全文获取类型
收费全文 | 42274篇 |
免费 | 541篇 |
国内免费 | 790篇 |
专业分类
电工技术 | 729篇 |
综合类 | 52篇 |
化学工业 | 6380篇 |
金属工艺 | 3094篇 |
机械仪表 | 1386篇 |
建筑科学 | 865篇 |
矿业工程 | 151篇 |
能源动力 | 1429篇 |
轻工业 | 2271篇 |
水利工程 | 356篇 |
石油天然气 | 1386篇 |
无线电 | 3977篇 |
一般工业技术 | 10682篇 |
冶金工业 | 7279篇 |
原子能技术 | 796篇 |
自动化技术 | 2772篇 |
出版年
2021年 | 342篇 |
2020年 | 276篇 |
2019年 | 374篇 |
2018年 | 666篇 |
2017年 | 659篇 |
2016年 | 743篇 |
2015年 | 539篇 |
2014年 | 808篇 |
2013年 | 2389篇 |
2012年 | 1407篇 |
2011年 | 1887篇 |
2010年 | 1489篇 |
2009年 | 1782篇 |
2008年 | 1627篇 |
2007年 | 1772篇 |
2006年 | 1401篇 |
2005年 | 1229篇 |
2004年 | 1179篇 |
2003年 | 1081篇 |
2002年 | 1067篇 |
2001年 | 1120篇 |
2000年 | 966篇 |
1999年 | 1002篇 |
1998年 | 2133篇 |
1997年 | 1660篇 |
1996年 | 1449篇 |
1995年 | 989篇 |
1994年 | 761篇 |
1993年 | 780篇 |
1992年 | 598篇 |
1991年 | 573篇 |
1990年 | 524篇 |
1989年 | 486篇 |
1988年 | 369篇 |
1987年 | 402篇 |
1986年 | 365篇 |
1985年 | 382篇 |
1984年 | 306篇 |
1983年 | 301篇 |
1982年 | 302篇 |
1981年 | 296篇 |
1980年 | 350篇 |
1979年 | 342篇 |
1978年 | 299篇 |
1977年 | 417篇 |
1976年 | 632篇 |
1975年 | 309篇 |
1974年 | 292篇 |
1973年 | 311篇 |
1972年 | 272篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
The development of a simplified approach for sizing and placement of tuned filters for power factor correction of nonlinear loads is outlined. This approach has been successfully applied to industrial power distribution systems ranging in size from 550 to 10000 kVA. Six case studies that illustrate different aspects of the approach are presented. In all instances, power factor was improved to meet the goal, and in many cases, harmonic distortion was significantly reduced 相似文献
92.
93.
Neurocomputing strategies in structural design — on analysing weights of feedforward neural networks
The sequel of two papers explores the applicability of selected neurocomputing strategies in the optimization of structural systems. The present paper describes the use of interconnection weights of a multilayer, feedforward neural network to extract information pertinent to a design space modelled by such a network. It is shown that aweights analysis provides a technique to assess the effect of all input quantities on a given output. Such dependencies are expressed in the form of atransition matrix, and their evaluation is reduced to the inspection of elements of a matrix row. Explicit formulae are derived for networks with one and two hidden layers and can easily be generalized to networks with an arbitrary number of hidden layers. In addition to its use as a tool to partition design spaces, the weights analysis may be employed to assist in determining the size of hidden layers and an adequate number of training patterns (input-output pairs). Several numerical examples from the field of structural analysis are provided, and the paper underscores the utility of the present technique in decomposition driven optimal design; such optimization is treated in full in the companion paper. 相似文献
94.
95.
S.H. Tantawi I.Z.Selim 《材料科学技术学报》1996,12(2):95-99
The use of a natural white juice, taken from magrabe banana stem, as concrete admixture to improve mechanical and physicrvchemical properties of concrete has been studied. The compressive strength, bulk density the free lime liberated during hydration and the combined water content were determined. The results indicate that the admixture acts as a retarder in most cases and as accelerator in some ones. Also, the admixture effect on the corrosion resistance of the reinforcing steel against surrounding aggressive media has been investigated using galvanostatic polarization technique. The addition of 0.2% admixture leads to the more inhibition of the steel 相似文献
96.
97.
This experiment was designed to use the graded dose-related amnesia produced by the benzodiazepine lorazepam (1.0, 2.0 mg/70 kg, oral) and the anticholinergic scopolamine (0.3, 0.6 mg/70 kg, subcutaneous) as a tool to explore the cognitive and neurochemical mechanisms underlying metamemory in the judgment of learning paradigm, with a placebo-controlled independent groups design in healthy volunteers (n=12/group). Results provide evidence for a pharmacological dissociation between effects on memory versus metamemory (relative accuracy of item-by-item monitoring) across a range of levels of memory performance and suggest that the drugs selectively impair those aspects of metamnemonic monitoring that require participants' awareness of their overall current state of functioning (absolute accuracy of prospective item-by-item monitoring, prospective global monitoring) but not those that rely solely on assessment of individual item characteristics (relative accuracy of item-by-item monitoring). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
98.
Endocrine disrupting chemicals (EDCs) are the focus of current environmental issues, as they can cause adverse health effects to animals and human, subsequent to endocrine function. The objective of this study was to remove a specific compound of EDCs (i.e. pentachlorophenol, C(6)OCL(5)Na, molecular weight of 288 g/mol) using low pressure reverse osmosis membrane (LPROM). A cross flow module of LPROM was used to observe the effects of operating parameters, i.e. pH, operating pressure and temperature. The design of the experiment was based on MINITAB(TM) software, and the analysis of results was conducted by factorial analysis. It was found that the rejection of pentachlorophenol was higher than 80% at a recovery rate of 60 to 70%. The rejection was subjected to increase with the increase of pH. The flux was observed to be increased with the increase of operating pressure and temperature. This study also investigated the interaction effects between operating parameters involved. 相似文献
99.
100.
W. Tang H.Z. Shi G. Xu B.S. Ong Z.D. Popovic J.C. Deng J. Zhao G.H. Rao 《Advanced materials (Deerfield Beach, Fla.)》2005,17(19):2307-2311