全文获取类型
收费全文 | 21195篇 |
免费 | 1963篇 |
国内免费 | 951篇 |
专业分类
电工技术 | 3202篇 |
技术理论 | 1篇 |
综合类 | 1435篇 |
化学工业 | 1913篇 |
金属工艺 | 871篇 |
机械仪表 | 2327篇 |
建筑科学 | 1050篇 |
矿业工程 | 1245篇 |
能源动力 | 581篇 |
轻工业 | 934篇 |
水利工程 | 373篇 |
石油天然气 | 1109篇 |
武器工业 | 503篇 |
无线电 | 3471篇 |
一般工业技术 | 1682篇 |
冶金工业 | 797篇 |
原子能技术 | 264篇 |
自动化技术 | 2351篇 |
出版年
2024年 | 43篇 |
2023年 | 233篇 |
2022年 | 431篇 |
2021年 | 574篇 |
2020年 | 646篇 |
2019年 | 437篇 |
2018年 | 376篇 |
2017年 | 604篇 |
2016年 | 740篇 |
2015年 | 821篇 |
2014年 | 1527篇 |
2013年 | 1293篇 |
2012年 | 1747篇 |
2011年 | 1674篇 |
2010年 | 1235篇 |
2009年 | 1258篇 |
2008年 | 999篇 |
2007年 | 1377篇 |
2006年 | 1237篇 |
2005年 | 1161篇 |
2004年 | 934篇 |
2003年 | 916篇 |
2002年 | 719篇 |
2001年 | 614篇 |
2000年 | 511篇 |
1999年 | 407篇 |
1998年 | 315篇 |
1997年 | 238篇 |
1996年 | 224篇 |
1995年 | 176篇 |
1994年 | 145篇 |
1993年 | 116篇 |
1992年 | 101篇 |
1991年 | 70篇 |
1990年 | 48篇 |
1989年 | 45篇 |
1988年 | 43篇 |
1987年 | 11篇 |
1986年 | 13篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1962年 | 2篇 |
1959年 | 2篇 |
1957年 | 1篇 |
1955年 | 2篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Optimal power flow with generation reallocation is a suitable method for better utilization of the existing system. In recent years, Flexible AC Transmission System (FACTS) devices, have led to the development of controllers that provide controllability and flexibility for power transmission. Out of the FACTS devices unified power flow controller (UPFC) is a versatile device, capable of controlling the power system parameters like voltage magnitude, phase angle and line impedance individually or simultaneously. The main aim of this paper is to minimize real power losses in a power system using BAT search algorithm without and with the presence of UPFC. Minimization of real power losses is done by considering the power generated by generator buses, voltage magnitudes at generator buses and reactive power injection from reactive power compensators. The proposed BAT algorithm based Optimal Power Flow (OPF) has been tested on a 5 bus test system and modified IEEE 30 bus system without and with UPFC. The results of the system with and without UPFC are compared in terms of active power losses in the transmission line using BAT algorithm. The obtained results are also compared with Genetic algorithm (GA). 相似文献
43.
结合烧结球团工程中环冷工艺存在的不足,着眼于实际应用需求,阐述了烧结球团环冷机温度检测及控制装置的设计思路、设备选型、系统功能设计,并针对设计过程中技术难点和技术要点进行针对性的探讨。 相似文献
44.
Jie-Long He An-Te Chen Jyong-Huei Lee Shih-Kang Fan 《International journal of molecular sciences》2015,16(9):22319-22332
The basic structural and functional unit of a living organism is a single cell. To understand the variability and to improve the biomedical requirement of a single cell, its analysis has become a key technique in biological and biomedical research. With a physical boundary of microchannels and microstructures, single cells are efficiently captured and analyzed, whereas electric forces sort and position single cells. Various microfluidic techniques have been exploited to manipulate single cells through hydrodynamic and electric forces. Digital microfluidics (DMF), the manipulation of individual droplets holding minute reagents and cells of interest by electric forces, has received more attention recently. Because of ease of fabrication, compactness and prospective automation, DMF has become a powerful approach for biological application. We review recent developments of various microfluidic chips for analysis of a single cell and for efficient genetic screening. In addition, perspectives to develop analysis of single cells based on DMF and emerging functionality with high throughput are discussed. 相似文献
45.
This study proposes a 3D CAD system available on smart devices, which are now a part of everyday life and which are widely applied in various domains, such as education and robot industry. If an engineer has a new idea while traveling or on the move, or in the case of collaboration between more than two engineers, this 3D CAD system allows modeling to be performed in a rapid and simple manner on a smart device. This 3D CAD system uses the common multi-touch gestures associated with smart devices to keep the modeling operations simple and easy for users. However, it is difficult to input the precise geometric information to generate 3D CAD models by such gestures. It is also impractical to provide a full set of modeling operations on a smart device due to hardware limitations. For this reason, the system excludes several complicated modeling operations. This work provides a scheme to regenerate a parametric 3D model on a PC-based CAD system via a macro-parametrics approach by transferring the 3D model created on a smart device in an editable form to a PC-based CAD system. If fine editing is needed, the user can perform additional work on a PC after reconstruction. Through the developed system, it is possible to produce a 3D editable model swiftly and simply in the smart device environment, allowing for reduced design time while also facilitating collaboration. This paper discusses the first-ever system design of a 3D CAD system on a smart device, the selection of the modeling operations, the assignment of gestures to these operations, and use of operation modes. This is followed by an introduction of the implementation methods, and finally a demonstration of case studies using a prototype system with examples. 相似文献
46.
Yong Pan Chen Zhu Wen Bin Zeng Pei Fu Chi Chen Bao Ming Xu Zhong Feng Gao 《Chembiochem : a European journal of chemical biology》2021,22(24):3431-3436
Rapid and sensitive point-of-care testing (POCT) is an extremely critical mission in practical applications, especially for rigorous military medicine, home health care, and in the third world. Here, we report a visual POCT method for adenosine triphosphate (ATP) detection based on Taylor rising in the corner of quadratic geometries between two rod surfaces. We discuss the principle of Taylor rising, demonstrating that it is significantly influenced by contact angle, surface tension, and density of the sample, which are controlled by ATP-dependent rolling circle amplification (RCA). In the presence of ATP, RCA reaction effectively suppresses Taylor-rising behavior, due to the increased contact angle, density, and decreased surface tension. Without addition of ATP, untriggered RCA reaction is favorable for Taylor rising, resulting in a significant height. With this proposed method, visual sensitive detection of ATP without the aid of other instruments is realized with only a 5 μL droplet, which has good selectivity and a low detection limit (17 nM). Importantly, this visual method provides a promising POCT tool for user-friendly molecular diagnostics. 相似文献
47.
Xiaojun Gao Tao Cui Zongyan Zhou Yingbo Yu Yang Xu Dongxing Zhang Wei Song 《Advanced Powder Technology》2021,32(5):1438-1449
This paper presents a numerical study on the motions of seed particles in a novel high-speed seed metering device based on the discrete element method. The effects of key parameters, including inlet velocity of particles, feeding rates and the angle of seed cleaning element, are investigated by a series of controlled numerical experiments. The results show that in the seed filling area of the device, a better match of particle velocity and the tangential linear velocity of the seeding plate can improve the seed filling performance. The number of particles remaining in the metering device is an important factor that affects the device performance. A large number of particles in the device results in more multiple seeding, and a small number causes more leakage seeding. Under the conditions of the seeding plate rotational speed at 194.5 rpm (corresponding to the high ground speed of 14 km/h), feeding rate at ~14 seeds/s can ensure that around 24 seed particles are maintained in the device which generates minimum leakage and multiple seeding. The studies of the effect of the seed cleaning element angle show that an appropriate angle (e.g., 30°) can effectively enhance the clearing ability, increase the uniform stability of particles backflow, and improve the seeding performance. 相似文献
48.
《International Journal of Hydrogen Energy》2021,46(77):38416-38424
Marigold flower (MG; Tagetes erecta) derived Graphene quantum dots (GQDs) have been successfully reported for the fabrication of supercapacitor electrodes in charge storage devices. The GQDs have been synthesized through a hydrothermal route using biomass viz. Waste material (MG) without adding any hazardous chemicals. The successful formation of GQDs as elaborated has been confirmed by various analytical characterization techniques. The as-synthesized GQDs have been electrodeposited on the Ni foil (working electrode) with the help of PVDF (binder) and subsequently, cyclic voltammetry (CV) has been conducted to access specific capacitance, energy density, and other parameters. Moreover, the galvanometric charge/discharge (GCD) technique has been employed due to its accuracy and reliability. Maximum areal specific capacitance has been found as 1.6008 F/cm2 with the current density of 2.0 A/g even after loading a little amount of material on the electrode. The high magnitude of columbic efficiency (160.08), energy density (17.78 Wh/kg), and specific capacitance of 200 F/g at current density 2.0 A/g within a voltage range of −0.55 V to +0.25 V in 2 M KOH electrolyte solution indicate a good electrocapacitive performance of the as-synthesized material. Moreover, the as-synthesized GQDs have shown excellent capacitive retention after 1000th cycles which clearly embarks its sustainable electrocapacitive nature and henceforth offers outstanding potential for the applications in energy storage devices like supercapacitors. 相似文献
49.
身份基加密(IBE)需要提供一种有效的成员撤销机制,然而,现有可撤销成员的IBE方案存在密钥更新和加密运算量过大的问题,可能使执行该操作的设备成为系统的瓶颈。将完全子树方法和在线离线技术相结合,通过修改指数逆类型IBE的密钥生成和加密算法,提出了一种高效可撤销的身份基在线离线加密方案。方案利用完全子树方法生成更新钥,使得撤销用户无法获得更新钥,进而失去解密能力;利用在线离线技术,将大部分加密运算在离线阶段进行预处理,使得在线阶段仅执行少量简单计算即可生成密文。与相关知名方案相比,该方案不仅提高密钥生成中心的密钥更新的效率,而且极大减少了轻量级设备的在线加密工作量,适合于轻量级设备保护用户隐私信息。 相似文献
50.
In view of the shortcomings of silicon micro acceleration sensor based on piezoresistive effect and capacitance principle,
such as temperature drift, low resolution and poor anti-interference ability, a fuze acceleration sensor based on dual SAW devices is
proposed. The sensor adopts a dual saw device structure, one is coated with a sensitive film for measurement, the other is an uncoat-
ed reference channel for compensation of environmental temperature, pressure, humidity and other factors. The experimental results
show that the maximum linear error is only 1.6%, the sensitivity is 54.3Hz/g, and the maximum hysteresis error is less than 1%.
Compared with piezoresistive accelerometer and capacitive accelerometer, the linear error of the accelerometer is small, the sensitivi-
ty is high, and it has strong anti-interference ability. 相似文献