全文获取类型
收费全文 | 138866篇 |
免费 | 13833篇 |
国内免费 | 7284篇 |
专业分类
电工技术 | 9737篇 |
技术理论 | 6篇 |
综合类 | 10200篇 |
化学工业 | 20629篇 |
金属工艺 | 8712篇 |
机械仪表 | 9571篇 |
建筑科学 | 10422篇 |
矿业工程 | 4315篇 |
能源动力 | 4453篇 |
轻工业 | 9598篇 |
水利工程 | 3094篇 |
石油天然气 | 6693篇 |
武器工业 | 1549篇 |
无线电 | 17265篇 |
一般工业技术 | 16432篇 |
冶金工业 | 6130篇 |
原子能技术 | 2057篇 |
自动化技术 | 19120篇 |
出版年
2025年 | 29篇 |
2024年 | 1875篇 |
2023年 | 2271篇 |
2022年 | 3752篇 |
2021年 | 5502篇 |
2020年 | 4375篇 |
2019年 | 3708篇 |
2018年 | 3681篇 |
2017年 | 4318篇 |
2016年 | 4195篇 |
2015年 | 5590篇 |
2014年 | 7149篇 |
2013年 | 8404篇 |
2012年 | 9630篇 |
2011年 | 10757篇 |
2010年 | 9801篇 |
2009年 | 9471篇 |
2008年 | 9381篇 |
2007年 | 9110篇 |
2006年 | 8559篇 |
2005年 | 6933篇 |
2004年 | 5066篇 |
2003年 | 4234篇 |
2002年 | 4223篇 |
2001年 | 3638篇 |
2000年 | 2952篇 |
1999年 | 2418篇 |
1998年 | 1740篇 |
1997年 | 1432篇 |
1996年 | 1191篇 |
1995年 | 979篇 |
1994年 | 832篇 |
1993年 | 641篇 |
1992年 | 443篇 |
1991年 | 346篇 |
1990年 | 261篇 |
1989年 | 231篇 |
1988年 | 172篇 |
1987年 | 146篇 |
1986年 | 112篇 |
1985年 | 61篇 |
1984年 | 58篇 |
1983年 | 58篇 |
1982年 | 49篇 |
1981年 | 48篇 |
1980年 | 36篇 |
1979年 | 20篇 |
1977年 | 25篇 |
1976年 | 19篇 |
1959年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
Sludge disintegration treatment by using simultaneously ultrasonic irradiation and electrolysis was investigated experimentally. A lab-scale diaphragm cell irradiated with ultrasound at a constant oscillating frequency of 20 kHz was used as a reactor. The batch experiments were carried out under different conditions of electric outputs of the ultrasonic generator, electric current for the electrolysis and different initial SS concentrations. A simultaneous treatment in the cathodic compartment without any chemical doses considerably facilitated the sludge solubilization, compared to the sonication alone. An increase in the electric current up to 400 mA under a constant ultrasonic density decreased the specific energy by 55% within the experimental range. The specific energy consumption was also reduced when the initial SS concentration increased. In addition, before carrying out the simultaneous treatment, a brief electrolysis was effective for further reduction of the specific energy and the acceleration of soluble COD generation. 相似文献
22.
In arc welding processes, because of the complexity and nonlinearity of heat transfer phenomena, it is often difficult to design an effective control system based upon an exact mathematical model. In this paper, a self-organizing fuzzy control method is proposed to obtain a uniform weld quality by regulation of the surface temperature at a desired level. The proposed control system is designed to comprise a combined structure of the fuzzy SOC with conventional PD control for improving the system's stability. The control experiments show that the proposed controller guarantees a uniform weld quality for various welding conditions. 相似文献
23.
化学镀Ni—P镀层的X射线衍射研究 总被引:2,自引:0,他引:2
根据X射线衍射分析结果,对化学镀高P(含P>11wt%或19at%)Ni-P镀层加热时效时,镀层成分和加热温度对结构转变的影响作了研究,结果表明,高P共晶、过共晶(含P>11wt%或19at%)合金的结构转变有如下特征:(1)相同加热时效条件下,Ni-P合金的结构转变与成分有密切关系:(2)对同一成分的过共晶合金,Ni-P合金的结构转变与时效温度密切相关;(3)过共晶合金在290~360℃温度范围内时效处理,出现Ni_xP_y介稳相,X射线衍射分析认为Ni_xP_y为Ni_(12)P_5。 相似文献
24.
Plasmapropertiesoflaser-ablatedSttargetinairWangXiang-Tai(王象泰);ManBao-Yuan(满宝元);WangGong-Tang(王公堂);FanXi-Jun(樊锡君);WangJun(王军)... 相似文献
25.
Tetsuhiko Kobayashi Nolven Guilhaume Jun Miki Naoyuki Kitamura Masatake Haruta 《Catalysis Today》1996,32(1-4):171-175
In an attempt to develop new catalysts for the formation of formaldehyde from methane, the promotion effect of Fe on SiO2 and that of Sn on WO3 have been studied. The formation of formaldehyde on silica can be appreciably enhanced by the impregnation of Fe, as far as iron loadings are kept below 0.1 atom.% (Fe/Si × 100). In the case of Sn---W---Ox catalysts, both the addition of Sn to WO3, and that of W on SnO2 were effective to the selective formaldehyde formation. Absorption spectra (UV-Vis) and ESR measurements revealed that tetrahedrally coordinated Fe3+ in the silica network plays an important role in the formation of formaldehyde. A thin surface layer consisting of W and Sn oxides can account for the selective formaldehyde formation on the Sn---W---Ox catalysts. 相似文献
26.
27.
Xiaolin Hu Jun Wang 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》2007,37(3):528-539
This paper presents a recurrent neural-network model for solving a special class of general variational inequalities (GVIs), which includes classical VIs as special cases. It is proved that the proposed neural network (NN) for solving this class of GVIs can be globally convergent, globally asymptotically stable, and globally exponentially stable under different conditions. The proposed NN can be viewed as a modified version of the general projection NN existing in the literature. Several numerical examples are provided to demonstrate the effectiveness and performance of the proposed NN. 相似文献
28.
In this work, we designed, fabricated and tested a disposable, flow-through amperometric sensor for free chlorine determination in water. The sensor is based on the principle of an electrochemical cell. The substrate, as well as the top microfluidic layer, is made up of a polymer material. The advantages include; (a) disposability from low cost; (b) stable operation range from three-electrode design; (c) fluidic interconnections that provide on line testing capabilities; and (d) transparent substrate which provides for future integration of on-chip optics. The sensor showed a good response and linearity in the chlorine concentration ranging from 0.3 to 1.6 ppm, which applies to common chlorination process for drinking water purification. 相似文献
29.
30.