全文获取类型
收费全文 | 9293篇 |
免费 | 318篇 |
国内免费 | 18篇 |
专业分类
电工技术 | 102篇 |
综合类 | 9篇 |
化学工业 | 2102篇 |
金属工艺 | 256篇 |
机械仪表 | 192篇 |
建筑科学 | 340篇 |
矿业工程 | 28篇 |
能源动力 | 207篇 |
轻工业 | 786篇 |
水利工程 | 112篇 |
石油天然气 | 38篇 |
武器工业 | 2篇 |
无线电 | 667篇 |
一般工业技术 | 1750篇 |
冶金工业 | 1931篇 |
原子能技术 | 62篇 |
自动化技术 | 1045篇 |
出版年
2023年 | 64篇 |
2022年 | 115篇 |
2021年 | 185篇 |
2020年 | 145篇 |
2019年 | 138篇 |
2018年 | 188篇 |
2017年 | 173篇 |
2016年 | 190篇 |
2015年 | 141篇 |
2014年 | 233篇 |
2013年 | 506篇 |
2012年 | 405篇 |
2011年 | 509篇 |
2010年 | 330篇 |
2009年 | 359篇 |
2008年 | 431篇 |
2007年 | 425篇 |
2006年 | 341篇 |
2005年 | 313篇 |
2004年 | 283篇 |
2003年 | 246篇 |
2002年 | 262篇 |
2001年 | 118篇 |
2000年 | 128篇 |
1999年 | 131篇 |
1998年 | 161篇 |
1997年 | 146篇 |
1996年 | 156篇 |
1995年 | 140篇 |
1994年 | 140篇 |
1993年 | 157篇 |
1992年 | 118篇 |
1991年 | 107篇 |
1990年 | 131篇 |
1989年 | 106篇 |
1988年 | 82篇 |
1987年 | 129篇 |
1986年 | 97篇 |
1985年 | 127篇 |
1984年 | 124篇 |
1983年 | 131篇 |
1982年 | 104篇 |
1981年 | 93篇 |
1980年 | 77篇 |
1979年 | 74篇 |
1978年 | 92篇 |
1977年 | 71篇 |
1976年 | 74篇 |
1975年 | 79篇 |
1974年 | 82篇 |
排序方式: 共有9629条查询结果,搜索用时 15 毫秒
61.
Joseph Breheny Cian Kingston Robert Doran Joao Anes Marta Martins Samus Fanning Patrick J. Guiry 《International journal of molecular sciences》2021,22(12)
Herein, we report antibacterial and antifungal evaluation of a series of previously prepared (+)-tanikolide analogues. One analogue, (4S,6S)-4-methyltanikolide, displayed promising anti-methicillin-resistant Staphylococcus aureus activity with a MIC of 12.5 µg/mL. Based on the antimicrobial properties of the structurally related (−)-malyngolide, two further analogues (4S,6S)-4-methylmalyngolide and (4R,6S)-4-methylmalyngolide bearing a shortened n-nonyl alkyl side chain were prepared in the present study using a ZrCl4-catalysed deprotection/cyclisation as the key step in their asymmetric synthesis. When these were tested for activity against anti-methicillin-resistant Staphylococcus aureus, the MIC increased to 50 µg/mL. 相似文献
62.
Kyung-Ju Choi Joseph E. Spruiell James L. White 《Polymer Engineering and Science》1989,29(21):1524-1527
The present paper describes an analysis of the orientation developed in biaxially stretched polystyrene films in terms of the kinematics of the process and a viscoelastic constitutive equation. It was possible to achieve reasonable agreement of predicted and experimental birefringences through use of a convected Maxwell model and the Rheo-Optical Law. 相似文献
63.
The objective of this study was to identify how physiological measures relate to self-reported vehicle seating discomfort. Twelve subjects of varied anthropometric characteristics were enrolled in the study. Subjects sat in two seats over a 2-h period and were evaluated via three physiological measures (near-infrared spectroscopy, electromyography and pressure mapping) yielding six testing sessions. Subjective discomfort surveys were recorded before and after each session for nine regions of the body. Conditional classification discomfort models were developed through dichotomised physiological responses and anthropometry to predict subjective discomfort in specific body locations. Models revealed that subjects taller than 171 cm with reduced blood oxygenation in the biceps femoris or constant, low-level muscle activity in the trapezius tended to report discomfort in the lower extremities or neck, respectively. Subjects weighing less than 58 kg with reduced blood oxygenation in the biceps femoris or unevenly distributed pressure patterns tended to report discomfort in the buttocks. The sensitivities and specificities of cross-validated models ranged between 0.69 and 1.00. 相似文献
64.
We compared methods for predicting and understanding the source of confusion errors during military vehicle identification training. Participants completed training to identify main battle tanks. They also completed card-sorting and similarity-rating tasks to express their mental representation of resemblance across the set of training items. We expected participants to selectively attend to a subset of vehicle features during these tasks, and we hypothesised that we could predict identification confusion errors based on the outcomes of the card-sort and similarity-rating tasks. Based on card-sorting results, we were able to predict about 45% of observed identification confusions. Based on multidimensional scaling of the similarity-rating data, we could predict more than 80% of identification confusions. These methods also enabled us to infer the dimensions receiving significant attention from each participant. This understanding of mental representation may be crucial in creating personalised training that directs attention to features that are critical for accurate identification.
Practitioner Summary: Participants completed military vehicle identification training and testing, along with card-sorting and similarity-rating tasks. The data enabled us to predict up to 84% of identification confusion errors and to understand the mental representation underlying these errors. These methods have potential to improve training and reduce identification errors leading to fratricide. 相似文献
65.
Frédéric Destaillats Jean B. Jean-Denis Joseph Arul Robert L. Wolff Paul Angers 《Journal of the American Oil Chemists' Society》2002,79(11):1091-1094
GC analysis was performed to determine regiospecific distribution and FA composition in seed oils of the Aceraceae species,
Acer saccharum and A. saccharinum. The oil content in the seeds was low at 5.0% in A. saccharum and 5.8% in A. saccharinum, and the main FA were linoleic (30.8 and 29.4%), oleic (21.3 and 27.6%), palmitic (10.1 and 10.5%), and cis-vaccenic (9.4 and 7.9%) acids, respectively. In addition, both oils contained long-chain monoenes of the n−9 and n−7 groups,
including 11-eicosenoic, 13-docosenoic, 15-tetracosenoic, 13-eicosenoic, and 15-docosenoic acids, whereas γ-linolenic acid
accounted for 0.8% of total FA in A. saccharum, and 0.5% in A. saccharinum. Regiospecific analysis, performed using the methodology of dibutyroyl derivatives of MAG, indicated that linoleic, oleic,
and linolenic acids were mainly esterified at the internal position of TAG in both seed oils, whereas long-chain monoenes
of the n−7 group were almost exclusively esterified on the external positions. 相似文献
66.
In order for robots to effectively understand natural language commands, they must be able to acquire meaning representations that can be mapped to perceptual features in the external world. Previous approaches to learning these grounded meaning representations require detailed annotations at training time. In this paper, we present an approach to grounded language acquisition which is capable of jointly learning a policy for following natural language commands such as “Pick up the tire pallet,” as well as a mapping between specific phrases in the language and aspects of the external world; for example the mapping between the words “the tire pallet” and a specific object in the environment. Our approach assumes a parametric form for the policy that the robot uses to choose actions in response to a natural language command that factors based on the structure of the language. We use a gradient method to optimize model parameters. Our evaluation demonstrates the effectiveness of the model on a corpus of commands given to a robotic forklift by untrained users. 相似文献
67.
Joseph Akyeampong Silvanus Udoka Giandomenico Caruso Monica Bordegoni 《International Journal of Industrial Ergonomics》2014
This study evaluated newly proposed Human–Machine Interface (HMI) design concepts for improving the ergonomics of hydraulic excavators. The design concepts were based on an augmented interaction technique which involved the use of heads-up display (HUD) and coordinated control as HMI elements. Two alternative HMI designs were elaborated in order to separately evaluate the ergonomic impacts of the head-up display and the coordinated control by comparing them to the standard HMI design. The effectiveness of these three HMI designs in terms of the reduction of the operators' mental and physical workload were assessed by conducting experiments utilizing human subjects, ages 23–35 years. The National Aeronautics and Space Administration's Task Load Index (NASA TLX) method was used for collecting subjective workload scores based on a weighted average of ratings of six factors: Mental Demand, Physical Demand, Temporal Demand, Own Performance, Effort, and Frustration Level. The results showed that the type of HMI design affects different aspects of the operator's workload. Indeed, it showed how the proposed augmented interaction is an effective solution for reducing the ergonomic gaps in terms of mental workload, and to a lesser extent the physical workload, subjected by the standard HMI design. 相似文献
68.
Equilibrium exchange isotherms were determined for the exchange of Cu2+ with NaZSM-5 at varying Cu(Ac)2 concentrations in solutions of constant volume and zeolite weight. At low Cu2+ levels the solid scavenged all the copper ions. When copper could be detected in the equilibrated solutions, overexchange was observed. The extent of overexchange was higher at pH 6 than at pH 4. These results were analyzed in relation to catalytic activity.On leave from the Central Institute for Chemistry, Hungarian Academy of Sciences, H1525 Budapest, Hungary. 相似文献
69.
70.
Summary Novel oxycarbonyl isocyanate telechelic polyisobutylenes have been prepared by conversion of hydroxylterminated polyisobutylenes with N-chlorocarbonyl isocyanate. This reaction is free from side-reactions and provides highly reactive isocyanate-terminated polyisobutylene prepolymers. Conversion of these prepolymers with glycol, urea, pentaerythritol, and polyethylene glycol led to linear chain extension, crosslinking, and multiblock copolymer formation, respectively. 相似文献