全文获取类型
收费全文 | 12872篇 |
免费 | 1144篇 |
国内免费 | 789篇 |
专业分类
电工技术 | 610篇 |
综合类 | 1408篇 |
化学工业 | 2702篇 |
金属工艺 | 179篇 |
机械仪表 | 489篇 |
建筑科学 | 1095篇 |
矿业工程 | 212篇 |
能源动力 | 142篇 |
轻工业 | 1416篇 |
水利工程 | 236篇 |
石油天然气 | 272篇 |
武器工业 | 121篇 |
无线电 | 878篇 |
一般工业技术 | 789篇 |
冶金工业 | 752篇 |
原子能技术 | 69篇 |
自动化技术 | 3435篇 |
出版年
2024年 | 107篇 |
2023年 | 377篇 |
2022年 | 574篇 |
2021年 | 681篇 |
2020年 | 623篇 |
2019年 | 369篇 |
2018年 | 286篇 |
2017年 | 330篇 |
2016年 | 342篇 |
2015年 | 340篇 |
2014年 | 566篇 |
2013年 | 663篇 |
2012年 | 779篇 |
2011年 | 731篇 |
2010年 | 679篇 |
2009年 | 700篇 |
2008年 | 727篇 |
2007年 | 879篇 |
2006年 | 838篇 |
2005年 | 700篇 |
2004年 | 567篇 |
2003年 | 481篇 |
2002年 | 384篇 |
2001年 | 308篇 |
2000年 | 258篇 |
1999年 | 204篇 |
1998年 | 165篇 |
1997年 | 127篇 |
1996年 | 117篇 |
1995年 | 104篇 |
1994年 | 113篇 |
1993年 | 81篇 |
1992年 | 81篇 |
1991年 | 58篇 |
1990年 | 59篇 |
1989年 | 45篇 |
1988年 | 40篇 |
1987年 | 36篇 |
1986年 | 32篇 |
1985年 | 37篇 |
1984年 | 20篇 |
1983年 | 19篇 |
1982年 | 17篇 |
1981年 | 10篇 |
1979年 | 10篇 |
1966年 | 12篇 |
1965年 | 10篇 |
1964年 | 13篇 |
1957年 | 12篇 |
1955年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
33.
The objective of this study is to explore the possibility of capturing the reasoning process used in bidding a hand in a bridge
game by an artificial neural network. We show that a multilayer feedforward neural network can be trained to learn to make
an opening bid with a new hand. The game of bridge, like many other games used in artificial intelligence, can easily be represented
in a machine. But, unlike most games used in artificial intelligence, bridge uses subtle reasoning over and above the agreed
conventional system, to make a bid from the pattern of a given hand. Although it is difficult for a player to spell out the
precise reasoning process he uses, we find that a neural network can indeed capture it. We demonstrate the results for the
case of one-level opening bids, and discuss the need for a hierarchical architecture to deal with bids at all levels. 相似文献
34.
Pankaj Mathure Ashwin Patwardhan 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(4):413-419
In this study, the mass transfer efficiencies of a novel horizontal rotating packed (h‐RPB) bed and the conventional disc‐type rotating biological contactor (RBC) were studied at four speeds and seven submergences. Pall rings of two different sizes (25, 38 mm), superintalox saddles and a wiremesh spiral bundle were used as packings in the h‐RPB. Volumetric gas–liquid mass transfer coefficients were determined by unsteady state absorption of atmospheric oxygen in de‐aerated water. Power consumption per unit liquid volume has been found for all geometries tested. The oxygen transfer efficiency values for the h‐RPB were found to be 2–5 kg kWh?1 and for the disc RBC were found to be 1–2 kg kWh?1. The performance of the h‐RPB was also compared with other gas–liquid contactors such as surface aerators. The study proves that the h‐RPB is a energy efficient alternative to conventional contactors. Copyright © 2005 Society of Chemical Industry 相似文献
35.
Yong Ma Yong‐zhen Peng Xiao‐lian Wang Shu‐ying Wang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(10):1118-1124
The laboratory scale anaerobic–anoxic–aerobic (A2O) process fed with synthetic brewage wastewater was designed to investigate the effects of changing feed C/P ratio on the performance of biological nutrient removal (BNR) processes. In the experiment, the influent chemical oxygen demand (COD) concentration was kept at approximately 300 mg L?1 while the total phosphorus concentration was varied to obtain the desired C/P ratio. Results showed that when the C/P ratio was lower than 32, phosphorus removal efficiency increased as C/P ratio increased linearly, while when the C/P ratio was higher than 32, the P removal efficiency was maintained at 90–98%, and effluent P concentration was lower than 0.5 mg L?1. However, regardless of the C/P ratio, excellent COD removal (90% or higher) and good total nitrogen removal (75–84%) were maintained throughout the experiments. It was also found that very good linear correlation was obtained between COD uptake per unit P released in the anaerobic zone and C/P ratio. In addition, the P content in the wasted activated sludge increased with the decrease in the C/P ratio. Based on the results, it was recommended that the wastewater C/P ratio and its effects be incorporated into BNR design and operational procedures, appropriate C/P ratios were used to achieve the effluent treatment goals. Copyright © 2005 Society of Chemical Industry 相似文献
36.
DO浓度对SUFR系统同步硝化反硝化的影响 总被引:1,自引:1,他引:0
采用螺旋升流式反应器(SUFR)处理生活污水,考察了好氧反应池中DO浓度对其同步硝化反硝化的影响。结果表明,在好氧反应池上部溶解氧浓度为3.0~3.5mg/L时,发生了明显的同步硝化反硝化现象,其对TN的去除量占SUFR系统对TN去除总量的16%左右;好氧反应池中的同步硝化反硝化反应只发生在池的下部,其中、上部只进行了好氧硝化反应;SUFR系统中好氧反应池上部的最佳溶解氧浓度范围为3.0~3.5mg/L,此时系统的硝化和反硝化效果最佳,好氧反应池中的脱氮效果也较好,系统对TN的去除率〉84%。 相似文献
37.
Dr Joseph A. Cannataci 《AI & Society》1989,3(3):169-183
This paper examines some of the possible legal implications of the production, marketing and use of expert systems. The relevance of a legally useful definition of expert systems, comprising systems designed for use both by laymen and professionals, is related to the distinctions inherent in the legal doctrine underlying provision of goods and provision of services. The liability of the sellers and users of, and contributors to, expert systems are examined in terms of professional malpractice as well as product liability. A recurring theme indicates that legislators may be inclined to restrict possibilities of liability suits in order to avoid disincentives to the creation of expert systems. 相似文献
38.
《钢结构工程施工质量验收规范》修订简介 总被引:1,自引:1,他引:0
简要介绍《钢结构工程施工质量验收规范》(GB 5 0 2 0 5 - 2 0 0 1)的修订原则、方法以及对原规范进行修订中新增加的内容及要求 ,并进行了详细解释 ,以便于对新规范的理解 相似文献
39.
智能型MNS低压开关柜 总被引:1,自引:0,他引:1
MNS智能低压开关柜是ABB公司的新一代产品。除具有设计灵活、结构紧凑和免维护等特点外,安全可靠性是其最突出的优点,包括抗故障电弧、可靠的绝缘分隔及接插性能、可靠的抽屉单元和温升限制。采用和智能化电动机控制中心INSUM及配电智能化控制和能量管理系统ESD2000的完美结合,开发了了基于现场总线的智能化的系统解决方案。 相似文献
40.
Over the last century, IQ scores have been steadily rising, a phenomenon dubbed the Flynn effect. Because of the Flynn effect, IQ tests are periodically renormed, making them harder. Given that eligibility for mental retardation (MR) services relies heavily on IQ scores, renormed tests could have a significant impact on MR placements. In longitudinal IQ records from 9 sites around the country, students in the borderline and mild MR range lost an average of 5.6 points when retested on a renormed test and were more likely to be classified MR compared with peers retested on the same test. The magnitude of the effect is large and affects national policies on education, social security, the death penalty, and the military. This paper reports the perceptions of professionals as they relate to IQ score fluctuations in normal, borderline, and/or MR populations. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献