现场以及智能化仪器仪表前端显示的需要,阐述了TMS320F2812DSP和QH2001液晶显示模块的原理及特性,提出了一种基于高速DSP处理器控制低速液晶显示模块的接口设计方案,并对该方案的硬件接口电路和软件驱动程序进行了设计,同时给出了软、硬件实现的相应电路图、程序流程图以及具体程序段;实验调试表明,设计方案结构简单、成本低、抗干扰能力强、显示性能稳定可靠,达到设计要求,能够有效解决高速DSP对低速LCD的驱动及显示问题,并取得了良好的显示效果,对其它便携式系统显示终端的设计也具有一定参考价值。 相似文献
84.
地下管线被视为城市的生命线。分析了地下管线定位仪的基本原理,并在此基础上详细介绍了基于ATmega 128单片机的数字化地下管线定位仪的硬件实现和软件实现,重点分析了基于磁保持继电器的分时供电电源电路。ATmega 128单片机实现了地下管线定位仪的数字化,使得定位仪能快速、准确地对地下管线进行水平定位和垂直定深。 相似文献
85.
Jae Kyeong Jeong Jong Han Jeong Hui Won Yang Tae Kyung Ahn Minkyu Kim Kwang Suk Kim Bon Seog Gu Hyun‐Joong Chung Jin‐Seong Park Yeon‐Gon Mo Hye Dong Kim Ho Kyoon Chung 《Journal of the Society for Information Display》2009,17(2):95-100
Abstract— A full‐color 12.1‐in.WXGA active‐matrix organic‐light‐emitting‐diode (AMOLED) display was, for the first time, demonstrated using indium‐gallium‐zinc oxide (IGZO) thin‐film transistors (TFTs) as an active‐matrix backplane. It was found that the fabricated AMOLED display did not suffer from the well‐known pixel non‐uniformity in luminance, even though the simple structure consisting of two transistors and one capacitor was adopted as the unit pixel circuit, which was attributed to the amorphous nature of IGZO semiconductors. The n‐channel a‐IGZO TFTs exhibited a field‐effect mobility of 17 cm2/V‐sec, threshold voltage of 1.1 V, on/off ratio >109, and subthreshold gate swing of 0.28 V/dec. The AMOLED display with a‐IGZO TFT array is promising for large‐sized applications such as notebook PCs and HDTVs because the a‐IGZO semiconductor can be deposited on large glass substrates (larger than Gen 7) using the conventional sputtering system. 相似文献
86.
Xiaohong Guan Wei Wang Xiangliang Zhang 《Journal of Network and Computer Applications》2009,32(1):31-44
In this paper, we present an efficient fast anomaly intrusion detection model incorporating a large amount of data from various data sources. A novel method based on non-negative matrix factorization (NMF) is presented to profile program and user behaviors of a computer system. A large amount of high-dimensional data is collected in our experiments and divided into smaller data blocks by a specific scheme. The system call data is divided into blocks by processes, while command data is divided into consecutive blocks with a fixed length. The frequencies of individual elements in each block of data are computed and placed column by column as data vectors to construct a matrix representation. NMF is employed to reduce the high-dimensional data vectors and anomaly detection can be realized as a very simple classifier in low dimensions. Experimental results show that the model presented in this paper is promising in terms of detection accuracy, computation efficiency and implementation for fast intrusion detection. 相似文献
87.
L. Guan I.U. Awan I. Phillips A. Grigg W. Dargie 《Simulation Modelling Practice and Theory》2009,17(3):558-568
The provision of guaranteed QoS for various Internet traffic types has become a challenging problem for researchers. New Internet applications, mostly multimedia-based, require differentiated treatments under certain QoS constraints. Due to a rapid increase in these new services, Internet routers are facing serious traffic congestion problems. This paper presents an approximate analytical performance model in a discrete-time queue, based on closed form expressions using queue threshold, to control the congestion caused by the bursty Internet traffic. The methodology of maximum entropy (ME) has been used to characterize closed form expressions for the state and blocking probabilities. A discrete-time GGeo/GGeo/1/{N1, N2} censored queue with finite capacity, N2, external compound Bernoulli traffic process and generalised geometric transmission times under a first come first serve (FCFS) rule and arrival first (AF) buffer management policy has been used for the solution process. To satisfy the low delay along with high throughput, a threshold, N1, has been incorporated to slow the arrival process from mean arrival rate λ1 to λ2 once the instantaneous queue length has been reached, otherwise the source operates normally. This creates an implicit feedback from the queue to the arrival process. The system can be potentially used as a model for congestion control based on the Random Early Detection (RED) mechanism. Typical numerical experiments have been included to show the credibility of ME solution against simulation for various performance measures and to demonstrate the performance evaluation of the proposed analytical model. 相似文献
88.
89.
Ying-Xia Du Qiao Yang Wang-Ting Lu Qing-Yu Guan Fei-Fei Cao Geng Zhang 《Advanced functional materials》2023,33(27):2300895
Single metal atom isolated in nitrogen-doped carbon materials (M N C) are effective electrocatalysts for oxygen reduction reaction (ORR), which produces H2O2 or H2O via 2-electron or 4-electron process. However, most of M N C catalysts can only present high selectivity for one product, and the selectivity is usually regulated by complicated structure design. Herein, a carbon black-supported Co N C catalyst (CB@Co N C) is synthesized. Tunable 2-electron/4-electron behavior is realized on CB@Co-N-C by utilizing its H2O2 yield dependence on electrolyte pH and catalyst loading. In acidic media with low catalyst loading, CB@Co N C presents excellent mass activity and high selectivity for H2O2 production. In flow cell with gas diffusion electrode, a H2O2 production rate of 5.04 mol h−1 g−1 is achieved by CB@Co N C on electrolyte circulation mode, and a long-term H2O2 production of 200 h is demonstrated on electrolyte non-circulation mode. Meanwhile, CB@Co N C exhibits a dominant 4-electron ORR pathway with high activity and durability in pH neutral media with high catalyst loading. The microbial fuel cell using CB@Co N C as the cathode catalyst shows a peak power density close to that of benchmark Pt/C catalyst. 相似文献
90.
Tianhao Wu Xu Zhang Yinzhong Wang Nian Zhang Haifeng Li Yong Guan Dongdong Xiao Shiqi Liu Haijun Yu 《Advanced functional materials》2023,33(4):2210154
As one of the high-energy cathode materials of lithium-ion batteries (LIBs), lithium-rich-layered oxide with “single-crystal” characteristic (SC-LLO) can effectively restrain side reactions and cracks due to the reduced inner boundaries and enhanced mechanical stabilities. However, there are still high challenges for SC-LLO with diverse performance requirements, especially on their cycle stability improvement. Herein, a novel concentration gradient “single-crystal” LLO (GSC-LLO), with gradually decreasing Mn and increasing Ni contents from center to surface, is designed and prepared by combining co-precipitation and molten-salt sintering methods, yielding a capacity retention of 97.6% and an energy density retention of 95.8% within 100 cycles at 0.1 C. The enhanced performance is mostly attributed to the gradient-induced stabilized structure, free of cracks and less spinel-like structure formation after long-term cycling. Furthermore, the gradient design is also beneficial to the safety of LLOs as suggested by the improved thermal stability and reduced gas release. This study provides an effective strategy to prepare high-energy, high-stability, and high-safety LLOs for advanced LIBs. 相似文献