全文获取类型
收费全文 | 2028篇 |
免费 | 38篇 |
国内免费 | 46篇 |
专业分类
电工技术 | 27篇 |
综合类 | 67篇 |
化学工业 | 438篇 |
金属工艺 | 184篇 |
机械仪表 | 154篇 |
建筑科学 | 133篇 |
矿业工程 | 62篇 |
能源动力 | 285篇 |
轻工业 | 32篇 |
水利工程 | 5篇 |
石油天然气 | 43篇 |
武器工业 | 7篇 |
无线电 | 105篇 |
一般工业技术 | 279篇 |
冶金工业 | 34篇 |
原子能技术 | 41篇 |
自动化技术 | 216篇 |
出版年
2024年 | 2篇 |
2023年 | 48篇 |
2022年 | 69篇 |
2021年 | 74篇 |
2020年 | 55篇 |
2019年 | 46篇 |
2018年 | 61篇 |
2017年 | 45篇 |
2016年 | 41篇 |
2015年 | 32篇 |
2014年 | 80篇 |
2013年 | 153篇 |
2012年 | 79篇 |
2011年 | 137篇 |
2010年 | 82篇 |
2009年 | 104篇 |
2008年 | 146篇 |
2007年 | 107篇 |
2006年 | 98篇 |
2005年 | 82篇 |
2004年 | 67篇 |
2003年 | 111篇 |
2002年 | 68篇 |
2001年 | 32篇 |
2000年 | 48篇 |
1999年 | 24篇 |
1998年 | 33篇 |
1997年 | 31篇 |
1996年 | 28篇 |
1995年 | 24篇 |
1994年 | 21篇 |
1993年 | 13篇 |
1992年 | 20篇 |
1991年 | 16篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1975年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有2112条查询结果,搜索用时 593 毫秒
11.
12.
Bedich ika Helena Bendov Ivan Macha
《Chemical Engineering and Processing: Process Intensification》2005,44(12):1312-1319
A procedure has been proposed for the estimation of the terminal falling velocity of non-spherical particles moving in a Carreau model fluid in the transition flow region. The procedure is based on a modification of the relationship formerly developed for the fall of spherical particles including the particle dynamic shape factor. The suitability of the proposed procedure has been confirmed by good agreement between experimental and calculated terminal falling velocity data. In the experiments, the terminal falling velocity of short cylinders and rectangular prisms in polymer solutions of different measure of shear thinning and elasticity has been measured. 相似文献
13.
Maria Chiara Dalconi Giuseppe Cruciani Alberto Alberti Paolo Ciambelli 《Catalysis Today》2005,110(3-4):345-350
High-silica zeolites exchanged with transition metal ions (TMIs) are the subject of great interest for their unusual catalytic activity and selectivity. Structural information like coordination and accessibility of TMIs in zeolites are important factors for understanding their catalytic activity. Siting of TMIs in zeolites is typically obtained by spectroscopic (EXAFS, EPR, UV–vis and IR) and computational methods, as in the case of Co-ferrierite. However, some controversy exists in the literature concerning the model for incorporation of bare Co ions in ferrierite. We show here that the results of our synchrotron X-ray powder diffraction studies on Co- and Ni-exchanged ferrierite (Si/Al = 8.5) are in a good agreement with the model of Co siting based on an indirect spectroscopic approach and help to validate this model. By direct structural evidences, a possible explanation for the larger catalytic activity of Co sites in the main channels of ferrierite can be inferred. A combination of data from in situ XRD continuous monitoring of the Co ion migration during calcination and crystal-chemical considerations allows to device a strategy for the design of optimised co-cations containing Co-ferrierite catalysts. 相似文献
14.
Mgidi Donald Dlamini 《Solar Energy Materials & Solar Cells》1996,43(4):353
In this paper results on surface photovoltage (SPV) and electron beam induced conductivity (EBIC) studies of edge-defined film-fed growth (EFG) and floating zone (FZ) silicon solar cell materials (both p-type) are presented. A systematic comparison based on minority carrier diffusion length and carrier recombination is made between: (i) samples contaminated with Ti and/or Fe, (ii) samples gettered by phosphorous diffusion, and (iii) as-received samples. Deep level transient spectroscopy (DLTS) measurements, together with the iron-boron (FeB) pairing kinetics [1] have successfully been used to detect the presence of Fe in the samples. Even though this process is effective in revealing Fe impurities in p-type FZ silicon it is evidently not suitable for Fe identification in p-type EFG silicon. Ti, like Fe, is found to be a prominent lifetime-limiting metallic impurity in both EFG and FZ silicon. Phosphorous diffusion is proven to be an effective external gettering technique for fast-diffusing impurities such as Fe, but not for Ti. 相似文献
15.
介绍了间接跃迁的半导体AlP与GaP形成的超晶格,由于零折叠效应,实现了能带由间接带隙向直接带隙的转变,从而增加了带间的光跃迁几率,并推导了该几率的表达式。 相似文献
16.
A. Andreev L. Prahov M. Gabrovska A. Eliyas V. Ivanova 《Applied catalysis. B, Environmental》1996,8(4):365-373
The catalytic activity of a wide range of transition metal oxides in oxidation of sulphide ions by air in aqueous medium was studied. Some specific features of the reaction mechanism on some of the studied oxides were considered. The transition metal oxides are promising catalysts for practical application. Some of these oxides will allow the preparation of catalysts possessing activity comparable to that of the cobalt phthalocyanine based catalysts, popular in industrial practice. 相似文献
17.
HPAM/柠檬酸铝胶态分散凝胶形成条件研究 总被引:41,自引:7,他引:34
采用一种简化的实验程序测定胶态分散凝胶(CDG)的转变压,用测得的转变压值作为评价参数,考察由HPAM、柠檬酸铝、硫脲、氯化钾组成的CDG的形成条件及相对强度。所考察的形成条件包括HPAM的来源和浓度,柠檬酸铝和氯化钾的浓度,pH值,绝大部分实验工作在40℃和pH=7.0的条件下进行,用一组实验考察了温度的影响(70℃和40℃)。 相似文献
18.
Large elevated steel silos for the storage of bulk solids generally consist of a cylindrical vessel above a conical discharge hopper supported on a cylindrical skirt. The cone–cylinder–skirt transition junction is subject to a large circumferential compressive force which is derived from the horizontal component of the meridional tension in the conical hopper, so either a ring is provided or the shell walls are locally thickened to strengthen the junction. Extensive theoretical studies have examined the buckling and collapse strengths of these junctions, leading to theoretically based design proposals. However, no previous experimental study on steel silo transition junctions has been reported due to the considerable difficulties associated with testing these thin-shell junctions at model scale. This paper presents the results of a series of tests on cone–cylinder–skirt–ring junctions in steel silos under simulated bulk solid loading. In addition to the presentation of test results including geometric imperfections and failure behavior, the determination of buckling modes and loads based on displacement measurements is examined in detail. 相似文献
19.
20.
本文在分析局域网服务器信息缓冲区、数据包接受和发送缓冲区的相互关系基础上提出一种新的局域网服务器缓冲区设计方法─—广义随机Petri网方法,并给出了局域网服务器信息缓冲区的广义随机Petri网模型。该设计方法理论完备、严谨实用,且不再局限于追求某一边界值(上限或下限),并且避免了排队理论处理多级服务的繁琐公式。最后本文用一例题说明了这种方法的应用。 相似文献