全文获取类型
收费全文 | 2765篇 |
免费 | 92篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 37篇 |
化学工业 | 572篇 |
金属工艺 | 92篇 |
机械仪表 | 54篇 |
建筑科学 | 140篇 |
矿业工程 | 25篇 |
能源动力 | 64篇 |
轻工业 | 246篇 |
水利工程 | 18篇 |
石油天然气 | 13篇 |
无线电 | 168篇 |
一般工业技术 | 455篇 |
冶金工业 | 591篇 |
原子能技术 | 41篇 |
自动化技术 | 347篇 |
出版年
2022年 | 16篇 |
2021年 | 30篇 |
2020年 | 26篇 |
2019年 | 33篇 |
2018年 | 38篇 |
2017年 | 45篇 |
2016年 | 45篇 |
2015年 | 50篇 |
2014年 | 64篇 |
2013年 | 192篇 |
2012年 | 93篇 |
2011年 | 121篇 |
2010年 | 114篇 |
2009年 | 88篇 |
2008年 | 117篇 |
2007年 | 118篇 |
2006年 | 113篇 |
2005年 | 83篇 |
2004年 | 96篇 |
2003年 | 92篇 |
2002年 | 64篇 |
2001年 | 50篇 |
2000年 | 51篇 |
1999年 | 52篇 |
1998年 | 76篇 |
1997年 | 59篇 |
1996年 | 55篇 |
1995年 | 35篇 |
1994年 | 39篇 |
1993年 | 47篇 |
1992年 | 41篇 |
1991年 | 25篇 |
1990年 | 25篇 |
1989年 | 27篇 |
1988年 | 30篇 |
1987年 | 26篇 |
1986年 | 29篇 |
1985年 | 36篇 |
1984年 | 38篇 |
1983年 | 25篇 |
1982年 | 21篇 |
1981年 | 36篇 |
1980年 | 21篇 |
1979年 | 23篇 |
1978年 | 26篇 |
1977年 | 31篇 |
1976年 | 29篇 |
1975年 | 22篇 |
1974年 | 25篇 |
1972年 | 19篇 |
排序方式: 共有2863条查询结果,搜索用时 218 毫秒
71.
Carl Heinz Brieskorn und Günter Blosczyk 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1981,172(3):201-205
Zusammenfassung Die Cuticula von Traubenschalen enthält neben Oleanolsäure noch 3-Oxo-olean-12-en28-säure, 3-Hydroxi-olean-12-en-28-aldehyd, 3,29-Dihydroxi-olean-12-en-28-säure sowie zwei bisher unbekannte Triterpensäuren. Ihre Strukturen werden durch spektroskopische Daten als 16-Hydroxi-3-oxo-olean-12-en-28-säure und 16-Hydroxi-3-oxo-oleana-1,12-dien-28-säure belegt.
New triterpenic acids from the peel of grapes
Summary The grape-cuticle contains beside oleanolic acid, 3-oxo-olean-12-en-28-oic acid, 3-hydroxy-olean-12-en-28-aldehyde, 3,29-dihydroxy-olean-12-en-28-oic acid, and two yet hitherto unknown triterpenic acids. Their structures have been elucidated by spectroscopic methods to be l6-hydroxy-3-oxo-olean-12-en-28-oic acid and 16-hydroxy-3-oxo-oleana-1,12-dien-28-oic acid.相似文献
72.
Carl Miller Helen Austin Larry Posorske Jesus Gonzlez 《Journal of the American Oil Chemists' Society》1988,65(6):927-931
The lipase-catalyzed synthesis of ester bonds has been well-documented lately and is of much current commercial interest.
Immobilization of a fungal lipase on a unique macroporous support allows not only the ability to operate in non-aqueous media
but to catalyze ester synthesis in quantitative yields, employing attractive commercial conditions. Catalyst dose and process
configurations will be illustrated. The capability of the catalyst to operate efficiently in reverse under a variety of unnatural,
hostile, solvent-containing environments will be discussed. The range of substrates for this immobilized lipase, Lipzome,
has been investigated. The enzyme will catalyze ester synthesis with saturated, unsaturated and a variety of branched carboxylic
acids. The alcohol specificity for this enzyme also is equally broad. A wide variety of straight-chain, branched and polar
alcohols can be substrates. In addition, some examples of alcohol specificity for kinetic isomer resolution will be cited.
Presented at the symposium “The Biology, Biotechnology and Technology of Lipases” at the 78th annual meeting of the American
Oil Chemists’ Society held May 17–21, 1987, in New Orleans, Louisiana. 相似文献
73.
Jongchul Song Walter R. Fagerlund Carl T. Haas Clyde B. Tatum Jorge A. Vanegas 《Canadian Metallurgical Quarterly》2005,131(6):723-733
Prefabrication, preassembly, modularization, and off-site fabrication, collectively termed as prework have become more viable with recent advances in design and information technologies. These construction methods offer a substantial opportunity to improve project performance when circumstances merit. Successful implementation of these methods on a particular project requires systematic analysis and early decision making based on specific factors of the project. This paper identifies those factors influencing decisions on the use of prework, and current industry practices for evaluating the applicability of prework on industrial projects. It then presents a decision framework to assist industry practitioners with evaluating the applicability of prework on their project, and describes a computerized tool to aid project teams in the decision-making process. The developed framework and tool are useful and effective in the decision-making process, and easy to use, as validated by practitioners in the industry. 相似文献
74.
Schwebel David C.; Brezausek Carl M.; Ramey Craig T.; Ramey Sharon L. 《Canadian Metallurgical Quarterly》2005,24(5):501
The number of immigrants in the United States is at an all time high, yet psychologists have largely ignored the domain of immigrant health. This article considers 1 aspect of immigrant health, risk for pediatric injury. A sample of over 5,000 5-year-old children from impoverished families was studied; approximately 13% had immigrant mothers. Children of immigrants had a significantly lower rate of injury in the prior year. This was particularly true of non-White children of immigrants. Three possible mediators for this finding--assistance with parenting, parenting style, and health care accessibility--were considered, but none explained the difference. The need for further research on the topic and implications of results for injury prevention are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
75.
A Flexible Framework for Fault Tolerance in the Grid 总被引:2,自引:0,他引:2
This paper presents a failure detection service (FDS) and a flexible failure handling framework (Grid-WFS) as a fault tolerance mechanism on the Grid. The FDS enables the detection of both task crashes and user-defined exceptions. A major challenge in providing such a generic failure detection service on the Grid is to detect those failures without requiring any modification to both the Grid protocol and the local policy of each Grid node. This paper describes how to overcome the challenge by using a notification mechanism which is based on the interpretation of notification messages being delivered from the underlying Grid resources. The Grid-WFS built on top of FDS allows users to achieve failure recovery in a variety of ways depending on the requirements and constraints of their applications. Central to the framework is flexibility in handling failures. This paper describes how to achieve the flexibility by the use of workflow structure as a high-level recovery policy specification, which enables support for multiple failure recovery techniques, the separation of failure handling strategies from the application code, and user-defined exception handlings. Finally, this paper presents an experimental evaluation of the Grid-WFS using a simulation, demonstrating the value of supporting multiple failure recovery techniques in Grid applications to achieve high performance in the presence of failures. 相似文献
76.
Carl L. Gardner Wolfgang Nonner Robert S. Eisenberg 《Journal of Computational Electronics》2004,3(1):25-31
The drift-diffusion (Poisson-Nernst-Planck) model is applied to ionic channels in biological membranes plus surrounding solution baths. Simulations of the K channel in KCl solutions using the TRBDF2 method are presented which show significant boundary layers at the ends of the channel. The computed current-voltage curve for the K channel shows excellent agreement with experimental measurements. 相似文献
77.
Solution of a Well-Field Design Problem with Implicit Filtering 总被引:1,自引:0,他引:1
Fowler Kathleen R. Kelley Carl T. Miller Cass T. Kees Christopher E. Darwin Robert W. Reese Jill P. Farthing Matthew W. Reed Mark S. C. 《Optimization and Engineering》2004,5(2):207-234
Problems involving the management of groundwater resources occur routinely, and management decisions based upon optimization approaches offer the potential to save substantial amounts of money. However, this class of application is notoriously difficult to solve due to non-convex objective functions with multiple local minima and both nonlinear models and nonlinear constraints. We solve a subset of community test problems from this application field using MODFLOW, a standard groundwater flow model, and IFFCO, an implicit filtering algorithm that was designed to solve problems similar to those of focus in this work. While sampling methods have received only scant attention in the groundwater optimization literature, we show encouraging results that suggest they are deserving of more widespread consideration for this class of problems. In keeping with our objectives for the community problems, we have packaged the approaches used in this work to facilitate additional work on these problems by others and the application of implicit filtering to other problems in this field. We provide the data for our formulation and solution on the web. 相似文献
78.
Diguer Louis; Pelletier Sylvie; Hébert étienne; Desc?teaux Jean; Rousseau Jean-Pierre; Daoust Jean-Philippe 《Canadian Metallurgical Quarterly》2004,21(2):259
This study examined the hypothesis that psychotic, borderline, and neurotic personality organizations (POs) present a progressive differentiation between self and object representations and an increasing integration of their bad and good aspects. Fifty patients participated in the study. Measures included scales of self and object representations (S. J. Blatt, S. A. Bers, & C. E. Schaffer, 1993; S. J. Blatt, H. Wiseman, E. Prince-Gibson, & C. Gatt, 1991), as well as the Personality Organization Diagnostic Form (L. Diguer & L. Normandin, 1997) and estimations of psychiatric severity. Results showed that PO groups differed in terms of the integration of the object and its valence. It was also observed that although object and self representations were closely intertwined, the latter showed more discrimination between POs than the former. Psychiatric severity was shown to correlate more with object representations than self representations. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
79.
An automated quality assessment technique is proposed for rapidly detecting excessive size variations during the production of stone aggregates. The system uses a laser profiler to scan collections of aggregate particles and obtain three-dimensional data points on the particle surfaces. For computational efficiency, the resulting data are converted into digital images. Wavelet transforms are then applied to the images to extract features indicative of the material gradation. These wavelet-based features are used as inputs to an artificial neural network, which is trained to classify the aggregate sample. Taken together, these components form a neural network-based classification system that can determine whether or not an aggregate product is in compliance with a given specification. Verification tests show that this approach could potentially help to determine, in an accurate and fast (real-time) manner, when adjustments or repairs to the production equipment are needed. 相似文献
80.