全文获取类型
收费全文 | 94562篇 |
免费 | 9548篇 |
国内免费 | 5055篇 |
专业分类
电工技术 | 14097篇 |
技术理论 | 19篇 |
综合类 | 7088篇 |
化学工业 | 8902篇 |
金属工艺 | 2998篇 |
机械仪表 | 4672篇 |
建筑科学 | 19214篇 |
矿业工程 | 2371篇 |
能源动力 | 12976篇 |
轻工业 | 2125篇 |
水利工程 | 2168篇 |
石油天然气 | 2221篇 |
武器工业 | 831篇 |
无线电 | 6084篇 |
一般工业技术 | 8569篇 |
冶金工业 | 3926篇 |
原子能技术 | 1294篇 |
自动化技术 | 9610篇 |
出版年
2024年 | 592篇 |
2023年 | 1951篇 |
2022年 | 3146篇 |
2021年 | 3478篇 |
2020年 | 3782篇 |
2019年 | 3247篇 |
2018年 | 2757篇 |
2017年 | 3394篇 |
2016年 | 3767篇 |
2015年 | 3821篇 |
2014年 | 6783篇 |
2013年 | 6735篇 |
2012年 | 6635篇 |
2011年 | 7457篇 |
2010年 | 5805篇 |
2009年 | 6006篇 |
2008年 | 5445篇 |
2007年 | 6028篇 |
2006年 | 4885篇 |
2005年 | 3868篇 |
2004年 | 3177篇 |
2003年 | 2693篇 |
2002年 | 2391篇 |
2001年 | 2067篇 |
2000年 | 1746篇 |
1999年 | 1371篇 |
1998年 | 1069篇 |
1997年 | 859篇 |
1996年 | 748篇 |
1995年 | 594篇 |
1994年 | 532篇 |
1993年 | 411篇 |
1992年 | 313篇 |
1991年 | 289篇 |
1990年 | 234篇 |
1989年 | 181篇 |
1988年 | 150篇 |
1987年 | 118篇 |
1986年 | 73篇 |
1985年 | 129篇 |
1984年 | 106篇 |
1983年 | 75篇 |
1982年 | 83篇 |
1981年 | 36篇 |
1980年 | 44篇 |
1979年 | 33篇 |
1978年 | 14篇 |
1977年 | 11篇 |
1959年 | 5篇 |
1951年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Although the gas metal arc welding (GMAW) process is widely used for joining metals, its planning is still a cumbersome task. The planning procedure involves many complex interrelationships among the process variables and depends heavily on empirical knowledge. Therefore, a solution method that allows a convenient way to represent the domain knowledge and evaluate the process variable relationships is needed. Further, the lack of a strong domain theory to quantify these interrelationships is a deficiency in the planning of the GMAW process. This paper presents a solution method that overcomes this deficiency and introduces a convenient knowledge representation scheme. The solution method considers the planning procedure to be a constraint satisfaction problem (CSP). The AC-4 algorithm is used to obtain arc consistency among nodes in the constraint network and the PC-4 algorithm is applied to obtain path consistency in the network. A modified version of the AC-4 algorithm is developed to reduce the search space and correspondingly reduce the computation time. An example is presented to demonstrate the capability of the method and its potential to reduce lead time. 相似文献
102.
An open‐cycle ocean thermal energy conversion (OC‐OTEC) system is one of the energy conversion methods used to generate electricity from ocean thermal energy. For the OC‐OTEC system, steam evaporated from the surface seawater due to flash evaporation drives the turbine. At that time, dissolved gas such as air is introduced into the low‐pressure system (OC‐OTEC system) as the noncondensable gas, which degrades the performance of condensation heat transfer. In this paper, a small‐scale OC‐OTEC experimental unit experimentally investigates the effect of noncondensable gas on the heat transfer performance in a condenser. The experimental results are discussed in comparison with theoretical estimation by the Sparrow–in method. It is shown that the condensation is occupied by heat and mass transfer near a condensation surface and that the condensation efficiency is affected by exhaust quantity of noncondensable gas at a relatively high concentration ratio of condensable gas. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 154(1): 29–35, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20179 相似文献
103.
Damiana Chinese Antonella Meneghetti Gioacchino Nardin Patrizia Simeoni 《国际能源研究杂志》2007,31(9):829-848
A mixed integer linear programming model combined with a more traditional design by scenarios is proposed to optimize facilities size and operation mode of a municipal energy system involving significant civil centres and a hospital. Moving from the need of a new heat and power station for the local hospital due to the construction of new pavilions, the opportunity of involving other centres in the neighbourhood in a distributed cogeneration system is analysed, increasing system complexity step by step. Smaller cogeneration units tailored to hospital needs are rewarding ventures with relatively low risks but, in a country whose traditional power generation systems heavily rely on fossil fuels and where energy policy and market conditions can make it profitable to sell surplus power, district heating systems foster the installation of larger cogenerators and lead thereby to higher profits and to better performance as for primary energy savings and greenhouse gases emission reduction. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
104.
Energy minimization and design for testability 总被引:6,自引:0,他引:6
Srimat T. Chakradhar Vishwani D. Agrawal Michael L. Bushnell 《Journal of Electronic Testing》1994,5(1):57-66
The problem of fault detection in general combinational circuits is NP-complete. The only previous result on identifying easily testable circuits is due to Fujiwara who gave a polynomial time algorithm for detecting any single stuck fault inK-bounded circuits. Such circuits may only contain logic blocks with no more thanK input lines and the blocks are so connected that there is no reconvergent fanout among them. We introduce a new class of combinational circuits called the (k, K)-circuits and present a polynomial time algorithm to detect any single or multiple stuck fault in such circuits. We represent the circuit as an undirected graphG with a vertex for each gate and an edge between a pair of vertices whenever the corresponding gates have a connection. For a (k, K)-circuit,G is a subgraph of ak-tree, which, by definition, cannot have a clique of size greater thank+1. Basically, this is a restriction on gate interconnections rather than on the function of gates comprising the circuit. The (k, K)-circuits are a generalization of Fujiwara'sK-bounded circuits. Using the bidirectional neural network model of the circuit and the energy function minimization formulation of the fault detection problem, we present a test generation algorithm for single and multiple faults in (k, K)-circuits. This polynomial time aggorithm minimizes the energy function by recursively eliminating the variables. 相似文献
105.
多缝式烧嘴点火器具有燃烧效率高,火焰长度易调,炉膛温度分布合理等优点,经工业试验证明,该点火器能满足攀钢烧结点火工艺要求,并有明显节能效果。 相似文献
106.
107.
Yasuhiro Kobayashi Toshiyuki Sawa Toshiyuki Furukawa Shigeru Kawamoto 《Electrical Engineering in Japan》2002,138(2):49-58
This paper describes a load dispatch method which minimizes power cost—[fuel cost]/[electric output]—for a power system with thermal plants and energy storage facilities. The proposed method employs fractional programming to convert a minimization problem with fractional objective function to a series of quadratic minimization problems, and semidefinite programming to solve converted problems. The method provides the optimum time‐dependent power output/input and storage level of energy storage facilities as well as time‐dependent power output of thermal plants. The method has been applied to a power system with five thermal plants, two energy storage facilities of various performances, and five load demands. The optimum load scheme of four time mesh points is obtained for the thermal plants and energy storage facilities. The fractional programming successfully converges the optimal scheme through a few iterations. The semidefinite programming deals with a variable matrix of 164 dimensions, and 185 inequality constraints. © 2001 Scripta Technica, Electr Eng Jpn, 138(2): 49–58, 2002 相似文献
108.
This paper presents an investigation into the energy absorbing behaviour of axially splitting square metal tubes. Tubes 50 mm square with a variable thickness were pushed slowly against rigid pyramid shaped dies, which had various semi-angles. By pre-cutting 5 mm long slits at the four corners, the tube splits along the corners and curls outward with a certain radius at a constant force. In this energy dissipating system, there are three components: tearing energy, plastic deformation energy and frictional energy. Theoretical analysis of the three energy components is presented. Curl radius is also studied in detail. Good agreement between experiments and theory is obtained. The results show that tubes which both split and curl may be used as efficient, long stroke energy absorbing devices. 相似文献
109.
介绍了珠海拱北口岸联检楼空调系统的设计特点,提出了按建筑类型、功能进行空调系统分区的设计方法,强调应根据建筑物的具体情况设置设备用房,以保障空调系统正常有效地运行。 相似文献
110.
Because of its high–temperature chemical stability, SiC ceramic is a promising material for high-temperature device applications such as thermoelectric energy converters. However, the electrical conductivity of SiC ceramic is too low for it to be used as a thermoelectric energy converter at the cold junction. Therefore, we propose a SiC-Si functionally gradient material (FGM) in order to improve the electrical conductivity of the SiC ceramic at the cold junction. An SiC rod was fired in a temperature gradient furnace. One end of the SiC rod was maintained at 2473 K and the other end was maintained at 1973 K for 30 min. After firing, the porous SiC edge fired at 1973 K was dipped into molten Si in order to infiltrate molten Si into the porous SiC. The microstructure of the FGM is classified into three regions: the SiC-Si composite material; the porous SiC ceramic; and the densified SiC ceramic. The electrical conductivity, the Seebeck coefficient and the thermal conductivity for each region of SiC-Si FGM was measured at 300 K; a figure of merit was calculated. The figure of merit of the SiC-Si FGM at the cold junction, at room temperature, was 108 times higher than that of a nongradient SiC ceramic. 相似文献