全文获取类型
| 收费全文 | 858篇 |
| 免费 | 20篇 |
专业分类
| 电工技术 | 12篇 |
| 综合类 | 1篇 |
| 化学工业 | 234篇 |
| 金属工艺 | 16篇 |
| 机械仪表 | 18篇 |
| 建筑科学 | 14篇 |
| 能源动力 | 16篇 |
| 轻工业 | 79篇 |
| 水利工程 | 4篇 |
| 石油天然气 | 14篇 |
| 无线电 | 98篇 |
| 一般工业技术 | 148篇 |
| 冶金工业 | 97篇 |
| 自动化技术 | 127篇 |
出版年
| 2024年 | 18篇 |
| 2023年 | 10篇 |
| 2022年 | 13篇 |
| 2021年 | 22篇 |
| 2020年 | 23篇 |
| 2019年 | 36篇 |
| 2018年 | 18篇 |
| 2017年 | 22篇 |
| 2016年 | 19篇 |
| 2015年 | 21篇 |
| 2014年 | 30篇 |
| 2013年 | 28篇 |
| 2012年 | 32篇 |
| 2011年 | 48篇 |
| 2010年 | 33篇 |
| 2009年 | 22篇 |
| 2008年 | 47篇 |
| 2007年 | 47篇 |
| 2006年 | 39篇 |
| 2005年 | 24篇 |
| 2004年 | 20篇 |
| 2003年 | 23篇 |
| 2002年 | 18篇 |
| 2001年 | 10篇 |
| 2000年 | 4篇 |
| 1999年 | 16篇 |
| 1998年 | 20篇 |
| 1997年 | 26篇 |
| 1996年 | 15篇 |
| 1995年 | 9篇 |
| 1994年 | 14篇 |
| 1993年 | 15篇 |
| 1992年 | 15篇 |
| 1991年 | 9篇 |
| 1990年 | 4篇 |
| 1989年 | 7篇 |
| 1988年 | 7篇 |
| 1987年 | 8篇 |
| 1986年 | 5篇 |
| 1985年 | 6篇 |
| 1984年 | 6篇 |
| 1983年 | 8篇 |
| 1982年 | 6篇 |
| 1980年 | 3篇 |
| 1979年 | 7篇 |
| 1978年 | 3篇 |
| 1977年 | 5篇 |
| 1975年 | 4篇 |
| 1974年 | 3篇 |
| 1971年 | 3篇 |
排序方式： 共有878条查询结果，搜索用时 15 毫秒
731.
Eli Ruckenstein 《Chemical engineering science》1982,37(10):1505-1511
This paper emphasizes the generality of a simple algebraic procedure suggested in 1962 by the author to predict the rate of heat or mass transfer in complex situations. It consists in replacing the terms in the convective diffusion equation by expressions involving scaling quantities multiplied by constants. Thus the convective-diffusion equation is replaced by an algebraic equation for the mass transfer coefficient containing a number of constants. The constants are determined from the solutions available for some simpler limiting cases. To illustrate the procedure a variety of examples are given which include: penetration theory for diffusion with chemical reaction, laminar flow along a plate accompanied by a chemical reaction, diffusion with chemical reaction in a turbulent liquid, mass transfer from a drop to a continuous phase, unsteady heat transfer to a liquid in steady laminar flow along a plate and free convection superimposed on forced convection. Numerous other complex situations have been or can be treated by interpolation between some simpler limiting cases. 相似文献
732.
Image enhancement has been shown to improve the perceived quality of images and videos for people with visual impairments. The MPEG coding scheme makes spatial filtering, likely to help those with such impairments, possible at the decoding stage. We implemented a real-time platform for testing and improving contrast enhancement algorithms for MPEG video, with controls appropriate for the target population. The necessary additional processing runs efficiently on a general-purpose PC and can be integrated easily into existing MPEG-2 decoders. The system has enabled us to substantially improve the previous filtering algorithm; reducing artifacts exhibited in the previous implementation and should facilitate individual user-selection of enhancement parameters in evaluation studies. 相似文献
733.
Gorelick L Blank M Shechtman E Irani M Basri R 《IEEE transactions on pattern analysis and machine intelligence》2007,29(12):2247-2253
Human action in video sequences can be seen as silhouettes of a moving torso and protruding limbs undergoing articulated motion. We regard human actions as three-dimensional shapes induced by the silhouettes in the space-time volume. We adopt a recent approach for analyzing 2D shapes and generalize it to deal with volumetric space-time action shapes. Our method utilizes properties of the solution to the Poisson equation to extract space-time features such as local space-time saliency, action dynamics, shape structure and orientation. We show that these features are useful for action recognition, detection and clustering. The method is fast, does not require video alignment and is applicable in (but not limited to) many scenarios where the background is known. Moreover, we demonstrate the robustness of our method to partial occlusions, non-rigid deformations, significant changes in scale and viewpoint, high irregularities in the performance of an action, and low quality video. 相似文献
734.
Eli Dresner 《人工智能实验与理论杂志》2013,25(1):113-123
In the first section of his celebrated 1936 paper A. Turing says of the machines he defines that at each stage of their operation they can ‘effectively remember’ some of the symbols they have scanned before. In this paper I explicate the motivation and content of this remark of Turing's, and argue that it reveals what could be labeled as a connectionist conception of the human mind. 相似文献
735.
Direct separation of the enantiomers of the two diastereomers, menthone and isomenthone, was performed using an octakis-(3-O-butyryl-2,6-di-O-pentyl)-α-cyclodextrin phase. Enantiomerically pure (—)-menthone and (+)-isomenthone were detected in many oils of Mentha, Micromeria fruticosa (L.) Druce and Calamintha incána (Sm.) Heldr. High enantiomeric purities of (+)-menthone and (—)-isomenthone were detected in commercial and freshly distilled geranium oils. 相似文献
736.
Uzi Ravid Eli Putievsky Irena Katzir Efraim Lewinsohn 《Flavour and Fragrance Journal》1997,12(4):293-296
The amount and the enantiomeric composition of linalol were determined in the essential oils of seven chemotypes of Ocimum basilicum L., in the oils of O. sanctum L., O. gratissimum L. and O. canum Sims. of Thai origin, and in commercial basil oils. The linalol isolated from cultivars of O. basilicum L., of various origins, and from commercial basil oils consisted of (R)(−)-linalol and was proved to be optically pure in most cases. In essential oils of O. sanctum L. and O. canum Sims., (S)(+)-linalol was the main enantiomer. Thus, the enantiomeric differentiation of linalol may be helpful in interspecific taxonomy in the genus Ocimum. © 1997 John Wiley & Sons, Ltd. 相似文献
737.
The enantiomeric differentiation of camphor isolated from natural essential oils and samples from commercial sources was determined using a fused-silica Lipodex E capillary column. Enantiomerically pure (S)(−)-camphor was detected in Chrysanthemum parthenium (L.) Bernh. oil. The (S)(−)-enantiomer, with high enantiomeric purity was detected in two types of Salvia offtcinalis L., and (R)(+)-camphor with high enantiomeric purity was detected in two other types of S. officinalis and in S. glutinosa L. 相似文献
738.
Oz Elnir Uzi Ravid Eli Putievsky Nativ Dudai Gideon Ladizinsky 《Flavour and Fragrance Journal》1991,6(2):153-155
The chemical composition of two essential oil types of Salvia sclarea L. during early and late flowering stages was analysed. A new chemotype with relatively high citral, geranyl acetate and geraniol content was observed in two small populations growing in northern Israel. Comparison of the new chemotype with a Russian type showed a great difference in composition and organoleptic character between the two oils. The highest amount of mono- and sesquiterpene hydrocarbons was detected in the Israeli type, at the early flowering stage. The relative quantity of most components of hybrid oils was intermediate between those of the parent plants. 相似文献
739.
Camil Fuchs Eli Cohen 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1985,180(5):384-388
Summary In many cases no fixed standards are available and a sample from a target population is used to provide the necessary quality-control norms. Furthermore, many products posses several correlated attributes that are relevant to the authenticity question. This article addresses some issues related to statistical tests used in such cases, focussing in particular on a procedure that has been lately proposed for differentiating between pure and adulterated fruit juice.The quality control of fruit juice is usually performed by comparing the values of several characteristics in the tested sample against some prespecified standards. In many cases those standards are based on the values found in a sample of a presumably pure juice, which is used as a reference sample or a base sample.Several detection methods were recently proposed that use universal base samples and are supposed to be valid when applied to juices from different sources or different varieties. We compare the results yielded by the use of various base samples and show that the application of such a method to Israeli citrus juice leads to too many rejections of pure juices. We suggest that the main drawbacks of the method is the use of improper base sample that is not specific to the sample being tested.
Über die statistischen Merkmale eines stufenweisen Vorgehens zum Testen der Reinheit von Fruchtsaft
Zusammenfassung In vielen Fällen gibt es keine festen Standards und eine Probe aus einem Bestand wird angewandt, um die notwendige Qualitätsnorm zu beschaffen. Weiterhin besitzen viele Produkte mehrere korrelierende Eigenschaften, welche für die aufgeworfene Frage von Bedeutung wird. Dieser Beitrag stellt sich Fragen, die mit den in solchen Fällen üblichen statistischen Tests angewandt werden und die sich zuspitzen auf ein Vorgehen, das zur Differenzierung von reinen und verfälschten Fruchtsäften vorgeschlagen worden ist.Die Qualitätskontrolle von Fruchtsaft wird gewöhnlich durchgeführt durch Vergleichen mehrerer charakteristischer Werte in der Probe gegen einige typische Standards. In vielen Fällen gehen derartige Standards auf eine Probe mit aller Voraussicht auf reinem Fruchtsaft zurück, der als Referenzprobe oder als Basisprobe verwendet wird.Mehrere Nachweismethoden wurden kürzlich vorgeschlagen, welche universell als Basisproben gebraucht werden und die als gültig angenommen worden sind bei Fruchtsaft aus verschiedenen Quellen oder bei verschiedenen Varietäten. Wir vergleichen die Ergebnisse durch den Gebrauch verschiedener Basisproben und zeigen, daß die Anwendung einer solchen Methode auf israelische Citrussäfte zu allzu vielen Ablehnungen reiner Säfte führt. Wir vermuten, daß der hauptsächliche Nachteil der Methode der Gebrauch von unreinen Basisproben ist, die nicht typisch für die zu testende Proben sind.相似文献
740.
Eli Cohen 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1982,175(4):258-261
Summary Like many natural products, citrus juice is affected by many factors, such as climatic, seasonal, agrotechnical etc. The seasonal effects cause several problems in quality control. Almost all statistical techniques for quality control of citrus juice suffer from the same problem, namely they are applicable only to samples obtained under similar conditions to those initially taken, and thus avoiding the seasonal variability.
This work was supported by the State of Israel, Ministry of Industry and Trade, Food Division. The paper presents the opinions of the author and not necessarily that of the Ministry 相似文献
Jahreszeitliche Schwankungen von Citrussaft-Inhaltsstoffen und ihr Einfluß auf die Qualitätskontrolle von Citrussäften
Zusammenfassung Wie viele Naturprodukte wird Citrussaft durch verschiedene Faktoren wie Klima, Jahreszeit, gartenbauliche Methoden beeinflußt. Die jahreszeitlichen Einflüsse verursachen ernste Probleme bei der Qualitätskontrolle des Citrussaftes. Fast alle statistischen Techniken zur Qualitätskontrolle von Citrussaft stehen vor dem gleichen Problem, nämlich daß sie sich nur für Proben eignen, die unter gleichen Bedingungen wie das ursprüngliche Muster entnommen wurden und so jahreszeitliche Schwankungen ausgeschlossen werden.
This work was supported by the State of Israel, Ministry of Industry and Trade, Food Division. The paper presents the opinions of the author and not necessarily that of the Ministry 相似文献